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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 9:01 PM ET
Edited Aug 13, 2014 9:19 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 wjrobinson
Posted Aug 13, 2014 10:26 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 Rich Mc
Posted Aug 14, 2014 6:04 AM ET
Edited Aug 14, 2014 6:10 AM ET.

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