# insulating crawl space



## chrisasst (Jan 23, 2013)

So my floors are freezing. I can feel the cold air come up through them. Under them is the crawl space. What can I do.  When I saw crawl space, I am literally talking about a space a little kid would have trouble crawling around in.  I have tried to seal up the outer perimeter. But obviously I need to do something more with that also.  
I am pointing a IR thermometer at my floor right now and it is 38 degrees...
what can I do?  I know carpet would help a little but..


----------



## Highbeam (Jan 23, 2013)

You have a couple of options.

One is to insulate the perimeter walls that hold up your house and then close off all the crawlspace vents. The crawl becomes a warm space and your floors won't be so cold. You need a dry crawl for this so no water issues. Your plumbing will also be in the warm crawlspace which is good.

The other option which is much more common is to leave the vents but insulate the floor from below. This is what I had done a few years ago and the floors were immediately warmer. I think they used R18 faced FB batts. Hire this job out. It is terrible work crawling around on your back pushing thick batts up against the bottom of the floor.

Current codes require this floor insulation so the pros know how to do it. They are not afraid of slithering around on their bellies to install the FG.


----------



## yooperdave (Jan 23, 2013)

Another good application for spray foam...the rigid type, not the retro foam that can be added to walls


----------



## chrisasst (Jan 23, 2013)

yooperdave said:


> Another good application for spray foam...the rigid type, not the retro foam that can be added to walls


 
This is one thing I thought about, but don't know where to start.  Does Lowes rent / have this type of machine to do this or is this a leave it to the pros kind of thing?   

And there are, at the moment, no plumbing down there in this crawl space..


----------



## yooperdave (Jan 23, 2013)

Chrisasst--I would think that someone rents the equipment and materials.  I occasionally see them on craigslist around here. 
After too many years of crawling around in crawl spaces, I would definetly hire it out.  If it is a 'tight" space like you mentioned, be sure to inspect the job before you pay full.  That way, any missed or weak spots could be dealt with.


----------



## Highbeam (Jan 23, 2013)

Foam application is almost exclusively done by professionals. It is extremely expensive.


----------



## ScotO (Jan 23, 2013)

HB is right.  Not to mention it gets pretty warm when doing it.  My cousin just had his new house done with spray foam, and man that was unreal.  The guy doing it looked like the Michelin man every half hour or so, he had to remove the Tyvek suit and resuit up several times......messy isn't the word for it...


----------



## seige101 (Jan 23, 2013)

Definitely look into having a contractor do it. It is probably only a few dollars more than buying the material your self and you don't have to deal with the pain in the ass suck job that it is. Bonus points if your state or local utility company has a program similar to mass save, where they will pick up most of the tab. Something to look into.


----------



## semipro (Jan 24, 2013)

Given current pricing and availability, IMO there are only two ways to install foam that make sense:
- Hire a contractor to spray foam
- Install board foam products in between the floor joists (eps, xps, polyiso) yourself or have a contractor do that. These are sealed in place with spray foam from a can.

Fiberglass batts are rarely installed properly under floors.  To work well there must be no air gap between batt and floor.  You'd need to add an infiltration barrier like Tyvek also to prevent air flow though the batts and into your house.


----------



## serveprotect (Jan 24, 2013)

I am in the exact same situation.  Remodeling an old summer kitchen and turning it into a living space.  It is not my forever home and ripping up the floor would be a major undertaking.  Since i have to build up the floors 2 inches to level with shims i plan on spraying between them with spray foam i have left over from the walls.  I did the walls myself with spray foam.  The kit came in a propane tank setup and took me about 30 min to do a 300 sf room.  Imo it was a very easy diy project.  I will add it was more expensive than traditional insulation but sealed up an old room very well.  Also,  make sure you have the room atleast 70 degrees to make the foam work properly.  Do you guys think my plan will work?  Figure it cant hurt.


----------



## Highbeam (Jan 24, 2013)

semipro said:


> Fiberglass batts are rarely installed properly under floors. To work well there must be no air gap between batt and floor. You'd need to add an infiltration barrier like Tyvek also to prevent air flow though the batts and into your house.


 
The pros that did mine used faced batts held up tightly to the subfloor with lots and lots of that nylon string. Seems pretty hard to screw up.


----------



## semipro (Jan 24, 2013)

Highbeam said:


> The pros that did mine used faced batts held up tightly to the subfloor with lots and lots of that nylon string. Seems pretty hard to screw up.


Many will install batts under floors by stapling the facing to the joists. 
This almost always results in an air gap between floor and batt.


----------



## Highbeam (Jan 24, 2013)

My floors were uninsulated when I moved in. House was built in 1963. The Floors are 1.5" thick T&G decking perpendicular to beams at 5' spacing. So they had to use strings to hold the batts up. Above the decking is tar paper, and then in the kitchen 5/8" plywood and then linoleum. The biggest difference after the insulation was that when you stood in one place on the linoleum it would heat up the floor and then you could find your hot footprints if you stepped away for a second. Before the insulation is was like walking on cold concrete all the time.


