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Radiant Floor Heating/Whole house radiant heat, low-voltage or hydronic


QUESTION: I am building a 3000SF house in Philadelphia area with spray form insulation. I really want to get whole house radiant heat as primary heat source. I did a lot of research but still not sure what to get. I know the best should be hydronic radiant with NG broiler but the house don't have natural gas, only electric and propane. After researching, the following seems to be my options, please advise. I am very concern the energy cost to run the system. This the fuel cost in my area as follows:
Electricity 0.15per kwh, Natural Gas 0.97/CCF, Propane about $2.6/gallon
1) Hydronic radiant with propane broiler
2) hydronic radiant with electric broiler
3) Low voltage radiant heat, I seems very limited information on it and not sure how expensive to operate it.
4) My last choice will be heat pump with area electric radiant heat (110v or 220v).
Or would it be without NG, it is not suitable to do whole house radiant heat?

ANSWER: Everybody wants radiant floor heating, but how to get it can be a stumbling block.

I have installed many radiant systems including high and low voltage cable systems. In fact I had two low voltage radiant floors in the bathrooms of a home I recently sold. No matter how you do it, a radiant floor can't be beat for comfort or operating efficiency.

However, electric cable radiant floors fix the heat source forever. In other words, you can't change your mind. So when designing radiant floor heating systems for primary heat in a residence I always use PEX hydronic radiant floors, walls and ceilings. The reason is simply flexibility of heat sources, controls and overall efficiency.

First, a room-by-room Manual 'J' heat load to determine the boiler and radiant floor outputs. Once the size of the boiler is determined the type of radiation will help us choose the proper boiler and of course domestic hot water system.

Natural gas is almost always the best choice for space and water heating and a condensing boiler the best way to use this clean and plentiful fuel source as born out in your local Philadelphia market by the following numbers.

Cost per million Btu.

NG    10      therms x  0.97 = $ 9.70

LP    11     gallons x  2.60 = $28.60

Oil    7.4   gallons x  3.90 = $28.86

Elec  293         kW x  0.15 = $43.95

The electric boiler is the only hydronic heating boiler considered "100% efficient" and so the other fuel values must will be higher depending on the combustion efficiency of the boiler you choose and the quality of the installation.

Even so, it is clear to see that a 95% efficient condensing boiler is the easy choice against any electric option short of a ground source heat pump raising the other question of installation  cost.

If you need further help specifying a heat source or finding a local competent installing contractor feel free to drop me a line.

---------- FOLLOW-UP ----------

QUESTION: According to your calculation, Elec cost 4.5 times over NG for the same btu output. I am building the exact same house of my builder that he is living now, same size, same insulation, except his house has NG boiler hydronic heat. If he spend $300 for NG, does it mean it cost 4.5 times if I use electric boiler? I understand electric is 100% efficient but electric is much more expensive.
Do you recommend whole house low voltage radiant heat? I don't know the result and operating cost. Almost all the info on the web about low voltage review are the same companies that sell the system, not actual user have use it.
I like radiant heat but I don't want after seeing the energy bill and shut off the whole system.  Also, do u have any experience on geo heat? How costly to install it?

Badger Boiler Vitodens
Badger Boiler Vitodens  
ANSWER: In most of the US where natural gas is available its price has been relatively low and stable for many years now. The trend is in the same direction. I just installed my 16th manufacturer of condensing boilers all of which were 93% AFUE or higher. Most are now at 95% AFUE.

In your area, as in most, a condensing boiler, either combi or with an indirect-fired water heater, is the best choice of most hydronic work and hydronic radiant floor heating in particular.

Natural gas is clean, safe, efficient and is piped right into your house. There is currently no better choice for space and hot water heating for the typical residence where natural gas is available.

---------- FOLLOW-UP ----------

QUESTION: My issue is NG is not available on my site, and what is my 2nd best choice to do whole house radiant heat?  Thanks for your time.


It appears the choice is between propane and oil. In this case I would interview the local contractors and consider the best oil and "condensing" propane boilers they offer. Ask about their knowledge, experience and formal "factory" training for the boilers they advocate.

These are usually two distinct camps so opinions will vary, but the facts stay the same.

The contractor that gets my business shows me a sample of a current computer-generated Manual "J" heat load analysis.

The boiler used should have weather sensitive controls (outdoor reset), which is a standard feature on all gas-fired condensing boilers but must be added to most oil-fired boilers. We have have few oil boilers here in the Minneapolis but like to use Buderus and Crown oil boilers when we do. Buderus has one of the most advanced control systems for oil-fired boilers on the market.

Outdoor reset control will always save fuel and make you more comfortable, more especially with hydronic radiant floor heating.

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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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