Function | Educational/Office - Regional business hub for East Anglia University

Location | University of East Anglia, Norwich Research Park, UK

GIA Area | 3,400 sqm

Timeframe | November 2013 to June 2015

Client | Adapt Low Carbon Group/UEA

Architect | Ben Humphries, Christian Dimbleby. Gareth Selby, James Todd at Architype

Cost | £11,600,000

Certification | Passivhaus Standard, BREEAM Outstanding

Just under 30 miles from the coast, west of Norwich, this highly sustainable building is located on the East Anglia University campus, between Earlham Park and the Memorial Garden to the west, and the University Sportspark to the east. The campus is on the outskirts of the city, with residential areas to the north, east and south. The River Yare forms the west boundary of Earlham park and passes near the University of East Anglia Broad to the south of the campus.

This new built and its landscape are exemplary in the use of local natural and bio-renewable materials. “This is the 1st international building to offer Passivhaus performance alongside renewable materials” (Architype, 2020). The building is designed to enable its energy efficiency and carbon offsetting to be monitored. Materials throughout the building can be replaced and are exposed to show how they have been used. 

The Enterprise Centre building was designed to achieve a 100 year design life, Passivhaus certification and a BREEAM Outstanding rating. The level of embodied carbon  - 216 kgCO2e/m2  - is approximately 1/4 of that of many new university buildings (Taylor, 2015). Furthermore, landscaping was fully part of the scheme, the goal being to strengthen the connection to the historical context.

Key design features include locally sourced timber frame, 70% Ground Granulated Blast-furnace Slag (GGBS) concrete slab (reclaimed from locally demolished buildings), carbon negative thatched exterior cladding panels (locally sourced), mechanical ventilation with heat recovery (MVHR), triple glazed windows, water-saving sanitaryware, biodiversity features, Zero VOC indoor finishes and adaptable shading.

The environmental approach to designing the Enterprise Centre was holistic, and considered the structural frame, the provenance of the materials together with  lifecycle and embodied carbon. Passivhaus Planning Package (PHPP) software was used to simulate design options throughout the process and establish the best solutions to various challenges encountered. This contributed to the Passivhaus certification of this project.

FORM

The form of the building takes into account the site and sun orientation. It considers access (east), facilities (east and north), prevailing winds (south-westerly) and interesting views (west). The two main aisles of the E-shaped building are narrow enough to optimize the use of daylight.

TRANSITIONAL SPACES

All three main entrances to the east, north and south have a vestibule allowing for a transition between external and internal environments. These act as buffer zones between indoor and outdoor temperatures.

STRUCTURE

The building’s primary superstructure is made of timber, a renewable material, and was sourced as locally as possible (in Suffolk and Austria) to reduce the carbon footprint and contribute to the local economy. The primary substructure’s concrete raft contains 70% of GGBS, lowering the embodied carbon (“38% embodied carbon when compared to ordinary concrete of comparable mix” (CIBSE, 2015)). The raft’s sub-base was salvaged from the demolition of a local hospital.

ENVELOPE

The envelope is carefully designed to be thermal bridge free and with very high levels of insulation and airtightness, in line with the Passivhaus standard. The building is three times more airtight than the level required for Passivhaus compliance, with an airtightness of 0.21m³/m² at 50Pa. The continuous layer of insulation starts with prefabricated modules of Isoquick raft insulation, reducing installation waste and time. These have special edge pieces providing for a good junction with the walls. The external walls and the roof have over 300mm insulation.

The overall building and the south facades of the courtyard are extensively glazed to maximise thermal and daylight gain, while the north facades have reduced apertures for thermal control. Passivhaus approved triple glazing was used throughout. All outward facing facades, with the exception of those south facing, are cladded with thatch cassettes which add a level of weather protection to the envelope.

From an acoustic perspective, the building has no openings on the busiest side of the site (along University Drive), apart from a couple of exit doors, and the walls covered with thatch, which also has good acoustic qualities.