----------



## daveswoodhauler (Jan 24, 2013)

I thought Flatbed Ford had used the sprayfoam in his crawlspace....and posted the results....will see if I can find the thread.

This is a pretty good thread:

https://www.hearth.com/talk/threads...d-now-with-pictures-2-2-10.46321/#post-590841


----------



## chrisasst (Jan 24, 2013)

daveswoodhauler said:


> I thought Flatbed Ford had used the sprayfoam in his crawlspace....and posted the results....will see if I can find the thread.
> 
> This is a pretty good thread:
> 
> https://www.hearth.com/talk/threads...d-now-with-pictures-2-2-10.46321/#post-590841


 
Interesting. Too bad they are in CT.. not my area..


----------



## begreen (Jan 25, 2013)

We had an estimate for a pro to come and insulate underneath our floors. Same problem, toward the perimeter on a couple sides only a child would fit. I once almost got stuck in there. Guy came by, gave us an estimate that we approved. A week later the crew showed up. The got in the crawl space and about 5 minutes came out, packing their gear. Both said they couldn't and wouldn't do the job.

That was 2005. Looking back, they were right and even it they could, by now half the insulation would have been rodent nesting. Our "foundation" walls on one side were just stem walls and the south side just rest on a large rough doug fir 8x8. In 2006 we bit the bullet and put in a proper foundation by raising the house 6ft and setting it back down on a new 3ft higher foundation. Now we have a bullet proof easy to work in crawlspace that my son and I insulated. Temp hardly varies down there. This isn't the only option. If your foundation is sound and good and the footings deep enough, you may be able to dig out those low areas instead.


----------



## Highbeam (Jan 25, 2013)

BG, didn't you do the "warm crawlspace" method where you insulate the stemwalls, bare floor, only a VB over the dirt, and no ventilation?


----------



## begreen (Jan 25, 2013)

Correct. We totally tossed out the old plan once the house was raised and on a solid foundation. It's interior insulated with a vapor barrier over the dirt. The space is ventilated in the summer, but not in the winter. All the ductwork, hot water heater and hot water pipes are insulated in the crawl space. It stays a pretty constant 60-63F all winter long with no supplemental heat.


----------



## semipro (Jan 25, 2013)

begreen said:


> Correct. We totally tossed out the old plan once the house was raised and on a solid foundation. It's interior insulated with a vapor barrier over the dirt. The space is ventilated in the summer, but not in the winter. All the ductwork, hot water heater and hot water pipes are insulated in the crawl space. It stays a pretty constant 60-63F all winter long with no supplemental heat.


Why is summer ventilation needed?


----------



## begreen (Jan 25, 2013)

Prolly not necessary, but it's easy to do. I tried going a year with it closed and find it smells a little musty after a while. Also, my "vents" are nice big 18" square holes with galvanized screen on them. This is where the large I beams went through to support the house when it was airborne. When they are open it lets in daylight like a window which is nice.


----------



## Cross Cut Saw (Jan 26, 2013)

I insulated two crawl spaces under my home, one was an addition that was built in 2010 so the boards were nicely spaced 18" on center (I think) and 96" long.  It was very easy and I was able to get insulation bats that exact size and put them in held up by rods.

The other space was a project from hell.  It was a very tight fit for me (6' 240lbs.) but I slithered around on my back and stomach for a day doing it.  It was an old carriage house that had been attached to the back of our house by the previous owners and used primarily as a 3 season space.  The floor appears to be framed by a drunken sailor, from 16" on center in some parts to 24" on center in others.  So to use those same bats I had to turn the bat sideways and cut each and every piece so that I could cram it into the space.  I can't remember how many pieces it took but it was the worst experience of any DIY project I've ever done...


----------



## Trilifter7 (Jan 27, 2013)

Has anyone ever heard of using the foam sheets to insulate the floors? I am considering putting them against the bottom of the floor joists and taping the seems to give an insulated air lock between the floor and the bottom of the joists. Not sure if this would actually work but seems like an easy way to do it.


----------



## semipro (Jan 27, 2013)

Trilifter7 said:


> Has anyone ever heard of using the foam sheets to insulate the floors? I am considering putting them against the bottom of the floor joists and taping the seems to give an insulated air lock between the floor and the bottom of the joists. Not sure if this would actually work but seems like an easy way to do it.


I think this would be okay.  It would be much better if the space between the joists were filled with insulation. Alternatively, you could install foam board between the joists and against the floor, sealing it in place with canned spray foam.  Additional insulation could then be added with a housewrap installed along the bottom of the joists to stop air infiltration.


