Replace fiberglass insulation with spray foam in a crawlspace?

[A440]

Once or twice a year I enter the bowels of my home and do a cursory inspection in the crawlspace. I check the foundation for evidence of mudtubes, check plumbing connections for any signs of leaks, and anything possibly making a home in the crawlspace
I also push up and secure fiberglass insulating that has fallen out of floor joists with 16" wire supports. I've lived in the home for 30 years. My neighbors adjacent to me have the same type home and no insulation in the crawl. I have the insulation and 10 mil plastic vapor barrier over the very rough concrete floor.
I was wondering if other Boglehead crawlspace owners have ever replaced the fiberglass insulation with spray foam, and what (if any) the benefit might be.

[lthenderson]

The benefits are better insulative value and less food and habitat for insects and critters. Probably the two drawbacks are cost and that it makes it harder to work on any wiring, plumbing or HVAC within the floor joists.

[newtoseattle]

We did this and the main benefit was it sealed up small air gaps in the floor ("car deck"). In my research it seems it is very dependent on where in the country you live. In most of the country there is a strong recommendation to "encapsulate" the crawl space (ie seal up and insulate the walls of the crawl space and not the floor joists). In the PNW that is not the case and continuing with floor joist insulation seemed reasonable.

[Tundrama]

Do plenty of due diligence and not necessarily here.

When done properly, spay foam is excellent.

Done wrong, or over moist materials or where there is moisture potential between the wood and spray foam…that’s a no go.

Good luck.

[elcadarj]

I had problems with damp insulation in our crawlspace which made the first floor of our house smell musty. Turns out the ventilated crawlspace isn't suited to the climate here in the Piedmont Carolinas. We had our crawlspace insulated and encapsulated. Foam board insulation was attached to the block walls, the fiberglass insulation between the floor joists was removed, and the ground and walls were sealed with a thick membrane. One of the best home improvements we've done. Saved energy and improved the comfort of the house, winter and summer. I did my research here: https://www.energystar.gov/saveathome/s ... crawlspace.

[A440]

I have a PSE&G Home Energy Audit scheduled for next week. It will be interesting to see what is suggested.

[A440]

I was also reading another thread that mentioned a couple things: 1) if it ain't broke, don't fix it and 2) changing the design of the crawlspace of a home built in the 50's may make things worse.

For the past 30 years, we haven't had any health issues relating to mold or mildew. No one has every had asthma or year round allergies. Never had any smells from the crawlspace. I close the vents during the heating season and open them every spring. Water has only been an issue if we get a spring nor'easter. The temperature never gets below 50 degrees. We might catch a mouse or two in the attic in the winter months. However, we did not have any this past winter. I think they've caught on that a dog has taken up residence.

[HaveaNiceDay]

Just a thing to watch for, if you seal/encapsulate the crawl space, you might want to do a Radon check because you have modified the venting from the crawl space. The people I know who have encapsulated the crawl space also spend another 1K to add a radon system due to the higher readings after sealing.

[TT]

delete

[Normchad]

It’s a bit confusing, and there are conflicting opinions of what to do. Sounds like there are also lots of charlatans out there that will take your money and cause you new problems.

I have moved into a home built in 20008 that has a crawl space. This is a first for me, so I’m trying to figure it out as well.

A big part of me thinks this. Hey OP, you’ve had this system for 30 years without issues. Just leave it be? OTOH, I am drawn to the idea of “doing something”.

If you want to call down a rabbit hole, look on YouTube for videos from “crawl space ninja”. Very good stuff…..

I guess my biggest concern is this. The water supply pipes are in the crawl space, and are not insulated at all. A few nights a year, the temps will drop below 32 and stay there for 6+ hours. So I worry about that…..

[A440]

It’s a bit confusing, and there are conflicting opinions of what to do. Sounds like there are also lots of charlatans out there that will take your money and cause you new problems.

I have moved into a home built in 20008 that has a crawl space. This is a first for me, so I’m trying to figure it out as well.

A big part of me thinks this. Hey OP, you’ve had this system for 30 years without issues. Just leave it be? OTOH, I am drawn to the idea of “doing something”.

If you want to call down a rabbit hole, look on YouTube for videos from “crawl space ninja”. Very good stuff…..

I guess my biggest concern is this. The water supply pipes are in the crawl space, and are not insulated at all. A few nights a year, the temps will drop below 32 and stay there for 6+ hours. So I worry about that…..

