Ceiling support box without vented flashing??

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.


New Member
Nov 25, 2021

The store sold me one of the silicone roof flashings since I have a corrugated tin roof so it could be molded. However, they also sold me a 24” ceiling support box. The ceiling to roof clearance is shallow enough I could get the ceiling support box to pass all the way through the attic and out the roof and have my 2” on the bottom, but then the top of the support box would be fully covered by the tight fitting silicone flashing. From what I can tell if you have a ceiling support box it needs to pass all the way through the attic and have vented flashing. So, can I have the support box not pass through so it breaths into the attic, or can I use this non vented flashing?

Also, having the ceiling support box open into the attic seems like it would leach a little heat into that space which is the opposite of what I want.. does much heat pass through the double wall at all?

I was going to install all this starting in the morning, but it will be thanksgiving and everything will be closed, so any advice would be greatly appreciated! Thank you!