Green / Energy-saving home. New build or Reno experience?

[boknows]

A thread that was resurrected from 2011 about building a new home reminded me... My wife and I currently live in a townhome, and have plans to move into a single-family home sometime in the next 5 years (no firm date). I'd really like to have a home that is energy efficient. Home prices in our area are pretty high (DC suburbs) and I'm trying to weigh my options so that we don't overspend.

What are some of your experiences with building a green/energy-saving home or renovating an existing home to comply to such standards? I'm trying to figure out what is cost effective, and it's actually somewhat hard to find architects/builders in the area that specialize in such a thing, and even harder to find pricing examples readily. I emailed an architect of a net-zero home that was advertised in the area, and asked him if it was even possible to build such a home for our budget (500-600k total) and he said that it IS possible, but that land is a big cost in the area (all I can find in my school district is plots for $300k).

Seems like passive-solar design (facing south) and an extremely tight envelope are highly important, and that building from scratch is the best way to achieve that.

[livesoft]

I just looked at utility bills for our 3000+ sq ft McMansion in south Texas for the past year. We paid less than $1550 for electricity and gas. Our 1993 home is energy efficient, but nothing overboard. I don't recall anything special in the design or construction, except that it has insulation. Other features are 2 water heaters, 2 HVAC units, ceiling fans over the beds, and a great site situation.

The site probably has a lot to do with it: The home faces south with close trees providing lots of shade in summer; leaves fall in winter providing more sun then. The north side of the house is about 90% windows and fewer trees for lots of natural indoor light. The house is two-story rectangular box without any in/out protusions or changes to roof line. Inside, the front of the house is not used much (living/weight room, dining room) while the back of the house is where time is spent (eat-in kitchen, great room, den, master br). I think the same house on a different bit of land and facing a different direction would have much higher energy costs.

Also how one sets the thermostats, how long one spends in the shower, and size of refrigerator probably have a lot to do with energy costs.

[Valuethinker]

A thread that was resurrected from 2011 about building a new home reminded me... My wife and I currently live in a townhome, and have plans to move into a single-family home sometime in the next 5 years (no firm date). I'd really like to have a home that is energy efficient. Home prices in our area are pretty high (DC suburbs) and I'm trying to weigh my options so that we don't overspend.

What are some of your experiences with building a green/energy-saving home or renovating an existing home to comply to such standards? I'm trying to figure out what is cost effective, and it's actually somewhat hard to find architects/builders in the area that specialize in such a thing, and even harder to find pricing examples readily. I emailed an architect of a net-zero home that was advertised in the area, and asked him if it was even possible to build such a home for our budget (500-600k total) and he said that it IS possible, but that land is a big cost in the area (all I can find in my school district is plots for $300k).

Seems like passive-solar design (facing south) and an extremely tight envelope are highly important, and that building from scratch is the best way to achieve that.

You are right. It's all about 1). insulation and 2). airtightness.

Everything else is extra-- solar gain is useful but a double edged sword (see below). And it's a lot easier to do at the design and consruction stage than renovations.

How many of us have not sat in a modern, high glass home and thought 'gee I am hot?'.

I had a special edition of a US mag (will look up name later) about energy efficient renovations. The short answer it is it hard once the house is built. Talking $100-150kish for a 'deep renovation'. You've basically got to add insulation either internally or externally, plus air tighness. Plus all the usuals: LED lighting, heat pump etc.

In terms of passive solar that is how the Passivhaus standard is achieved (German invention, most countries have the certification). No separate internal heating system other than lights, hot water etc. However there is a challenge in a US environment-- summers in much of North America tend towards hot and humid. The Canadians also have a 'E home' (used to be called R2000) and some US builders can build to it.

If you put lots of windows for solar gain in for winter then you have overheating issues in summer (and gas is cheap compared to electricity)-- there are windows though that really block that . And the humidity problem (ventilation systems can address that-- Passivhaus uses Mechanical Heat Ventilation and Recovery MHVR systems to ensure enough fresh air but reduce energy loss). When you get a house as buttoned down as a truly energy efficient one, you do have to circulate air in and out (the metric is air changes per hour, a Passivhaus is something like 1/4th a normal house). The contractor has to do a blower test (take the front door off, put a fan in) to certify-- that's something any energy efficient build requires.

Windows are trouble both ways. Even a top class arbon triple glazed is only R7-8, when your walls should be R60 and your roof R100. And then you have the solar gain problem in summer (or even in winter if not properly designed). Big windows, which most home builders want, present a challenge. Any kind of custom windows are truly expensive-- the bigger the panel, the higher the cost. And heave a sigh of relief when the windows actually *fit*-- the glazing is one of the real risk points on any build.

Once you get to say R60 walls R100 roof then it's really not about insulation any more, it's about airtightness (probably the tradeoff is even lower R values than that). That's a bit handwavey you can find the right level, but R60/ R100 feels about right for a highly insulated home.

Underfloor heating systems are popular (work well with heat pumps as heat pumps are more efficient the lower the output temperature water) at least in Europe. If the house is highly insulated you run the heat pump all the time and let it gradually warm up the house. Hot water systems can have less problems with dryness than forced air.

Thermal mass is important and worth thinking about, particularly in summer. The reason Victorian houses 'work' is because they hold their 'cold' a long time but if you put internal wall insulation on, you lose the benefit of that-- insulation cuts you off from thermal mass. Desert houses rely on thermal mass (it's a lot cooler in the desert at night, because there is no moisture in the air to trap the heat)-- walls and floors cool off at night, a traditional desert home can have 3' thick walls.

Being clever about shading is a good start-- architects have the software (latitude and longitude, sun position etc) and you may be able to get access to some tools. The sun is higher in the summer, so a longer overhang on the roof is not a problem in winter and will block out the sun in the crucial 12.00-4.30 period. Deciduous trees help of course too (once they have grown up) but conversely muck up PV systems, fill your evestroughing with leaves, etc.

Also consider roof materials. Good roof materials (ie not black) can reduce heat gain by 10%. In the winter, the sun is lower and less intense, so the loss of heat is less of a problem (that's true up to at least NYC by the way-- Argonne National Labs has modelled this). Note solar panels (if not flush to the roof) also provide some shade value.

Unless you buy a kit home (and there are some really good ones done by Scandinavians and Germans, like Hufhaus, and I presume US equivalents) custom build can be an expensive nightmare with architect client contractor at war, running way over budget-- be very careful. Some of the kit homes are truly energy efficient and modern and should be considered (they make every bit in the factory, so actual erection is very fast).

If you buy and knock down, to build anew, you almost never wind up with a total market value greater than what you spent.

If you are building your own home, or doing a 'deep renovation' then seriously consider putting CAT5 (or latest standard) cables and access points into all the rooms. Works way better than WiFi (and we may eventually decide WiFi is unhealthy) and just about every consumer electronic device seems to be evolving towards using Local Area Networks to deliver services. Futureproofing against home automation.

Also make sure you have 'zoned' heating and cooling systems. And air conditioning system with variable speeds -- the problem is often more the humidity than the temperature, and 'cycling' between too cold and too hot is a significant issue which variable speeds helps with.

Things like solar thermal, solar photovoltaic etc. are just gadgets-- only if you have nailed

[boknows]

Valuethinker, a lot of great points that I've thought about at one point or another.

I do know that roof overhangs can prevent a lot of the overheating issues you mention for passive houses. I've talked with an architect in the area that actually does certified 'passivhaus' homes.

I want to think that building a new home would be a moving saving endeavor in the long run, but it's sometimes a hard sell. We theoretically would be comfortable with paying $550-600k all said and done, but a similar already-standing home can be had for 100-150k less.

[hand]

What are some of your experiences with building a green/energy-saving home or renovating an existing home to comply to such standards? I'm trying to figure out what is cost effective, and it's actually somewhat hard to find architects/builders in the area that specialize in such a thing, and even harder to find pricing examples readily.

What is your goal? Low ongoing energy costs or low environmental impact?

If low environmental impact, I'd think re-using an existing house would likely be better than building from scratch or worse tearing down and rebuilding.

For low ongoing energy costs, I think you're right about a tight envelope. Check out Passivhaus.

[Valuethinker]

Valuethinker, a lot of great points that I've thought about at one point or another.

I do know that roof overhangs can prevent a lot of the overheating issues you mention for passive houses. I've talked with an architect in the area that actually does certified 'passivhaus' homes.

I want to think that building a new home would be a moving saving endeavor in the long run, but it's sometimes a hard sell. We theoretically would be comfortable with paying $550-600k all said and done, but a similar already-standing home can be had for 100-150k less.

