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Discussion Starter · #1 ·
I'm finishing my basement and plan to make a boiler room around my oil-fired hydronic boiler (acknolwedging that I will comply with required fresh air supply and venting).

The treatment I'm using for the rest of my basement walls (in Connecticut) is 2" XPS foam glued to the concrete block wall, with a 2x3 stud wall in front of the insulation for sheetrock (leaving 1" on bottom to guard against moisture.

One wall of my future boiler room is an exterior block wall. Do I leave it uninsulated? I'm wary of clearances to combustibles. Is this something we all just need to chalk up to "doing the best one can to insulate" and deeming some areas as "impractical" to insulate?
Advice appreciated.


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You cannot leave the foam exposed in either case. Insulating it will help with the heat loss by a big factor. The flue and other hot surfaces should not be in direct contact with any foam and should have sheet metal barrier around them, a non combustible insulation (i.e. Roxul), and then the foam board.

The drywall should supply the necessary thermal barrier coverage. If you are concerned, double it up or run a fire rated drywall.

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