Because mechanical ventilation systems for schools are designed to bring in outdoor air, many buildings operate under a slight positive pressure and air leakage into the building is not a concern. If mechanical ventilation is not used, air infiltration will likely be uncontrolled and can result in significantly higher energy use. Where high humidities are present, uncontrolled air infiltration can be an even greater concern because moisture can move through building cavities, where it can be detrimental to the building's structural components and materials. Smaller school buildings may use unconditioned attic space as the return air path to the heating or cooling system. Routing of return air leads to substantial air infiltration, since return air plenums are depressurized and will suck in surrounding outside air if not sealed.
Some local codes require attics to be ventilated.
If this is the case, ensure that connection paths between vents and return air plenums are minimized or eliminated. Additional Resources For more information on window technologies, see DOE's fact sheet entitles, Advances in Glazing Materials for Windows and the Efficient Windows Collaborative's Web site. EnergySmart Schools is a campaign of Rebuild America .