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Radiant Floor Heating/Glycol or not? percentage or mix?


I live in North Alberta where in winter we get 0 to -40deg temps.  I have an attached garage that is insulated and drywalled and I am thinking that I do not need to add glycol for in floor heat as I plan on keeping it running at around 8 degs in the winter months. Am I thinking wrong?  Thanks

Answer snow melting
Water will freeze in any environment with an ambient temperature below freezing (0 C for you folks up in Canada). The more extreme the environment the more risk there is for freezing, should systems fail, doors or windows be left open, etc.

I generally do not specify propylene glycol or any anti-freeze for hydronic systems unless the need can be justified, since the heat transfer and pumping efficiency are both diminished (you pay more for fuel and electricity). The higher the concentration of anti-freeze the greater the penalty. This coupled with the fact that all anti-freeze must be maintained, should make one hesitate before buying anti-freeze for any radiant floor. If you decide that you must have anti-freeze to protect particularly threatened hydronic components, then the anti-freeze mix or percentage should be designed for "burst" rather than flow. The only reliable way to determine the mix is with a refractometer in the hands of a trained and qualified technician.

We are often called out to work on new radiant floor heating systems that are not working up to par and are often disappointed to find the entire system filled will a 50% mix of propylene glycol. So the entire space heating system is compromised just on the odd chance that the radiant floor zone in the garage will freeze and the PEX embedded in the slab will burst. This is a silly practice since all of the system is compromised for one big room at kept at 50F/10C.

If you feel you must use anti-freeze for your garage zone the proper way to install it is with a sub-system consisting of a plate heat exchanger, pump, expansion tank, PRV, air eliminator and controls..., which is why the proper way is not always followed.

This of course assumes that no one has noticed the heat has gone off in the garage.

If the PEX in the garage slab does happen to freeze it does not necessary mean that it will burst, as we have been on several jobs where the outside loop next to the leaky garage door has frozen to slush but not to burst. If I perceived an unusual risk I would install a thermostat with a freeze alarm and send a message to my phone.

I have insurance and will use it should my garage door open itself in severe weather with a hard blowing nor-easter, the pump fails, the boiler quits and no one is at home for a day or two while my "unprotected" garage floor freezes to death.

Respected authorities disagree so I leave up to the individual and his affinity for risk.  

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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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