# Basement insulation and DRIcore



## mrtn (Sep 6, 2012)

Hello everyone,

I am new to this forum but have been reading it constantly for information on finishing my basement. 

I have decided to put rigid foam on the concrete walls with DRIcore floors. It is easier for me and recommended by the manufacturer to build the walls on top of the DRIcore. I will the insulate between the studs with fiberglass insulation. My question is does this defeat the purpose of blocking the walls with rigid foam? You need a 1/4" gap between the walls and DRIcore. Does it matter the the gap for air flow will be behind the walls? The cold air from the concrete would come out and mix with the warm air of the room. I made a pic to try and describe what I'm talking about. Does this matter? I'm thinking it's the same scenario either way you do it. 

I realize I spelt basement wrong in the subject, sorry I don't think I can edit it now. If this is in the wrong section for this topic I apologize, this is my first post.


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## notmrjohn (Aug 20, 2012)

You need unfaced insulation between the suds, it will stop cold air from floor.The foam on walls is a vapor barrier. An empty air space between wall foam and back of insulation.Install the floor way manufacturer says, almost to the foam. You don't want to trap moisture under the floor. "I made a pic to try and describe what I'm talking about. Does this matter?" Does it ever! Half the responses to questions are "Do you have a picture or drawing?" I know. That's not what you meant. Excellent first post, when you make more, you'll get used to me, or have found the ignore button.


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## mrtn (Sep 6, 2012)

Lol thank you, very helpful! Every time I visit this site I get a little more confident on how to get this project started.


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## Gary in WA (Mar 11, 2009)

"I have decided to put rigid foam on the concrete walls with DRIcore floors. It is easier for me and recommended by the manufacturer to build the walls on top of the DRIcore. I will the insulate between the studs with fiberglass insulation."-----

Fiberglass insulation is very air permeable (goes right through it), hence the reason why furnace filters are made from it. 

"My question is does this defeat the purpose of blocking the walls with rigid foam?"----

Yes, if air from the room/under floor gets to the concrete wall, your air barrier (foam board) is compromised.

"You need a 1/4" gap between the walls and DRIcore."---

DriCore falls short here, no air gap to room/wall cavity; Fig.#3: http://www.buildingscience.com/documents/insights/bsi-003-concrete-floor-problems?full_view=1

Delta FL has it together, read paragraph #8 (air gap at perimeter); http://www.cosella-dorken.com/bvf-ca-en/products/foundation_residential/floor/products/fl.php

"Does it matter the the gap for air flow will be behind the walls? The cold air from the concrete would come out and mix with the warm air of the room. I made a pic to try and describe what I'm talking about. Does this matter? I'm thinking it's the same scenario either way you do it"----

Imperative that *no room air *gets to the concrete; page #11- middle paragraph; http://www.buildingscience.com/documents/reports/rr-0202-basement-insulation-systems

Why bring extra moist air from the slab to the wall cavity to rot the wood framing and mold the drywall backing paper?

Here is a current similar thread: http://www.diychatroom.com/f15/finishing-basement-advice-needed-156026/

Gary


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## mrtn (Sep 6, 2012)

Thank you. This is the problem with this sort of thing.everyone seems to have a different opinion on how to do things and once again I'm unsure how to do it. I went looking for Delta-fl and was told that it was taken out of production. Don't know why. 

It is my understanding that the air gap is necessary to keep air flow so water does not form. I don't have water issues in my basement at all, but wanted to be safe. There will be no gap in the foam on the wall, but the gaps on the floor, as in my diagram from the first post. 










dricore even says to cut vents at the perimeter walls to increase airflow. It seems that delta-Fl and DRIcore have opposite ways of thinking and this causes confusion. However DRIcore has been out for a while and continues to be used, delta fl is no longer available... Is it a matter of lack of consumer knowledge and marketing dynamics, or is it infact an inferior product. I see all the home improvement shows using DRIcore but that could just be a case of paying for product placement?


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## AtlanticWBConst. (May 12, 2006)

mrtn said:


> .....I went looking for Delta-fl and was told that it was taken out of production. Don't know why.....


Found this link: http://www.cosella-dorken.com/bvf-ca-en/contact/distributors_usa.php?id=NY

FWIW - I just don't trust verbally passed-on information, as it is generally not very reliable. 
I prefer to contact manufacturers directly, especially when it comes to gathering accurate technical information & material data.


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## mrtn (Sep 6, 2012)

Thanks, I just took the guys word as I cannot find it at any store listed. I asked at lowes and they are the ones who told me that it was discontinued. I also live in Canada if that helps. Maybe just discontinued here. I'll contact them to get a final word.


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## mae-ling (Dec 9, 2011)

Excellent drawing!!!!!! Thanks.

Why not do it the second way?


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## mrtn (Sep 6, 2012)

Because it is recommended by the manufacturer and will eliminate the issue of the wood contacting concrete and code here says no pt wood in the house, not that I want it anyway due to the chemicals.


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## Gary in WA (Mar 11, 2009)

Just add a foam board bottom plate under the wood one, 1/4" higher than the Dricore, canned-foam seal it to wall f.b. and Dricore. Or just forget the Dricore and use rigid foam board under plywood and/or wood sleepers.

The dimpled material creates an air space which matches the moisture drive pressure of the concrete slab. The air space should not be allowed to exchange moisture with the room air. In the diagram Fig. 3, notice words like; Dimpled sheet membrane- air tight and gas tight, and below= Vapor pressure equalization--- and - airspace pressure tracks the vapor pressure of the slab---- *not* if the perimeter is able to relieve the moisture/pressure to the room air, and vice/verse when the HVAC kicks in, increasing the RH there, by tenfold or more. http://www.buildingscience.com/documents/insights/bsi-003-concrete-floor-problems?full_view=1

Think of foamboard on a wall (main purpose is an air barrier), only now its on the side= slab. No air transfer from slab to room, no transfer from room to slab, this is basic building science; eg.; computer pp.2, #3; http://www.buildingscience.com/documents/reports/rr-0309-renovating-your-basment

If air gets behind the foamboard from the basement, the RH will copy exactly; you want to keep all basement air from the concrete, *Wall#3*, page9-14 here, XPS did well; http://www.eceee.org/conference_proc..._1/p1_27/paper

Or just forget the Dricore and use rigid foam board under plywood and/or wood sleepers. I'd rather not have an engineered wood in a basement that could have water leaks from mechanicals (washer, plumbing lines, etc.).

Gary


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## mrtn (Sep 6, 2012)

What if I just forgot DRIcore and just put laminate down? With the foam underpad? 3 contractors I spoke to recommended doing that...


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## Gary in WA (Mar 11, 2009)

http://www.avsforum.com/avs-vb/archive/index.php/t-676110.html Both pages...

Do you know if there is a plastic vapor barrier under the slab; http://www.buildingscience.com/documents/insights/bsi-059-slab-happy

If not, have you checked for water present or live in a radon area: http://www.buildingscience.com/documents/reports/rr-0309-renovating-your-basment

Gary


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