Daylighting performance of sawtooth roofs for industrial buildings

Natural lighting in industrial, commercial and sports buildings is usually provided by roofs with transparent surfaces. Sawtooth roofings, in which opaque modular elements are combined with transparent surfaces, whether inclined or in various shapes, are especially popular. The exact dimensioning of these roofs is extremely important both in terms of energy savings (less electricity needed for artificial lighting) and as regards vision quality. The paper illustrates a calculation method that accurately assesses daylighting performances of sawtooth roofs. The method allows detailed modelling of the sawtooth’s shape to be created and the transmittances and reflectances of all the materials making up the roofs to be taken into account. The calculation method was applied to eleven different sawtooth roofs supplied by different manufacturers; the results were compared and some technical solutions were suggested for optimizing the performances of the roofs analyzed. Experimental verifications were performed on the method in two industrial buildings, with different roofs; the results show that the calculation method being proposed is both accurate and reliable.