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: 998

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

Steven Lewis replied to William Fisher's discussion Can tankless water heaters provide hot water even when the groundwater is fairly cold?
"Look at reducing the ambient humidity in the home.  The dew point is the key to the…"
13 hours ago
Olivia Taylor posted blog posts
23 hours ago
norman farwell replied to Bryan Pringle's discussion Dense packed cellulose in basement?
"Ha, we're on the same wavelength.  That's the big question--I'm still thinking…"
yesterday
Bryan Pringle replied to Bryan Pringle's discussion Dense packed cellulose in basement?
"Thanks Norm, we'll have a couple of case studies when all is said and done. Just curious, do…"
yesterday
norman farwell replied to Bryan Pringle's discussion Dense packed cellulose in basement?
"Bryan,  I am trying the same thing for most of the same reasons and also against advice to the…"
yesterday
Morgan M Audetat commented on Sean McLoughlin's blog post Programming in-floor electric radiant heat, is it worth it?
"You would need a large bathroom to see the difference. We install them both ways depending on the…"
yesterday
Dennis Heidner commented on Sean McLoughlin's blog post Programming in-floor electric radiant heat, is it worth it?
"The key is that this is the bathroom.  Occupancy is not constant.  It is more likely used…"
yesterday
Charles Cormany commented on Sean McLoughlin's blog post Programming in-floor electric radiant heat, is it worth it?
"I have seen resistance floor heaters add nearly $100 per month to an electric bill. Since most…"
yesterday

© 2015   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service