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Why a Ventilation System?
All buildings require controlled mechanical ventilation, or the controlled, purposeful introduction of outdoor air to the conditioned space. Building intentionally leaky buildings and installing operable windows does not provide sufficient outside air in a consistent manner throughout the year.
Building enclosures must be “built tight and then ventilated right.” Why? Because before you can control air you must enclose it. Once you eliminate big holes it becomes easy to control air exchange between the inside and the outside.
With a tight building enclosure, both mechanical ventilation and pollutant source control are required to ensure that there is reasonable indoor air quality inside the house.
Balanced Ventilation Systems (HRVs & ERVs)
A balanced ventilation system has two fans: one bringing outside air into the building, and the other exhausting stale interior air, resulting in roughly balanced airflows. These systems do not significantly affect the pressure of the interior space with respect to outdoors.
In most balanced ventilation systems, heat—and sometimes moisture—are exchanged between the two airstreams, reducing the heating and cooling loads caused by outside ventilation air. These systems are known as HRVs (heat recovery ventilators) and ERVs (energy or enthalpy recovery ventilators). HRVs only exchange heat between the airstreams, while ERVs exchange both heat and moisture.
These systems can be configured in a variety of ways; the options have a range of installed costs, energy efficiency levels (due to fan energy and recovery efficiency), and effectiveness at distributing the ventilation air throughout the house. In addition, system configuration will depend on the presence or absence of a central air handler, which can be used to distribute ventilation air.