5.- Orientation and lighting

Sunlighting, openings, and shapes

A detailed, accurate study of openings has been conducted. The building’s orientation, with long east and west walls, is not the best for providing the most pleasant views or optimal comfort, due to overheating. To offset this, spaces are redirected so as to face south, forming the saw-tooth pattern, which closes off the north and west of the building, opening all the spaces to the south. This gives the best orientations from the climatic standpoint and affords the most open views. Using this system, 89% of the surface of the spaces face south and east. (Figure 1)

    

Figure 1. Saw-tooth and brise soleils (sun-breakers) to give a self-shading effect

This saw-tooth or zigzag, together with the brise soleils that protect all the openings, give a self-shading effect which reduces cooling load without restricting natural light (Figure 2). According to the simulations performed, and comparing simulated buildings 1 and 3, as well as 2 and 4, the self-shading effect in the design is seen to yield a 27% reduction in cooling requirements in a building which strictly complies with Spanish Building Regulations (CTE). Together with other lighting strategies, in the LUCIA building this leads to a 29.6% saving in cooling energy requirements based on the E-Quest method, allowing direct differences to be established between one “straight facade building” and one with an “saw-tooth facade”. There is an estimated 54% (Graph 1) saving thanks to the self-shading effect. In addition to offering significant improvements in user wellbeing, the zigzag solution provides clear thermal and financial advantages. One key factor to be taken into account regarding Spain is the importance of providing cooling during several months of the year.

Graph 1.  Reduction in cooling requirements in kWh/m² year with the self-shading effect between the various reference buildings and LUCIA

Figure 2. Comparative summary of direct lighting between the various reference buildings and LUCIA

Shape and natural light

The compact shape of the building favours heat loss reduction in addition to providing natural lighting in interior areas. To achieve this, circulation areas, staircases, and areas near lifts enjoy natural vertical light from skylights, over which photovoltaic devices will be located for two further purposes: to filter light, and to produce electrical energy. Added to these is the glass-covered south-east facade, comprising the double photovoltaic skin which directs the filtered light to the interior whilst at the same time producing electricity. Finally, the devices or tubular daylighting devices situated inside each office or laboratory increase the level of natural light, channelling it directly from the roof to each of the floors. As well as increasing the amount of natural indoor lighting, these devices lead to a significant reduction in energy requirements for lighting. Average annual lighting consumption, which in office spaces comes to 38.90 kWh/m2 according to Region of Madrid calculations, is cut to 12.60 kWh/m2 in the LUCIA building. 

According to the simulation carried out, the annual 146,190 kWh lighting that would be needed by the reference building (ASHRAE standards) would be cut to 74,790 kWh in the LUCIA building (approximately half) thanks to these devices (Figure 3). A total of 27 devices will be installed at an estimated cost of 13,483 €. One key point is that these devices function purely on an optical effect and require no power supply to work. 

Figure 3. Tubular daylighting device leading to interior of offices and reducing energy demand for lighting between various reference buildings and LUCIA