HVAC Thermal image showing heat loss

Published on July 12th, 2016 | by Henri


Heat and AC not getting to 2nd floor

Q.  I live in a Colonial house which has 2 floors. In winter the first floor gets warm quickly by gas heat and in summer cools off quickly too when we turn on air conditioner. However the second floor stays cool in winter and warm/hot in summer. If I increase heat more in winter first floor gets too hot and vice versa in summer.

I installed an attic fan last summer but it does not seem to make much difference. I was thinking about adding an extra layer of rolled insulation sheet/roll (not the blow-in) on top of the existing insulation in the attic. Do you think that would help?

Currently I have one layer or R25 insulation in the attic which is about 20 years old. Any suggestion which would help me regarding this matter will be greatly appreciated. I have single zone central heating-a/c system for the whole house and the unit is fairly new (5 years old) for both heat and AC. Thank you.

A. Unless there is adequate net free ventilation area (NFVA) to supply the fan’s cubic feet per minute (CFM) rating, an attic fan generally gets the difference in air that it needs from the conditioned space.

Assuming that you use the attic fan only in the summer, this may be why the second floor is not staying cool. The fan sucks air in from the rooms below the attic, and in turn, warm, outside air is sucked in through any cracks around windows, etc.

But if you also use the attic fan in the winter to remove moisture from the attic, the fan sucks up warm air from the living space as well.

Adding insulation to the attic’s floor is a very good idea, as it will help through both summer and winter. You should aim for an R-factor of no less than 38. But why won’t you consider cellulose? It will be a lot easier to blow it in than carting bags of fiberglass batts to the attic and laying them down. Another advantage of cellulose is that it is a recycled material, and it will fill in areas that may not be possible to cover with fiberglass.

You should also make sure that there aren’t convective paths from the second floor to the attic that rob heated air from the rooms by the stack effect that occurs in winter. These paths can be around an access panel or disappearing stairway to the attic that is not weatherstripped and insulated. It can also occur around ceiling fixtures, especially the recessed kind. They should be sealed.

An energy audit is the best way to locate these paths and to seal them.

Finally, you may want to have a heating/air-conditioning contractor balance your system.

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