Author Topic: Anyone condition / insulate their crawl space?  (Read 859 times)

ManyMountains

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Anyone condition / insulate their crawl space?
« on: December 10, 2017, 11:32:48 PM »
Main Q's:
1) Is the best option for a ventilated crawlspace to condition it (ie insulate and vapor barrier to make it "inside" the house)?

2) Has anyone here done this themselves? Any advice on online resources, best materials, etc to help a DIY project?

We are in the process of renovating our house - a 1200 sq ft single-story 1950s home in the SF Bay Area. There is basically no insulation in the house, which is pretty standard for houses and apartments here built in the 50s and 60s.

We had our wood floors redone, and the guy who did the work said that if we insulate underneath than the floors would stay flush/even longer. So I started to research. Our house is on a raised foundation and I'm learning that the ventilated crawlspace doesn't work well, at least not for modern homes. It used to be recommended that we insulated under the floor, but now it seems that the prevailing advice is to condition the crawlspace. Basically, make it into a mini basement by closing off the vents, insulating the sides, and putting vapor barrier lining along the dirt floor and taping all the seams. Of course, our crawlspace is 2-3' tall, so the intention is not that it's usable like a basement, but rather the crawlspace is "inside" the house now, as opposed to be "outside."

A couple of references:
https://buildingscience.com/documents/information-sheets/crawlspace-insulation
https://www.bobvila.com/articles/insulating-crawl-space/

Thanks everyone! 

jpdx

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Re: Anyone condition / insulate their crawl space?
« Reply #1 on: December 11, 2017, 09:54:54 PM »
I need to make the same decision, except my crawlspace is just for a small section of the home, and basement under the rest. If I decide to insulate the walls with rigid foam boards, one challenge will be getting the boards through the tiny crawlspace access door in the foundation. Not sure if you have that issue.

I've read that this determination may be climate specific. Here is a resource for Oregon, and it looks like they only mention the traditional ventilated method:

https://insider.energytrust.org/wp-content/uploads/HES_WX_Manual.pdf

Also check if you have any local rebates, and if they have certain requirements.
« Last Edit: December 11, 2017, 09:56:43 PM by jpdx »

Fishindude

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Re: Anyone condition / insulate their crawl space?
« Reply #2 on: December 12, 2017, 08:08:10 AM »
I have an old farm house where the floors used to be cold.   Had one of those spray foam contractors come in and spray insulate the outside perimeter walls from underside of floor down to below grade.   This sealed up a lot of gaps and air leaks and keeps the crawl space much warmer.   To date, we've not added any heat to that space.

ManyMountains

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Re: Anyone condition / insulate their crawl space?
« Reply #3 on: December 12, 2017, 08:10:48 AM »
Did you add a vapor barrier lining to the floor too, or just the side insulation?

Fishindude

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Re: Anyone condition / insulate their crawl space?
« Reply #4 on: December 12, 2017, 12:14:57 PM »
No vapor barrier.  It stays pretty dry.

ManyMountains

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Re: Anyone condition / insulate their crawl space?
« Reply #5 on: December 12, 2017, 12:25:09 PM »
No vapor barrier.  It stays pretty dry.

Did you consider a vapor barrier? Why did you decide against using it? What part of the country are you in?

The dirt in our crawlspace stays super dry too, so avoiding the vapor barrier would save me a lot of time/energy in the install. But, everything I've read about insulating/conditioning a crawlspace put a great emphasis on using a vapor barrier and taping the seams. Maybe that's an issue for other houses or regions in the US.

Fishindude

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Re: Anyone condition / insulate their crawl space?
« Reply #6 on: December 13, 2017, 06:42:02 AM »
No vapor barrier.  It stays pretty dry.

Did you consider a vapor barrier? Why did you decide against using it? What part of the country are you in?

The dirt in our crawlspace stays super dry too, so avoiding the vapor barrier would save me a lot of time/energy in the install. But, everything I've read about insulating/conditioning a crawlspace put a great emphasis on using a vapor barrier and taping the seams. Maybe that's an issue for other houses or regions in the US.

I had a "cold floors" problem, not a moisture problem.  A vapor barrier is to keep moisture out, didn't think I needed it and still don't.
We are in the midwest.

If I was building new, I would make my crawl space extra deep, put down a vapor barrier and pour a lightweight slab, plus install a couple sump pits to pump from in the event water ever got in there.   A slab makes it real nice if you ever have to go back in there and do any plumbing or HVAC work, you can roll around on a mechanics creeper.   Would also insulate the inside face of all exterior walls with 2" rigid foam or sprayed foam, full depth.




Asalted_Nut

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Re: Anyone condition / insulate their crawl space?
« Reply #7 on: December 14, 2017, 04:16:23 PM »
One thing to consider, possibly depending on where you live, is how the insulation/vapor barrier will help with radon levels. We live in the PNW, in an area that is just lousy with radon, and vapor barriers help with that a little (along with a mitigation system, if necessary). Have you had your home's radon levels tested? Especially if you are closing off vents and sealing the space, if you don't have a mitigation system the radon would just go up into the house.. but if you already had it tested, or have a system, then that all is moot.

I admit, I am no expert, so perhaps someone could weigh in with their experience on if this is actually a legitimate concern.

Thanks for reading!

