Folks are always asking me, "Why are we having so many problems with buildings today? We never seemed to worry about rot, corrosion and mold before." What's going on? What's different? Is it workmanship? Builders and contractors are pretty bad today, right? No, it's not workmanship and the trades. It is always convenient to blame workmanship and the trades when you don't understand the problem.
If you do the wrong thing right, it's still wrong? Right? This is the basic difference between quality control and quality assurance. Quality assurance is figuring out what the right thing to do is. Quality control is executing it. For most of the past few decades, we have been focusing on quality control and have been missing the quality assurance part. We have been doing the wrong things, but we have been doing them really well. We have missed some basic fundamental changes to our industry.
Five fundamental changes to building construction have occurred in the last 50 years. They happened so gradually and insidiously that we missed their enormous significance. The five fundamental changes are:
* Increased thermal resistance (Photo 1);
* A change in the permeability of the linings that we put on the inside and outside of building enclosures (Photos 2 and 3);
* Water and mold sensitivity of building materials (Photo 4);
* The ability of the building enclosure to store and redistribute moisture (Photo 5); and
* Complex three dimensional airflow networks that inadvertently couple the building enclosure to the breathing zone of the occupied space via the mechanical system (Figure 1).
Fundamental change number one is reducing the drying potential of the enclosure by adding thermal resistance. One of the reasons older buildings were so durable is that when they got wet they didn't stay wet very long. Repeated wetting followed by repeated drying was never a problem. Older buildings got wet, but they dried quickly. What made it all work …
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