GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Low slope roof venting question

tech1234 | Posted in General Questions on

I have purchased a property with an existing garage that needs some repairs and I would like to do some improvements to half of it (1 of the 2 bays). I would like to insulate and (intermittently) heat one side with a wood stove for general shop work stuff. The other side I’ll leave as cold storage. 

 
It has a low slope “shed” or “mono pitch” roof on roof trusses (look similar to floor trusses) 
 
Roof pitch is 1.5 : 12
 
Currently has screw-on metal on 1×3 sleepers. (In bad condition)
 
Size 36 deep x 48 wide
 
It is located in southern NH
 
 
I would like to replace the roof and insulate the building (or at least the one bay)
 
I was originally thinking standing seam metal (hydrostatic) but my metal roofing contractor said that I would be better off with a TPO roof on this pitch. 
 
My question is about venting low slope roofs in general and especially on a TPO roof. Originally I was thinking I would put up drywall on the ceiling and fill the truss cavity with blown in cellulose and then put 2×4 sleepers on the roof deck and then add another layer of sheathing and then install the TPO roof on that. But then I read the 475 article below. 
 
Do any of the experts here have experience with venting low slope roofs and know what the best practices are? 
 
I have attached a crude drawing of my situation. Any advice would be welcomed.

James

https://foursevenfive.com/blog/the-ten-golden-rules-for-foam-free-flat-roofs/

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.

Replies

  1. Jon R | | #1

    A low (not flat) slope vented roof over normal conditioned space should have over-sized vents to make up for the decreased stack effect drive. 1.5" vents would be fine with occasional use.

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |