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: 958

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

Shashank Kirloskar posted a blog post

Important Facts about Solar Energy

“I’d put my money on the sun and solar energy. What a source of power! I hope we don’t have to wait…See More
5 hours ago
reflintorm replied to Dennis McCarthy's discussion Solid state lighting - saves lives- and it improves life .
"In my observation, In most of the lightning appliances led bulbs are used because of their…"
6 hours ago
Chad Mcaulife posted photos
14 hours ago
Bob Blanchette commented on Jeremy Begley's blog post The Home Envelope : Does it Really Matter in a Heat Loss Calculation
"Infiltration makes a HUGE difference. Look at the heat loads on a windy day vs. a calm one. On a…"
14 hours ago
Bob Blanchette commented on Everblue's blog post Poor HVAC Installation Leads to Increased Energy Use
"That explains a LOT of why HVAC system continue to be sized by the same "rule of thumb"…"
14 hours ago
Profile IconChristian Asdal and Shashank Kirloskar joined Home Energy Pros
15 hours ago
Don Fitchett shared their video on Digg
15 hours ago
Don Fitchett shared their video on StumbleUpon
15 hours ago

© 2014   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service