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Community and Q&A

How do I find a contractor that does external insulation?

Jason Crawford | Posted in Energy Efficiency and Durability on


I’m a fairly new home owner in zone 5A (NY, 40 miles north of NYC). My existing house is about 60yo and appears to have almost no insulation . The siding is mostly white-painted thick cedar shakes and a bit of board+batten. It’s a quirky house built by the owner two generations ago and surprises abound.

Alas, the paint on the siding is peeling in places and turning green in other places. Clearly siding work is necessary. I’m still trying to determine and price out my options… including simply prep+repainting. — Given the absence of insulation and my huge heating bill, I’m also thinking about insulating before winter arrives. These two considerations have lead me to try to investigate siding with several inches of exterior rigid foam insulation. I’ve read this is a terrific way to insulate for many reasons. Exterior insulation is also appealing to me because it seems like a single approach that is likely work regardless of any quirks that might be discovered in|near walls.

Alas… despite exterior insulation appearing to be highly recommended on the web, I’ve not found any contractors that have experience applying more that 3/4″ of exterior rigid foam. And when I ask questions, they don’t seem to understand the value of this approach to insulation.


How does one find a contractor that actually has experience adding at least R-10 of exterior rigid foam insulation?

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  1. GBA Editor
    Martin Holladay | | #1

    An excellent question! I know that in some areas of the country -- perhaps most -- your quest will be frustrating.

    GBA readers -- any suggestions for Jason?

  2. TJ Elder | | #2

    Maybe you could tell the local contractors they need to start reading Martin's blogs here at GBA.

  3. Dan Kolbert | | #3

    Check the USGBC listings, ask local architects or energy auditors.

  4. J Chesnut | | #4

    Time and money are two very important factors.
    I would recommend not rushing into this project to try to finish before this winter. Take your time finding a qualified contractor and write up a detailed scope of work to base your bids on.
    In the meantime before this winter it is a pretty safe bet to dense pack the existing walls with cellulose insulation.
    In addition to finding a contractor literate in exterior insulation make sure the contractor is literate in establishing a continuous air barrier as much as possible while retrofitting an existing home.

  5. Shane Claflin | | #5

    check the NYSERDA site for a list of contractors. EmpowerNY

  6. Jason Crawford | | #6

    @JC Thanks. But won't the cellulose push the dew point toward the interior and require even more external insulation to keep it outside the sheathing? And... would filling the walls with cellulose be a bad idea if I might "open" up those walls to replace drywall during the winter?

    @DK, SC Thanks for the suggestions. Perhaps part of the problem is half the people I'm dealing with are siding people or general contractors rather than insulation and energy people. I'm looking in to the suggestions you provided.

  7. J Chesnut | | #7

    For your climate zone here are the minimum R-values of exterior foam sheathing needed if your walls are dense packed with cellulose: R-5 for 2x4 walls, R-7.5 for 2x6 walls. (see

    Dense pack cellulose properly installed at 3.5 lbs/ft3 will hold in place if drywall is taken off. If you are planning to demo the drywall by gutting it with a hammer it will likely gouge out some of the insulation with it.

    I would also recommend sketching out for yourself how the exterior insulation will integrate with your windows, doors, and exterior casings. If your windows predate flange window installations the details will be more tricky.

  8. Aj Builder, Upstate NY Zone 6a | | #8

    Jason, am driving past you weekly. Ajbuilderny at g mail dot com.... This site too has specs and details that are what you and your contractor would find valuable.

  9. Jason Crawford | | #9

    I have found a local contractor that was able to comment on the apparent lack of local experience with exterior insulation exceeding 1". His comment was that exterior insulation is more expensive than in-wall insulation. Is this really true? I'd expect it to be a necessity to put at least some exterior insulation in and would hope that the cost of use of screws rather than nails would be roughly offset by a lower energy bill. In my case it's a retrofit, but I expect to have to replace the siding anyway. What do the GBA experts think?

  10. GBA Editor
    Martin Holladay | | #10

    Most people who own an older home with uninsulated studs start by installing dense-packed cellulose insulation in the wall cavities. That is indeed the least expensive way to insulate the walls of an existing uninsulated house.

    Anyone who needs new siding -- especially someone who lives in a cold climate -- should consider installing thick rigid foam insulation on the outside of their walls in conjunction with the new siding. It will never be easier to do -- until the next time you replace all the siding on your home.

    If you are getting new siding on the walls of an uninsulated home, I recommend that you do both types of insulation retrofit at the same time: blow some cellulose into your stud bays and then cover your exterior sheathing with rigid foam.

  11. Aj Builder, Upstate NY Zone 6a | | #11

    Basic economics . The bottom line. Completely insulating a non insulated home to 2012 specs if done for profit by a contractor is expensive. Saving a thousand dollars a year or even three thousand would be an easy sell and a desired project, if, the work cost five to ten years of savings. This is just not the case though. Three inches of of exterior foam, ripping off existing siding, air sealing, adding outsulation, WRBs, trim, siding, updating windows, (edit, forgot to mention the cost of proper ventilation system additions, possible updates to water heater, heating system air source, exhaust, kitchen, laundry and bath vents, and even next possibly addressing moisture sources such as wet basements that don't effect 60 yr old homes like they will a freshly air sealed 2012 spec.,) the cost approaches and or passes the cost of a full gut rehab.

    Still, it's a good project. One has to see it as a large undertaking that will result in a new 2012 home. It is not a small home improvement.

    If the interior of exterior walls is being replaced, insulation from the inside would price out lower, be a good project, could be done in stages as works for the homeowner, very trade friendly and is advocated by some as having the vapor barrier on the right side of the wall.

    I say give serious thought to adding insulation to the inside. I could see the total cost coming in a half an outsulation project.

    Air sealing with the new Knauf system, Spyder or cellulose, an inch of foam, work on the attic and basement/crawlspace.... change some windows... good fall/winter project.

  12. Shane Claflin | | #12

    check out New York state Foam and Energy out of Cornwall, NY. They are building science certified and know what they are doing.

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