Attic Retrofit: Spray Foam Insulation [Updated w Images]

[danwhite77]

I am rehabbing a two story house built in 1967 located in the Chicago suburbs. Currently, the attic has a minimal amount of blow-in fiberglass insulation on the attic floor (top of the second floor ceiling). The HVAC system is designed with the furnace in the basement and a large interior column bringing conditioned air up into the attic. This main column then branches out into smaller ducts in the attic that are fed down into the second floor rooms. The duct work in the attic is wrapped in very thin insulation. The house is a full two stories (with partial basement) with a small footprint of about 1000 feet. The roof is low slope, so the attic is low height, but it is a full ventilated attic above the second floor.

The combination of HVAC system design (ducts up into the attic) and under-insulation has, as you can imagine, resulted in a tremendous amount of heat loss this winter. In fact, during -20F days, I've been up in the attic and it's basically room temperature up there. Since I'm located in Chicago, the attic is extremely hot in the summer, heating the duct work carrying cool air. Considering the local climate and layout of the HVAC system, I believe that spray foam insulation on the underside of the roof decking is probably the best approach, effectively turning the attic into conditioned space. I've researched spray foam insulation both here and on the web and there seems to be a large number of conflicting opinions on, e.g., whether open or closed cell spray foam is best for an attic retrofit. My questions to you all are:

1. Does anyone have experience with a similar attic spray foam retrofit that they can share?

2. Thoughts regarding open vs. closed cell spray foam for this application - which is best? And if you have an opinion, do you have a website or document that you could link that discusses your point of view?

3. If I do have spray foam installed, does outside air need to be routed into the furnace/AC?

4. Any spray foam products to avoid or other pitfalls?

Updated:

Chicago just thawed out a bit and it's been raining hard all day so I made the trip up to my attic to see how it did. It's a new roof with new decking, installed October of last year (four months ago). My findings:

1. The roof did well, however there was some moisture at the edge of the eastern exposure (pictured below) presumably due to ice damming (due to miscommunication my wife and I didn't clean the gutter and the gutter is under a large tree). We had huge icicles off of every gutter simply due to the low insulation in the attic. For those in the spray foam camp, does this amount of moisture cause concern, keeping in mind ice damming probably won't occur once the spray foam has been installed?
2. I ran the fan on my furnace and checked for leaks and I didn't find anything obvious. This isn't the same thing as an energy audit, obviously, but I didn't see an obvious or large air leak.
3. You can see what I'm talking about in the images below regarding the duct work. For those in the blow-in insulation camp, could I possibly pile blow-in insulation on top of this duct work? If not, what do you recommend?

Below is my attic in all of its grandeur:

Duct work running length of attic:


The branch duct work on the right hand side of the first image:


Some of the branch duct work on the left hand side of the first image (the top of this duct is 2 or 2.5 feet above the floor of the attic):


The dark stain at the edge is the moisture by the gutter described above:


EPILOGUE EDIT:
(2/16/2015)

Thanks to everyone who weighed in on the spray foam v. blow-in insulation question that I posted here. Ultimately, last fall (2014) I had blow-in insulation installed (R49 total) and had R19 insulation batts draped over the duct work in the attic. Now that we're well into a winter that is comparable to the 2013-2014 winter here in Chicago, I have a pretty good apples-to-apples comparison. So far, our gas usage has gone down by about a third. Also, more importantly, the second floor is very warm and comfortable. Last winter we would freeze upstairs because all the heat went directly to the attic. So basically, the blow-in solution has had the desired effect.

I probably would have gone with spray foam insulation, but I could not find a retrofit installer that I trusted to use (what I believe to be) the right product. And, even if I could, using the correct product would've cost about three or four times what I paid for blow-in insulation, and at that price point it didn't make sense in my situation.

So again, thanks everyone. Stay warm out there!

[RenoJay]

All I know is that I got quotes a few years, and the spray foam insulation was easily 5x more expensive.

[Onyxmeth]

How much R value is currently in the attic approximately? Also what climate zone are you in?

[nyjetfan]

1. Does anyone have experience with a similar attic spray foam retrofit that they can share?

2. Thoughts regarding open vs. closed cell spray foam for this application - which is best? And if you have an opinion, do you have a website or document that you could link that discusses your point of view?

3. If I do have spray foam installed, does outside air need to be routed into the furnace/AC?

4. Any spray foam products to avoid or other pitfalls?

Thanks in advance for any help.

Dan

Hi Dan - Can't speak from direct experience, but I have a friend who did spray foam in a new construction house, and one of the issues/challenges was that many shingle/roofing manufacturers stated it voided their warranty, as the spray foam will prevent the attic from "drawing" the heat out of the shingles/roofing from the back side. Not sure what type of roofing you have installed, but it is possible it could need to be replaced with (or shortly after) the spray foam upgrade due to the high temperatures that the roofing/shingles will experience. Haven't been to my friend's house, nor can I say it is from my experience but it is something worth considering as part of the upgrade project.

[mw1739]

As somebody else mentioned, I think spray foam is easily several times more expense than fiberglass or cellulose insulation. Before I spent that kind of money I would check everything else possible first.

1. Are your ducts sealed? Look for joints and registers where the ductwork may have come loose and is leaking air into the attic. Seal with tape or mastic.
2. Why not just insulate your existing ductwork? Put some of this around the ductwork in your attic: http://www.homedepot.com/p/Master-Flow- ... 5yc1vZc5hi
3. Why not just put some fiberglass batts or blow cellolose into the attic? The home improvement stores will give you the blower if you buy the insulation there. (I've done both methods and feel that blown cellolose provides better coverage. Definitely wear a mask if you're blowing the insulation and/or wear long-sleeves if you're putting down fiberglass.)

I would imagine you could do all three of these things on a Saturday for just a couple hundred bucks.

[danwhite77]

How much R value is currently in the attic approximately? Also what climate zone are you in?