I don't think the real estate market now knows how to price energy efficiency-- that's my guess. In particular with gas prices so low, I don't think it's big on the radar screen. If bills are really too high (say someone has an inefficient swimming pool arrangement) then that counts against value--- but efficiency not so much the other way.

So you'd really be looking at being there long enough for the investment to pay back- assuming those savings would at least grow by CPI every year. It's quite a low risk investment in that sense.

There are rebuilds that are passivhaus certified-- I've heard of at least one in the UK. Not quite getting to the passivhaus certification probably saves you quite a bit of money.

I think it's probably better to go for buying an existing home, and renovating. You won't be able to achieve those levels of air tightness most likely (if you can get the zoning, you can add external insulation which will take you to high levels of insulation). You need a contractor who has done this.

My guess, and only that, is for 100-150k you can get say 2/3rds of the way to the equivalent energy use of a really tight new house. Note the other comment, reusing a house is almost certainly going to have less environmental impact ('embodied carbon') than building a completely new house.

[boknows]

Valuethinker, a lot of great points that I've thought about at one point or another.

I do know that roof overhangs can prevent a lot of the overheating issues you mention for passive houses. I've talked with an architect in the area that actually does certified 'passivhaus' homes.

I want to think that building a new home would be a moving saving endeavor in the long run, but it's sometimes a hard sell. We theoretically would be comfortable with paying $550-600k all said and done, but a similar already-standing home can be had for 100-150k less.

So you'd really be looking at being there long enough for the investment to pay back- assuming those savings would at least grow by CPI every year. It's quite a low risk investment in that sense.

Exactly. Barring any extreme circumstances, we plan to be in this theoretical house for 20ish years (whenever kids are off to college, one of which is only currently 10mo old, the other isn't even conceived yet haha). So, we have a decent payback period.

I do understand that buying an existing structure and renovating will have less of an environmental impact, but that's not our #1 priority. It also seems quite a bit more complicated to go the renovation route, in that you really need to look for the correct lot/layout/etc and then spend time drawing up plans, and then renovating. It's a tough choice for sure. While $100-150k in reno costs is doable for us, it seems like if all things are equal (including cost), we'd rather build from scratch.

[Valuethinker]

Aim for a kit house. Which sounds cheap and nasty but is actually the reverse-- the ones I have seen on documentaries have been truly impressive-- the care taken in the factory.

You have probably clicked to all the problems of new builds-- there have been some good threads here. Again and again I read/ hear:

- what's under the ground is unknown til they get there, and that can completely change the project in an expensive way

- anything non standard costs. The rectangular shoebox is always the cheapest to build (fewest angles)

- volume housebuilders make sizeable discounts on materials. To duplicate that, you have to sweat it-- a contractor is more worried about convenience, being on site on time, it's not his money that is going into this-- there are big discrepancies on prices for essentially the same stuff

- high spec interior stuff costs so be wary especially on the kitchens and the bathrooms -- I caused myself considerable grief on a veneer oak floor that way

- anything that is not a standard size (eg cabinet and counter heights) is trouble

- glazing is a big risk point-- anything that does not use standard units is trouble Somehow the glazing never quite fits the window holes, and that means jimming and jamming to make it work.

- the contractor has to have done this before, because working out there on the edge of energy efficiency etc. means a level of detailing, in particular around airtightness that is higher than builders have had to deal with -- make sure they are familiar with blower tests etc.

A wild assed guess (best statistical estimation technique): build costs in London are £200/ square foot ($320). Therefore in suburb of a major north eastern city: $200?

Start a notebook and write down everything clever or interesting you see about homes you pass. Particularly if you are talking to contractors, being able to sketch what you want is really important-- people in the building trades don't tend to be good on words but they can understand pictures.

[ThatGuy]

Underfloor heating systems are popular (work well with heat pumps as heat pumps are more efficient the lower the output temperature water) at least in Europe. If the house is highly insulated you run the heat pump all the time and let it gradually warm up the house. Hot water systems can have less problems with dryness than forced air.

I'm really curious about this. It's always said that radiant heat is more efficient than forced air, and I can see that being the case if you are heating the building all the time. However, in mild climates such as California, you don't need to heat 24 hours a day, even in the depths of winter. Do you, or anyone else, have any literature that speaks to the difference in energy used by radiant vs forced air if the occupants:

a) turn off the heat during the day when they are at work

b) turn off the heat at night because you're asleep under blankets anyways

I would think that the difference between heating air, and quickly heating the huge thermal mass of a floor would shift the efficiency balance towards forced air in the case where the heating needs are 12 or less hours per day.

[Valuethinker]

Underfloor heating systems are popular (work well with heat pumps as heat pumps are more efficient the lower the output temperature water) at least in Europe. If the house is highly insulated you run the heat pump all the time and let it gradually warm up the house. Hot water systems can have less problems with dryness than forced air.

I'm really curious about this. It's always said that radiant heat is more efficient than forced air, and I can see that being the case if you are heating the building all the time. However, in mild climates such as California, you don't need to heat 24 hours a day, even in the depths of winter. Do you, or anyone else, have any literature that speaks to the difference in energy used by radiant vs forced air if the occupants:

a) turn off the heat during the day when they are at work

I don't have direct links to studies (sure they are around. There is a forum on green building in the UK called AECB whose posters are a font of all knowledge on such things).

So to follow your logic, in short, if you use the heating as you describe a radiant system isn't likely to save you energy.

Following the logic in more detail:

OK the heat used is just heat input minus heat lost. If the house is well insulated, then it does not matter much -- there is a loss over just heating the house when you get home, but it should not be huge (depending on external temperature, air tightness, insulation etc.). Also thermal mass kicks in -- the desired temperature is easier to reach when you get home from reradiated heat from the floor and/or walls.

The efficiency gains from radiant heat are:

- it's generally more efficient to heat water than air, and circulate it around (I think)-- not sure about that
- floor hot water systems vs. rads are about 10% more efficient-- I think that is because you are heating the floor, not the walls, so less leaks out, and the heat goes *up* into the room more efficiently. Forced air, the hot air goes up from the ducts to the ceiling, without necessarily heating the room
- the Coefficient of Performance (COP) of a Heat Pump is driven by the difference output v. input temperature (lower better). Since water comes into the house at more or less 10C (5-13 say) then a 35-45 degree radiant floor system is *way* more efficient than a 60+ degree rads system. That's the problem with retrofitting HPs to old houses-- they don't stay warm.

HP manufacturers have charts but you see things like COP of 4.0 at 35C and 2.0 at 50C.

So the big gain on radiant floor heat is if you use a Heat Pump (Air or Ground). Also said to be more comfortable.

So if you have a Victorian home like mine (solid brick walls) having a gas system that puts out 70 degree C water into the rads, that you only run when you are home, is pretty important. You get to modern levels of insulation and it's a different ball game.

(by Regs, our hot water (and Canada too, apparently) has to be 55-60C into the hot water tank, and at that temperature a Heat Pump may not be much more efficient than an electric immersion heater ie COP heading down towards 1.0).

b) turn off the heat at night because you're asleep under blankets anyways

I would think that the difference between heating air, and quickly heating the huge thermal mass of a floor would shift the efficiency balance towards forced air in the case where the heating needs are 12 or less hours per day.

Yes. Probably. Marginally if the house is well insulated, very significantly if it is not.

One of the problems with Heat Pumps (in the UK at least) is it's a change in behaviour over the standard gas furnace/ boiler. In the latter, you only run the thing when you are home-- moves quickly to desired temperature. In the HP case, you run it all the time and rely on the insulation of the house to keep the heat in. If you are used to saving energy by not running the heat, psychologically that is a big shift-- counterintuitive.

(I have this constant row, colleagues turn the thermostat to 28, say (86F) when they are *cold*. I keep trying to explain that the room does not then get warmer any *faster* it just overshoots).

As you know from your point, air heats up quickly (but has low thermal mass) and concrete very slowly.

[ThatGuy]

- it's generally more efficient to heat water than air, and circulate it around (I think)-- not sure about that
- floor hot water systems vs. rads are about 10% more efficient-- I think that is because you are heating the floor, not the walls, so less leaks out, and the heat goes *up* into the room more efficiently. Forced air, the hot air goes up from the ducts to the ceiling, without necessarily heating the room
- the Coefficient of Performance (COP) of a Heat Pump is driven by the difference output v. input temperature (lower better). Since water comes into the house at more or less 10C (5-13 say) then a 35-45 degree radiant floor system is *way* more efficient than a 60+ degree rads system. That's the problem with retrofitting HPs to old houses-- they don't stay warm.

