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Community and Q&A

Insulating cold bedroom not in building envelope

ChrisTrollen | Posted in Energy Efficiency and Durability on

My wife and I recently bought a brick, 1925 Victorian twin in Philadelphia. It has 3 floors + attic, but the 3rd floor and attic spaces do not extend over the top of the bedroom at the back of the house. We are planning to use this room as our main bedroom but it is significantly colder than the rest of the house.

I’ve been reading as much as I canon GBA and many other site and online videos, but I am at a loss to know how to improve the comfort level in the room.

There is no wall insulation as far as I know and the walls I believe are plaster (with the possibility of some drywall patching replacement.

I think I understand why it is so cold as the room (ceiling/ roof and 2 exterior walls) are basically outside the building envelope (please forgive me if this is the wrong terminology). i’m also assuming it will be a sweat box come summer (although we are lucky to have central air!)

Short of ripping the walls down to add interior insulation, which I am not sure is even a good idea based on many things I have read online, I don’t know if the situation can be improved. I am attempting to air seal as much of the rest of the house as I can from the basement up (which is a task unto itself as actually accessing the rim joists is near impossible due to all of the pipes and wiring added throughout the years.) adding additional insulation to the attic will hopefully help the rest of the house.

Do we just grin and bear it, or is there something practical that will not break the bank that can be done?

Many thanks!

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  1. GBA Editor
    Martin Holladay | | #1

    There are at least four ways to make this room more comfortable:

    1. You can improve the heating system and cooling system that serves the room. What type of heating and cooling system, if any, does the room now have? If you do this, you can be as comfortable as you want (although the energy cost might be high).

    2. You can perform air sealing work to limit infiltration and exfiltration.

    3. You can insulate the floor, walls, and ceiling of the room.

    4. You can replace the existing windows with high-performance windows.

    Insulating walls and ceilings isn't that complicated. Techniques have been developed to add insulation to older houses without removing all of the interior plaster or drywall.

  2. ChrisTrollen | | #2

    Hi Martin,

    It's steam radiator heating and the AC is a high velocity 2 zone system. (and you are right the heating cost is very high which I would like to get under control)

    I've started to do air sealing but I'm so new to this I am not really sure how to start on individual rooms. Should the baseboards be taken off as there are significant gaps where the plaster wall ends and the floor boards meet, and I am not sure how to efficiently do this without ruining the really lovely floors we have - I do not want to use expanding sprayfoam as it just never seems to do the job without a total mess - any guidance on how to tackle the air sealing?

    While this is an old article it's one of many that I've read deterring people from adding wall insulation to an older home it's all very confusing.

    Many thanks for any further guidance or resources!

  3. GBA Editor
    Martin Holladay | | #3

    Is there any way to control the heat in this bedroom -- a thermostat or radiator valve?

    If the bedroom is part of a single-zone system that includes other rooms, and the bedroom is colder than the living room, maybe you can simply get a plumber to add another radiator.

  4. GBA Editor
    Martin Holladay | | #4

    If you aren't familiar with air sealing work, you might want to hire a home performance contractor to do the air sealing.

    Most older homes can be safely insulated. If you know how your walls and ceiling are built, you could describe how your house is built so we can help you.

    For example -- and I'm just making this up:
    From the outside in:
    Clapboard siding
    Asphalt felt
    Board sheathing
    2x4 studs
    Lath and plaster

  5. ChrisTrollen | | #5

    Hi Martin,

    I hadn't actually thought of adding a 2nd radiator. It is a one zone heating system and the old cast iron radiator does have a valve on it. I was hoping to get the house to a more energy efficient state through out. I'll keep (literally) plugging away at the air sealing.

    But a 2nd radiator is definitely something to consider.

    Many thanks!

  6. ChrisTrollen | | #6


    I believe it is 2 layers of bricks, There must be studs and then lath and plaster. I cannot be sure if there is any board sheathing, but my guess is not.

  7. GBA Editor
    Martin Holladay | | #7

    Your best bet is probably insulating the ceiling (plus the air sealing work, of course, and maybe installing storm windows).

    Here is a link to an article about insulating the walls of older brick buildings: Insulating Old Brick Buildings.

  8. ChrisTrollen | | #8

    Thanks Martin - I did spot this article, but I'll read it again in more detail.

    thank you!

  9. Expert Member
    Dana Dorsett | | #9

    Is it 1-pipe steam or 2-pipe? (If you don't know, post a picture of the radiator.)

    Bob Yapp's article is an embarrassment full of misstatements of fact, and technical sounding words that aren't even words ("condensating", really?) He needs both an an editor, and a building scientist. Don't put a lot of stock in it, since it contributes nothing toward understanding how YOUR wall system works, or how it might be insulated safely (or not-safely.)

  10. ChrisTrollen | | #10

    Hi Dana,

    It's a one pipe steam system. There's so much information out there - much of it contradictory - that it's hard to know how to proceed!


  11. Dana1 | | #11

    With 1-pipe steam sticky or clogged radiator vents can dramatically change the heat output of the radiators, and can upset the room to room temperature balance. If the cold room's radiator vent is at all suspect, swap it out.

    For a bunch of money you could install thermostatic radiator vents on all or most radiators to be able to tweak the balance. This isn't cheap, on the order of $100/radiator if you hire it out, $60-70/rad as a DIY, but it's probably still probably cheaper than adding a radiator or swapping out for a bigger radiator.

