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| Photos: Paul Riddle |
Daylighting and natural ventilation form an integral part of the Lincoln Innovation Centre.
The Lincoln Innovation Centre by Marks Barfield Architects is a £7.1m flagship building that is designed to attract and support high value, science-based businesses. Located on a brownfield site adjacent to the University of Lincoln, the 3200 square metre project comprises 22 offices and nine light industrial units serviced by a shared entrance/reception, conference facilities, and a reprographics suite.
One of the principal objectives for both the client and the design team was to create a sustainable low-carbon building using a combination of passive and active technologies. Central to this approach has been the use of sun pipes and windcatchers from Monodraught. The former ensure good levels of glare-free daylighting, while the latter provide a controllable source of natural ventilation as well as night-time cooling. Not only are the systems reliable and cost effective, they also act – along with an exposed concrete frame and green roof – as clear visual indicators of the scheme’s environmental intent.
Intended as a catalyst for the redevelopment of the 41-hectare Brayford Enterprise Park, the Lincoln Innovation Centre, or Think Tank, originally formed part of a feasibility study undertaken by Carey Jones Architects for Lincoln City Council in 2004. Marks Barfield responded successfully to the OJEU in October 2005, and began developing the scheme in January 2006. The project started on site in Autumn 2007 and was completed in December last year.
The brief was for a flexible and stimulating working environment that would encourage social interaction and the cross- fertilisation of ideas. The building also had to incorporate a range of shared resources, respond sympathetically to the local context and be environmentally friendly.
The ground floor comprises two abutting wings, running east-west and north-south respectively. The former houses the industrial units, while the latter accommodates the entrance/reception and the main support spaces, including a social hub where tenants and other building users can meet informally. A third bridge element is introduced at first-floor level, linking the two wings and creating a triangular-shaped courtyard. This arrangement allows not only natural light down into the ground floor, but also the external landscaped space to flow into the centre of the building. The first floor is given over to offices and meeting rooms of varying sizes. An external terrace located at the eastern tip of the plan reduces the massing of the scheme towards a proposed residential development, while also providing a further informal meeting place.
In terms of sustainability, the team decided to adopt the targets for the Energy Efficient Office of the Future produced by the Energy Efficiency Best Practice programme. This included limiting carbon dioxide emissions to 30kg CO2/m2/yr or lower, and reducing energy consumption to 80kWh/m2/yr or less. The building is highly insulated and has an airtightness of 4ac/hr/m2 at 50pa – exceeding current building regulations by around 60 per cent. The structure comprises an exposed concrete frame containing 50 per cent basaltic pumice slag. Trough-like soffits maximise the surface area of the floor slabs which, in combination with night-time ventilation, results in passive radiant cooling. Around 70 per cent of the building’s heating needs are provided by a ground source heat pump, which is linked to an underfloor heating system. Hot water is supplied by roof-mounted solar thermal panels.
The massing and orientation of the building is designed to maximise natural ventilation and daylighting. The dual-aspect nature of the ground-floor spaces meant that adequate cross ventilation could be achieved using a combination of opening windows and vents. However, the predominantly single-aspect first-floor offices and meeting rooms required a different approach. The solution was to use Monodraught’s Windcatcher system of ‘topdown’ ventilators. The roof-mounted GRP units are designed to catch the wind from any direction – using a series of external louvres linked to internal turning vanes – to introduce a controlled rate of flow in while simultaneously expelling warm air through the same route as a type of displacement ventilation.
Project architect Gemma Collins says the largest consumer of energy within a sustainable office development is artificial lighting. The two-storey nature of the design allows rooflights – in this case 230mm diameter SunPipes – to daylight the rear areas of the offices, boosting natural lighting levels by up to three times. On the north elevation, full-height glazing is combined with a sawtooth-profiled facade to maximise natural lighting while minimising solar gain. Windows on the east and west elevations are shaded respectively by horizontal and vertical larch timber louvres. Last but not least, the building is topped with a green roof that is planted with species to resemble a Lincolnshire meadow. This not only promotes biodiversity and air quality, but also increases insulation and controls rainwater run-off.
Windcatcher specification
The architect’s original intention was to design a bespoke rooftop ventilation and daylighting solution for the single-aspect first- floor spaces, but tight budgetary constraints combined with design and build procurement rendered this unfeasible. The decision to use Monodraught Windcatchers and SunPipes was taken following recommendations by the main contractor Marriott, who had successfully used the systems on previous projects. Among the advantages offered by Windcatchers are that they can be designed and sized to meet the exact needs of the spaces; they can provide effective and secure night-time cooling – one of the main tenets of the scheme’s natural ventilation strategy; and they are inherently reliable, being designed to operate at comparatively low wind speeds and containing few moving parts (none externally). The Windcatchers are also functionally expressive and can be clearly seen from the buildings surrounding the site.
