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Community and Q&A

Retrofit roof insulation for church

Newbold | Posted in Energy Efficiency and Durability on

My local church in Chicago was constructed in 1955, its a wood moment frame design with 2″ T&G on the interior as the finish ceiling as well as the structure that spans between purlins. We’re looking to re-roof, asphalt shingles, this summer. When I was doing a little investigating I noticed there is zero insulation on the roof. The roof is quite steep, any ideas of what we can do on the exterior for insulation. The total roof area is about 10,000 and the pitch is about 14/12.



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  1. GBA Editor
    Martin Holladay | | #1

    Here is a link to an article that will explain what you need to do: How to Install Rigid Foam On Top of Roof Sheathing.

  2. Expert Member
    Dana Dorsett | | #2

    With 10,000 square feet of roof area it's probably worth finding a source for reclaimed roofing foam to take the sting out of the materials budget. To do even R20 with new stock polyiso or EPS would run ~$20K just on the insulation. Re-using reclaimed foam would run $5-8K for R20. There's at least one foam reclaimer with a distribution network covering most of the 48 contiguous states (Nationwide Foam), but there may be more local sources too.

    IRC code-min roof insulation is for commercial buildings in US climate zone 5 (that would include Chicago) would be R25 continuous insulation. That would take 4.5-5" of polyiso (about $25,000 for 10,000 square feet, if using virgin stock material, $8-10K if reclaimed) and would be a HUGE performance improvement.

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