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Radiant heating system choices for new construction projects

When building a new home, garage or workshop, there are basically three forms of radiant-underfloor heating systems to choose from: hydronic (water based), electric cables (high voltage) and a mat system (low voltage).

Regardless of which system you choose, it is extremely important that the system is designed to meet your expectations. Most of these radiant-floor heating systems can be utilized for primary heat applications.

If you choose to use these systems for primary heat applications, you should have a heat loss calculation performed. From this heat loss calculation, a designer can choose the proper heating system to deliver the required BTU’s to comfortably heat your home.

Hydronic systems are installed most often due to their cost and availability. To install this system, the site is excavated at 2” below the final level to allow room to lay 2” polystyrene insulation panels. This high-density insulation will reduce the thermal transfer of heat to the surrounding ground. Insulating underneath the concrete slab and along the perimeter is also a very important step to minimize operational costs and enhance the thermal comfort of your home. Do not cut corners by reducing the amount of insulation. You will pay for that mistake in higher energy bills, caused by the inefficient operation of your system.

A network of cross-linked polyethylene tubing – commonly referred to as PEX tubing – is laid on top of the insulation foam panels where it is then stapled or affixed to rebar or wire mesh to hold it in place prior to the concrete pour. Then the tubing is connected to a manifold system that distributes the heat generated from a boiler fired by either gas, wood, electric or geothermal power. This is one major advantage of a hydronic system – you can easily choose a different heat source and go from gas to electric.

As noted above, hydronic systems are complex. It is important to properly design a system with the correct amount of PEX tubing, circulating pump or boiler etc. If you don’t install enough tubing, the boiler won’t help you heat the home any faster or better.

Conversely, if you have too much tubing installed, you need to be concerned about installing the correct pump size so it will move the water effortlessly throughout the network of PEX tubing. Furthermore if the boiler is not designed to meet the heat loss of the structure, then it will have a difficult time keeping up with the heating demands of your home through a cold winter.

See the complications yet? Sure, you can go to your local big-box store and pick out these components and attempt to plumb them over a weekend’s time. But it is a wise investment to have a professional design and install your system for you!

High-voltage cables or panels are another choice a homeowner can choose to provide radiant floor heating in their home. I recall YEARS ago in the early stages of my career when the use of high voltage cables or cables on mats that would be buried in 8-12”of washed sand. The perimeter of the foundation would have 2” of polystyrene insulation installed to prevent the thermal transfer to the cooler ground. No insulation was placed underneath the cables, as this would provide a heat reservoir. These systems are referred to as electric thermal storage systems. Typically, an electric utility would provide inexpensive off peak rates to energize these cable systems at night during the overnight off peak time frame. These systems quickly faded as hydronic systems became more prominent.

The third system involves low voltage radiant floor heating mats. These would be buried underneath the concrete much like hydronic systems. These systems are simple. There is no complex installation of pumps, boilers or controls. As an added benefit, there is also no maintenance with these systems as there are no moving parts. These low voltage systems are much easier to install than a hydronic heating system and are more efficient, resulting in lower energy bills.

Regardless of which system you have designed for your new home, any radiant floor heating system will surely surpass the comfort expectations of a forced air heating system. I highly recommend a radiant heating design, whether you’re a professional contractor or a DIY weekend warrior.