Residential Boiler

A residential boiler is essentially a tank that heats and stores water for your heating needs. The boiler provides radiant or hydronic heat for your home, house without using forced air. The result is a quieter, more efficient heating system that provides even heating. Because of this, boilers are gaining in popularity.

How a Residential Boiler Heats your Home


A typical residential boiler works by using natural gas to heat then circulate hot water throughout your home and back again. Depending on your heating system, this may be through radiators, baseboard units, or in-floor radiant tubing. The process repeats continually using the same water to maintain the temperature set on your thermostat.

Components of a Residential Boiler

AirPlus Canada works with three types of natural gas boilers

  • Mid Efficiency, floor standing boilers
  • High Efficiency, Condensing – Modulating – Floor Stand Boilers
  • High Efficiency, Condensing – Modulating – Wall Hung Boilers

All boilers have a tank where water is heated and/or stored. Hot water boilers rely on a pump to circulate the hot water through a central heating system. Steam boilers, on the other hand, rely on building pressure from the heated water to move the steam through the piping system to heat your home.

All boilers are also have a heat exchanger. The heat exchanger can be made of cast iron, copper, steel and alloy metals. The heat exchanger is what transfers or exchanges water from the flame where it was heated to the pipes that carry the water to the rest of the house.

In order to get the best efficiency out of your boiler, it is important to get the right size. Sometimes people think bigger is better, but either too big or too small will not give you the best efficiency. Considerations for boiler sizing are climate, house size, your central heating system and how weather tight your home is.
Boiler size is determined in part by a heat loss calculation, which is translated into the BTU (British Thermal Unit) output you need.

Residential boilers come in a variety of efficiencies. The two general types are standard efficiency and high efficiency.

  • Standard Efficiency Boiler: a boiler that has an AFUE (Annual Fuel Utilization Efficiency) of less than 85%
  • High Efficiency Boiler: a boiler that has an AFUE (Annual Fuel Utilization Efficiency) 85% or greater.

If you are considering replacing an old boiler, the AFUE for the old boiler is probably much lower than the current minimum standards.

A residential boiler can last over 20 plus years. A high efficiency boiler use less fuel, reducing energy costs on a yearly basis. While a high efficiency boiler costs more initially, the cost savings over a long period of time will offset the initial cost.

Boilers are generally vented through the chimney. This may also be called the flue. High efficiency boilers (90% AFUE or greater) are direct–vented to the outside, eliminating the need for a chimney.


The movement of water is key to the effectiveness of your boiler system. Boiler systems work on a loop, sending hot water out of the boiler, and receiving cooler water in return, ready to be heated and pumped throughout your home. Sufficient water head pressure is essential to ensuring maximum comfort levels and minimal operating costs. Many older homes that have been modified or renovated, where original piping and radiators have been removed or replaced have inadequate or unbalanced water pressure. If your hydronic heating system isn’t working – simply changing the boiler might not solve the problem. Ensure that you consider, and budget for, pump / plumbing fittings/ piping and radiator replacement as well. An AirPlus design engineer can help you avoid costly mistakes.