Stating the obvious for all those who may not know, a furnace is a device that generates heat. Besides using a furnace at home for warmth, furnaces have industrial uses as well, such as making steel, smelting ores, fractional distillation or heat-treating materials.

Brief history

The Romans invented the furnace system centuries ago. Wood was fed to a fire, usually in the basement, which transferred the hot air through flues. This was in stone/brick houses, and was not a safe method of central heating as there were possibilities of a fire.

Early furnaces required fire to keep the heat constant, which was later replaced by coal. Around 1940, gas furnaces started emerging, which are still the most popular form of home heating systems. With the advancements in technology, electrical furnaces were introduced, which replaced gas furnaces during energy crisis.


There are 3 types of furnaces:

i. Single-stage: simplest in terms of technology, it has only one stage of operation, with lack of controllability. They pump the hottest air at the highest velocity, and are the noisiest of all types.

ii. Two-stage: Has two operational stages, which are full speed and half speed, which provide a better comfort level. They maintain the desired temperature in the house and are quieter.

iii. Modulating: Most efficient form, they are able to modulate the heat and air pressure nearly continuously, depending on the demand and temperature outside.

Efficiency rating

All modern furnaces display an AFUE rating, which is Annual Fuel Utilization Efficiency, which is represented in percentage. Clearly the higher the AFUE percentage, the more efficient your furnace is. For example, if your furnace AFUE is 90%, then that means 90% of the fuel you put into your furnace will convert to energy and the remaining 10% will escape through the chimney. There are furnaces that range from 75% AFUE to 98% AFUE. Besides the AFUE rating, there is also an Energy Star label, a government development program, which ranks appliances on how they deliver results without wasting energy and consuming as little as possible. An Energy Star label is denoted by a number of stars. The more stars your appliance has, the more efficiently it will run.

Life span

Your furnace can run for many years. Be sure to track the number of years that have passed, because after around 20 years, the efficiency starts to diminish. It’s a good time to start thinking about a replacement if your furnace is that old.

Rules and guidelines

To ensure safety of the public, local and state government bodies set up rules and guidelines for installing a furnace system. To avoid system malfunctions or any serious problems, like a fire or an explosion, ensure that you have your furnace system installed correctly by a professional contractor.

By products and waste

Most of the components of a furnace are recyclable. You can send back parts of your old furnace, such as scrap metal or defective steel sheets, to the manufacturer for them to be reformed.

Furnaces are used in almost all the houses in the northern regions of Canada, where the winters are unbearable. They help keeping you and your homes warm. It is nearly impossible to survive the freezing winter cold without a furnace.


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