Daylight and Views in Green Building

The debate over the contribution that daylight and views make to a healthy interior appear to be over as the inclusion of these elements is encouraged and incentivized by many of the green building rating systems used to define success in green building today. The Leadership in Energy and Environmental Design (LEED) green building rating system, created by the USGBC, is the preeminent green building standard in the United States. This standard has included credits for bringing daylight and views into the interior for years, and in its most current version, LEED v4, more points have been allocated to this area to underscore its importance.

The Daylight credit offers up to three points for achieving a minimum amount of daylight penetration in the interior while not exceeding a maximum intensity. The Quality Views credit awards one point for designs that can provide a quality view (one to two points in LEED Healthcare).

The fact that there is a requirement not to exceed a maximum sunlight exposure limit, and for the use of glare control devices, indicates that USGBC recognizes that controlled exposure to daylight is an incredibly positive and beneficial aspect of the interior environment, but that uncontrolled daylight in the interior can be destructive.

These maximum and minimum intensity requirements create a significant design challenge for architects. Given the dynamic nature of daylight intensity, it is hard to design a building that has enough glazing area to provide the requisite level of daylight and views for a large proportion of the occupied space without exceeding the maximum intensity limit, especially in the immediate vicinity of the window wall. In addition, the increased use of glass can create challenges with meeting the energy performance requirements in the Energy and Atmosphere credit area because the insulating value and solar heat gain of a window is higher than an opaque wall.