Due to the rising number of Binderholz Bausysteme GmbH employees working at the company’s Hallein site, it has become necessary to extend the existing offices to create adequate space for existing and new employees. The “TimberBrain”, as the new office is known, provides space for up to 120 workplaces with a usable area of 1,335 m². Apart from the spatial advantages, the new building also provides a number of environmental and economic benefits.
Project Cost-efficient and future-centric office building
Place Hallein, Austria
Developer Binderholz Bausysteme GmbH
Year of construction 2019
Architecture/Design Huber-Meixner & Partner Ziviltechniker Gesellschaft m.b.H
Execution MHB - Holz und Bau GmbH based in SW Austria
Building services design IB-Krallinger GmbH
Material use 610 m³ binderholz CLT BBS, 20 m³ glulam GLT and 100 m² 3 layer larch panels
The new four-storey building accommodates a number of modern offices, a spacious seminar room and two meeting rooms. The floors are connected by a staircase and a lift. The building services plant room is located on the roof of the building and has been clad with CLT BBS. The construction of a ramp means that the main entrance and emergency exit are now fully accessible. The grounds of the building have also been redesigned with the car park now on the west side, and a specimen tree has been planted in the protected inner courtyard that can be used during breaks.
The design of the entire building took only 12 weeks including the design of the building services, which were considered in great detail (bonding requirements, recesses, openings etc.). The carpenters only needed 12 working days from the start of timber construction to complete a rain-tight flat roof. This fast construction time was made possible by splitting the workers into two assembly teams and prefabricating as many BBS walls as possible on site. The largest wall element fitted, almost 23 m³ binderholz CLT BBS, measures 7.3 m x 13.5 m and weighs a hefty 11 tonnes. It was a truly impressive spectacle to behold as the carpenters installed this wall with the aid of a 100-tonne mobile crane.
The existing office building was also fully redesigned. The former main entrance was converted into an emergency exit, which then provides space for a further office in the old part of the building. A two-storey connecting passage with the central main entrance and spacious entrance foyer connects the ground and first floors of the old building to the new one.
A total of 610 m³ binderholz CLT BBS was used for the new building: of which 450 m³ were BBS 125 and 160 m³ BBS XL elements. 20 m³ glulam and 100 m² 3 layer solid wood panels of spruce, stone pine, larch, pine and white fir were also used in the new building. The load-bearing external walls were also constructed with what are known as BBS Thermo elements. BBS Thermo wall elements are 23.4 cm thick BBS construction elements without any additional thermal insulation, the external face of which is planed larch and the internal face of which is sanded spruce on this project.
The solid timber wall construction without additional thermal insulation is below the required mathematical U-value and so fundamentally it does not comply with the statutory requirements. However, a derogation enshrined in the Salzburg Building Act permits its use in compliance with the law. binderholz has already demonstrated on several reference projects already built that the BBS Thermo construction method is very energy-efficient and thermally efficient as well as sustainable. To scientifically prove the thermal insulation properties of a BBS Thermo wall, approx. 160 data points are detected in our office building: air temperature, air humidity, thermal radiation, stratification temperature, surface temperature, core temperature and air quality sensors in four research and test chambers. Different parameters, including temperature and humidity curves in the individual timber layers of the external wall, thermal flex in the wall construction, surface temperatures and air flows in the interior, indoor air quality (temperature, air humidity and CO2) as well as volatile organic constituents of the wood (VOC), are recorded over time and scientifically analysed and evaluated.
BBS has a monolithic structure, in other words is a “single piece of wood”, incorporating only 0.6% environmentally safe adhesive. The solid finished element can bear heavy loads, is fire-proof, can quickly be fitted dry and has sound and thermal insulating properties. It helps to regulate indoor air humidity, creating a comfortable and balanced interior room climate - both in summer and in winter. binderholz considers that there is major potential in future for construction using so-called BBS Thermo walls, a pure solid CLT BBS construction without the need for an additional layer of thermal insulation, with an external larch layer for the structural protection of the timber on the façade. This solid timber construction fully adheres to the philosophy of using a single material. BBS Thermo combines the known technical benefits of solid construction with the eco-friendly benefits associated with using the sustainable raw material of wood.
