Ontario's Plain-English Guide to Custom Home Buildingπ 705-533-1633 | βοΈ 1-866-868-6606 | βοΈ info@icfhome.ca
Radiant Floor Heating Problems in Ontario: Cold Zones, Air in the Loops, Short-Cycling Boilers, Slow Response, What a Homeowner May Check and What Needs a Licensed Tech
Heating, Cooling & Ventilation
When the Radiant Floor Is Not Right: Five Common Problems, the Five Things You May Check Yourself, and the Line Where You Stop and Call
A radiant floor that was designed and commissioned properly is the quietest, least troublesome heat in the house. When one acts up, it is nearly always one of five things, and most of them are visible from the manifold and the thermostat without touching anything that burns gas. I have been building these floors since the early 1990s and fielding the calls about them for just as long. This page is what I tell people on the phone: what you can look at, what to write down, and what is a job for a licensed technician.
What You May Check Yourself
These are looks, not repairs. Write down what you see; it shortens the service call and the bill.
- The thermostat. Is it on heat, set above the room temperature, with fresh batteries if it takes them, and not on a schedule someone forgot? A slab takes hours to respond, so give a change half a day before you judge it.
- Power to the system. Is the boiler service switch on and the breaker not tripped? A tripped breaker can be reset once. If it trips again, leave it off and call.
- The zone valve or actuator indicator. Most manifolds have a small lever, window or light on each zone valve or actuator that shows open or closed. Turn the cold zone’s thermostat up and see whether its indicator changes after a few minutes.
- The manifold flow meters. Many manifolds have a small glass sight tube on each loop. Note which loops show flow and which do not, and compare them with the commissioning sheet if the installer left one.
- The pressure gauge reading. Read the boiler or system pressure gauge and write the number down, then compare it with the number on the tag or commissioning sheet. A reading that keeps dropping over days, or one near the red zone at the relief valve, is a service call, not a top-up.
Stop here if: you smell gas (leave the house and call the gas utility from outside), a CO alarm sounds (get everyone out and call 911), there is water on the floor under the boiler, or the boiler shows a lockout. Write down any error code on the display and call. Do not keep pressing reset.
What Needs a Licensed Tech
Anything inside the boiler cabinet, the burner, the venting, the gas valve or the gas piping is gas work for a TSSA-registered fuels contractor with a certified gas technician, usually a G2 in a house. That includes resetting a lockout more than once, cleaning a burner and checking combustion. Nobody else opens a sealed combustion appliance, and neither does the homeowner, however handy.
Purging air from loops, adding water to the system, adjusting the mixing valve, changing the outdoor reset curve, replacing a circulator and balancing loops are hydronic jobs. They need a tech who knows the system and the pressures; a garden hose and enthusiasm have flooded more mechanical rooms than I can count. Electrical work on the controls for hire is done by an ESA licensed electrical contractor.
The Five Problems, One at a Time
One cold zone. Start with the zone valve indicator. If it never opens, it is the thermostat, the wiring or the actuator, all cheap fixes. If it opens and the loops show no flow, it is air or a closed balancing valve. If it opens, flows and the floor is still cool, look at the floor covering: a thick rug or engineered wood on foam over a slab heats like a sweater over a sweater. The flooring over radiant page has the R-values.
Air in the loops. Gurgling or trickling in the pipes, and a zone that works one day and not the next, usually mean air, often after a repair or a top-up. It needs purging loop by loop at the manifold, and the air separator should be checked; that is a tech job.
A short-cycling boiler. If the boiler fires for a minute, shuts off, and fires again all day, it is too big for the load or the zones are too small, a pickup truck hauling a bag of groceries. It wears out the igniter and wastes the efficiency you paid for. Fixes are controls, a buffer tank, or at replacement time a boiler sized from a room-by-room CSA F280 heat loss. The sizing mistakes page explains how it happens.
Slow response. Not a fault. A slab is a big thermal mass, and turning the thermostat down at night and up in the morning means a cold breakfast. Pick a temperature and leave it. An outdoor reset control, set up properly by a tech, lets the floor adjust before the house feels the weather.
A zone that never satisfies. Every other zone is fine and this one runs all winter and never gets there. Usually it is design: a loop too long, tubing spaced too far apart, a room with more glass than the floor can make up for, or water too cool for that room. Sometimes it is a new hardwood floor nobody checked. A heat loss on that room settles it; the radiant design page explains what the designer should have done.
What Fixes Cost
| Fix | Range | Note |
|---|---|---|
| Annual boiler service, as for a furnace | $150 to $250 | allowance; catches most of this early |
| Manifold and zone controls, one bathroom | $500 to $1,500 | replacement or upgrade |
| Manifold and zone controls, a basement | $1,500 to $3,500 | |
| Manifolds and zone controls, whole house | $4,000 to $10,000 | |
| CSA F280 heat loss to settle a sizing argument | $395 | OntarioHeatLoss.ca |
| Condensing boiler replacement, heating only | $5,500 to $11,000 | $8,000 default |
| Combi boiler replacement | $5,000 to $10,000 | $7,500 default |
Why Ontario prices are all over the map: when the fix turns into a new boiler, the prices we checked are far apart. A Toronto contractor’s guide puts a standard boiler at $4,500 to $9,500 and a premium one at $7,500 to $14,000; for a combi, one price guide says $3,500 to $10,000 and up and our own page says $5,000 to $8,000. Whether the venting, the controls and the old-unit removal are in, the brand, and a January no-heat call against a booked September visit move it. Budget $8,000 for a boiler or $7,500 for a combi and get two or three quotes on the same written scope.
Before anyone sells you a new boiler for a cold zone, make them show you the boiler is the problem. A $395 heat loss report from OntarioHeatLoss.ca is cheap beside an $8,000 boiler that heats the same cold room just as badly.
Questions people ask
Why is one zone of my radiant floor cold?
Check whether its zone valve or actuator indicator opens when you turn that thermostat up, and whether its loops show flow at the manifold. No opening points to the thermostat or actuator; no flow points to air or a closed valve; flow and still cold points to the floor covering or the design.
How do I get air out of my radiant floor loops?
Have a hydronic tech purge them at the manifold and check the air separator and system pressure. It involves filling and draining a pressurized system, and done wrong it lets more air in or floods the room.
What should the pressure gauge on my boiler read?
Whatever the installer set it to, which is usually written on a tag or the commissioning sheet. Read it and write it down. A number that keeps falling, or one near the red zone, is a service call.
Why does my boiler keep turning on and off?
Short-cycling usually means the boiler is too big for the house or the zone calling for heat. A tech can adjust controls or add a buffer tank; at replacement, size the new one from a CSA F280 heat loss.
Is it normal for radiant floor heat to be slow?
Yes. A slab takes hours to change temperature. Leave the thermostat at one setting; setbacks make the floor slower, not cheaper.
If the answer is a new heat source
The HVAC system cost comparison calculator prices five systems on your house, including a combi with radiant and air-to-water with radiant, installed and over 15 years. If you already have a repair or replacement quote, the $99 review reads up to three of them and tells you whether the work matches the problem.
Sources and further reading
- TSSA: hire registered and certified fuels professionals: Technical Standards and Safety Authority: why gas furnace, boiler and water heater work must be done by a registered contractor with a certified technician, and how to check.
- OntarioHeatLoss.ca services: heat loss reports, full HVAC permit packages and radiant heating design, with prices.
- Gas furnaces: Canada energy efficiency regulations: Natural Resources Canada: the minimum AFUE rules for gas furnaces sold in Canada and what the efficiency ratings mean.
