This sympathetic renovation ensured the windows retained a traditional appearance while offering excellent levels of energy efficiency. The use of high performance glass and SWISSPACER warm edge spacer bars within a slimline sealed unit helped maximise natural daylight in the property and create a comfortable indoor temperature.

The townhouse’s original owners, brothers Georg and Rudolf Stamm, understood the importance of energy efficiency when they first designed their home in 1897. While some rooms were built with single-glazed windows, which was typical for that period, the windows in the main living areas included two panes of glass for improved insulation. The brothers also installed a removable ‘winter window’, similar to secondary glazing, for very cold weather.

Over the past two years, the townhouse, which is located in a conservation area in Basel, has undergone a total refurbishment. Architects Schröer Sell were responsible for the project and site management. Lead architect Carmen Eichenberger explains: “This was a careful and considered refurbishment that excluded major structural changes. Our aim was to retain and restore as many of the building’s original features as possible.

“For example, we refurbished the roof for improved energy performance and restored the dormer window to its original design. We also retained the original room layout and main structures, including the windows and doors, to the front and rear of the property.”

 

A slimline double glazing solution

Schröer Sell worked closely with sub-contractor Holzmanufaktur Rottweil, who were responsible for restoring the windows and developing a solution that helped retain the building’s original appearance. “We reconditioned the window frames and reglazed them with the original glass”, explains Dirk Obser, project leader at Holzmanufaktur Rottweil. “This way, all the authentic characteristics of the original glass can be seen.”

The windows were restored using high performance CLIMAPLUS ECLAZ LIGHT sealed units from Saint-Gobain Glass. Its special Low-E coating means the energy performance of the double glazed units matches that of triple glazing. The slimline unit also allowed for the glass to be fitted into the original slim frames for an authentic, elegant finish.

The ECLAZ LIGHT sealed units benefit from 83% translucency, which means rooms are flooded with natural daylight - particularly important for historic buildings with traditionally small windows. The glass also benefits from low iron oxide, which means a significant reduction in the green tinge often found with other glazing solutions, allowing rooms to be viewed through the glass in their true colours.

Warm edge spacer bars for outstanding energy efficiency

SWISSPACER’s high performance warm edge spacer bars also contributed to the sealed unit’s excellent performance. With its low thermal conductivity and low Psi values, SWISSPACER Advance spacer bars were specified to boost energy efficiency in the building and prevent condensation and mould forming on the inside of the windows. Holzmanufaktur Rottweil, who regularly specify SWISSACER, says the sleek look of SWISSPACER’s warm edge solution is another big benefit. According to Dirk Obser, “SWISSPACER spacer bars are the best looking: they have a high end finish and clean, neat corners.”

The combination of the ultra-slim, high performance ECLAZ LIGHT sealed unit and SWISSPACER Advance allowed project managers to restore the windows to their former glory and with the added benefit of top thermal performance.

Project managers took a similar approach to the townhouse’s two glazed doors, one facing the street and the other opening onto the courtyard terrace. The street door required an ultra-slimline sealed unit, but Holzmanufaktur Rottweil needed to develop a completely bespoke solution for the terrace door: REVETRO. By salvaging the door’s existing glass and using it as the outer pane in a new, energy efficient sealed unit, the refurbished terrace door features the original glass complete with authentic streaks, waves and bubbles.

 

 

Site board

Project: Thorough refurbishment of a town house

from 1897 in Basel

 

Planning and

construction management: Schröer Sell Architekten, Basel

 

Refurbishment and

glazing of the windows: Holzmanufaktur Rottweil, Rottweil

 

Glass manufacturer: Glashandel Tuttlingen GmbH, CLIMAplusSECURIT Partner

 

Glass: Saint-Gobain Building Glass

Product: Double glazing CLIMAPLUS® ECLAZ LIGHT 3-10-3
with SWISSPACER Advance spacer bar