The Cp of air is roughly 1/4 that of water in the normal occupancy temperature range. On top of that, most floors out here have a large dead space underneath, whether it's a crawl space, basement, or a 1st floor. So unless someone goes to the trouble of insulating under their in-floor heating, a significant bit of energy will be lost downwards instead of upwards. This could make a real difference if the lower space is hardly ever, or never occupied.

With regard to directionality, you can get nifty vents that shoot the air out sideways before it rises to the ceiling

I'm just real leery of manufacturer's claims, and I'd like a better understanding of real world comparisons.

[Valuethinker]

- it's generally more efficient to heat water than air, and circulate it around (I think)-- not sure about that
- floor hot water systems vs. rads are about 10% more efficient-- I think that is because you are heating the floor, not the walls, so less leaks out, and the heat goes *up* into the room more efficiently. Forced air, the hot air goes up from the ducts to the ceiling, without necessarily heating the room
- the Coefficient of Performance (COP) of a Heat Pump is driven by the difference output v. input temperature (lower better). Since water comes into the house at more or less 10C (5-13 say) then a 35-45 degree radiant floor system is *way* more efficient than a 60+ degree rads system. That's the problem with retrofitting HPs to old houses-- they don't stay warm.

The Cp of air is roughly 1/4 that of water in the normal occupancy temperature range. On top of that, most floors out here have a large dead space underneath, whether it's a crawl space, basement, or a 1st floor. So unless someone goes to the trouble of insulating under their in-floor heating, a significant bit of energy will be lost downwards instead of upwards. This could make a real difference if the lower space is hardly ever, or never occupied.

With regard to directionality, you can get nifty vents that shoot the air out sideways before it rises to the ceiling

I'm just real leery of manufacturer's claims, and I'd like a better understanding of real world comparisons.

Good point on difference between US and (some) European houses-- British houses generally do not have basements.

I guess it in part depends how well the floor is protected from thermal bridging to the outside walls and the earth.

On the Heat Pump point that's physics, so it is fairly certain ie that a radiant heating system uses a lower temperature and is thus more efficient.

[willardx]

It's great for me to read about this as we are in the planning stage of remodeling our house. We looked for a house that fit our 'needs' list but gave up (not entirely, I keep peeking at what comes on the market). We are doing a major remodeling, basically just keeping the footprint of a 3-storey house with a walk-out basement that was built in 1935. We are taking this opportunity to insulate the walls much better and install radiant heat instead of forced-air. But we want to preserve a nice lake view so we are putting in a lot of windows facing the lake.

Interviewing architects and builders, we met one design-build company who was all about passivehaus and wanted to make our new house as energy-efficient as possible. We went middle of the road and chose comfort and aesthetics while getting (we hope) a big bump up in comfort and efficiency by doing what I mentioned above. For our slab floor basement, the talk is to put in heated walls because it would be too costly to tear out the floor and insulate the new slab from leaching heat downward into the soil. We also want AC and one builder proposed a small network of vents on the 3rd floor of all bedrooms, working with the Heat Recovery Ventilation (?) and heat pump to sandwich the middle/main floor that will not have AC directly. We do have the benefit of large oak trees on the south side that shade in the summer and let in light in winter.

I had a question about moisture in wood floors and radiant heating. Is this a common problem? A builder said white oak for our main floor, which sounds nice, but I don't want cupping or shrinkage as the wood fluctuates between moisture. Concrete on the main floor is not an option, but maybe a high-quality engineered wood that can withstand moisture loss might be an option. I would appreciate any thoughts on that issue.

We decided that this is our house for the next generation (building an in-law master suite on the main), so we are putting far more into this remodel than buying a different house. Even with the land already owned, we are looking at approx. $200/sf, in the NW. Which is probably why I keep peeking at the real estate market, in case a home pops up that saves us the hassle of remodeling/moving out, etc.

[Valuethinker]

I
I had a question about moisture in wood floors and radiant heating. Is this a common problem? A builder said white oak for our main floor, which sounds nice, but I don't want cupping or shrinkage as the wood fluctuates between moisture. Concrete on the main floor is not an option, but maybe a high-quality engineered wood that can withstand moisture loss might be an option. I would appreciate any thoughts on that issue.

.

We have radiant heat on a tiled bathroom floor (electric-- not worth having, in retrospect, takes too long to make any difference and too expensive to run) and rads everywhere else (new extension on a Victorian home).

We were told you can put radiant heat on an an engineered wooden floor. So yes, they claim it can be done. I was a little sceptical but that's just me being cautious I think.

[Valuethinker]

It's great for me to read about this as we are in the planning stage of remodeling our house. We looked for a house that fit our 'needs' list but gave up (not entirely, I keep peeking at what comes on the market). We are doing a major remodeling, basically just keeping the footprint of a 3-storey house with a walk-out basement that was built in 1935. We are taking this opportunity to insulate the walls much better and install radiant heat instead of forced-air. But we want to preserve a nice lake view so we are putting in a lot of windows facing the lake.

All fine and good. If those windows are south facing watch the solar gain-- easy to have an overheating problem especially as it does not sound like your house will be fully air conditioned?

If north facing, the reverse-- it could be quite cold in winter. Consider forking out for good glazing. Either argon triple glazing (the argon will leak out over time, unfortunately, say 10-20 years). Or there is 'low E' glass (Pilkington calls it K glass, there's stuff on the Pilks USA website). I honestly don't remember the differences between hard and soft E coating, but it is worth having.

One mistake I made (north facing windows) was to go for not-very-special triple glazings. Thermal performance ain't that great. On the south windows whihc are slanting roof windows (brand here is called 'Velux') (overheating is a problem in London very few days of the year) I went with a double glazed low E solution, and it works a treat.

If you are going to live in this house a long time, it is worth shelling out for good windows*. Aluminum probably the best (if there is a proper thermal break between inner and outer frame, otherwise they gush heat). Wood good but more expensive than plastic and will require regular repainting. Plastic (PVC) probably the worse-- they last about 20 or so years, get brittle, frames will yellow, are difficult to dispose of in an environmentally sensible way (rules on that stuff keep tightening here). Also (my mistake, we have a door onto a false balcony) the frames and cross bars have to be quite wide (plastic isn't that strong) and it doesn't look great.

Interviewing architects and builders, we met one design-build company who was all about passivehaus and wanted to make our new house as energy-efficient as possible. We went middle of the road and chose comfort and aesthetics while getting (we hope) a big bump up in comfort and efficiency by doing what I mentioned above. For our slab floor basement, the talk is to put in heated walls because it would be too costly to tear out the floor and insulate the new slab from leaching heat downward into the soil.

Even a few inches of insulation on the existing slab will save a lot of heat, if you can afford the loss of ceiling height.

We also want AC and one builder proposed a small network of vents on the 3rd floor of all bedrooms, working with the Heat Recovery Ventilation (?)

I suspect he is talking MHRV -- there are passive systems, and there is mechanical. I think it works fairly well if you have it right. You want variable speed fans (variable speed DC)-- more efficient and quieter. Someone here in one of these threads was singing their praises.

and heat pump to sandwich the middle/main floor that will not have AC directly. We do have the benefit of large oak trees on the south side that shade in the summer and let in light in winter.

Not sure quite what he is proposing -- separate AC for the middle floor?

My parents took a 1920s house, and when Dad retired they put in a high speed 'mini duct' AC system (house has hot water rads). Works well. Ducts in each room about 4" across.

I had a question about moisture in wood floors and radiant heating. Is this a common problem? A builder said white oak for our main floor, which sounds nice, but I don't want cupping or shrinkage as the wood fluctuates between moisture. Concrete on the main floor is not an option, but maybe a high-quality engineered wood that can withstand moisture loss might be an option. I would appreciate any thoughts on that issue.

We decided that this is our house for the next generation (building an in-law master suite on the main), so we are putting far more into this remodel than buying a different house. Even with the land already owned, we are looking at approx. $200/sf, in the NW. Which is probably why I keep peeking at the real estate market, in case a home pops up that saves us the hassle of remodeling/moving out, etc.

Unfortunately you'll probably want to remodel that house .


* payback on better windows does not justify the cost-- 20 years+ is quite possible payback. HOWEVER you do get higher comfort (cold drafts are caused by warm air hitting the windows and sliding down, which starts a circulation cell). Triple is better on sound insulation but if you have sound issues you want specialized windows and/or secondary glazing (the optimal gap between 2 window panes to block noise is around 200mm ie 8", for thermal it is 12-20mm).

