Impact of fresh air on whole building performance

Thermal comfort is the basis of building homes from the beginning, mainly to protect oneself from the harsh climate conditions outside. Today, buildings are advanced enough to control the ventilation of a building. In order to maintain that, fresh air is required for any HVAC system. Fresh air is the air outside as opposed to that within a room or other enclosed space.

Why is it important?

Fresh air is a necessity for both physical and mental health. But unfortunately most of us, due to living and working in confined areas, don’t get the optimal amount of fresh air needed.
In some buildings, if indoor air is recirculated, due to which impurities may be breathed in again and again which include indoor pollution, and higher level of carbon dioxide levels. This creates poor indoor air quality. To avoid this, fresh air is supplied as per the number of occupants and the area of the space. 

Ever wondered how much air a human requires per second?

Average Fresh air requirement per person per second is 8 litres! This is how much air we breathe!
If we don’t get this much fresh air, we may experience fatigue, drowsiness & dullness of mind.
You may have heard of Sick Building Syndrome (SBS). This refers to a number of ailments that occur as a result of exposure to harmful chemical toxins at a home or work building. The main conditions for experiencing Sick Building Syndrome are spending long periods of time in well-sealed, poorly ventilated buildings that contain indoor air toxins.

Fig. Reference building

Analysis

The following analysis is done to measure the impact of fresh air on energy consumption of the building which is represented by EPI (energy performance index). The unit of EPI is kwh/sq. m/year. An example building is taken here and modeled on eQuest with different input fresh air calculations. This building has a built-up area of 14655 sq. ft.

Fig. Graph showing relationship between EUI and fresh air

Fig. Graph showing relationship between Unmet hours and fresh air

Results

It can be seen through the analysis that min fresh air impacts the energy consumption of the building in a proportional sense. EUI increases with decrease in fresh air provided. But it also has an impact on unmet hours, which is the main implication on the thermal comfort of the building. Unmet hours increase with the decrease in fresh air.