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Heating & Air Conditioning

Central Air through old ducts or what?

13 years ago

I am at lost. Please help!

I've been thinking of adding central air conditioning to my 1950 colonial(~2500 sqft) but couldn't decide what to do. The house has forced air system for heating so the intuitive and easist way is to install a central air unit and use the exsiting ductwork. However, I seriously doubt it will work well because the temperature imbalance in my house.

1. The upstairs is 10+ degree warmer than downstairs in a hot day. We could improve insulation in attic but current status looks decent to me. In fact downstairs is always cool during summer because my house is surrounded by trees. However, the trees are not tall enough to shed any shade on our roof so the upstairs is hot. In order to cool down upstair bedrooms, the downstairs is probably very cold. Beside, there are vents in basement which does not need any cooling what so ever.

2. The exisiting ducts has it's problem. There is one bedroom upstairs always a lot colder than others. The air comes out from vent is not warm at all in winter. I suspect the room is sitting at the far end of the ducts. Unfortunately this room is the hottest room in summer nights because it has 2 windows facing south and one facing west. My gut feeling is it will still be a lot warmer than other bedrooms in the summer after the central air in on.

It will be big energy waste to cool the 2/3 of house to a freezing point just to cool down the bedrooms to sleep in. Zoning is not easy as I understood. And some people say it doesn't work so well without a separate unit for different zones. Let along the costs! Now I am looking at mini-split system but don't know how it works out for the whole house. I like the way it saves energy by separate controls. I guess I will need one air handler for each room. That sounds a lot because I would need 7 or 8 to put in my house. On another thought, it seems strange that we have the central heating already but putting on a separate cooling system without using the ducts.

Installation cost is an important concern too. I know I am asking too much: comfortness, low cost, energy saving... Please please help me find a balanced solution.

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Comments (2)

david_cary
13 years ago
Ok - do you have access to existing ducts?

Do you have dampers on existing ducts?

You don't really need a/c downstairs, right? Because then maybe a few minisplits is the answer.

Dampers are cheap (as dirt) and with some seasonal readjustment, are probably your best bet. A few new ducts perhaps to even it all out.

You could put a system in that is sized to just upstairs and close all the dampers to the downstairs in the summer. Or the dampers could be mostly closed. Normally this might be an issue but if you undersize the a/c, I don't see why there would be a problem.
milkyj
Original Author
13 years ago
I looked at our ducts. There is no damper. The main ducts is accessible from basement so maybe we can install dampers there? Thank you very much David. Your solution sounds very reasonable to me.
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