Will insulating walls of crawl space help?

17 years ago

Thought I'd try this forum as well...

My sunroom is very drafty and over a crawlspace. Of course the many windows don't help but I feel cool air rushing up from the base moulding. I'm thinking that insulating the interior walls of this unvented 3-foot high crawl space (with a cement floor) with R-19 insulation sould help. But what type of insulation is best? The duct-work/floor is already insulated.

If I use batts, does it have to be faced or unfaced? Any fire code concerns? It doesn't matter what it looks like, asthetically speaking.

Also, I've seen that Owens and Johns Mansville sell a "basement blanket" type of insulation. It's nice b/c it comes in 4 or 6' widths for easier install. It's fully encapsulated, but not sure if it's overkill b/c it costs more than I wanted to spend--but it may save labor time/hassle.

Any advice welcome!

Sort by:Oldest

Comments (12)

brickeyee
17 years ago
Remove the base molding and caulk the wall-floor joint.
Even with insulation the crawl will always be cooler than the heated room and air will move.
mcassel
17 years ago
I would think about using a spray foam (closed cell) on the underneath of the sun-room floor... I think this would be far more effective at stopping drafts than putting batt insulation on the crawl space walls. I would also spend some time caulking the windows and other cracks in the walls.
Related Discussions
recouping expense of insulating crawl space
Q
Comments (1)
By blocking/sealing the crawlspace you will definitely have some heat savings and increased comfort. With the cost being 1500 though it will probably take a while to recoup. If you sealed it yourself the materials wouldnt cost you anywhere near 1500 dollars more like 500 or much less. All you would do is cover/close the vents with 2 inch pink foamboard and place foamboard against the block walls. Seal them all with foam and then lay 6 mill poly sheeting on the floor (overlap 12 to 24 inches and tape them) and tape it to the foamboards on the wall. Its pretty easy if you have access to the crawl. Home depot sells the foamboard in 4X8 sheets for $25 and great stuff foam for 5 bucks a can. I dont know about the poly sheeting though but check it out.
...See More
Help with insulation in crawl space!
Q
Comments (5)
I dont know what code is in your area but if you have humidity in summer that insulation will get wet and ruined even if it doesnt get rain on it. Did he put a vapor barrier on the floor of the crawlspace and lap it up on the walls? Maybe ask him to put in some insulation like foamboards? They dont get ruined when wet. In my cold climate we dont put insulation foamboards on the floors above but on the crawlspace walls and seal it up with a 6 mill poly on the floor of the crawl.
...See More
Will insulating the crawl space help reduce cooling costs?
Q
Comments (3)
yeah...Entergy is going to help you out! LOL! they do actually have a program in N.O. through Entergy using local energy raters. a little biased, but it is what it is. below is a copy & paste link to LSU AgCenter's study about insulating floors in homes with open crawlspaces. http://www.lsuagcenter.com/NR/rdonlyres/D33F711D-DC4B-4E4C-9ED6-A97DCE9DB026/79806/pub3187insulatingraisedfloorsHIGHRES.pdf I plan to insulate my floors with closed cell 3" everywhere...not average fill. once floor in bathroom is replaced and plumbing is finished. your biggest battle is going to be getting 3" everywhere, and not just averaged fill. plan to crawl under house before they leave. take a piece of wire with inches marked on it and a can of spray paint. have them come back and touch up low spots. knowing the foam companies you'll have to deal with, plan on double checking the work and not relying on their word that it is right. understand that closed cell is about R-7 per inch so 3" is R-21. actual R-values not quanitive values are what is important. best of luck.
...See More
How to insulate a crawl space?
Q
Comments (5)
I happen to have the NKBA book "Residential Construction" right here - am reading through it. Pg 67 addresses this. It says, "Kitchen and bath floors above crawl spaces should contain insulation to stem heat loss and a vapor barrier to keep moisture out. Insulation can go either between the floor joists or at the foundation wall. Insulating the floor itself allows the crawl space to be continuously ventilated (required by some local codes) but is harder to do. Also, any water pipes and heating ducts that run under or within the floor must be wrapped." We have an over-5-foot crawl space under our entire house and it's insulated just under the floor with the 6" batting type. Our vapor barrier (or at least what I *think* is our vapor barrier - we may have another one in the floor itself as talked about below) is huge sheaths of thick black plastic taped together with heavy duty tape - and the vapor barrier is sitting on the ground. We have not experienced the floor being cold at all - we have linoleum, wood, and carpet, and none are cold, even in the coldest weather. The paragraph goes on to say, "On the other hand, the foundation can be easily insulated on the inside or outside face. However, any vents in the wall must be closeable during the cold season. The location of the insulation also affects where the vapor-control barrier goes. If the floor joist cavities are insulated, the barrier should go between the insulation and room above, usually between the floor joists and subfloor. The best vapor barrier is a sheet of polyethylene at least 4 mils thick. The foil or Kraft paper facing on batt and blanket insulation is not a reliable vapor barrier. If you choose to insulate the foundations walls rather than the floor, the vapor barrier should go next to the inside face of the wall and extend completely over the soil below the crawl space. Another way to insulate the foundation is to apply rigid foam to the outside of the crawl space, but this is more easily done on new construction. An existing foundation will have to first be excavated down to the footing." HTH
...See More
Pooh Bear
17 years ago
I was also wondering about the effects of insulating the inside
of the foundation in my crawlspace, using 2inch thick polystyrene.
The underside of my floor is not insulated. And the crawlspace
is a dirt floor. I was specifically told not to insulate the
floor so that heat could seep into the crawlspace and keep the
water pipes from freezing. (the waterpipes are insulated).
But last week on a very cold day I went around back of the
house and opened the door into the crawlspace. It was very
warm in there. So I suspect I am loosing a lot of heat thru
the foundation walls. Not to mention into the ground.
Would insulating the concrete block foundation walls
be worth the cost (ie: ROI > cost of lost heat).