----------



## Trilifter7 (Jan 27, 2013)

semipro said:


> I think this would be okay. It would be much better if the space between the joists were filled with insulation. Alternatively, you could install foam board between the joists and against the floor, sealing it in place with canned spray foam. Additional insulation could then be added with a housewrap installed along the bottom of the joists to stop air infiltration.


 
Thanks for the info. I'm def going to look into it more.


----------



## woodgeek (Jan 28, 2013)

I'm  late to the party, but I want to say that if your floors are 38°, that is not an insulation issue so much as an airsealing issue.  You crawl is cold due to stack effect hoovering outside air into your crawl, either through a vent you missed, around the rim joists, sill plates etc.  Rather than insulating the floor, I think you would get better ROI spray foaming the rims and closing the vents, and then insulating the perimeter (if needed).

You could also get a warmer floor by airsealing the top of the house.  Air comes in has to go out somewhere.  You feel where it comes in and blame that, but seal where the air is going out, and your floor will get warmer.


----------



## TheMightyMoe (Jan 28, 2013)

If it's draft that is getting you, and you can fit down there, the easiest fix is to go around with caulk gun / canned spray foam and just fill up any holes/gaps on the outside wall.

Once you have the draft fixed then you can decide if you need insulation (Which you likely do, but air sealing will make a BIG difference)

Make sure you have a vapor barrier on the floor, and it is completely sealed.

If you decide to insulate, you can put up fiber glass batts on the outside wall. This is assuming the crawl space is dry. This is the BANG FOR BUCK option, I did this with R38, and my crawl space has been 10-20* warmer since.

If your gonna fork out money, I would simply follow everyone elses advice, and pay a professional to come spray foam the perimeter wall. Air tight, water proof, with a high insulation value. Nothing wrong with that.

I'm not a fan of just insulating between joists, bu to each his own.


----------



## Trilifter7 (Jan 28, 2013)

woodgeek said:


> I'm  late to the party, but I want to say that if your floors are 38°, that is not an insulation issue so much as an airsealing issue.  You crawl is cold due to stack effect hoovering outside air into your crawl, either through a vent you missed, around the rim joists, sill plates etc.  Rather than insulating the floor, I think you would get better ROI spray foaming the rims and closing the vents, and then insulating the perimeter (if needed).
> 
> You could also get a warmer floor by airsealing the top of the house.  Air comes in has to go out somewhere.  You feel where it comes in and blame that, but seal where the air is going out, and your floor will get warmer.



That was another thing I was thinking of. Thanks for the info. I think I'm going to look at sealing up the crawl first then insulating the floor later.


----------



## Trilifter7 (Jan 28, 2013)

TheMightyMoe said:


> If it's draft that is getting you, and you can fit down there, the easiest fix is to go around with caulk gun / canned spray foam and just fill up any holes/gaps on the outside wall.
> 
> Once you have the draft fixed then you can decide if you need insulation (Which you likely do, but air sealing will make a BIG difference)
> 
> ...



Yea I'm def thinking sealing the crawl up is the first thing to tackle


----------



## peakbagger (Jan 28, 2013)

One thing you dont want to do is seal up the crawl space tight with no ventilation. I have seen some camps that were sealed up and the floor joists were like sponges after a few years. There are contractors that come in an lay some sort of plastic down on the floor and up the walls and seal all the seams to keep moisture from the ground from getting under the house and I even think they install some vents.


----------



## TheMightyMoe (Jan 28, 2013)

""Assuming it is a dry crawlspace""

If your walls leak waters, you got other issues...

If you vapor barrier the floor, with proper air sealing, moisture should not be getting in the home/crawlspace.


----------



## Highbeam (Jan 28, 2013)

peakbagger said:


> One thing you dont want to do is seal up the crawl space tight with no ventilation. I have seen some camps that were sealed up and the floor joists were like sponges after a few years. There are contractors that come in an lay some sort of plastic down on the floor and up the walls and seal all the seams to keep moisture from the ground from getting under the house and I even think they install some vents.


 
No, there are actual official standards for doing this with no vents. Just look at it like a basement with a low ceiling height, you don't ventilate your basement do you?


----------



## Highbeam (Jan 28, 2013)

TheMightyMoe said:


> ""Assuming it is a dry crawlspace""
> 
> If your walls leak waters, you got other issues...
> 
> If you vapor barrier the floor, with proper air sealing, moisture should not be getting in the home/crawlspace.



I've never been to Alaska but here in the northwest we have something called groundwater. You dig a hole in your lawn and the next morning it will have water in it even if it is not raining. During the wet season especially, it will come in from below the home and most houses in low elevations will have water in their crawlspaces under and/or on top of the plastic vapor barrier. The walls are not leaking, this is not surface water.

Folks do all sorts of things like sump pumps and drains to get rid of this water. Lots of sump pumpers on this board and it's not because of leaky walls.


