In every apartment several wirelessly networked Alpha Eos system sensors are installed in order to control the indoor air quality and heating curve. The energy for the signals is generated from sunlight and transmitted without any electromagnetic emissions. The building thus incorporates completely mains-free power, avoiding electrosmog.
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Smart Building Services Controls
All of the building services components can be controlled from central energy control units within the apartments, thus optimising living conditions and the level of consumption. All of the fans, blinds, actuators, radiators and window contacts are linked to one another, enabling smart metering via the ad hoc capture of electricity consumption through visualisations made by the Fraunhofer in-house system. The lift is equipped with a braking energy recovery (Kone) system, reducing its energy requirement by a further 60 per cent. The building is also laid with PVC- and halogenfree cables, reducing VOC emissions.
General lighting is provided by LED technology. The lighting for the staircase and balconies consumes about 1 W. Light sensors are installed in individual rooms and react to the presence of people, thus automatically regulating the brightness of the rooms.
The remaining electricity requirement is currently being purchased from a green electricity provider.
Due to the coverage of the electricity requirement by a photovoltaic unit that feeds the excess power into the local grid, the already low carbon dioxide emissions caused by the heat supply are balanced. The “WOODCUBE” thus operates at a carbon balance. A photovoltaic unit performing at 10kWp was installed on the green roof in order to provide electrical energy. This unit generates 23,000 kWh per year, corresponding to slightly more than the “WOODCUBE’s” annual electricity consumption. Excess electricity is fed into the local grid and credited to the building’s life cycle assessment.
Solar thermal analysis and optimisation of the exterior shading was carried out in order to keep the inside temperature steady without active measures. This meant that solar protection was applied only to the areas of glass where it was required.
As a result, central ventilation would have been unprofitable. Another reason for doing without it was the aim of leaving as much of the wood visible as possible: if there were centralised ventilation, it would have been necessary to install a suspended ceiling. In addition, there were hygiene concerns with regard to the possibility of cleaning the pipes. Doing without this element also meant savings on maintenance costs.
As part of an ongoing quality agreement with the IBA Hamburg, the building does not include a central ventilation unit. The design, which is open to diffusion, and the manufacturer’s 50-year guarantee against condensation problems for the solid wood walls meant that ventilation would have been desirable for reasons of comfort alone.
The actual consumption is being evaluated by the Technical University of Braunschweig as part of an external monitoring project.
All of the apartments within the “WOODCUBE” building have controlled ventilation using façade ventilators with heat recovery, and central control of the living and sleeping areas. Automatic, moisture-dependent control has also been set up in the bathrooms. Radiant heating was shown to be preferable for the “WOODCUBE” in comparison with surface heating systems, which were unsuitable due to periods of inactivity and space requirements. The heating requirement is 18 kWh/m2 per year.
The heat energy thus comes from renewable sources. All of the heating conduits are made of stainless steel, so no composite pipes were installed, allowing materials to be separated in the event of deconstruction. The radiators are designed as optimised heating surfaces and can cope with peak loads.
In addition, all of the building services components are managed from a central unit within the apartments, rather than from a decentralised point. This saves building components and additional routeing.
Room heating and hot water are provided through the “Wilhelmsburg Central Integrated Energy Network”. Heat and Electrical Energy
Energy-saving technology was built into the energy concept in order to support the energy properties and existing resource efficiency of the solid timber system. This incorporated all of the optimisations in terms of requirements, energy efficiency during operation, and user comfort when using Holz100, CLT with no glue or treatment. Fig. 12: Test pieces of the solid timber element (Holz100) of the outer wall for WOODCUBE after 60 minutes subjected to a direct flame, at a temperature of approximately 900ºC.
Visible surfaces can be maintained much more costeffectively than coatings over time by cleaning or sanding. This also applied to the untreated wood façade cladding, which was shown to be durable in a hygrothermal simulation. The higher initial investment will be largely amortised through the maintenance costs over the life cycle of the building. When making planning decisions the emphasis was therefore on longevity.
Compensation was made for this higher investment in various areas. For example, there was no need for coatings for most of the surfaces. “WOODCUBE” is a residential building with freehold apartments built with Holz100. Ongoing conversion work is not envisaged. Nevertheless, the goal is to keep running costs low. For the most part, the known life spans of all of the building components and recommendations on maintenance were taken into consideration, and the most durable types were selected for use.
The floor and ceiling elements (Holz100) were specially developed for the “WOODCUBE” project in order to allow spans of up to 500 cm and cantilever arms of approximately 250 cm, while also taking the noise protection and fire safety requirements into account.
However, the prerequisite for this was a nonrear-ventilated façade structure, which required hygroscopic evidence of no structural damage. As a result, the extensive investigation led to a single-material timber structure solution that is the first of its kind in multistorey buildings. Holz100 is a cross laminated timber system with no glue, no toxins, no chemicals, and no VOCs.
Ultimately, on the basis of comprehensive supplementary fire safety surveys, structural solutions were found that deviated from the non-flammable materials recommended in the building regulations, instead making it possible to construct a completely timber façade.
The wooden elements were made in such a way that their quality is visible to the eye, but this required milling in the factory and precise and costly preliminary planning. The façades also presented the planners with major challenges.
Long-term Cost Considerations
Solid wood supports in the required dimensions and of the desired quality are extremely expensive. In addition, steel bands had to be incorporated into the ceiling layers to create plates and stiffen the structure. Planning the installations, including electricity and sanitary facilities, plays a major role in solid wood buildings. This reduces the requirements for the stacked board core to 28 minutes. In order to ensure that there is smoke control between the residential units, the upper sides of the floors are completely covered in the product Pro Clima Intello, and professionally joined together and made flush with the walls. Holz100 is Cross Laminated Timber, without the use of any glue or preservatives.
The 80 mm thick load-bearing core layer of Holz100 can be expected to burn through by another 15 mm. The building thus has a fire resistance capacity of about 120 minutes.
For the floor and ceiling elements, the lower cladding of the solid wood elements is applied as a burn-up layer. The outer wall components are resistant to fire from the inside for more than 90 minutes, due to the inbuilt 84 mm thick sacrificial layers, which burn at 0.9 mm per minute under optimal ventilation conditions. The sacrificial layers delay the fire reaching the load-bearing core layer by approximately 93 minutes.
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