Comments on: Go Up, Go Small, and Get Those Ducts Inside Conditioned Space

By: David Butler

David Butler — Fri, 05 Jun 2015 22:24:34 +0000

@John, either strategy is a
@John, either strategy is a good way to have ducts inside the envelope. However, you need to make sure the upper ceiling is air tight.

By: Curtis Johnson

Curtis Johnson — Fri, 05 Jun 2015 20:02:52 +0000

John:

John:

I think framing down the entire ceiling might be a bit much but without knowing what your floor plan looks like, I could be wrong. As a designer, I try to take the minimalist approach and look for parts (ceilings)of the room layouts, such as hallways, and use them for placement of ducting inside the condtioned area. Of course all this needs to be worked out with your HVAC designer.

Lately many of my designs have been for radiant floor heating in tight ICF homes, so I am mostly dealing with trying to find where the HRV/ERV ducting can be installed.

For Eastern Canada, I hope you have a good handle on providing a good thermal break for your slab edges as well as planning to install continuous insulation under your slab. Thermal energy loves to find cold/cooler places to migrate to, so you definitely don't need to be warming up the soil under/around your home at the expense of operating your heating system more than you need to.

Just my 2 cents worth. Good luck.

By: John

John — Fri, 05 Jun 2015 14:28:13 +0000

Not sure if this blog is
Not sure if this blog is still active but here goes. I live in Eastern Canada so outside cold is my concern. I am building a 2000 sq ft one story on slab. I was thinking of building with 9' ceilings and installing duct work and plumbing in a tray ceiling or build with a 10' ceiling and dropping the entire ceiling 1'.
Would either of these methods be practical?

By: David Butler

David Butler — Mon, 03 Feb 2014 13:14:55 +0000

@Richard:
@Richard: moving ducts in an existing house is rarely cost effective. Better to make sure ducts are tight and well insulated, seal the ceiling, etc.

BTW, in tight homes built to current code, there's no rationale for locating diffusers at perimeter. Returns just need to be strategically located to ensure no feedback.

Buidding America will conduct a free webinar on March 20: Ducts in Conditioned Space (includes deeply buried encapsulated ducts) GoToMeeting.

By: Richard

Richard — Fri, 31 Jan 2014 11:47:49 +0000

Nice post Allison
Nice post Allison

I have been studying various construction technicians to lower the power consumption in a new residential home for me and my wife in the Atlanta GA area. I have looked into moving HVAC ducts into the conditioned space. But it seem to be a rather expensive move to make for a one story home. Not doubt every problem has a solution and normally comes with new problems.

The illustration showing registers located in the center of rooms would make for uneven temperatures throughout the rooms. Registers should be located against exterior walls or furthest point from room opening/return.

@ Clayton D
Thanks for the link on the Buried and Encapsulated Ducts. I read the entire 89 page test report, and believe this one of the most economical solution I have found yet to get within a razors edge of the efficiency of Ducts in a conditions space.

Using Deeply Buried Encapsulated Ducts

ccSPF Duct Spray Foam ($1.89/ft2) (Stated in Report)

Thermaflex 8" Flex Duct (R-8.0 = 2 1/4")
Cost to Spray Duct about $6.18 Lf

Would love to hear more opinions from others on Buried and Encapsulated Ducts.

By: Eric Kjelshus

Eric Kjelshus — Tue, 14 Jan 2014 23:34:38 +0000

I try to all flex under 5'
I try to all flex under 5' long with the rev bulkhead I can do that. I do find the grills you pick must be the higher end not just the stamped grill so the draft does not dump down your back.

By: T.C. Feick

T.C. Feick — Wed, 08 Jan 2014 01:30:33 +0000

Allison, this works well. I
Allison, this works well. I recently built a small in-law apartment behind my house. I spent a lot of time thinking about my duct work and air handler location, so I have no duct run over 20 feet, and all of my duct work was installed in a tray recess designed into the bottom chord of the roof truss. We drywalled the space then hung the ductwork, then installed my ceiling below, as Curtis suggested in an earlier post. This is not a super popular installation to pitch to an unsympathetic HVAC contractor, but it is easily doable. Another approach I've seen is to drop the ceiling in the second floor hallway, and use that as the duct space. With the popularity of 9' ceilings, an 8' hallway works fine.

By: David Eakin

David Eakin — Tue, 07 Jan 2014 23:01:32 +0000

Allison,

Allison,
Recently visited our daughter in Florida; she has a slab-on-grade, single-story, no basement home similar to the one illustrated (except built sometime in the ’50s). The biggest issue I see with this modified raised-heel truss is the difficulty of maintaining integrity when future modifications are needed (and there will be future modifications – there have been many in my daughter’s house over the decades). I would also think that the additional costs for the specialized trusses, additional labor/materials in sealing/insulating the reverse bulkhead, and additional drywall labor would far exceed the cost of spray foam on the roof underside – especially considering the low roof slopes typically found in non-snow load regions (less square feet). Plus recent insurance analysis of hurricane and tropical storm damage now leads to recommendations for non-vented attic spaces in storm-prone areas.

By: David Butler

David Butler — Mon, 06 Jan 2014 23:22:28 +0000

@Barry, ASHRAE Standard 193P
@Barry, ASHRAE Standard 193P defines a test procedure for cabinet leakage (2% at 1"WC). California and possibly other states now require this for all air handlers so all the majors now offer AHU's that meet this. You just need to know what to look for in the specs.

By: David Butler

David Butler — Mon, 06 Jan 2014 23:16:17 +0000

Regarding access to balancing
Regarding access to balancing dampers... you have the same issue when HVAC is installed in floor system between two levels or in drop soffits.

Mark's point regarding damper access is spot on. In homes with finished basements, I try to steer towards a drop ceiling. Attractive ceiling tiles are available. Makes life easier for future electrical, low voltage and plumbing changes as well.

@A Hyde, the requirement to support ducts over the insulation is appropriate. But I'm not sure why you think it would apply in this case.