The R value in the attic is probably negative. Seriously. There are many places where there simply isn't any blow-in insulation, the ceiling drywall is it. The insulation wrap around the duct work can't be more than R-4. The existing insulation is basically 1967 era builder's grade insulation which is to say virtually nothing.

Also, regarding climate zone, this is from the wiki on Chicago:

The city lies within the humid continental climate zone (Köppen: Dfa ), and experiences four distinct seasons. Summers are hot and humid, with a July daily average of 75.8 °F (24.3 °C). In a normal summer, temperatures exceed 90 °F (32 °C) on 21 days. Winters are cold and snowy with few sunny days, and with a January daytime average high of 31 °F (−0.6 °C). Spring and autumn are mild seasons with low humidity.

Or did you mean the scale used for plants? If so, I think we're 6a.

[runner9]

Also what climate zone are you in?

I am rehabbing a two story house built in 1967 located in the Chicago suburbs.

[Onyxmeth]

How much R value is currently in the attic approximately? Also what climate zone are you in?

The R value in the attic is probably negative. Seriously. There are many places where there simply isn't any blow-in insulation, the ceiling drywall is it. The insulation wrap around the duct work can't be more than R-4. The existing insulation is basically 1967 era builder's grade insulation which is to say virtually nothing.

Ok. So next up I was going to get into what was mentioned a few posts up. You don't need and definitely shouldn't be insulating the rafters. You're likely to create a moisture problem in the attic. Get the recommended level of R level between the joists as per your climate zone, and let the roof breath. It doesn't need insulation. Personally, I would blow in cullolose.

[danwhite77]

1. Are your ducts sealed? Look for joints and registers where the ductwork may have come loose and is leaking air into the attic. Seal with tape or mastic.
2. Why not just insulate your existing ductwork? Put some of this around the ductwork in your attic: http://www.homedepot.com/p/Master-Flow- ... 5yc1vZc5hi
3. Why not just put some fiberglass batts or blow cellolose into the attic? The home improvement stores will give you the blower if you buy the insulation there. (I've done both methods and feel that blown cellolose provides better coverage. Definitely wear a mask if you're blowing the insulation and/or wear long-sleeves if you're putting down fiberglass.)

Thanks, I have considered what you've described. If the estimate for spray foam comes in at a very high amount, I will probably revert to plan B. Plan B would involve wrapping the ducts and blowing in a mountain of fiberglass insulation to bury the ductwork. The problem with that approach is that the column leading up to the attic is not airtight. In fact, it's the opposite, there are huge gaps on all sides of the column leading into the attic (all the way up from the basement). Basically it's a large metal duct with 2-6 inches between it and the drywall that surrounds it. So there is a huge amount of uncontrolled heat transfer. I supposed you could block this space off at the bottom and blow in a tremendous amount of insulation into the gap leading all the way from the basement to the attic.

I've spent a lot of time in my attic (unfortunately) and I'm just not willing to DIY this job. I am tall, the ceiling (with many nails in it) is low, and I'm just not willing to put up with the aggravation. I may go with the blow-in insulation, but I think given the house design challenges that spray foam would probably be the best solution. If it's also a remotely affordable solution, I'll probably go with it.

[William4u]

As somebody else mentioned, I think spray foam is easily several times more expense than fiberglass or cellulose insulation. Before I spent that kind of money I would check everything else possible first.

1. Are your ducts sealed? Look for joints and registers where the ductwork may have come loose and is leaking air into the attic. Seal with tape or mastic.
2. Why not just insulate your existing ductwork? Put some of this around the ductwork in your attic: http://www.homedepot.com/p/Master-Flow- ... 5yc1vZc5hi
3. Why not just put some fiberglass batts or blow cellolose into the attic? The home improvement stores will give you the blower if you buy the insulation there. (I've done both methods and feel that blown cellolose provides better coverage. Definitely wear a mask if you're blowing the insulation and/or wear long-sleeves if you're putting down fiberglass.)

I would imagine you could do all three of these things on a Saturday for just a couple hundred bucks.

+1
I got a blow in cellulose machine from Home Depot. It was pretty easy with two people.

[jimb_fromATL]

Since you say it's a low attic, I assume there's no real floor that you can walk on, and you mean that the insulation is between the rafters. I also am assuming that your roof is normal shingles rather than something like metal or terra cotta, etc.

If so, I'd suggest that you NOT consider spray foam insulation under the roof. Just use more blown or batt insulation to keep the heat inside the occupied space in winter and outside the living area in summer. And add a lot more wrap insulation on the distribution plenum chamber and pipes.

One big reason is that it does indeed get hot in the attic in the summer. So the attic ventilation helps keep the roof decking cooler on the underside even if it's 100 degrees or more in the attic in the summer, it's a lot cooler than the 140 degrees or more that the roof itself might be in the sun. If you insulate the underside of the roof deck, you'll lose the cooling effect of ventilation of the attic, which can greatly raise the temperature and reduce the life of the shingles.

Plus, you're still heating a lot of unoccupied space in winter, and trying to cool it in summer. Not only are you paying to condition unoccupied space, but it is vented to the outdoors via --presumably-- soffit vents and roof or gable vents. So you'll still be losing a lot of heated or cooled air to the outdoors.

Another problem is moisture. Despite being --probably-- plywood or individual planks for the decking, moisture does escape from the attic through the roof. (A roof is designed to keep rain water and snow and ice out, not to keep moisture in.) If you insulate the underside of the roof you may cause a lot of condensation on the underside because of the cooler air in the attic -- which may eventually lead to wood rot and/or mold problems.

Another point to consider is whether you have enough attic ventilation. Building standards have changed since the 60's and it may need more area for cool air intake (at the soffit or low ends of the gables) and more area for hot air to exhaust with roof vents or vents at the top of the gables.

