Insulating the floors

[charlz]

My house was built with a vented crawlspace where they insulated the foundation walls versus the floor. I guess the theory now is to do that for unvented crawlspace but a vented crawlspace should have the floor insulated. I am tired of hearing about cold floors in the winter months so thought I would investigate getting the floors insulated.

I priced out the material at HomeDepot so I would have an idea of what that would cost. I then requested quotes from 4 different insulation companies. So far I have gotten 2 bids back. One over the phone (based on sq ft from the house plans) and the other the guy came out to look at it. To my surprise the quotes are all less than it would cost me to buy the stuff and do it myself Only real difference is they are spec'ing unfaced batts and I priced out faced... is there really that much price difference?

I watched some videos from the Home Depot site on insulating crawlspace floors and they recommend sealing the band joist seams where they meet the floor. How critical is that? I sealed all the floor penetrations so I am reasonably sure the band joists were not sealed.

The floor is 1817 sq ft, 11 7/8" joists on 16" centers. There is a vapor barrier installed over the dirt. I got quotes for R19, R30 and R38. The guy that came to the house said while insulating the floors will improve 'foot comfort' it likely won't make much of a difference on my energy bill. Opinions on R38 versus R30? It is about $200 difference is all.

The guy that quoted me over the phone also let me know that our power company is giving $.15/sq ft rebate for attic insulation upgrades. If my attic is R38 and I take it to R50 I will qualify. The rebate would pay about 50% of the price he quoted me to blow in more insulation to bring it to R50. I forgot to ask the guy that came to quote and need to go in the attic and verify what I have. Would the $$ difference between R30/R38 be better spent in the attic or should I really pay for both?

Opinions?

Thanks!

 

[Joe H]

Seal the vents and you'll convert the crawl into a conditioned space.

That will help some, and it's fairly cheap to do yourself before you start spending big bucks on something that may or may not get you what you hope for.

Joe H

 

[charlz]

I did close all but two of the vents a few years ago. They have penetrations through them, dryer vent and outside air to former fireplace. I did not put insulation in the vents to completely seal them. I am a little paranoid about completely sealing it off and possibly having a moisture problem. I go under the house about once a year to have a look-see for potential problems.

 

[dmccarty]

How about spray insulation instead of batt? Batt insulation is almost impossible to get air tight. You can get good enough with batt. We used batt insulation in the walls just so it would be somewhat easy to run wires in the future if we had too. And we have rigid insulation on the exterior was well. Building and these sorts of upgrades are always compromises. We figured batt and rigid was good price performance mix.

The attic is blown insulation and some batt insulation. The batt is because of what the HVAC guy did. I was not and am not happy with what he did but it is what it is.

For under the floor I would look into spray insulation. Good coverage and if you had to rewire/replumb it would not be too difficult. The only negative I can think off would be water leaks in a place like the bath or utility room. Would a leak drain from the insulation?

Later,
Dan

 

[jonyyuma]

I leave two vents open for the winter for moisture and radon gas escape? Have you tested for RADON? It might not be in your area, my house is partially in a hill.I have two layers of plastic, 4 mil and 6mil, under house many posts. I have r30 under floor with the paper up and tiger teeth wires holding it up. once in awhile i have to restake it back up in a section, no reason to fall? just my own 2 cents. I did add the floor insul after living there 10 years and it helped heating bills.Jy.

 

[bdeboer]

I watched some videos from the Home Depot site on insulating crawlspace floors and they recommend sealing the band joist seams where they meet the floor. How critical is that? I sealed all the floor penetrations so I am reasonably sure the band joists were not sealed.
Opinions?

Thanks!

I think you would feel a difference just foaming the band joists with spray foam like Tiger Foam. Try sticking your hand up by the end of joists, you will probably feel the cold air when the wind is blowing.

Check out the buildingsciences.com articles.

RR-0401: Conditioned Crawl Space Construction, Performance and Codes — Building Science Information

 

[Larry Caldwell]

I insulated my subfloor 5 years ago with R-25 unfaced batts. It made a big difference in the liveability of the house. I did new doors and windows and upgraded the attic insulation at the same time, and dropped my heat bill about 50%.

I don't understand about sealing the band joists. They are outside the insulation envelope, aren't they? Leave the foundation vents wide open. In my younger years I made a lot of money fixing rot under poorly ventilated houses. If you have moisture in the ground under your house, a visqueen vapor barrier is a real good idea.

 

[Travelover]

I have had good luck with covering the crawlspace floor with plastic sheathing, sealed to the walls with roof repairing mastic, then closing off the vents and insulating the walls, including over the vents. If you are worried about humidity under there, stick a remote sensor with temperature and humidity capabilities. If you do this, I would seal the rim joists, as this is now conditioned space.

Test and Measurement Products : OMNI Controls Online

 

[ShenandoahJoe]

If somebody's willing to do the insulation for a good price, sign them up. I don't recommend closing up the crawl space. Let the air flow however it wants down there. New Mexicans may not fear the destructive power of moisture the way I do.

 

[charlz]

If somebody's willing to do the insulation for a good price, sign them up. I don't recommend closing up the crawl space. Let the air flow however it wants down there. New Mexicans may not fear the destructive power of moisture the way I do.

We do have a fairly high water table here, no basements in this area. That is sufficient to make me paranoid about moisture.

I was just surprised to find the bids for materials and installation to be lower than I could get the materials for!

I have one more guy coming out today to bid it and then I will pick one and get it done.