Furnace & AC Sizing
A rough heating and cooling size for your home, with the BTU-per-square-foot set from how cold and hot your local climate actually runs. Enough to sanity-check a contractor's quote, not a substitute for a proper load calculation.
Insulation & air sealing
Set your place to read your climate's heating and cooling demand.
How the size is set
Heating and cooling needs scale with floor area and with climate. The rough rules of thumb run from about twenty BTU per square foot of heating in a mild winter to fifty or sixty in a cold one, and fifteen to thirty for cooling depending on summer heat. We read your station's coldest and warmest months to pick where on that range you sit, then adjust for insulation. It is a screening number: a real installer runs a Manual J load calculation on your actual windows, orientation, and air leakage, and that is the size to buy by.
Rules of thumb from the U.S. Department of Energy, ENERGY STAR, and ASHRAE climate-zone guidance. Informational only, not a Manual J load calculation. Oversizing wastes money and short-cycles; size with a professional.