How Blower Door Testing Can Help Homebuilders
As more and more homeowners and homebuilders seek energy efficient structures, residential codes are responding. As we’ve seen from the standards set in the 2012 and 2015 versions of the International Energy Conservation Code, air tightness standards are significantly higher in order to address energy efficiency. Though currently only nine states have adopted the 2012 IECC and two more have adopted the 2015 version, blower door testing and airtight designs by homebuilders are likely to grow in importance.
What Blower Door Testing Achieves
A blower door test uses a blower door-essentially a powerful fan attached and sealed to a door-to measure the flow rate of air through any cracks in the building envelope. This flow rate of air is produced at a specified pressure, and when certain specifications are met: that the exterior doors or sealed, dampers closed, HVAC turned off, and more. The goal is to find the air changes per hour (ACH) by multiplying the volumetric flow rate from outside (measured in cubic feet per minute) divided by the building volume. The lower the ACH, the more airtight the building is said to be.
Either way, pouring over the results of similarly built and sized homes can help homebuilders achieve tighter building envelopes on new houses. As a result, many homebuilders know that the best places to resolve air leaks are not just in doors and windows, but in the overall construction of unconditioned spaces like basements and attics.
Overall, the emphasis for airtightness must occur in the building stages, and cannot just be resolved at the end with caulk around the windows. In addition, it forces homeowners to consider indoor air quality, which might mean installing mechanical ventilation.
Still, blower door testing has its limitations. For one, it can’t account for all leaks at every moment: there are environmental and climate considerations to be made, so one ACH rating for a house in Washington might not be the goal for a house in Florida. It can and should, however, be used as a tool to find major leaks, reveal overlooked components to the building envelope, and challenge homebuilders to refine the build.
Where Homebuilders Should Pay Attention
As more and more home builders turn to weatherization and energy efficiency professionals for consultation, blower door tests reveal certain constants that can help homebuilders adjust their building envelopes. Not only will it help with energy efficiency, but paying attention to major risk areas can create a more comfortable home and a long-lasting structure.
The U.S. Department of Energy compiled an air leakage guide, which identifies where the greatest leaks can occur, and what measures your blower door test should meet for every zone. At the top of the list for biggest trouble spots is air and thermal barrier alignments, with its greatest effect at breaks and joints that are not sealed. The need for a continuous air barrier installed in the building envelope provides the best protection against leakage. Cracks between partition top plates and drywall should not be overlooked.
Basement and attic insulation also cause a dramatic effect on the comfort of the home. Without addressing air tightness in the basement and attic, homebuilders can also run into moisture control problems, such as an increased risk of mold in basements. Builders should also pay attention to basement rim joist areas, cracks between finished flooring and baseboards, as well as joists. In the basement, builders should consider placing a basement slab down on concrete spread footings, and look into less porous materials for building basement walls. The attic’s heat loss could be addressed by paying attention to the type of insulation, and the insulation’s alignment to the air barrier.
Overall, blower door testing lends itself to higher requirements for air tightness, but with good reason. By understanding blower door tests, homebuilders can avoid common energy efficiency problems, and make the home a more comfortable space overall.
Interested in the design and construction of complete air barrier systems? See our DELTA®-VENT SA Technical Guide which features how to improve heat flow control, condensation control and more.