Study Tour: Bicester Eco Business Centre

The Passivhaus Student Competition, sponsored by Tarmac, is well underway, and some participants took the opportunity to visit a commercial development currently under construction that is aiming for a Passivhaus first in Bicester. When completed Bicester Eco Business Centre (BEBC), will become the first commercial building in the UK to achieve Passivhaus Plus standard. The 1147m² building will form a significant landmark in Elmsbrook’s new zero-carbon northwest Bicester Eco Town.

Bicester Eco Business Centre presented itself as an ideal project to attempt the new Passivhaus Plus standard. The combination of a dedicated client with a wider environmental agenda, coupled with an appropriately experienced design team and contractor, has made us confident that we can take the design to the next level and meet the new standard.

Lee Fordham, Architype

Passivhaus was not originally in the clients brief. They aspired to create flexible rentable office spaces for up to 125 people in a building that was zero carbon in use, low in Volatile Organic Compounds (VOC’s) and achieve BREEAM excellent. Outline planning had already been granted when Architype were appointed. However, after initial feasibility studies and a few tweaks from an L-shape plan to a more efficient building form, it was clear that the building had potential to meet Passivhaus Plus standard. The client was convinced of adopting a Passivhaus approach as it not only reduces energy demand, carbon emissions and the number of PV's required, but thanks to the evidence shared on costs & indoor monitoring that Architype have gathered from previous Passivhaus schemes.

Architype & Kier collaborated on the Hereford Archive & Record Centre (HARC) which achieved Passivhaus certification. The team are applying learned skills, knowledge and experience from that successful non-domestic scheme to this new project, but this is the first Passivhaus Plus for all involved.

Passivhaus Highlights

Construction & Materials

The building adopts a hybrid construction system that consists of an elegant concrete frame & timber larson-truss infill panels, insulated with warmcell. Breathable walls & non-toxic natural materials are championed inside and out to meet the clients goal of creating a healthy work environment. Exposed internal concrete columns, and a custom-cast concrete stairwell simplifies the whole finishing material palette, whilst also providing thermal mass that helps the building regulate its thermal environment.

Favourable form

Bicester Eco Business Centre: Hybrid construction The 3-storey simple rectangular form creates an efficient form factor and simplifies achieving continuous insulation to minimise thermal bridges. The layout remains simple but flexible with various sized offices, meeting rooms, break-out spaces, hub space and additional office facilities. Bicester Eco Business Centre

Airtightness & services

Students learned that the airtightness layer is located on the inside of the thermal envelope. The timber infill panels are taped directly to the concrete frame, using several tapes with various adhesives to ensure a good fix. The main building entrance is designed with a double door lobby to help minimise excessive heat losses.

Bicester Eco Business Centre

Learning from their previous Passivhaus scheme, Keir have designated an overall on-site airtightness champion. Frequent on-site meetings between contractors, designers & consultants has helped plan & minimise service penetrations through the building fabric and optimise construction sequencing to assure airtightness details. The plant room is strategically placed close to the main stairwell which acts the main service run vertically up the building, and distributed horizontally through floor voids.

Natural Light & Shading

One of the buildings key features is a triple height top-lit atrium space, allowing daylight into the depth of the plan, and reducing excessive use of artificial light and energy. Each of the 24 rooflights will be triple glazed units, and a few will be openable to help with cooling when necessary.

Externally, vertical timber fins not only give the building a unique identity, but act as a large Brise-soleil that reduces unwanted heat gains in summer and provides solar shading. The fins are supported by an external steel frame and made from European larch that will weather naturally.

Bicester Eco Business Centre

Street view render ©Architype

Bicester Eco Business Center elevation BEBC North Elevation ©Architype

Energy Generation

The fabric-first approach is bolstered by a renewable energy strategy so that the building will generate as much energy as it consumes; The whole roof is covered in PV panels and heat will be supplied from the local direct gas district heating system which is located opposite the road. To meet the Passivhaus Plus standard, the building will generate as much energy as the building consumes. The predicted building energy demand is ≤45 kWh/(m²TFAa.)

Bicester Eco Business Centre

BEBC Site Plan ©Architype

The 51-week programme is due for completion & handover in August 2018. The Trust look forward to returning once the scheme is complete. Many thanks to Architype & Keir for facilitating the study tour.