How Your HVAC System Works

What Does HVAC Stand For?

HVAC stands for Heating, Ventilation, and Air Conditioning. It's the collective term for all the equipment that controls the temperature, humidity, and air quality inside your home. In Canada, a complete HVAC system typically includes a furnace or heat pump, an air conditioner or cooling coil, a ventilation system, and the ductwork that connects everything together.

Understanding how these components work — and how they work together — helps you maintain your system properly, recognize warning signs before they become expensive repairs, and make smarter decisions when it's time to upgrade.

A gas furnace burns natural gas to produce heat. The combustion happens inside a sealed heat exchanger — a metal chamber that gets very hot. Air from your home is blown across the outside of this heat exchanger, picks up the heat, and is distributed through your ductwork. The combustion gases (including carbon monoxide) stay sealed inside the exchanger and are vented safely outside through a flue pipe.

Modern high-efficiency furnaces (90%+ AFUE) extract so much heat from the combustion gases that the exhaust cools down enough to be vented through PVC plastic pipe rather than a metal chimney. The top-rated Lennox SLP99V achieves 99% AFUE — meaning 99 cents of every dollar of gas you burn becomes heat in your home.

Air conditioners don't create cold air — they move heat from inside your home to outside. The system uses a refrigerant that cycles between liquid and gas states to absorb heat indoors and release it outdoors. The indoor coil (evaporator) absorbs heat from your home's air; the outdoor unit (condenser) releases that heat outside.

The efficiency of an air conditioner is measured in SEER (Seasonal Energy Efficiency Ratio). A higher SEER means less electricity used per unit of cooling. Ontario's minimum standard is 13 SEER; premium units like the Lennox XC21 reach 21 SEER — cutting your cooling costs nearly in half compared to a minimum-efficiency unit.

A heat pump works like an air conditioner that can run in reverse. In summer it moves heat from inside to outside (cooling). In winter it extracts heat from outdoor air — even at very cold temperatures — and moves it inside. Modern cold-climate heat pumps like the Lennox XP21 operate efficiently down to -30°C, making them ideal for Canadian winters.

Because heat pumps move heat rather than generate it, they can deliver 2–3 units of heat energy for every 1 unit of electrical energy consumed. This makes them significantly more efficient than electric baseboard heaters and often more efficient than gas furnaces when electricity rates are reasonable.

Your ductwork is the circulatory system of your HVAC setup. Supply ducts carry conditioned air from the furnace or air handler to each room; return ducts bring air back to be reheated or cooled. The balance between supply and return air is critical — an imbalanced system creates pressure problems that reduce efficiency and comfort.

Leaky or poorly insulated ducts are one of the most common sources of energy waste in Canadian homes. Studies suggest that 20–30% of conditioned air can be lost through duct leaks in a typical home. Air balancing — measuring and adjusting airflow at each register — ensures every room gets the right amount of conditioned air.

Modern homes are built very tightly to conserve energy — which is great for efficiency but means stale air, humidity, and pollutants can build up indoors. A Heat Recovery Ventilator (HRV) solves this by continuously bringing in fresh outdoor air while recovering up to 80% of the heat from the outgoing stale air.

Whole-home humidifiers maintain healthy humidity levels (35–50% RH) during dry Ontario winters. Low humidity causes dry skin, static electricity, and makes your home feel colder than it actually is — meaning you turn up the heat and spend more. A properly humidified home at 20°C feels as warm as a dry home at 22°C.

Basic Maintenance Every Homeowner Should Do