How a Boiler Heats Your Home: Hydronic Heating Explained
A boiler heats water and circulates it through radiators, baseboards, or in-floor loops to warm your home with steady, quiet, radiant heat. Here's how the system works and what maintenance it needs.
Reviewed by Nathalie Brooks, Owner of Brooks Heating & Air and Treasurer, HRAI Contractors Division Board of Directors · Updated July 22, 2026
A boiler heats your home by warming water and pumping it through a closed loop of radiators, baseboards, or in-floor tubing. The heat radiates into rooms without blowing air, which is why boiler homes feel steady and draft-free. Many older Georgetown and Acton homes — and most homes with cast-iron radiators — run on hydronic (water-based) heat.
What are the parts of a boiler system?
- The boiler burns natural gas or propane to heat water in a heat exchanger.
- The circulator pump pushes that hot water through the loop.
- Radiators, baseboards, or in-floor loops release heat into rooms.
- The expansion tank and pressure-relief valve manage the pressure that heated water creates — key safety components.
How is a boiler different from a furnace?
A furnace heats air and blows it through ducts; a boiler heats water and radiates warmth from fixed emitters. Boiler heat is quieter and doesn't stir up dust, but it can't share ductwork with central air conditioning — boiler homes usually cool with ductless mini-splits.
What goes wrong with boilers?
- Pressure loss from small leaks — the most common no-heat call.
- Airlocked radiators — cold at the top, warm at the bottom; they need bleeding.
- Failed circulator pumps — the boiler fires but heat never moves.
- Scale and sludge in older loops, which choke flow and efficiency.
Gas boiler work in Ontario must be done by a registered gas technician — Brooks Heating & Air is TSSA-registered and has serviced boilers across Halton Hills since 2009.
Next step: Weighing a tired boiler against a new one? Read the boiler replacement cost estimate guide, or book a boiler repair or maintenance visit with a TSSA-registered technician.
Frequently asked questions
How long does a boiler last?
Cast-iron boilers commonly run 20–30 years; high-efficiency condensing boilers typically 15–20 with annual service.
Why is my radiator cold at the top?
Trapped air. Bleeding the radiator usually fixes it; recurring air points to a system issue worth a service visit.
Can I add air conditioning to a boiler home?
Yes — most boiler homes add ductless mini-splits or a small ducted system, since there's no existing ductwork.
What pressure should my boiler show?
Most residential systems sit around 12–15 psi cold. Repeatedly dropping pressure means a leak — have it checked.
Does a boiler need annual maintenance?
Yes. An annual service checks combustion, safety controls, pressure, and the expansion tank — it's also usually a warranty condition.
Related reading: Boiler services in Georgetown & Halton Hills · Boiler maintenance tips for Acton homes · Central air vs ductless for older homes