The front page upper fold story in the Sunday business section of the New York Times yesterday was about a family building a Passiv-House in Vermont. Worth checking out for prospective on how adoption for this approach is slow to take hold in the US vs Europe, where it is widely used. We like the Passiv approach, as it focuses on passive (duh) techniques, rather than more resource intensive mechanical approaches. One of the main products used in Passiv design that is starting to come on the market here is triple paned windows, which reduce thermal loss from the lowest R value element of the housing shell. We have yet to install these, but are looking at the cost savings compared to the increased cost to purchase. I expect the cost will drop as they become more commonplace, as this is not a flashy technology, just the next step in window technology.
Although we are not building the extra deep double stud walls also seen in Passiv design, we are building tight enough that we need to bring fresh air into homes. The article talks about installing a Heat Recovery Ventilator (HRV). In the Virginia mixed-humid climate we have decided to install Energy Recovery Ventilators (ERV) instead. This mechanical system (yes, we do value advanced mechanical engineering along with passive design) is for geographic regions where cooling loads (AC) place strong demands on HVAC systems. Rather than just capturing the heat from exhaust air to reduce the need to heat cold incoming air, the ERV also transfers humidity from hot outside air to dry exhaust air (and vice versa), which is a serious concern here when the the interior and exterior humidity varies widely in July and August. HRV/ERVs also keep pressure better regulated on the house, rather than just using a supply-only fresh air intake or exhaust-only vents, which can cause humidity to get pushed through wall cracks causing condensation and mold.