August 2011: Pressure and Thermal Boundaries

Pressure and Thermal Boudaries

If there was a single concept that should be ingrained in all contractors that work directly or indirectly with Home Performance it would be getting the pressure and thermal boundary correct.  Whether it is identifying it correctly on the front end of the assessment or in the reconfiguration process after building an actionable work scope or as work proceeds, it is paramount to get it RIGHT. This is the main reason it ranks as the first item on my Lucky 13 List of prescriptive areas to apply to all buildings. Though I refer to the three criteria as : complete, well-defined, and, aligned with one another; John Tooley and the gang at Advantage Energy call them by the three “Cs”…COMPLETE,CONTINIOUS and CONTIGUOUS. A couple of excellent articles can be referenced in the past issues of Home Energy March/April and May /June 1999 (these were handed out during the first Teaser session). It may seem like a simple concept to convey but to actually understand and SEE it takes experience, time spent looking at a lot of buildings, and, what I refer to as “spatial referencing”….If you were good in Geometry class this helps immensely.

Remembering that Home Performance could best be described as three main strategies:

1.      To treat the house as a system

2.      To build/retrofit according to climate (mixed humid)

3.      Control the movement of: air, heat and moisture.

Realize that these three barriers do not completely block they simple retard the flow of this air, heat and moisture. It is the job of the Building Analysts to identify them, the contractor’s job to put them in place and QA’s job to insure they are there and working properly. By accomplishing these goals we all serve a unique part to insure the clients actualizes greater: comfort, health, safety and savings. “The objective is to restrict air, heat, and moisture movement at its source, reducing their entry into the assembly or conditioned space. This practice will help reduce air infiltration, hidden condensation, mold growth, and rot and to maintain installed R-value. “John Tooley Home Energy May/June 1999.  We can dive deeper at some other time.


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