Yet another point worth some research is whether you need a vapor barrer between the ceiling sheetrock or panels -- whichever it is-- and the insulation. Back in the 60's there wasn't as much attention paid to keeping moisture out of the atttic. Moisture from the living area can seep through the ceiling and condesnse in the insulation, which also reduces its efficency, in addition to possible mold problems.

If your local building codes require it or suggest it, you might want to consider removing the old blown insulation and putting down a vapor barrier before you add a lot more insulation. Or use batts with a vapor barrier. Moisture and condensation in the insulation is usually not a big problem with a thin layer of insulation, but can become a much bigger problem with a much higher insulation factor.

By the way, when you do add insutation, be careful not to block the soffit vents -- and make sure that the installers are careful about it you don't do it yourself. Again, the attic ventilation is important to keep it cooler in the summer and drier in the winter.

There are a lot of websites that go into details about insulation, attic ventilation, moisture control and other things you nee to consider. Even if you don't plan to do it yourself, it will pay to be well-informed so you will know whether a ontractor or salesman is really helping you or just trying to make a sale.

jimb

[Onyxmeth]

Also what climate zone are you in?

I am rehabbing a two story house built in 1967 located in the Chicago suburbs.

i missed that. Climate zone 4 it seems like. R-43 seems to be what is suggested.

[tiguak]

i built new in 2009 and found the builder only put in r36, had hold your temp add the cellulose to bump up to r60. for a 5000 sq ft home it was about 1200 installed. i went for r60 because it will settle down over time and i didn't want to be bothered later on. i think they r located in nw illinois or wis border.

[BillyG]

Dan,

I had this done in our home, built around 1940 in the DC area. I researched it a lot and read hundreds of articles and exchanged correspondence with building scientists and spray foam experts because I wanted to get it right. I have to say there is a lot of misinformation or more likely misunderstanding in the answers you've received so far.

Below I have some links to articles you can read.

You are correct that placing the insulation under your roof so the thermal envelope encloses the HVAC system can be a very good thing.

One of the huge benefits of spray foam is it also creates an air barrier, which is to some extent more important than the insulation value. If you insulate your house and leave a window open you will use a lot of energy and be uncomfortable. Likewise, many people insulate their homes and don't seal the air leaks so they get the same result. You get a lot of bang for your buck by air sealing your house to the extent possible without tearing open your walls (even better if you are opening the walls).

IF you decide to use spray foam under the roof you absolutely need to use closed cell foam unless you also have a vented roof assembly that allows moisture to escape. Do not let them talk you into using open cell foam. Open cell foam is vapor permeable and water vapor can pass through it and condense on the underside of cold roof sheathing. Closed cell foam is vapor impermeable so you will not have this problem is you spray at least 2-3 inches of closed cell foam; to meet the necessary insulation requirements in Chicago I would tend to think 4-6 inches would be much better and probably required by code. The details of how and where they spray the foam are critical to a good quality job. Don't let them spray foam in freezing weather -- above 50 degrees is better.

You do want to foam the rafters to reduce thermal bridging (wood is R1 per inch).

Don't plan on being in your house for at least a few days after they spray the foam. The fumes are bad and you want to give it time to cure.

Get a few quotes and ask lots of questions of the estimators. They usually know a lot about he process and will offer suggestions on the best approach. Above all the company you choose should be very competent. If they screw up the spray foam installation it can be a real mess. While rare, it can happen with inexperienced installers or poor equipment.

Good luck and check out the links below.

Billy

http://www.finehomebuilding.com/assets/ ... -sheet.pdf
http://www.finehomebuilding.com/tool-gu ... -foam.aspx

http://www.buildingscience.com/document ... er-roofing

http://www.buildingscience.com/document ... of-systems

http://www.buildingscience.com/document ... m=unvented roof

http://www.greenbuildingadvisor.com/gre ... losed-cell
http://www.greenbuildingadvisor.com/blo ... -sheathing

http://www.buildingscience.com/document ... oof-design
http://www.buildingscience.com/document ... -sheathing

[ataloss]

Can you just use spray foam and wood to keep heat from leaking into the attic from around the column? That part would seem like a diy project.

Can you move the ducts to conditioned space i.e. second floor? (not diy)

Here is a picture from energy.gov about insulating attic ducts
http://energy.gov/energysaver/articles/tips-air-ducts

and another explaining why you insulate the attic floor and not the rafters
http://www.michiganenergyoptions.org/co ... ate-attics

[Summit111]

I live in New Orleans in a raised home. Several years ago, I had 4" of closed cell foam applied to the back side if the roof In the attic and the underside of the floor. Sealed the attic completely. This made a huge diffence in comfort and air quality.

My roof is a Galvalume Metal type so no warranty issues...best improvement I've ever done to my house...

Summit

[danwhite77]

BillyG, thanks very much for all of that information, that's extremely useful!

[killjoy2012]

It's probably not what you want to hear, but your HVAC lines have no business being in the attic in the first place based on your geographical location. Moving them would be the right fix, but you're probably not going to like that cost estimate. Closed cell spray foam is good stuff, but not cheap, and I would certainly have an engineer confirm your plans are feasible. e.g. If you spray foam the underside of the roof, what are you going to do about the roof vents, gable vents and soffits? How are you going to circulate the air up there if you're treating it as a conditioned zone, but has no return? Also wondering how much $ you'd be losing operationally per year by heating/cooling that space year-round, vs. moving the HVAC runs and fixing the root cause.

[frugaltype]

I live in New Orleans in a raised home. Several years ago, I had 4" of closed cell foam applied to the back side if the roof In the attic and the underside of the floor. Sealed the attic completely. This made a huge diffence in comfort and air quality.

I had blown in cellulose added to my attic in Calif, obviously a different zone, and it also caused a noticeable increase in comfort.

