The HVAC system is what keeps a home comfortable throughout the year. It keeps the home cool in the heat of summer and warm during the winter and makes sure that fresh air comes in and stale air is pushed out. HVAC is an acronym that stands for:
- Air conditioning
There are many ways to heat a home. The homeowner can choose from gas fueled, oil fueled, electric or heat pumps. Some people still heat their homes with wood or coal. The warmth is provided either by heated air or heated water.
In a hot air system, a blower pushes hot air through a supply plenum then into ducts that service most rooms in the house. Registers in the floors or walls connect to the ducts. They allow hot air to enter the rooms, and pull chilled air back to the furnace. These systems need filters to remove the dust from the air and humidifiers to add moisture to the air, which is not only hot but uncomfortably dry.
In a hot water system a pump or circulator forces hot water from a boiler and into pipes. The heat from the water comes out of radiators or convectors in the rooms while the cooled water returns to the boiler to be reheated and circulated again. Older houses only have one pipe loop for hot water systems, while new homes may have two or more. This allows the house to be zoned, which is more efficient and lowers the homeowner’s heating bills.
Heat pumps use the energy of the air or the ground to heat a home. This surprises some people since the outside air seems cold to them, but 40 degrees Fahrenheit is toasty compared to outer space, for example. In the winter, the heat pump is able to take heat from the air, and use it to warm the house. The drawback is if the temperature dips to about 35 degrees F, the system switches to electricity. This makes it less efficient. Because of this, heat pumps are more appropriate for warmer climates.
Like the people, pets and even plants who live in it, houses need to be able to breathe. This is important because when the house breathes out it takes away a lot of mold-causing humid air with it. This is where the ventilation system comes in.
There are even more ways to ventilate a home than to heat it. One way, which has worked for thousands of years, is to open the doors and windows. Other ways that ventilate a house are roof vents, including vents in the gables and the ridges; appliance vents; fan vents in bathrooms, and vents in the eaves and foundations. Duct vents connected to the clothes dryer and cooling and heating systems also take stale, moist air out of the house. Most of these vents can be helped by a whole house fan located in the attic. In some houses, the whole house fan not only ventilates the rooms but can take the place of the air conditioner.
Cooling the house down in the summer can be done through room unit air conditioners, central air conditioners or heat pumps. These systems work by removing heat from the air as opposed to adding cold. They all have an evaporator and a condenser coil. Sometimes the evaporator is near the furnace, but the condenser needs to be outside. This is why room units fit in a window.
In an air conditioner or heat pup, warm air is pulled into the system and cooling coils filled with refrigerant absorb its heat. This heat is returned to the outdoor condenser and expelled. The cooled air comes into the rooms through the same registers and vents that deliver heat in the winter.
The power of an air conditioner is expressed in BTUs, or British thermal units. This is the energy that’s needed to raise the temperature of a pound of water 1 degree F. The more BTUs the air conditioner has, the more powerful it is. In order to comfortably cool down a house during the hot months, a homeowner needs to consult with an HVAC specialist to learn how many BTUs their home needs. Too few BTUs won’t cool down the house, and too many wastes energy.