ChpBstrd

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Re: Anyone condition / insulate their crawl space?
« Reply #8 on: December 21, 2017, 02:33:36 PM »
I am suspicious of those companies claiming to make a ventilated crawlspace into an unventilated sterile clean space. There are 150+ year old houses using crawl spaces over bare dirt with no problem. This hermetically sealed crawlspace idea is untested in the long term IMO.

Moisture is the enemy. Lay down a vapor barrier but leave the crawlspace vented. My exterminator quoted me $350 to do the job, which is less than I could buy the plastic for!

If cold floors are bothering you, either hire a contractor to spray foam or DIY with *enclosed* fiberglass batts and supporting rods. Also check local codes to see if your crawlspace has too much ventilation. If you can, closing some of the vents in winter (only after vapor barrier installation) might make the crawl space and your floors warmer. Just be sure to reopen the vents in the spring as humidity creeps up.

ManyMountains

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Re: Anyone condition / insulate their crawl space?
« Reply #9 on: December 21, 2017, 04:17:12 PM »
I am suspicious of those companies claiming to make a ventilated crawlspace into an unventilated sterile clean space. There are 150+ year old houses using crawl spaces over bare dirt with no problem. This hermetically sealed crawlspace idea is untested in the long term IMO.

Are you skeptical of the companies that propose to condition crawl spaces, or the actual theory behind doing this? Because the research I've done makes it seems like the way to go, at least for my case. And the evidence that this works for 150 year old houses on the east coast doesn't necessarily mean that it'll work well for "newer" west coast houses.

Moisture is the enemy. Lay down a vapor barrier but leave the crawlspace vented. My exterminator quoted me $350 to do the job, which is less than I could buy the plastic for!

Again, this may be a regional difference, but I don't think moisture is the issue here in California. We have some humidity in the summer, but not like the east coast. Here, however, the temperature can swing be 40+ degrees between the day and night. But, the humidity could be an issue in that we have a conditioned house and an unconditioned crawl space, separated by wood floors. These floors are getting warped within one year of having them redone. So, whatever the cause (temp or humidity) the solution is the decrease that temp/humidity differential. You're suggesting insulating the floors but keeping the crawlspace vented. Can you provide a reference as to why this would work better than conditioning the crawlspace?

If cold floors are bothering you, either hire a contractor to spray foam or DIY with *enclosed* fiberglass batts and supporting rods. Also check local codes to see if your crawlspace has too much ventilation. If you can, closing some of the vents in winter (only after vapor barrier installation) might make the crawl space and your floors warmer. Just be sure to reopen the vents in the spring as humidity creeps up.
It's the combination of cold floors, high heating/cooling bills, and warping of hardwood that has use looking to improve the situation.

And to be clear, I'm thankful for your input. Your suggestions seem to contradict the research that I've done, so I'd be more likely to go your route if there were some references or data points to review. Thanks!

bacchi

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Re: Anyone condition / insulate their crawl space?
« Reply #10 on: December 21, 2017, 04:35:06 PM »
I'm probably going to put rigid foam under the joists and tape the seams. Spray foam under the joists in my climate makes for a condensation nightmare, per Building Science.

ManyMountains

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Re: Anyone condition / insulate their crawl space?
« Reply #11 on: December 21, 2017, 04:36:48 PM »
I'm probably going to put rigid foam under the joists and tape the seams. Spray foam under the joists in my climate makes for a condensation nightmare, per Building Science.
So you're going to insulate your floor but leave your crawlspace vented?

bacchi

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Re: Anyone condition / insulate their crawl space?
« Reply #12 on: December 21, 2017, 04:39:59 PM »
I'm probably going to put rigid foam under the joists and tape the seams. Spray foam under the joists in my climate makes for a condensation nightmare, per Building Science.
So you're going to insulate your floor but leave your crawlspace vented?

Correct. I can ensure that the joists are sealed well; getting the crawlspace 100% sealed will require a lot more time and money.


Eta: And I have leftover rigid foam from another project taking up space in the workshop.

Edit 2: https://buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces
« Last Edit: December 21, 2017, 04:52:04 PM by bacchi »

ManyMountains

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Re: Anyone condition / insulate their crawl space?
« Reply #13 on: December 21, 2017, 10:09:26 PM »
I'm probably going to put rigid foam under the joists and tape the seams. Spray foam under the joists in my climate makes for a condensation nightmare, per Building Science.
So you're going to insulate your floor but leave your crawlspace vented?

Correct. I can ensure that the joists are sealed well; getting the crawlspace 100% sealed will require a lot more time and money.


Eta: And I have leftover rigid foam from another project taking up space in the workshop.

Edit 2: https://buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces

Makes sense. For me, the side walls might be easier to seal, given that the HVAC ducts are routed through the floors, and the water pipes too, so sealing off the floor would be quite challenging.

The buildingscience.com articles are the best I've found too. Thanks for sharing!

accolay

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Re: Anyone condition / insulate their crawl space?
« Reply #14 on: December 24, 2017, 01:59:32 AM »
I'm down with putting in a plastic vapor barrier. Not only for the moisture, but I'd do it to keep the creepy crawlies down. A lot of times the dirt will look really dry, but if you dig down a bit... Also the radon levels as previously mentioned, depending on where you live.