Well...I went down the rabbit hole and watched lots of YouTube videos. I'm even more flumoxed now whether or not my crawlspace vents should be sealed or not. The builders of the home in the 50's must have felt that having vents for the crawlspace was important. Even a recent addition in early 2000's had closeable vents installed in the foundation block and R-19 (faced) installed between the floor joists.
We get humidity here in NJ, so I can see the reasoning for keeping the vents sealed so humid air doesn't create moisture in the crawlspace. OTOH, having them open provides for air movement to aid in keeping the space dry. We have a downflow system, so the space never gets below 45 degrees at best in the winter and probably in the 50's to low 60's in the summer. The ducts are insulated, but I'm sure not air tight. I'm okay with that because it keeps the space warm enough to avoid frozen pipes.

[flarf]

https://buildingscience.com/documents/b ... her-or-out

I'd take advice from them, not whoever decides to upload a video to Youtube.

[Saving$]

1. Make sure that your crawlspace stays dry. If there are sources of moisture, remediate.
Once you have done what is needed to prevent water from entering the crawl:
2. Seal the crawl. This is done by blocking the vents, doing massive air sealing, putting plastic on the ground and then insulation the perimeter walls of the crawlspace. The crawlspace air then communicates with the house so it become somewhat conditioned.
3. At that point you will not have or need insulation on the underside of the floor/in the ceiling of the crawl. Remove it.

A sealed conditioned crawl may mean you need to install a radon mitigation system, and /or a dehumidifier in the crawl.

The advantages are healthier indoor air and dramatically increased comfort. Your crawl is now close to the temperature of your house, so the floor is never cold in the winter and drafts are reduced or eliminated.

The comments above about spray foam are correct. It can have issues.

Read more about all of this at www.buildingscience.com, as noted by another poster.

[A440]

1. Make sure that your crawlspace stays dry. If there are sources of moisture, remediate.
Once you have done what is needed to prevent water from entering the crawl:
2. Seal the crawl. This is done by blocking the vents, doing massive air sealing, putting plastic on the ground and then insulation the perimeter walls of the crawlspace. The crawlspace air then communicates with the house so it become somewhat conditioned.
3. At that point you will not have or need insulation on the underside of the floor/in the ceiling of the crawl. Remove it.

A sealed conditioned crawl may mean you need to install a radon mitigation system, and /or a dehumidifier in the crawl.

The advantages are healthier indoor air and dramatically increased comfort. Your crawl is now close to the temperature of your house, so the floor is never cold in the winter and drafts are reduced or eliminated.

The comments above about spray foam are correct. It can have issues.

Read more about all of this at www.buildingscience.com, as noted by another poster.

I'm purchasing an Airthings Wave Radon detector today. In addition to constantly monitoring radon, it provides humidity and temperature. It works via bluetooth with your smartphone. I plan to place it in the crawlspace and monitor what is happening on a month to month basis.

[ShaftoesSpreadsheet]

I looked into this as our home has has no floor insulation. Spray foam is VERY expensive compared to batts. The benefit is it has a higher R value per inch and can act as an air sealer as other have mentioned. Either way, the utility savings of adding floor insulation would never pay for itself in our case. I wear Birkenstocks inside so I don't feel the cold floor in the winter.

Even if spray foam was cheaper or penciled out, we would never go with it for health risk reasons. The spray foam sales pitch included a disclaimer that we have to vacate the home for 24 hours due to off gassing. In other words the stuff is TOXIC. Given my understanding of chemistry and the nature of reaction rates, probably much longer. Yes it binds and becomes largely inert, but why 24 hours, not 12 or 48? It is an arbitrary estimate. We avoid memory foam mattresses for the same reason. I don't have a study to back any of this up, it is an opinion from a rando on the internet, but better safe than sorry. Most chemicals in our environment were invented in the last 30 years and the health effects are poorly understood. We are all guinea pigs. And if you want to agitate your amygdala even more, if it is sprayed incorrectly it can heat up and cause a fire.

[ShaftoesSpreadsheet]

It’s a bit confusing, and there are conflicting opinions of what to do. Sounds like there are also lots of charlatans out there that will take your money and cause you new problems.

EXACTLY! Many topics are like this when it comes to big ticket items (crawl space insulation, solar panels, fancy "alternative" investments, annuities, etc). When I see this kind of situation, my gut tells me to stay away from it. Better option is to go with something less complex and time tested.