[frugaltype]

The problem with that approach is that the column leading up to the attic is not airtight. In fact, it's the opposite, there are huge gaps on all sides of the column leading into the attic (all the way up from the basement). Basically it's a large metal duct with 2-6 inches between it and the drywall that surrounds it. So there is a huge amount of uncontrolled heat transfer. I supposed you could block this space off at the bottom and blow in a tremendous amount of insulation into the gap leading all the way from the basement to the attic.

If I'm visualizing this correctly, I'm not sure why you need to insulate the entire area between the column and its enclosing drywall. Maybe the drywall is against an exterior wall and that's causing a heat transfer problem? Otherwise, I would think blocking off the bottom of the gap and the top would be effective for that part of the problem.

[BillyG]

I agree with frugaltype in terms of sealing the air gaps around the main duct that goes to your attic. It is good if you can seal it at the attic as well as down below where it enters the plenum or framed-in space made for it. If any of this space is adjacent to a chimney you will need to deal with fire code issues and seal the space around the chimney with metal flashing and adhesives approved for that purpose.

If you do spray foam on the bottom of your roof correctly it will act as a "cap" on your house so air leakage into your attic from conditioned spaces will suddenly not be as big of a deal. However, you will want to make sure foamers block air paths from inside the wall cavities (especially on exterior walls) into the attic.

I forgot to mention that you want to be absolutely sure your roof is in good shape before you spray foam under the roof sheathing. If there's a roof leak you may not notice it because of the foam, and if you do it can be very difficult to determine where the leak originated. That's one of my fears, so far no problems. I had about six inches of closed cell foam sprayed under my roof and I wish I had done a little more... The house is incredibly comfortable because of all the insulation we added during a major renovation to the roof, walls, under the slab, and to foundation walls.

Another poster mentioned roof vents -- if your house has operational soffit and ridge vents I think you should keep the ventilation and spray foam over (actually under) this system. Blocking will need to be added to protect the integrity of the ventilation system (i.e., you don't want to clog up the soffit or ridge vents with foam) and still obtain the insulation value of the spray foam.

You will learn a lot from the estimators, and take your time and consider your options before you make the decision. It is great you are giving this a lot of thought now.

Good luck with your project.

Billy

[4nursebee]

There are lots of homes with HVAC ducts in the attic. The insulation is generally minimal, I recall new install in my house as R-4. I asked about it, the logic was the air is moving in the duct for brief periods and the losses only happen at start of air handler cycle. I'd focus on sealing connections. Or flat out replace the ducts with new if the insulation is torn. It could be DIY but I would hire out to get better sealing.

In my area we can get a free energy audit from the power company. A serious geek comes out for quite a while. Expanding foam insulation a good idea IF you condition the envelope it is in (this is what I recall). Sounds like you are not going to condition the attic. Others have pointed out good ideas as to why else this is not a good idea-mositure, costs etc... TALK TO SUCH A PERSON if they exist.

What is the purpose of the rehab? There are different solutions based upon what the place would be used for.

Do you know the energy costs for house as it is? Can the insulation problem be fixed later after knowing the place better?

I would favor DIY or hired out blown in cellulose using caution near high heat lighting.

How is the condition of your roof? Roofing ages faster in poor attic conditions.

[HoosierJim]

As a side note - you may want to consider adding ductwork dampers so you can turn on off rooms. Saw this on This Old House the other day.

http://www.thisoldhouse.com/toh/video/0 ... 32,00.html


https://customer.honeywell.com/en-US/Pa ... th=1.3.3.4

[Stonebr]

Dan,

I had this done in our home, built around 1940 in the DC area. I researched it a lot and read hundreds of articles and exchanged correspondence with building scientists and spray foam experts because I wanted to get it right. I have to say there is a lot of misinformation or more likely misunderstanding in the answers you've received so far.

Below I have some links to articles you can read.

You are correct that placing the insulation under your roof so the thermal envelope encloses the HVAC system can be a very good thing.

One of the huge benefits of spray foam is it also creates an air barrier, which is to some extent more important than the insulation value. If you insulate your house and leave a window open you will use a lot of energy and be uncomfortable. Likewise, many people insulate their homes and don't seal the air leaks so they get the same result. You get a lot of bang for your buck by air sealing your house to the extent possible without tearing open your walls (even better if you are opening the walls).

IF you decide to use spray foam under the roof you absolutely need to use closed cell foam unless you also have a vented roof assembly that allows moisture to escape. Do not let them talk you into using open cell foam. Open cell foam is vapor permeable and water vapor can pass through it and condense on the underside of cold roof sheathing. Closed cell foam is vapor impermeable so you will not have this problem is you spray at least 2-3 inches of closed cell foam; to meet the necessary insulation requirements in Chicago I would tend to think 4-6 inches would be much better and probably required by code. The details of how and where they spray the foam are critical to a good quality job. Don't let them spray foam in freezing weather -- above 50 degrees is better.

You do want to foam the rafters to reduce thermal bridging (wood is R1 per inch).

Don't plan on being in your house for at least a few days after they spray the foam. The fumes are bad and you want to give it time to cure.

Get a few quotes and ask lots of questions of the estimators. They usually know a lot about he process and will offer suggestions on the best approach. Above all the company you choose should be very competent. If they screw up the spray foam installation it can be a real mess. While rare, it can happen with inexperienced installers or poor equipment.

Good luck and check out the links below.

Billy

http://www.finehomebuilding.com/assets/ ... -sheet.pdf
http://www.finehomebuilding.com/tool-gu ... -foam.aspx

http://www.buildingscience.com/document ... er-roofing

http://www.buildingscience.com/document ... of-systems

http://www.buildingscience.com/document ... m=unvented roof

http://www.greenbuildingadvisor.com/gre ... losed-cell
http://www.greenbuildingadvisor.com/blo ... -sheathing

http://www.buildingscience.com/document ... oof-design
http://www.buildingscience.com/document ... -sheathing

+1 This is the only answer in this thread that you need to read.

