LOCATION
Sluppen is located 4 km South of the city centre of Trondheim next to the Nidelva river. Nevertheless, when looking in the map, one can see that it is quite in the middle of the built area of Trondheim. It has a good infrastructure connection to the highway and by bicycle one can reach large parts of the city very fast. The area is at the beginning of a new district development with first buildings having been already erected. In near future new public transport hub will be added to the area improving its reachability further.

SLUPPEN AS ZEN
The new development of Sluppen will consist out of new office and residential zones. The core idea for the ZEN project is that both zones have different energy demands. Residential areas will be more dependent on receiving thermal energy, while office buildings instead need larger amounts of electricity to supply their equipment. Due to a good insulation of the building envelopes office buildings can to a large extent heat themselves with the internal heat gains (IHG) from those appliances. However, at the same time these IHG increase the cooling demand during warm periods - offices produce more heat than they need. Instead of only ventilating out the excess heat the idea is to store it in a large seasonal thermal energy storage in the district and to use this energy for covering the heating demand of the offices and parts of the residential area during the colder months. By adding office buildings with optimized solar facades and solar hot water systems the supply of heat can be increased and potentially 500 households can be supplied fully with heat generated by office buildings. This system has the advantage of producing very clean thermal energy with embodied emissions 3.5 times lower than from the Norwegian grid and 1.5 to 2.5 times lower than energy produced by PV systems. Another reason to opt for such district heating system is the use of a large centralized storage tank, which has less heat losses and causes less emissions than comparable systems with multiple smaller tanks in many buildings. The second part of the ZEN development will focus on providing the large amount of electric energy needed in the offices. While the latter provide heat for the residential areas, the households can provide the offices in return with solar electricity. Since the residential area will be developed less high and dense than the office zones the ratio between roof space and GFA improves, giving place to the more space demanding PV-modules. The following work will focus on a possible district heating office building.

SPATIAL CONCEPT
The building site is located at the border of the office zone towards a green belt and residential areas. As office districts tend to become lifeless in the after-work hours the concept implements functions which blur the line between work and freetime. The possibility to shift between co-working spaces, cafe and bar functions will create flexibility throughout the day.

FORM FINDING
The optimal angle of the solar surface was determined by software simulation. The output showed the best angle for receiving as much as possible solar energy on the surface throughout a year. As the energy demand is the highest during winter but production strongest in summer, large amounts of the produced energy have to be stored. As these systems come along with heat losses it is better to increase the angle of the facade slightly, reducing its solar energy production in summer and increasing it in winter. So, less energy has to be stored and additionally more space is available in the building. The sun path diagram shows that the sun stands low above the horizon at most times of year. To prevent self shading of solar systems a solar facade seams to be the best choice. Additional, the wind rose diagram shows that the prevailing winds are coming from west or east, giving the potential of using them for efficient natural ventilation.

FLEXIBILITY
“Commercial buildings have to adapt quickly, often radically, because of intense competitive pressure to perform, and they are subject to rapid advances that occur in any industry. Most businesses either grow or fail. If they grow they move; if they fail, they’re gone. Turnover is a constant. Commericial buildings are forever metamorphic.”
“How Buildings Learn” Stewart Brand, Penguin Books
The positioning of the core of the building and its structural beams was done according to scenario based planning, taking already into account changing spatial demands of tenants. Each office floor can be divided in up to 4 different sized parts, allowing tenants to grow or shrink in different levels. Flexible sliding walls help to provide short term flexibility by giving the possibility of creating different room layouts or partitions only in minutes. The daylight factor analysis shows that the deepest floor reaches still the needed requirement for daylighting. As the higher floors reduce in depth the conditions improve.

ANALYSIS
Differing to the ZEN concept, in the early stage it was tried to use a seasonal storage tank for the building alone. IHG would cover most of the heat losses through the building envelope and ventilation and only a small amount of SHW modules was needed to heat also the domestic hot water. The rest of the solar facade was used for electricity production, covering around half of the electric need of the offices. The construction for a large thermal energy storage for one building alone turned out to be too costly and due to its large size hard to integrate in the architecture. Therefore, the ZEN approach was looked closer at.
The new system produces heat by SHW modules on the solar facade. This thermal energy will be used for providing domestic hot water and to preheat the inlet ventilation air, if needed. Due to heat recovery at the ventilation exhausts the heat losses can be minimized. All the heat that is not needed at the time in the building is transported to the nearby pit thermal energy storage. And in the same way, if more heat is need in the building than produced, heat from the storage is pumped back.

Simulations state that the building has a low energy demand. One third of the energy needed is thermal and two third electric. Two different scenarios have been looked at. First, how the building would perform by its own (ZEB approach), focusing on the on site renewable energy production and emission reduction. Secondly, how the building would function in a ZEN scenario. The ZEB scenario visualizes that the solar facade can be used to cover 63% of the buildings energy need. The ZEB ambition level ZEB-O % EQ can be reached. In the ZEN scenario the solar facade would be used only for thermal energy production. The heat produced can cover the annual heating demand of the building and additionally 76 more households (2/3 of energy demand is thermal). The delivered residential buildings have to provide 1420 m² PV-module surface to cover the annual electricity demand of the office building. This system would lead to an higher emission reduction than the ZEB approach, as more renewable energy can be produced and the efficiency of the solar thermal system increases.

In regards to cost reduction for the building, the construction has been planned in a way that prefabrication and easy on site assembly is possible. Furthermore, the intent is to reduce any kind of undetachable connections between building elements so enabling easy repair and replacements as well as reuse. In terms of materials, the facade is intended to be covered by carbonized wood. The structural as well as other interior components are made from wood. For core as well as the basement of building due to fire safety and resistance against humidity low carbon concrete is chosen. Furthermore, triple glazed windows are used. Since acoustic concerns can arise in offices, wooden acoustic panels can be easily integrated in the rib-like ceilings. Additionally, carpet can be used to reduce the noise level. The indoor environment is improved due to reduction of possible glare. This is an additional advantage to the solar facade which due to the South facing eliminates windows on the southern facade. As a result, West, East and North facing windows as well as North facing rooflights are used.