Builders Need To Get Two Things Right For Energy Efficient Homes
As more states adopt newer versions of the code, HERS Raters are providing key guidance to builders that are tasked to deliver increasingly tight homes.
Home Energy Rating Systems (HERS) Raters can play a central role in helping builders transition to new more stringent residential building energy code requirements, like the 2012 or 2015 International Energy Conservation Code (IECC).
That guidance includes essential training in how to reduce building air leakage.
James Rodriguez of Fox Energy Specialists talks about the two things that may blindside builders when they must meet new code requirements and what builders must do to prepare for compliance. Rodriguez is Executive Vice President of Fox Energy Specialists, a Texas-based company that provides a wide range of energy efficiency consulting services in the residential and commercial construction sector.
In its advisory capacity, Fox helps builders meet code-built specifications and high-performance building program requirements like Zero Energy Ready. Rodriguez said many builders who now must meet more stringent code requirements for air tightness in their new homes are often blindsided by two things that must become the focus of their work in the lead up to the adoption of new codes:
1. Double-Digit Duct Leakage Rates
Testing for duct leakage is an important part of meeting air tightness requirements. Researchers at Lawrence Berkeley National Lab (LBNL) found that duct systems leak on average about 10% of the supply air they move and 12% of the return air of the average home’s heating and cooling energy is wasted through leaks in inefficient duct systems, primarily through leakage in unconditioned attics, crawl spaces, basements, or garages. These leaky duct areas amount to an energy wasting and expensive problem for the homeowners and will impact the builder’s ability to reach new air tightness requirements. Following a basic protocol for duct leakage testing (like this one recommended by Energy Vanguard) can be essential to reducing duct leakage for builders.
After testing duct leakage, Rodriguez recommends that builders whose jurisdictions haven’t yet adopted more stringent energy codes prepare now for compliance. “Spend a couple of months focusing on sealing your ducts to 4 percent leakage rate consistently,” he said.
2. Tightening the Envelope to Target ACH50
Once duct leakage has been reduced to 4 percent, Rodriguez says builders must then address ways to tighten the envelope to target new air leakage targets like 3 ACH50. In the runup to mandated blower door testing, builders need to spend a significant amount of time training with their staff, framers, and contractors to address the critical components of getting tighter assemblies, including quality framing and effective air sealing in key priority areas.
“We typically conduct air sealing training quarterly to refresh applicable trades on proper air sealing techniques and our expectations as HERS raters inspecting each home’s air barrier,” he said. “Builders, framers, and insulation crews are usually the key trades that attend these trainings.”
As a HERS rater providing services for builders in both Climate Zone 2 and Climate Zone 3, Rodriguez noted that 85 to 90 percent of builders in Climate Zone 2, which requires homes reach 5 ACH50, typically pass their blower door test the first time. “5 ACH50 is a very easy airtightness level to achieve with your standard air blocking and sealing techniques.” Builders in Climate Zone 3 with a 3 ACH50 target are having a tougher go of it, with about half passing on the first effort. Rodriguez notes the importance of training, air sealing, and inspection to help builders boost their success with blower door testing on the first attempt.
An Easier Transition in Two Steps
Rodriguez believes that builders who focus first on reducing duct leakage and then on tightening the envelope will learn what areas need additional focus prior to the adoption of the new building energy efficiency code.
“Those two items usually blindside builders when permitting under the more recent codes so focusing on those items and having your homes tested ahead of time will make the transition to the newer code much easier.”