[danwhite77]

It's probably not what you want to hear, but your HVAC lines have no business being in the attic in the first place based on your geographical location. Moving them would be the right fix, but you're probably not going to like that cost estimate.

You are correct, but in 1967 no one cared about energy costs so that's where they are (for our house and millions of others). Moving the ducts simply is not a workable solution, the house effectively would need to be rebuilt. I would be better off moving or leveling our current house and building new.

[danwhite77]

I live in New Orleans in a raised home. Several years ago, I had 4" of closed cell foam applied to the back side if the roof In the attic and the underside of the floor. Sealed the attic completely. This made a huge diffence in comfort and air quality.

I had blown in cellulose added to my attic in Calif, obviously a different zone, and it also caused a noticeable increase in comfort.

I should have more fully described why blow-in insulation really isn't an option for me. The duct work in the attic is approximately two feet above the floor of the attic, and the main conduits are large. For me to effectively insulate the attic using blow-in insulation, I would need to pile about three feet of insulation on the floor to cover over the ducts. The duct wraps that are currently on the market have minimal R value and many sites warn against wrapping too much insulation around the ducts because condensation can build up, resulting in mold. I just don't see how blowing in several feet of blow-in insulation would be a workable solution. If I didn't have the duct work up there, I would be in complete agreement with you all, but unfortunately the duct work makes the solution much more difficult than simply layering in additional insulation.

[Qtman]

I renovated a small house 2years ago and foamed the entire thing. It's like living in a cooler, heat and ac run but infrequently. Cost is higher than fiberglass etc, but no comparison on efficiency.

[Onyxmeth]

I live in New Orleans in a raised home. Several years ago, I had 4" of closed cell foam applied to the back side if the roof In the attic and the underside of the floor. Sealed the attic completely. This made a huge diffence in comfort and air quality.

I had blown in cellulose added to my attic in Calif, obviously a different zone, and it also caused a noticeable increase in comfort.

I should have more fully described why blow-in insulation really isn't an option for me. The duct work in the attic is approximately two feet above the floor of the attic, and the main conduits are large. For me to effectively insulate the attic using blow-in insulation, I would need to pile about three feet of insulation on the floor to cover over the ducts. The duct wraps that are currently on the market have minimal R value and many sites warn against wrapping too much insulation around the ducts because condensation can build up, resulting in mold. I just don't see how blowing in several feet of blow-in insulation would be a workable solution. If I didn't have the duct work up there, I would be in complete agreement with you all, but unfortunately the duct work makes the solution much more difficult than simply layering in additional insulation.

I just meant between the joists. Use duct wrap insulation for the ducts themselves.

[Bengineer]

OP, a couple thoughts. I am in the conventional seal the envelope and ducts, then add duct & ceiling insulation camp.

You mentioned low pitch - If you do go with foam, it will be difficult for the foam contractor to get to the outside walls, seal up your vents, etc. Foaming also involves some skill, the right temps during application etc. to get your full moneys worth. BillyG provided a great note & reference links. I too worry about condensation in your roof sheathing once it's foamed.

If you do go the conventional route, I get how much fun being tall and leaving hunks of your scalp hanging from the roofing nails in the attic is. You should be able to find contractors to seal your attic floor & ducts & / or install insulation.

You might consider getting an energy audit so you have a known baseline and then another blower door test again after so you have a known / agreed-upon amount of improvement to hold your contractors to. The blower door measurements might be folded into your sealing contract.

Good luck with either choice. Let us know how it goes! I for one will be very interested in the outcome.

Edit: Re new pix posted.

Oooh! Attic porn!

The roof pitch doesn't look too bad, you(r contractor) should be able to get out to the eaves. Not fun, but possible.

Your ductwork: It looks like you've got a quality duct system - hard rectangular trunk, short, straight hard branch runs. By hard, I mean metal pipe, which is durable and efficient in terms of airflow. It's wrapped with insulation /vapor barrier, which is good. From here, you could have the wrap taken off, ducts sealed with mastic (might already be done, you could look at the furnace main ducts or pull back the insulation at a branch where it comes off the main or register and look at the joints.) and then a higher r-value insulating wrap added. My take? Get the ducts tested for leakage. it might not be bad at all. Burying or wrapping the existing duct+insulation in vapor-permeable insulation might not be a good idea, as there is potential for condensation during the cooling months when it is hot and humid.

Ice damming could happen even after you seal and insulate - freeze-thaw cycles, sunny days, rain after snow, buildup at the gutters. You may currently have warm air rising up your exterior walls and out just under the wet area you showed. Some things to think about. An article on creating a conditioned attic at GBA with some discussion of foaming the underside of the roof deck. Warning: GBA could become nearly as addictive as this forum for those building/remodeling/insulating. My question/concern is if the foam is applied to the underside of the decking how does it dry out if there are ice dams? How do you find leaks or replace decking if there is rot? Bottom line, I think I'd want to understand the established foaming practice in your climate and see some examples, preferably several years old.

Edit 2: Link to org dedicated to getting the ducts inside the conditioned space: Ductsinside.org

[enc0re]

Another vote for blown in cellulose. It's what I used for my Michigan attic in 2007. It was cheap and effective. Two tips:

1. I used contractors and got three quotes. There was a 3x (!) spread between the low and high cost one for the same amount of cellulose. Get a couple of quotes if you will use contractors. The cheap guys I used showed up with two people, an old pickup, a machine rented from Home Depot, and cellulose. Just the way I like it. Have them tape measuring tape on a post so that you can verify the agreed upon installation depth. They were good people and did it on their own and explained to me why I want that. Would have never thought of it myself.

