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COMFORTWhy is my upstairs so much hotter than downstairs?

Bedroom filled with warm afternoon sunlight
Photo: Thanos Pal / Unsplash

Short answer: the attic, the ducts and the sun. In most two-story DFW homes, the upstairs sits right under a superheated attic, gets its cooling through ducts that run through that attic, and takes the most direct sun. Fix those in the right order and the gap between floors shrinks a lot.

1. The attic is heating your ceilings

On a summer afternoon, your attic can be far hotter than outside. If the insulation is thin, that heat pours down into the upstairs bedrooms and keeps coming after sunset. This is the most common cause we see. ENERGY STAR recommends R-49 for an uninsulated attic in our climate zone. Learn how to check yours in how much attic insulation a DFW home needs.

2. Your ducts run through that hot attic

In many DFW homes, the ducts that carry cool air upstairs run through the attic. ENERGY STAR says a typical duct system loses about 20 to 30% of the air moving through it to leaks, holes and loose connections. Every leak in the attic dumps cool air where it does no good, and poorly insulated ducts pick up heat on the way. The upstairs rooms at the end of those runs get the least.

3. Warm air rises, and the house leaks

Warm air naturally rises to the top floor. Gaps between the top floor and the attic, around recessed lights, the attic hatch and wiring holes, let hot attic air in and pull cooled air out. Air sealing those gaps is the first step of any good attic job.

4. Sun through the upstairs windows

West- and south-facing windows upstairs take hours of direct afternoon sun. Older clear glass lets most of that heat in. Windows with a low Solar Heat Gain Coefficient block much of it. See how to read a window label.

What actually helps

  1. Seal and insulate the attic. Usually the biggest single improvement, and done in a day. Attic insulation & venting
  2. Have the ducts checked. Sealing and insulating attic ducts and balancing airflow to upstairs rooms is HVAC work. A licensed HVAC contractor can test for leaks.
  3. Upgrade the sunniest windows. Start with the west and south sides. Windows
  4. Use simple habits. Close blinds on sunny upstairs windows in the afternoon, run ceiling fans counterclockwise in summer, and keep supply and return vents clear.

What usually doesn't

  • Turning the thermostat way down. Downstairs gets cold while upstairs stays warm, and the bill goes up.
  • Closing downstairs vents. It can unbalance the system and strain your HVAC rather than push more air upstairs.
  • A bigger AC unit. If the attic and ducts are the problem, a larger system cycles harder without fixing the cause.
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The bottom line

A hot upstairs is a whole-house problem, not a thermostat problem. Start where the heat gets in: the attic first, then ducts and the sunniest windows. During a free assessment we'll check your attic and windows and tell you what will close the gap for your budget.

Book a free home assessment

Sources: ENERGY STAR, recommended home insulation R-values; ENERGY STAR, duct sealing.