When buying a home, or alternatively during new construction, one of the far-reaching decisions facing prospective homeowners is just how to properly insulate. As we established during our discussion of earthships, the proper insulation (and in the cases of some sustainable homes, super-insulation) is critical to the long-term energy expenditures of a household. Yet as Scott Gibson addresses in Green Building Advisor's Q&A Spotlight, insulation goes hand-in-hand with another, often overlooked facet of construction: airflow management and air-sealing.
While air-tightness isn't the first thing that comes to mind for most people when their attention turns to home construction, it has a major impact on interior air quality and energy performance. Getting it right during the construction phase can dictate energy loss (or savings) that will be incurred years later during the building's lifetime. Knowledge of your options can be crucial, because almost all home owners operate under a tight budget when constructing their abode, often presented with difficult decisions about where to invest limited amounts of resources.
Recent home builder Ani Brown posits a question facing many budget-conscious homeowners on Green Building Advisor (GBA), pointing out that "Ideally one would spend additional money for better installed insulation and on proper air flow controls. But, if additional money is not available for both, what would be best to spend the money on? Better installed insulation like a spray product or better air flow controls?"
According to Peter Yost, GBA's technical director, in a head-to-head match-up between insulation and air-tightness, it's almost no contest:
"Hands down, air sealing, in all climates in all buildings, is priority one, given its impact on indoor air quality and energy performance. It also is really hard to correct air sealing defects after the insulation goes in, so sequencing is another reason for air sealing priority (unless of course your primary air barrier employs the airtight drywall approach — ADA)."
Ideally, the air-tightness of a structure should rate less than 1 change per hour at a pressure of at 50 pascals of pressure (ach50). A measurement of any more than 3 is largely unacceptable, according to Dana Dorsett, who describes a rating of 3 ach50 as "a cakewalk— more of a stripe painted on the floor than a hurdle to clear." With the use of exterior sheathing and interior drywall, making a structure airtight is "almost idiot-proof," Dorsett says, adding that "There's no excuse for performing worse than 3." Lucy Foxworth advises that blower door testing should be conducted before the building is finished, and if possible, twice: once after the installation of doors and windows, and again after drywall is installed.
Homeowners who are concerned about making sure that their houses are constructed in an energy-efficient manner would do best to start with their contractor, according to Brown, who points out that "one can argue that no matter what the product is (batt or spray); if it is installed incorrectly it will be a problem."
To that end, GBA senior editor Martin Holladay suggests inquiring what rating a contractor can typically achieve from a blower door test on their work, although he posits that in the end, proper communication with your builder will be the make-or-break factor. "Ideally, you need to keep looking for a contractor who understands the issues we're talking about, and who cares enough to do a good job," Holladay says, adding that "If you can't find that person, then none of these discussions matters."