Building Simply: Wooden Windows

Building Simply: Wooden Windows

Judith Resch

Birkhäuser

Basel

Ten window projects

The ten projects in this book are the result of the committed cooperation between craft workers and architects. Arriving at these solutions required inventiveness and perseverance, but the results show it was worth every effort.

The detailed drawings and descriptions were created after much intensive discussion between the people involved, to the best of their knowledge and belief. No liability can be accepted for errors.

Planning and design: Florian Nagler Architekten GmbH

Manufacture of pivoting window in concrete house: Hubert Mayr-Schütz joinery workshop

Completion: 2020

P1 Three research houses

Lintel, reveal, and window

The windows of the three research houses clearly illustrate how logically Building Simply was implemented here. Lintel, reveal, and window are consistent with the project’s material-specific construction method for each house and the well-considered positioning of the windows even provides adequate solar shading.

At first look, the three window forms appear to be a playful mixture of basic geometric shapes. In fact, each form is a response to the type of construction of the respective house. For the three houses, one each made from concrete, wood, and clay block masonry, and the lintel is made by hand out of a single material in the monolithic walls. That is the reason for each building having its own typical window form.

Building Simply is a research project by Florian Nagler at the Technical University of Munich. Building Simply has the aim of creating robust houses using the simplest possible component layers to provide living comfort at a reduced, essential standard. The technical equipment in buildings designed this way is straightforward to service and use and

The three research houses in Bad Aibling constructed in infra-lightweight concrete, wood, and clay blockwork.

will consume less energy over the years. The geometry of the building and the construction of the facades play a leading role in achieving this aim. In the three research houses, the development of the design for the window facades was based on research findings. This affected the size, type, and shape of the window openings, the solar shading, the window-wall junction, and the ventilation concept.

Size of window opening

To ensure window openings are an optimum size, the designer must consider the relationship between the amount of light entering the room and the energy balance, taking into account the choice of glazing. In this calculation the main influencing factors are the heat lost through the glazing and the solar heat admitted. Double glazing lets more light into the room but performs less well in the energy balance calculation than triple glazing. Both types of glazing require adequate solar shading. Solar control glass, on the other hand, certainly protects against solar overheating, but it also admits considerably less light per square meter. Windows with solar control glass would then have to be larger, and that larger area would be responsible for much higher heat losses. Triple glazing without a solar control coating is the optimum solution and gives a sensible windowopening-to-wall ratio (see Fig. 5). The balanced aesthetic achieved in the architecture of the facades for the research houses resulted from the application of this finding. Generous, undivided window openings take up a regular rhythm on the longitudinal facades. They provide adequate light in the upper floor rooms and unobstructed views out. [1]

The light transmittance TVis quantifies the visible light transmitted through the glazing

Graphical representation of the investigation to find the optimum relationship of window opening size to room size, Building Simply research project

Rule of thumb: Window glazed area = 10–15% of the room area to be illuminated, avoid using solar control glass [1]

Window with horizontal pivot mechanism

The generously sized windows with their continuous glazed surfaces would project too far into the room if used with standard tilt and turn fittings. In addition, the weight of the large windows would place high loads on the fittings. This was avoided by choosing windows that rotate on a horizontal pivot mechanism instead of a tilt-turn fitting (see Fig. 7). The principle was also tested on windows with a vertical pivot mechanism. The vertical rotational axis gives rise to a weak point in driving rain because the rebates and seals also change direction at the pivot. As a result, they fail the tests. In contrast, the more favorable position of these points on windows with horizontal pivot mechanisms makes them less susceptible to driving rain. They also offer further advantages: during the summer months, the horizontal axis of rotation of the window is ideal. In the open position, warm air flows out of the room at the top of the window overnight, while cool air flows in at the bottom. [2]

Vertical section through a horizontal pivot window 1:20

Type of window opening

Even when manufactured by hand by craftsmen, individually designed windows are still produced using standardized profile geometries. Standard fittings and tools are therefore also the rule. This situation has already influenced the design of the composite windows. The design shown here uses combinations of commonly available wood profiles: the window frames are 70 mm wide and 68 mm thick, which is more slender than the two individual frames of the original composite window together. The bottom frieze board of the window frame is made wider in the prototype. The weather bar is effectively sheltered by the balcony and can therefore simply be glued on flush. The considerable dimensional differences between the original and the new window construction show up in the face widths of the frames. The new frames are almost 20 mm wider. To approximate the character of the original facade design, continuous profile strips were placed around the window frame so that the narrow face widths could be taken up again. This has the effect of preserving the windows’ delicate lines. The glazed areas of the new window construction are almost the same size as those of the original. The insulating glazing, however, is held in by glazing beads and not by putty as with the composite window. These narrow beads are designed with a projection to highlight the profile on the inside of the rooms as well. The result is an additional, finely proportioned frame around the glazed area.

Traffic noise from the busy street in front of the main facade of the residential building has continuously increased over the decades. This could be an additional criterion for the design of the new window construction. The construction shown above would be a simply implemented improvement of the sound insulation performance. The sound insulation glazing consists of an additional pane of glass, and the casement frame profiles are 8 mm wider all round. This could achieve a sound reduction index of approximately 39 dB. Comparing the drawn elevations of the facade showing the different construction details, the even wider profile is completely justifiable.

High-rise residential building in Munich

Proposed construction for a replacement window showing a schematic outline of the original profile, horizontal section 1:2

Proposed construction for a replacement window with higher sound insulation performance, horizontal section 1:2

Planning and design: Wolfgang Zeh

Window construction: Wolfgang Zeh

Completion: 2018

Architect Wolfgang Zeh’s house fills an extremely narrow gap site in Cologne-Ehrenfeld. He used readily available components for the extensively glazed post and beam facade.

An isometric sectional representation by architect Wolfgang Zeh illustrates the room sequence.

Wolfgang Zeh’s house in Cologne-Ehrenfeld is a sensation. The architect and joiner designed it for his family of three on a gap site only three meters wide. That alone is sensational enough in itself; the way he did it is even more sensational. The plot is 35 m² in area, as big as a one-bedroomed apartment. Because of the planning rules relating to distances between buildings, the rear facade is terraced so that the higher stories become successively less deep. A sequence of rooms stretches up and down eight stories, and discovering them is fun: six cleverly designed staircases take the visitor from the entrance and meeting zone into the architect’s office, then to a bedroom lobby, crossing a half-landing to another bedroom and up to the dining kitchen, before entering a living room and finally going up to the roof terrace. The seventh set of stairs goes from the entrance down to the workshop, which is unsurprisingly the largest room in the house considering the way the go-getting architect works. He built the house himself in two phases. The windows were a special highlight. Through the extensively glazed facade, the living rooms look over the railway tracks on the viaduct opposite. Climbing up to the roof terrace gains a view of Cologne Cathedral. Zeh designed and built the facade himself, essentially for architectural reasons: the quotations submitted by various facade manufacturers were based on alternative facade configurations. Since he did not like these proposals and the construction costs would also have been very high, the architect and joiner decided to do everything himself, from planning to implementation.