Heating and cooling in Huntsville
In Huntsville, air conditioning carries the heavier load, but winter brings real cold snaps. A system has to remove a lot of moisture in summer and still keep up when temperatures drop.
Design temperatures
NOAA's engineering weather data for the Huntsville airport station gives a 1% summer design temperature of 92°F with a mean coincident wet-bulb of 75°F, and a 99% winter design temperature of 20°F (15°F at 99.6%). Contractors use values like these in a load calculation, which sizes the system to the house. Ask for a load calculation; a system sized by rule of thumb is often too big.
Humidity
NOAA counts about 935 hours a year at the Huntsville station with the wet-bulb temperature above 73°F. An oversized air conditioner cools the house quickly and shuts off before it removes much moisture, leaving the air cool but clammy. Ask how the proposed system handles humidity: variable-speed or two-stage equipment, fan settings and whether a separate dehumidifier makes sense for your house. Ask the contractor to check the condensate drain and pan, since a clogged drain is a common summer service call.
Efficiency rules
Alabama is in the Department of Energy's hot-humid Southeast region. Split-system central air conditioners installed on or after January 1, 2023 must be rated at least 14.3 SEER2 (13.8 SEER2 for 45,000 Btu/h and larger), and split-system heat pumps must meet 14.3 SEER2 and 7.5 HSPF2 nationwide. Higher ratings cost more up front and less to run; ask the contractor to estimate the difference for your home.
Heat pumps and cold snaps
Heat pumps work well most of the winter here, but output drops in hard cold. On February 25, 2015, the National Weather Service reported 5 to 12 inches of snow across most of north Alabama, and cold spells like that test any system. Ask how much heat the proposed heat pump delivers at low temperatures, what backup heat it has, and how the thermostat will manage it so the backup doesn't run more than necessary.
Ducts
Many Huntsville homes have ducts in hot attics or damp crawlspaces. Leaky ducts there waste cooling and pull in humid air. Ask the contractor to test or at least inspect the ducts, and to quote sealing separately.
Comparing quotes
Ask each contractor for the same information: equipment model numbers, efficiency ratings, load calculation, duct work, thermostat, permit and warranty terms for parts and labor. Ask who registers the warranty.