A glycol radiant floor is a network of tubing set in the concrete slab or installed under the floor, carrying a mix of water and glycol heated by a boiler or a heat pump. The glycol acts as antifreeze: if the heating stops or the building stays cold, the loop does not freeze. At Wilfrid David in Chénéville, we install these systems across La Petite-Nation, mainly in cottages that are not heated year-round, garages, workshops and new homes built on a slab.
How a hydronic radiant floor works
In a hydronic radiant floor, the floor is warmed by hot water, or a water and glycol mix, flowing through a series of small-diameter pipes. The system includes a heat source, either a boiler or a heat pump, and pumps that keep the fluid circulating.
The floor warms up first, then releases heat into the room from below. There is no forced air and no baseboard heaters, and the heat is distributed evenly.
The loop is closed: the fluid circulates between the heat source and the floor without ever coming into contact with the household drinking water.
Why glycol instead of water
In a house heated all winter, plain water works very well. Glycol is used when there is a risk of the loop freezing: a cottage closed for part of the winter, a garage heated only during working hours, or an extended power outage in cold weather. A frozen loop inside a concrete slab means major repairs, and glycol removes that risk.
Glycol does have characteristics that need to be taken into account:
- it carries less heat than water, so the pumps and the overall system must be designed for it from the start;
- it must be propylene glycol made for heating systems, with corrosion inhibitors, and never automotive antifreeze, since ethylene glycol is toxic;
- it ages and can become acidic over time, which can damage the system. An annual check of concentration, pH and corrosion protection is therefore recommended.
When properly maintained, a glycol system is reliable. That regular check is simply part of owning one.
In the slab or under the floor
Installation in the slab is the most common approach in new construction, basements and garages. The tubing is fastened over the insulation before the concrete is poured. Once the slab is poured, the layout is permanent, so the loop design, the zones and the supply locations must be planned in advance. Insulation under the slab is essential to keep a large share of the heat from being lost to the ground.
A concrete slab is heavy and holds heat for a long time; it even works as a form of heat storage. It is very comfortable, but slow to respond: it takes time both to warm up and to cool down.
Installation under the floor is the preferred option for renovations, when the underside of the floor can be reached, for example through the basement ceiling. The tubing is fastened beneath the subfloor, with insulation below it to direct the heat upward. This type of installation responds faster than a slab, but the structure and access must allow for it. We assess that on site.
What to consider before starting
A radiant floor is not well suited to large temperature swings. Deep night-time setbacks, common with baseboard heaters, do not work well with a heated slab, which needs several hours to return to the set temperature. It is best to choose a steady temperature and leave it there.
A radiant floor heats surfaces rather than air. It does not replace ventilation, and air conditioning, if wanted, has to be planned separately.
It is also a complete system made up of a boiler, pumps, an expansion tank, manifolds and controls. It should be planned along with the rest of the house, ideally before construction begins. Our article on planning a new build covers this in more detail.
Where this system works best
A glycol radiant floor is especially well suited to a garage or workshop on a slab, a cottage kept at a minimum temperature in winter to prevent freezing, and a new house with a concrete basement that is used regularly.
Other solutions may be more appropriate in some cases. For a single-room renovation, electric in-floor heating is often simpler. For a building that needs to warm up quickly on arrival, a system that heats the air responds better. If you close your cottage for the winter, see also our article on closing the cottage for winter.
When to call a professional
Contact us before pouring a slab, before closing in a basement ceiling, or if your glycol system has not been checked recently. We can design the installation, test the fluid and advise you on the option best suited to your building. Call us at 819-428-3161 or see our radiant heating page.
Filed under Radiant heating
