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: 931

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.  

Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy,) and brought to you in partnership with Home Energy magazine.

Latest Activity

Hal Skinner commented on Hal Skinner's group The RCC Classroom (Radiant Control Coatings)
"Kurt, check your emails.  Sent you a friend request you need to confirm then I can send you a…"
4 hours ago
Kevin Jordan replied to Kevin Jordan's discussion Does anyone have pointers on approaching real estate induatry.
"thank you sir!! If you have any other tips Id appreciate. I am new in this industry and I go and…"
5 hours ago
Bud Poll replied to Kurt Shafer's discussion Where can I find the best radiant barrier to install under my roof?
"Hi Kurt, You mentioned "On a RESNET discussion some insulation experts agreed that insulation…"
6 hours ago
Kurt Shafer commented on Hal Skinner's group The RCC Classroom (Radiant Control Coatings)
"Wow, I am very sad to hear about your eyes.  Would have been super to do that comparison. Good…"
6 hours ago
Hal Skinner commented on Hal Skinner's group The RCC Classroom (Radiant Control Coatings)
"My dads house has an attached garage.  It was converted to living space around 20 years…"
6 hours ago
Kurt Shafer commented on Hal Skinner's group The RCC Classroom (Radiant Control Coatings)
"Hal, do I see a terrific chance for you to show us all the power of your RCC? Your father's…"
7 hours ago
Hal Skinner replied to Kevin Jordan's discussion Does anyone have pointers on approaching real estate induatry.
"Kevin, Several years ago I worked closely with a general contractor and a real estate…"
7 hours ago
Hal Skinner commented on Hal Skinner's group The RCC Classroom (Radiant Control Coatings)
"That same RCC, used as paint on the ceiling of living space, will do the same as if it was applied…"
8 hours ago

© 2014   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service