    Taking this a bit afield, almost all steam systems are more than 2x oversized for their actual loads with the windows closed (a policy artifact of the Spanish Influeza pandemic of 1918, where it was thought that over-ventilating by keeping the windows open would limit the spread of the disease.) As a result of the oversizing factor many/most house became uncomfortably warm with the windows closed, and people began painting the radiators with silvery or gold low-E paints to reduce the radiated heat transfer, &/or started covering them up with restrictive enclosures to limit convective heat transfer. If the radiator in the cold room has a metallic color paint, re-paint it with something more emissive (almost any non-glittery color except bright white will perform about the same.)

    If there's space for it, slipping foil-clad sheet of anything (1/2" polyiso) between the radiator and your brick will also improve heat output and reduce heat loss from the room due to the low thermal performance of the brick and the very high temperature difference between the air convecting through the radiator and the outdoor temps.

  12. Expert Member
    Dana Dorsett | | #12

    When sorting out apparently contradictory information it's important to vet your sources. Bob Yapp is all about historic preservation, and has a strong bias toward "If it survived 100+ years don't mess with success by trying to change it." type thinking. Building scientists (including but not exclusively those at the Building Science Corporation) run a deeper analysis of where the potential problems are, and actually measure & test stuff to determine how well the modeled theoretical basis matches real world data. Many of his stated problems are well understood, with well evolved solutions.

    Most of what Yapp on the blog page in the link was specific to wood framed structures. The whole business about how & why paint failures can occur after such a building is insulated is far from "unexplained", as asserted in the article- it's WELL understood by building scientists. Removing the insulation may solve that issue, but it's rarely the RIGHT solution in a resource-conscious world. It's clear from the article that Yapp is fairly clueless about the difference between air permeance/air leakage and vapor permeance, or where & when vapor barriers are appropriate (or not.) He's also simply misinformed about the ability of cellulose installers to control the pressure and prevent blow-outs, etc. (Just because some drivers run red lights isn't an indication that drivers in general will do so.) He's correct that air infiltration is a bigger issue than raw R-value in many/most older framed houses, but he's missing big pieces of the puzzle around insulation and vapor diffusion. His broad recommendation for use of vapor-barrier paints will help in some instances but can hurt in others. The notion that " There is no reasonable payback to blowing insulation, foam or dense pack into the plastered sidewalls of your old or historic house." is just plain BS. Done right, there's plenty of "payback", though done poorly in an ill-advised stackup it's also true that "This practice has truly been the ruination of many of our historic central city homes."

    All of which is IRRELEVANT for double-wythe brick wall construction. Most double-wythe brick construction has furring to support the lath & plaster, not studs, which limits your options. If there are indeed studs, behind the plaster & lath and not merely furring, there may be safe opportunities for improving the thermal performance of the wall short of gutting it, but we would need to know the layering stack up of the wall. If you can find some places to drill exploratory holes to figure out the stackup it would be possible to advise more specifically.

    In the mean time, I'd be surprised if the existing radiator isn't big enough to heat the room twice over with 215F steam. But if the room by room radiation isn't proportional to the room loads you'll have to develop a strategy for balancing room temps on a single zone system. Thermostatic radiator valves would be a start, but you may also have to change where the system thermostat is located as well.

  13. ChrisTrollen | | #13

    Hi Dana,

    Thanks again for such a detailed answer. I guess as this is our first home I am hesitant to do anything that will have adverse effects and you are right I am intimidated by the fact the house has existed for nearly 100 years and I don't want to be the owner who screws it up!

    I'm trying to deal with the air infiltration and leaks and I've included some photos of what I think is pretty typical behind the baseboards - how do i deal with this? Particularly on the external walls?

    As I mentioned previously gaining full access to all of the rim joists in the basement is basically impossible.

    Thanks again!

  14. Expert Member
    Dana Dorsett | | #14

    First, with a hole saw /other,n carefully remove some of the plaster to get a better peek at the wall stackup. If you open up a 2" hole and peek in with an eyeball or boroscope and all you see is brick an inch or two away it means the lath is supported by lath, and there are no studwalls. You may be able to figure some of it out probing in there with a stiff wire (like a cut wire clothes hanger) or thin screwdriver.

    In the basement where you DO have access to the joists, take a look and see how the floor joists & rim joists (if any) are being supported at the exterior wall.

  15. GBA Editor
    Martin Holladay | | #15

    Use canned spray foam. Then replace the baseboard.

    The baseboard can be caulked in place if you want -- with a bead of caulk between the baseboard and the flooring, and another bead of caulk between the baseboard and the plaster wall.

  16. ChrisTrollen | | #16

    Hi Dana,

    I'll check again tonight but when I used a flashlight to look into the bigger hole in the photos I'm almost sure I could see red brick as you say a couple of inches away.

    Martin - thanks. I didn't think I could add caulk between the baseboard and the actually flooring due to the floor expanding and contracting - is it best to use 100% silicone caulk for this? something more flexible?

    Thanks very much to both of you for taking the time to answer my newbie questions!

  17. GBA Editor
    Martin Holladay | | #17

    I have seen weatherization contractors use clear silicone caulk in this location. Silicone caulk is flexible enough that you don't have to worry about the caulk limiting movement in your floorboards.

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