| Causes For Building Envelope Failures | | | | structural, architectural systems, as well as occupant |
| The majority of building envelope failures can be | | | | comfort and loading to ensure building performance. |
| attributed to water in one of its many forms (gas, liquid, | | | | The building envelope includes the foundation, walls, |
| solid). Water degradation can take the form of | | | | windows and doors, and roofs. |
| biological degradation, freeze/thaw cycling or frost | | | | Performance requirements for the building envelope |
| heave, condensation, high relative humidity (RH) levels, | | | | are:o Control heat flowo Control water vapor flowo |
| water ingress and absorption. Other environmental | | | | Provide strength and rigidityo Control light and |
| effects that are harmful to buildings are air, and its | | | | radiationo Be aesthetically pleasingo Be durableo |
| components (oxygen, nitrogen, carbon dioxide, sulfur | | | | Control air flowo Control rain penetrationo Control fireo |
| dioxide), wind, biological and ecological agents, | | | | Control noiseo Be economical |
| temperature and solar radiation. | | | | WHY DO BUILDINGS DETERIORATE?o Poor design |
| Differential service life is a particularly important subject | | | | and detailingo Lack of buildability in designo Lack of |
| because it relates to the premature removal of building | | | | knowledge of materials and components usedo Lack |
| components simply because they are part of a | | | | of maintenance and repairo Environmental effects |
| system comprised of components with varying | | | | including water related factors, biological contributors, |
| service lives. The component with the shortest life | | | | chemical contributorso Construction on contaminated |
| dictates the life span of the system as a whole. It is | | | | lando Inadequate drainageo Movements due to |
| important to harmonize the service life of system | | | | settlement or temperature changeso Normal wear and |
| components and ensure the accessibility of | | | | tear and users abuseo Poor construction workmanship |
| components for periodic maintenance, repair, and | | | | and inappropriate installation |
| replacement. | | | | Water related factors of deterioration to buildings may |
| Buildings are constructed to provide space for a | | | | take the largest toll on structures- Snow, rain, moisture, |
| function, and the functional requirements of a building | | | | internal condensation, and humidity. Biological factors |
| typically require that the enclosed environment be | | | | include fungi, bacteria, and insects. Chemical |
| controlled. The building envelope consists of those | | | | contributors may include oxidizing agents, i.e bleach, |
| parts of the building that separate the controlled indoor | | | | reducing agents, i.e. sulfides, acids, i.e. bird droppings, |
| environment from the uncontrolled outdoor | | | | bases, i.e lime, salts, i.e. chlorides, or even chemically |
| environment. The enclosure acts as an interactive | | | | neutral substances such as fat or oil. Solar radiation, air |
| system that requires integration with the heating, | | | | quality, freeze thaw effects and wind are other |
| ventilating, and air conditioning (HVAC) equipment, | | | | environmental contributors to building deterioration. |