Daylight and overheating prediction formulas for building design in a cold climate

Abstract

Indoor comfort in buildings has a critical impact on occupants’ health and cognitive performance. The fulfillment of daylight provision and overheating risk requirements can be challenging. This paper proposes a coupled method based on prediction formulas that can be used to assess daylight provision and overheating risk in buildings. In addition, this method can be used for the design of interior floor plan and window sizing in order to rooms fulfill simultaneously both performances. The considered daylight provision requirements are based on the minimum Daylight Factor (minDF) defined by the European standard EN 17037, and the overheating risk requirements are based on the degree-hour (DH) metric adopted by the Estonian regulation. The minimum window-to-wall ratio (minWWR) to fulfill minDF-based requirements and maximum g-value to fulfill at the same time DH-based requirements for any room design can be calculated or represented graphically. The prediction accuracy in terms of relative RMSE is up to 0.20 for minDF and DH values. By using this approach, designers can minimize the number of design iterations during early stages, as well as the required computational time required by daylight and energy simulations. Furthermore, the proposed coupled method based on minDF and DH prediction formulas has big potential to help architects and designers to achieve the combined fulfillment between daylight provision and overheating protection during early stages of the design process within the Estonian context. Finally, the authors recommend the proposed coupled method to regulation makers for future building standards and regulations.