MATERIALS

Materials play an essential role in the environmental strategy of this project. The choice of local natural and bio-renewable materials contributes to achieving its Passivhaus performance and the exceptionally  low embodied carbon level of 216 kgCO2e/m2.

The use of thatch and straw panels was innovating while celebrating local vernacular architecture. The use of straw, a carbon negative material,  helped achieve the BREEAM Outstanding accreditation.

CLIMATE CONTROL SYSTEMS

The building’s heating and cooling systems make use of natural ambient conditions as much as possible, with the use of overhangs and adaptable shading systems (brise soleil) on south-facing facades. Cross and stack ventilation strategies were implemented, together with clerestories, and a Passivhaus certified mechanical ventilation system with highly efficient heat recovery (MVHR, Swegon GOLD). The windows are set back in order to accentuate shading. What little thermal mass this building has to store the heat is mainly to be found in the diamond polished concrete floors.

RENEWABLES

480 m² of Bauder solar photovoltaic panels are laid across the roof, thereby exceeding the requirement for 10% renewable energy. “31.9% of the building’s electricity comes from renewables” (UKGBC, 2020). Furthermore, rainwater is collected and reused for sanitary purposes.

SERVICES

LED lighting is used throughout the building in conjuction with an intelligent control system. The primary energy demand is kept below 120kWh/m²/y, which meets the Passivhaus standard.

BIODIVERSITY

Biodiversity features such as insect hotels, bat and bird boxes and the display bed terraces enhance ecological value. (Architype, 2020)

The main drive for the choice of structure was the environmental impact of the building. In order to achieve a low-embodied carbon construction, the design team chose, where possible, local PEFC or FSC certified timber to reduce transport costs and support the local economy, while making a durable choice. The use of prefabricated glulam beams and columns helped to enable the primary structural frame to be built quickly and in clean conditions.

PRIMARY STRUCTURE

The primary structure of the Enterprise Centre is comprised of lightweight timber on reinforced concrete raft foundations, to suit the poor ground conditions. The rafts (under the lecture theatre and the rest of the building) enable the load to be spread from the timber structure over the area of the rafts.

The primary substructure is composed of sub-base aggregate (100% recycled from a local hospital demolition), Isoquick insulation, which is a water-resistant polysterene foam boards system, topped with a reinforced concrete slab that was diamond polished as an interior finish. The insulation is designed specifically for rafts, with a profile that facilitates the installation of the boards and improves the stability of the structure.

The reinforced concrete slab is made of 70% recycled GGBS which allows it to have “38% embodied carbon when compared to ordinary concrete of a comparable mix” (CIBSE, 2015), and the reinforcing steel is 98% recycled.

The primary superstructure consists of glulam (glued laminated timber) columns and beams, together with CLT (cross laminated timber) at vertical circulations (lift and staircases). 

SECONDARY STRUCTURE

The secondary structure includes stud-work, of which 70%  was sourced from within 30 miles of the site (Architype, 2016), timber curtain wall mullions, insulated I-joist walls, floors and roofs as well as the brise soleil structure for the south facades.

The services for the Passivhaus buildings tend to be more limited than for other buildings because one of the core principles is to reduce the needs for mechanical heating and cooling to a minimum.

HEATING

A custom built heat interface unit is linked to the University of East Anglia’s district heating and its combined heat and power network.  Two heat exchangers are incorporated in the heat interface unit for heating and for hot water. However due to the shape of the building and the location of the heating mains and interface, one of the toilet’s hot water had to be topped up with “point-of-use local electric water heaters”. (CIBSE Journal, 2015)

Additionally, in this airtight building, the thick insulation, careful massing and orientation allow natural solar heating. This is an important part of the heating strategy for the building. As mentioned previously, to ensure there was enough thermal mass to store the heat and redistribute it slowly into the rooms, the ground floor concrete raft was left exposed  (diamond polished finish). 

