LEED (BD+C)- Indoor Environmental Quality Credit:  Thermal comfort

LEED (Leadership in Energy and Environmental Design) is a green building certification program that promotes sustainable building design, construction, and operation. The Indoor Environmental Quality (IEQ) category of LEED focuses on creating a healthy and comfortable indoor environment for building occupants. One of the credits in the IEQ category is Enhanced Indoor Air Quality Strategies, which is applicable to various building types, including new construction, schools, retail, data centers, warehouses and distribution centers, hospitality, and healthcare.

The intent of the Enhanced Indoor Air Quality Strategies credit is to provide quality thermal comfort that promotes occupants’ productivity, comfort, and well-being. This credit requires meeting the requirements for both thermal comfort design and thermal comfort control.

The LEED requirements for thermal comfort design vary depending on the building type. For new construction, schools, retail, data centers, hospitality, and healthcare, there are two options to choose from.

Option 1 is to design the HVAC systems and building envelope to meet the requirements of ASHRAE Standard 55–2010, Thermal Comfort Conditions for Human Occupancy, with errata or a local equivalent.

Option 2 is to design the HVAC systems and building envelope to meet the requirements of the applicable standard, such as ISO 7730:2005 or CEN Standard EN 15251:2007.

To achieve the thermal comfort goals required by LEED, the following steps are recommended:

Step 1: Establish Thermal Comfort Goals

It is essential to work with the building owner to understand their expectations for the indoor thermal environment, the level of control that occupants should have, and the characteristics of the occupant population. It is also important to determine whether a tightly controlled environment is required or whether some variation in indoor conditions is acceptable. Additionally, consider including factors and design criteria related to occupants in the owner’s project requirements (oPR) for commissioning activities.

Step 2: Select Conditioning System

Based on the established thermal comfort goals, determine the best conditioning approach for the project. Consider whether the project is a candidate for natural conditioning and identify program areas that could be designed to accommodate cross or stack ventilation. This step is crucial because the conditioning system selected will impact the building’s energy use and indoor air quality.

Step 3: Select Comfort Controls

Determine the best thermal comfort controls for the conditioning system(s) selected based on the type of project and occupant’s activities. Examples of eligible thermal comfort controls include thermostats, ceiling fans, adjustable underfloor diffusers, task-mounted controls, and operable windows. Zone the conditioning system to ensure that at least 50% of individual occupant spaces have individual thermal comfort controls. Additionally, provide at least one group thermal comfort control in each shared multi-occupant space.

Step 4: Select Thermal Comfort Standard

Decide which standard or set of standards is suited to the project. Option 1, which uses ASHRAE standard 55-2010, is suitable for most US project teams. Option 2 relies on two international standards, ISO 7730-2005 and EN 15251-2007, to document mechanically and naturally conditioned spaces, respectively. Both options include compliance paths for mechanically and naturally conditioned spaces based on the same comfort models.