Cold floors/crawlspace

[Henz]

Since I would say that most of us dedicated wood burners are anal about heating our homes, does anyone have any suggestions for insulating under floors within crawl spaced?? I can get my house at shoulder height up to 90 degrees but when you are laying on the floor its about 60..any thoughts or suggestions would be appreciated..I have an old 1800's homestead with layed up rock foundation.. hand hewed beams irregular widths so you cant simply put in fiberglass ins etc...

 

[Roospike]

Ceiling fans , insulation & dont forget to wrap your water lines and also wrap with a electric pipe heater.

 

[Henz]

yeah I guess ceiling fans but my ceilings wont allow it..way too low. really old house remember.. I ahve found that when I have my blower on and am trying to circulate warm air around I am actually pulling cold air through drafty spots in the floor and cills...Its a never ending problem for me..but I ahve to do something about that crawlspace and floor...

 

[Roospike]

How tall is your ceilings ? my house is late 1800's with the rock foundation and has 7'11" ceilings and i put in ceiling hugger fans X 3

 

[Henz]

try like 6' 5" tops

 

[Roospike]

try like 6' 5" tops

WOW..............

How about a blower fan that tilts 90° and aim it at the ceiling to move the air around.

 

[Henz]

might work, but hte bigger probelm is getting some insluation in the floor and keeping the draft down

 

[BrotherBart]

yeah I guess ceiling fans but my ceilings wont allow it..way too low. really old house remember.. I ahve found that when I have my blower on and am trying to circulate warm air around I am actually pulling cold air through drafty spots in the floor and cills...Its a never ending problem for me..but I ahve to do something about that crawlspace and floor...

A lot of that cold air isn't leaking into the house. It is the colder air in the house being displaced by the heat, dropping down to floor level and being pulled back to the blower and the stove intake.

 

[Henz]

maybe alittle but put it this way, I can hold match to my sill and on a windy day it will blow out

 

[sailor61]

I had a similar problem - house is/was/will be in a flood zone very close to the water. As such my bedroom - which was an addition - was not on a foundation it was on pilings. The floor joists were insulated with fibreglas bats - which seemed to only serve as bedding for the local rodents no matter what I did to seal it off. On the rebuild I'm using sprayed in open cel foam, seems as if that should deal with some of the draft problem as well as the critters. Not the cheapest stuff in the world, but cost to insulate entire structure (including floor in this one room - rest of the place was on a pre-flood code foundation and is going back on it) is around 3400. 'glas quote was around $1200.

 

[Henz]

where would one find such an outfit that does this sprayed on foam..I thought about that the other night as I was laying on my back staring under the floor thinking how in the hell I was gonna do this and remembering an episode of "This Old House" where the master carpenter guy said tht he only uses sprayed in foam for everything now..

 

[sailor61]

I did a google search for something along the lines of "sprayed foam insulation RI" and came up with several local firms. I think the brand name for the foam that's being used on my place is something like "isocyanene" and they do have a national web site that lists all the local branches/franchises

 

[tutu_sue]

Here's is a link to information on weatherproofing your crawlspace: (broken link removed)

First, try sealing the sill plate and all plumbing, electrical etc. penetrations into your house from the crawl space. If that doesn't do it for you, then you may want to insulate the ends of the joists (aka rim joist and band joist) above the foundation. Finally, you can consider insulating the interior crawlspace walls. Based on the type of foundation and joists you have, you can insulate using foam board insulation (Option 2) on the inside of the rock foundation. Taking measures to control moisture before installing insulation is vital to long term success.

Good luck and keep us posted.

 

[budman]

That stuff come,s with a heffty price tag but realy does some hell of a job. :snake:

 

[sailor61]

The thing that really appeals to me about it is that it is moisture resistant and does not require a vapor barrier. As such I don't have to vent the roofline etc

 

[Henz]

wait a minute. so you are basically saying that I should run foam board insluation parallel to the rock foundation and not tack it up on the underside of the floor??

 

[Rhone]

According to my energy books, the right method is to use XPS. Fiberglass would be the worst possible solution, a 1% air space around fiberglass will reduce it's effectiveness 30-50% and under floors it's almost impossible to install it correctly, without air gaps or channels forming.

My energy books say the proper method for crawl spaces is

1.) Caulk or use insulating foam to first seal any air spaces between the plank as they pass through the floor joists & support beams. Caulk is preferred, basically, go down every floor joist and where there's a space between the planks, fill it. You only need to fill the small spot above each floor joist where the planks are seperate.

2.) Once that's done, the best material is XPS that's Extruded PolyStyrene. Probably 2" thick, it's the baby-blue if made by DOW or light pink foam board if made by Owens Corning (foamular is the the same). Best to get the 4' x 8' pieces.

