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old house / central air..

I have an old house from the 40's in northern VA. In the summer, the attic is quite hot. The house has central ac through the same ducts as the heat. Worst case, I think I may buy a portable AC unit to help the finished attic out. It may be possible to upgrade the insulation at some point, but my budget is limited.. so between now and then, I was curious about your experience with duct boosters to try and bring more of the cold air from a very efficient a/c unit upstairs?

A. Spruce
Re: old house / central air..

You might want to look into a "dual zone" system, which if I understand them right is just a damper in the downstairs duct controlled by thermostat. What it does is divert more cooling to the upstairs, since heat rises the second floor is the hardest to cool and would require more airflow than the downstairs.

Re: old house / central air..

To expand a little to A.Spruce"s post .... warm air rises because it is less dense than cold air. Because cold air is more dense it sinks allowing for the lower level of the home to be cooler than the upstairs level.

With a dual zone damper setup two thermostats will control dampers ... one for the lower level and one for the upper level.

When the central A/C unit turns on cool air will flow through the ducts like normal until the lower thermostat reaches the setting ..... instead of turning off the A/C it closes a damper for that level continuing to cool the upper level.

The A/C with continue to run until the upper thermostat reaches the set point without freezing the lower level.

Since you already have central A/C it may be a viable option to consider ... though it may be a bit more than buying a potable A/C unit.

Re: old house / central air..

The zoning may provide you with a satisfactory level of cooling to both levels as long as both levels are not calling for cooling at the same time. The second floor system will require its own duct (supply and return) so that if calling for airflow you can get the required amount where it needs to go.

A professional should be able to go through the house and make the proper recommendations that result in the best possible operating system.

all the best, Irishmist

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