Wall systems decision
I am designing and home in the outskirts of Santa Fe, NM (climate zone 5B / elevation 6800 ft.).
I am interested in energy efficiency, low maintenance and overall best choice for this climate.
(note: we are planning to use geo-exchange heating and cooling + PV’s to minimize energy costs as the site will only have electrical and propane fuel sources)
We all know pretty well the pros and cons of double wall frame construction for this area.
Adobe brick seems to be a nice and locally available method, but it seems to take much longer, cost much more and requires rigid foam insulation on the exterior.
ICF & pumice walls are also a common option, but I have little knowledge of the pros and cons of these methods.
The last choice I’ve researched is AAC block (e-crete or Hebel) which seems to be an easy and effective system. Alas it does not seem to be common method in the area.
I’ve read all the articles on this and other sites for all of these systems, but none seem to give much of a conclusive direction one way or another.
Any information, input and opinions will be appreciated.
thx!
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Replies
Abelardo,
There seems to be something about Santa Fe that leads homeowners and builders to obsess about wall specifications. What is it about Santa Fe?
GBA reader Kim Shanahan wrote about this phenomenon in a comment posted on this site. (It was in response to an article on earthships.) Shanahan wrote:
"It is often said around these parts that there has never been a wall system conceived that hasn't been tried by a Santa Fe builder. And many of them are proud members of our local HBA. Indeed, even my career as a builder saw me dabble in strawbale, Rastra, adobe and even a formed-on-the-wall puddled adobe system I devised and employed on my own personal home. I was certain it would revolutionize adobe construction world-wide.
"I took my idea to the local Executive Director of an affordable housing non-profit to proselytize on the cost-saving wonders of my system. It could utilize un-skilled volunteer labor to put up walls, while having beers, getting baked, and socializing in the Southwest sunshine. The ED of the housing non-profit, whose primary function was to provide low-cost home ownership financing, simply rolled his eyes at yet another wonder wall presentation and reminded me that if he could find an extra half a percentage point of savings on a bought-down 30 year mortgage interest rate, he could save a consumer more money over the lifetime of homeownership than I could even if I invented a home that had no walls at all! Chagrined, I shifted my focus to modern building science and re-learned to love frame walls, lots of insulation, tight envelopes, and mechanical air-exchanges.
"A not insignificant part of my job running our local HBA is disabusing newly arrived aging hippies that the wall-systems they have read about have all been tried by local builders. And the really good ones, the ones still around long after their pony tails receded past the back of their hat bands, will be happy to build them a net-zero energy home that barely sips from our precious aquifer, all while using the same basic construction techniques of whatever kind of home they just moved away from.
"After they get over their initial disappointment, I think most of them are actually relieved to have the certainty and warranty that a new home with a genuine HERS rating can provide."
Abelardo,
OK, now that I've made a few jokes about Santa Fe builders -- sorry for the unjustified detour -- I'll focus on your question.
I imagine that you already know how to build a code-minimum wall. I'm assuming the main reason that you are posting a question on the GBA site is that you would like to choose a wall system with a higher R-value than a code-minimum wall.
As I've written before, the two main choices are (a) a double-stud wall and (b) a 2x6 wall with a layer of continuous insulation (rigid foam or mineral wool) on the exterior side of the sheathing.
Either of these two approaches can work, and the choice often comes down to the builder's preference.
ICF walls cost more than the two options I've listed, and often have a relatively low R-value.
Adobe walls and AAC walls have a relatively low R-value.
You wrote that you want a "low maintenance" wall system. Achieving that goal depends mostly on siding choice. You don't want to choose siding that needs regular painting. Siding choice is rather idiosyncratic; siding choice often boils down to local preferences. Certainly brick veneer is low maintenance -- but brick veneer is expensive, and must be installed conscientiously to avoid water-entry problems.
Martin,
Thank you for both of your replies. I've read your articles on the subject with great interest.
You did give me a chuckle in your first reply. As my realtor told me "that's why they call it the "City Different"".
This house is definitely not in the category for experimental and out there wall systems. With your answer above, I think I will go back to basics and stick with the frame construction and discuss the details further with the selected builder from his experience.
Due to architectural design constraints in the locations CC&R's, the skin needs to be stucco to fit into the Pueblo and Territorial styles common to the area. So I'm thinking a color infused acrylic three coat stucco similar to El Rey (Parex) Fiber-47 300 (HE) High Efficiency system.
If you have any other thoughts please feel free to share.
Many thx again!
a