Closed Cell Foam on Dormer Section of Roof and Fiberglass on Remaining Section?
I’m building a small 12′ x 26′ Coffee Shop near Cleveland, OH in Climate Zone 5. We’re in the building design phase and are trying to figure out the most cost effective way to insulate the Cathedral Ceiling in our shop. I’ve done extensive research and this article on GreenBuildingAdvisor.com ( “Five Cathedral Ceilings That Work” : https://www.greenbuildingadvisor.com/article/five-cathedral-ceilings-that-work ) has been extremely helpful. However, since the Coffee Shop has a dormer we won’t be able to go the cheapest route in the article. That being, “Assembly #1: Vented assembly with fiberglass or mineral wool insulation”.
I’m trying to come up with solutions to keep costs down. Here is one of them. Since there’s a dormer on the building, can I apply r49 worth of closed cell foam insulation in the dormer rafter and the rafter all the way up to the roof ridge ( see the outlined green section in the attached photo )? The rest of roof would be a vented roof with fiberglass like “Assembly #1: Vented assembly with fiberglass or mineral wool insulation” suggests.
Is this a good solution?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part