Expert: Richard Taylor, AIA - 1/5/2012

Question
Richard, thank you so much for offering your expertise.  I just read your comments regarding Hot & Cold roofs.  I have been working on a design with an engineer and designer(s) for our dream home in Alaska (it has been a very long frustrating process) and one of the many challenges I have been running into is the mis-communication...some of which I think can be attributed to different understanding of construction terminology.  I wanted to build a house that was designed specifically for our lot to maximize the eastern and southern exposure, the mountains and forest views as well as being the most efficient our cold climate.  One of my ideas was to have shed roof/vaulted ceilings with south facing clerestory windows.  If I am understanding correctly, this would be referred to as a “cold” roof which based on the description is the best suited for our climate to minimize ice damming (please correct me if I am wrong in my understanding).  So that being said I started to put the drawings out for bid and included a request for feedback from the contractors, because of the challenges I have run into.  The final drawings are different than what I had asked for from the engineer and my faith in his understanding of my project has dwindled significantly over the past year; needless to say I gave up on asking him to fix it.  Anyway, one of the contractors suggested using a parallel chord truss roof instead of an I-joist roof system for the vaulted/clerestory roof.  He noted that the parallel chord trusses “are easier to install and offer far superior cross ventilation”.  What are your thoughts on my roof choice or on the contractor’s suggestion?  Also, do you have any suggestions for a better way to vet the drawings I have from the engineer…is it best to go to another engineer or would an architect be able to review them and identify better methods; I really do not have very much faith in his prescribed construction methods for the below grade level, since it is exactly what I told him that I did not want and what the city inspector said they would not approve?

Answer
Hi Lisa - thanks for your question!  Alaska sounds wonderful, I can only imagine how nice the mountain and forest views must be!

The cold roof you're referring to isn't a function of the "shape" of the roof - a shed roof with clerestory windows isn't a cold roof unless you construct it that way; it depends on the details of the construction of the roof itself.

A cold roof can be a shed, gable, almost any normal roof shape - a cold roof is a construction detail.

Here's what the "cold" part means.  Heat inside the house rises to the ceiling and heats the roof construction - some of that heat makes it all the way to the sheathing (the plywood under the shingles) on the roof.

That heat may cause some melting of snow, which is how ice-damming starts (that's another story).

A COLD roof creates a cold air space between the main roof structure and the sheathing/shingles above.  This isolates the shingles from the heat of the house - and prevents the snow from melting.

And viola - no more ice damming!

The parallel chord trusses you've been told about make a lot of sense for the roof SHAPE (the shed/clerestory).  They also may sense for the roof TYPE (cold construction).

For a cold roof TYPE, especially in your climate - the details are critical if you want it to work.  That means proper construction materials; the right insulation; the right truss depth; and the right type of cold air space above the main roof construction.

It's somewhat technical - you might try this article: http://www.finehomebuilding.com/how-to/articles/framing-roofs-to-prevent-ice-dam

You'll have to create a trial account to read it, but it gives a good overview with photos and details.

On to your engineer.  All of the decisions you're struggling with should have been addresses by the designer or Architect.  Engineers have specific knowledge that is valuable to a proper home design, but limited to the engineering aspects.

It's as if you asked your plumber to design your house (OK, I'm being a little harsh).

The point is, the engineer is a specialist who should be working FOR your designer or Architect to work out the finer details of the roof structure and cold roof design.

It's your designer or Architect's responsibility to figure out what you want, then work with the engineer to make it happen the way YOU want and still have it engineered properly.

You shouldn't be seeing changes to the basic design or structure of the house at this point, and there shouldn't be any need to get "feedback" from contractors if your designer and engineer have done their jobs; the drawings should be complete in every respect, ready to bid, ready to build.

To your questions:

1 - I like the idea of the pc trusses...given how little I know about your project.
2 - you need to reverse the relationship between designer and engineer - the designer or Architect should be in charge, with your best interests in mind, and the engineer should be HIS consultant, not yours.
3 - if what's been designed is NOT what you asked for, and doesn't meet code, you need a new and better designer and possibly an attorney, too!

I recommend you find an Architect who specializes in this kind of house in this climate, who can should you examples of his work, who has references that speak well of him, and who will listen to you.  Architects are not cheap, but a good one would have prevented you from suffering through this year-long frustrating process, just to get a house you don't want anyway.

Best wishes, I do hope you're able to work this out!

Sincerely,

Richard Taylor, AIA
www.rtastudio.com
www.rtastudio.blogspot.com
www.facebook.com/rtastudio