Spot the Design Weakness - For Northern Climates

If we had a dime for each weak building assembly detail we saw, we’d be rich. In our 14 years of diagnosing comfort problems for clients; the exposed floor ranks as one of the most stark discomfort features of a home, new or old.

Walking home from the coffee shop Sunday and came across the feature below. Have a look at the photo and see how many design errors you can pick out:

Exposed floor with duct

1- The 2nd floor cavity is exposed above the front door.

2- The metal duct travels in a floor joist cavity past eh stone veneer covering a steel beam.

3- There are pot lights in the eaves.

Even 2LBS spray foam won’t ward off the discomfort in this small but significant exposed floor. How can it, the poor design will handicap it and soon enough all will be covered with lovely aluminum perforated soffit and who will know better.

So here’s the blow by blow, spray foam doesn’t stick well to oiled metal, there’s not enough room between the bottom of the duct and future soffit and though code does allow R12 they won’t get 2″ on the bottom. The duct will lose flow and warmth as it passes so close to the outdoors only to come back in. It runs close and may even touch 2 uninsulated metal beams. Lastly, let’s keep our finger’s crossed that the open joist cavity above the stone wall is continuously sealed otherwise that whole floor cavity above the entire foyer will feel cold to the touch on both sides (main floor and second).

As for the pot lights in the eaves, they are hard to change when they burn out and often create too much heat enough at times to create and ice dam.

Views: 1229

Comment

You need to be a member of Home Energy Pros to add comments!

Join Home Energy Pros

Comment by tedkidd on October 25, 2013 at 11:24am

Nice post Greg! 

Mind if I add to your list?  

4 - furnace will be oversized, so cycle times will be short thereby insuring that in heating season this duct will deliver cold air to a cold room. (You don't deliver hot air through cold duct.)

There is only so much you can do when multiple design flaws occur.  Often correcting for a few means the penalty due to the unsolvable (overhang) becomes insignificant.  I'd move the supply in as far as possible and use closed cell spray foam to this whole area.  

Videos

  • Add Videos
  • View All

Twitter

Latest Activity

Tom White's video was featured

Residential Energy+ - Rocky Mountain Institute from James Brown Media on Vimeo.

Residential Energy+ Rocky Mountain Institute

Residential Energy+ is a Rocky Mountain Institute (RMI) initiative enabling industry actors to capture the $150 billion residential energy upgrades market opportunity, and meet the top unmet demand among homeowners: improved home energy performance.
32 minutes ago
Tom White posted a video
15 hours ago
Chris Stratton liked Kim Tanner's discussion Game of Homes
15 hours ago
Amber Vignieri posted a blog post
23 hours ago
ofer ben -nathan added a discussion to the group HVAC
yesterday
ofer ben -nathan joined Allison A. Bailes III's group
Thumbnail

HVAC

HVAC design, Manuals J, S, T, & D, Duct leakage, Air flow, ENERGY STAR new home requirements,…See More
yesterday
Mary Knox replied to Kim Tanner's discussion Game of Homes
"Sounds interesting. I will definitely try it."
yesterday
Judy Roberson joined Norm Bourassa's group
Thumbnail

Multifamily Buildings

For too long there has been relatively little EE focus on multifamily, but some new programs have…See More
yesterday

© 2016   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service