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Radiant Floor Heating/Humidity problems radiant heat garage



I'm so happy to find this site. I'm having serious moistur/humidity problems and no one knows why. I just built an attached 30x41 3 car 2 story garage with an unfinished great room above the garage. This is in northeast pa 18431.  I put radiant heat in the whole floor and keep the heat at 55-60 the garage is insulated with fiberglass but no sheet rock and the second floor is insulated and I have a space heater keeping the heat at 55 in the second floor.  I have good garage insulated doors.  My problem is my garage is overly humid it's crazy.  The walls doors windows ceiling everything sweats excessively.  I didn't notice this until two weeks ago and The insulation on the walls was soaking wet.  There isn't any water getting in the garage other than a little snow from our cars but since I noticed and pulled all the insulation out Ive installed 3- 65 pint dehumidifiers and have bought a humidity tester and even with all three dehumidifiers running 24/7 I can only get the level to 65 or 60.  When I first got the tester the level was at 95.  I read your previous post about ervs or hrvs but I've never heard of them and just need some advice because no one in my area has any clue what to do and I need to do something  different.  Please Help!  Thank you very much!

The relative humidity in a cold garage is usually quite low but when heated the melted snow can raise humidity dramatically. The answer, as you have surmised, is ventilation. My wife raise the garage door an inch or so until the water dries of the floor. Not high tech or real energy efficient, but a heated garage does not cost much nor can one justify a heat recovery ventilator for the occasional "airing out".

Of course you could install an exhaust fan but you still need to relieve the negative pressure created by the fan e.g. open window or door.  

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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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