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The most common indoor pollutants monitored in DCV systems are carbon dioxide and humidity. [1] This control strategy is mainly intended to reduce the energy used by heating, ventilation, and air conditioning (HVAC) systems compared to those of buildings that use open-loop controls with constant ventilation rates.
Humidity occurs in indoor environments due to building related causes. Porous walls, rising damp, and leaks in the building are determinants for structural dampness due to elevated humidity levels. [4]: 185–187 The construction of the building can also lead to humidity and unwanted moisture in the indoor environment. [15]
The control system can compare the temperature of the outside air vs. return air, or it can compare the enthalpy of the air, as is frequently done in climates where humidity is more of an issue. In both cases, the outside air must be less energetic than the return air for the system to enter the economizer mode.
Ventilation is mainly used to control indoor air quality by diluting and displacing indoor pollutants; it can also be used to control indoor temperature, humidity, and air motion to benefit thermal comfort, satisfaction with other aspects of the indoor environment, or other objectives.
Plumbing systems also service air distribution/control, and therefore contribute to the mechanical part of MEP. Plumbing for HVAC systems involves the transfer of coolant, pressurized air, water, and occasionally other substances. Ducting for air transfer may also be consider plumbing, but is generally installed by different tradespeople. [11]
Joseph Lstiburek (/ ˈ s t iː b r ɪ k /, pronounced STEE-brek) is a forensic engineer, building investigator, building science consultant, author, speaker and widely known expert on building moisture control, indoor air quality, and retro-fit of existing and historic buildings.
HVAC (Heating, Ventilation and Air Conditioning) equipment needs a control system to regulate the operation of a heating and/or air conditioning system. [1] Usually a sensing device is used to compare the actual state (e.g. temperature) with a target state. Then the control system draws a conclusion what action has to be taken (e.g. start the ...
By comparison, thermal comfort standard ASHRAE 55 requires systems designed to control humidity to maintain a dew point of 16.8 °C (62.2 °F) though no lower humidity limit is established. [44] Water vapor is a lighter gas than other gaseous components of air at the same temperature, so humid air will tend to rise by natural convection. This ...