Air leakage through building envelopes can cause condensation, mold growth and damage to building materials. It can increase heating and cooling loads, thereby increasing energy consumption and operating costs. In sufficient quantities, air leakage can compromise occupant comfort by creating drafts and allowing uncontrolled entry of dust and environmental pollutants into occupied space. These concerns are driving the development of government regulation and building code requirements for mandatory air barrier systems in commercial buildings. This paper reviews the mechanisms by which water vapor migrates through and condenses within the building envelope, and clarifies the difference between a vapor retarder and an air barrier. It summarizes design considerations for these systems and common reasons for failure.

Subject
Air pressure, Buildings, Barriers, Water, Materials, Insulation, Moisture, Diffusion, Walls, Leaks, Condensation, Vapors, Penetration
© 2003 Association for Materials Protection and Performance (AMPP). All rights reserved. This work is protected by both domestic and international copyright laws. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2003
Association for Materials Protection and Performance (AMPP)
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