Passive houses in timber construction
On the old slaughterhouse premises in the north of Berlin, three 5-storey passive houses in timber construction with a total of 41 residential units have been erected by the Müllers Büro firm of architects. The following features have made them resource-efficient.
Energy efficiency using the passive house standard
The highly thermally-insulated external envelope with triple glazing passive house windows and with a natural gas filling in the pane interspace and insulated frames reduces heat losses. The walls have been constructed with a forward-looking K value of 0.087 W/m²K. Controlled living space ventilation with heat recovery prevents ventilation heat losses. Heat pumps make use of geothermal energy for the remaining heating needs. The indoor air can also be cooled using them in the summer. Photovoltaic equipment is planned for the roof. The passive houses have been optimised for comfort and energy efficiency in the context of available and currently economical building services technology. Occupiers will profit from the lowest-possible operating costs in the long term, are unaffected by energy price increases and can look to a future without worrying about being able to finance where they live.
Load-bearing structure made of renewable timber as the raw material
Timber stands out as a resource-conserving raw material since it grows again and is CO2-neutral. It has been used consistently in the upper floors for all supporting walls and ceilings with the exception of the stairway tower. Solid masonry construction (masonry walls and reinforced concrete ceilings) was necessary for the ground floor since commercial use was originally intended – this has now partially been replaced by residential use. Fire protection reasons necessitated the stairway being built with a non-flammable material. That is why precast concrete components were selected. This stairway design was simultaneously used in the load-bearing structure concept for stiffening so that it functions as a stiffening core. As a result, no further vertical stiffening elements are necessary, which in turn means an absence of restrictions on the layout plan and location of window openings. In addition to the low deadweight of timber, the core also allowed very low 10 to 14 cm thicknesses of the timber walls. This means that the external walls are no thicker than 50 cm despite the high insulating properties. A total of around 400 m³ timber was used as the main construction material in addition to a further approx. 500 m³ of derived timber panels which act as a CO2 storage system during the utilisation phase. A further positive effect of timber is that it is highly suited for prefabrication – something which enables the construction time to be minimised. In fact, one storey was erected per week during the construction phase. This permitted the first residents to move into their new home as early as April 2010 after a construction start in March 2009. This had a positive effect on financial resources since the new owners only had to simultaneously pay their rent and financing costs over a short period.
Reduction of land use
The "Alte Schlachthof" is on the boundary between the popular Berlin districts of Prenzlauer Berg and Friedrichshain. At the end of its original use, the 50 hectare plot has since been redeveloped by the city over the last 10 years. This has resulted in the construction of an attractive residential area on a plot originally used commercially under the city centre building compaction scheme. Area re-use avoided the development of new residential plots areas. Compared to the adjoining development with terraced houses, the 5-storey city houses enabled the plot to be more intensively used. In so doing, the houses were designed on a two-storey basis so that they had a similar residential quality to that of detached houses.
Adaptability to residential requirements
Since construction requires a high level of resource deployment it is important that these resources are utilised for as long as possible, i.e. by maximising the building life cycle. In view of changing residential requirements, this is only possible through flexibility of utilisation. The three city residences were designed so that flats can be spread over just one storey or over two storeys. This makes it possible to separate or combine flats at a later date. In view of an ageing population, barrier-free-living will become more and more important in the future. Each floor, even those in the two-storey flats, can be reached by lifts. The front doors have been fitted with electronic openers to allow unimpeded access for wheelchair users .