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Q: The upstairs bedrooms in my two-story house are always significantly warmer than on the main level. Is there any way to combat this?

A: It's no mystery why upstairs rooms get hotter than downstairs ones: Heat rises. But it also moves in other directions, and for the top floor of a house, a lot of heat also comes down from the attic.

And, yes, there are things you can do to make your bedrooms more comfortable. Some are simple and cheap; others are costly.

First, the quick fixes:

Close shades or drapes, especially during the hours when the sun hits windows directly. Do this downstairs and upstairs, because it will reduce the load on your air conditioning system. Exterior shades are even more efficient at blocking heat, because they keep the glass cooler, but they are generally practical only for ground-floor windows. Depending on your house's floor plan and how you use the upstairs, you can also keep the doors to the hottest rooms closed, so that the others stay more comfortable.

Also, take advantage of fans, which use relatively little energy compared with air conditioners. Adjust the fan setting on your thermostat to "on," not "auto." This will make the blower fan circulate all the time, which can help to even out temperatures throughout the house. You might also experiment with closing a few vents on the ground floor, so more cool air goes to the upper levels.

Adding a fan in each bedroom and switching it on when people are in the room can make a dramatic difference. A fan doesn't lower air temperature, and running it in a vacant room can raise the temperature slightly because of the heat from the motor. But when a room is occupied, the moving air boosts evaporation from your skin, even when you don't seem to be sweating, and the change from liquid water to water vapor pulls heat away from your body.

Ceiling fans are terrific and can be relatively simple to install in rooms that have a ceiling light and access to the ceiling above to install enough bracing to support the fan's weight. That's usually easy on upper floors, because of attics. Be sure to purchase a fan that matches the size of the room and is appropriate for the ceiling's height.

If installing ceiling fans is too complicated, or if you are a renter, mimic the gentle breeze that a ceiling fan would deliver by purchasing an oscillating fan on a stand, such as the Lasko Cyclone pedestal fan ($44.98 at Home Depot).

If the upstairs rooms are still too hot for comfort, ask a company that specializes in heating and air conditioning to check the ducts and air conditioner. If the ducts leak or are undersized, or if the air conditioner is more than 15 years old, a system upgrade might make a big difference.

Tim Capps of Capps Mechanical in Huntingtown, Md., said ducts serving upper levels are often undersized, which results in those floors getting less cool air than they need. But breaking into walls to redo ducts would cause a lot of collateral damage to drywall, so a better solution would be to supplement the existing system by installing a ductless system for upstairs.

A single-zone ductless system would start at around $5,000. Or, depending on your house, you might want a multi-zone ductless system, with a single heat pump outside connected via two pipes to each indoor unit. A Mitsubishi Hyper-Heating system that serves up to eight zones and delivers 100% of the heat you'd need in cold weather down to 5 degrees Fahrenheit would cost about $20,000, including installation, Capps said.

The system automatically adjusts depending on how many zones are switched on, so you wouldn't have to run it in every bedroom if some are used only occasionally. And if you don't typically use the bedrooms during the day, you could set a programmable thermostat in each room to switch on close to the bedtime of that room's occupant and to turn off in the morning.

Capps also recommends installing attic fans or calling an insulation company to give you a bid on installing spray foam insulation on the attic side of the roof. That would keep the attic much cooler, reducing the heat transfer from the attic to upper-level rooms.