| You should give serious consideration to installing a | | | | to get its combustion air from the interior of the |
| high efficiency furnace due to increase comfort | | | | home. Have the furnace intake piped to the |
| and energy savings. The most common used | | | | exterior of the home. This can only be done with |
| heating system for a residential home is a | | | | the 90% or higher efficiency furnaces. Otherwise |
| forced-air natural gas furnace which distributes | | | | you will be removing indoor air every time the |
| warm air through a duct system. Some other | | | | furnace operates and creating negative pressure |
| fuels that can be used for combustion are | | | | inside the home. |
| propane (LPG which is liquefied petroleum gas), | | | | A high efficiency furnace is also known as a |
| fuel oil, coal or wood. There are also electric | | | | condensing furnace since water is condensed in |
| furnaces which use electric resistance heaters; | | | | the flue gases when most of the heat has been |
| however these have much higher energy costs | | | | removed from them. This condensate will have to |
| to heat your home. | | | | be drained to the exterior by gravity or be |
| A combustion furnace will always need to be | | | | pumped. It can share the same drain as the A/C |
| vented to the exterior of the home. This is | | | | condensate drain assuming it is contains a proper |
| needed since the flue gases could contain carbon | | | | trap. A high efficiency furnace typically has a dual |
| monoxide (a deadly gas). Furnaces used to vent | | | | stage burner and a multi-speed or a variable |
| up a chimney that was built up through the roof, | | | | speed blower, which increases its efficiency and |
| however a high efficiency furnace can be vented | | | | comfort in the home. |
| out a plastic pipe since so little heat is lost through | | | | Any home furnace works basically the same way. |
| the flue gases. A furnaces efficiency, also known | | | | The fuel (gas, propane, oil, etc) is ignited/burned |
| as it's AFUE (Annual Fuel Utilization Efficiency) is | | | | which creates the heat, this heat (the combustion |
| measured by its ability to convert its fuel to | | | | gases) pass through a heat exchanger (except |
| usable heat for the home. The minimum efficiency | | | | for electric heat), then to the exterior and the |
| rating for furnaces today is 78% AFUE (which | | | | blower passes the air from your home across this |
| means 78% of the heat is transferred into the | | | | heat exchanger transferring the heat into the air, |
| home and only 22% is lost through its exhaust) | | | | then blows this air back into your home at a |
| and then the high efficiency models are 90% & | | | | warmer temperature. The typical temperature |
| higher with an efficiency rating as high as 98% | | | | rise of a modern gas furnace is 30F to 50F. This |
| (only a 2% loss!!!). | | | | means if the indoor temperature is 70F, then the |
| Important tip: For maximum efficiency and | | | | air blowing out of your supply registers in the |
| comfort in your home, do NOT allow the furnace | | | | home will be 100F to 120F. |