Heating and Cooling

Space heating

In Canada’s commercial sector, natural gas provides 80.3 per cent of the energy used in space heating. Petroleum-based sources provide 13.7 per cent, electricity 5.9 per cent, and steam 0.1 per cent.

Common systems in Canada

Boilers are among the most common heat sources in Canada’s commercial and industrial buildings. They burn oil or gas, or use electric resistance coils to produce hot water or steam, which is circulated through the building via water-to-air or water-to-water heat exchangers. Large buildings often require more than one boiler to provide adequate heat generation; in some cases, a number of boilers are kept together in a central heating plant.

Baseboard heaters and electric resistance coils within a ventilation system are varieties of the electric heating coils system of commercial space heating. The system uses a process called electric resistance to heat a room. Inside each baseboard are electric cables that heat the air passing through. As the air is heated, it rises from the top of the heater and colder air is pulled into the baseboard from the bottom. This cycle continues until the air entering the heater reaches the temperature specified by a centralized thermostat.

Heat pumps typically upgrade energy from a source – usually waste heat from industrial processes or from the ground itself – to a temperature appropriate for heating a building. A heat pump system includes a refrigerant that passes continuously over an evaporator, a compressor, an expansion valve and a condensor. At the start of the evaporation cycle, the refrigerant is a low-pressure, low-temperature liquid that passes through a heat exchanger where it absorbs heat from outdoor air and vapourizes. The vapour is compressed, causing its volume to decrease and its temperature to increase, after which it passes through another heat exchanger where it gives off heat to indoor air and condenses into a liquid. The liquid passes through an expansion valve, which reduces its pressure, and the cycle begins again.

New space heating technologies

Cogeneration, which is the simultaneous production of thermal and electrical energy from the same fuel source, offers a new suite of technologies for commercial space heating. Most engines used in space heating convert only about 30 per cent of fuel energy into mechanical energy, with the remaining 70 per cent of energy wasted as heat in the engine exhaust or through engine walls. Cogeneration uses a heat-recovery system incorporating reciprocating engines, steam or gas turbines to produce additional steam or hot water that may be used to heat space.

Energy Management Control Systems (EMCS) incorporate a sophisticated system of computers, sensors and communications links that monitors energy usage within a building at all times. An EMCS is designed to automatically control temperature and humidity in a building, and to turn off heating equipment temporarily during lower load conditions (i.e., late night/early morning hours when commercial buildings are usually unoccupied.)

Properly managed, solar heat can reduce annual space heating costs up to 24 per cent. New technologies to collect solar energy have proliferated in recent years. In commercial properties, the most common way to collect passive solar heat is through advanced windows. Advanced windows use double or triple glazing, argon or krypton gas fills, insulated frames and special coatings to allow sunlight in and keep heat from escaping. This technology is especially effective when used on the south side of buildings. Solar collectors may be used to preheat ventilation air drawn from outside a building. This form of solar heating incorporates a glazed panel, a heat transfer circuit and a storage system including a heat exchanger. Using solar energy to preheat the air reduces or eliminates the cost of heating the air once inside the building. Photovoltaic systems use solar cells or solar photovoltaic arrays to convert solar energy into electricity for heating. An array can be added to the roof or walls of a commercial building, or retrofitted into existing buildings. The solar photovoltaic system at Nunavut Arctic College in Iqaluit, Nunavut generates approximately 2,000 ± 200 kWh of electricity each year. Radiant floor heating is a new technology that uses a highly efficient condensing natural gas boiler as its energy source, distributing the resulting heat through pipes encased in the building’s concrete and brick slabs.