The house of the future is airtight. Examples: the Passive House standard calls for 0.6 air changes per hour at 50 pascals depressurization (ACH50), while Efficiency Vermont’s standard for new homes is 1.0 ACH50.
Even regular building codes are getting tougher. The 2012 International Energy Conservation Code (IECC) requires 3 ACH50 in cold regions, 5 ACH50 in milder climates. Many states are not enforcing that, however—mostly because some builders say that 3 ACH50 or 5 ACH50 is too strict (or too costly).
But if 3 ACH50 is too tough, how are Passive House builders doing five times better? One strategy they employ is ensuring the airtight shell is never compromised by wiring, plumbing, or mechanicals. The trick is to create chases that isolate those services from the insulation and air barrier. Tedd Benson, founder of Bensonwood Homes in Walpole, N.H., calls this “disentangling” the building elements.
This approach keeps the air-pressure control layer intact as you finish out the house. It also allows future owners to modify the plumbing, wiring, or HVAC as technology advances, or when their needs change—without risking the performance of the building structure or the insulated airtight envelope.