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Community and Q&A

Insulating a 1960’s house with no room in wall for insulation

Merlyn614 | Posted in Energy Efficiency and Durability on

I have recently bought a house in south-eastern PA. The first floor exterior walls are brick & block (4″ cinder block). I took down wood panelling in the family room and found that there was no dry-wall behind the panelling on the exterior walls. In addition to this, there is no insulation or room for insulation. After the cinder-block, there is about 1/2-inch of space and a thin foil vapor-barrier. I’m at a lose as to how to insulate this room properly without losing precious interior space. In addition, most likely the other first-floor rooms (which have dry-wall) also won’t have any insulation behind them or room for insulation. Is there anything I can do to insulate those rooms without removing the drywall and making the rooms smaller? Is it worth insulating the one room that I took the wood panelling down in if I can’t insulate the other rooms (I really don’t want the expense of removing all the drywall to insulate and put it back up again).

Thanks for any and all advice!

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  1. GBA Editor
    Martin Holladay | | #1

    The best way to insulate this type of building is with exterior insulation. The easiest approach would be to install EIFS (rigid foam plus synthetic stucco). If you call up a local EIFS contractor, you can get an estimate for the cost of the work.

    Of course, this work will change the appearance of your house. Instead of exterior brick, your house will have a stucco-like finish.

    If you want to keep the exterior of your house unchanged, then your other option is to install interior insulation -- either rigid foam or spray polyurethane foam. Of course, this insulation will take up interior room, and will make your rooms smaller.

    There is no free lunch. The insulation has to go somewhere.

  2. DellStator | | #2

    As Martin says, no free lunch space wise.
    1. If you have NO wall insulation, I have to wonder what's overhead. Is there an attic? If there is less than a foot of insulation, put more insulation up there first. If it's a flat roof on joists, what's between the joists. Blown high density cellulose would be a great solution / add on in both scenarios. If it's a concrete slab with no insulation, I hope you have head room for a suspended ceiling - and make sure it's strong enough for the insulation with NO sagging in the panels.
    2. Check for drafts / air leaks and seal all those.
    3. For the walls, I'd say if money is really tight, since you have NO insulation at all, ANYTHING will help ALOT, a DIY job with 1 inch of high tight fitting (no air gaps) density glass wool (R-4.2, 1 inch 4pcf Thermafiber is one) behind new inside GB, (Spacers on the furring to get out to 1 inch will help on thermal bridging) could pay back and 2 yrs.

    I'll toss a few more factors to consider that might point the way to a more inclusive solution.

    1. The big cost is not going to be insulating / insulation, so whichever, insulate big to maximize "returns".
    2. How much money can you spend insulating? If you don't have over $10,000, then you aren't likely to be working outside. Inside, as you alluded to, you can do one room at a time, as you have the money.
    3. What is the value to you of related improvements insulating will achieve. This isn't an economic calc, it's emotional calc. like, "Wow, and the house will look GREAT too! "
    4. The longer you keep the place, the more insulation and realted work you can justify, economically and emotionally, but even flipping, a 10 yr payback is a good idea as energy savings, and related improvments will be a selling point.
    5. DIY or contracting out? Working inside is probably more forgiving of time / ability issues. For reference, as a DIY'r I'm middling, and you can see at what it's taking me to heavily insulate an old house (hint - A LOT of work).
    Good Luck

  3. Expert Member
    Dana Dorsett | | #3

    The half-inch air gap plus foil probably brings the whole-assembly R up to about R3-4, but it's clearly not enough to provide much comfort at the temperature extremes.

    I'm with Martin- an exterior foam-over approach is the right way to go since it's cleaner (you can live in the house while it's being done), and more likely to yield a continuous thermal envelope, with no hidden thermal bridging.

    In addition to the walls, it's probably worth doing a "chainsaw retrofit" and extend the foam over the roof as well. If taking the low-cost EIFS approach it may be worth using 3-4" of unfaced EPS R12-R16) on the walls and 2.5"-3" (R15-R18) polyiso for the roof. For EIFS to work as a retrofit on a brick clad house with impermeable foil on the interior requires that the brick become the drain-plane, and you'd probably want to use a spray applied weather resistant barrier (WRB) for better moisture control in that none-too-dry climate. The vapor permeance of EIFS isn't all that great (most are under 2-perms, not counting the foam, some are under 1-perm), and in rainy climates that can become an issue. You can't allow the brick to become saturated or any wood in contact with the brick can run into rot issues. Deep roof overhangs can mitigate the incidental rain-wetting and some of the bulk-moisture issues, but it won't deal with ground moisture wicking.

    With the interior foil layer you may want to consider using 3-4" of unfaced low density Type-I EPS with a rainscreen gap between the EPS and siding, since EPS is semi-permeable, and the brick can always dry toward the exterior. Unless you re-mounted all the windows & doors to bring the flashing out to exterior side of the foam, you'd still need to use the brick as the drain plane layer, probably still with a liquid-applied WRB.

    With R15+ above the roof you can safely air-seal the attic and insulate the under side of the roof deck. This is easier to get right than air-sealing at the attic floor. With older homes with thin joists & rafters it can be hard to get enough attic R at the floor level in the first place, at least out over the exterior walls, which creates a thin-spot, heat leaks at that end of the roof, which all too often creates ice damming issues after winter storms.

    None of this is super cheap, but neither is heating & cooling an unisulated house in climate zone 4. It's worth checking to see if there are subsidies available through the state or local utility for this type of work to take the sting out of it.

    Edited to add: When using a liquid WRB in a foam-over where there is an interior vapor barrier, it's important to choose one that is vapor permeable (some are, some aren't) eg:

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