3.) Measure each 8' space looking for the shortest distance. If it's 14 1/2 you want to cut the next piece 14" to leave a 1/4" gap or more on each side. I prefer to cut it with a Skihl saw 1 1/2" deep and snap the rest like dry-wall with a push down until you hear it pop and then a lift up to finish, a table saw can also easily cut it but I find the table saw likes to grab it, or bite pieces out of it and dangerous. Happens everytime with me, meanwhile my father has cut as much as I have on the same table-saw no less and never happens to him.

4.) Fit it in place, tight against the subfloor as possible and shim it so it stays without holding, then take either expanding foam spray and spray it as deep down in the openings on each side (best method but also expensive) or caulk down each side.

Rinse, repeat. If you want to really do the job then...

1.) Follow step 1 above

2.) Cut and adhere each piece of XPS so that it completely covers the bottom of the floor joists, probably best to go perpendicular to joists.

3.) Rent a blown cellulose machine, and the wall nozzle attachment

4.) Cut a small opening in the XPS, saving the piece and dense pack the cellulose in the cavity.

5.) Put the piece back that you removed, and caulk it in place so that it keeps an air tight seal.

I included pictures of both methods, in the best possible scenario I didn't draw the XPS perpendicular to the floor joists like I should have. I didn't want to redo the picture.

 

[Rhone]

wait a minute. so you are basically saying that I should run foam board insluation parallel to the rock foundation and not tack it up on the underside of the floor??

That saves money & time and is an improvement but isn't as good as tacking it up underside of the floor.

 

[Henz]

I was thiking about doing the #2 at first. This is becuase I have piping that runs under it and if I ever needed to access it that blown in insulation would be tricky..I wounder if jsut tacking the foam directaly to the subfloor would be ok?? meaning my joists are hand hewn and some span a distance of 4' or more..

 

[Rhone]

I think I tried to show that as option #1 the (easy.gif). If you mean tacking it below the floor joists like my picture #2, but skip the cellulose that will work as well but you really have to make certain you stop air leaks before tacking it in place. That will give a dead-air space which will give a little bit of added insulation, and also prevent short circuiting of the cold through the floor joists. The key will be how well you caulked any possible air leak beforehand and caulked/sealed the XPS afterward. You'd have to make sure there isn't a pathway for air to sneak in around the perimeter and pretty much nullify the insulation. I think it won't be possible to do #2 but skip the cellulose cause it's just too easy to create a wind tunnel.

 

[Henz]

I guess doing anything to stop the air leaks will be better than what I have now...I will look at it again and go for it.. thanks for the help

 

[wg_bent]

Go here and do a search on Crawl Space.

Lots of information. Look at best practices, and top 10 dumb things. You'll find it almost funny that most houses are not built properly.

(broken link removed to http://www.buildingscience.com/search.htm)

Oh, and by the way...Rhonemas's post looks spot on.

 

[jjbaer]

Another thought:

Last year I put R-19 fiberglass on the underside of my floors in my crawlspace. Before I did this however, I realized that installing insulation makes it difficult to visually inspect wood for termite and other damage. So I heavily sprayed every board AND the underside floor boards with Boracare, the #1 timber treatment. It's not the preventive stuff but the strong stuff that kills bugs already in the wood and others that will eat it in the future! Then I insulated and have no worries about future damage.

I bought my insulation at Lowes and got low prices and 2, $75 rebates. A friend of mine got 5, $75 rebates, the max for this.

 

[Henz]

huh...well, I am definately going with rigis foam, however, I would love to do the spray on foam if I can find a place locally that does it

 

[kevinmoelk]

Old houses, gotta love them.

I'm in the process of insulatiing my floors as well. Rhonemas is correct. Hope I spelled your name right. The thing to do is to seal the gaps in the subfloor with caulk or spray foam. Then place styrofoam (blanket term, lots of options here) sheets between the floor joists and fill the gaps with spray foam as suggested. After that is done, add a seond layer of styrofoam on the bottom of the floor joists. I'm using screws with fender washers so these panels can be easily removed for any future plumbing or electrical service. Then you can tape the joints with tyvek tape or some other suitable tape. The dead air space inbetween is a great insulator.

I would strongly suggest not to use any blown in cellulose or fiberglass insulation in the lowest floor of your home. Particularly if your crawlspace has a dirt floor, which many old homes do. Moisture problems, rodent problems, etc.

Foam would be great, but foam is NOT rodent resistant. They can chew through the stuff if they want to, and I have several holes in my garage as proof of that. Besides it's lack of rodent resistance any future mechanical work is going to be that much more difficult if you have to tear a bunch of foam away.

I'm also wondering how the crawlspace is vented. Has anyone added vents? Do you have any moisture problems? Do you block off your vents in the winter time or reduce their size opening?

As for the sills, to block rodents you can use 1/2 hardware cloth and staple this up all around your sills, essentially creating a little fence for the critters. But this will only serve to greatly reduce the chance of rodents entering your home. I've never known any old house that a mouse couldn't find SOME way inside.

-Kevin