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insulating brick houses

Roznne Smith
Roznne Smith Member Posts: 2
I have a large old brick house (1894), with zero insulation. The interior walls are lath and plaster over 2x4 studs. In reading about insulating old houses I read somewhere that it is not good to insulate a brick house, because of the dead air space between the brick walls and the plaster acts like insulation and they also give the house air flow. Also I noticed how warm the brick get when the sun is on it even during the winter. Wouldn’t insulation stop this warmth from warming the house? But everybody says I must insulate but they can’t tell me if this holds true for a brick house. Everything I read only talks about stick construction. Do I or don’t I insulate my brick house? Your input would be greatly appreciated.


  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588

    We have a local guy who injects polyurethane foam in the space between courses. It will take the wall from maybe
    R-3 to R-8, a huge improvement, but still only about half of the current code requirement.

    Superinsulated Passive solar house, Buderus in floor backup heat by Mark Eatherton, 3KW grid-tied PV system, various solar thermal experiments
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,285
    In Europe...

    ... they are doing what's called "Passive House" retrofits. This involves adding thick rigid insulation to the outside of their masonry houses and coating that with stucco or some other cladding. It's a lot of work, but quite effective. Try a search for "passive house" and see what comes up ;~)

    Yours, Larry

    ps. I'll add that this approach would negate nearly all the moisture concerns expressed below. Also, it puts thermal mass inside of the insulation, which would be a plus.
  • Brad White
    Brad White Member Posts: 2,398
    The Jury is still out....

    There is an engineering firm local to us (near Boston) who have determined that older more porous common brick (as opposed to faced brick) buildings should not be insulated due to the ability of moisture to ebb and flow through the masonry itself.

    The principle is that if uninsulated, moisture enters the brick and will re-evaporate as vapor pressure changes on either side of the wall, moving from high to low vapor pressure. Thus if it is dryer indoors, the moisture will diffuse in that direction and if dryer outdoors, that is where the moisture will go. (This also depends on where the moisture is within the wall and through what it must pass to do this.)

    Now, if the wall were to be insulated on the interior, the moisture would remain in the brick and possibly freeze because, with insulation, the wall is now cold, isolated from the heat of the house. Freezing moisture would cause spalling (breaking off of brick due to ice expansion within the wall).

    Naturally this all depends on how cold it gets where you are, how porous is the brick and how much moisture is present. Older hand-fired brick has plenty of variations in porosity and at what temperature a particular brick was fired. Enough variables to play with but the principle is clear, I think.

    Conversely, I have seen older buildings (mill/loft buildings) insulated on the interior without apparent damage that I can see at least.

    I can only give what I have heard and intend to look into this more closely.

    You may also want to check out Building Science Corporation, run by Dr. Joseph Lstiburek for some of his white papers. He also has publications for sale. Good reading and he can use the money to buy a vowel. :)
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • jim lockard
    jim lockard Member Posts: 1,059

    If the bricks were sealed with a paint ? or a good clear sealer and then the building was to set awhile before insulating would that be ok?
  • Brad White
    Brad White Member Posts: 2,398
    Sealing Bricks

    My best sources (architects, building scientists and industry practitioners) caution against sealing brick. The integrity of the coating, eventual wear and tear and never knowing where you have missed a spot are problematic.

    I would think of it this way: If the coating is moisture-impermeable, those properties go both ways- water that ever gets in has fewer pathways out. What is apparently liquid impermeable may also be vapor impermeable and not in any way you could call predictable.

    If you insulate the inside (especially with a closed-cell foam) and seal the outside, I would submit that you would positively be causing water to be trapped within the fabric of the wall -a sandwich effectively- with uncertain but undesirable results.

    My $0.02

    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • gerry gill
    gerry gill Member Posts: 3,078
    Brad, thats a very interesting

    web site you referenced..i think i'll have to procure some of those books he sells..thanks for the info.

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • jp_2
    jp_2 Member Posts: 1,935
    but then......

    all common bricked insulated structures would have brick failure, in the northern climates that is :)

    I'd say insulate
  • Brad White
    Brad White Member Posts: 2,398
    That is

    one way to find out....


    I would say that most inner-city buildings in Boston (Philadelphia, New York for that matter) dating before 1930 -not to mention those remaining from the 18th century-, have faired pretty well, common hand-fired brick notwithstanding and uninsulated.

    Naturally a periodic re-pointing of the mortar joints should be expected. The joints are the main source of water intrusion when mortar is missing. Using Portland Cement mortar however, is not recommended on old brick due to different flexion and hardness. That is another topic.

    I have seen spalled brick across enough old buildings but could not state what the cause was and whether or not insulation was a factor. But I have seen far more in pretty decent shape, periodic re-pointing excepted, that were not insulated.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • Maine Doug_65
    Maine Doug_65 Member Posts: 24
    My 1911 bank building

    has three layers of brick with a small air space between them. Inside is lath and plaster with another air space. The brick was wood fired and has a hard surface but softer interior. It is in excellant shape and required very little repointing. All the granite required repointing. Insulation was never added to the walls or above the 14 foot ceilings.
    There is some spalling in the lower course at a couple of the corners.
    I did not insulate above the ceiling to avoid moisture buildup in the 4.5 foot space between the ceiling and roof and the exterior walls in this space are bare brick. Also a little warmth is needed to melt snow and keep the center roof drain working.

    A fellow at the brick company said the same as you-- don't paint it and let it breath.
  • ChrisL
    ChrisL Member Posts: 121
    Older Brick Buildings

    I guess a bigger question is where are we headed as far as the future of these old brick buildings. If energy prices keep going up, they are going to become too expensive to heat. I own a number of older 20's brick apartment buildings with 3 course brick exterior walls and they are very hard to heat evenly, and even when they are heated to say 70, the outside walls are cold like ice and really make it very uncomfortable.

    I read an article a while back where the options they offered were either injecting foam spray insulation into the gap between brick and plaster, or putting up foam board insulation on top of the plaster, or demo-ing the plaster and gluing it to the brick. I know from my buildings that the gap between plaster and brick has some huge wind+convective currents that go from the the bottom all the way to the roof unimpeded, and also spread into the joist areas since there is no blocking. On a two or three brick wall, I don't think that sealing the inside with insulation would be too risky since there is still a lot of air movement between the outside, and other rows of brick.

  • Maine Doug_65
    Maine Doug_65 Member Posts: 24
    Injected foam

    Injecting foam into the gap behind the plaster would be a good improvement. With a flat roof and flat ceiling and 4.5 feet between them, that gap is accessable from the top. It feels like it is contiguous by the draft where I had opened it. I bet that would be a pricey process.
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