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Old field stone foundation

Oakleerulez | Posted in General Questions on

I have an 1850s brick house that I recently moved into.  I live in a very cold part of NY and I am trying to reduce my energy consumption.
My basement is damp, not overly wet, but by no means dry.  3/4 of the basement has a poured slab, the remainder is dirt floor(covered by plastic).
My plumbing, furnace, hotwater heater are all in the basement, but it is by no means a finished (nor will it be) 

Realistically I would love to just spray closed cell foam around the rimjoist and fill in any obvious gaps around the top of the foundation walls, but the cost to do that is approx 450$, which is not bad, but there is a 1000$ minimum for the sprayfoam company to come out.

The spray-foam company suggested/quoted me to do the basement ceiling to minimize the amount of cold air being sucked out of the basement.

Would sprayfoaming the entire field-stone wall be a better choice(or even just a few feet down)? 
Are there any negatives to insulating the basement ceiling if it will not be a finished space? I love the idea of keeping the cold/moisture in the basement where my dehumidifier can take care of it.

Thanks in advance for any suggestions.

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  1. GBA Editor
    Brian Pontolilo | | #1

    Hi Oakleerulez.

    All that you are considering is acceptable. It is common to install spray foam to old stone foundations if they are solid, without loose stones, and are not leaking water. It is also okay to install spray foam between the joists of the floor. However, if your were going to go that route, I wonder if you could save a lot of money by insulating your rim joist and floor with cut-and-cobble rigid foam insulation, which is an easy do-it-yourself project. This is what cut-and-cobble means, if you are not familiar: Cut-and-Cobble Insulation

  2. Oakleerulez | | #2

    Thanks Brian,
    I had thought about that as well, but have not priced out the cost. I will definitely give it a stronger look now that I know it is acceptable to insulate the basement ceiling. Assuming I go this (insulating the ceiling route) will there be any other special considerations that I need to know? I am assuming moisture will be "trapped" in the basement so I will need to run a dehumidifier and in the coldest months I may need to heat it.
    Also, if I did cut and cobble with foam board, wouldnt that surface need to be covered as well? (for fire protection)

    1. GBA Editor
      Brian Pontolilo | | #3

      You'll have to decide how you want to proceed and may want to consult with a local builder experienced with old houses and energy upgrades. With all of your appliances in the basement, I wouldn't abandon the idea of insulating the basement too soon. Have the foundation evaluated.

      If you do insulate the floor, how much moisture will be "trapped" depends on the type and thickness of the insulation you end up using. In any case, you can monitor humidity levels in the basement and in your home and dehumidify as needed.

  3. hughw | | #4

    I'm an architect and approach a lot of things on an analytic level rather that with real field take what I say with a grain of salt.

    I would be nervous about insulating basement ceiling. I'm assuming that the contractor in talking about cold air being sucked out of the basement means that you're getting cold air int the house from the basement. That may well be true, and if there any particularly large pathways creating a cold draft you might want to seal them. But the floor above is actually transmitting (losing) heat to the basement. That heat is keeping the basement somewhat warm and above freezing temperatures. If you isolate the house from the basement, the house might be more comfortable, but basement plumbing may be subject to freezing without heat wraps and other measures. If it was my house, I would probably spray as much of the basement wall as my budget allowed.

  4. Expert Member
    Dana Dorsett | | #5

    Insulate the foundation walls, not the attic ceiling. IRC and NY code min would be R15 continuous insulation, but even 2" of HFO blown closed cell foam (R14-ish) all the way from the rat-slab up the wall over the sills & band joists and up to the subfloor would make a huge difference.

    If that's too pricey, 2" on everything from 2' below grade on up to the subfloor would be a very good start.

    Insulating JUST the attic ceiling would indeed increase the frozen plumbing risk as Hugh points out, and in rare instances risks frost-heaving the slab & foundation.

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