2. If you DIY, don't forget you need something to cover your soffits so that they don't become clogged.

[ataloss]

The pictures help. It looks tough. I wouldn't want you to level the house but if there is a central duct rising from the basement to the attic I was thinking that there might be a way to tap in to it in multiple spots on the first and second floor to have short runs of vents to living areas, abandoning the original ducts. Maybe a contractor has done this? Sealing and insulating the attic ducts might be the best you can do. I think R6 to R11 per energy star.

http://www.energystar.gov/ia/home_impro ... S_2005.pdf

although all ducts leak, attic leaks result in more energy loss

http://apps1.eere.energy.gov/buildings/ ... ystems.pdf

[runner9]

(for anyone following an update e-mail who's confused like I was: photos are in the first post at the top)

[BillyG]

Dan,

I'm a little concerned about the water stain near the gutter. When you had the roof re-done did they use something like Grace Ice & Water Shield as a peel and stick membrane along all the eaves and at the gables before they installed the shingles?

Ice dams are generally caused by heat under the roof sheathing melting the snow.

Do your gutters have screens on them?

Do you have soffit vents or just the mushroom vents on the roof?

Billy

[danwhite77]

When you had the roof re-done did they use something like Grace Ice & Water Shield as a peel and stick membrane along all the eaves and at the gables before they installed the shingles?

Regarding your first question, I do have a full winterguard system, including extra underlayments near the gutters. That side of the house is east facing, under a large tree, and due to a miscommunication between my wife and I the gutter (which was undoubtedly full of leaves) wasn't cleaned out this fall. So it was really the combination of a number of factors. I'm weighing whether to go back to the roofer or pin this one on myself.

Ice dams are generally caused by heat under the roof sheathing melting the snow.
Do your gutters have screens on them?

No.

Do you have soffit vents or just the mushroom vents on the roof?

We have soffit and mushroom vents. When the roofer removed the decking, he removed any of the insulation from the soffit vents so ventilation should be adequate. Or at least as intended.

I should add that my icicle (heat loss) issues are not unique in my neighborhood that is filled with similar vintage and design houses.

[danwhite77]

The pictures help. It looks tough. I wouldn't want you to level the house but if there is a central duct rising from the basement to the attic I was thinking that there might be a way to tap in to it in multiple spots on the first and second floor to have short runs of vents to living areas, abandoning the original ducts. Maybe a contractor has done this? Sealing and insulating the attic ducts might be the best you can do. I think R6 to R11 per energy star.

I've thought about leveling the house once or twice!

I don't think moving ducts is an option. Honestly, even if the second floor joists are running in a manner that makes it theoretically possible, the cost would dwarf any economic benefit. And I'm 99.9% certain the joists are running in a manner that would make it impossible, even in theory, to move the duct work. I'd move before I'd undertake that type of project.

[gordons1]

After spraying in a foot or two of insulation, purchase and install Radiant Reflective Barrier from a company in Arlington Texas....Innovative Insulation (google that name). This will contain the heat in the winter and air conditioning in the summer time....study their web site for ways to install; it will give you a 1-2 year payback (double the value of your blow-in insulation). This product was invented as a heat shield for the space capsules by NASA.

[likegarden]

I live in a 2 story house in upstate NY, minimum winter temperatures are -20 degrees. I just had installed central AC in the attic. (We have hot water baseboard heat with the furnace in the basement.) Our attic is also not occupied. I have never heard of insulating the plywood and rafters under the roof. Our area houses have very well insulated attic floors with ventilated attics to reduce heat loss and damage by moisture. All houses here have ridge and soffit vents. Shingles on our roofs last 25 years and longer.

When you insulate directly under the roof of the house and keep heat in the attic by that, any snow would be melted off the roof, ice and ice dams will be created, not what a roof and house are built for.

Reading some of the answers, I would ask the utility to do an energy audit with their people giving you some basic advice before you blow in foam onto the attic ceiling. Also note that heating and AC installing companies, not the foam blowing contractor, in my area also installs or improves insulation and could give you independent advice.

[jimb_fromATL]

Dan, the stuff I posted was what I learned from a lot of research some years ago. Among other things I learned as somebody else posted is that if you have sprayed the foam insulation under the roof decking, manufacturers will not warrant their shingles because the trapped heat reduces their life. Several builders and roofing contractors told me the same thing. It stands to reason that they'd prefer to make a sale if they didn't have awfully good reasons to know that it does shorten the life of the roofing, so I tend to believe them more than a salesman's promise.

If you dig deep at those linked sites that somebody else posted, you'll find discussions there about concerns about moisture and humidity in the attic if you spray under the roof decking. As you do more web searching I think you'll eventually notice that virtually the only people who ignore the problems with moisture control – and minimize it or sometimes outright lie about it-- are the people who manufacture, sell or install the sprayed foam.

Some of those manufacturers don't really push it for the roof decking, but some ignore the reality that water can get into the roof decking but not get back out or evaporate if the underside is many inches of water-proof foam. I even found one sales-oriented site that stated that there is no proof that it has ever happened ... or words to that effect. Seems to me that common sense and logic would suggest that if water gets into the roof decking and rafters from leaks or backup from ice dams, that if there's no ventilation and no way for it to leak through or to get enough air to evaporate quickly, mold will form and the wood will evenually rot.

You might also do some web searching about attic ventilation, soffit and ridge vents, etc that also discuss the problems of NOT venting an attic.

Ours is a very steep roof hip roof ... about a 9 in 12 pitch. When we re-roofed (and redecked) our late 70's house we added Hardee plank ventilated soffit and a ridge vent as well as some additional mushroom vents because the hip roof ridge was not very long. Now that there is a lot more vent area, it is in the range of 15-20 degrees or more cooler in the attic in the summer, and has greatly reduced our cooling bill. (Heating is not normally as big a problem in the south -- though it did get below zero here for the first time in 30+ years or so this winter.)

