Energy Efficiency Empowerment (E3) audited an already completed project by the Pittsburgh Housing Development Corporation (PHDC) and immediately admired this beautifully finished 1,174 sq. ft. Beltzhoover home, powered by a 3-ton Mitsubishi heat pump. However, the measured air leakage (21 ACH@50) indicated room for improvement. The basement rim joists have since been air sealed.
Using a TrueFlow grid to measure HVAC duct airflow, we discovered that the return duct was restricting flow to only 673 CFM, when 910 CFM was required for this heat pump. To address this issue, a new return register was added, and several ducts were expanded. Allowing for an easy air flow through the ducts is important for energy efficiency – obviously, the blower motor works less, when it is easy to push the air.
PHDC’s vision of an all-electric home—with heat pumps for both space and water heating—substantially reduced energy use, which is a great achievement. However, E3’s modeling predicted a significant increase in utility costs compared to heating with a gas furnace. Therefore, our third intervention involved adding a 3.5 kW solar array, scheduled for completion in the coming months.
Results (including solar):
Air leakage reduced to 14 ACH@50 (2,298 CFM@50)
Home Energy Score improved from 7 to 10
Energy reduction: an additional 44% beyond PHDC’s original achievement
Utility cost reduction: $930/year over PHDC’s original
Additional cost (beyond PHDC’s rehab budget): $17,000
