Many homeowners and business owners have added energy efficient upgrades to reduce their environmental impact. Double-paned windows and high quality insulation can decrease the amount that owners spend on heating and cooling costs. These efforts are also more environmentally friendly because energy is not lost due to leaks. However, many owners don’t take into consideration the impact that these improvement have on the HVAC system of the home or business.
Energy efficient improvements change the heat load of the house. In fact, the US Department of Energy calculated how much the heat load of a 2000 square foot house in North Carolina would change with energy efficient improvements. The hypothetical house improved the insulation in the ceiling and walls, upgraded to double-paned glass, increased the window overhangs and eliminated duct leakage by moving the ducts into the conditioned space. Before the updates, the house’s heat load would have been 46,100 Btu/hr by the Manual J calculation. After the updates, it would have been only 21,300 Btu/hr. The energy efficient upgrades cut the heat load in half!
Unfortunately, many people don’t realize the impact that this heat load reduction has on the HVAC system. In the original home, a 4 – 5 ton HVAC system would have been installed. This large HVAC system would have been appropriately sized for the home. However, HVACs are sized based on the heat load. Therefore, after improvements, the proper HVAC sizing would be 2 tons. If the HVAC system is not upgraded with the rest of the house, it will not be properly sized for maximum efficiency.
The Department of Energy evaluated how much energy savings would result if the HVAC system was upgraded with the rest of the house. With a new 2 ton HVAC system, the homeowners would save 63 percent on heating energy and 53 percent on cooling energy. If the homeowners did the rest of the upgrades but did not upgrade the HVAC system, they would save 54 percent on heating and 47 percent on cooling. It does save energy to do the other upgrades, but homeowners that match the HVAC system to the current heat load gain an extra 10 percent increase in energy efficiency.
Long lasting HVAC systems are often not included in home and business energy efficiency upgrades. However, they should be. As the heat load of the home or business changes, the HVAC system should be matched to the needs. A right-sized HVAC system could boost the energy efficiency of the home by 10 percent.