# Insulating a Crawl Space



## Downstate Doug (May 8, 2001)

Which is the proper way to insulate a vented crawl space? I have heard and read about many ways. Has to be a way they are doing new construction to some sort of code. Being 2012 one would think they have it figured out by now. The area is approx. 30 x 15 ft. The entry is from a small door in the floor. Cannot enter from the basement.

I have been told do/dont insulate between the floor joists.
Do/dont insulate piping and ductwork.
Do cover vents to make it unvented.
Just insulate walls and dont use foam sealer.

Any consensus help is appreciated. I think it is a job I can do myself but want to do it right.

DD


----------



## Greenbush future (Sep 8, 2005)

Well I'll tell ya what I did on my Tri-level right or wrong. First off, I open and close my external vents, closed in winter, open in summer. Then I stuffed large bats of insulation in-between the floor joist's and in most of the corners where the joist's rest on the slab walls. I cant say my floor (inside the house) is any warmer by doing this, as this area is the farthest run, away from my furnace, and I have no vents (internal furnace) that heat this area well. My goal was, accomplish reduced heat bills and try to warm the floor up. Ended up using a large rug on the kitchen floor to keep my toes warm. And I installed the insulation with the paper side of the insulation bat's out, so all I see when I go down there is the paper. Didn't do anything on my water pipes.


----------



## wally-eye (Oct 27, 2004)

Greenbush future said:


> Well I'll tell ya what I did on my Tri-level right or wrong. First off, I open and close my external vents, closed in winter, open in summer. Then I stuffed large bats of insulation in-between the floor joist's and in most of the corners where the joist's rest on the slab walls. I cant say my floor (inside the house) is any warmer by doing this, as this area is the farthest run, away from my furnace, and I have no vents (internal furnace) that heat this area well. My goal was, accomplish reduced heat bills and try to warm the floor up. Ended up using a large rug on the kitchen floor to keep my toes warm. And I installed the insulation with the paper side of the insulation bat's out, so all I see when I go down there is the paper. Didn't do anything on my water pipes.




I did mine the same exact way. Had a contractor say that putting insulation up that way was wrong and would draw in and hold moisture..........sure didn't work that way with mine. I pull down a section every once in a while and it will be completely dry, no moisture nor any hint of mold.... I have a dirt floor that's covered in plastic...

The only water line wrapped is where the main comes thru the outside wall from the well.....16 years and have never had a frozen pipe..


----------



## Duckman1 (Oct 14, 2004)

Does it have a concrete floor in the space? Is it a conditioned space? At minimum it should have a poly barrier over the dirt or stone if that what it is. Code in most places now for crawl is 2" rigid foam on the foundation walls. I will install 2" rigid foam up tight to the subfloor in between the joists as well. The ducting should have been insulated at time of contruction. Can be done now but more difficult. Don't block off your vents those are there to let moisture vent out. You can purchase replacements now that will open and close with the changes in temperature.


----------



## storman (Mar 12, 2008)

Cover floor if dirt or stone like stated. Sprayfoam walls and then condition the space if sprayfoamed ir wont take much to condition the space did it for my inlaws and they couldnt be happier.

Outdoor Hub mobile, the outdoor information engine


----------



## mmac1318 (Feb 5, 2007)

Duckman1 said:


> Does it have a concrete floor in the space? Is it a conditioned space? At minimum it should have a poly barrier over the dirt or stone if that what it is. Code in most places now for crawl is 2" rigid foam on the foundation walls. I will install 2" rigid foam up tight to the subfloor in between the joists as well. The ducting should have been insulated at time of contruction. Can be done now but more difficult. Don't block off your vents those are there to let moisture vent out. You can purchase replacements now that will open and close with the changes in temperature.


Hi I am a BPI certified home energy auditor and just wanted to say that this is the correct way to do it but wanted to add to it. If you use the insulation board make sure it is a closed cell foam to keep moisture from absorbing into it. You could also have it spray foamed but it is fairly expensive. Make sure the plasic seams overlap and are taped then run it up the wall above the joints. You probably should insulate the ducts. Depending on the type of ducts I would probaly use batt insulation above and around the ducts. Insulation between the joists is most likely not neccesary unless it is a conditioned space which most crawls arent. If you have other areas of concern a enrgy audit would give you alot of good information. good Luck.


----------



## BFG (Mar 4, 2005)

My crawlspace was just re-insulated according to code in my area by a local contractor. They used insulation bats tacked to the foundation cap around the entire perimeter. I inquired about the closed cell foam board for my foundation walls but the contractor told me that it would have to be 8" thick (i.e. four 2" sheets glued together) to meet our code. My job was an insurance job since my crawl was flooded when a neighbors sewer contractor cut off my sewer line and perimeter drain tile. 

My furnace is in my crawl, and my ductwork is not wrapped. I have considered wrapping it with Reflectix, but I am still researching it. It is very warm in the crawl when the furnace is running, and I am almost positive that I am venting heated air out of the ductwork at one or more points. I have poor flow in the farthest floor vents. I open the foundation vents in the warm months, and close them in the winter. The Reflectix site says you can use their product in between floor joists in crawls, and between trusses in attics. I've talked to a couple friends who are contractors and they both told me that they would NOT put that product in either place. 

Frustrating thing for me is that I also had to have a perimeter tile and permanent sump pump installed in my crawl after the issue with the contractor. I've never had water down there in the 10 years I have lived there. Not the case now...dang sewer jobs...


