Aeropolis II was at its conception the biggest passive office building in Benelux. In 2007 it became one of Brussels Exemplary Buildings by the IBGE, not only because it is passive, but because it is passive and reproducible. The techniques used can be easily implemented in new and retrofit buildings. The architects are looking into how to use the same construction model for new projects. The main motivation was to increase the occupants’ well-being and demonstrate feasibility, as well as long-term asset value considerations. The main challenge was implementing a common working procedure with respect of budget and deadlines.
The main innovative features are for example the triple glass front, the exterior solar protection reducing incoming heat, the earth-air heat exchanger, automated windows for cool air in the night. Although those techniques aren’t “new” in a common sense of view, the application in an office building (and therefore a green change in this sector) is innovative.
The outcomes are astounding: the corrected gas consumption for heating is 20 kWh/mÂ².year, whereas the electricity consumption is 49 kWh/mÂ².year. Much less than in a standard office building.
Type: Commercial, new built
Size: 7,400 m2
Year of realisation: 2010
- 90% less heating costs (compared to standard office building)
- After evaluation, on-site numbers:
- gas consumption for heating = 20 kWh/mÂ².year
- electricity (all included) = 49 kWh/mÂ².year
- Savings annually: 451 ton CO2
- Limited extra costs (2-4%), return on investment: 5 years
Design: Architectes AssociÃ©s
For the designers it has been important to use ecological, certified and native materials (FSC certified wood) and realize a flexible use of space. Equally important was the reduction of the finishes. Reduction of suspended ceilings, inner finish of prefabricated facade frames included and reduction of plaster rendering (painting concrete) were one of the many aims. Still, the architects are very strict about one aspect: the ecological footprint is very important but you have to stay in between the technical and economical limits. That’s why it is so important to take the energy, necessary for production, fabrication, transport, maintenance and recycling into account when choosing the materials. The inside walls can be moved- that means that the building can be used for different purposes and is unlikely to turn into something useless which has to be demolished. Also the rainwater is recovered.
Energy — Insulation
- Airtight walls and roof;
- Exterior solar protection;
- Reinforced insulation.
Aeropolis achieves its exceptional passive qualities through the use of airtight walls and roof, triple glazing, solar protection and reinforced insulation. Large wood frames with Rockwool guarantee a perfect insulation. The window surface is reduced to 29% of the total window surfaces. The windows with triple glazing are of variable widths and exterior solar protection reduces the incoming heat (less cooling). Still, there is enough daylight entering the rooms (22% -> less electricity consumption).
The compact construction of the building, build around a central core, reduced energy loss. The structure is made of concrete to use the thermic feature of it. The faÃ§ade consists of FSC-certified wood — there are two different types: the wooden skeleton is framing the layer of isolation or the triple glazing. A boiler of only 140 kW is used for the entire building.
Energy — Ventilation
- Earth-air heat exchanger;
- Automated windows for night ventilation;
- Heat recovery on hygienic ventilation.
It is also equipped with a â€˜Canadian well’ system (earth-air heat exchanger), which uses the latent temperature of the water table some meters below the ground to add heat to the building in winter, and cool it in summer. During the day the concrete structure absorbs the heat produced in the workspaces. During the night the free cooling/ ventilations cools the concrete and delivers fresh air trough automated windows. Because of the low heating demand it is possible to heat the building using simple the ventilations system.
The full budget was 11,5 million euro with limited extra costs (due to the sustainable measures) of 2-4% and with a return on investment of 5 years. The extra-costs have been necessary because of modifications following fit-out requirements received late from the client. Looking at the financing aspects, the project could be realized thanks to a bank loan and subsidies from local authorities. Financial support of 100 euro/ mÂ² was granted (sustainable measures). Huge investments were made to fulfil the sustainable and ecological objectives (reducing energy demand and the use of not renewable energy).
This project started with an architect competition with very different objectives. Originally, the building was not designed to be passive, but the architecture firm that won the project proposed a design change that would reach passive standards. According to the architect Sabine Leribaux there have been two driving factors: the client needs and the technical know-how to meet those needs. Building the house in passive style was evident to them and they wanted to go a step further by going “green”. The use of timber instead of aluminium for the facade structure seemed innate.
A very important factor was the motivation of all parties involved. Priority is given to energy reducing architectural design techniques and best in class renewable materials. Major financial efforts are made to achieve a highly effective, completely prefabricated, thermal insulating envelope.
The key milestones have been convincing the client to go passive, getting the permits from the local authorities who have been very supportive, finishing the tender documents with a specified underground heat-exchanger composed of standard concrete sewer piping, getting a bid within the budget and actually finishing the project with everything functioning well (like automated windows and blinds, the BMS-links etc.). Also the collaboration in design phase and during the construction and the aspect “learning by doing” and learning from each other has been important.
But there have also been obstacles. The architects put forward that the project came in two months late and was 3% over budget due to passive measures (drawings had to be redrawn to accommodate the late implementation of passive measures including the ventilation diagram and fit-outs).
- Flexible use of space (e.g. rooms can be transferred to a meeting room and vice versa);
- Combined use of different sustainable technics and methods (triple glass front, exterior solar protection reducing incoming heat, earth-air heat exchanger, automated windows for cool air in the night, etc.);
- Techniques are easily reproducible and integrated in new and retrofit buildings (the architects are now developing the prefab wooden facades in further projects, like the ELIA Nearly Zero Energy Building and Brussels GreenBizz, an environmental business incubator).
- Looking at the financing aspects, the project could be realized thanks to a bank loan and subsidies from local authorities. There have been limited extra costs (2-4%) with a return on investment time of 5 years;
- An Integrated Design Process has been used which formed a critical part of the project. After designing, the plans have been altered multiple times during realisation. Support and participation of all project members at all times is one major reason this project has been successful.
- The architects put forward that the project came in two months late and was 3% over budget due to passive measures (drawings had to be redrawn to accommodate the late implementation of passive measures including the ventilation diagram and fit-outs). Lessons learned include the necessity of greater communication, more thorough tender documents and simplified faÃ§ade logistics.