ASHRAE 62.2 Ventilation for Indoor Air Quality

The 2008 Energy Efficiency standards went into effect on January 1st 2010.  With this round of changes, ASHRAE 62.2 was incorporated into the code and made ventilation for indoor air quality mandatory for all new homes and additions 1000 sq.ft and up.  What is the reason behind this new requirement?  New homes are built tighter and people tend not to open their windows as much due to noise and for security reasons.  So the requirement to bring in fresh air, while this is not an energy saving measure, went into effect to ensure indoor air quality.

What are the options to bring in fresh air?
There are a number of ways to bring in fresh air into a home, mechanically speaking.  The three most common ways are:

1. Exhaust only with the use of bathroom exhaust fans (the simplest method).
2. Supply Ventilation with the use of an outside air duct and motorized damper system.
3. Combination Ventilation which can be done with an HRV or ERV tied into the main system or better yet, a dedicated system.

The top diagram shows what is generically called a combination system.  This device is typically an HRV (heat recover ventilator) or ERV (energy recovery ventilator)  It is a balanced system in that both air from the inside is exhausted out while fresh air from outside comes in.  There is a heat exchanger inside the box that “tempers” the incoming air.

The next diagram shows supply ventilation.  This is typically done by bringing an outside air duct into the return plenum of the mechanical system.  It has a motorized damper that adjust the amount of outside air coming into the system. Because it is adding outside air to the system, it will tend to “pressurize” the house where an exhaust only system will “depressurize” the house.

There are plus and minuses to each type of method.  Our intent here is to introduce you to the options available.