Q&A with the New Homes team: EPS, building envelopes and bath fans

Trade allies, builders, subcontractors and real estate professionals contact the New Homes team with great questions all the time. Topics range from best practices in new home construction and EPSTM requirements to how to market EPS homes. Here are this month’s featured questions and answers.

Do you have an efficiency or new home construction question we didn’t cover this month? Send it to the New Homes team and it could be included in the next issue of the Insider. Find more information about EPS requirements or energy-efficient new home construction on the Online Residential Training page.

Q: Do I have to follow one of the EPS Paths for a home to receive EPS? Can a home qualify for EPS if I build with a different combination of specifications?
A: You do not have to follow one of the EPS Paths for your home to receive EPS or Energy Trust incentives. EPS Paths present a combination of improvements that other builders have used to achieve energy savings. They serve as a guide and give you an idea of what your Energy Trust incentive might be if you build to a certain level of efficiency. You are free to mix and match your home’s efficiency improvements to suit your design, budget or buyers.

To receive an EPS, you must configure upgrades, build the home to be at least 10 percent better than code and follow EPS requirements. Your verifier can help walk you through the different upgrade options, guide you through EPS requirements and model your home to determine its final efficiency level.

Q: I have heard the terms: building envelope, air barrier, primary air barrier, thermal barrier and weather barrier. What exactly are these and how do they relate?
A: A building envelope, or shell, refers to a home’s roof, exterior walls/siding and foundation. You should easily be able to draw a line around the building envelope when viewing elevations on a blueprint. This envelope is the first line of defense against ambient environmental conditions and works to separate occupants from wind, rain, heat, cold, light and noise.

An air barrier is made up of rigid materials such as oriented strand board and siding. It prevents air from freely entering the conditioned areas of the home.

The primary air barrier is the air enclosure boundary that separates conditioned spaces from unconditioned spaces. A primary air barrier is sometimes referred to as a pressure boundary.

The thermal barrier may be in a different location than the building envelope, and separates conditioned from unconditioned spaces. The air barrier and thermal barrier should always align. This will maximize efficiency, boost comfort and prevent condensation.

The weather barrier is affixed to the building envelope to prevent moisture from intruding into the home or exterior sheathing through bulk water transport, vapor drive and capillary action.

Q: Why is it important to install bath fans/whole-house fans with low sone ratings?
A: As homes are built to tighter standards of air leakage, it’s important to pay attention to the mechanical systems that evacuate ambient moisture. Ineffective systems can result in poor indoor air quality, which could negatively impact the health and well-being of the building occupants.

In addition to the volume air movement rating, CFM, it’s important to also consider the sound made by the fan, which is measured in sones. The sone scale is a linear measurement of how sound is perceived by the human ear. For example, a sound with a sone of 2.5 is perceived as 25 percent louder than a sound with a sone of 2.0.

In general, occupants don’t enjoy the mechanical sound of fans running inside the home environment. However, occupants are more likely to tolerate soft sounds, and are therefore more likely to operate fans for long enough to evacuate moisture. For a home to receive an EPS, all fans located in full baths should not exceed 2.0 sones and whole-house fans should not exceed 1.0 sone.