Design Proposal


Double-Skin Facades and Achieving Thermal Comfort

Research Question: How long does it take to achieve thermal comfort in a space using the concept of a double-skin facade? What factors (light source, distant from light source, wall material and thickness, glass thickness) limit the passive heating and cooling of an enclosed space?

Abstract: Adapting the three common North American classifications of double-skin facade systems, this project works to answer the question of how long it takes to achieve thermal comfort in a space using the methods of these facade types. In constructing a unit to replicate how the typical double-skin facade works, we would like to measure how the capturing of hot air within the air cavity of the facade can transfer heat to an enclosed space through solar heat gain on the facade. In another iteration based on the North American classifications, we intend to test how the natural ventilation of that air out of the cavity works to cool a space by taking hot air out of the space through additional openings ​ ​

Double-Skin Facades:
  • Introduction: A double-skin facade is an envelope system consisting of two exterior building skins placed in such a way that an intermediate cavity is produced between the two layers of glass. This additional facade is typically installed over an existing building facade, the new space between the second skin and the original facade acting as a buffer zone to insulate the building (Poirazis, 2004). The main layer of glass is usually insulated, with the air space between the layers acts as insulation against temperature extremes, winds and sound. The air cavity situated between the glass is typically naturally or mechanically ventilated. The origin and destination of the air can differ, depending on the climatic conditions of the region, the use of the building and its HVAC system. The buffer zone can also be heated by solar radiation, depending on the facade’s orientation. For south-facing facades, the solar heated air can be used for heating purposes in colder climates. Venting is required to prevent overheating in other regions. In colder climates, the solar gain within the cavity may be circulated to the occupied space to offset heat requirements. The assumption associated with double-skin facades is that a higher insulative value may be achieved by using this configuration versus conventional glazing configurations.
  • History: The fundamental concept of the double-skin facade was first explored and tested by architect Le Corbusier in the early 20th century. Known as the “mur neutralisant” (neutralizing wall), the experiment involved inserting heating and/or cooling pipes between large layers of glass. 

  • Classifications of Double-Skin Facades: These types of facades can be classified in a number of ways, based on their different methods of air ventilation and overall energy consumption, as well as their geometry (Poirazis, 2004). The four types defined by their geometry include:
    • Multi-Story Facade
    • Shaft Box Facade
    • Corridor Facade
    • Box Window Facade
      • The geometry and type of double-skin facades are crucial for the properties of the air inside the cavity. The function of the facade and the building’s HVAC system is closely dependent on the temperature and air flow of the air between the glass layers.
  • Based on the North American classifications of double-skin facade systems, three types are recognized based on their air ventilation performance (Boake, 2002):
    • Buffer System
      • This system predates insulating glass and was invented to maintain daylight in buildings while increasing insulating properties of the wall system. Using two layers of single glazing, a cavity is sealed and allows fresh air to enter the building through additional controlled means -- separate HVAC system or box type windows in envelope. Shading devices can be included in the cavity to control solar heat gain
      • Another application of this system is the method of capturing fresh air that enters the cavity and heating the air through solar gain. This can work to heat the occupiable space beyond the facade when dealing with colder climates. Ventilation of the cavity is required to prevent overheating when the temperature rises 
    • Extract Air System
      • This system consists of a second layer of glazing placed on the interior of a main facade of double glazing. The air space between the two layers of glazing becomes part of the HVAC system. The heated air between the layers is extracted through the cavity by use of fans, tempering the inner layer of glazing while the outer layer works to minimize heat-transmission loss. Fresh air is supplied by HVAC and the air contained within the system is used by the HVAC.
    • Twin Face System
      • This system consists of a conventional curtain wall or thermal mass wall system inside a single glazed building skin. This system can be distinguished from Buffer and Extract Air systems by its inclusion of openings in the outer skin to allow for natural ventilation. The internal skin offers the insulating properties to minimize heat loss. The outer glass skin is used to block or slow the wind and allow interior openings and access to fresh air without noise or turbulence. Ventilation openings on the outer ski moderate temperature extremes within the facade.
  • Characteristics that influence the properties of the air in the cavity:
    • Depth of the cavity
    • Glass pane type
    • Type and position of shading devices
    • Size and position of the inlet and outlet openings of the cavity
    • Strategy of ventilation
      • Repeated simulations when changing these characteristics can provide information for the way that the temperature of the air at different heights of the cavity changes for different configurations.
Picture
Buffer System
Picture
Extract Air System

Fabrication Technique:

​Sources: 

Aziiz, Akhlish Diinal, S. Wonorahardjo, and M.D. Koerniawan. “Effectiveness of Double Skin Facade in Controlling Indoor Air Temperature of Tropical Buildings.” Institut Teknolgi Bandung, 2018. https://iopscience.iop.org/article/10.1088/1755-1315/152/1/012016/pdf.

Boake, Terri Meyer. “The Tectonics of the Double Skin: Green Building or Just More Hi-Tech Hi-Jinz?” Montreal, Quebec, 2002. http://www.tboake.com/pdf/tectonic.pdf.

Faggal, Ahmed Atef. “Double Skin Facade Effect on Thermal Comfort and Energy Consumption in Office Buildings.” Ain Shams University, 2014. https://www.researchgate.net/publication/312040800_Double_Skin_Facade_Effect_on_Thermal_Comfort_and_Energy_Consumption_in_Office_Buildings.
​
Poirazis, Harris. Double Skin Facades for Office Buildings: Literature Review. Vol. 4. 2004. Division of Energy and Building Design, Lund Institute of Technology, Lund University, n.d. http://www.ebd.lth.se/fileadmin/energi_byggnadsdesign/images/Publikationer/Bok-EBD-R3-G5_alt_2_Harris.pdf.