Here are some excerpts from those links… where there are also a lot of cautions and warnings.

http://allinoneinsulation.com/2012/02/b ... nsulation/

• “…Spraying foam insulation on the underside of the roof sheathing doesn’t help the roof. During the day, as the roof heats up to 160°+ the heat has to go somewhere. Since the conductive insulation is on to the underside of the sheathing, it takes longer for the heat to conduct through the roof so the heat is forced to stay on the roof surface, effectively baking the shingles. Shingles are made of asphalt-based products and, because of the consistently high temperatures, the oils begin to break down and evaporate and the shingles lose their integrity sooner than normal…”
  
  “…If the plans call for a conditioned attic, confirm that your local building official allows unvented attics…”
  
  “…Many green builders avoid the use of closed-cell spray foam because…”

http://www.finehomebuilding.com/how-to/ ... hutes.aspx

http://www.buildingscience.com/document ... of-systems

• “…The primary concern with the use of unvented roofs is the potential for moisture build up at the
  underside of the roof sheathing during cold weather. Rain leaks are just as dangerous. Research has
  shown that the good field experience with ventilated attics is due to the removal of moisture that
  passes through the ceiling plane by diffusion and accidental air leaks…”

http://www.greenbuildingadvisor.com/gre ... losed-cell

http://www.greenbuildingadvisor.com/blo ... -sheathing

• “…The researchers concluded, “The most important retrofit option, whether the duct system is in the attic or not, is to seal the attic floor.” They also advise, “For new construction the best option is to keep the ducts out of the attic, make sure the attic floor is sealed to limit whole-house air leakage, and add at least the code level of insulation to the ceiling…”

http://www.greenbuildingadvisor.com/gre ... losed-cell

Response to Bob Rinehuls
by Martin Holladay, GBA Advisor

Q. "Is there any concern about moisture accumulation between the foam and the roof deck, say, if the roof leaked?"

A. Yes, many builders and homeowners have expressed that concern. If you want to be able to inspect the roof sheathing for possible roof leaks, it's best to design either an unconditioned attic, or a conditioned attic with all of the insulation located above the roof sheathing.

More excerpts gleaned from those links:

• “…but filling a 2x4 cavity to R-13 with closed cell spray foam costs about $1.75 to $3 per sq. ft…”
  
  “…
  CLOSED-CELL FOAM
  
  “Two-pound foam, also known as closed-cell foam, has a density of about 2 lb. per cubic foot and an R-value of 6 to 6.5 per inch. Two-pound foam is significantly more expensive than half-pound foam…”

So you need to hink about this: If it takes 4” to get R-13 and you need in the range of R42 or better, that’s a lot more foam … and a lot more money.

Something else I don’t see anybody mentioning is the simple geometry and math about how much area you have to cover. Don’t overlook that not only is the foam a lot more expensive, but you’ll also need in the range fo 1.25 to 1.5 times more of than on the ceiling rafters it because each section of the roof surface is essentially the longest side – the hypotenuse of a right triangle. IF your attic is gabled rather than a hip roof, even more insulation is required for the gables.

So ... not only does it stand a good chance of causing mold and rotting out your roof sheathing where you won’t even know it until the roof decking starts buckling or caving in because it doesn’t show from the underside, it’s going to cost an arm-and-leg more than blown in cellulose or blown fiberglas or fiberglas batts. I didn't notice any of the sales sites or foam advocates mentioning that. I guess it was just an oversight. Ya think?

About the ducts:

From the looks of it, those are all supply ducts. Chances if you have adequate ventilation, there won't be sweating if they are insulated better.

Something you might want to look into with the help of somebody in the HVAC business is whether you have enough return air ducts.

Ours has supply ducts in the attic. However a couple of the bedrooms did not have return ducts, but depended on a central return in the upstairs hall. Thus they didn't heat or cool as well when the doors were closed. One thing we added when we upgraed our HVAC system was some additional return ducts so that all rooms got good circulation even with the doors closed ... which made the rooms considerably more comfortable, especially for guests who could have more privacy without being too hot or too cool.

By the way, that brings up another consideration, which is whether you have bathroom exhaust fans that exit into the attic instead of to outside. If they exhaust moist air into the attic, all the more reason you need a lot of attic ventilation. If you were to seal the attic, you'd need to have the bathroom vents go the outside. The problem is that then you'd have a direct pipe for ouside air to your bathroom -- which sort of defeats the purpose of super-insulating.

As for the central supply from downstairs, IMO all you really need to do is close off/insulate the opening where it comes thought the ceiling into the attic. The heated or cooled air in the shaft inside the house is not really being lost, since the loss is through the walls into the living area.

I think the main thing worth repeating is this ... from one of the links above.

• “…The researchers concluded, “The most important retrofit option, whether the duct system is in the attic or not, is to seal the attic floor.” They also advise, “For new construction the best option is to keep the ducts out of the attic, make sure the attic floor is sealed to limit whole-house air leakage, and add at least the code level of insulation to the ceiling…”

Good luck in your decision making process. Let us know what you decide.

jimb

[WhyNotUs]

I really like JimB's comments. I am not an expert but would be in the seal and cellulose camp. Looking at your duct work made me think about ripping some 1//4 inch ply and using 1" cross-bracing to build a form around the main duct to fill with cellulose and bury the distribution ducts. That would be something that a homeowner could do.

Only used foam insulation once, open cell in a very confined steel roof system. Used open cell for sound isolation as the site was next to a highway. Given the design, there were not other options or I would not have used it due to off-gassing concerns. This was about 10 years ago so prices have changed but it was ridiculously expensive back then.
One of the things that I like about cellulose is that one leaves their choices open for the future, foam locks one in. I have an affinity for cold roofs that biases my perspective but I think that they have proven to be a good idea in most situations as it gives me more options to deal with ventilation and air exchange in the future.

I am sure that after all of the homework that you are doing, you will make a good decision regardless of the choice.

[likegarden]

I do not know if problems in the 1970s with foam (formaldehyde) installations occasionally are still occuring. Then we had to rip out the foam insulation and sheet rock of our bedroom outside walls, because they were supposedly gasing out and could have made us sick. I would ask for a reference list from foam contractors and check with their former customers.

