Chantal Basurto Dávila
The inclusion of daylight in buildings represents several benefits: its use not only signifies a reduction in the building energy consumption through the compensation of electric lighting, it also has positive effects in the execution of human activities. Through its spectral composition, it contributes to create a better interior atmosphere for visual comfort, leading to a better performance on working tasks. It also influences biological human cycles, which has an impact on human alertness, mood and well-being. Compared with electric light, its intensity and dynamic variations have a stimulating effect by providing a connection with the exterior environment. However, for buildings located at low latitudes (between 23°N and S), the inclusion of daylight implies the admission of sunrays, which affect the visual comfort and perception of the indoor environment by altering the interior luminance distribution increasing the risk of glare. An additional unfavourable effect is the increment of the interior thermal loads which represent a risk of overheating for the occupants. In those regions, common practices such as: the reduction of the window size, the use of tinted glazing and solar protection are usually applied to buildings in the search of overcoming such problems. However, the use of such strategies also implies a reduction of the admission of daylight inducing the use of electric light, which is incongruent in countries with large amounts of this natural resource. The use of Complex Fenestration Systems (CFS) may represent a solution given their characteristics: daylight redirection and direct solar rays protection. The latter would contribute to control the admission of solar gains while maintaining a good visual interior environment. However, the appropriate selection of CFS requires a careful evaluation of their features and performance regarding their suitability to the building location. This thesis explores the potentiality of using CFS to improve the interior daylight distribution in buildings located at low latitudes while maintaining a satisfactory visual and thermal interior environment for the occupants. In order to do this, the existing daylight situation of two office rooms located in the central-north of México (Zacatecas 22° 783' N., 102° 583' W, Altitude: 2543m) were monitored from 2011 to 2013. Illuminance and luminance were measured on periods of the year that are crucial for the interior luminous environment (summer and winter solstices together with spring equinox), in order to characterize the existing daylighting situation and to study the dispersion of results obtained using a virtual model which reproduces the features of both offices. The performance of five CFS was then tested using computer simulations in order to assess their suitability to the local sky conditions. For this, three main factors were taken into account: the improvement of the interior daylight distribution, the risk of glare and overheating. The effects of the CFS in a room regarding such conditions were simulated using RADIANCE and Energy Plus using BTDF data (Bidirectional Transmission Distribution Function that characterizes the CFS’s lighting transmission properties) assessed by the use of a gonio-photometer. The assessment was performed first during the winter and summer solstices as well as spring equinox and secondly then on annual basis. The latter was done in order to take into account the daylight variation characteristics of two locations with prevailing clear sky conditions. The results obtained allow determining the CFS that better contributes to a better interior luminous environment in each building without compromising the thermal and visual comfort of the occupants.
EPFL2014
