Energy-efficient homes, both new and existing, require mechanical ventilation to maintain indoor air quality. There are four main types of mechanical ventilation systems for the whole house: exhaust, supply, balance, and energy recovery. Each system has its own advantages and disadvantages, and the best system for your home will depend on the climate and other factors. In this article, we'll discuss the special considerations for installing an energy-efficient ventilation system in Broward County, FL.
Exhaust ventilation systems work by depressurizing your home. The system expels air from the house, while replacement air is infiltrated through leaks in the building housing and through intentional and passive ventilation grilles. Exhaust ventilation systems are best suited for cold climates. In climates with hot, humid summers, depressurization can draw humid air into the cavities of building walls, where it can condense and cause moisture damage.
These contaminants are of particular concern when bathroom fans, stove fans, and clothes dryers (which also depressurize the house while they work) operate when an exhaust ventilation system is also in operation. Exhaust ventilation systems can also contribute to increased heating and cooling costs compared to energy recovery ventilation systems, since exhaust systems do not temper or remove moisture from replacement air before it enters the home. Supply ventilation systems use a fan to pressurize the house, which causes outside air to enter the building while air is filtered out of the building through holes in the housing, bathtub and stove fan ducts, and intentional ventilation grilles (if any). Like exhaust ventilation systems, supply ventilation systems are relatively simple and inexpensive to install. A typical supply ventilation system has a system of fans and ducts that introduce fresh air normally into one, but preferably several, rooms occupied by most residents (e.g., living room).
This system may include adjustable vents on windows or walls in other rooms. Supply ventilation systems allow better control of the air entering the house than exhaust ventilation systems. By pressurizing the house, supply ventilation systems minimize outdoor pollutants in the living space and prevent flue gases from being extracted from fireplaces and appliances. Supply ventilation also makes it possible to filter the outside air introduced into the house to remove pollen and dust or to dehumidify it to control humidity. Supply ventilation systems work best in warm or mixed climates.
Because they pressurize the home, these systems have the potential to cause humidity problems in cold climates. In winter, the supply ventilation system causes warm indoor air to filter through random openings in the outer wall and roof. If the indoor air is sufficiently humid, moisture can condense in the attic or on the cold outer parts of the outer wall, which can lead to mold and decay. Like exhaust ventilation systems, supply ventilation systems do not temper or remove moisture from replacement air before it enters the home. Therefore, they can contribute to increased heating and cooling costs compared to ventilation systems with energy recovery. Because air is introduced into the house in inconspicuous locations, it may be necessary to mix outdoor air with indoor air before delivery to avoid cold drafts in winter.
An in-line duct heater is another option, but it increases operating costs. Balanced ventilation systems, if properly designed and installed, do not pressurize or depressurize your home. Rather, they introduce and expel approximately equal amounts of fresh outdoor air and polluted indoor air. Some designs use a single-point escape. Because they directly supply outdoor air, balanced systems allow the use of filters to remove dust and pollen from outdoor air before it is introduced into the house.
Balanced ventilation systems are suitable for all climates. However, because they require two duct and fan systems, balanced ventilation systems are often more expensive to install and operate than supply or exhaust systems. Like supply and exhaust systems, balanced ventilation systems do not temper or remove moisture from replacement air before it enters the home. Therefore, they can contribute to increasing heating and cooling costs unlike ventilation systems with energy recovery. In addition, like supply ventilation systems, it may be necessary to mix outdoor air with indoor air before delivery to prevent cold drafts in winter. Ventilation systems with energy recovery provide a controlled way to ventilate a home while minimizing energy loss.
They reduce the costs of heating ventilated air in winter by transferring heat from warm indoor exhaust air to fresh (but cold) outdoor supply air. In summer, indoor air cools the hottest air supply to reduce cooling costs. Because an energy recovery ventilator transfers some of the moisture from the exhaust air to the incoming winter air which is usually less humid; this keeps humidity levels more constant. In summer an energy recovery ventilator can help control humidity in the house by transferring some of the water vapor from incoming air to outgoing air that is drier. If you use an air conditioner an energy recovery fan generally offers better humidity control than a heat recovery system; however there is some controversy over using a ventilation system during humid but not too hot summer days - some experts suggest that it's best to turn off the system in very humid climates to keep indoor humidity levels low. You can also set up your system so that it only works when your AC is running or use pre-cooling coils.
Most energy recovery ventilators can recover between 70% - 80% of energy from outgoing air and deliver that energy to incoming air; however they are more cost effective in climates with extreme winters or summers where fuel costs are high - in temperate climates additional electricity consumed by system fans can outweigh energy savings by not having to condition incoming air. Ventilation systems with energy recovery usually cost more than other types of ventilation systems; however simplicity is key when trying to save on installation costs - many times existing ducts can be used for multiple purposes which will save on installation costs as well as maintenance costs since complex systems require more maintenance as well as consume more electrical energy. For most homes looking for an energy-efficient solution for their mechanical ventilation needs in Broward County FL., an energy recovery system is likely their best option due its ability to reduce heating/cooling costs while maintaining good indoor air quality year round.