Heating and cooling in Sioux Falls
In Sioux Falls, heating is the main job. A system here has to keep up through long stretches of deep cold, then handle summers that are hot and sometimes humid.
Design temperatures
NOAA's engineering weather data for Sioux Falls gives a 99% winter design temperature of −11°F (−16°F at 99.6%) and a 1% summer design temperature of 91°F with a mean coincident wet-bulb of 73°F. Contractors use values like these in a load calculation, which sizes equipment to your house. Ask for one; sizing by rule of thumb often leads to oversized furnaces that short-cycle and uneven heat.
Furnaces
High-efficiency gas furnaces vent through plastic pipes and produce condensate. In deep cold, intake and exhaust pipes can ice up, and condensate lines in cold spaces can freeze, shutting the furnace down. Ask where the vents will exit, how they'll be kept clear of snow, and how the condensate line will be protected. Have the furnace serviced before winter.
Heat pumps
South Dakota is in the Department of Energy's North region. Split-system central air conditioners installed since January 1, 2023 must be rated at least 13.4 SEER2, and split-system heat pumps at least 14.3 SEER2 and 7.5 HSPF2. Cold-climate heat pumps can heat in very low temperatures, but output drops as it gets colder. Ask how much heat the proposed unit delivers at −10°F, what backup heat it has (a furnace or electric strips), and how the controls will switch between them.
Summer
NOAA counts about 892 hours a year in Sioux Falls with the wet-bulb temperature above 67°F. Summer isn't as long as in the South, but humid spells happen. An oversized air conditioner cools fast and leaves the house clammy. Ask how the system handles humidity.
Freeze-thaw and the outdoor unit
NOAA lists about 75 freeze-thaw cycles a year and a 50-year ground snow load of 40 pounds per square foot. Heat pump outdoor units need to sit high enough that snow and ice don't block them, and defrost water needs somewhere to drain. Ask how the unit will be mounted.
Comparing quotes
Ask each contractor for equipment model numbers, efficiency ratings, the load calculation, ductwork changes, venting, thermostat, permits and warranty terms. Ask who registers the warranty and what maintenance it requires.