Q. With the spate of hot weather during recent days, one of my sons asked me whether an attic fan was a good investment to significantly decrease the temperature in the upstairs bedrooms. He and his family recently bought a new home with a pitched roof. I'm sure his attic venting system is working as designed but it does little to keep the upstairs cool. He reminded me when we lived in our house in California a number of years ago I designed and installed a system in which I used two 12 inch attic fa ns to draw the cooler air through the roof-line vents and exhausted the hotter air out a vertical attic vent. The system seemed to help since it constantly kept the cooler air moving through the attic. I also installed a temperature cut-off switch in ca se of fire.

Is there anything on the market today that can reduce the heat in the attic thereby reducing the temperature in the upstairs bedrooms? A neighbor of his who has the same problem is looking into getting a contractor to install a separate air-conditioning system for the upstairs, but I'm sure it will be costly. And I know that exhausting the cooler air from the house by use of an exhaust fan into the attic isn't the answer, either. What is your advice?

A. I’m glad you haven’t advised your son to go out and spend money on something that intuitively makes sense but in reality may not. There are a few things going on here simultaneously that need to be separated and examined before any course of action is taken involving a cash outlay. It’s not rocket science to notice that the upstairs bedrooms, especially if the doors are closed but not necessarily, are warmer than the living spaces on the first floor. And it’s a real safe bet if the temperature outsi de is hovering near 100º that the space in the attic will be well above 120º if the sun’s shining. Your son’s house is new so it was insulated to today’s standards which is quite adequate, so no need to upgrade there. In fact, the insulation in the att ic is placed directly over the bedroom ceiling’s drywall and is providing a thermal a barrier between house temperature and attic temperature. Venting the attic beyond what was built in during construction shouldn’t have any impact on the interior temp eratures. What’s needed is better air-mixing of the conditioned air in the house. Because the house is so well insulated, the heating and cooling system doesn’t have work as hard as it would in a leakier, less insulated old house. In such an older hous e the system would run almost constantly and, sure, it would feel cool. I’ll bet if you asked your son to time how many minutes an hour the system ran you’d be surprised at how little it really works. But the key is the system is responding to a thermo stat located in a living or dining room downstairs. Between A/C run times warmer air stratifies and migrates upstairs and hence the warmer bedrooms. Instead of buying a fan to install in the attic, he already has the fan he needs. It’s in the HVAC syst em. Have your son set the controls on the thermostat to the fan ON position. Doing that will move the around throughout the house even when the system is not providing cooling but will add cooling if the thermostat senses air above the temperature sett ing. It will use about the same electricity as any attic fan and the consumption is about equal to burning a 100 watt light bulb. Have your son place a thermometer upstairs and check the differences between there and the thermostat with the fan running constantly. I’ll bet it won’t vary more than one or two degrees. The added benefit, other than not spending a dime for a new fan, is he will avoid putting a running electric motor up in the attic that can potentially burn out one day and burn the house. It’s for that reason and other considerations make me shy away from powered attic ventilators (PAV) but they sell them and people use them.

Q. I had a roof ridge vent installed on my home which before that I had 16 inch wide soffit vents,front and rear--4 each side, house length 44 ft.--gable vents at each end and an electric powered gable fan at one end.

With the energy cost of electricity, do I need the electric powered fan and if I don't, how hard is it to disconnect it from the power source?

A. No, you don’t need the fan. And in fact if you now have ridge and soffit vents-- the current state of the art venting arrangement for the roof system you have-- you need to block off the gable end vents as they will tend to work against the new syste m creating dead air spaces in the attic. As for disconnecting the fan, you could just set the on/off limits way out so that it would never cycle on or, making sure the circuit is dead, go into the junction box near it and disconnect the wires.