16-0714 v3.0/Operable Windows and Fresh, Healthy Air in an Existing Building


The Delos Headquarters project is an approximately 16,000 square foot project in an existing building in NYC. Pursuing not just Petal Certification and LEED Platinum, but also WELL Platinum, we have rigorous sustainability goals as well as robust health goals. The two floors that we will occupy are surrounded by glazing, providing adequate daylighting throughout the office. The new space also includes access to a 1,520 sf outdoor terrace, open to all occupants of the space at all times.

The WELL Building Standard is a holistic, evidence-based and performance-driven building standard that addresses all aspects related to human health and wellness in the built environment, including air, water, nourishment, light, fitness, comfort and mind - within these concepts, air quality, thermal comfort, individual control and outdoor access are required to achieve WELL Platinum Certification which aligns with the objective of the Health and Happiness Petal of LBC.

However, we have found that the operable window requirement hinders our ability to meet the Health and Happiness Petal requirements as we are moving into an existing building with a curtain wall system, which does not have operable windows. However, as the intent of Imperative 07, Civilized Environment, is to allow occupant control of fresh air and tangible access to the outdoors, we contend that free access to the dedicated terrace, along with a specialized HVAC system, is acceptable to meet the intent of operable windows. We also find this strategy superior to providing operable windows, due to air quality and thermal comfort issues that may arise by haphazardly opening windows due to our location in a dense urban area with full seasonal fluctuation.Traffic noise has also proven to be a leading cause of stress and even serious health conditions like stroke and heart attack. In NYC, the best way to adjust for this is by adding acoustical treatments in a sound-controlled space.

A dedicated outdoor terrace:

  • Allows occupants to get fresh air when desired
  • Allows occupants the ability to actually go outside to experience the outdoor environment (rather than just a window)
  • Avoids the potential decline in indoor air quality by opening a window and introducing unfiltered outdoor air, as the project is located in a dense urban area and the outdoor air provided by the HVAC is filtered to remove particulate matter (2.5 and 10)
  • Avoids the potential thermal discomfort of others indoors by opening a window and introducing untempered humidity and temperature, as the project is located in New York, which has full seasonal fluctuation.

Our specialized HVAC system:

  • Is designed to provides a thermal gradient across the space to allow occupants the ability to move to areas where they feel most comfortable. Opening windows would affect this carefully modeled system.
  • Provides ventilation rates 30% higher than required by ASHRAE 62.1 to introduce additional amounts of outdoor air.
  • Includes a demand-controlled ventilation system tied to CO2 sensors to guarantee that CO2 levels in densely occupied spaces are kept below 800 ppm.
  • Filters particulate matter (2.5 and 10) to improve the quality of the indoor air.
  • Monitors the quality of both indoor and outdoor air, to ensure indoor air quality is always optimal for human health and indicates when it is ideal to go outdoors.

While the Health & Happiness Petal Handbook clarifies that poor outdoor air quality and humidity do not provide exemptions from meeting this imperative, operable windows:

  • Introduce unfiltered outdoor air which may compromise air quality.
  • Introduce untempered outdoor air (temperature and humidity) which may compromise thermal comfort.
  • Per our engineer, disrupts the design of the mechanical system, which may introduce condensation in our raised floor and stack effect issues in winter.

While operable windows within 41 ft of workstations is one strategy to provide access to fresh air and the outdoors, the combination of a dedicated, accessible outdoor terrace and robust HVAC system actually creates a healthier space for occupants. The inclusion of an outdoor terrace provides the opportunity for employees to seek out fresh air whenever desired and a more tangible access to the outdoors than windows provide without compromising the air quality and thermal comfort of others.


The terrace and specialized HVAC system, though designed for occupant happiness, thermal comfort, and high air quality, do not meet Imperative 07 requirements to provide access to daylight and fresh air within 9 meters (30 feet) of staffed workstations. There is not sufficient evidence of meeting the intent of this Imperative, which is to provide occupants control over their environment, and connections to nature, fresh air, and daylight as they work inside the project, to warrant an Exception.

NOTE - Exception I07-E5 Operable Windows in Renovation Typology, created subsequently, would permit this approach.

Post ID 5733

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