HVAC Filters, Thermostat Settings and Simple Upkeep You Can Do Safely

Check the air filter once a month

ENERGY STAR’s maintenance checklist tells homeowners to “inspect, clean, or change air filters once a month” in a central air conditioner, furnace or heat pump, and says your contractor can show you how. It warns that “a dirty filter can increase energy costs and damage your equipment, leading to early failure.”

If you aren’t sure where your filter is or which size it takes, your contractor can show you at the next check-up, as ENERGY STAR suggests. When you replace it, match the size printed on the old filter’s frame and follow the airflow direction marked on the new one.

Which filter should you buy?

The EPA’s guide to air cleaners in the home says that if you upgrade, choose a filter rated at least MERV 13 (Minimum Efficiency Reporting Value), “or as high a rating as your system fan and filter slot can accommodate,” and that you may need an HVAC technician to tell you what your system can handle.

The EPA also notes that furnace and HVAC filters only clean the air while the system runs, that systems usually run less than 25% of the time during heating and cooling seasons, and that “all filters need regular replacement.”

In our view, if your current filter fits, your system runs normally and you change it on schedule, it may already be the right one. Ask a technician before jumping to a much thicker or higher-rated filter.

Thermostat settings that help

• Smart thermostats. ENERGY STAR says certified smart thermostats can learn your preferences, set back temperatures while you are asleep or away, and use geofencing to adjust when you leave or head home. It notes that almost half of the average household’s annual energy bill goes to heating and cooling.
• Heat pumps are different. ENERGY STAR’s heat pump tips say heat pumps “do not save energy by turning it down when you’re away or asleep”: pick a comfortable temperature and leave it. It also suggests choosing “heat” or “cool” instead of Auto mode, and using the auto fan setting or the lowest fan speed that meets your needs.
• Furnace and AC. A pro check-up should include checking thermostat settings so the system keeps you comfortable when you are home and saves energy while you are away (ENERGY STAR).

Look for leaky ducts

ENERGY STAR says that in a typical house, about 20 to 30 percent of the air moving through the ducts is lost to leaks, holes and poor connections. Signs include high summer and winter bills, rooms that are hard to heat or cool, stuffy rooms, ducts in an attic, crawlspace or garage, and tangled or kinked flexible ducts.

For ducts you can reach safely, ENERGY STAR says to seal leaks with mastic sealant or metal tape and insulate them, and to “never use duct tape, as it is not long-lasting.” Many homeowners hire a contractor for this work.

What a yearly pro check-up should cover

ENERGY STAR recommends annual pre-season check-ups by a contractor: the cooling system in spring and the heating system in fall. Its checklist includes:

• Checking thermostat settings and the system’s start, run and shut-off cycle.
• Tightening electrical connections and measuring voltage and current on motors.
• Lubricating moving parts.
• Checking the condensate drain. A plugged drain can cause water damage and affect indoor humidity.
• Cooling: cleaning the indoor and outdoor coils, checking the refrigerant level, and adjusting blower parts. ENERGY STAR says airflow problems can reduce efficiency by up to 15 percent.
• Heating: checking gas or oil connections, gas pressure, burner combustion and the heat exchanger.

Leave these to licensed pros

Refrigerant work requires an EPA Section 608 certified technician, and venting refrigerant is prohibited. Gas connections and electrical work also belong to licensed professionals; ENERGY STAR lists gas connections, gas pressure and electrical connections among the items a contractor checks.

Monthly and seasonal checklist

• Monthly: look at the filter; clean or replace it if it is dirty.
• Monthly: keep supply and return vents open and unblocked.
• Spring: book the cooling check-up.
• Fall: book the heating check-up.
• Any time: note rooms that are hard to heat or cool, and ask about duct leaks at the next visit.