[interplanetjanet]

I just looked at utility bills for our 3000+ sq ft McMansion in south Texas for the past year. We paid less than $1550 for electricity and gas.

I do think a noteworthy factor there is your cost for electricity, from what I hear from my friends Texas is overall quite cheap there. I don't know how the OPs electricity rate compares, but it's probably worth thinking about (I consume about half as much electricity as a friend in Dallas, and pay bills twice as large). You're also likely to use much less gas for heating.

It's always said that radiant heat is more efficient than forced air, and I can see that being the case if you are heating the building all the time. However, in mild climates such as California, you don't need to heat 24 hours a day, even in the depths of winter.

That last comment just made me chuckle - I know what you're driving at - but I lived up in the hills of California for a time, where 15+ feet of snow per year are the norm. For what it's worth, we used radiators there.

[TheGreyingDuke]

Look here http://www.unityhomes.com/ for some examples of energy efficient kit homes, I have toured the plant and would utilize their services. They are in NH, likely there are equivalents elsewhere.

[btenny]

I found these energy use studies about a large group of homes built in the last 10 years in the Phoenix area. Maybe the data will help you understand some of the tradeoffs. See below.

Basically the reports says getting the builders to "Guarantee" a utility bill forces them to make good tradeoffs as to how to insulate a home and what kind of AC/heating systems and windows to use versus the costs for these items. The data talks about standard "Code Built" homes versus "Energy Star" homes versus "Guaranteed Performance" homes.

It says the Guarantee homes are 33% better than Code homes and Energy Star homes are 16% better than Code Homes.

It also notes that only 40% of home energy use is for cooling/heating so a 10% reduction in cooling needs only equates to a 4% reduction in energy costs. So better insulation and cooling systems are only part of the energy reduction equation.

http://www.advancedenergy.org/buildings ... udy_v2.pdf

http://www.advancedenergy.org/corporate ... 12007.html

The detail analysis report also talks about what the builders do to make these various homes meet the standards. Good stuff.

Bill

[ThatGuy]

... I know what you're driving at - but I lived up in the hills of California for a time, where 15+ feet of snow per year are the norm. For what it's worth, we used radiators there.

Wait a minute, there's parts of California where you can't go surfing every morning and drink on the beach in the evening!?! What's the world coming to...

[btenny]

Yep there are even places in California where we can go snow boarding and snow skiing in the morning, to the beach for some water skiing in the afternoon and then to the golf course for a few holes followed by an evening walk on the beach. But the best part is doing all this in the same day or even doing it 2-3 days in a row but in a different order.

http://www.jmaventuresllc.com/sites/all ... Alpine.pdf
http://www.tahoevacationguide.com/Activ ... kiing.html
http://www.tahoevacationguide.com/Activ ... lfing.html
http://www.yelp.com/biz/kiva-beach-south-lake-tahoe

Bill

[btenny]

Yep there are even places in California where we can go snow boarding and snow skiing in the morning, to the beach for some water skiing in the afternoon and then to the golf course for a few holes followed by an evening walk on the beach. But the best part is doing all this in the same day or even doing it 2-3 days in a row but in a different order.

http://www.jmaventuresllc.com/sites/all ... Alpine.pdf
http://www.tahoevacationguide.com/Activ ... kiing.html
http://www.tahoevacationguide.com/Activ ... lfing.html
http://www.yelp.com/biz/kiva-beach-south-lake-tahoe

Bill

[Valuethinker]

It also notes that only 40% of home energy use is for cooling/heating so a 10% reduction in cooling needs only equates to a 4% reduction in energy costs. So better insulation and cooling systems are only part of the energy reduction equation.

Intuitively those nmbers don't look right.

They might be true in a very modern insulated home. But I do have some data points

- 19th century Victorian home, England, c. 33,000 kwhr pa (gas and electricity -- elec is about 3,000 kwhr pa (no AC)) - 90% is heating/ hot water (hot water about 10% of that)

- 1920s home, Toronto - about 80% is heating/ cooling

Those Toronto numbers would be consistent with other eastern Canadian homes of which I am familiar. In the Prairies the heating load is far more, AC not a lot less. West Coast not so much.

Just generally, from memory, US electricity consumption (ex AC) is about 5,000 kwhr pa per home. AC then pushes it to something like 12,000 kwhr (ie the average US home spends $1200-1400 pa on electricity). US houses tend to heat = with gas (unhelpfully usually measured in BTU) but that would be on top of that.

So that statistic, intuitively feels quite wrong *unless* we are talking about a modern home with very good insulation (an efficient heat pump would also do that).

I shall see if I can find some hard numbers, later.

EDIT: had a quick look. P.20 in that document. Electricity demand averages 16-17000 kwhr pa in those homes (the study notes that heating in Phoenix is like cooling in Maine ie may be optional). They give figures for AC around 6000 kwhr pa.

So that's the source of their number (the 40%).

I noted the SEER on the ACs Energy Star homes and baseline homes is just about the same (ie between 11 and 12). It's not unusual for a 20-30 year old home to have a SEER 7-8, so there's a big pickup there in upgrading. The big delta in Phoenix seems to be whether there is a swimming pool.

Reading those graphs, I would intuit that Phoenix local building codes (ie the baseline) are sufficiently tight that Energy Star is not a big improvement.

I would say in the climates of NE North America (hot humid summers, cold and very cold winters) that heating and cooling is a much larger proportion of total energy consumption (I would say at least 60%), and so the gains from increased insulation and efficiency are much greater. This would also be true of the UK, where the climate is generally mild (think coastal Oregon and Washington) but energy prices are much higher (say on average double US levels for gas and electricity) but insulation standards are generally very poor.

Similarly if you live in a high energy cost part of the USA (like New England, New York or California) the gains are going to be greater. That's probably also true of Texas (depending where) since Texas climate doesn't do mild, AFAIK-- it's either too hot and humid, or it's cold.

[mm9811]

I'm really curious about this. It's always said that radiant heat is more efficient than forced air, and I can see that being the case if you are heating the building all the time. However, in mild climates such as California, you don't need to heat 24 hours a day, even in the depths of winter. Do you, or anyone else, have any literature that speaks to the difference in energy used by radiant vs forced air if the occupants:

a) turn off the heat during the day when they are at work

b) turn off the heat at night because you're asleep under blankets anyways

I would think that the difference between heating air, and quickly heating the huge thermal mass of a floor would shift the efficiency balance towards forced air in the case where the heating needs are 12 or less hours per day.

I am a long time home builder in California/ Northern Nevada. I have built several hundred homes. Radiant heating is wonderful for cold climates (I've lived in several of my home in lake tahoe). It is very efficient, no drafts and comfortable. Especially in homes with open floor plans, high/volume ceilings radiant is wonderful. In mild California climates it is also very comfortable but the cost/benefit is not there. Radiant heating works by heating up the slab or concrete subfloor and then the slab radiates heat into the living space. The thermostat is set at one temperature and then not changed. Let's say the house is 60 degrees, it might take 12-24 hrs to raise the temperature to 72 degrees. If you turn it off when the slab has warmed the house to 72 degrees it will take days for the house to cool down. So in answer to your question. Forced air for your application is more efficent and cost effective.

