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Historic home insulation questions

Newburgh70 | Posted in General Questions on

Hello everyone, 
I am new to the forum and the new owner of a 5700SF Historic home located in Newburgh NY, 12550. The home is in excellent condition overall but will be going through some upgrades over the next few months and I was considering insulating the house while I am at it. 

Plaster walls everywhere with clapboard on the exterior. I have spoken with a couple of insulation contractors who are suggesting we would go about it from the exterior. I have read a lot of mixed reviews on this online and also read a lot of the previous post on this topic but still do not have a definitive answer on what to do. Also, anything I did find on the topic was quite old and I am sure there have been advancements in products since then. 

The site will not allow me to attach a picture from my phone or computer. If this is possible and recommended, what type of insulation should I be looking for? I know one of the guys mentioned they use victory polymers foam.

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  1. walta100 | | #1

    Before you make any changes understand this house has survived because how much moisture gets into the wall and gets out has found a good balance. If you insulate you are going to change that balance. If the balance is wrong the walls may rot or the exterior paint fall off the walls every other year. We all want low heating bills but the payback is often long and the risks are not insignificant.

    My first question is how sure are you, that there is absolutely no active K&T (knob and tube) wiring in your walls? It is not uncommon for people to hide K&T wiring by splicing modern wire in the boxes and any place the wires are visible. Insulating over K&T wiring is a big fire hazard.

    If you are sure the walls are safe I would think about blowing cellulose into the walls and attic only after I did the best possible job of air sealing the house using a fan and incense sticks.


    1. Jon_R | | #2

      > If you insulate you are going to change that balance.

      Also note that air sealing can change the balance far more than insulation. For example, changing a wall that is moderately tight on the interior and leaky on the exterior into a moderately tight and tight wall can create a moisture problem.

    2. severaltypesofnerd | | #8

      Insulating over Knob & Tube is no sort of fire hazard whatsoever: at least not for the reasons some people state. The "overheating" theory for example is completely wrong: if the breaker size is correct, K&T take take as much or more current than modern wiring.


      I however concur that moisture balance is a HUGE issue. Insulating via blow in from the outside will also destroy what's left of any tar paper, inviting leaks.

      Insulating old walls is VERY dangerous.

  2. Newburgh70 | | #3

    Hi Walter,
    The house is going under a major renovation very soon. All electric is being upgraded. There will be no more knob and tube.

    Jon R,
    This is what I am nervous about.

    I also came across this link

  3. BrianPontolilo | | #4


    You didn't say when this home was built, but I have not heard of a many problems from fibrous insulation blown into the walls of very old homes. That said, there is a lot to consider, including the fact that the results may be less-than-stellar if the house is still super leaky. So, you could consider some air sealing measures as well. And like Walter said, if the walls are getting wet inside and drying easily right now, because they are empty and without any air or vapor barriers, which is the case with lots of old homes, the insulation may change that equation. You may want to assess how well the siding and any underlayment (that could possibly have been added at some point?) are doing at keeping the walls dry. Here's a list of considerations for your situation from Peter Yost:

    "The order of priority is always the same:

    (1) Bulk water management

    (2) Air leakage (convective) control

    (3) Addressing dedicated directional drying potential

    (4) Thermal (conductive) control."

    Those are from this article:

    Blower door directed air sealing may also be worth considering. Here is something to read on that topic:

    1. severaltypesofnerd | | #9

      From experience: insulating old house with blown in cellulose is super dangerous. If that stuff gets wet it just retains the moisture, leading to eventual paint failure inside or out.

  4. Newburgh70 | | #5

    Thanks a lot, Brian. Much appreciated, ill have a look. I would guess the home was built in the very early 1900s. Here is a pic

  5. Newburgh70 | | #6

    Sorry, 2 attempts to upload a pic from my home computer didn't work either. Something must be wrong with the site.

    1. Expert Member
      BILL WICHERS | | #7

      I’ve had similar problems uploading pics. I was successful when I only uploaded one pic per message. Make sure the pics aren’t too big too, I suspect there is a file size limitation.


  6. seabornman | | #10

    Do you know what the exterior wall construction is? I have seen early 1800s houses in NY with several types of wall construction and structure, which would affect your decisions. Anything from braced post and beam with "studs" or planks, to balloon framed, with various combinations.

  7. Newburgh70 | | #11

    Hi Joel,
    I am honestly not sure, I will have to ask my contractor.

    Would the same overall opinions be for insulating the roof?

  8. Expert Member
    Dana Dorsett | | #12

    It makes a HUGE difference if there is sheathing and sheet air barrier type materials between the clapboards and the wall cavities. Houses with let-in bracing and clapboards nailed directly to the studs are NOT good candidates for simply blowing insulation into the cavities, since there would be no capillary break of any type between the siding and insulation, and almost no ability of the clapboards to dry.

    Investigate the wall construction's material stack up, and the details of the window flashing (if any) before proceeding.

  9. Newburgh70 | | #13

    Hi All,
    I really wish the site would allow pictures to be uploaded. It would be very helpful.
    My contractor just sent me pics and it seems as though the house was framed in wood on the exterior where the clapboard is, and bricked inside.

  10. Newburgh70 | | #14

    Trying picture uploads again

    1. josh_in_mn | | #16

      No pictures showed up.

  11. Newburgh70 | | #15


  12. seabornman | | #17

    I have seen brick inside an exterior wall (nogging is the term) of houses and barns of this vintage, but I have only seen it used in areas like a pantry to keep pests out and seal the space. I haven't seen it throughout a house. If it is, it will be much more difficult to retrofit insulation. See if your contractor can verify where the brick is used.

  13. Newburgh70 | | #18

    Hi again everyone. I have visited the house again today and see the entire house, on every single floor is brick behind the plaster. I made a mistake about the framing though. They framed the house in wood and put brick around it so the framing is not in front of the wood, it is next to it.
    Strange but true.

  14. Newburgh70 | | #19

    Hello everyone, please read this article. This is EXACTLY what I have going on.

  15. GBA Editor
    Martin Holladay | | #20

    If you have a wood-framed house with brick nogging between the studs or posts, the best way to insulate the walls is with continuous exterior insulation (rigid foam or semi-rigid mineral wool). To do that work, you would need to remove the siding. Once the insulation was installed, you would install furring strips, and then either re-install the old siding (if it is in good shape) or install new siding to match the old historic siding.

    That work would be expensive, so many homeowners would conclude that the work isn't worth the cost. As an alternative, you can simply perform blower-door-direct air sealing. For more information, see "Blower-Door-Directed Air Sealing."

  16. Newburgh70 | | #21


    Good morning. Thank you for this information, It’s certainly a lot to digest.
    The top 3 floors of my building are just about perfect. The only floor that’s a gut is the basement so I can do whatever I want to do there from the interior. Removing and reinstalling all of the clapboard, reframing the entire building and/or installing hardy board in its place will be extremely time consuming and costly, I agree. I now understand why a lot of people leave the exterior walls alone.
    I do have an attic though. Maybe I can just concentrate on the basement and attic for now along side the blower door test?

    Any suggestions for going that route?
    Thank you and Happy holidays

  17. GBA Editor
    Martin Holladay | | #22

    For more information on improvements to your attic, see these articles:

    "Air Sealing an Attic"

    "How to Insulate an Attic Floor"

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