The manufacturer produced a natural ventilation proposal indicating the preferred dimensions and specification of the Wind-catchers for each area of the building (a total of 32 units were specified). In terms of sizing, the approach taken by Monodraught is to recommend a system that will provide the requisite number of air changes at a wind speed of 2-3 metres per second. The Met Office suggests that the average UK wind speed is 4-4.5m/s throughout the year, hence sizing below this gives a good assurance that the desired airflow will be achieved even at low wind speeds. The air change rate is based on factors such as room size, occupancy, and predicted heat gains from windows, artificial lighting, electrical equipment etc. To ensure best performance, even on hot sunny days with little or no wind, it was decided to specify the Sola-boost Windcatcher model throughout. The units feature a 40W polycrystalline solar panel mounted on the truncated top capping. This drives a high-efficiency fan that can be used to bring up to 260l/s of additional fresh air down into the building or extract stale, warm air.
The smaller offices, measuring approximately 45 square metres, are served by single 600mm square ventilators, while the larger offices and meeting rooms, measuring up to 70 square metres, use a combination of single and paired 800mm square units. Added to this, a 1200mm Sola-boost Windcatcher was chosen for the ground-floor reception/hub area. The units were specified in a light grey finish.
Installation and commissioning
The roofing contractor formed the structural apertures and then fitted insulated metal aprons ready to receive the ventilators. Installation was carried out by Monodraught following completion of the preparatory work. Fixed to the base of the ventilator trunks are motorised damper assemblies (used to control the airflow) and white eggcrate diffuser grilles. The Windcatchers are automatically controlled via the building management system (BMS). They are connected to the system using bothtemperature and carbon dioxide sensors positioned on the internal walls of the rooms. Readings taken from the sensors determine the degree by which the dampers are opened or closed. Under summer daytime operation, temperature and CO2 levels dictate the amount of ventilation required. The dampers start opening at 16°C and then open further in increments of 20 per cent for each additional degree rise in temperature. In terms of carbon dioxide, the room sensor is set at 1500ppm. If this level is reached, the dampers automatically open for 20 minutes before returning to the closed position.
In the summer when night-time cooling is required, the dampers open fully between midnight and 6am. This has the effect of purging the building of warm stale air, leaving it cool and fresh for users in the morning. A minimum temperature limit can be programmed into the system to ensure the building is not over-cooled. During the winter, the dampers can be closed or set to five per cent trickle ventilation. A manual override located on the sensor allows building occupants to fine-tune comfort levels and/or respond to unusual weather conditions. The override is linked to a timer, which re-sets the system to its pre-programmed settings after a specified period.
SunPipe specification
Some 49 SunPipes were specified for the rear areas of the offices and meeting rooms, as well as the corridors. Designed to intensify and reflect daylight and sunlight from the roof down into the building, each 230mm diameter unit comprises a silverised mirror-finish aluminium tube capped by a polycarbonate diamond dome.
At the base of the fitting is an opal diffuser, designed to give an even spread of light. The main appeal of the system was its effectiveness in both sunny and overcast conditions, its ability to save energy and cost, and its durability/vandal resistance. Installed by Monodraught, each unit is fixed to an insulated galvanised steel upstand, with a brushed nylon condensation trap positioned between the dome and the collar.
Project team
Architect: Marks Barfield Architects; structure: Jacobs; m&e: XCO2 (up to RIBA stage F); project management, cost consultant: Thornton Firkin; main contractor: Marriott; client: City of Lincoln Council.
Selected subcontractors and suppliers
Passive stack vents, lightpipes: Monodraught; rainscreen cladding: Rockpanel; facade contractor: SBS; green roof: Bauder; internal doors: Leaderflush Shapland; windows, curtain walling: Acorn Aluminium; Komfort internal glazing: Butler & Willow; cubicles: Amwell; sanitaryware: Armitage Shanks, Grohe; paint: Johnstone’s Paint; linoleum: Altro; carpet: Tessera; Blanc de Bierges courtyard/entrance paving: Cathedra Stone; Sintra quartz cafe floor tiles: Focus Ceramics; car park paving: Marshalls.
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