Best insultation for crawl space under modular

[Michelle K linnane]

Hi Guys
I had a lot of action about my post of reducing heating costs by wood stove another thing I am going to do is insultate my cement block crawl space in the spring or this summer. Crawl space is 4 blocks high. The house it self is
r22 on floors, r21 on walls and R44 in ceiling. If I remember house 30 feet wide and 50 feet long.

I have a modular that sits on a cement slab slap, with concrete blocks around as a foundation. Nothing in crawl space, house has been here 6 years. In past years I have placed round bales against foundation(from 95% wind side) and had it make a difference with making house warmer. Also this year we have a lot of cold and no snow to bank the house. Wind can not get in a quick and steal heat. There are 4 windows to vent the crawl space that I can open from the outside as I wish. I am sure there are drafts between block and house as house does not sit on the block.

My choices for insultation (already elminated fiber glass)
I have 2 different thoughts about insulation


Blue or pink board (cheapest more then likely)
Getting blue board and trying to do at least an r15 in the back of the house and the rest maybe an R7. Will not seal as well as blown in and I am sure I can get used blue board which would be cheaper. But not as tight as blown in.
Expanded Polystyrene Foam
R value of 3.6 to 4.0 per inch of thickness
Extruded Polystyrene Foam
R value of 4.5 to 5.0 per inch of thickness.


Spray foam insulation Closed Cell (seems like this is what people used for foundations).
would seal an air leaks getting in now and I assume mice leave this
stuff alone unless it is in their way? One inch is I think R7 so 2 inches
on the back wall would give me what I need.

I talked to someone recently and they said for open cell plan on a $1 a sq foot? Does this sound reasonable. We finally had some snow and I took the tractor and loader and dumped some of snow banks on the back of the house to seal an drafts between round bales and stop wind from hitting the house. Wind can be bad here sometimes.

As always would love to hear different thoughts on the subject.

 

[jonyyuma]

How are you going to treat for termites if you cover the inside block walls? Jy

 

[KB9UDE]

We used 2" sheets of foamboard. I just lean them up against the inside of the blocks and used concrete blocks to hold it up. Cut to fit from concrete to bottom of floor joist. Easily removed for future work if needed.

 

[PILOON]

Sprayed foam is the absolute best.

To go economical you can attach blue or pink foam boards using plastic washers but for a first rate job U then get the foam guy to spray shoot all the seams and joints for total job.

If not too many seams or gaps you can always use spray foam in cans but it adds up fast.

 

[Milo]

I'm not sure I'd permanently seal and insulate your crawl space walls. I'd certainly close vents to seal off any air infiltration in the winter months.

FWIW When building my home I asked about insulating the crawl space. What I was told by an insulation/HVAC designer was to "insulate the outer envelope of your conditioned structure tight and well". With a crawl space this conditioned area would typically be your home's walls, ceiling, and floor. Any areas beyond this should not have insulation and be able to vent and breath (especially in the summer). This includes the crawl space and attic.
As an option one could expand the conditioned area by omitting insulation in the floor or ceiling, instead insulating the basement or crawl space walls, and the roof. Naturally the attic and crawl space would then be non-vented and a similar temperature to the rest of the home.
He strongly recommended using a foam insulation to completely seal as well as insulate. In the attic 12" was sprayed down on the ceiling covering the trusses as well as the cavities in between. For the crawl space 6" was sprayed around the rim and in between the joists, as well as over all duct work.

 

[Craig Clayton]

If you have insulated the floor then what will you gain by insulating the walls of the crawl space. Any heat that escapes from the floor is passing down to a lower temp crawl space which is next to the outside temps. In the high arctic the houses site on piles on perma frost and the floor is insulated.
I think some blue board type would be helpful but the temperature difference to the crawl space will not make a hugh difference.
Maybe add a bit more insulation to the floor.
Craig Clayton