Ideal roof overhang length?
I think I have decided on the wall assembly that I want to use but by the sounds of it it spend time concentrating on the wall but very little time on the roof.
I have read several books on sustainable design and affordable or low tax housing. My general plan was to build a rectangular house with a gable end roof on a 4/12 pitch. I had intended to use either a 16” or 24” raised heel truss with 2’ overhangs. I intended to use through fastened metal roofing. My design goals are one and only one roof line.
After reading Martin’s suggestions for roofs I think I favor upgrading to a 12/12 pitch to help shed water and provide a less likely to leak roof. I would be willing to pay for the extra ~30% roofing area knowing that the likelihood of any leaks causing damage would be diminished.
My questions roof overhangs. I still haven't decided if i’m going to go with 8’ ceilings and a duct wall or 9 foot ceilings and drop the ceiling 1’ over the bedrooms for HRV ducts. This will factor into window sizes and placement for passive solar tempering.
I am looking to build in Sanilac County Michigan and the average rainfall is around 30” and 49” snowfall per year.
What is the ideal overhang for this climate? I was planning on 2’ overhangs but am interested in longer overhangs if possible if it doesn't interfere with passive solar.
What is the ideal overhang for the rake on the gable end? Since the overhang on the gable end side is at varying higher elevations should this overhang be larger than at the eaves to provide more protection from precipitation and the sun?
Raised Heel or over sized truss? I have found very little information on the web on this topic. Is there a significant difference in thermal bridging between running raised heel vs over sized trusses? When using steeper pitches like 9/12 or steeper the over sized would have plenty of space for full depth insulation on the attic floor. I think over-sized trusses would be stronger and provide a surface for vented soffit.
Posted Nov 30, 2012 5:22 PM ET
Edited Dec 1, 2012 6:17 AM ET
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Can unvented roof assemblies be insulated with fiberglass if I use rigid foam on the exterior of the sheathing?