Home Energy TechTips

When sealed tightly, sized properly, and installed with adequate filtration, ducts do a great job at delivering conditioned air to a space. However, in an old house with years of use and neglect, it’s easy to go 0 for 3 on these functions. A full replacement of a duct system can be highly invasive and very expensive. So, the next best thing is improving the air sealing of the system; but when ducts are behind walls, in floor cavities, and generally inaccessible, they can be very difficult to seal. Enter aerosolized sealing.

By spraying an aerosolized sealant into a pressurized duct system, technicians can seal tiny leaks within ducts. “But how does the sealant know where to go?” Good question. The holes in ducts that allow air out under pressure also allow the sealant to travel directly to the leaks. To make an effective seal, you have to first have a clean surface, so that’s how the process starts. After cleaning the ducts (and in this case, it was long overdue), the supply registers are sealed, and the supply plenum is also capped just above the indoor heat pump unit. Using a fan, a compressor, and a spray nozzle, the sealant is released into the ducts in an as an aerosolized spray. Technicians monitor the air leakage through the ducts, and when leakage bottoms out, it’s time to unhook the system and perform the same steps on the return ducts. The system works best when addressing small holes, but does have its limitations – like in the case of large holes or disconnected ducts. Even with the aerosolized sealant doing the work, the job takes a long time when dealing with an old duct system, about 8 hours for a 2 man crew. So, tomorrow they’ll be back tomorrow to complete the sealing of the second duct system.

Other accomplishments for the day included diagnostic testing on duct leakage to outdoors (tests to be completed pre- and post-duct sealing efforts), and installation of several occupancy lighting sensors throughout the house.

On deck for Friday: Air sealing, attic insulation, duct cleaning, aerosolized sealing, and new outdoor lighting fixtures with photo sensors.

With a window of just five days to reach 40% energy savings, the retrofit work continued today, despite the rain in D.C. The dedicated HVAC crew overcame slippery roofs, cramped closets, and decades old equipment in installing new, high performance heat pumps. Old heat pump units had a nameplate cooling efficiency rating of 13 and 10 SEER, and were expected to have even lower efficiency performance due to the age of the equipment and lack of regular maintenance. In fact, one of the units had a date of 1979 on its wiring diagram, which just happens to be the same year that Sony released the Walkman. Time for a change out, anybody?

The new units are rated at over 17 SEER in cooling, with a heating season performance factor of almost 9. While both interior and exterior units are set in place, there are a couple more details to finalize before the new heat pumps are up and running: installation of condensate pumps (as required by code), digital programmable thermostats (allow you better resolution than a +/- 5 degrees Fahrenheit set point), and drain pans.

We also completed the installation of state data loggers on each window within the home - over 30! The loggers will record window open/closed operation, which can be overlaid with heat pump energy use to determine if the building is being managed efficiently (i.e., no heat pump operation when windows are open), or if there are opportunities for greater energy savings through better window management. And no, unfortunately the loggers do not beep or ask, “Do you live in a barn?” when tripped.

After a long day of work, Sasha Bruce and the Home Builders Care Foundation hosted a reception to provide some education on the project and give us an opportunity to thank Walmart, HomeAid America, and the Department of Energy for their generosity in making this project a reality. Staff were excited to hear that they could realize up to 45% energy savings at the home once the retrofit is completed. And the residents were especially excited to eat
brownies before dinner.

On deck: Tomorrow should see the completion of the ASHP installation and the beginning of air sealing efforts. It will be interesting to see what we find in the attic, as part of this home was constructed before the turn of the century. Yes - that’s the 19th century, kiddos. We’ll keep you posted.

The energy retrofit of the Sasha Bruce House has officially begun!  The old vinyl windows on the front of the home, which were in poor condition and a source of air leakage, were replaced with new double pane vinyl windows with a U-factor of 0.32.  After the windows were set in place, they were caulked from the inside along the trim.  Tomorrow, the remaining windows will be installed (20 total on the south side of the building), and all of the windows will be spray foamed and flashed from the exterior, to enhance air sealing and ensure that the windows are able to effectively shed water.

Each of the windows was installed with a state data logger to monitor window operation (open/closed).  These data will complement data being collected on indoor temperature, outdoor temperature, and heat pump energy use to help us determine if the new heat pumps are operating as efficiently as expected.  Also, the window data loggers will tell us if the windows are being operated as a complement to the air source heat pumps (e.g. taking advantage of cool outdoor temperatures for air conditioning), or if the open windows are simply making the heat pump work harder (e.g., open while it’s hot outside and the heat pump is running).

On deck: Tuesday should bring the completion of the window installation and the installation of the first of two high efficiency air source heat pumps.