Author(s)

S. Robertson & M. Thompson

Abstract

Roof windows are often used as a major glazing element in loft conversion projects and to create a room in the roof space of new residential developments. Selecting the correct size of roof window is subject to a range of potentially competing influences, including the need to satisfy building regulations and planning control legislation. This paper describes a recent investigative project to address a particular research question: ‘When considering the daylighting and energy consumption aspects, how can designers determine the appropriate size and position for roof windows in loft rooms?’ The primary objective was to identify appropriate roof window size and position for a typical loft room, when based on accepted numerical daylighting criteria. The research method that was adopted used standard calculations, scale modelling under an artificial sky, computer simulations and internal illuminance measurements for real loft rooms. The relative daylighting performance of a dormer window was also determined using similar techniques. By considering an example of typical modern residential construction, it was then possible to illustrate the effect of variation in roof window size on annual energy consumption. Finally, the paper outlines the preliminary development of a simple graphical design tool that exploits the research. This tool is intended to assist homeowners and designers in selecting roof windows that optimise both the daylighting and energy consumption aspects. Keywords: roof windows, dormer windows, loft conversions, daylighting, energy consumption, design tools. 1 Introduction Roof windows are tilting double glazed units that are fitted in the plane of the sloping roof surface. Such windows are often used as a major glazing element in conversion projects for domestic lofts, agricultural barns and former industrial

Keywords

roof windows, dormer windows, loft conversions, daylighting, energy consumption, design tools.