[mm9811]

As a long time builder of luxury homes I have often been asked to exceed any code required energy requirements. Some general advise. In the building business there are always "NEW AND INNOVATIVE" products that will "SAVE TIME AND MONEY" and "SAVE ENERGY" blah, blah, blah. They are not to be trusted unless they are by a major manufacture AND have been around for some years. Why do I say this? Many great products are invented, but when subject to real world field conditions do not work or live up to there claims for one reason or another. Dual Glazed windows, which I recommend everyone use in every climate are now proven technology. However, when they were introduced they were built in very low volume and often experienced problems with seals leaking, structural issues in the window due to the weight of the glass, expansion contraction issues etc. Unfortunately the homeowners are the beta testers for the building supply industry. If you think logically about it, it makes sense that it takes years for new products to be refined and ready for prime time. And many of them go by the wayside.
Alright that is my rant on don't believe everything you read. As far as energy efficiency goes, with new construction or rebuild you are going to have to find a builder that pays attention to details. Sloppy workmanship will kill an energy efficient house. Walls should be fully insulated. This includes foam in cracks and crevices around window and door framing. Special attention to all electrical and plumbing in outside walls. The exterior should be wrapped with "TYVEK" or similar material and properly sealed at seams, windows, doors and other penetrations. Roofs obviously should be well insulated, and use of reflective film in colder climates is also effective. Heating ducting should be primarily within the conditioned space as opposed to in the attic if possible. Beyond, these general guide lines the local, heating and cooling requirements very I can't give much more advise. One other thing to consider is how traditional homes are built in your area with respect to orientation to the sun, roof overhangs etc. Solar heat gain can be very beneficial and very problematic so both sides of the coin must be addressed.
Please be skeptical of all payback claims of the latest products I have found them to be generally very exaggerated or done under ideal conditions to show what great products they are.
Find a good reputable builder, have him show you other houses under construction and have him point out the details. Ask him about cost/benefit of everything. If he can't explain it to you, move on. (I am not a great writer, but I could explain walking around a house hundreds of important details that are important, and often ignored or done poorly by others). On the contractors side for energy efficiency, quality of construction and enjoyment of your home it is all about the details. From the architects side site considerations are very important if the parcel of land allows choices. If the parcel does not allow choices than it comes down to solar heat gain issues versus, privacy, view, neighborhood issues. Please don't take the architects word for everything, if thing don't make sense ask questions (same goes for the builder). Also architects are notorious for designing what they like (not necessarily what you like). For many people I recommend find a builder first and let him recommend a couple or architects.
Someone mentioned "kit homes". In theory they can be great, I have often wanted to use them for speed of production and quality control issues, but personally I have not been able to pencil the costs out.
Someone also mentioned costs of finishes in a home. This is probably the biggest budget buster for people building custom homes. It is very easy to walk into a specialty store (tile, plumbing, light fixtures etc) and fall in love with some very expensive items. Keep your budget in mind and force yourself to stay within it. There are many creative ways of achieving a high end look at a much lower cost. For example recently did a job with a specialty onyx fireplace facing that cost around $40 per square foot for the material. As it was only about 20 square feet the cost was worth it for the impact it brought. Another customer saw this and did a whole wall in a bathroom and although it was magnificent, the cost was 10 times as much and the impact was (IMHO) over the top.
I apologize for my writing abilities, or lack thereof, if you have specific questions let me know. I have built everything from starter homes to 20 million dollar estates.

[Valuethinker]

As a long time builder of luxury homes I have often been asked to exceed any code required energy requirements. Some general advise. In the building business there are always "NEW AND INNOVATIVE" products that will "SAVE TIME AND MONEY" and "SAVE ENERGY" blah, blah, blah. They are not to be trusted unless they are by a major manufacture AND have been around for some years. Why do I say this? Many great products are invented, but when subject to real world field conditions do not work or live up to there claims for one reason or another. Dual Glazed windows, which I recommend everyone use in every climate are now proven technology. However, when they were introduced they were built in very low volume and often experienced problems with seals leaking, structural issues in the window due to the weight of the glass, expansion contraction issues etc. Unfortunately the homeowners are the beta testers for the building supply industry. If you think logically about it, it makes sense that it takes years for new products to be refined and ready for prime time. And many of them go by the wayside.
Alright that is my rant on don't believe everything you read. As far as energy efficiency goes, with new construction or rebuild you are going to have to find a builder that pays attention to details. Sloppy workmanship will kill an energy efficient house. Walls should be fully insulated. This includes foam in cracks and crevices around window and door framing. Special attention to all electrical and plumbing in outside walls. The exterior should be wrapped with "TYVEK" or similar material and properly sealed at seams, windows, doors and other penetrations. Roofs obviously should be well insulated, and use of reflective film in colder climates is also effective. Heating ducting should be primarily within the conditioned space as opposed to in the attic if possible. Beyond, these general guide lines the local, heating and cooling requirements very I can't give much more advise. One other thing to consider is how traditional homes are built in your area with respect to orientation to the sun, roof overhangs etc. Solar heat gain can be very beneficial and very problematic so both sides of the coin must be addressed.
Please be skeptical of all payback claims of the latest products I have found them to be generally very exaggerated or done under ideal conditions to show what great products they are.
Find a good reputable builder, have him show you other houses under construction and have him point out the details. Ask him about cost/benefit of everything. If he can't explain it to you, move on. (I am not a great writer, but I could explain walking around a house hundreds of important details that are important, and often ignored or done poorly by others). On the contractors side for energy efficiency, quality of construction and enjoyment of your home it is all about the details. From the architects side site considerations are very important if the parcel of land allows choices. If the parcel does not allow choices than it comes down to solar heat gain issues versus, privacy, view, neighborhood issues. Please don't take the architects word for everything, if thing don't make sense ask questions (same goes for the builder). Also architects are notorious for designing what they like (not necessarily what you like). For many people I recommend find a builder first and let him recommend a couple or architects.
Someone mentioned "kit homes". In theory they can be great, I have often wanted to use them for speed of production and quality control issues, but personally I have not been able to pencil the costs out.
Someone also mentioned costs of finishes in a home. This is probably the biggest budget buster for people building custom homes. It is very easy to walk into a specialty store (tile, plumbing, light fixtures etc) and fall in love with some very expensive items. Keep your budget in mind and force yourself to stay within it. There are many creative ways of achieving a high end look at a much lower cost. For example recently did a job with a specialty onyx fireplace facing that cost around $40 per square foot for the material. As it was only about 20 square feet the cost was worth it for the impact it brought. Another customer saw this and did a whole wall in a bathroom and although it was magnificent, the cost was 10 times as much and the impact was (IMHO) over the top.
I apologize for my writing abilities, or lack thereof, if you have specific questions let me know. I have built everything from starter homes to 20 million dollar estates.

I don't think you should feel defensive about your writing abilities.

What you write is perfectly clear, at least to me.

Thank you for adding some real world experience and insight to this discussion.

[serocs]

This is in response to the original post. I skimmed through the rest of the posts, but some of them were tomes that I didn't make it through.

I am not a professional builder, but I have worked extensively on two homes in Virginia: one was a build-from-scratch energy efficient home (LEED Platinum) and one was a energy efficient renovation (left before end of project so not sure LEED level). I was the mechanical engineer on both of these projects, so that is the approach I have to efficient design.

Something that you need to know building in Virginia (and by extension, around DC): the majority of days in Virginia are heating days (approximately 2 out of 3 days). This means you need to worry far more about heat retention than avoiding heat. You mentioned that you understand that roof overhangs can offset the heat in the winter so I won't speak to that point.

As you mention, insulation and air envelope are the most important things to focus on up front. These are very difficult to change once the house is completed (and one of the issues with doing energy efficient renovations), so it is important to do it right up front. For both insulation and air envelope, you cannot do better than foam insulation. Closed cell foam has a much higher R rating, but if you ever plan on doing any sort of work inside the walls once the insulation is in place, keep in mind that closed cell insulation will need to be cut out and replaced. Open cell foam is much easier to deal with in walls and without too much of a loss of R value. There are obviously more efficient ways to build a home than using studs, but prices skyrocket. If you are interested I can tell you a bit more about those options.

If you do plan on doing a renovation, realize that the thickness of the walls is set. There is only so much insulation you can get into a set amount of space.

Valuethinker mentioned that you can use triple pane windows. Be warned that triple paned windows are INCREDIBLY expensive. I wouldn't even consider them in your price range. The efficiency rating per cost is much better if you stick at the double paned level and worry more about the quality of the frame (and its heat transfer properties).

Photovoltaics (which are for electricity) are still not really cost effective. We put 100k worth of PVs on the new-construction house, but only because they were donated. They are most likely out of reach for the price range you are discussing.

You should definitely consider either solar hot water and/or on demand hot water. Prices have come down significantly for both and should be within your reach.

I have a lot more information I could give you, but I don't really want to give you a wall of text (which I may already have failed at). What it comes down to is that to get an equivalently efficient renovation you will go through many more headaches and probably pay more to get it done correctly.

[ThatGuy]

I have a lot more information I could give you, but I don't really want to give you a wall of text (which I may already have failed at). What it comes down to is that to get an equivalently efficient renovation you will go through many more headaches and probably pay more to get it done correctly.

I, for one, would be keenly interested in any additional tips or insight you could add to a general energy efficient home design discussion. I would also like to hear more from mm9811, particularly in what he finds is cost effective in his specific geographical region.

[BillyG]

I've studied this subject in depth, recently went through a big renovation where we applied a number of energy saving technologies, and I used to be a carpenter and have done some of these myself.