----------



## TheMightyMoe (Jan 28, 2013)

Then it would not be a very dry crawlspace. Sounds like you live somewhere with a high water table. I live in a desert thankfully.


----------



## Highbeam (Jan 28, 2013)

I dare say that more often than not, folks have moisture issues in a crawlspace. Some of the smarter builders have begun to backfill the crawlspace excavation so that the groundwater level is not above the soil level in the crawl. Thing is, you need undisturbed soil for any concrete support pads on the crawlspace floor so you need to pour some thick pads.

My crawl is now dry. It had 6" of water in it when I bought the house.


----------



## Trilifter7 (Jan 28, 2013)

Highbeam said:


> I dare say that more often than not, folks have moisture issues in a crawlspace. Some of the smarter builders have begun to backfill the crawlspace excavation so that the groundwater level is not above the soil level in the crawl. Thing is, you need undisturbed soil for any concrete support pads on the crawlspace floor so you need to pour some thick pads.
> 
> My crawl is now dry. It had 6" of water in it when I bought the house.



What did you do to get the water out? My crawl never stays wet but I have a sump pump that only runs when it rains. If its dry outside its normally dry under my crawl. One issue I have is that the floor was insulated and it must have gotten wet bc someone ripped it all out and left it in piles down there. I believe my moisture problem is due to saturated batten rotting in my crawl. I suppose a start will be to clean it out then insulate the outside masonry walls and seal up any leaks. Would batten or foam sheets be better on the masonry walls?


----------



## firefighterjake (Jan 29, 2013)

When we bought our home it said in the crawl space there was a "damp" area . . . in the Spring we learned that what this meant was 3-6 inches of water . . . we have since put down crushed rock and a vapor barrier . . . but we still get the water coming up through . . . sump pump takes care of most of it though.


----------



## Highbeam (Jan 29, 2013)

Trilifter7 said:


> What did you do to get the water out?


 
I live on a hill. So I dug under my footing to the lowest point in my crawlspace, then installed a pipe with slope that drains any water downhill to where it daylights. I also regraded around my home so that I have 15' in all directions sloping away from the house at 2%. Then I installed a curtain drain (aka french drain, burrito drain, etc.) at that 15' distance as well as a new downspout collection system that also drained well down the hill. My goal was to remove any potential surface water source and have an emergency crawlspace drain just in case.

It's dry down there now. Only damp dirt under the new plastic.

People have gone so far as to pump concrete into their crawlspaces to pour a "rat slab" whatever that is.


----------



## begreen (Jan 30, 2013)

Highbeam said:


> I've never been to Alaska but here in the northwest we have something called groundwater. You dig a hole in your lawn and the next morning it will have water in it even if it is not raining. During the wet season especially, it will come in from below the home and most houses in low elevations will have water in their crawlspaces under and/or on top of the plastic vapor barrier. The walls are not leaking, this is not surface water.
> 
> Folks do all sorts of things like sump pumps and drains to get rid of this water. Lots of sump pumpers on this board and it's not because of leaky walls.


 
Not just in the west, my SIL has this in her house in Mass. too. It has to do more with local topography. If there is clay underneath the top soil, moisture is going to rest there. A lot of the area north of Boston is built on swampland that stay at near saturation year round.


----------



## begreen (Jan 30, 2013)

peakbagger said:


> One thing you dont want to do is seal up the crawl space tight with no ventilation. I have seen some camps that were sealed up and the floor joists were like sponges after a few years. There are contractors that come in an lay some sort of plastic down on the floor and up the walls and seal all the seams to keep moisture from the ground from getting under the house and I even think they install some vents.


 
Highbeam is correct. You need to evaluate the soil and house before deciding to do this. Our house has wide overhangs, good gutter drain system and soil that drains straight down. That makes for a nice dry crawlspace. After 6 years we have had zero issues with our sealed crawlspace and a lot of benefit.

Ironically an open crawlspace can be the source of too high moisture too, especially back east with their humid summers. If the crawlspace is much cooler than the humid outside air (and it often is) moisture can condense on the joists and sills.


----------



## Trilifter7 (Jan 30, 2013)

begreen said:


> Highbeam is correct. You need to evaluate the soil and house before deciding to do this. Our house has wide overhangs, good gutter drain system and soil that drains straight down. That makes for a nice dry crawlspace. After 6 years we have had zero issues with our sealed crawlspace and a lot of benefit.
> 
> Ironically an open crawlspace can be the source of too high moisture too, especially back east with their humid summers. If the crawlspace is much cooler than the humid outside air (and it often is) moisture can condense on the joists and sills.



Good to know. I'm not thinking of sealing it off completely right now. I think I will work on insulating the masonry walls and getting the vents so I can seal them off in the winter and open them up in the summer


----------

