Solar Activated Facade (S.A.F.)

SAF is an ideal wall construction for very energy efficient buildings also maximising solar energy use. Conventional facades attempt to de-couple the building interior from the exterior. The SAF façade offers another solution: the creation of a sun-warmed buffer. This buffer effect begins at sunrise and holds well past sunset. In this manner building heat losses are dramatically reduced. The annual energy balance of a highly insulated wall can be matched with only half the wall thickness.

What is SAF?

The solar facade SAF was invented and patented by a Swiss architect in 1998. The core of the concept is a solid wood absorber with slanted, horizontal slits. A back-vented glass façade protects the wood from the elements and helps preserve the thermal buffering effect. Behind the absorber is an insulated, conventional wooden or masonry structural wall. The SAF wall is an exciting architectural element giving a building a special, individual identity.

How does SAF function?

Solar radiation from the low winter sun is transmitted through the glass facade and absorbed in the louver-structured wooden absorber. Slowly the wood is warmed during the daylight hours. After sunset, during the next four to twelve hours the wood slowly cools down. During this time it provides a thermal buffer against the cold exterior temperatures. Building heat losses are diminished accordingly. In summer the sun is higher in the sky so sunrays strike the wooden absorber at a steeper angle. The slope of the slits into the solid wood create a self-shadowing effect. Consequently, the absorber does not heat up to the same extent as in winter.

SAF-ePlus and SAF-Air

SAF is continuously being further developed. The latest developments include building integrated photovoltaics and an air recovery system coupled with a heat exchanger.


SAF  has been successfully established in Europe for over 15 years... 

... is now coming to North America!

--> Nelson Architech owns the exclusive rights to market and distribute this patented facade system in the U.S. 


Award Winning Architecture in Switzerland

Recipient of the 2012 Lord Norman Foster Solar Award

 Hofberg 11 001 kl

Energy Concept – Minimize Consumption

The energy usage concept of the building aims to minimize the energy consumption of the building through special design features and technical application. The building is Minergie-P certified in Switzerland, which beats the legal limit of usage by 71%. These outstanding values are achieved among others through the application of a SAF façade. The summer heat gain is reduced through the massive overhanging balconies even though that means that you also reduce the passive solar heat gain during the winter. Heating is done with a heat pump and a geothermal source. Only the most energy efficient appliances have been installed and with very few exceptions in the residences the entire lighting concept is based on LEDs. In the architectural office all the lights have daylight sensors.

Hofberg 7818 kl

Energy Concept – Maximize Gain

The building produces over 180% of the annual electricity consumption. This doesn’t just provide enough energy for the operation of the building but even enough for electric mobility. The energy production is achieved through building integrated pv system in the roof as well as in the façade as part of the SAF ePlus series.

Hofberg 7841 kl

Innovation – The Thermo-Electric Façade

This project applies for the first time the newly developed thermo-electric façade SAF ePlus, which is a combination of the standard thermo-active façade SAF with glass-glass pv modules instead of clear solar glass. The heat emitted on the back side of the panels act similarly as the direct sunlight does by charging the wood absorber behind it with thermal energy which is then slowly emitted throughout the night to significantly reduce the thermal losses from the inside out.

Hofberg 7854 kl

Architect: Fent Solare Architektur