Thanks.

Pooh Bear
jamesbodell
17 years ago
Poo bear, I have done some research on this for my own home and come to the folowing conclusions.

If you have water pipes under, try and leave the floors un-insulated. Get Thermax (a Dow product) wall system and line the basement walls with it. Use strappign and concrete screws. Put 6 Mil plastic on the ground.

Do not use regular polystyrene as it will hold water and lose R value. You need XPS for this application. I specify Thermax because you do not need to cover it with wallboard (code issue here).

If water pipes are not an issue, I would blow icynene under the floors.However, this, I believe, is an open celled product.

mcassel: why closed cell. I have never fully understood the difference.
mcassel
17 years ago
Yes icynene is an open cell foam... The main difference between the two is open cell can absorb moisture where as closed cell is water proof and can act as a vapor barrier... Both are great products and in most places I don;t think it makes a big difference but somewhere that is damp naturally, well I think blocking that moisture would be a good thing too.
jamesbodell
17 years ago
Sounds reasonable. But What I have read in the icynene web site (granted, bias) states that open cell will dry out as well as absorb. They state that Icynene can be used as a vapor barrier as well.

What are examples of closed cell products? I should look into them
mcassel
17 years ago
I would check out these two web sites and talk to some pros in your area. GL

www.sprayfoam.com
www.sprayfoam.org
popesterb
17 years ago
Sorry to get slightly off topic, but can you use this Icynene or another type of spray foam strictly to spray on ABS and metal duct work in attics and crawl spaces?
Pooh Bear
17 years ago
When I said polystyrene I meant the insulating panels
that come in 4x8 sheets from Lowes or Home Depot.

Pooh Bear
jamesbodell
17 years ago
Poohbear; right, they carry many kinds. The white stuff that is cheaper won't work. Make sure it states XPS. I do not think the foil faced stuff will work either. its called polyisocyanurate or something like that

If you are concerned about code, all this stuff must be covered with a fire block layer, ie: wall board.
Pooh Bear
17 years ago
Thanks for the info.
Have to ask the house insurance agent about the code.
If it passes him then it can go in. No codes here.
Code only matters if it matters to insurance agent.

Pooh Bear
jamesbodell
17 years ago
Let me know his thoughts. I am having a hard time finding a supplier of thermax. I am looking at the moment into possibly a fire rated paint? to paint voer the foam? Don't know, ask your insurance guy about that, too.

Will insulating walls of crawl space help?

Comments (12)

brickeyee

mcassel

Related Discussions

Pooh Bear

jamesbodell

mcassel

jamesbodell

mcassel

popesterb

Pooh Bear

jamesbodell

Pooh Bear

jamesbodell

COMPANY

BUSINESS SERVICES

GET HELP

CONNECT WITH US