In-Floor Heating Systems

Radiant in-floor heating is possible in almost every type of renovation and new construction project.

Written and Photos by Steve Maxwell

Everyone I know likes warm feet when it’s cold outside, and that’s the attraction of radiant in-floor heating. You can’t beat it for even, efficient distribution of warmth in any building. But there’s a problem. Too few homeowners understand that radiant systems can be installed in wood-framed floors, too. You don’t need to pour a brand-new, pipe-embedded concrete slab to enjoy warm floors and happy feet. While this standard option is an excellent and widely applied choice, it’s not the only one. Radiant in-floor heating is possible in almost every type of renovation and new construction project.

There are two types of in-floor systems. The most common uses pipes to carry warm water through the floor structure. This is called a hydronic system, and it turns the entire floor of your home into one big heating radiator.

Another completely different option includes thermostatically controlled, high-resistance electric heating grids or mats embedded in floors. Think of it like an electric blanket installed under your feet. Both systems have strengths and weaknesses that you need to know about before you can make an informed decision.

Hydronics in Wood-Framed Floors

Hydronic in-floor heating systems make the most sense in applications that involve large areas of your house. That’s because pipes in the floor are only part of the equation. You also need to consider an appliance to heat the liquid flowing through those pipes, and a control panel to regulate the flow thermostatically. While none of this makes sense for just a bathroom or den, it’s quite practical for a large portion of your home. This is where hydronics shine.

There are three ways to install a network of in-floor hydronic heating pipes in a wood-framed floor. You can fasten them to the underside of the subfloor from below. Easy, yes, but heat transfer upwards to the floor surface isn’t terrific. You can also embed hydronic pipes within self-leveling concrete poured directly on top of a wood floor. Thermal performance is excellent, but the work is troublesome, messy, expensive, and reduces ceiling height more than any other approach.

An excellent compromise between these two options involves setting heating pipes within grooves created in the top of the floor. You can do this by laying down 8-inch or 10-inch-wide strips of 3⁄4-inch plywood, with a 3⁄4-inch to 1-inch gap between neighbouring strips to create a pipe groove. Set reflective foil insulation in the gap to direct heat upwards, then lay pipes in the grooves and install a finished floor on top. Some manufacturers offer moulded plastic grid systems for use in place of the plywood strips.

Radiant in-floor heating is fast becoming a must-have home feature. It boosts home wintertime comfort levels more than anything else. The good news is that even those of us who don’t live on a slab of concrete can now enjoy the warmth.