Green Schools Attributes for Health and Learning (2007) / Chapter Skim
Currently Skimming:
3 Building Envelope, Moisture Management, and Health
3 Building Envelope, Moisture Management, and Health
Pages 40-53
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 40... ...
It is generally accepted that more than 75 percent of all building envelope (foundation, walls, windows, roof) problems are caused by excess moisture.
|
From page 41... ...
The effects of excess moisture are manifested by mold, mildew, rotted wood, insect infestations, spalling of masonry, condensation on surfaces, stained finishes, peeling paint, and reduced service life of materials and systems.1 Typically, current green school guidelines address moisture management issues as they relate to the siting of a building (they discourage development on wetlands or below the 100-year floodplain) , the placement of drainage and irrigation systems to prevent water accumulation in or near buildings, keeping construction materials dry, and using walk-off mats and grills to prevent the buildup of snow and rain brought into a building by people.
|
From page 42... ...
has issued two reports on the association between excess moisture or dampness and mold growth on the one hand and respiratory illness in building occupants on the other: Clearing the Air: Asthma and Indoor Air Exposures (IOM, 2000) and Damp Indoor Spaces and Health (IOM, 2004)
|
From page 43... ...
(2003) reported on a birth cohort of 849 infants less than 1 year old who had at least one sister or brother with physiciandiagnosed asthma; they found that wheeze and persistent cough were associated with airborne concentrations of Penicillium and Cladosporium, two types of mold commonly found in indoor air samples.
|
From page 44... ...
Health effects from excess moisture are mediated by increased indoor organisms or by deteriorated building materials that produce bioaerosols, defined as contaminants that come from living organisms and are airborne. Health effects may arise from a wide variety of mechanisms, including direct irritation of the eye or respiratory mucosa, immunologic bacteria, direct inflammation induced by toxic effects of bacterial products such as endotoxin or by VOCs, immunologic sensitization and inflammation, and the direct effects of fungal exotoxins.
|
From page 45... ...
• Asthma symptoms in sensitized persons • Cough • Wheeze • Upper respiratory (nasal and throat) tract symptoms Limited or Suggestive Evidence of an Association: Evidence is suggestive of an association between the agent and the outcome but is limited because chance, bias, and confounding could not be ruled out with confidence.
|
From page 46... ...
Vapor diffusion. Bulk transport is the liquid flow of rain, snowmelt, or groundwater into a building envelope under the influence of pressure differences exerted by gravity, hydrostatic pressure, wind, or air pressure.
|
From page 47... ...
As air moves, so does the water vapor. Airborne moisture moves under the influence of air pressure differentials created by wind, mechanical equipment, and the stack effect.3 The relationship between air transport of moisture and heating, ventilation, and air-conditioning (HVAC)
|
From page 48... ...
Architects must incorporate design features to control the entry of large amounts of rain and ground water from the outside, block capillary transport through and within the structure, and prevent excessive transport of water vapor through air movement and vapor diffusion. Compounding the challenge, designers must concurrently provide a healthy indoor environment, minimize energy use, and control construction costs (Lstiburek and Carmody, 1994; Achenbach, 1994; Powell, 1994)
|
From page 49... ...
Since below-grade moisture is one of the most powerful sources of moisture in conditioned spaces, building dry foundation assemblies can be one of the most effective strategies used to control interior airborne moisture (Lstiburek and Carmody, 1994; ORNL, 1988; Christian, 1994)
|
From page 50... ...
• Control rain penetration into above-grade walls using rain screens, drainage planes, building papers, and appropriate placement of flashings.
|
From page 51... ...
• Construct building envelopes that can store water if they get wet and are able to dry if they get wet, as appropriate for the local climate. • Install thermal insulation in a position to control dew point locations in the building envelope when possible and as appropriate for climate and building assembly.
|
From page 52... ...
These include discouraging development on sites below the 100-year flood plain or in wetlands; keeping site irrigation to a minimum; designing all drainage systems and HVAC condensate drainage systems to prevent the accumulation of water under, in, or near buildings; using walk-off grills and mats to prevent the buildup of moisture from rain and snow brought in by occupants; keeping all construction materials dry and well ventilated; discarding materials that have been wet for more than 24 hours; and requiring a maintenance plan that specifies the staff time and materials that will be dedicated to HVAC, plumbing, and roof systems. FINDINGS AND RECOMMENDATIONS Finding 3a: There is sufficient scientific evidence to establish an association between excess moisture, dampness, and mold in buildings and adverse health outcomes, particularly asthma and respiratory symptoms, among children and adults.
|
From page 53... ...
Recommendation 3b: Research should be conducted on the moisture resistance and durability of materials used in school construction. Such research should also investigate other properties of these materials such as the generation of bioaerosols and indoor pollutants as well as the environmental impacts of producing and disposing of these materials.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.