How Can I Install My Own Radiant Heat Floor?

Question

Is it my impossible dream to think this do-it-yourselfer can install a radiant heat floor? I have no idea where to begin. (Arliss from Spokane, WA)

Answer

Today's Hydronic Supply Answer to Toasty Floors & Rooms

Everyone likes warm feet, and that’s the attraction of radiant infloor heating systems. Various designs use hot water or electricity to warm buildings from the bottom up, and this feature is being incorporated into more and more new and existing structures these days.

What most homeowners don’t realize is how easy radiant infloor heating systems are to install yourself. Advances in technology mean that it’s now quite reasonable to incorporate radiant heat into renovations, additions, perennially cold rooms, and even underneath paving bricks.

If you can do basic plumbing, you can install the piping needed for a hot water radiant infloor system. This approach is called a hydronic system in the trade, and what scares most people away is the apparent complexity of the job. All those pipes snaking around does conjure a daunting image, though the reality of the installation is something quite different.

Hydronics hardware is terrific these days, easy to work with and functions perfectly in both poured concrete floors and on wood-framed situations. The technology is now mature, and the key to successful installation of a radiantly heated floor is understanding the essentials and applying diligence when it comes to putting the hardware in. Although there’s not enough room to go into all the details here, leading hardware manufacturers offer all the technical information you’ll need.

Does pouring a concrete floor seem a little too daunting for you? A multi-purpose garage or workshop is an excellent place to consider hydronic radiant heat under a floor of paving bricks. Instead of a network of pipes worked into poured concrete, create a compacted gravel base that’s six inches thick. Add two inches of rigid foam on top, then nestle hydronic heating pipes into a bed of sand before the paving bricks go on top. Although this system won’t be quite as efficient as a conventional installation in a poured floor, it won’t matter much in a garage or heated outbuilding. An oil-fired hot water heater is an excellent source of heat for small and medium-sized hydronic installations. As long as the heater is big enough for the job, it can provide domestic hot water, too.

Do pipes and a water heater seem like too much trouble to heat a cold bathroom or one of those notoriously cold over-garage bedrooms? Electric in-floor heating mats might be just the ticket. They’re made using high-resistance heating cables woven into a fabric mat. Just roll it out, test the mat electrically, then cover it over with ceramics, laminates, or most other kinds of finished flooring. The thermostatically controlled system is simple and adds almost no additional height to the completed floor.

Regardless of whether you’re considering hydronic infloor heating or electric infloor mats, success begins with a boring bit of math called a heat-loss calculation. This is a computer-generated analysis that estimates the total amount of heat that will escape from your building at or near some minimum expected outdoor temperature. Your radiant equipment supplier can work out the final numbers for you, based on information you provide on building size, wall and roof construction, plus the number of windows and doors involved. When the computer finishes crunching numbers, it produces an overall figure in something called British thermal units per hour (btus/hr). This number is used to size the heat source that powers your hydronic system, plus it does something else. It allows the system designer to make recommendations about pipe spacing for various building areas. A workshop floor, for instance, usually heats fine with a 12-inch spacing between runs of 1/2-inch diameter hydronic pipe, though that should be tightened up to around 6 inches apart on the couple of runs nearest exterior walls. You need more heat there to make up for energy losses along the edge of the slab. An 8-inch spacing is better suited for living spaces.

With warm weather here, it’s easy to forget about heating systems. But as the building season gets under way -- and, Arliss, as you think about the cold Spokane winter nights ahead -- now’s the time to consider the heating options that will make the coming winter a whole lot easier to take.

This material was reprinted with the permission of casaGURU. casaGURU is an everyday, everywhere, anytime homeowner website built on the premise that every home deserves a house expert.

Extra Help: For more information on Installing a Radiant Heat Floor, click on these links to the Radiant Panel Association and the Hydronics Industry Alliance for some great advice and The Handyman for some step-by-step installation guidance.

Also check out a radiant floor system called ThermoSoft that many DIYers recommend for easy home installation. And we just found a great radiant underfloor heating mat supplier - Warm Your Floor.