Radiant Floor Heating radiant floor heating and wood floors, Gypcrete, staple up radiant floor

Radiant Floor Heating radiant floor heating and wood floors, Gypcrete, staple up radiant floor

Radiant Floor Heating /radiant floor heating and wood floors



Hello there,

First I would like to say I have enjoyed this web site and have gleaned a wealth of information from it already. Thank you for providing such an informative site.

We are in the process building a log home kit in NW Montana. This home consists of a full ICF walk out basement (all of the walls are completely exposed) consisting of 1344 square feet, a main floor which is also 1344 square feet and a loft area with rather large dormers that is approximately 800 square feet. This loft will be enclosed by walls.

We have installed hydronic radiant floor heating in our basement consisting of two zones. One for the garage portion and one for the living portion of that area.

We have also installed two zones on our main floor with sleepers and gypcrete. Currently we have no plans to heat the loft as the flooring that comes with our package is also the finished ceiling on the main floor. The loft occupies about 2/3 of the house’s floor plan. We have been told that the main floor radiant system will passively heat the loft and told it won’t. We aren’t counting on it to do so.

My question is in regards to the flooring. It is 1 and a 1/2 inch tongue and groove pine that is 5″ wide. This is to be the flooring used on our main floor as well. I am concerned as to whether we will be able to feel the heat adequately enough on our main floor. The pex is laid 8″ on center. Our great room has a 26 foot vaulted ceiling and measures 12 feet by 32 feet. We have a prow front with wall to wall and floor to ceiling windows.

We will be adding insulation in the basement ceiling below. Is it necessary to have foiled back insulation in this application.

Our plumber has chosen a 23 KW Thermalec boiler. Electricity is extremely reasonable here at about 6 cents per KW. There is no natural gas in the area and propane is quite expensive comparably.

We had been advised to use a staple up system, we ended up not going that way as one person I know that has it is having a dickens of a time keeping his main floor comfortable, yet his basement with pex in concrete is extremely comfortable.

So do you think we’ll have adequate heat transfer for our main floor? We can experience very cold Montana winters and I hate being cold.

In advance thank you for any advice you can provide us.


Radiant Floor Heating radiant floor heating and wood floors, Gypcrete, staple up radiant floor

I appreciate the compliment.

Your installer should provide a heat load per room before the first tube goes down.

I start every job with a heat load analysis. As every room has a different load, each may need a different system. The trick is to choose a system that heats the coldest room in the coldest weather with the lowest water temperature possible saving money on fuel and increasing comfort all at once. Floor covering can make a big difference as you have noted, so this goes into the equation when designing for load and response time. The more resistant the floor covering the longer the response time (room gets cold) and the hotter the design water temperature (you burn more fuel).

Once you know the load you can choose the type of heating emitter and from there the heat source and/or design water temperature.

If electricity is the fuel source, you will want an electric boiler with built-in outdoor reset. The max supply temperature will be 140°F to help protect the Gypcrete and wood floors. If the output water temperature is high enough to satisfy the thermostat in design conditions (coldest few days of the year) then supplemental radiation in order. This is OK, especially if your contractor has done the math and anticipated the need ahead of time.

Without a heat load you just guess-by-golly. In your great room the most efficient radiant floor may not due and a supplemental heat source may be employed such as panel radiators, radiant walls or cast iron baseboard.

The insulation below will depend on the heat load above and the below the floor your heating.

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