Maintaining good indoor air quality in your Tallahassee home is important for the health and comfort of your family, and an effective home ventilation system contributes to this. Older homes that weren't built with energy efficiency in mind get enough natural ventilation from air leaks around doors and window, as well as through cracks between walls, floors and ceilings. But new, energy-efficient homes require mechanical ventilation systems to keep the right amount of fresh air moving through the home.
There are three popular methods for providing home ventilation: exhaust-only systems, supply-only systems and balanced systems. Each type of home ventilation system has advantages and disadvantages, so discuss your home-building or remodeling ideas with your HVAC contractor to plan the best solution for your situation. The following brief descriptions of the types of systems will help get you started.
Exhaust-Only Home Ventilation
An exhaust-only system uses exhaust fans to suck air out of your house. They create negative pressure inside your house which is balanced by air infiltration through air leaks in the building structure.
Low cost is the only real advantage to an exhaust-only system. Since you can ventilate your home using fans that have to be installed anyway, such as in bathrooms and in the kitchen, there's no additional cost involved.
There are several big disadvantages to the exhaust-only approach, though:
- You have no control over where the makeup air enters your house. If it comes in via leaks around doors and windows, you won't have any air quality issues with it, but if it's sucked in from the crawl space or from behind walls or the garage, you can be bringing polluted air into your home. Radon, mold and combustion gases from fuel-burning appliances or automobiles are all potential hazards from uncontrolled air infiltration.
- If you decide to cut your home energy losses by sealing air leaks, you may reduce air infiltration enough to prevent an exhaust-only ventilation system from working.
- Since you don't control the entry points of the makeup air, you also have no control over whether your whole house is adequately ventilated. Any rooms that don't contribute to the air infiltration will not adequate ventilation.
- Incoming air can't be filtered. The other types of ventilation systems, described below, have discreet air entry points so the quality of incoming air can be improved with filters. Exhaust-only systems might get makeup air from hundreds of small cracks and holes, so filtration is impossible.
A supply-only ventilation system uses a fan to blow air from outside into your house. This raises the pressure inside the building, and air flows out around doors and windows and through small openings in the building structure to balance the pressure. Supply-only systems have some advantages over exhaust-only systems:
- Incoming air can be filtered to improve indoor air quality.
- Contaminated air from the garage or utility room isn't sucked into your home.
- The supply air can be distributed throughout your home via ducts, ensuring good ventilation of every room.
- Supply-only systems can incorporate a dehumidifier, which is useful in our humid Florida climate.
Balanced Ventilation Systems
Balanced ventilation systems blow air into the house at the same time that air is being exhausted out of the house. Balanced systems offer many benefits:
- The source of incoming air is controlled.
- Incoming air can be filtered.
- Energy recovery ventilators (ERVs) or heat recovery ventilators (HRVs) can be included in a balanced ventilation system to reduce energy losses from the exchange of outside air with inside air.
- The supply and exhaust fans come on together and move the same amount of air, so a neutral pressure is maintained inside your home. This prevents the infiltration of noxious fumes from the garage or utility room and reduces the loss of conditioned air through air leaks in walls and around doors and windows.
Balanced systems as well as supply-only systems can use your existing heating and air conditioning ductwork, but there are good reasons to have separate ducts for ventilation. The heating and air conditioning blower is too large for the amount of air you need to move for effective ventilation, so a separate blower will improve system efficiency. You can design a ventilation system to work well with existing ductwork with the A/C or heat on, or with the A/C or heat off, but not for both situations.
For the design, installation and maintenance of an effective home ventilation system anywhere in the Tallahassee area, contact us at Air Control Heating & Cooling.
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