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Heating, Ventilation and Air Conditioning: An Overview

A house is just like its owner: It needs to be heated, cooled, maintained at a comfortable constant temperature, surrounded by fresh air, and kept at a humidity level that is safe and comfortable for the building and its contents. The heating, ventilation and air conditioning (hvac) systems in a home are responsible for all of these conditions, so understanding how they function and work together will help you plan for an efficient, reliable, safe, and comfortable home heating and cooling system.

Heat Is What You Make It
Making heat, distributing it and controlling it are all closely intertwined. These three areas relate directly to the furnace or boiler and its fuel, the ducts, pipes or fans that carry the heat, and how the furnace delivers or witholds that heat. Research is essential to any hvac project, whether you’re thinking of adding heat, assessing the overall effectiveness and efficiency of your system, providing necessary ventilation, or making product selections to enhance your existing system or create a new one.

Adding On the Right Way

Choosing Your Heat Source

When your are choosing a fuel source for your home heating system, start with available fuels in your region, because not all fuels are available everywhere and some are cleaner and more efficient than others. Based on your chosen fuel—natural gas, fuel oil, light propane gas, and kerosene are the most common— you can figure out how much heat a gallon will give you and how efficient that fuel is likely to be. Called the standard heat value, the amount of heat a fuel can produce per gallon or cubic foot is measured and reported in Btu (British termal units). The higher the Btu produced, the more efficiently the fuel burns and the greater its heat value. Fuel oil, for example, has a heat value of 135,000 Btu/gal., while liquid propane gas produces 91,000 Btu/gal. Next you need to plug that information into the furnace selected. How many Btu/hour the furnace or boiler releases determines its output and will help to decide how much furnace you need to heat your space to the desired temperature. This is how the pros size and evaluate your heating needs. Following these formulas, you can plot out your energy usage, optimal furnace size, and desired output, too.

On the home front, consider where the heat source will be located, the space to be heated, and the distribution pathways you will use. You may use metal duct to supply forced air, copper pipe or PEX for hot water heat, fans for heat distribution, additional heaters for supplemental heat. Keep in mind that the space required to install or deliver hot water heat varies dramatically from that which is needed for forced hot air. Also, while adding a duct run in a wall or to a nearby addition may be easier, it is less space conscious than adding a stand-alone room heater for that new study. Adding a radiant panel to warm a bathroom or guest room may be simpler than retaining the old radiator or adding baseboard heat. These are all considerations when adding to an existing system, so you need to ask whether it is wisest to extend the existing system or supplement with a more energy- and space-efficient mode of heat.

Noise, soot, and byproducts of different heating systems need to be taken into account, too. Given your specific requirements, some heating options will be cleaner and more versatile than others. So remember to look at everything, including projected heating needs such as spas, pools, walkways or drives. Installation costs, space requirements, and operational demands of the system will help you compare your options, old and new.

A House Needs Air
Once heat has been created, it needs to be vented. Some furnaces pull the air they need directly from the house; others have a direct vent to the outside. Which option you choose and to what degree ventilation is required will further define your heating options. A new, energy-efficient home is tighter than an older, drafty house, but that’s not always a plus. The tighter the house, the more critical the need for ventilation. The furnace needs air to function; the house needs air exchanges to provide fresh, clean air for the family; the walls, attic and furnishings need moisture kept under control. All of these concerns center on ventilation which is linked to heating. The two systems can and should function together, but you must plan for it and keep ventilation concerns in mind at all times.

Keeping Cool
In some regions, cooling is actually more important than heating. In addition to traditional air conditioning units, hybrid heating and cooling systems provide efficient answers to heating and cooling needs. Alternative sources such as geothermal pumps, which use stored underground heat or cool air, are viable options in many areas of the country. Active and passive solar systems can also be used to power or supplement heating and cooling needs. Finally, never overlook the interplay of building materials, windows, doors, and the siting of the house itself; they complete the heating and cooling picture of every home.

Credit: Renovate Your World