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Comfortboard vs rigid foam insulation

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Posted by: from Vaughan
2/6/2017 at 10:28:38 AM

I am looking to finish my basement and question about insulation. Is there a difference between using Roxul comfortboard vs 2" rigid foam insulation between the concrete wall and the studs?

Seems to me that the foam insulation would be the better way to go as you don't have to worry about vapour barrier and tyvek wrap on the concrete wall. I priced out material cost and its roughly the same cost and both have the same r value.

Second question, when installing a subfloor like dricore or DMX 1-step, would you butt it up against the comfortboard/foam or would you take it straight to the foundation wall?

REPLIES (6)
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Date/Time2/6/2017 at 11:22:18 AM

Foam board does NOT provide a vapour barrier recognized by Canadian Building Code. Both products do not reguire Tyvek be water moisture is not absorbed. and are midew mould free. #1 Tyvek lettering facing concrete #2 Comfort Board. To floor with Tyvek coming into the interior 3-6 Inches. Then subfloor. Water never enters Living space and travels under subfloor. Foamboard to floor subfloor up to it. Frame in front of both.

Cheers,

BMUSCOTTY

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John in Vaughan
Date/Time2/6/2017 at 11:53:12 AM

Thanks for response but this where I got confused. See section 6.2.1, it doesn't mention anything about vapour barrier where double batt insulation does.

http://www.nrcan.gc.ca/energy/efficiency/housing/home-improvements/keeping-the-heat-in/basement-insulation/15639

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Date/Time2/6/2017 at 5:41:20 PM

I have done several basement renovations and prefer roxul with a 6ml vapour barrier. Seal the seams with tuck tape and do whatever covering you have in mind. (drywall, paneling, t&g, etc.) As to the flooring, I would go to the concrete foundation (wall) and build any interior wall on top of the new subfloor.

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Date/Time2/6/2017 at 7:07:06 PM

Hi John,

My company always finishes basements in the following manner. We glue 2" ridged foam to the concrete walls and then seal every edge with Tuck tape. We take the foam from the base of the floor joists to the concrete floor. We then Frame all our walls with blue board plates with barrier paper between the board and the concrete. We always leave about an inch between the framed walls and the ridged foam. As we sit the boards down we put a glob of techni-seal on the bottom every spot we are going to install a ramset nail. After the framing is finished we then install roxul in the framed walls. This gives you extremely good insulation. Now those areas between the floor joists against the outside wall...roxul and plastic vapor barrier. Use tuck tape an all the edges. The dricore we always install is to the edge of the framed walls. On the inside. Leave a quarter inch for expansion and contraction. In any area of the basement that is not going to have a framed wall, take the dricor up to the ridged foam insulation.

Hope this helps,

James Fram

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John in Vaughan
Date/Time2/6/2017 at 7:39:23 PM

Thanks James,

That's exactly what I was planning on doing as it seems the simplest method wth one exception. In between the floor just I was planning on using 1 inch depth spray foam then back fill with roxul to five me an r20. Saves time and my sanity from having to do all that taping.

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Date/Time2/6/2017 at 8:13:07 PM

Hi again John,

The reason we don't fill the tiny gap at the base of the foam board where it meets the floor is the future possibility of a crack in the foundation and leak.If you ever experience a leak you want the water to run under the dricore towards the drain. Now that is a major leak. But even a small one fron a crack will have the opportunity to dry out in the airspaces under the dricore.

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