[carolinaman]

I guess my biggest concern is this. The water supply pipes are in the crawl space, and are not insulated at all. A few nights a year, the temps will drop below 32 and stay there for 6+ hours. So I worry about that…..

We have a ranch home with crawl space in NC. Our pipes are in crawl and have never frozen in 50 years. Our climate is moderate but we have cold snaps where temp was in single digits for several days. One time, we lost electricity in ice storms for days, and despite the very cold temp, our pipes did not freeze. At that time, we had well water which was not working either, so there was no running water. I was surprised that our pipes did not freeze that time, but we were blessed.

BTW, we finally encapsulated our crawl space 5 years ago. They used thick poly on ground, rigid foam boards on outer walls and piers, and fiber glass in floor joists. Also have industrial strength dehumidifier. This was done due to hot, humid summers and excessive moisture during summer. Expensive, but worth it.

[A440]

FWIW, I had a free energy audit performed by my utility company. I asked the person doing the audit for an unbiased opinion of the crawlspace. He looked (and smelled) in the space and said he would leave it alone. "If you haven't had any health issues from the crawlspace in the last 30 years (e.g. asthma, allergies) you should be fine."
I still plan to inspect the sills every spring for termites (with a long screwdriver, and look for mudtubes), replace any R19 insulation that has fallen and add metal supports, check for water leaks, inspect wood for any signs of mold.
If I get motivated, I might install an insul-barrier along the foundation walls and maybe put another vapor barrier down on the rough concrete "floor". But, I'd have to be really motivated for the time, effort and expense.

[Watty]

.... a home built in the 50's....

Is there any asbestos down there? If so I would not touch anything I did not have to.

Before you do this one thing to look into is how long your water pipes are expected to last. Copper pipes do not last forever but just how long depends on a lot of factors. My subdivision was built in the 1970s and several houses have had pinhole leaks in copper pipes develop and they have had all their copper pipes replaced with PEX which is a major project.

So far we have been lucky and when we have the bathrooms remodeled later this years all the copper pipes in the bathrooms will be replaced. Other than that almost all our other copper pipes are easily accessible in our unfinished basement.

If you have the spray foam in the crawl space and you need this done you may get bids with the high "we don't want to do it" price.

[A440]

.... a home built in the 50's....

Is there any asbestos down there? If so I would not touch anything I did not have to.

Before you do this one thing to look into is how long your water pipes are expected to last. Copper pipes do not last forever but just how long depends on a lot of factors. My subdivision was built in the 1970s and several houses have had pinhole leaks in copper pipes develop and they have had all their copper pipes replaced with PEX which is a major project.

So far we have been lucky and when we have the bathrooms remodeled later this years all the copper pipes in the bathrooms will be replaced. Other than that almost all our other copper pipes are easily accessible in our unfinished basement.

If you have the spray foam in the crawl space and you need this done you may get bids with the high "we don't want to do it" price.

Good to know. Thanks.

[Valuethinker]

Once or twice a year I enter the bowels of my home and do a cursory inspection in the crawlspace. I check the foundation for evidence of mudtubes, check plumbing connections for any signs of leaks, and anything possibly making a home in the crawlspace
I also push up and secure fiberglass insulating that has fallen out of floor joists with 16" wire supports. I've lived in the home for 30 years. My neighbors adjacent to me have the same type home and no insulation in the crawl. I have the insulation and 10 mil plastic vapor barrier over the very rough concrete floor.
I was wondering if other Boglehead crawlspace owners have ever replaced the fiberglass insulation with spray foam, and what (if any) the benefit might be.

I would not.

For all the reasons of disliking foam as a product. This is something that there is no environmentally safe way of disposal (AFAIK) and someday someone will have to dispose of it.

Also I worry about it being impermeable to water vapour, and you getting condensation on the cold side. Plus having to remove it for whatever reason.

I would repair/ refill the fiberglass insulation. It's not without its problems, but it's a well known material.

The additional insulation from foam would be marginal *unless* you have a home energy audit and they can point to that being a particular issue. Where I could see it might be on the air leak test (if they do one with a blower). But I think you can seal up air holes without using foam.

[Valuethinker]

I looked into this as our home has has no floor insulation. Spray foam is VERY expensive compared to batts. The benefit is it has a higher R value per inch and can act as an air sealer as other have mentioned. Either way, the utility savings of adding floor insulation would never pay for itself in our case. I wear Birkenstocks inside so I don't feel the cold floor in the winter.

