How to Balance Temperatures in a Two-Story Home

Short answer: Heat rises, so in a two-story home the upstairs runs warmer, which feels worse in summer and better in winter. Start with the simple fixes: keep every vent and return open and clear, change the filter, try the fan on On for steadier mixing, and use blinds on sun-facing windows. If one floor is still several degrees off, the usual causes are duct leaks or undersized runs to the second floor, too few returns upstairs, or one system trying to serve two floors, which a technician can measure and fix with duct work, dampers or zoning.

Safety first: if you smell gas (a rotten-egg smell), leave the house now and call 911 or Southwest Gas from outside. If a carbon monoxide alarm sounds, get everyone out and call 911 from outside. A dusty or oily smell the first time the heat runs each season is normal and can linger for a couple of days.

Why two floors run at different temperatures

A few things work against an even house:

• Warm air rises. Upstairs collects heat from the floor below.
• The roof. Upstairs rooms sit right under the attic, and in Las Vegas summers the attic gets very hot. NOAA's 1991–2020 normals put the average July high at Las Vegas's airport station at 104.5°F.
• Long duct runs. In many two-story homes, ducts to the upper floor are the longest runs and often pass through the attic. Longer runs lose more air and more heating or cooling along the way.
• Returns. If the upstairs has few return vents, or only one in a hallway, air pushed into closed bedrooms has a hard time getting back to the system.
• One thermostat. A single thermostat downstairs is satisfied when the downstairs is comfortable, even if the upstairs isn't.

In winter, the picture flips: the upstairs may be fine while the downstairs, especially rooms over a slab or near large windows, runs cool. NOAA's normals put the average January low at 40.5°F, so mornings are when you'll feel it.

Steps you can take yourself

1. Open and clear every vent and return

Closing downstairs vents to push more air upstairs sounds logical, but closing too many can raise duct pressure, cut total airflow and make the system work harder. Keep supplies open, and make sure furniture, rugs and curtains aren't blocking vents or returns.

2. Change the filter

A clogged filter cuts airflow everywhere, and the farthest rooms, usually upstairs, lose the most. Desert dust loads filters faster than people expect. See how to find your air filter size.

3. Try the fan on On

Running the blower continuously keeps air mixing between floors, which can narrow the gap. It does run the blower more hours, so try it and see if the difference is worth it to you. Our thermostat guide covers fan settings.

4. Adjust the thermostat schedule

Some households set the system a couple of degrees cooler in summer during the hours they're upstairs, such as bedtime. A smart thermostat with a remote sensor upstairs can average the two floors or favor the one you're using.

5. Manage the sun

Close blinds or shades on west- and south-facing upstairs windows in the afternoon. Window film or solar screens can help too.

6. Keep doors open, or add a path for air

Closed bedroom doors with no return in the room can trap supply air. Leave doors open, or ask a technician about adding a return or a transfer grille.

What a technician can do

If one floor is still uncomfortable after the basics, the cause is usually in the system or ducts, and it can be measured:

• Airflow testing at each vent to see which rooms are short.
• Duct inspection and sealing for leaks, kinks or disconnected sections in the attic. See our ductwork problems guide.
• Balancing dampers in the duct trunk to set how much air goes to each floor. Some homes benefit from adjusting them seasonally, more upstairs in summer and more downstairs in winter.
• Added or larger returns upstairs.
• Zoning, which uses motorized dampers and a thermostat on each floor so one system can serve both.
• A second system for the upper floor, in some larger homes.
• Checking the equipment itself. If the system can't keep up on the hottest days, see our AC not keeping up guide.

A seasonal check, like our furnace tune-up, is a good time to have airflow and dampers looked at too.

Spring Valley and Rhodes Ranch homes

Spring Valley is an unincorporated town in Clark County, west of the Las Vegas Strip, and Rhodes Ranch is a community within it in the southwest valley. In older homes anywhere in the valley, the ductwork may be original to the house, so it is worth having it checked. If you live in a two-story home there and one floor never feels right, the steps above apply. See our Spring Valley service area page for local service.

FAQ

Why is my upstairs so much hotter than downstairs?

Warm air rises, upstairs rooms sit under a hot attic, and the duct runs to the second floor are often the longest. A single thermostat downstairs also stops cooling once the downstairs is comfortable.

Should I close downstairs vents to cool the upstairs?

Closing a lot of vents can raise duct pressure, cut total airflow and strain the system. Keep supplies open. If you need more air upstairs, a technician can adjust balancing dampers or improve the ducts.

Does running the fan on On help a two-story home?

It can. Continuous fan keeps air mixing between floors and can narrow the temperature gap. It runs the blower more hours, so see whether the comfort difference is worth it.

What is zoning in a two-story home?

Zoning uses motorized dampers in the ducts and a thermostat on each floor, so one heating and cooling system can send air where it's needed instead of treating the house as one space.

Why is my downstairs cold in winter?

Heat rises to the second floor, and downstairs rooms over a slab or near large windows lose heat faster. Adjusting dampers to send more air downstairs in winter can help.

What hours can I reach Colton?

Colton Air Conditioning is open Monday to Friday, 8am to 5pm. You can call or book online during those hours.

Colton Air Conditioning

Colton Air Conditioning, 6545 S. Fort Apache Rd Ste 135 #467, Las Vegas, NV 89148. Nevada contractor license 0092120. Hours: Monday to Friday, 8am to 5pm. Call (702) 738-6976 or book online during those hours.

Want routine maintenance on a schedule? See our Comfort Club maintenance plans: Gold, Platinum and Diamond tiers are all listed there.