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Adding additional ducting, why not got through existing walls?

Posted by kitty_may (My Page) on
Sun, May 29, 11 at 13:02

Every time I read about someone who needs additional ducting the suggestion on the list is to go through an existing wall. Why is that?

My second floor master bedroom is woefully under-cooled and I can't help but think adding a supply would help. I know that my system would need to be recalculated for the load and that it also needs more returns. But why not look into going through the existing exterior walls for a few additional return? Dry wall repairs aren't fun but they aren't horribly expensive either. None of the HVAC professionals who've looked at our system have mentioned the possibility.

What am I missing that makes cutting out part of your wall to fix a major A/C issue the last thing on the list to try?


Follow-Up Postings:

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RE: Adding additional ducting, why not got through existing walls

sorry, meant to say,
"the suggestion on the list is *never to go through an existing wall."


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RE: Adding additional ducting, why not got through existing walls

Exterior walls are full of insulation.

Interior walls can have wiring and fire-blocks.


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RE: Adding additional ducting, why not got through existing walls

But what if I'm in a 1940's brick home with no insulation to speak of?

We're looking into tightening up our house to make it more energy efficient, but no matter how energy efficient we make it I don't think it will make up for the fact the ducting was built for heat only and our large master bedroom has only one supply.

The process is all kind of all woven together for us.


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RE: Adding additional ducting, why not got through existing walls

Well - how about ducting doesn't usually run through walls? Conventional ducting is way too big to fit in a wall. Anything new would have to be insulated and there just isn't room in a wall for duct + insulation.

Soffits are big enough. An attic is big enough. A crawlspace is big enough. Do you have an attic? If not - build a soffit.


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RE: Adding additional ducting, why not got through existing walls

We do have an attic. It's the primary space we're wanting to tighten up along with the basement. I think that means we'd have to put the A/C and our second air handler in up there? What we have now is in the basement. Our current AC system is over 12 years old so we're thinking of replacing it. The energy audit person mentioned that as probably the best option, but I'm having issues with getting referrals or an HVAC company to show up.

Due to how small our house is and the design soffits aren't really a good option.

Thanks for explaining it to me. I appreciate it! Our old ducting runs through exterior walls, but it clearly is not adequate for the second floor. Adding more of what doesn't work to make something work is probably not the best answer.


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RE: Adding additional ducting, why not got through existing walls

Put the new air handler in the attic.

There are a couple options for ducts.

Duct-board works well since it has a lower mass than metal ducts and built in insulation.

Enclosing the air handler and some (or all) the attic ducts in insulated space that then is treated as 'semi'-conditioned also works.
You move the insulation from the floor of the attic to walls and a ceiling around the air handler (and as much of the ducts as you care to enclose.


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