Even if spray foam was cheaper or penciled out, we would never go with it for health risk reasons. The spray foam sales pitch included a disclaimer that we have to vacate the home for 24 hours due to off gassing. In other words the stuff is TOXIC. Given my understanding of chemistry and the nature of reaction rates, probably much longer. Yes it binds and becomes largely inert, but why 24 hours, not 12 or 48? It is an arbitrary estimate. We avoid memory foam mattresses for the same reason. I don't have a study to back any of this up, it is an opinion from a rando on the internet, but better safe than sorry. Most chemicals in our environment were invented in the last 30 years and the health effects are poorly understood. We are all guinea pigs. And if you want to agitate your amygdala even more, if it is sprayed incorrectly it can heat up and cause a fire.

I think this is generally true of a lot of chemicals, so you are not crazy. We don't really know if they cause cancer or not. But the issue of endocrine disruption, among its side effects possibly the cause of declining male fertility globally, is a very real one. This isn't internet crank stuff. This is genuine scientific uncertainty and we certainly have not applied the precautionary principle.

In the UK there is special fireproofing required of mattresses and foam in furniture. It appears to cause cancer, at least in firefighters. We are unique in requiring this - it's not some carryover from our time in the EU. But once it's in the legislation, it's very hard to move.

(If you ever follow Maytimber, possibly the world's most popular firefighter account on Insta, Norwegian firefighters now don & remove their protective masks *outside* the vehicle ie not on the way to the fire but when they arrive on site. This is to protect them from carrying cancer-causing residues back into the vehicle cab).

Similarly with the "teflon chemicals" that we are now finding in rainwater. (PFAs? TFAs?)

[firebirdparts]

If you have any thought of doing an encapsulation then put it off. if you do an encapsulation you can convert that to conditioned space and you won't have any humidity issues.

[mariezzz]

Potential issues with spray foam insulation

https://vtdigger.org/2023/05/22/i-wante ... omeowners/

Excellent article.
I've heard bad things about spray foam insulation over time, and this article does a nice job of summarizing many of the problems.

[A440]

Sounds like spray foam is not the way to go.
I have a call into my local building inspector to get the code on vented vs. unvented crawlspace and get another unbiased opinion on whether or not to seal the vents.

[A440]

UPDATE: So after speaking with the building inspector and doing way too much research on crawlspaces in my Southern New Jersey, here is what we decided.
1) Remove the 30 year old moldy, probably mice infested R19 insulation in the floor joists and old saturated board insulation along the foundation walls.
2) Clean up the debris on the old 6 mil vapor barrier and install a new 10 mil vapor barrier over the old and run up the walls and pillars 15" or so.
3) Install 2" polyisio reflective along the foundation walls, allowing 3" gap for termite inspection at the top.
4) Install 2" polyisio "blocks" in the rim board sections and seal with spray foam from a can.
5) Remove fiberglass insulation from the ducts and inspect for leaks. Apply mastic and foil tape where needed.
6) Seal the vents and any entrances for pests.
7) Treat all the wood with Bora-care +Mold if needed.
8) Hang a smart device in the crawlspace to monitor temperature, humidity and radon levels.

Some of this work I will contract out, simply because I don't wish to do it, the rest I will do myself. The cost for the work is ~$6,000.
Unless the humidity levels are above 65% in the summer, I will probably pass on a dehumidifier for the space. I really don't want to deal with changing the filters 1 to 2 x a year and having to install and outlet in the space.
Because we rarely have water in the space, I will pass on the sump pump as well.

It will be interesting to see if the improvements have a positive effect on the humidity levels in the home. Something I will monitor this summer, as we plan for an HVAC upgrade in the fall and decision between 1 and 2 stage cooling.

[RustyShackleford]

UPDATE: So after speaking with the building inspector and doing way too much research on crawlspaces in my Southern New Jersey, here is what we decided

Sounds like an excellent plan. I seriously doubt you're going to be able to get by without a dehumidifer though, and 65% RH is too high.

[buddysam1]

Re the dehumidifier issue - I have a shallow (2-3ft) crawlspace with a fiberglass insulation and a vapor barrier that has many gaps/tears. When I bought the house in 2020 the crawlspace was very damp in the summer. I did a lot of research and just couldn't pull the trigger on foam or encapsulation. I closed all of the vents, cleaned up the insulation and installed a Govee wifi dehumidifier in a spot where I was able to run a hose to the outside for the condensate drain. It's been over a year and the dehumidifier works great. The crawlspace is nice and dry. The app is nice to have. It was a $175 solution.

