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