Expert: Richard Taylor, AIA - 11/12/2004

Question
I read your definition of a warm and cold roof that you gave on 11/1/03 "A warm roof is the standard method of roof construction. It is essentially an air space over the insulation with soffit and ridge vents. A cold roof is used with vaulted ceilings. It has no air space next to the insulation."

This definition is incorrect. Your terminology is reversed. What you describe as a warm roof is actually a cold roof and visa versa.

There has been some discrepancy between AIA definitions and industry standards. This is a perfect example of one such discrepancy. The APA, Insulation Manufactures Association, numerous construction manuals and literature including the book you sited by Rob Thallon, and construction professionals, all recognize the non AIA definition.

Other architects that I have worked with over the years have referred to these roof details the same as you have. In fact during my higher education in architecture your explanation is how it is taught. One can only assume that the AIA dictates course curriculum and industry standards are overlooked.

These types of discrepancies are unfortunate for professionals in the design field and have created an atmosphere of non trust between builders and architects often with the clients in the middle.

Our profession would be better served if the AIA would get on board with the rest of the industry.


Answer
Jeff:

Thanks for your question, but I gotta disagree with you.  Rob Thallon's book describes exactly what I described, in that a cold roof doesn't have an airspace NEXT TO the insulation, as is standard in a warm roof.

In a cold roof, the insulation is isolated from the ventilation path.  A ventilation path does exist (except in solid foam construction), but it is separated from the insulation by felted sheathing (see the illustration on page 192 of "Graphic Guide to Frame Construction").  A great example of cold roof/foam construction is the SIP (which we're using on two homes right now).

In fact, the reason it's called "cold" is because the ventilation path is isolated from the warm interior keeping the path "cold" and thus preventing the freeze-thaw cycle and eliminating ice dams.  A "warm" roof, by contrast, allows the ventilation space to take on some of the warmth and humidity of the interior, since it's not as isolated from the interior.

We may be simply talking semantics here, since a cold roof is also often referred to as a "vented cold roof".  We've designed and built both, depending upon the region and client's budget.  The unvented cold roofs we've built have solid foam insulation instead of fiberglass to eliminate the possibility of moisture saturation of the fiberglass as in the SIP roofs I mentioned above.

My information comes from 21 years of designing homes and working with builders, suppliers, manufacturers, and subcontractors.  I've learned a lot from all of them and in my experience we all agree on the definitions of cold and warm roofs.  I've never had the experience you describe of mistrust between architects and builders that was caused by a difference of opinions about definitions.  We take great pride in our relationships with builders and rely heavily on them for their role in helping create great homes.  And I have no idea if the AIA has a definition for a cold roof - that subject wasn't covered in my classes 28 years ago.

I appreciate your comments and your interest in accuracy!

Thanks!

Richard Taylor, AIA
President
Richard Taylor Architects, LLC
www.rtastudio.com