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Radiant Floor Heating/Basement radiant floor tankless WH NO!!!!!!!!!!!!!!!!!!!!!!!!!!!


My house was built in 2004 with a gas-fueled forced air furnace to heat the main & upper levels.  The basement was left unfinished but provided with hydronic heat tubes in the concrete floor slab.  I am now looking at having the basement finish completed which will include everything needed to get the hydronic heat functioning.  I am analytical and detail oriented so I have been doing a fair amount of research into the options for heating the water in the hydronic system.  There are a lot of pro's & con's to each.  I'm drawn to a gas appliance because of the long range fuel costs (much cheaper than electric - even utilizing off-peak programs#.  I believe storage tank water heaters listed for space heating are not cost effective with the requirement for heat exchangers to separate the two water uses.  That leaves me with an on-demand water heater listed for space heating or a boiler.  Given these two options I'm wondering if it is possible for an on-demand water heater approved for such a use could meet my needs as they are certainly more cost effective than a boiler. The bottom line is that I will be making an investment in my home and want to make the right choice.  The HVAC & plumbing contractors I've talked to are recommending electric mini-boilers and aren't open minded.  I don't want those electric costs.  Here's more info on my house.
Built in Elk River, MN in 2004, 1200 square feet with full basement #8' ceiling) and 2 stories, gas furnace to heat main & upper level, condensing water heater for DHW. Could you please provide some direction which may include recommendations or point me to a contractor who can help? Any advise would be appreciated.

You will find in my previous comments on this site my absolute distain tank-water heaters misapplied to radiant floor heating or combi-water and space heating applications. They are water heaters, made to heat potable water from vary low to relatively high temperature rise, say 45 to 130F.  

A space heating boiler applied to a radiant floor is made to heat at lower temperature, 70-110F, for very long periods of time.

As you correctly point out, the tankless water heater is cheap, but not necessarily a good value. Worse yet, I find the folks that use them, no less about radiant floor heating than they might.

My personal favorite for most low-load or basement radiant slabs in a storage type, sealed combustion, direct vent condensing water heater with a sub-assembly to control the radiant side. Not cheap, but effective and durable with more domestic hot water and space heating capacity than you need but not over-sized, like the smallest condensing boilers available.

There is a new breed of boiler--more like a tuned up tankless water heater, that promises to be more efficient at space heating while still producing copious amounts of hot water.

Where natural gas is available electric boilers are almost never a good investment.

If you contact me directly we can discuss them. You are in our service area.

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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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