A Compact, Unitized Double Skin Facade

Thermal performance comparison in US climates





Driven by an increasing demand for high thermal and acoustic performance, transparency, and low maintenance costs, a number of facade innovations have been developed over the past 50 years. These advancements, collectively part of the emerging market of dynamic, adaptive facades, give designers the freedom to control energy loads and glare through the building envelope using building management software. Integrated, intelligent control systems are being developed to optimize energy performance and meet sustainability goals with minimal compromise to aesthetics and transparency.

Double skin facades, which feature two distinct glazed wall assemblies separated by an air cavity and typically include a shading device in the cavity, have been successfully used on a number of projects in Europe for the past 20 years, as well as a few in the US. More recently, the compact double skin facade known as MFreeS, which is a unitized cavity wall with integral blinds, has been developed by Permasteelisa Group and its research partners. To date, there are fewer applications of these double skin facades in the US market, due primarily to the lower cost of energy and less-stringent building codes.

This study uses whole-building simulation software to compare annual energy consumption of conventional, double-skin, and MFreeS facades in various US cities in a hypothetical south-facing office room, for the purpose of quantifying performance of the various systems.

The results show that overall building energy consumption can be significantly reduced by the use of double-skin and mfree-SCCF facades - by as much as 20% in most climates – relative to the baseline single skin facade. It is also seen that the conventional steady-state measures of thermal attributes, such as U-value and solar heat gain coefficient, are poor predictors of actual energy use for buildings with dynamic facades. The use of whole-building simulation tools has the potential to save more energy on a yearly basis in the US market.


Facade design in the last 50 years has seen tremendous innovation in the area of thermal performance. Some notable developments include insulated glazing units, which became commercially viable in the

Members Only

Overview of Facade Types Evaluated

In this study, the thermal performance parameters of the following five facade types are evaluated and compared in several cities in the US market (Fig. 3):

Figure 3: Typologies studied. Image

Members Only


In order to obtain reliable predicted energy performance for office buildings with dynamic DSF systems and cavity ventilation, it is necessary to use whole building simulation tools. For this purpose

Members Only


Figures 6 through 15 show the thermal and energy results of the subject room for each city. In these graphs, the five facade types are shown on the top as

Members Only

Analysis & Observations

The results from the dynamic whole building simulation show that:

In all climates, the use of DSF and mfree-SCCF results in lower total energy consumption than SSF (most notably in

Members Only

Conclusion and Future Work

From the standpoint of energy consumption in this study, Facade 4 (Interactive Wall) performs the best in all climates. Some notable examples of this DSF system in use include the

Members Only


The authors would like to thank their software and university research partners for their contributions during the developments of the innovative facade solutions.

Rights and Permissions

Aksamija, Ajla. Sustainable Facades: Design Methods for High Performance Building Envelopes. John Wiley & Sons, 2013.

BBRI(2002), Prediction of thermal comfort and energetic behavior of active facades.

Carmody, J., Selkowitz, S., Lee, E.S., Arasteh, D. & Willmert, T. Window Systems for High-Performance Buildings, New York, Norton & Co. (2004).

De Bleecker, H., Berckmoes, M., Standaert, Piet, Aye, Lu.(2012). MFREE-S Closed Cavity Facade: Cost-Effective, Clean, Environmental. CTBUH Proceedings, Shanghai, 2012.

De Bleecker, H., Berckmoes, M., Van de Linde, L.W., Standaert, P., Blasco, M.(2007). EPBD, Energy Performance of Building Directive. IWT 060756, January.

ISO 15099 (2003) Thermal performance of windows, doors and shading devices – Detailed calculations.

Laverge, J., Janssens, A. Schouwenaars, S. & Steeman, M. (2010). Condensation in a closed cavity double skin facade: a model for risk assessment. Proceedings of ICBEST 2010, Vancouver, British Columbia, June.

National Institute of Building Sciences, “Whole Building Design Guide (WBDG).” https://www.wbdg.org/guides-sp... (accessed September 12, 2017).

PHYSIBEL, (2002). Capsol v4.0 Manual.

US Office of Energy Efficiency and Renewable Energy, “EERE Success Story.” https://energy.gov/eere/succes... (accessed September 26, 2017).