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.

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Comment by R Higgins on October 30, 2013 at 7:03pm

Won't matter how energy efficent or not a house is, if water proofing and condensation isn't the first priority. 

Bigger problem for the entire building is the stucco finish. In a Northern (freeze / thaw) they crack, and it seems most folk don't think you need to maintain stucco even as much as wood siding, like painting to seal the hairline cracks before they become big cracks.  Stucco chock full of synthetic ad mix can act as a pretty good vapor barrier and condensing surface too.  Of course, what I'm looking at is probably the facing of a EFIS system in which case all I can say is ekkkkk!

As an architect, I'll question the overhang, dormers and 2nd fl soffit cans.  I like boxes suspended in space as much as the next guy, but the fringe of roof and soffit just cries out for a couple of posts, which could be glazed between, and you have a vestibule, maybe even a sun room that could be a net heat generator, and mitigate coldness of the overhang.  Dormers, I'm betting not another floor, but part of cathedral ceiling, and the cave man in me loves that the living in a cavern feeling, but, indefensible energy wise.  The 2nd fl cans are just lame, as pointed out.  Though, I've seen such for those who had "security" problems, which as sad as that might be, could justify the cans (and luckily these clients could always afford to hire folk to replace the bulbs).

Comment by tedkidd on October 29, 2013 at 9:24pm

LOL.  How did I have the nerve to turn off one of these gas valves?  

Greg, sometimes you just have to take some chances...  The house is literally 1.3 blocks away from my house, so the risk was pretty small.  

This summer I pulled the disconnect on one of the AC units.  That risk is bigger as the thing is on the garage roof...

Comment by tedkidd on October 29, 2013 at 8:27pm

The value of collaborative overlap.  

Comment by Greg Labbe on October 29, 2013 at 8:25pm


I agree, we typically collaborate with Architects and Design-Build contractors to 'head these off at the pass.'

If you asked me to design a house, I could. I could also build it. It'd be super efficient and super comfortable but it would look like an old Volvo.

That's why we need architects, they know how to design and use space elegantly; a skill I don't have. But I do know building envelope weakness and that's where boots on the ground can help the designer if they don't have the experience of fixing and witnessing countless failures. 

Its so much cheaper to fix things with an eraser than a hammer!

Comment by tedkidd on October 25, 2013 at 8:36pm

Pardon, NOT 70k, likely 50-60k output according to my friends Jim Davis and Dave Richardson at NCI

Comment by tedkidd on October 25, 2013 at 8:34pm

LOL.  Talking about oversized...

This house, 2200 to 2400 sf PER FLOOR over 4 floors,

Circa 1920, some 8000 cfm50 leakage, has these twinned 80,000 btu low efficiency furnaces heating it:  

Last winter I did this to one of the gas valves: 

And the homeowner reported an immediate and noticeable improvement in comfort, both evenness and balance. 

One week after single digit temps every night I had to turn the other furnace on for a few days because the house slid back.  I think this may have been due to Time Warner's crappy thermostat which seems to have a mind of it's own.  Had the temp been left constant, the 70k output may have been sufficient to carry this HUGE house.  

When I've aggressively sized below Manual J in the past, surprising energy savings have been another positive result:

You guys keep egging me on, I'll keep providing pics...

Comment by Greg Labbe on October 25, 2013 at 8:20pm

Ice cubes! That's some nice filtering going on up there. As for the furnace, it should be oversized because the house is so leaky ;-).

Comment by Jim Gunshinan on October 25, 2013 at 7:02pm


Comment by tedkidd on October 25, 2013 at 6:45pm

Jim, 95% of overhangs you see lead straight into the home.  My brother could freeze icetrays on his kids floors until he addressed it.  My mother and every one of the identical $250k condo's in her neighborhood all have garage attics connected to the second floor - no box band: 

more fun stuff from my BAD picture album:

Comment by Jim Gunshinan on October 25, 2013 at 6:11pm

Nice catch Greg. It seems too bad to be true, but it's true.

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