[TrustingSoul]

OP,
An audit done by professional inspectors is probably going to serve you well. The floor and crawl space might not be the most important issue. The company doing the inspection will tell you where to put your efforts. I wouldn’t say don’t fix it, just make certain it’s the best Bogleheads use of your resources.

[GreenLawn]

Just a thing to watch for, if you seal/encapsulate the crawl space, you might want to do a Radon check because you have modified the venting from the crawl space. The people I know who have encapsulated the crawl space also spend another 1K to add a radon system due to the higher readings after sealing.

All our Crawlspace vents were covered by the encapsulation installer. The radon readings were too high so I installed a vent fan that runs 24/7. Retested for Radon and that did the trick.

[A440]

Re the dehumidifier issue - I have a shallow (2-3ft) crawlspace with a fiberglass insulation and a vapor barrier that has many gaps/tears. When I bought the house in 2020 the crawlspace was very damp in the summer. I did a lot of research and just couldn't pull the trigger on foam or encapsulation. I closed all of the vents, cleaned up the insulation and installed a Govee wifi dehumidifier in a spot where I was able to run a hose to the outside for the condensate drain. It's been over a year and the dehumidifier works great. The crawlspace is nice and dry. The app is nice to have. It was a $175 solution.

I've been looking at putting a dehumidifier next to the high-efficiency furnace that is rated for 1,500 sq ft. I can have it drain into the pump used for the furnace that drains into the laundry sink. It would only be needed in the seasons when the furnace isn't used. Also makes it easy to change the filter.

[A440]

Just a thing to watch for, if you seal/encapsulate the crawl space, you might want to do a Radon check because you have modified the venting from the crawl space. The people I know who have encapsulated the crawl space also spend another 1K to add a radon system due to the higher readings after sealing.

All our Crawlspace vents were covered by the encapsulation installer. The radon readings were too high so I installed a vent fan that runs 24/7. Retested for Radon and that did the trick.

I purchased the AirThings Wave Radon that continuously checks for radon. Also checks temperature and humidity.

[A440]

Does a dehumidifier in the crawl space need its own dedicated circuit?
Can I get away with purchasing one with a pump to drain through the foundation vent (through the foam that seals it)?
How about using a sump pump only when Nor'esters come through, instead of a dedicated one wired with a pvc drain.
I'm thinking I could leave a sump pump in the pit, connected to a garden hose coiled up in the crawl near the entrance. Then just use it if and when it is needed, which is not very often. I have an outlet next to the entrance of the crawl. I could have the power cord near the entrance as well.

[nativenewenglander]

I would recommend visiting Green Building Advisors they are part of Fine Home Building. The site is out of Sheffield VT and run by Martin Holliday they have a forum where you can ask questions and get professional answers. I live in northern NH I used spray foam on our stone foundation up to the floor and followed their advice on insulating our walls and attic. Our 1620 sqft home with the original 125 year old windows uses 80 gallons of heating oil and 1.5 cords of wood to heat. Our carriage house is all spray foam insulated including the crawl space it heats well with no issues.

[A440]

UPDATE: So after speaking with the building inspector and doing way too much research on crawlspaces in my Southern New Jersey, here is what we decided

Sounds like an excellent plan. I seriously doubt you're going to be able to get by without a dehumidifer though, and 65% RH is too high.

You are correct.
Even after encapsulating the space, the R.H. is still close to 80% on really humid days. I ordered a dehumidifier with a built in pump. The unit is sized to cover 1,500 sq. feet, which is more than I need. I'll place it where I can feed the drain hose (16 ft in length) in an area near a foundation vent and continue out about 4 feet from the foundation. I'll also install a GFCI outlet for the dehumidifer and place the unit up on 6" furniture blocks. I can monitor the temp/humidity with the Govee device. I also plan to install a smart plug in the GFCI outlet so I can turn the unit on/off remotely.

[A440]

Winter update:

With the now sealed/encapsulated crawl, I am measuring an average temp of 64 degrees and RH below 50% in the crawl space, it is currently 25% outside. I have the dehumidifier turned off for the winter months as any humidity would be beneficial to the home to offset the drying of our force air heating system.
The radon levels average around 1.0 pCi/L which seems acceptable.
So far the encapsulation seems to be doing what is should.