----------



## Greenbush future (Sep 8, 2005)

I does make sence on the keeping them open for ventalation. In my case I am working with cement floors/walls with no moisture issues, I close them in the winter only to keep the draft s out. The area isnt heated, and it is 20 degree's cooler, but I do have water lines running through this area. I would guess the reason I even have vents that open close are to help moisture to escape. Any other reason they would be closable?


----------



## redneckmi2 (Jan 3, 2010)

I read this post yesterday and it got me thinking about my crawl space. I crawled under a couple of weeks ago and the insulation was falling down between the joists and the vents were knocked out. I stuffed the insulation back up where it wasn't destroyed by rodents and I put some 1.5" blue foam in the vents for the winter (I'll remove them and replace the vents in the summer). 

While I was under there I noticed that the lines running to the floor vents were insulated while the main duct running down the center of the room was not insulated. This is a square duct that runs between the floor joists. I also noticed that it had a vent in it that vents into the crawlspace. * Is that vent suppose to be there?* It seems like I am loosing heat/cooling through it. (FYI, the crawlspace is for an addition that was built on the house before I purchased it and the access is in my basement).


----------



## Greenbush future (Sep 8, 2005)

redneckmi2 said:


> I read this post yesterday and it got me thinking about my crawl space. I crawled under a couple of weeks ago and the insulation was falling down between the joists and the vents were knocked out. I stuffed the insulation back up where it wasn't destroyed by rodents and I put some 1.5" blue foam in the vents for the winter (I'll remove them and replace the vents in the summer).
> 
> While I was under there I noticed that the lines running to the floor vents were insulated while the main duct running down the center of the room was not insulated. This is a square duct that runs between the floor joists. I also noticed that it had a vent in it that vents into the crawlspace. *Is that vent suppose to be there?* It seems like I am loosing heat/cooling through it. (FYI, the crawlspace is for an addition that was built on the house before I purchased it and the access is in my basement).


My furnace main runs through my crawl space and doesnt have any vents at all, the area has slab floor and walls. I do have external vents that allow air from outside to enter, but I close mine in the winter to help keep my kitchen floor above, warmer. And it's always cold, and it's that farthest location from my furnace.


----------



## AJ swampbuster (Jan 24, 2012)

I work for a foam company he sprays closed cell foam we do these all the time he's really good at what he does. He would come put plastic down first close or cover vents however us like it and then he will spray 2 in on walls, bonds and seal the plastic to floor. Let me no if interested. His price is 90cents square foot per inch

Outdoor Hub mobile, the outdoor information engine


----------



## MEL (Jul 17, 2005)

Downstate Doug said:


> Which is the proper way to insulate a vented crawl space? I have heard and read about many ways. Has to be a way they are doing new construction to some sort of code. Being 2012 one would think they have it figured out by now. The area is approx. 30 x 15 ft. The entry is from a small door in the floor. Cannot enter from the basement.
> 
> I have been told do/dont insulate between the floor joists.
> Do/dont insulate piping and ductwork.
> ...



Energysavers.gov is a Gov site that you can look up the proper way to insulate a crawlspace. For a Gov. site they do a pretty good job with it. 
They dont go into detail about vented/unvented crawls as regards to closeing your vents.
Owenscorning.com (the pink insulation) also have a decent site with details about crawls. One word of caution, owens is a great marketing company and pushes THEIR products as THE best products, In many cases its not.

If you have a vented space and keep the vents open all year, use the floor insulation method. If you are like me and close your vents in winter
(I also use 2" rigid foam cut to fit to seal it) then you can use the wall insulation method. 
I strongly suggest air sealing before insulating. Pretty simple. use the can of Great Stuff and foam the perimeter of every band joist (google: sealing band joists) to keep cold air out. Make sure what ever type insulation you use that you insulate the Band joist as well. If using the wall method a 4+mill thick visqueen vapor barrier needs to be applied to the floor prior to insulating. The visqueen needs to go up the wall or the insulation need to overhang onto the visqueen buy like 24" for a good seal. 

You can cover your vents to make it a unvented space but realize you can cause harm (moisture/mildew) buildup with no air flow. Do as I do and cover in winter (with additional piece of foam insulation) to keep cold out. In spring I uncover to allow air flow.

Insulating the walls with out a foam sealer is really doing half the job, its better then nothing but in the end just spend a few more dollars and alittle extra time and do the job right.

Hope this helps, contact me if you have any other questions.


----------



## MEL (Jul 17, 2005)

BFG said:


> My crawlspace was just re-insulated according to code in my area by a local contractor. They used insulation bats tacked to the foundation cap around the entire perimeter. I inquired about the closed cell foam board for my foundation walls but the contractor told me that it would have to be* 8" thick* (i.e. four 2" sheets glued together) to meet our code.


What? Batt insulation is approx 3 R per inch. Closed cell Foam Bd is approx 5 R per inch. 8" of the Foam Bd would equal R-40 total. I dont know the code but highly doubt it even near R-40? I dont think its even half of that. Go to any Lowes or Home depot and look at the pink or blue closed cell foams they are all R-5 per inch. 
The guy who posted above you, mmac1318 would be able to confirm this. He's BPI certified so he's the man to ask.


----------



## BFG (Mar 4, 2005)

R-19 is what I was told.


----------



## MEL (Jul 17, 2005)

BFG said:


> R-19 is what I was told.


Sounds about right. R-19 would be a 6" thick batt so that sounds correct.
Why your contractor said the 8" of foam bd? That dosent add up. 4" would be R-20. I would prefer the foam bd myself.


----------

