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Radiant Floor Heating/Sandwich Style Radiant Floor Heating


QUESTION: I've decided to install sandwich style radiant in my basement.  I have an existing slab.  My layers will be as follow.  I will place vapor barrier, then 1 or 2" EPS foam with stripped pieces of OSB board for pex tubing.  Someone suggested instead of 2" EPS foam to just lay down 3/4" OSB board which will have the same effect for barrier resistance.    
My question is, would you suggest I put down 1" or 2" Foam or 3/4" OSB as the first layer.  My finishing floor will be engineered hardwood and tile in bathroom.
Which heat plate type/brand would you recommend and what spacing should I put them?  Thank you

Badger Radiant Designs Sandwich
Badger Radiant Designs  
Badger Radiant Designs over-pour panels
Badger Radiant Designs  
ANSWER: First, OSB should never be in full-time contact with the ground or other source of full-time moisture such as most slab-on-ground basement floors. A vapor barrier is just that. What you likely are referring to is a vapor retarder such as a 6 mil plastic sheeting. Not good enough, and made worse by floor coverings that will not breath.

I like most the various panels that are made-to-order of radiant "over-pours" or dry "sandwich" radiant floor heating systems as you describe.

For over-pour radiant floors we specify and install a variety of pre-made products including Crete-Heat, Viega Snap Panel and Uponor Fast Track (pictured).

We have used a Korean made product distributed by Mr. PEX(Koreans have been great fans of radiant floors for a long time). The one we used goes together like a locking rubber mats but are instead plastic with thin "insulation" on the bottom and grooved steel on top to accept the PEX tubing. For basement applications this is adequate if not the most efficient.

Another more recent product we love to use on floors, walls and for radiant ceilings incorporates high density EPS at a higher R-value with an aluminum heat transfer plate neatly glued to the panel. The assembly is available for 1/2 and a lower profile 3/8" PEX configuration.

The insulation value below floors is determined by the climate and the construction of the home. Here in Minneapolis we mainly use R-10 XPS but floor covering matter. If you want to beef-up the nominal insulation offered by one of the "dry" radiant heating systems you must be careful to use the minimum psi recommended for human traffic.

Spacing is dictated by heating loads, design water temperature and floor coverings.

With the typical wood flooring product or light carpet, 12" will "heat" most finished basements in North America, but it never hurts to do a proper heat load. I am not a fan of home-made sandwich systems but many work well in floor-warming applications and in mild climates or basements...

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QUESTION: Thank you for the info.  What is the Korean made product called?  I'm trying to research it.  Also you mention another more recent product you love to use on floors incorporates high density EPS.  What is the product called or is this a home made sandwich system you are explaining?

Thank you

Badger Radiant Designs Roth Panels
Badger Radiant Designs  
ANSWER: Mr. PEX calls their retrofit sandwich radiant floor heating system RetroPanel.

Roth makes their own high performance sandwich radiant panel known as RothPanel.

I know, not much imagination, but they didn't ask me...

You should get professional radiant heating design help, as "radiant design by Internet" often leads to much waste and long lasting disappointment, instead of perpetually perfect comfort.

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QUESTION: Thank you for the info.  If I go with my own Sandwich style, I'd like to know which heat transfer plates you'd recommend.  RHT, Thermofin U, Heatlink.

This a question for your designer.

The answer is in the heat load and specific application. The farther you get from a pre-engineered sandwich type radiant system the more you need professional design services.

We design all sorts of radiant floor heating systems for DIY, professional installers and engineers alike.  

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Morgan M. Audetat


Radiant panel heating design, including floors and ceilings, European wall panels and snow melting for residential and light commercial buildings..............................................................-Master of Steam and Hot Water,City of Minneapolis....................................................--- Master Plumber, State of Minnesota...........


30 years..... Charter Board Member - Radiant Panel Association, former manufacturer of condensing boilers, former national distributor of radiant floor products, son and apprentice of mechanical & plumbing contractor. Current mechanical/plumbing contractor specializing in hydronic based, integrated HVAC systems. Radiant floor heating/cooling. Snow Melting. Condensing Boilers. Indirect water heaters. System design, consulting and technical training world-wide. Licensed contractor, designer, installer and consultant.

B.S. University WI 1981 CONTINUING EDUCATION: Viessmann Condensing boiler and Solar water heating certification 2010, N.D.S.U. Lead Worker RRP certification 2010, Knight condensing boiler certification 2009, Wrightsoft Manual J CAD certification 2009, RPA Designer & Installer Certification 2008, Nate Hydronic/Forced Air Certification 2008, Uponor/Wirsbo advanced design school certification 2007, Buderus Wall-hung certification 2007, Power Limited License (low voltage controls) 40 CE credits 2005, Basic Hydronic Certification IPEX & Northern Alberta Institute of Technology 1998, Charter Board Member - Radiant Panel Association 1994, Residential Off-Electric to Hydronic Conversion Heating School Canadian Hydronics Council 1994, B&G Little Red School House 1993, Rood Utilities (now Auburn Technical Institute) Oil Burner School 1993 ,Tekmar Controls residential and commercial 1993, Division Manager and Advanced Hydronic Seminar Instructor for the first Exclusively Hydronic Radiant Floor Distributor in the USA 1990, Hydronic Radiant Heating Association Workshop participant with Richard c. Bourne, PE spring 1988, Master Plumbing, Hydronic, Solar Course Red Rocks Community College 1987.

Awards and Honors
2009 System Showcase Award - Radiant Panel Association

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