You do need a builder who is "into" these things and cares about doing it right. Many builders and architects have little understanding of air barriers versus vapor barriers and foam versus cellulose, and what works best in a particular climate. But others do.

I suggest that you study the treasure trove of information available here:
http://www.buildingscience.com/

I spent untold hours with the materials on this website and I learned a lot. (My architect kept saying they should be paying me instead of vice versa. Too bad it didn't turn out that way!) Joe Lstiburek at Building Science is the guru in this area, with a combination of engineering and building experience. He knows what works and what doesn't, and he won't venture into untested areas. They do full design services and they also will review any draft design your architect has and suggest changes. But it would best to get them involved early.

I can also recommend this website. Although it has a lot of amateur opinions it does have some useful information.
http://www.greenbuildingadvisor.com/

What did we do? XPS foam panels under all the new slabs, foam panels on all the basement walls (with seams taped), spray foam and dense-pack Spider insulation against the roof, spray foam on the rim joists, and spray foam and/or dense-pack Spider insulation in the walls, depending on if the walls were open or not. All spray foam was closed cell. And we were very anal about all window flashing, and sealing every penetration during construction.

Spider is a very fine and fluffy fiberglass insulation that blocks airflow much better than typical fiberglass insulation (which we did not use anywhere in the house). Make sure that you specify "dense-pack" to block airflow. See http://www.specjm.com/products/sprayin2/spider.asp We opted out of using cellulose because the original house is brick with unknown flashing and any water leakage would have been disastrous with cellulose in the walls.

For some walls that we wanted to make thicker for insulation we put horizontal 2x2 strapping across the studs, adding 1-1/2" thickness to the walls. This also greatly reduced thermal bridging through the studs. Google "Mooney walls."

I spec'd rain screen walls in the new cosntruction areas and top and bottom weeps/vents in the brick walls to promote drying of the structure should (when) there is water instrusion. We also used wider overhangs. All windows were replaced with Marvin casements that seal tightly. Good low-E double glazing was used although we should have been smarter about varying the low-E coatings on the north versus south sides of the house. We used some Solatubes to get natural light into otherwise dark spaces.

If you use can lights I suggest you go with Cree CR6 LED bulbs to save energy. They can be dimmed much lower than most LED lights and the light quality is fantastic! 2700K color temperature.

There are lots of other details, but too much to get into here.

Good luck!

Billy

[sls239]

To be honest, energy efficiency is not the be all end all of environmentally friendly. I would suggest that you look at what you really mean when you say you would really like a home that is energy efficient. Get a little more detailed about the things that are important to you and allow that to guide your decision and realize that there isn't likely to be a perfect solution. It may be that choosing an existing home is more in line with what you really want, even if it isn't as energy efficient as a specially built new home.

[mm9811]

To be honest, energy efficiency is not the be all end all of environmentally friendly. I would suggest that you look at what you really mean when you say you would really like a home that is energy efficient. Get a little more detailed about the things that are important to you and allow that to guide your decision and realize that there isn't likely to be a perfect solution. It may be that choosing an existing home is more in line with what you really want, even if it isn't as energy efficient as a specially built new home.

I agree with this. Energy efficiency is a factor, just as many, many other things are. It is all a trade off.

Billy G got it right with..

And we were very anal about all window flashing, and sealing every penetration during construction.

Most of the failed projects I see come down to the details.

I agree with all of serocs post. This is exactly what I was talking about regarding cost/benefit and time for a product to mature.

Valuethinker mentioned that you can use triple pane windows. Be warned that triple paned windows are INCREDIBLY expensive. I wouldn't even consider them in your price range. The efficiency rating per cost is much better if you stick at the double paned level and worry more about the quality of the frame (and its heat transfer properties).

Triple pane have been around for 20years+ but they are generally a waste of money.

For all the others reading this or any other building information. Building techniques vary greatly from one part of the country to another. They vary in different climates, different codes, different citities, different altitudes etc. Local knowledge is best, but that doesn't mean you can't research what works in similar climates to yours

[interplanetjanet]

Photovoltaics (which are for electricity) are still not really cost effective. We put 100k worth of PVs on the new-construction house, but only because they were donated. They are most likely out of reach for the price range you are discussing.

Thank you for your post, it was very informative.

I do have to say that I think the decision for or against PV solar depends heavily on where you are located, the tax incentives available to you, and your marginal rate for power. In areas where summer air conditioning is desirable and time of day metering can push electric rates past 50 cents per kw-h, solar can make a lot of economic sense. A friend of mine has kept all of the numbers from his solar install and just finished nominal payback in about five years, this is reasonably good as far as I'm concerned.

I am likely to buy within the next several years and energy efficiency is a key concern of mine - electric & gas bills are my largest expense after housing and food.

[Valuethinker]

As you mention, insulation and air envelope are the most important things to focus on up front. These are very difficult to change once the house is completed (and one of the issues with doing energy efficient renovations), so it is important to do it right up front. For both insulation and air envelope, you cannot do better than foam insulation. Closed cell foam has a much higher R rating, but if you ever plan on doing any sort of work inside the walls once the insulation is in place, keep in mind that closed cell insulation will need to be cut out and replaced. Open cell foam is much easier to deal with in walls and without too much of a loss of R value. There are obviously more efficient ways to build a home than using studs, but prices skyrocket. If you are interested I can tell you a bit more about those options.

Terminologies differ, but in Europe the lowest U (u = 1/R and multiply R by 5.6 to get North American R) is from PIR foam (poly isocyanate). Brand names are Kingspan, Celotex, Knauf (I think Celotex is the generic term like Scott towels, Scotch tape etc.).

As you say once you get to a certain insulation value, then it's all about air tightness. Which is about finish/ detailing as much as anything else-- ie a careful and knowledgeable contractor.

[Valuethinker]

Probably the other thing to mention is the emerging problem, as we insulate our houses more and more, is moisture/ condensation. Particularly for renovated homes that were not built to be that airtight and insulated, the problem of moisture (cooking, breathing, showers etc.) out migrating and condensing in the walls or at key cold points can be significant.

That is something that you need good advice on.

[Valuethinker]

Valuethinker mentioned that you can use triple pane windows. Be warned that triple paned windows are INCREDIBLY expensive. I wouldn't even consider them in your price range. The efficiency rating per cost is much better if you stick at the double paned level and worry more about the quality of the frame (and its heat transfer properties).
y.

One thing I got wrong was to specify triple glazed (a bathroom window and a door onto a false patio 'Juliette balcony'). Without looking at thermal performance ratings (didn't know much about them, then). A low E double glazed would have done just as well.

I think with frames PVC plastic is OK for thermal bridging, but has lots of other issues (width, recyclability or lack thereof). Aluminium is expensive, durable, low maintenance and terrible for bridging unless a thermal break is explicitly included. Timber is traditional, pretty, but requires recurrent maintenance (if repainted every 5-10 years will last essentially forever-- we still have some original windows).

My triple glazes are facing essentially due north and I am over 50 degrees north latitude (Britain is warm because of the ocean currents, not its latitude!). I do not regret the extra cost, even with those windows you can feel the heat sucking out-- there is never any direct sunlight on those windows. Our winters are much warmer than North American on average, but recent years have been quite cold (jetstream has apparently shifted).

Also we put in domes as skylights into the roof, and again you can walk under them and feel the cold draught-- so I don't regret the extra expense.

But it is basically about being selective.

[Valuethinker]

This is in response to the original post. I skimmed through the rest of the posts, but some of them were tomes that I didn't make it through.

I am not a professional builder, but I have worked extensively on two homes in Virginia: one was a build-from-scratch energy efficient home (LEED Platinum) and one was a energy efficient renovation (left before end of project so not sure LEED level). I was the mechanical engineer on both of these projects, so that is the approach I have to efficient design.

Something that you need to know building in Virginia (and by extension, around DC): the majority of days in Virginia are heating days (approximately 2 out of 3 days). This means you need to worry far more about heat retention than avoiding heat. You mentioned that you understand that roof overhangs can offset the heat in the winter so I won't speak to that point.

Seroc

You obviously know a lot about this! Thank you for sharing your insights.

One thing I would say is that whilst if you have natural gas, it's not too expensive to keep the middle class home in the Mid Atlantic area warm (assuming good insulation and airtightness). However although modern air conditioners are efficient, being too hot (or rather too humid) in the Virginia/ DC climate would be really unpleasant. My parents in *Ontario* so a less extreme summer, had to retrofit air conditioning to a 1920s house-- as they got older, the summer got too much to bear.

