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Lighting Seattle since 1905 Jorge Carrasco, Superintendent
Conservation: Be Smart & Build Smart
Built Smart Users Manual: Specifications Chapter 5:
Indoor Air Quality
Built Smart Users Manual | Specifications | Alerts | Water

This chapter applies to all buildings, not just those receiving the optional efficient fan incentives. All BUILT SMART residences shall meet the Washington State Ventilation and Indoor Air Quality (VIAQ) code, latest edition. Much of the information below comes directly from the VIAQ code. For complete code requirements, and in case of conflict between these documents, please refer to the VIAQ code at

5.1 Whole-House Exhaust Airflow - Prescriptive Path
Residential buildings of four stories or fewer shall meet the current minimum and maximum fan flow requirements described in the appropriate chart below. For taller buildings please see the State VIAQ code.

5.1.1 Intermittent Ventilation
Unit Square Footage # Bedrooms Min/Max Fan Flow at 0.25 in W.G.
Less than 500 2 or fewer 50-75 cfm
501 - 1000 2 or fewer 55-83 cfm
1001 - 1500 2 or fewer 60-90 cfm
501 - 1000 3 70-105 cfm
1001 - 1500 3 75-113 cfm

5.1.2 Continuous Ventilation
# Bedrooms/ Residence Min. Fan Flow at 0.25 in W.G. Max. Fan Flow at 0.25 in W.G.
1 30 cfm 60 cfm
2 50 cfm 75 cfm
3 60 cfm 90 cfm
NOTE: A single, continuously operating, integrated whole-house fan or fan pickup in one bathroom is acceptable if spot ventilation fans are provided in the kitchen and in the other bathrooms.

5.2 Whole-House Exhaust Airflow - Calculated Path
Whole-house ventilation systems not meeting the prescriptive path shall be calculated for exhaust airflow. The minimum combined measured airflow capacity shall be 0.35 ACH, but not less than 15 cfm per bedroom and 15 cfm for main living area. The maximum ventilation rate for non-heat recovery ventilation systems shall not exceed 0.5 ACH for residences greater than 1400 square feet or 0.65 ACH for residences less than 1400 square feet.

5.3 Whole-House Exhaust Fan Controls
Intermittently operating, whole-house exhaust fans shall have both automatic and manual controls. Automatic controls shall include time clock or cycle timers with a minimum of three on/off periods per day and be set to provide at least 8 hours of mechanical ventilation per day. Control pins shall not be removable.

5.4 Individual Room Outdoor Air Inlets
All residential units shall have a minimum of two outdoor air inlets provided in the living/dining areas. Each bedroom shall have one outdoor air inlet.

5.5 Formaldehyde Reduction Measures
All structural components such as softwood plywood, particle board, wafer board and OSB shall be identified as :"EXPOSURE 1", "EXTERIOR", or "HUD-Approved".

Interested in BUILT SMART incentives?
Contact an Energy Advisor at
or call (206) 684-3800.

Contact an Energy Advisor at
or call (206) 684-3800

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