The Ecoffice project is the result of a research project aimed at erecting a passive and sustainable tertiary building, labelled BREEAM, at the same cost as standard offices
- This pilot project led to the construction of a passive and sustainable office building at the same price as a conventional building
- The design of the structure, the technical installations and facades aimed to preserve the greatest flexibility possible in the use of the space
- In the development of the architectural approach of A2M, the passive system is naturally associated with the rationale of the building’s life cycle
Sebastián Moreno-Vacca & Aline Brander
Both architects, Aline Branders is Master in Architecture and Sustainability. Research & Development partner of A2M. Sebastian Moreno-Vacca is founding partner of A2M. University professor.
Large construction companies are obviously interested in the passive standard, which is considered more as more as the first indispensable step for the development of their activities towards Nearly Zero Energy construction[i].
Nevertheless, it often still costs more than traditional construction at this time. Under the aid provided to innovative Walloon companies by the 2.Green Marshall plan, Thomas & Piron succeeded in putting together a consortium of architects, engineers, researchers and companies to study the optimisation of all the parameters of a tertiary passive project “in vitro” and in detail.
This pilot project led to the construction of a passive and sustainable office building at the same price as a conventional building. This “passive for all” project is described in detail on www.ecoffice-building.be
The “ecoffice” project is the result of a research project aimed at erecting a passive and sustainable tertiary building at the same cost as standard offices. It is certified passive and labelled BREEAM «Very Good »[ii] for its sustainable construction qualities.
Origin of the project
The future tenant of the project, the firm Holcim, wanted to have the building erected near the headquarters it occupies at present in the Parc des Portes de l’Europe in Nivelles, near the E19 motorway. The operation of the company actually requires such proximity to the motorway and the use of the car. The 76 bus connects the business estate with the City of Nivelles, however.
The project was erected on a plot, facing North-South; it uses the existing slope to separate the building from its parking facilities. The remarkable trees were preserved and integrated in the project.
Starting with a simple, compact rectangle, the shape is divided lengthwise to form two strips, which were shifted to improve the penetration of natural light in the core of the platforms. This objective was reinforced further by an atrium. As such, the blind core (where the sanitary facilities and vertical circulation systems were situated) was reduced for the benefit of the space round the offices.
Functionality and size
The design process included energy and lighting aspects from the outset. All the work areas thus get natural light, which leads to operating savings.
The design of the structure, the technical installations and facades aimed to preserve the greatest flexibility possible in the use of the space. The size was optimised and corresponds to levels of ± 1,000 m², which are appropriate for the landscape arrangements and for the cell offices.
The party retained the North-South orientation, reducing the East and West sides (which are the most difficult to control in terms of overheating). The North and South facades correspond to the same openings (distributed in semi-arbitrary manner), but the side facing north is slightly more glazed than in the south. On the façade, a play of colours forms a set of oversized pixels that echo the accents of the landscape.
Search for optimisation
The project is unique because all its parameters were studied systematically and optimised by the partners so as to make it a reproducible, flexible and multi-purpose model. The search was geared to determining the optimal outcomes between functional imperatives, technical choices, economic criteria and the principles of sustainable construction.
The parametric study focused on constructional, energy and environmental aspects, through themes as varied as the general establishment and form of the building, the structure and choice of materials, level of insulation, performance and choice of technical installations, and matters concerning lighting, natural light, etc.
A monitoring procedure was moreover implemented by the CSTC: it started with the monitoring of future occupants in their current offices and will be continued for 3 years after their move in the new offices.
Construction and energy
The building is erected with a concrete structure and closed by filling with traditionally built concrete breezeblocks. External insulation in Neopor® EPS was then applied and coated. The gables are covered with brick cladding.
The building meets the passive standard with walls that have U values between 0.17 and 0.23 W/m²K. The windows are equipped with triple glazing in the north, but double glazing in the south.
The ventilation is dual flow, of course, and the wheel exchanger is used to adjust the humidity. The inertia of the construction is capitalised on thanks to partial false ceilings in the office areas.
In the development of the architectural approach of A2M, the passive system is naturally associated with the rationale of the building’s life cycle. It has led architects to focus on the particular sustainability of structures, walls and partitions. Reducing the technological aspects for the benefit of architectural aspects was a paradoxical challenge, which got them to focus on ever more structured, low tech energy, relying less on technologies. It is in this connection that they adopted the rationale of the Trias Energetica – “less, better, otherwise,” -- which requires reducing first the needs (of energy, but also of surface, materials, water, etc.) by work on the form and on the material, before considering improvements to the technical systems and resorting to other forms of resources (renewable, etc.).
The work on the erection and form of the building led to the optimisation of natural light while reducing heat losses. The optimisation of solar gain, natural lighting and ventilation needs made it possible to reduce the heating needs in winter and the overheating risks in summer.
Comfort and technical choices
The initial choice of a light structure was abandoned for a heavy one due to its inertia and mechanical resistance qualities, but also for its reduced cost with a comparable environmental impact.
Particular attention was paid to the comfort of the occupants, as a guarantee to the proper use of the building. To enable regulation on an office by office basis, heat is distributed in a traditional hot water system and extra heating is provided by a gas condensing boiler. The ventilation system is oversized to ensure the necessary flow rates of intensive ventilation at night in summer and a cooling unit is provided as backup in the event of heat waves. The lighting installations are optimised thanks to the choice of low-consumption devices properly positioned and an adjustment of dimmers and presence sensors.
The passive certification and BREEAM “Very Good” label attest to the efficiency of the solutions selected and the sustainable character of the building.
The cost of the construction comes to €1,100 / m² (exclusive of VAT, exclusive of fees).
Performances and reality check
The building in question has been built in Nivelles to promote passive offices and has a Very Good BREEAM certification.
The design and engineering firms involved attached the dynamic simulations to the bill of specifications for the work, and the installation and programming work was carried out in accordance with these parameters. After a few months of operation, the building started showing a number of disparities with the simulated results. Over a 4-month period, the occupant increased the heating setting from 21°C to 23°C . This led to a post-acceptance fine-tuning period during which settings have been slightly modified. The monitoring also revealed further relevant information, such as the possibility of losses in the heating network, the imminent failure of one of the post-heating units, etc.
The designers are continuing to monitor the building's performance, and could possibly remain on-site for a total of two years. The readings and the feedback from the occupants are now being regularly checked against the simulation results, thereby helping the maintenance team to fine-tune the building management system. Should the occupant make any significant change to how he uses the building, the maintenance team, associated with the project right from the start, is now able to adapt the building's behaviour accordingly. This commissioning, although only in a "light" version, shows that a building that has been optimised in line with its real-life use and its occupants is able to meet the energy efficiency and comfort targets defined in the design phase.