Fresh air is hopefully just beyond the walls and windows of your home. With a crack of a window, the air pressure in the room changes and the fresh outdoor roles in, and the dusty old air floats out.
However, not everyone lives in a clean environment, and not everyone likes to let hot or cold air into their home. In fact, new energy code regulations such as the 2021 International Energy Conservation Code, requires home alterations and new construction to be air-tight to a high standard that will require an entirely new mechanical system that brings fresh air into your home. These types of mechanical systems are known as 'ERVs' and HRV's- 'energy/ heat recovery ventilators'. The system is a type of fan that takes existing air in your home, and pulls old air through a honey-comb shaped filter, and then pulls outdoor air into the filter to recapture ~90% of the heat/ coolth. With the outdoor air now matching the interior temperature of your home via a free exchange of energy within the filter, the air gets re-delivered to the rooms of the home through an independent ducting system, or through the existing ducting.
Here is a simple example of the heat exchange mechanism:
How does this deliver fresh air to the home? While the requirements for a single-family home and a multifamily building are a little different, we will cover single family homes. According to Massachusetts building code, ventilation must follow one of three standards:
N1103.6 (R403.6) Mechanical Ventilation (Mandatory). Each dwelling unit of a residential building shall be provided with continuously operating exhaust, supply or balanced mechanical ventilation that has been site verified to meet a minimum airflow per:
1. Energy Star Homes’ Version 3.1;
2. ASHRAE 62.2-2013; or
3. the following formula for one- and two-family dwellings and townhouses of three or less stories above grade plane: Q = .03 x CFA + 7.5 x (Nbr +1) - 0.052 x Q50 x S x WSF
In this diagram we see a strategic locations of vents near bedrooms and living rooms central to the home helps evenly distribute the fresh air throughout the single 'dwelling unit'.
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