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If your HVAC technician wants to size a new furnace for your home by its square footage alone, or using some other discredited “rule of thumb” method, you should change technicians. Furnace sizing involves an engineering methodology developed by the Air Conditioning Contractors of America (ACCA), which has been time-tested and energy-budget approved. Here’s why and how.
Heat Gain, Heat Loss
A home’s heat gain/loss totals the heating load placed on the furnace. A new furnace should be sized to meet the load, or it will be over- or undersized. For instance, take two very similar homes, in terms of floor plan and square footage, located in the same neighborhood; the old rule-of-thumb furnace sizing method would result in the same size furnace installed in each home.
However, what about the heat gain/loss properties? Perhaps each home has a different orientation to the sun. One home has Energy Star-qualified windows, and has undergone air sealing and insulation upgrades. The other home has not. It is likely each home will require a different size furnace. Here’s why:
Furnace Sizing
These are the basic steps you and your HVAC contractor should take when sizing your new furnace:
For complete details about proper furnace sizing for your Portland area home, please contact us at Roth Home & Cooling.