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Discussion Starter · #1 ·
Hi guys, I have a question. I recently had a new HVAC system with all new duct work. Previously, my air flow was not very good. The bedrooms did not cool down like rest of the house and some of my vents that I have in the ceilings either had zero air flow or very weak air flow.

The HVAC company I used said the duct work needed to be replaced. Upon replacing it, they found that there were complete blockages and that the previous duct work was not installed properly. That is why I had bad/weak air flow. They showed me pictures of what they saw in the attic and explained to me how there were blockages and improper installation. Also, the HVAC company told me the old duct work was improperly sized for my house, which contributed to the air flow problems. There is no doubt that the duct work needed to be replaced and the pictures corroborate what they said.

Since the new duct work was installed, my wife and I feel air coming through the vents where we never felt air (I'm in New York and it's winter here at this time). We asked the HVAC company and they explained that because we now have new duct work with proper air flow, the cold air that's in the attic will pass through ducts whereas it didn't before. Thus, we may feel air pass through at times. They recommended that we manually close each vent so that air passing through does not enter into the rooms (and to reopen the vents when the weather warms up and we are ready to turn on the AC).

There are some vents that you can't "close," yet I feel air passing through. I was just wondering if this is a normal thing. I did not grow up in a house with central air, so I couldn't tell you if this is a normal thing in a home with proper duct work for central air.

It doesn't make sense to me why I would feel air circulating in the winter time, when the AC is off, bringing cool air into my home, when I have the heat on to keep those rooms warm.

The HVAC company I hired is very reputable and was very highly recommended by numerous people in my community. I'm not fully doubting what they told me, but I'm just seeking either corroboration or maybe a better explanation of what's taking place.

Thank you.
 

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Were all ducts air sealed and insulated? AC ducts in a hot attic need a lot of insulation and all seams should have been sealed.
Cold air coming from ceiling registers can mean warm air from the house is moving in to replace it and that can cause condensation.

Bud
 

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Discussion Starter · #3 ·
I don't know the answer to your question, but I remember them telling me the new air ducts would be insulated when we talked about replacing the air ducts.
 

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Sounds like they installed flex ducts instead of metal (the cheap and quick approach) and although flex is insulated there are different thicknesses and even the best is minimal.

Then make magnetic sheets that can be cut to fit to cover registers and help reduce the drafts.

Bud
 

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You can have air cooling down in the ducts when the system is off and coming out - natural convection effect.

if you notice it more when it's windy, probably due to leakage instead.
 
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