Case Study
This new construction, EarthCraft-certified, single-family home in Glen Allen, VA, has an impressive HERS index of 52, indicating that it’s 48% more efficient than a house built to code.
A number of efficiency improvements contributed to this low HERS index. The crawlspace was conditioned, and the 1st-floor air handler is located there, keeping it in conditioned space. Instead of using oriented strand board (OSB) for sheathing, R-3 structurally insulated sheathing (SIS) was used in its place. Using SIS minimizes thermal bridging and improves the R-value of the wall assembly, making it a smart improvement over OSB.
The properties of SIS also mean that house wrap is not required, saving the builder a step while still providing a moisture barrier. Since SIS has its seams taped, it contributes to a tighter building envelope. This house tested in at a notable 2.5 ACH50.
With a tight envelope, proper ventilation and safe combustion practices are essential. Supply-side ventilation is provided. The furnace and tankless water heater are high-efficiency condensing models, greatly reducing the chances of any combustion byproducts affecting the occupants. A tight envelope also contributes to occupant comfort, as do the well-designed and well-sealed duct systems. Overall duct leakage in the house was less than 3% to the outside of the home and less than 6% total.
Fresh air is provided in energy-efficient homes to promote healthy indoor environments with superior indoor air quality compared to standard housing. Ventilation systems consist of a fresh air system to provide odor control to occupants and dilute stale air, as well as intermittent, spot exhaust systems (e.g., bath fans and ducted kitchen range hoods) to remove point-source pollutants from the indoor environment. It is critical to occupant health and building durability to optimize the ventilation systems based on human factors and climate.
Ventilation is provided to Bain-Waring’s home according to ASHRAE Standard 62.2 Ventilation for Acceptable Indoor Air Quality. The fresh air system is a Central Fan Integrated System (CFIS) consisting of an AprilAire mechanical damper and controller programmed to provide fresh air ventilation through the heating and cooling system based on the size of the home and the number of occupants. While there are several companies that manufacture the CFIS technology, Bain-Waring utilizes the AprilAire system due to its high/low temperature and high humidity lockout feature. This feature prevents fresh air from being brought in and distributed throughout the home when the outdoor conditions risk comfort and/or durability issues within the home.
A Sense energy monitor was installed in this home, allowing real-time energy usage to be seen. The device installs in the electrical panel box and has an app to see energy use as it happens, as well as historical data.
When lights turn on and off, or when the central air turns on, the app will show the change in usage and quantify it.
One of the selling points of the Sense is its ability to start to detect which devices in your home are using energy. When first installed, a grey circle shows on one of the app screens, simply labeled “unknown.”
As the Sense gets more data, usually after a week, additional circles will appear. For example, you may see one named “dishwasher” and one named “television.”
For example, you may see one named “dishwasher” and one named “television.”
The size of the circles is based on the amount of energy the device uses. Over time, you’ll have a visual representation of what is using energy in your home and how much.
Armed with this information, it’s possible to find devices that may be using more energy than they should, or devices that are on when they shouldn’t be.
If you have solar panels, this data can also help you see if it’s worthwhile to shift some energy usage to daylight hours, when the solar panels are producing energy. It may also help shape your energy usage behaviors.
Let us help you achieve outstanding results like those showcased in this case study.
