1. A Ventilation Standard for Residential Structures
ASHRAE
Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings
A Ventilation Standard for Residential Structures

2. Intent of Standard Ventilation as a designed operating system
Whole house ventilation
Local exhaust
Source control
Increased outdoor air exchange
Controlled to reduce interior moisture
Applicability: Single and multi-family structures three stories or less.

3. Outdoor Air Requirements Cubic Feet per Minute (cfm)
Bedrooms:
0-1
2-3
4-5
6-7
>7
<1500 ft2 30 45 60 75 90
ft2
105
ft2
120
ft2
135
ft2
150
>7500 ft2
165
Assumes 1-2 people in first bedroom with 1/ea. additional bedroom.
If additional occupancy density expected: add 7.5 cfm/additional person

4. Accomplishing Ventilation
Mechanical Systems!
Exceptions
Climates with less than 4500 infiltration degree days)
e.g., Honolulu, Birmingham, Tucson, Las Vegas, San Francisco, Los Angeles, etc.
Homes with no central air and < 500 heating degree days
Not occupied more than 876 hours per year.

5. Previous Approaches: Infiltration of Outdoor Air From Interior Vacuums
Humid climates
Uncontrolled entry of humid exterior air
Condensation and mold on walls and shell cavities
All climates
Radon entry
Outdoor pollutants

6. Effect Of Fresh Air Make-Up Warm Climates
Previous
ASHRAE 62.2
A/C
Fan Unit
A/C
Fan Unit
Negative or
Neutral Pressure
Positive Pressure
Allows entry of pollutants and moisture from outdoors and from beneath foundation
Dilutes indoor pollutants and resists entry of outdoor and sub-grade pollutants

7. Cautions on Fresh Air Supply
Leak on supply duct can depressurize home and cause uncontrolled infiltration
Warm Climates
Air conditioner must have sufficient dehumidification capacity.
If ductwork is exterior it must be well maintained.
Inlets will need to be maintained
If screen on fresh air inlet is not cleaned, make-up air will decrease.

8. Exhaust Approach Recommended for Severe Cold Climates
Additional mechanical exhaust increases infiltration of cold, “dry” air.
If building pressurized, humid interior air could condense as it is forced through shell and cause moisture accumulation in wall cavities.
Can increase entry of soil gases (radon, VOCs)
Attention to combustion flues to avoid backdrafting.

9. System Elements Continuous or Controlled intermittent operation.
Occupant to have control over system
Warning labels on switches
Fans should be designed for quiet operation.
Air movement to be distributed through house to avoid stale zones or areas of negative pressure when exhaust systems operated.

10. ASHRAE
Can significantly help reduce indoor pollutants if properly applied and operated.
Maintenance and homeowner intervention are concerns.
Impact on radon measurement and mitigation protocols.
Application to existing homes?