homeaboutpartnersnewsdownloads principlesin depthapplicationsteaching resourceslearning resourcesprinciples Natural Lighting Lighting standards Daylighting is more often addressed in certifications than in norms. Nevertheless, some standards point out that it is important to provide daylight in buildings for the comfort of the occupant and to reduce energy consumption. But generally, illuminance recommendations are given in terms of levels to achieve with artificial lighting. In green building certifications (BREEAM, LEED, HQE) daylighting is addressed as an important parameters of indoor quality having an impact on comfort and health of the occupant. Level of illuminances, in environmental assessment method for buildings, is more often calculated with daylight factor. Glare is addressed in recommending the use of sun protection. A view toward outside is also a parameter which enters into account.
homeaboutpartnersnewsdownloads principlesin depthapplicationsteaching resourceslearning resourcesin depth Natural Lighting BREAM BREEAM, for "Building Research Establishment Environmental Assessment Method", is probably the most used environmental assessment method for buildings. The assessment method is divided in nine main categories which are : management, health and wellbeing, energy, transport, water, materials, waste, land use and ecology and finally pollution. According to the performances of the building, points are granted in each categories and are then weighted according the category. Finally, the building is classified according to its score as pass, good, very good, excellent and outstanding. Daylighting issue is addressed in the category “Health and Well-being” under 3 subcategories which are: -Hea 1 – Daylighting whose the aim is “to give building occupants sufficient access to daylight”; -Hea 2 - View out whose the aim is “to allow occupants to refocus their eyes from close work and enjoy an external view, thus reducing the risk of eyestrain and breaking the monotony of the indoor environment.” -Hea 3 - Glare control whose the ail is “to reduce problems associated with glare in occupied areas through the provision of adequate controls.” Lighting standards
homeaboutpartnersnewsdownloads principlesin depthapplicationsteaching resourceslearning resourcesin depth Natural Lighting You have different ways to evaluate if daylighting criteria (Hea 1) is reached, for at least 80% of the net lettable office floor area : There are supplementary criteria for industrial and retail development. In the BREEAM rating system, the working plane is normally taken at 0.7m above the floor for offices and 0.85m for industry. Lighting standards Average daylight illuminance of 200lux for 2650 hours per year OR An average daylight factor to achieve according to the latitude of the building latDFmean <40°> 1.5% …… >60°> 2.2% AND Uniformity ratio of at least 0.4 OR A minimum daylight factor to achieve according to the latitude of the building OR A view of sky from desk height (0.7m) is achieved AND lat DFmin All spaces Glazed roof Room depth criterion d/w + d/HW < 2/(1-RB) is satisfied where d is the room depth, w is the width, HW is the window head height <40°0.61.05 ……… >60°0.881.54
homeaboutpartnersnewsdownloads principlesin depthapplicationsteaching resourceslearning resourcesin depth Natural Lighting LEED LEED, for Leadership in Energy & Environmental Design, is another well-known green building certification which is developed by the US Green Building Council (USGBC). According to the performances of the building, points are granted and the building is classified according to its score as certified, silver, gold and Platinum. The assessment method is divided in several categories and daylighting is evaluated in “Indoor Environmental Quality” through two sub-categories which are: - Credit 8.1 Daylight & Views which requires daylight in 75% of spaces; - Credit 8.2 Daylight & Views which requires views for 90% of spaces. In the LEED rating system, the studied area corresponds to the whole office area at 30 inches (0,76m) above the floor. LEED suggests achieving a minimum illuminance value of 269lux in 75% of occupied rooms, for a clear sky on the equinox at noon but no absolute value for the zenith luminance is given. Users are thus allowed to choose this value, which is not trivial to evaluate. A view toward outside is required in 90% of spaces. Lighting standards
homeaboutpartnersnewsdownloads principlesin depthapplicationsteaching resourceslearning resourcesin depth Natural Lighting HQE HQE (High quality environment) is the French environmental certification. Daylighting is addressed is a field which aims to create a pleasant interior environment and in the subcategory “visual comfort”. HQE evaluates the daylight through several criteria which are the access to daylight, the view toward outside, a minimum illuminance level in the room, daylight in corridor and the absence of glare. Illuminance levels are evaluated by calculating the minimal daylight factor (DF) on a studied area. The depth of the considered studied area is defined by the room and working plane height. According to the DF obtained on the studied area, the room is rated as “good” or “efficient”. If a room rated as “efficient” has a minimal daylight factor on the rest of the working plane superior to 1%, the room obtains a “very efficient” rating. The final building rate is the higher rate obtained in 80% of the rooms. The studied area is defined by the dimensions of the room and by the working plane height. As there is no criteria to achieve in the non- studied area, HQE can give points to deep buildings in which the central zone is not lit. Lighting standards 80% of studied area20% of studied areaNon-studied area DF > 2%DF > 1.5%-Good DF > 2.5%DF > 2%-Efficient DF > 2.5%DF > 2%DF > 1%Very efficient