Meanwhile, up on the roof...

The roofing system that I am using for my eco-friendly home is different than the systems used for most homes. I am using a multi-layered roofing system for the roof that’s designed to compliment the advanced framing construction techniques I used below it.



The roof isn’t quite done yet, but when it does it will pack quite an R-value punch. My base layer for the whole system is a layer of GAF underlayment to keep water out but allow the whole roof to “breathe” - that is, allow moisture to escape. I’ll place my insulation system on top of that, which for the roof consists of two four-inch layers of rigid commercial insulation.

On top of the two four-inch layers of rigid, I’m placing 2x4s spaced about a foot apart, with an additional one-inch layer of insulation. This will create an air cavity that will allow for roof ventilation. Above that goes a layer of plywood, followed by shingles.



At the very top is a ridged vent that completes the ventilation aspect of my roofing system. Adequate ventilation is necessary in a colder climate like New England to prevent the roof from icing up during a snowmelt, and to vent moisture that’s moving from the interior of the home to the attic. If you’re ever looking for a crash course in roof venting, I've put one of my favorites at the end of this article.

I did not add extra insulation underneath the garage area, simply because I don’t plan on using the space. I focused on creating a building envelope around the primary living space, where my wife and I will spend most of our time.

The system I built should have a thermal resistance (R-value) of around 70. R-70 is a lot higher than most conventionally built roofs, which come in at around R-30. I built the whole system to work together as one unit to keep my home as comfortable and energy efficient as possible.

If you're looking to expand your knowledge about roofing ventilation, buildingscience.com has a good article that I found is a good place to start.

As I finish up the roof, I’m also getting ready to install the first PEX tubing for my underfloor heating system in the basement and garage foundation floors. I plan to have Taco Residential Trainer and underfloor heating expert Dave Holdorf come down to the job site to give me some insights and tips about the system I plan to install. Dave is a lot of fun to work with, so I’m looking forward to seeing him and hearing what he has to say. Stay tuned!


Showing 4 reactions

Please check your e-mail for a link to activate your account.
  • Shawn,

    Thanks for your comment. Yes, I had the same concerns when it came to choosing roof materials. We plan on installing 51 PV panels on the back roof of our home, so that’s why we had to weigh our options carefully. I put together a segment where we explore what kinds of shingles are best for certain applications. You can check it out right here:

    https://www.youtube.com/watch?v=eBf4BllEdWA

    Let me know what you think!
  • Joe,

    I have put together some materials that should answer some of your questions. You can find it right here on the Green Comfort Photobucket account:

    http://s1361.photobucket.com/user/GreenComfortBlog/media/Wall%20construction%20diagram_zpsthakw0py.jpg.html
  • hi Dave, interesting stuff…I work in hydronic heating…there are 2 factors concerning roofing materials that should also be addressed : sustainability and potential solar equipment…I recently chose my roof based upon these 2 factors because 1) shingles are an ongoing source of construction waste in landfills…I wanted a product that would protect my roof and last a long time, not contributing to more waste cluttering up a landfill every few years…2) I am going to put solar thermal equipment (to heat my hot water-a Viessmann Vitosol Solar Pack…solar thermal has a way better payback than solar PV) on my roof and I did not want to install a roof, then have to remove solar equipment to re-install another roofing product…here are 2 products that fulfilled those considerations http://www.euroshieldroofing.com/ https://malarkeyroofing.com/product_detail/legacy both are excellent products…I live in the foothills of the Rockies, so extreme hail / ice and wind were more of a consideration for us weather wise…the warranties with both of these products, as well as the quality of the installers available made a significant impact as well and we are happy with the results
  • Great roof insulating system, however, a closer view of a cross-section of completed system would help me better understand. Do I presume the two 4" rigid foam board are fitted between the roof joists to a plywood deck using rigid foam approved glue? Then the breathable barrier is placed over the plywood and then the “sleeper”(?) 2×4 on its 3.5" side with an addl 1" thick insulating rigid foam board in between the 2×4s with the these affixed to the roof joists using 3-" 16 penny nails? Thus two layers of plywood involved? Thanks.