Is there such thing as a “perfect wall” design?

Guess it all depends on the criteria being used to define what “perfect” really means, but if there is one person on this planet of ours that might have a clue what the perfect wall is, it is Joseph Lstiburek. At the wonderfully named Let’s Fix Construction website, building scientist extraordinaire Lstiburek contributed an article with the bold title, The Perfect Wall.

In truth, the article goes well beyond the scope of describing what a “perfect” wall might be, and could instead be titled, The Perfect Building Envelope. Besides walls, Lstiburek also diagrams the components of the perfect roof, the perfect slab, as well as providing several variations on wall design options.

Getting back to the definition of what a perfect wall actually is, here is the introduction:

The perfect wall is an environmental separator—it has to keep the outside out and the inside in.  In order to do this the wall assembly has to control rain, air, vapor and heat. In the old days we had one material to do this: rocks. We would pile a bunch or rocks up and have the rocks do it all. But over time rocks lost their appeal. They were heavy and fell down a lot. Heavy means expensive and falling down is annoying. So construction evolved. Today walls need four principal control layers—especially if we don’t build out of rocks. They are presented in order of importance:

  • a rain control layer
  • an air control layer
  • a vapor control layer
  • a thermal control layer

A point to this importance thing here, if you can’t keep the rain out don’t waste your time on the air. If you can’t keep the air out don’t waste your time on the vapor.

You’ll definitely want to read and bookmark the full article. Just be prepared — this is some seriously geeky building science content. But what else would you expect from the founder of the Building Science Corporation?