*PLUMBERSSTOCK EXPERT* responded:
Hi! Thank you for asking help from the PlumbersStock team! In order to determine the properly sized unit, your heating and air company or utility company will need to conduct a Manual J load calculation on your home. This load calculation uses many variables (ex: square footage, insulation, windows, etc.) to determine what is the proper size unit. We hope this helps. If you're interested in purchasing the Ducane 80G1DF070AP12 Single Stage Downflow Gas Furnace, just click the "Add to Cart" button, enter your zip code and you'll be all set. Thank you for visiting PlumbersStock.com. Have a great day!