DIY Network

Keeping Your Home Toasty

In a centralized forced-air system, heat is generated by an air-handling unit and is pushed through the ductwork and into rooms.

Have you ever experienced, in your own home or one you're considering buying, that in winter it's hot on upper floors and chilly on the first floor? You might be surprised to learn that there's no one heating system that can be installed in all homes and perform equally well. Since every house is different, each heating system needs to be designed to take into account the individual characteristics of a particular house. This includes how it will affect or be affected by other systems in the home (for example, your heating system may work wonders but be all for naught if the heat it produces is sucked out of the home through poor-performing windows).

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	A furnace is the most common type of AHU.
	An alternate type of AHU is a heat pump, which is used mainly in hot climates.
	A radiant system provides heating in the flooring.

If you're building a home, it's important that you understand how a heating system works so that you can talk with your builder about your options, and together choose the best system for your home.

Heating is part of a home's mechanical system, commonly known as the HVAC (heating, ventilating and air conditioning) system. This article focuses on the heating component.

You can use a number of different systems to heat a home. The most prevalent is centralized forced air. In a forced-air system, heat is generated at a central point in the home, typically in the basement or the lowest floor, by an air-handling unit (AHU). Fans in the unit push air over hot coils and then through ducts that run inside your walls and under your floors. Ducts are passageways, usually tubular and made from either sheet metal, flexible material or rigid insulation, that deliver air from the AHU throughout the home and also return air from the rooms back into the AHU for re-circulation. Finally, the air is delivered into rooms through supply vents at the ends of ducts, which are openings to a room, typically in the wall, floor or ceiling. Return vents pull stale air back to the system through a separate series of ducts. If you put your hand in front of a vent and don't feel air coming out, that vent is a return vent. Returned air is drawn through an air filter before going back into the AHU, where it's heated and forced back through the home.

• A common type of AHU used for forced-air heating is a furnace. A furnace uses gas, electric or oil to create heat.

• Alternate types of AHUs are hydronic systems, which use the home's hot water to heat the air; radiant heating, which heats the floor; and heat pumps. This article doesn't explain these systems in depth, so if you're interested in learning more, be sure to ask your builder about alternate types of AHUs.

• Regardless of the type of AHU, the heating system must be the right size for your home so it uses less energy and keeps your utility costs under control. Proper sizing is also key to good humidity control in the summer and uniform temperatures year-round. To ensure the HVAC system is properly sized, a mechanical engineer or HVAC designer should perform an engineered analysis according to industry standards, such the Air Conditioning Contractors of America's (ACCA) Manual J.

• Also, the heating system must be installed correctly to exhaust fumes and gases to the outdoors. HVAC installers should carefully follow the system manufacturer's guidelines for installation.

• The heating system also must be in the right location. As a best practice, the AHU should not be placed in unconditioned space (meaning space that doesn't receive heated or cooled air), whether in an attic, crawl space or basement. Why? Think about how hot or cold your attic gets. When an AHU is located there, it's subject to those extreme temperatures; operating in such conditions will negatively affect its performance.

Don't wait until the mechanicals stage of construction, when the HVAC system is being installed, to give input on your heating system and to discuss your options with your builder. (The mechanicals are typically installed about 12 to 13 weeks into the construction process -- click here for more information on the stages of construction.)

An HVAC system that provides the right amount of heat for each room to keep you comfortable, and that operates efficiently, needs to be designed well before construction starts. If you're having your home built, make sure you discuss this with your builder as early as you can. Be sure to ask the following:

• Is the system sized according to ACCA's Manual J?

• Is the system located in conditioned space?

• Will there be quality-control checks on the installation.

RESOURCES :

For more information on the topics contained within this article please reference The U.S. Department of Energy's (DOE's) Building America Program

The Building America program works with members of the home-building industry to produce quality homes that use less energy without costing more to build.

Website: www.eere.energy.gov/buildings/building_america/