Sustainable Building Technical Manual - Etn-presco.net

HVAC System Practices❑ Flush out newly constructed interior spaces prior to occupancy.Flushout of newly constructed spaces with fresh air (at as high a percentage as possibleor practical, with 100 percent as the goal) can effectively remove high levels of airbornecontaminants prior to occupancy. This activity should be coordinated with measuresto protect the HVAC distribution system (for example, the supply-air ductworkand air-handling equipment) so that contaminants are flushed out of the building andnot recirculated in the process, contaminating distribution systems and equipment aswell as other areas throughout the building (see Chapter 13, “Indoor Air Quality”).❑ Flush out occupied areas during off-hours.When occupancy schedules make flushout impractical, perform the procedure duringoff-hours (for example, weekends and evenings) for a period of time until contaminantlevels are reduced. Complete prior to scheduled occupancy.❑ Depressurize the construction work area.Keeping the construction area under negative pressure, especially in an occupied building,can help prevent airborne contaminants from migrating into occupied areas. Acombination of measures can depressurize the site, such as supplying ventilation intothe space under construction, using temporary or existing building exhaust systems tosiphon pressure out of the construction area, or supplying positive pressure to occupiedportions of the building.❑ Pressurize occupied areas.Maintaining occupied areas under positive pressure in relation to the space under construction(by ensuring that the air volume supplied to the occupied space is greaterthan that supplied to the area under construction) can prevent the migration of contaminantsfrom the construction area into occupied sections of the building.❑ Increase outside air.Increasing outside-air ratios in the air supply to a building dilutes airborne contaminantsinstead of recirculating them into the building. Increased ventilation, althoughan appropriate measure for reducing potential contaminants in indoor air, may not besufficient on its own and may have to be combined with other measures for effectiveIAQ mitigation.❑ Protect ventilation systems and components.A building’s ventilation system consists of three components: a supply-air distributionsystem, a return-air distribution system, and air-handling equipment, which also performsfiltration. The return-air system recirculates indoor air back through the air-handlingequipment and back into the building through the supply-air system. For thisreason, the return-air system in a construction area should not be used to exhaust thespace unless airborne contaminants are filtered prior to entering the return-air system.Sealing off return-air inlets and establishing alternative exhaust measures (such asremoving windows) that work in tandem with the building’s supply-air system to provideventilation can be an effective mitigation strategy. Care must be taken to ensurethat the construction space is kept under negative pressure relative to the occupiedportion of the building.(See Chapter 12, “HVAC, Electrical, and Plumbing Systems.”)Source-Control Practices❑ Use low-emission products.Concerns about indoor and ambient air quality have spurred the development of low-VOC-emission products. Consider low-emission products when they are cost-and-performance-effective;when a building under construction is partially occupied; andwhen the potential impact of higher-emission products on occupant health and safetyis a concern.