Indoor Air Quality & Ventilation
With houses and buildings being built as tightly as possible, we are plagued by unbalanced ventilation systems. This means we can have positive air pressure caused by exhausted air not being ventilated as fast as supply air comes in. Or, vice versa. There can be negative pressure with supply air not being brought in as fast as air is exhausted. This leads to too much moisture in the home or building and increased loads on the heating and cooling system. Poor ventilation can also cause unpleasant odors and buildup of contaminants such as radon, formaldehyde, and VOCs.
ASHRAE 62.2 Standard (2013)
Ventilation is very important in an energy-efficient home. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has established the 62.2 standard which applies to all residential spaces that are "intended for human occupancy" in single family homes and multi-family structures up to three stories. These spaces include living rooms, bedrooms, kitchens, bathrooms, hallways, closets, store rooms, laundry rooms, garages, and basements. There are two components of the ASHRAE 62.2 standard that relate to ventilation fans: Whole Building Ventilation & Local Exhaust.
A local mechanical exhaust system shall be installed in each kitchen and bathroom:
- Kitchens: 100 CFM intermittent or 5 ACH continuous (based on kitchen volume)
- Bathrooms: 50 CFM intermittent or 20 CFM continuous
Each local exhaust fan counts towards meeting the ASHRAE 62.2 Whole Building Requirement.
Whole Building Ventilation
The 62.2 Standard (2013) Whole Building Ventilation requires that a home's living area should be ventilated at a CFM rate determined by adding 1% of the conditioned space floor area to 7.5 times the number of bedrooms plus one [formula: minimum required CFM = 0.01A + 7.5 (# bedrooms + 1)]. Mechanical ventilation is required in tight homes to meet the minimum CFM requirement. Use our CFM calculator to determine your minimum required CFM.