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

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

Outdoor Air Requirements Cubic Feet per Minute (cfm) Bedrooms: >7 <1500 ft ft ft ft ft >7500 ft Assumes 1-2 people in first bedroom with 1/ea. additional bedroom. If additional occupancy density expected: add 7.5 cfm/additional person

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

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

Effect Of Fresh Air Make-Up Warm Climates A/C Fan Unit A/C Fan Unit Previous ASHRAE 62.2 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

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

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

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

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