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I-Joists, Fiberglass Batts, Joist Trak and Energy Star Checklist

I'm about to break ground on a 1.5 story, 2100 sf Cape Cod house on Cape Cod (lots of knee-walls). The first floor is to be heated with Wirsbo Joist Trak. Also, the large room over the garage will have an insulated floor to allow for future conditioned space(mini-split). The house will use 11 7/8 I-Joists exclusively due to the open concept design and all floor surfaces above I-Joists will be glue and screw 3/4 plywood. My building code requires I use/meet the energy star checklist.

Now for the tough stuff; my wife insisted I sell my motorcycle, use a 4 point harness when I paint my 2-decker, and spray in (foam) won't be used (substantially) in the house.

My questions are/quandary is:

1. How to achieve Energy Star compliance for sub-floor insulation contact when a small air gap for extruded heat transfer plates promotes even floor surface heat? (current design call for R-30 9 1/2" un-faced fiberglass batts with rim plates insulated under the 1st floor)

2. How to achieve sub-floor insulation contact compliance while using 12" R-38 un-faced fiberglass batts in the garage/under knee wall ceilings; can an insulation installer get sufficient fit with 15" or 16" x 12" in the plenum formed by 11 7/8 I-Joists 16" on center for a 25' x 35' ceiling?

I'm afraid there was some misunderstanding with the HERS rater plan review during the permitting stage; he figured I would change the design during the build phase.

Oh, and increased cost is an issue...Does anyone have a winning lottery ticket they want to sell cheap?

Asked by A Guy
Posted Aug 13, 2014 10:01 PM ET
Edited Aug 13, 2014 10:19 PM ET


2 Answers

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Advice; Stop the project till the entire plan is ready, priced, on a schedule, with subs signed.

Joe L, says insulation does NOT need to contact floor sheathing.

Sell the motorcycle, cost benefit verses divorce.

Answered by aj builder, Upstate NY Zone 6a
Posted Aug 13, 2014 11:26 PM ET


I am a Uponor certified designer / installer and have been for a very long time . The only underfloor heating application that requires an air layer is suspended tube (horrible) , PERIOD . If someone is telling you otherwise , fire them and seek qualified assistance . Uponor joist trak fastens directly to the subfloor (no gaps) and the even heat is achieved from that direct contact taking spacing , water temp , room ambient temp and all things into consideration . Insulation should be a minimum of R19 and should be right up to the sub floor . Although I am a Uponor recognized designer / installer I only use joist trak for retrofit or the occasional area where floor height is an issue . As for your knee walls , why don't you utilize them as radiant wall heat instead of the floor , heat does not rise ! Plus when your wife wants to place a wooly mammoth on the floor the heat emitter won't be compromised .


In most new homes , again depending on design and preference . Where responsiveness and efficiency are of the utmost importance I use this product , have a look .


In case you wonder about my qualifications you can check the "find an installer " section of Uponor North American site , my zip code is 08755 and find me at my Bluewater Mechanical space and I also design and install for Langans Plumbing and Heating , we are the real deal .


Don't sell your scooter my friend , it does not talk back and always understands you . Putt away .

Answered by Richard McGrath
Posted Aug 14, 2014 7:04 AM ET
Edited Aug 14, 2014 7:10 AM ET.

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