Good article. It definitely makes a difference having well sealed and, where needed, insulated duct-work. My gas bills this past winter will attest to that.
Good read Nick. We done just that when I use to work with Cundiff-Heating and Air.
Building cavities are no longer allowed for any portion of the ducting(returns included) in Illinois since the adoption of the IECC.
This condition is also responsible for high Radon levels, mold distributed throughout the house, inability to control moisture, dirty ducts that become allergy issues etc…
The article fails to make enough of a distinction between inside and outside the building envelope. All supply and returns that are located outside the building envelope need to be treated as per the article’s recommendations, however, if the ducts are entirely inside the building envelope, it does not matter.
This may be a US vs Canada issue, or a northern construction vs southern issue. Homes built in Alberta do not have crawlspaces or supply ducts in the attic. Basements are entirely inside the building envelope (heated in other words), and they are insulated if they are new construction.
Air leakage is not an issue if occurs inside the building envelope, it may even help in drying out and ventilating enclosed building materials within the building envelope, such as a chase surrounding air ducts in a finished basement, and ensuring that a consistent temperature is maintained throughout the building envelope. The same goes for using joist or wall cavity space for return air.
The article should include some words that make the distinction of what is inside or outside the building envelope, and what should be insulated what does not need to be insulated.
I came across 2 older homes last month that use the interior wall cavity for supply to registers.
I never feel they can be cleaned properly-stuff sticks.
We added some new photos to the article today: http://www.nachi.org/building-cavities-supply-return-ducts.htm
Yes you did. I copy and pasted this last night in my library for future use. Well the future has passed, I used it in my report today and then see it posted here now. Talk about timing. Thanks Nick