Convinced by the material and construction properties, binderholz has already constructed three administrative buildings with BBS Thermo walls: the Binderholz Deutschland GmbH administrative building in Kösching / Germany (276 mm BBS Thermo wall), the Binderholz Unternberg GmbH administrative building in Unternberg / Austria (200 mm BBS Thermo wall) and the Binderholz Nordic Oy administrative building in Lieksa / Finland (234 mm BBS Thermo wall). These buildings have already had very positive experiences with the BBS Thermo product, particularly in relation to its energy consumption for heating and cooling and the interior climatic effects of the material.
The newly constructed office building at the binderholz sales site in Hallein is definitively a timber construction with many features. The four-storey extension was connected to the existing building by a two-storey connecting wing. The extension was needed to accommodate the ever-growing team.
The staircase is constructed using BBS REI60 enclosure walls (60-minute fire protection), which are clad with 12.5 mm thick A2 plasterboard. The staircase itself is a pure solid timber construction made of BBS RE160 with a clear tread of 1.20 m and was also clad with 12.5 mm thick A2 plasterboard. Apart from the staircase, there is also a passenger lift for up to 8 people from the ground floor to the third floor. The lift cabin measures 110/140 cm. The lift shaft also has a multi-shell structure: BBS REI60 wall element, mineral wool, BBS REI60 wall element and internal plasterboard cladding (A2). The foundation plate is made of reinforced concrete. All external walls and all load-bearing interior walls are made of CLT BBS REI60 as per the static requirements. The non-load-bearing walls are made of CLT BBS with plasterboard cladding on one side.
As solid wood is extremely versatile, CLT BBS REI60 was also prescribed as per the statics for the roof of the office building and sloped roof insulation is used as per the building physics. Wood-aluminium windows with triple glazing are installed throughout the entire building. In addition to the main entrance and the emergency exit, the use of the entire building is barrier-free (accessible). The building also includes a covered bike parking space, a covered break area and a covered waste area.
Heat is supplied by the building’s own local heating system with a heat exchanger housed in the old building. Heating is provided by low temperature panel heating systems fitted to the ceilings of the offices. The internal functional rooms in the core of the building (wet rooms, kitchenette, plant rooms etc.) are unheated. The building is cooled by a water-based system fed with groundwater. Heat is dissipated via the heated/chilled ceiling system (gentle cooling) and transferred to the groundwater via an isolating heat exchanger = 100% free cooling. The fresh air required is preconditioned (cooled/heated) by an air handling system, which is also fed by the biomass system and groundwater. The air handling system is fitted with a heat recovery system to return the exhaust air energy back to the building. The additional production of a steam humidifier transforms the air handling system into a full air conditioning system – steam humidification is provided electrically, with electrical energy being generated from solar energy by a photovoltaic system installed on the roof of the building. This photovoltaic system (30 kWp) also supplies all other electricity consumers in the office, feeding any surplus electricity back into the power grid on the industrial park.
binderholz would like to examine more closely the nature, manner and functionality of this new and optimised BBS Thermo construction method with the construction of the new Binderholz Bausysteme GmbH administrative building at its Hallein site. In particular, it wishes to focus on the building physics properties and the behaviour of the construction under real conditions. The examinations are to be conducted as part of a scientific research project being run in conjunction with the Chair of the Timber Construction and Building Construction at the Technical University of Munich, headed up by Prof. Dr.-Ing Stefan Winter.
At the same time, binderholz wishes to use the building to examine the internal air hygiene aspects of the building construction and the positive effects of it on the workers in collaboration with the Institute for Quality Management and Environmental Hygiene (Weikersheim, Germany), and Karl-Heinz Weinisch’s preventative health care practice (in Weikersheim, Germany). The 4-storey building is ideal for conducting the relevant long-term experiments and also taking into account the employees’ user behaviour.
Photos: © binderholz