kiDOUBLE SKIN FACADES – FASHION OR A STEP TOWARDS SUSTAINABLE BUILDINGS Ole J. Hendriksen and Henrik Sørensen Esbensen Consulting Engineers A/S, Vesterbrogade 124 B, DK-1620 København V, Denmark, Tel.: +45 33 26 73 00, Fax.: +45 33 26 73 01, e-mail: email@example.com Anders Svensson and Pontus Aaqvist White Architects AB, Skeppsbron 7, S-211 20 Malmö, Sweden, Tel.: +46 40 660 93 00, Fax.: +46 40 611 44 79, e-mail: firstname.lastname@example.org Abstract – In recent years double skin facades has found increased use both as part of renovation of buildings or as part of new buildings to improve transparency. Double skin facades lead to improvement of daylight levels and view to the outside, but glare problems can be increased. It is possible to reduce heat loss and external noise, when taking the extra layer of glazing into account, compared to a traditional glazed facade. Protection of external solar shading devices against wind, and degradation seems to be a very important issue. Furthermore, ventilation and fire safety measures need careful consideration at the design process. 1. INTRODUCTION In recent years double skin facades have found increased use both as part of renovation of buildings or as part of new buildings to improve transparency. This paper deals with the question: Are double skin facades an architectural trend or a step towards sustainable buildings? One of the objectives of double skin facades is to reach a satisfying indoor climate with a reasonable energy consumption for the building. In order to reach that objective several indoor climate and energy aspects must be taken into account, when double skin facades are designed. Furthermore, fire safety conditions play an important role in the design of these facades. Double skin facades are very sensitive to outdoor climate due to large glazed surfaces compared to a traditional window facade, this calls for a detailed analysis of transparency, solar gain, glare, daylight, view to the outside, ventilation and control strategy, heat loss, noise and weather protection. The paper is based on a Swedish research project on double skin facades, which was carried out as case study of existing double skin facades of non-domestic buildings. The focus is on architectural aspects as well as indoor climate and energy issues presented in an overall way. The case study deals with North European office buildings. 2. DEFINITIONS AND TYPOLOGY A double skin facade could be defined as glazing layers divided by a cavity. One of the main characteristics of a double skin facade is the combination and position of the glazing layers, which could lead to the typology shown in table 1. DSF Outside Inside Type 1 Sub-type 1.1 Opening(s) in outer layer 1.2 Opening(s) in inner layer 1.3 Opening(s) in both layers 2.1 Opening(s) in outer layer 2.2 Opening(s) in inner layer 2.3 Opening(s) in both layers
2 Outside Inside
Table 1 Typology for Double Skin Facades (DSF). 3. MAIN FEATURES OF DOUBLE SKIN FACADES Glazed facades have large impact on the impression of a building, it affects indoor climate and energy aspects of the adjacent buildings and has some aspects, which more or less interact or depend of each other. These aspects are shown in figure 1. Besides these aspects of architecture, indoor climate and energy some basic functions of facades should also be fulfilled for double skin facades without depreciation compared to a traditional facade. The basic function of a facade is to serve as a building envelope, keeping out cold and water and letting in air and light. The double skin facade serves as an extra buffer zone and collector of solar energy or as a shaded ventilated cavity protected from rain and strong wind. (Tombazis, 1996).
Facade type Traditional window facade DSF 1+2
LT % 77 66
Rg % 30 80
LT*Rg % 23 53
Index % 100 230
Daylight/ view out
Table 2 Relative light effective areas for a traditional window facade and a...