Electricity is much more expensive than gas, and so efficiency in AC is rewarded in comfort and cost-- high SEER (I would say for a new system go for SEER15, you only do this *once* in your time in a house), variable speed etc. At a high heat pump efficiency this should not be too costly.

Also therefore careful re overheating. I'd rather lose some thermal gain in winter, than be too hot in summer in a climate like Virginia's. Those old houses with high ceilings, ceiling fans, big porches, were designed to keep cool in that climate.

[bpp]

I
I had a question about moisture in wood floors and radiant heating. Is this a common problem? A builder said white oak for our main floor, which sounds nice, but I don't want cupping or shrinkage as the wood fluctuates between moisture. Concrete on the main floor is not an option, but maybe a high-quality engineered wood that can withstand moisture loss might be an option. I would appreciate any thoughts on that issue.

.

We have radiant heat on a tiled bathroom floor (electric-- not worth having, in retrospect, takes too long to make any difference and too expensive to run) and rads everywhere else (new extension on a Victorian home).

We were told you can put radiant heat on an an engineered wooden floor. So yes, they claim it can be done. I was a little sceptical but that's just me being cautious I think.

Radiant heat on engineered wooden flooring is very common in Japan. Works fine.

[Epsilon Delta]

Terminologies differ, but in Europe the lowest U (u = 1/R and multiply R by 5.6 to get North American R) is from PIR foam (poly isocyanate). Brand names are Kingspan, Celotex, Knauf (I think Celotex is the generic term like Scott towels, Scotch tape etc.).

It is more correct to say the foam has the highest R per inch.

R (and U) values deal with heat transfer per unit area, with no concern for the thickness. You can get a high R value with solid steel, if you use enough steel. As a practical matter some earth sheltered homes, and many basements, use several meters of dry earth to get a high R value.

[BillyG]

Probably the other thing to mention is the emerging problem, as we insulate our houses more and more, is moisture/ condensation. Particularly for renovated homes that were not built to be that airtight and insulated, the problem of moisture (cooking, breathing, showers etc.) out migrating and condensing in the walls or at key cold points can be significant.

That is something that you need good advice on.

The www.buildingscience.com website has a lot of excellent information about these issues, which basically fall into two areas.

The first is you (actually the OP) need to use good ventilation fans/systems for bathrooms and kitchen areas. We used remote vent fans to reduce indoor fan noise. Bath vent fans are on timers, and I just changed the vent fan control in the kid's bath to motion sensors because the teenage girls sometimes (always?!) take showers that outlast the timer switch.

Second, you need to consider wetting and vapor drive in your climate in view of your building and insulation materials. Always assume that bulk water will get into your exterior walls at some point, due to building material failures, high wind rainstorms, ice dams, etc. With tight air sealing how will your walls dry? With your wall cladding materials nailed tightly to your wall sheathing and trapping water against it and the Tyvek, how well will your walls dry? With vapor drive you need to consider your vapor barriers and interior/exterior wall materials.

With closed cell spray foam in my walls (note there are big differences between closed cell and open cell foam -- many people treat them interchangeably which is a huge mistake), if my wall sheathing gets wet there is absolutely no way my walls could dry to the inside. That is why I used rain screen walls -- so the sheathing can easily dry to the outside. The rain screen walls also allow any bulk water to drain easily from the wall assembly.

With the closed cell foam against my roof I added vent baffles and ridge/eave vents. Most builders do not add baffles to a "hot roof" but building science and real world experience show that vent baffles promote drying of the roof sheathing if it gets wet for any reason (exterior roof leak or vapor drive from the house interior) and they help reduce ice dams (admittedly not an issue in coastal California). Note that open cell foam against a roof is a bad idea in colder climates because open cell foam is vapor permeable and water vapor can pass through the open cell foam and condense on a cold roof surface, rotting the roof sheathing from the inside out.

Billy

[serocs]

Excellent info BillyG. You are absolutely right. It is important to keep water issues in mind. However, if the wall is designed correctly (with some sort of rain screen as you mentioned), drying to the inside should not be necessary. You may have implied this, but I wasn't sure and just wanted to reiterate it.

Ideally a house should have no unplanned air/vapor exchange with the outside. This does mean that in an air-sealed house you will need mechanical ventilation to keep the air from getting stuffy (or worse) inside. Luckily mechanical ventilators are inexpensive.

Another thing that BillyG touched on: ventilated attics (and crawl-spaces) are a thing of the past. Not all builders like this new science, but they are indeed better. I don't remember all of the reasoning right now, but I can look it up if someone is interested.

[ThatGuy]

There seem to be several builders in this thread, so I'm hoping I can get a quick answer to a niggle. I understand the benefits of foam sheathing, but I can't get past the fact that it's polystyrene. Other than moving to a double stud wall, and taking up extra inches, is there a viable alternative to rigid sheathing that would still create a thermal break in a standard stud wall?

[thatwhichisgood]

This is a wonderful way to get out and about and see lots of different flavors of energy efficient housing. Talk to owners etc.... We have seen many various types of buildings, not just solar on them.

http://www.ases.org/solar-tour/


Of course taht assumes that their are folks in your area doing it.

[BillyG]

Excellent info BillyG. You are absolutely right. It is important to keep water issues in mind. However, if the wall is designed correctly (with some sort of rain screen as you mentioned), drying to the inside should not be necessary. You may have implied this, but I wasn't sure and just wanted to reiterate it.

Ideally a house should have no unplanned air/vapor exchange with the outside. This does mean that in an air-sealed house you will need mechanical ventilation to keep the air from getting stuffy (or worse) inside. Luckily mechanical ventilators are inexpensive.

Another thing that BillyG touched on: ventilated attics (and crawl-spaces) are a thing of the past. Not all builders like this new science, but they are indeed better. I don't remember all of the reasoning right now, but I can look it up if someone is interested.

Yes, the rain screen siding allows drying to the outside. the website www.buildingscience.com has a lot of information about sealed crawlspaces, attics, etc., and the reasons for building this way.

There seem to be several builders in this thread, so I'm hoping I can get a quick answer to a niggle. I understand the benefits of foam sheathing, but I can't get past the fact that it's polystyrene. Other than moving to a double stud wall, and taking up extra inches, is there a viable alternative to rigid sheathing that would still create a thermal break in a standard stud wall?

If you want to greatly reduce thermal bridging in an existing house, you need to give up extra inches on the outside and/or inside. With a Mooney wall you give up only 1-1/2" on each wall.

What is your issue with polystyrene? Is it the fact that it is made from oil? If so, consider you are using it once but the energy savings are cumulative over time. For exterior insulation alternatives you can look into rigid mineral wool panels.

Billy

[ThatGuy]

If you want to greatly reduce thermal bridging in an existing house, you need to give up extra inches on the outside and/or inside. With a Mooney wall you give up only 1-1/2" on each wall.

I'm not concerned over a couple of inches, or outside inches, I was more concered over the 5.5" for an extra stud + whatever spacing one would use in a double stud wall. Unless staggered, which seems more trouble than it's worth with roof supports. That said, I've yet to see any actual tests of a Mooney wall, and it strikes me as bit of a joke. I have a hard time seeing how having the studs on the outside, still attached to the wall and being used as a thermal bridge, but the 1.5" of a cross member will provide enough of a break to be worth the added effort.

What is your issue with polystyrene? Is it the fact that it is made from oil? If so, consider you are using it once but the energy savings are cumulative over time. For exterior insulation alternatives you can look into rigid mineral wool panels.

Polystyrene, while recyclable, is hardly ever acccepted for recycling, and it takes a long, long time to break down. That's my issue. There are valid uses for oil based products, but I think there's already too much polystyrene out there from general consumption practices.

I'm less clear if polystyrene can even be recycled in the traditional sense. Most plastics are recycled by downcycling them, however polystyrene is a thermoplastic...

Thanks for the mineral wool idea, I'll look into that.

[leonard]

On a new build, I would definitely design and build with Structural Insulated Panels (SIPs). Extremely air tight and energy efficient.

Then, depending on location and exposure, I would design for passive solar, solar water heater, active solar, and possibly wind generated power (if you are fortunate or UNfortunate enough to be building a location that windy). Would also analyze geothermal for the site - although this is very expensive, so may not make sense.

Personally, I would take 100% advantage of free rain water with a huge rain catchment system - at least for outdoor watering, if not gray water systems indoors. This is very easy to design in to a new house, but more challenging to retrofit - particularly locating the tank.

So, I would emphasize SIP's building structure with great passive solar design - and then build the rest out from there.

