Results 1 to 11 of 11
  1. #1
    Join Date
    Jan 2004
    elsewhere here, I've posted re: red-doing our heating to radiant.
    but the bigger problem as has been pointed out to me by several contractors is the lack of insulation under the ground floor.

    it's very tight crawl space. what are thee possibilities of spray foam?
    would I be better of with Icynene or something else?
    I'm in the NYC area. The floor is about 800 sq ft of somewhat accessible space.
    2x6 joists, 24" oc.

  2. #2
    I do insulation installations in your area. I don't wan't to break a forum rule by giving you contact information here. I am doing a crawl space where I am turning it into a semi-conditioned space. I am using spray foam around the foundation and insulating the floor joists with cellulose.

    Urethane foam is very expensive, but easy to use.

  3. #3
    Join Date
    Jan 2004
    in speaking with a insulation contractor in the area, he recommends first doing the boiler and zone work to see if that makes a difference. Rather then spend the $2500 on insulating the crawl space.

    He would insulate with untreated fiberglass, blown in.

    He says that the heat loss thru the crawl space (provided the rest of the house is done right) is only 3% or so.

    What say on the accuracy of this info? I can't find any ref at DoE or the like, as to actual % loss.

  4. #4
    3% of what? 3% of the total heat load?

    Crawl space heat losses depend on a number of factors. Biggest is how tightly sealed the space is. Older homes, in particular, get a lot of air leakage around where the sill plate meets the foundation.

    I would have to inspect the space before I could get anywhere near providing an estimate as to what the heat losses are.

  5. #5
    Join Date
    Feb 2003
    read at

    I insulated the WALLS of my crawl with 2" tk Styrofoam, ground was | is covered with pvc --

    Is contracting proposing to blow cellulose on floor? then cover it with?

    read other threads herein -- I have several posts on this --

    run the load calc from this site, then you will know what is giving you the biggest losses -- but, you have to read a ruler --
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  6. #6
    Join Date
    Apr 2002
    Several years ago, during the Texas Mold Crisis, we were hired to remove cellulose from the crawl space of a home because humidity in the crawel space had made it moldy. Big house over 5000SF of foot print. Mold had totally contaminated it. Clean up cost over $140,000 then we sprayed rigid polyurethane where the cellulose had been removed, to act not only as insulation, but to incapsulate any mold we missed. Spraying the insulation and placing a vapor barrier added another $25000.

    Isonyne is not good either, because it is water soluble and although it will not grow mold, the dirt imbededed in it will after it gets older.

    Insurance paid our bill, but they pursued the original builder and the insulater for reimbursement.

    No good deed goes unpunished.

  7. #7
    Join Date
    Nov 2003
    northern mass
    Isonyne is an open cell foam....nice and soft to the touch like memory pad on high end matress. You want a closed cell foam for your application. It hardens up, and would seem to be the choice.

  8. #8
    Join Date
    Nov 2004
    SW FL

    Confused Closed cell

    Originally posted by fritzl
    but the bigger problem as has been pointed out to me by several contractors is the lack of insulation under the ground floor.

    would I be better of with Icynene or something else?
    he floor is about 800 sq ft of somewhat accessible space.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  9. #9
    Join Date
    Jan 2006
    Heat transfer from the occupied space into the crawlspace will be negligible, but that's irrelevant.

    What is relevant is running hydronic or radiant lines through the crawlspace. In this case, system efficiency drops by far more than 3%.

    What is also relevent is the pressure balance that occurs through the crawlspace: the crawlspace acts as the source for cold air, which is used to replace hot air lost through the attic due to stack effect.

    All foam plastics & wet-sprayed cellulose, when installed in the crawlspace or lower floors, improve whole-house performance by reducing the volume of air that can be lost through the attic.

    Closed-cell vs open cell suitability is based on thermal expansion rates (closed cell are not designed to resist large thermal expansion or wood expansion, and can crack) and moisture drive. Closed cell are great exterior vapor barriers for hot humid climates.

    Yes the sprayed in foams are expensive. But that's why they all qualify for reduced R-Value requirements and EPA credits.

    [Edited by marcus12 on 02-10-2006 at 02:26 PM]

  10. #10
    Join Date
    Feb 2003
    If you're going through the expense of radiant floor and need insulation, think warmboard or easyfloor. Leave the crawl as is and insulate from above.

  11. #11
    Join Date
    Feb 2006

    run the numbers

    I did considerable renovations on a crawl space of a rental property last year. Prior owners had put some fiberglass in there and it was a mess. Most had been wet throughout its life and sagged and/or molded. Basically, it was worthless.

    Construction will make a huge difference. Is your subfloor tight? In this space, you could see light around the edges and the drafts in the living space were horrible. Heat loss was definitely significant.

    what's your climate? Is the crawlspace vented? Is the floor dirt? Do you have water problems in there? In NYC, you experience a god amount of cold...

    Do some basic heat loss calculations. For example, assuming you don't have air leakage through the floor (huge assumption), if your house is 70F, your crawlspace is 40F and the wood floor has no insulation (~R1), you're going to lose:
    (70-40)*800 = 24000 BTUs per hour.
    That's serious loss and quite realistic for a ventilated crawl space. If air infiltrationis bad or temperature colder, you would further significantly increase losses.

    In the unit I referred to, the floor was always cold and the unit was drafty. Sealing air leaks helped some. Insulating under the floor and using an air-tight radiant barrier under the joists helped tremendously. The unit was vastly more comfortable.

    Again, running the numbers, if you just put R10 whatever in (fiberglass, foam board, PU), you'll reduce the non-filtration loss to 2400 BTUs/h. The big gains for PU will be air infiltration control, high R-value/inch and ability to stand up to moisture. The numbers show that you don't need to go crazy with R value (though with radiant, you'll want to run the numbers with that temperature, not your room temp).

    You might consider other options too. My big concern in a crawl space would be moisture. Whatever you do needs to seriously consider that. I've seen several serious examples of water damage affecting the structural integrity of houses when moisture wasn't adequately considered.

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