[BillyG]

likegarden, polyurethane foam is different from the foam used in the 1960s. No formaldehyde.

JimB, closed cell foam does not have the moisture issue under a roof; open cell foam does. You have to consider where is the air barrier, where is the insulation, and where is the vapor barrier, if any.

It is best to have a vented roof assembly if possible, with insulation below it. If it is not possible and you have insulation under the roof, closed cell foam is the next best because it provides a vapor barrier, among other things.

There are unscrupulous foam contractors who will spray open cell foam under a roof without providing an vapor barrier.

Billy

[danwhite77]

EPILOGUE:

Thanks to everyone who weighed in on the spray foam v. blow-in insulation question that I posted here. Ultimately, last fall (2014) I had blow-in insulation installed (R49 total) and had R19 insulation batts draped over the duct work in the attic. Now that we're well into a winter that is comparable to the 2013-2014 winter here in Chicago, I have a pretty good apples-to-apples comparison. So far, our gas usage has gone down by about a third. Also, more importantly, the second floor is very warm and comfortable. Last winter we would freeze upstairs because all the heat went directly to the attic. So basically, the blow-in solution has had the desired effect.

I probably would have gone with spray foam insulation, but I could not find a retrofit installer that I trusted to use (what I believe to be) the right product. And, even if I could, using the correct product would've cost about three or four times what I paid for blow-in insulation, and at that price point it didn't make sense in my situation.

So again, thanks everyone. Stay warm out there!

[Carson]

Thanks for the update! I am in Chicago too and know we need to do *something* about our attic, but I really don't know what. Plus we store all kinds of junk up there. Appreciate you posting how the solution has worked for you.

[zadie]

We had open cell foam done in our attic 2 years ago. A few weeks after the install the entire house started smelling like chemicals. They had to come back and rip everything out, by hand. Took 5 guys 5 days. Brutal. I would never do form in a retrofit again. Luckily the installer stood by their work and took care of it, but there are horror stories out theor about the same thing.

[Cosmo]

Not to discourage your hard work and efforts thus far, I noticed your comment in your OP above about this winter being an "apples to apples" comparison to last winter. The winter of 2014/2015 is not anywhere close to how cold the prior year was in the Chicago area:

Here are some stats for Chicago

Mean temperature relative to the standard 30 year normal at ORD:

Dec 2013 Dec 2014
-4F +4.8F

Jan 2014 Jan 2015
-8.1F -1.5F

Feb 2014 Feb 2015
-10.4F -7.2F

While the present month is giving Feb 2014 a run for its money, Dec-Jan of this winter is 9-10F degrees warmer than the prior winter in the Chicago area. That is huge. Now for the poor folks who live in Boston. Hands down; this winter much colder than the prior winter.

Cosmo

[danwhite77]

Gotta love it on Bogleheads when an 8 degree Fahrenheit difference turns a comparison into apples and oranges! Remember, we're not talking about expense ratios here!

These are the temperatures Nicor provided on our bill for the following months:

NOV
2013: 39
2014: 46
DEC
2013: 26
2014: 35
JAN
2014: 20
2015: 25
FEB
2014: 13
2015: 26

We would have to make a lot more adjustments for apples to apples - specifically my wife seems to like to leave gas burners on the stove and grill on from time to time! Also, my kids like to open doors and stand in the doorway talking to other kids outside. Actually, now that I think of it, my kids (and furnace) are probably the reason this winter has been warmer!

[BillyG]

Dan,

Congratulations on the great results! It's good to see the extra insulation and your insulation approach are for you. The added comfort is a really big plus that doesn't always show up in the numbers, but it keeps everyone happy at home.

Billy

[BillyG]

We had open cell foam done in our attic 2 years ago. A few weeks after the install the entire house started smelling like chemicals. They had to come back and rip everything out, by hand. Took 5 guys 5 days. Brutal. I would never do form in a retrofit again. Luckily the installer stood by their work and took care of it, but there are horror stories out there about the same thing.

This sounds like a terrible experience. The fact they used open cell foam in your attic means they didn't really know what they were doing, unless this was a vented roof. What time of year did they spray the foam?

It is good they stood behind their work, as there are worse stories about installers doing a poor install and then not standing behind their work.

Billy

[zadie]

Billy, they did it late spring. Awful experience. The installers blamed it on the foam and the foam manufacturer blamed the installers. Thank god that the installers took care of it. when they removed the foam, it filed up 4 box trucks. There are horror stories online, about this and nobody taking responsibility and the homeowners have to move out b/c of the smell. Also bad stories using closed cell foam as well. One I came across, the homeowners had to have their roof removed and rebuilt, b/c you can't remove the closed cell foam. I would caution anyone who is considering the foam for a retrofit.

[Cosmo]

Gotta love it on Bogleheads when an 8 degree Fahrenheit difference turns a comparison into apples and oranges! Remember, we're not talking about expense ratios here!

These are the temperatures Nicor provided on our bill for the following months:

NOV
2013: 39
2014: 46
DEC
2013: 26
2014: 35
JAN
2014: 20
2015: 25
FEB
2014: 13
2015: 26

We would have to make a lot more adjustments for apples to apples - specifically my wife seems to like to leave gas burners on the stove and grill on from time to time! Also, my kids like to open doors and stand in the doorway talking to other kids outside. Actually, now that I think of it, my kids (and furnace) are probably the reason this winter has been warmer!

From a heating perspective, a 9-10F degree warmer winter per the Chicago NWS is not trivial and could largely explain why your usage was down by a third. In any case, sounds like a really good move here. On a separate note, have you read the ice dam thread here on this site? Unfortunately, this is a very widespread problem right now in New England and your efforts here likely mitigate the risk for this happening in the event of another super snowy winter in Chicago.

Cosmo