[BillyG]

Thatguy,

I'm sorry you think a Mooney wall approach to thermal bridging is a joke. I am not going to do your work for you but it is obvious you should study thermal bridging more carefully:
http://www.google.com/search?q=thermal+ ... tartPage=1

Wood is R1 per inch and a significant percentage of the surface area of a traditional wall is thermally bridged when you count studs on 16 inch centers, top and bottom plates, window and door headers, cripples, typical corner framing, etc. The percentage of wall being thermally bridged significantly decreases with a proper Mooney wall. I did it in some areas of my house and it works well, and it is quieter. But if you want to do something more expensive than a Mooney wall it is up to you. You could attach 2x3s or 2x4s on edge and get additional thickness as you see fit without all the expense and complications of double wall alternating stud framing.

I still don't understand your point about polystyrene -- if you're putting it in your home you want it to last -- but you need to do what makes you feel good. You would be hard pressed to find a better energy saver in terms of R value per inch than closed cell foam, and some of it is soy based rather than petroleum based(but I think that is more of a marketing ploy to make people think they are being "green"). You could use less insulation and feel more green even though you use more energy, or make your walls thicker and use the insulation you want at the expense of addditional framing lumber and cost. It's all about tradeoffs and you being happy with your choices.

Good luck with your project.

Billy

[ThatGuy]

I don't have access to thermal building software, but if you do, or if you know of an actual study modeling Moody walls as opposed to a general thermal bridging search, I'm all for looking at real math

I'm sorry you took this personally, I will note that I said "a bit of" as in not all it's cracked up to be, not as in it's a scam. I'll take a look at any actual study you have to share regarding Mooney Walls, or cross-hatching as they've been known for decades, but Dana1 pretty much sums up my feelings.

he most you'd get out of 2x2 Mooney stringers even using a full R3.7 for the additional cellulose in such an analysis is a whole-wall R of ~R15.25, (which is only R1 better than a 2x6 24" o.c. approach- no foam, according to Oak Ridge.)
...


In the Mooney wall approach the plates band joists & subfloor are still not thermally broken and there remains a ~0.9% clear wall thermal bridging of the timber at the cross points. The U value of even that sub-1% adds up in a thicker assembly even using fantasy K-values for wood.

It's all conjecture without actual numbers/tests anyways.

With regard to polystyrene, it might make more sense if I call it Styrofoam. At any rate, it's not that I want something to break down inside the walls, it's that I don't want my house material to still be floating around in the Great Pacific Garbage Patch in 10,000 years. Any energy I save by burning less fossil fuel will be negated by that stuff hanging out in the environment for eons.

[BillyG]

Thatguy,

You're mixing new construction and retrofit construction when you compare a 2x4 Mooney wall with a new 2x6 stud wall. Which one are you considering? A new 2x6 wall costs more with less performance than a Mooney wall using 2x4 studs.

By the way, your Dana1 reference said

"A 16" o.c. 2x4 studded Mooney wall w 2x2 or 2x3 16" o.c. laterals may run about R19 as a clear-wall value, but doesn't thermally break the band joist or plates, subfloor, etc. It's maybe R16-17 for whole wall (which isn't bad- it's a huge improvement over the R10 you'd get with just the 2x4s and cellulose)"

A 60-70% improvement in insulation value for a Mooney wall sounds good to me, especially for the cost differential.

There's a ton of useful information if you take the time to look for it, and there are whole wall R value calculators too.

If you want to reduce thermal bridging and increase performance put the insulation on the outside. Polyiso foam panels are better than polystyrene, but you'll need to figure out the green quotient. Roofers frequently resell and recycle foam panels removed from roofing projects.

See more here, including mineral wool panels.
http://www.buildingscienceconsulting.co ... ontrol.pdf

There are lots of studies comparing whole wall R values to the nominal (insulation) R value. You can see here that a typical 2x4 stud wall with fiberglass batt insulation has only 70% of the insulating value of the center of wall measurement -- no doubt a Mooney wall would give you a significantly higher R value at minimal cost. During construction the horizonla straps can often be cut from bowed or short pieces of framing lumber that would otherwise go in the dumpster. Now that is green.
http://www.ornl.gov/sci/roofs+walls/res ... ntent.html

There are other approaches too, including Larsen trusses.

Billy

[ThatGuy]

Thatguy,

You're mixing new construction and retrofit construction when you compare a 2x4 Mooney wall with a new 2x6 stud wall. Which one are you considering? A new 2x6 wall costs more with less performance than a Mooney wall using 2x4 studs.

I'm not mixing anything. It's really silly to compare a 2x4 wall to a wall that has an extra 1.5" of insulation, even disregarding any potential benefits of thermal bridging. I happen to be interested in new construction, so 2x6 vs SIP construction. I view Mooney walls as a fine DIY thing, but hardly anything a professional would recommend.

By the way, your Dana1 reference said

"A 16" o.c. 2x4 studded Mooney wall w 2x2 or 2x3 16" o.c. laterals may run about R19 as a clear-wall value, but doesn't thermally break the band joist or plates, subfloor, etc. It's maybe R16-17 for whole wall (which isn't bad- it's a huge improvement over the R10 you'd get with just the 2x4s and cellulose)"

A 60-70% improvement in insulation value for a Mooney wall sounds good to me, especially for the cost differential.

There's a ton of useful information if you take the time to look for it, and there are whole wall R value calculators too.

No kidding, I've found those ORNL calculators and others beforehand. Do note that the ORNL calculators hows a 2x6 with 16oc cellulose as a clear wall R-18 with a whole wall of R14. I have a hard time beliveing that a Mmoney wall with less total thickness has a whole wall closer to R-18. I keep asking for real studies of this stuff because I work as an engineer and I've seen conjecture be wildly off too many times. If you don't have a blower test, or some other analytical analysis of a Mooney wall, let's just drop it as untested.

If you want to reduce thermal bridging and increase performance put the insulation on the outside. Polyiso foam panels are better than polystyrene, but you'll need to figure out the green quotient. Roofers frequently resell and recycle foam panels removed from roofing projects.

I've contacted a SIPs manufacturer. He was unaware of ANYONE reusing or recycling panels once they've been used in construction. Waste from the manufacturing process is 'recycled' as high density low grade pellets, which is sold to manufacturers in China. This means that it has a finite use life, unlike say, recycling Aluminum cans.

Sure sounds like SIPs have been oversold as a green product.

[BillyG]

Thatguy,

You're mixing new construction and retrofit construction when you compare a 2x4 Mooney wall with a new 2x6 stud wall. Which one are you considering? A new 2x6 wall costs more with less performance than a Mooney wall using 2x4 studs.

I'm not mixing anything. It's really silly to compare a 2x4 wall to a wall that has an extra 1.5" of insulation, even disregarding any potential benefits of thermal bridging. I happen to be interested in new construction, so 2x6 vs SIP construction. I view Mooney walls as a fine DIY thing, but hardly anything a professional would recommend.

ThatGuy, thanks for saying you are interested in new construction. That makes a big difference. This thread started with a discussion of renovations. The fact is you did pick and choose your quotes to support your arguments. I'm an engineer too and I have other advanced degrees. I also used to be a carpenter and still regularly do this sort of work. So we're not exactly talking DIY here. The fact that you brush off thermal bridging tells me you have very little understanding of the factors that affect the thermal performance of building envelopes and for some reason are not inquisitive about learning this subject.

If you don't understand the importance of thermal bridging and the significance of creating a break in the bridge, I can't help you. There is plenty of data if you choose to educate yourself, and the rough calculations are within the grasp of any engineer. You can lead a horse to water but you cannot make him drink.

I am not going to get in a green debate with you. There are plenty of places on the internet where you can have those discussions.

ORNL study using Mooney walls in actual construction:
http://www.ornl.gov/sci/buildings/2012/ ... 41_New.pdf

For photos of a professional builder constructing a new solar house in Rhode Island using Mooney walls and dense-pack cellulose, see here:
http://forums.delphiforums.com/breaktim ... msg=8976.1

Also, you are just plain wrong about recyclying and foam. The highest R value per inch is achieved with polyiso foam board -- and this can be recycled, and you can buy polyiso foamboard made from recycled material. Polystyrene is not easily recyclable but to think that will remain the case for the next hundred years much less 10,000 years is equivalent to believing that science stands still. But you can use polyiso if you are worried about a material that is recyclable today.
http://www.firestonebpco.com/templatefi ... leid=14714

Good luck.

Billy