IAQ Feature Articles

CO2 “Demand-Controlled Ventilation” (DCV) and Intake Rate Control

What does the term “demand controlled ventilation” (DCV) mean?. Very simply, it is “any” method used to control ventilation that modifies intake rates based on changing “demand”. The intention is to control ventilation rates based on occupancy within a predefined space (assuming it varies over time). Because ventilation rates are normally associated with occupancy levels, we conclude that the “demand” for ventilation is due to a measured change in the occupancy level for the space.
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Controlling Mold Growth in Exterior Walls of Buildings by
Continuously Maintaining Positive Pressure Flow through
Dynamic Ventilation Strategies

Building pressure control is essential to assure acceptable indoor air quality in today’s buildings, especially in humid climates. Mold growth inside exterior walls can result in significant IAQ and health problems. Moisture is a prerequisite for microbial growth. Minimizing the infiltration of humid air into a building, where it could condense within the exterior walls, can reduce microbial activity.
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The REAL Costs of Poor Indoor Air Quality

The sad fact is that most building managers and mechanical design engineers ignore the potential for IAQ problems until they are in the middle of a crisis. Most feel that “lightning” will always strike someone else; that they have been using a particular design and/or components for “20 years”, without a problem of this nature; or that “if we have a problem, we can address it quickly and avoid significant damages”. They all sound familiar, akin to that list of “famous last
words”.
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Reduce IAQ Liability and Increase Profitability: Advantages for Architects, Engineers, and Building Owners

Verifying that ventilation rates meet the national Standard is cheap IAQ insurance and a smart investment. Since the middle1980s tighter building construction has dramatically reduced infiltration through the building envelope. Also during this period the increased use of variable air flow/volume (VAV) ventilation systems has unintentionally reduced the outside air distributed through the supply duct_1,2,3. Both of these factors have reduced the dilution rate for contaminants emitted from people and the building and have been a major factor in degrading indoor air quality (IAQ) to levels that are 100-1000 times more polluted than outside air₄. Since people typically spend 90% of their time indoors_5,6 IAQ has become a worldwide concern.
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One problem area that is a national concern and under the microscopes of many local communities is our school buildings' indoor environment. The physical environment where our children are expected to stretch their minds should be healthfully supportive and foster productivity in teaching as well as learning. It should never have been allowed to develop into a threat to the health and welfare of our children.
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