For the lecture theatre, which seats 300 people, an air handling unit (AHU) was also fitted to ensure the temperature remains comfortable. From the AHU (which has a cooling coil with condensers in exhaust air ducts). air is ducted to the floors and distributed through variable air volume units in the services distribution bulkhead (red volume above the theatre plantroom). The bulkhead is also used as an attenuated return air plenum. 

LIGHTING STRATEGY

With the aim of keeping the primary energy demand below 120kWh/m²/y, the building is has LED lighting controlled by an intelligent system to keep lighting loads low. The ambiant and task lighting by Fagerhult and Swegon was chosen for its ergonomics, sustainability conscious production and energy efficiency.

COOLING & VENTILATION

Three mechanical ventilation heat recovery units (MVHR) (Swegon Gold RX Passive House Institute certified) using thermal wheel are installed in the building. The plantrooms where they are located are in each aisle and in the lecture theatre (shown in orange on image 20, p.15). Fresh air is supplied to all rooms in use and stale air is extracted from wet rooms, mechanically and at a continuous rate. The amount of heat loss in the process is reduced by a heat exchanger that pre-heats the incoming air supply with the warmth of the extracted air. The ducts transporting the air are located in the horizontal service zones (in red and darker red on image 20, p.15) or air plenums between the dropped ceilings and the I-joist structure.

To avoid overheating in this timber building with limited thermal mass, room heights are around 3.3m, which helps create sufficient volume to mitigate temperature rises. A cross ventilation system is also in place with the clerestories windows and ventilation flaps (behind aluminium louvred panels) allowing an air flow to move hot air out and cold air in during hot periods. Both occupants and CO2 sensors control the ventilation system. Therefore, there is no cooling for the main floor areas. For ventilation in the toilets, air is extracted from the aisles, transferred through the thermal wheel and lead outside without any extractor fans.

In order to significantly reduce the embodied carbon of a building, a palette of materials that are more energy-efficient than steel or “standard” concrete must be used. The materials for the Enterprise Centre were selected for low-embodied carbon, proximity of source and, natural and pollutant-free qualities.

Achieving low embodied carbon is particularly difficult when specifying the foundations for instance. For the Enterprise Centre, owing to geotechnical constraints (AJ Specification, 2015), it was necessary to use a reinforced concrete slab rather than the small concrete pads initially envisaged. The resulting increase in embodied carbon was mitigated by using 98% recycled steel, locally sourced aggregate and by replacing 70% of the cement in the concrete mix with ground granulated blast-furnace slag (GGBS). GGBS is a “a sustainable by-product of the steel industry that improves the durability of the concrete with increased ratios” (Passivhaus Trust, 2015). The sub-base is composed of aggregate reclaimed from a local demolished building on top of which Isoquick, a strengthened interlocking polystyrene system, is added. The latter was specified as part of the thermal envelope design. (ibid) The raft foundation was manufactured off-site to reduce waste.

Another important aspect of the material specification is the internal finishes. A palette of environmentally friendly and non-toxic finishes was specified as part of the Passivhaus requirements for interior comfort and as a key factor for the wellbeing of the building’s users. The selection includes timber slatted ceilings, recycled car tyre flooring, natural wall coverings, and a linseed and hessian linoleum.

Often described as “the UK’s greenest building”, the Enterprise Centre certainly demonstrates the potential that exists in building large scale projects with a holistic and systematic approach that benefits the environment, the users, the industry, and the local community. Not only was every aspect of this project considered technically, to optimize thermal insulation, airtightness and, the construction process, but it was also designed to minimize the embodied carbon, the transportation and increase the potential for modification or demolition. This building was designed looking at the past, the present and the future.

Testimonials highlight the comfort and fluidity of the building. The design has kept the user in mind throughout, and this reflects positively on the direction architecture and Passivhaus design seem to be heading.