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What is the best way to build a wall?

It is perhaps the most vexing question among builders seeking to create affordable green homes: What is the best way to build a wall?

Toronto-based writer Lloyd Alter explores the question thoroughly in a new post at TreeHugger:

Voltaire wrote Le mieux est l'ennemi du bien, often translated as "The perfect is the enemy of the good;" he might well have been talking about residential construction. You run the gamut from the typical American 2x4 frame wall all the way to Passivhaus construction with 12" of insulation and incredible care in detailing and construction. Proponents keep saying that Passivhaus only costs 10% more than conventional construction, but they are not talking about Pulte and KB Homes, which is what I consider conventional. How do we upgrade the standard builder spec to build a high performance wall that doesn't cost the earth or reinvent the wheel?

Alter's well-illustrated and link-enriched post begins with a look at "the standard American wall," which ostensibly has an R value of between 12 and 20.

But it never really does; the studs have a lower resistance to heat transmission than the insulation and act as thermal bridges. The insulation is never absolutely perfect because there are wires in the cavity and you need to be really careful about installing around them and the electrical boxes.

...more importantly, research has shown that air infiltration and leakage is more important than the insulation, and that vapour barrier is shot full of holes for wires, boxes, misplaced nails and just general sloppy workmanship that comes from having people in a hurry working with an unforgiving system.

Alter goes on to consider what he calls the "Canadian Wall" (a CMHC innovation), Insulated Concrete Forms, and Structural Insulated Panels, and double 2x4 walls before arriving at a proposal by Greg Lavardera called the "USA New Wall."

It [USA New Wall] does a couple of things really well; it uses conventional materials that are familiar to anyone, but adds a horizontal furring strip to separate the drywall from the vapour barrier, and to provide a chase for electrical wiring that is not in the main insulated wall, the major cause of insulation discontinuities. After the wiring is done, more insulation is added in the furred out space, increasing the R Value of the wall. It isn't fancy and doesn't use a lot of high tech materials, but it makes sense.

With all due respect for Alter and Lavardera, I can't help but observe that the "USA New Wall" is strikingly similar to the superinsulated prefab wall developed by Matheo Durfeld in Whistler (and described halfway down this article).

It's a good idea, regardless of provenance. There may be no single step the BC and Canadian governments could take that would reduce more carbon emissions at less cost than to mandate high-performance envelopes such as these in the next version of the building code.

Monte Paulsen researches sustainability for the nonprofit Tyee Solutions Society, and has contributed to the Tyee series, Green Buildings that Pay Off.

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