Baby, it's cold outside, which can translate to it being pretty darn cold inside, too.

Thank goodness for insulation and heating systems, but when it comes to directly heating up the tootsies, a radiant floor system is like a warm cup of tea nestled in the palms of both hands — only the snuggly warm feeling starts at your feet and works its way up.

Heat rises. Mechanical gurus figured out how to use that basic, common-sense premise to heat the floor and direct the heat into the living space for overall warmth. Even before radiant floor systems, radiators were on the scene. Radiators are radiant heat but never really worked well with room layouts and are insanely heavy. Plus, unless a cover is constructed, the intense heat of radiators isn't shielded in any way from direct contact.

Radiant heat systems, whether electrical or hydronic, can be placed in wall sections but are most commonly used in floor applications. Radiant layouts can be retrofit under flooring where the underside is accessible, installed over concrete slabs and in concrete pours, or worked into prefabricated plywood and aluminum sections sandwiched between a sub-floor and a finished wood or tile floor.

Some systems seem more DIY-friendly than others. Installing a hydronic, or heated water, floor layout is relatively easy, much like a big maze or puzzle, but connecting it to the boiler requires a heating specialist, according to Patrick Martin, of Patrick L. Martin Remodeling, Reinholds.

A handy homeowner can definitely do the grooved plywood installation of the project, according to Randy Miller, project manager and an owner at Robert H. Ranck Plumbing, Heating and Air Conditioning, 2541 Marietta Ave.

"You can put the wood down and can even run the tubing, but other than that, an HVAC professional should be consulted," Miller says. "... The job should be sized and laid out by a professional, and then, of course, any hookup is a technician's job."

A home with boiler heat is perfect for the hydronic radiant system. According to Miller, a fossil fuel hot water heater, coupled with a heat exchanger and circulators, also does the job.

There really are two main components to a hydronic radiant floor heating installation: the manifold and thermostat that make the system operational, and the plywood installation which secures the tubing that delivers the water.

A manifold is the zoned brain that takes in the supply pipe of hot water from the boiler and directs the water out to the smaller, flexible tubing needed in each radiant zone. The tubing is leak-free, nontoxic and flexible polyurethane, and can handle really high temperatures. It snakes through the floor grooves and cannot be spliced within the "maze," but must return to the manifold to continue on.

The grooved 1/2-inch thick plywood sections come in 4-foot lengths that are 6 3/4-inches wide. The central groove accepts the tubing. There also are pieces that create the turning radii. Once laid out, Martin says, the parallel runs of tubing are about 6 1/2 to 7 inches apart, a distance that provides even heat distribution.

The prefab grooved plywood sections have another key element: They're backed with a thin layer of aluminum that reflects the heat and directs it into the living space.

Martin explains that the tubing's route must ensure that floor sections closest to the exterior walls are run first and are closest to the point of origin, since the water is hottest when it first leaves the manifold. That loop returns to the manifold to be sent back to the boiler and recirculated.

Working, for example, in a bathroom, it's important to pay attention to some potential roadblocks, such as the toilet. Martin notes that all tubing that will carry hot water must be a minimum of 1 foot away from the toilet base so it doesn't heat the wax ring that keeps the toilet anchored. It also, he says, is "routine to stay at least 2 feet away from any wall that will have cabinets attached", because base cabinets are 24 inches deep, while the toe kick is set back a standard 3 inches.

Each loop of tubing that comes out of and goes back into the manifold can't cross at any point, so the layout must be carefully considered. To keep track of which grooves of the plywood are being used in the layout, it helps to mark them with a marker and also indicate how many feet of tubing are needed to a certain point.

The manifold needs to be accessible for the initial settings and for periodic maintenance on the boiler. "Because there's a bleeder valve on the manifold, when the boiler is serviced, the person will have to open the valve to drain the system," Martin says.

It's not a bad idea to map the layout of the tubing. That way, when the finished floor covers the radiant tubing, there will be less chance of accidentally damaging the tubing with future construction. If the homeowner will install a tile-finished floor over the grooved plywood, it's best to put a thin layer of cement backer board to give a smooth base for tile installation. Hardwood strip flooring can be done directly over the grooved plywood, according to Miller.

Martin shares a trick for determining where radiant tubing is located if the finished floor already is installed. Simply turn up the heat and put some water on the floor, he says. "The area that dries first helps you map the tubing."
rmcroberts@Lnpnews.com