Ventilation is costly
Old mechanical systems provided minimal fresh outside air for the occupants of buildings. The sick building syndrome of the 70’s was caused to a great degree from not enough fresh air to flush out all the toxins. Nowadays, one of the key ingredients for a sustainable building design is providing adequate ventilation.
The American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE), which recommends standards for mechanical systems, uses the number of people in a room and the size of the room to determine the ventilation rate. For example, a 150-square foot office requires about 15-20 cubic feet of fresh air per minute. That’s a lot of fresh air.
Jared Bartell, a mechanical engineer at MODUS in Des Moines, says ventilation accounts for about 30% of the cost of heating and cooling a building. One of the reasons is during the summer the fresh air has to be dehumidified and during the winter heated.
The typical mechanical system provides fresh air to a space all day long even if it is unoccupied. If your building has areas such as conference rooms or other spaces not used all the time, you might think about investing in a CO2 sensor. The sensors measure the CO2 rate of the outside to the rate inside the room. When a higher level is sensed in the room the ventilation system kicks on. Therefore, you might have a situation where ventilation in a large room is not needed for days, resulting in quite an energy savings.
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