Every building has heating, ventilation, and air conditioning (HVAC) needs, whether it is a home, office, or warehouse. Mechanical design is primarily concerned with the HVAC and ductwork design in the building, however it is also about air quality, energy efficiency, and moisture management.
The Basics of Mechanical Design
A mechanical designer will first determine the size of the space to be heated or cooled. They will then look at how the space will be used and determine how often the air must be recirculated to maintain the correct temperature, humidity, and freshness for comfort. Finally, they will choose the appropriate heating source, cooling equipment, and ductwork layout for the building, all with the purpose of ensuring occupant comfort.
Occupant comfort can be greatly affected by the air quality in the space. Many individuals have likely experienced having gone to a lecture or performance where air circulation was poor which caused them to get sleepy. The sleepiness is a result of carbon dioxide not being effectively removed from the space. An effectively designed HVAC system will have the proper amount of fresh air to dilute contaminants, like carbon dioxide, from the air. Controlling the amount of fresh air is crucial to all building types.
Mechanical designers may also be required to do design for more specialized spaces like surgical suites or science labs. The designers must understand the specific purpose and use of the space in order to ensure the proper air conditions and quality that will keep everyone safe.
The HVAC system has a large impact on the energy efficiency of a building. Yes, you can buy equipment that is energy efficient, however, the entire system should be optimized. This means that the energy requirements of the building must be considered on a whole to ensure that there are no hot or cold spots within the building. Things to consider include, but are not limited to: the amount of sun exposure, sources of internal heating sources, and sources of high amounts of heat loss or gain. All of these must be taken into consideration in order to effectively zone the building and provide the appropriate levels of heating and cooling to each zone. Effective division of the heating and cooling requirements can lead to a reduction in the energy requirements for the building as a whole, while ensuring occupant comfort.
Air carries moisture. The moisture in the air, commonly referred to as the humidity, must be controlled; if it is too dry or too humid the occupants will not be comfortable. Moisture in the air inside a building can also cause problems with the integrity of the building if there are any inefficiencies within the building envelope.
Moisture wants to move from areas of high concentration to areas of low concentration. This means that on a cold dry winter day, the moisture from inside a home is trying to move towards the outside. If the moisture can enter the wall assembly, and if any component of the wall assembly is poorly protected against the cold, the dewpoint temperature may be reached, leading to moisture condensation. If there is condensation which is unable to dry effectively then mould growth can occur.
Since building envelope inefficiencies unfortunately do occur it is important to ensure proper moisture control to reduce the possibility of condensation, and good ventilation to ensure that if condensation does occur it has the ability to dry completely.