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High velocity a/c

Old 07-13-2019, 12:22 PM
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Default High velocity a/c

Our current a/c system is ducted through the attic which of course seems just idiotic because the ducts have to run through such a high temp area before itís vented through the ceiling and into the living area. Itís working fine but nothing lasts forever. Iím thinking of a high velocity system and the ducts would be in the basement where itís much cooler, then entering the living area through the floor via 2Ē ducts and small round registers. Any advise?
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Old 07-13-2019, 12:58 PM
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Are your ducts insulated?
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Old 07-13-2019, 01:00 PM
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Originally Posted by Gullpt View Post
Our current a/c system is ducted through the attic which of course seems just idiotic because the ducts have to run through such a high temp area before itís vented through the ceiling and into the living area. Itís working fine but nothing lasts forever. Iím thinking of a high velocity system and the ducts would be in the basement where itís much cooler, then entering the living area through the floor via 2Ē ducts and small round registers. Any advise?
Your thinking is tortured. Air flow is air flow regardless of the run. High velocity is used in really 2 applications - 1) when duct size is an issue ; 2) customers want low profile registers.

Other than low profile registers, what are you hoping to gain?

Of course we also need to talk price (may or may not matter to you) so this is secondary. A high velocity (spacepak or unico - $$$$$) will be significantly higher in cost.

You appear to be of a misconception that duct through the hot attic (very common) is worse than duct through the basement (also common).
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Old 07-13-2019, 01:05 PM
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If your attic is too hot, get some ventilation up there.
let some of that hot air get out so the cooler outside air can get in
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Old 07-13-2019, 01:34 PM
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Seems to me that if you want to get the same amount of air through a small 2 inch vent that it would make some serious noise. At least an annoying noise if nothing else. I bet my attic is 115 right now. Not worried as the air is cold coming out of the vent.
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Old 07-13-2019, 01:42 PM
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Floor registers suck if that is what you are thinking. I have had both and prefer the ceiling even if its in a hot attic. Floor registers always tend to be in the worst spots where somethig is blocking ariflow.
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Old 07-13-2019, 01:46 PM
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Originally Posted by ole_blue View Post
Seems to me that if you want to get the same amount of air through a small 2 inch vent that it would make some serious noise. At least an annoying noise if nothing else. I bet my attic is 115 right now. Not worried as the air is cold coming out of the vent.
nope
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Old 07-13-2019, 01:51 PM
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No more noise than conventional system. It just makes sense to me that running ducting through a cool space makes far more sense than running nearly 100’ of duct through a100 plus degree attic.
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Old 07-13-2019, 01:52 PM
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No matter what you do, you really should have all distribution insulated.
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Old 07-13-2019, 01:58 PM
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Originally Posted by waybomb View Post
No matter what you do, you really should have all distribution insulated.
AND the returns. Common problem with attic systems.
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Old 07-13-2019, 02:11 PM
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If you vent a/c in the floor the specific gravity will cause the cold air to stratify and just run in a boundary layer across the floor into the return vent, it's vented in a corner of the room ceiling so it will mix with the room air while it makes it's way across the room to the return vent. Much more comfortable.
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Old 07-13-2019, 02:13 PM
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Originally Posted by Gullpt View Post
No more noise than conventional system. It just makes sense to me that running ducting through a cool space makes far more sense than running nearly 100í of duct through a100 plus degree attic.
not if the duct is insulated properly. To answer your question though - I have run high velocity without a whisper (figure of speech). All depends on application and budget of course.

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Old 07-13-2019, 02:19 PM
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Originally Posted by billinstuart View Post
AND the returns. Common problem with attic systems.
no question supply and return duct to be well insulated.
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Old 07-13-2019, 04:16 PM
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whats needed? R8?
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Old 07-13-2019, 04:43 PM
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Originally Posted by edwardh1 View Post
whats needed? R8?
The ideal set-up is all ductwork is in "conditioned spaces"..below the ceiling insulation. A/C works best when the registers are ceiling or upper wall mounted. The great debate..do you place the vents around the outside walls, or do you blow the a/c towards the outside walls.
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Old 07-13-2019, 05:50 PM
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You, like most of us, simply need quality installed, properly insulated sheet metal ducts.... in the attic. I’ll never understand how the current standard flex duct crap was ever even approved. But it’s what most of the country lives with. If ducting is properly insulated and the attic is properly ventilated, there won’t be much difference of where it’s mounted.
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Old 07-13-2019, 07:26 PM
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Spray foam your attic and call it a day.
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Old 07-14-2019, 06:15 AM
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Originally Posted by Tireless View Post
Spray foam your attic and call it a day.
I'm just not comfortable with the long term effects of Isconyne..isoc..foam insulation on attic roof decking. I'm still in the "ventilate the attic" camp.
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Old 07-14-2019, 07:42 AM
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Originally Posted by billinstuart View Post
I'm just not comfortable with the long term effects of Isconyne..isoc..foam insulation on attic roof decking. I'm still in the "ventilate the attic" camp.
Well, I've had both and I will have foam from now on. No hesitation.
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Old 07-14-2019, 08:33 AM
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Originally Posted by Gullpt View Post
No more noise than conventional system. It just makes sense to me that running ducting through a cool space makes far more sense than running nearly 100í of duct through a100 plus degree attic.
Not sure what type of system you are considering but I have a Unico and I can assure you that it is much louder than conventional.
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