The design stage of a construction project is a chance to improve performance for the entire life cycle of the building. Projects are often designed to only meet the minimum requirements in local building codes. However, a design that exceeds codes can have an excellent return on investment. In the case of HVAC systems, a good design translates into energy savings and a better indoor environment.
Office buildings are used for business activity, and occupants can complete their tasks more efficiently if they are comfortable. Some key factors that influence comfort are air quality, indoor temperature, air speed and lighting quality. Note that their impact goes beyond comfort, since they also affect human health. Since the systems that control indoor environments are designed by MEP engineers, working with a qualified design firm pays off.
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The WELL Building Standard is a certification system like LEED, and it focuses on human health and well-being, as its name implies. The WELL scoring system gives high importance to factors like air quality, thermal comfort and acoustics.
Finding the Right Indoor Air Temperature
Subjective factors come into play when dealing with human comfort. A temperature that feels comfortable for one person may feel too hot or too cold for someone else. For this reason, the challenge is achieving an indoor temperature that is comfortable for as many people as possible.
Research organizations like Lawrence Berkeley National Laboratory (LBNL) and the Finnish Institute of Occupational Health have studied how indoor temperature influences productivity:
- The results vary depending on the study, but human productivity tends to peak within a temperature range of 21°C to 25°C (70°F to 77°F).
- A detrimental effect on office productivity has been observed with low thermostat settings like 17°C (62°F), and also high settings like 30°C (86°F). Productivity losses of 5% to 7% have been observed in these cases.
- In general, women tend to be affected more by low temperatures, while men are more susceptible to high temperatures.
Based on these results, an HVAC system that keeps the temperature within the optimal range is a lucrative investment. To achieve this, heating and cooling loads must be calculated accurately, and the corresponding equipment must be specified with the right capacity. Also consider that HVAC systems have many possible configurations, and the design must be suitable for the conditions found in the building.
While it is possible to be productive in offices that are cold or hot, doing so requires more effort. If the same task is performed with comfortable and uncomfortable temperatures, it may be perceived as more difficult in the second case, while causing more mental fatigue.
The WELL scoring system offers points for designing buildings with temperature variations. That way, occupants can sit where they feel comfortable, instead of having the same temperature for everyone. Building owners can also earn WELL points by adding localized temperature controls for occupants.
Importance of Indoor Air Quality and Air Velocity
According to the US Environmental Protection Agency, humans in urban locations spend 90% of their time indoors. To make building interiors comfortable and healthy, conserving air quality is very important. Carbon dioxide tends to get the most attention, but there are other substances that become dangerous at much lower concentrations. For example, particulate matter (PM) and volatile organic compounds (VOC) have been linked with many health issues.
Air pollutants with strong odors cause discomfort, but the sense of smell is unreliable when dealing with air quality. Many harmful substances are odorless, and some VOCs have smells that are considered pleasant. Air pollutants cause respiratory irritation even if they cannot be smelled, and asthma patients may suffer flare-ups.
Controlling air velocity is also important: a drafty environment can cause discomfort and health problems, even if air quality is kept under control. Air velocity issues are often caused by oversized or poorly controlled fans, or by using air ducts of incorrect sizes. The WELL scoring system offers points for using radiant HVAC systems, which use the natural convection of air to deliver heating or cooling.
A well-designed HVAC system is energy efficient, while conserving an indoor environment that keeps occupants comfortable and healthy. In office buildings, a good HVAC design can also improve productivity, while helping occupants feel better at work.
Temperature preferences vary, but building owners should aim for a temperature that is considered comfortable for most occupants. Research results have found that human productivity tends to peak in the range of 21°C to 25°C (70°F to 77°F). An HVAC system should also conserve air quality, while preventing air movement at high speed.