Heelis
The Central Office for the National Trust, Swindon

Building Team

• CLIENT: THE NATIONAL TRUST
• ARCHITECT: FEILDEN CLEGG BRADLEY STUDIOS
• INVESTOR PROPERTY COMPANY: AIM DEVELOPMENTS
• DEVELOPER: KIER VENTURES
• STRUCTURAL ENGINEER: ADAMS KARA TAYLOR
• SERVICES ENGINEER: MAX FORDHAM
• QUANTITY SURVEYOR: DAVIS LANGDON
• PROJECT MANAGER: BURO FOUR PROJECT SERVICES
• ACOUSTICIANS: APPLIED ACOUSTIC DESIGN
• CONTRACTOR: MOSS CONSTRUCTION

Building Data

• COMPLETED: JULY 2005
• NET: 6,942 m²
• GROSS: 7,680 m²
• EFFICIENCY: 90%
• FLOORS: 2
• COST: £11,384,971 TO CAT B

• to be as environmentally friendly as possible
• to be the platform for new, more business-focused ways of working across all functions
• to demonstrate that sustainability, carbon neutrality and low energy usage were achievable within an institutionally fundable project
• to be wholly flexible in use, adapting economically and speedily to business changes.

The architects explored a wide range of technologies, techniques and materials in order to meet the terms of the brief, including a range of ‘good practice’, ‘best practice’ and ‘innovative’ systems. These embraced measures such as heat recovery, the use of non-petrochemical-based insulation materials, providing office spaces with 100% natural light, sourcing building products as locally as possible and using micro power generation. The result, according to a statement from the client, was that ‘the building met and exceeded these aggressive criteria’.

‘The naturally ventilated, daylit working environment is the subject of constant favourable comment by users and visitors … Empiric evidence indicates absenteeism, days off sick, etc. has dropped significantly since we occupied the building,’ said the National Trust, adding that ‘the building is a great place to work’.

Heelis is a low-rise, deep-plan building whose mass, materiality and form show deference to the nearby train sheds which make up Swindon’s World Heritage Site. It is a complex, two-storey

Heelis is A Low-Rise, Deep-Plan Building With A Large, Airy Atrium. The Two-Storey Structure is Fitted with A Wide Variety of Sustainability Measures with A ‘Pay Back’ Period of Less Than 20 Years.

© Dennis Gilbert

affair with a plan designed around solar orientation and the need for a roof which maximises daylight penetration. Photovoltaics, enhanced thermal insulation, lighting controls, mechanical ventilation with heat recovery in winter months, propane chillers (which have zero ozone-depleting potential) as well as a host of other measures combine to create a building with impressive environmental performance.

Heelis, The Head Office of the National Trust. In Its 100-Year History, The NT Had Never Managed to Locate All Its Central Functions under A Single Roof.

© Dennis Gilbert

The mixed-mode, natural/mechanical ventilated building was designed around targets which stated that internal temperatures should not exceed 25°C for more than 5% of working hours; and should not exceed 28°C for more than 1% of working hours. Thermal modelling with TAS software indicated these targets would be achieved, and this has been borne out by experience. Occupant feedback among the Trust’s 470 staff during summer 2005 showed that they remained comfortable during hot weather.

The main office areas are naturally ventilated using a combination of night cooling and exposed thermal mass. Automatic windows are generally at high level with manual over-rides. Floor plates are split into a number of zones to allow local control based on orientation, wind direction and so on. Solar gain is limited since only northlight is allowed through the rooflights, while vertical glazing is provided with external shading. The roof-mounted PV panels also act as shading devices. Mechanical cooling is provided only to the ‘highly loaded’ areas such as meeting rooms. Meeting rooms adjacent to the perimeter use natural ventilation for as much of the year as possible. Windows close when mechanical cooling is operational. The National Trust retained the services of M&E consultants Max Fordham for one year after the building’s completion to monitor its energy use, allowing tweaks to the building management system where necessary.

In addition to the features outlined above, as many materials as possible were sourced from the National Trust’s own estate – timber from NT forests was used in key parts of the building and even wool from Herdwick sheep was used for the manufacture of carpet tiles.

Structurally, the building is composed of a steel frame on a grid of 6 m and 9 m spacings (concrete, timber and hybrid framing systems were also explored). Both storeys contain exposed precast concrete soffits; there are no suspended ceilings. Because of the deep-plan nature of the building, and the requirement to bring a good level of daylight into most parts of the base of the building, the floor-to-ceiling height at ground level is a very generous 3.75 m. Floor-to-ceiling heights vary on the upper storey owing to the pitch of the roof – 2.5 m at valley level to 5.17 m at ridge level. It is worth noting that use of the lift, located adjacent to a grand staircase, is discouraged (apart from disabled users, of course).

Floors are raised to a height of 250 mm, and it is this void that is utilised by the mechanical heat recovery system which operates during the winter. The original intention was to employ a timber-based raised floor system for sustainability reasons, but the developer insisted on using a metal composite product to meet institutional standards.

By common consent, this elegant, innovative and highly contextual project has been a success across a wide range of indicators – not least, according to the architects, because all concerned with the building bought into the same agenda: ‘The key success of the procurement of this building has been in the selection of like-minded consultants, developer, contractor, subcontractors and suppliers. By all working to a common set of clear objectives the Trust has been able to achieve a new operational building that meets its operational, financial and sustainability aspirations.’

Floor to Ceiling Heights are Generous Throughout the Building: 3.75M at Ground Level, and A Range From 2.5M TO 5.17M at First Floor Level, Depending on the Fall of the Roof Line.

© Feilden Clegg Bradley Studios

THE FACADE. NORTHLIGHT IS ADMITTED THROUGH ROOFLIGHTS, WHILE VERTICAL GLAZING IS PROVIDED WITH EXTERNAL SHADES. THE MAIN OFFICE AREAS ARE NATURALLY VENTILATED USING A COMBINATION OF NIGHT COOLING AND EXPOSED THERMAL MASS.

© Dennis Gilbert

Beaufort Court
Kings Langley, Hertfordshire

Building Team

• CLIENT: RENEWABLE ENERGY SYSTEMS
• ARCHITECT: STUDIO E ARCHITECTS
• INTERIOR DESIGNER: BREATHE
• STRUCTURAL ENGINEER: DEWHURST MACFARLANE AND PARTNERS
• SERVICES ENGINEER: MAX FORDHAM
• LANDSCAPE DESIGNER: CAMLIN LONSDALE LANDSCAPE ARCHITECTS
• QUANTITY SURVEYOR: A&S FRIEND AND PARTNERS
• PROJECT MANAGER: KING STURGE
• HEATSTORE DESIGN: SARNAFIL
• ACOUSTICS: HOARE LEA ACOUSTICS
• MAIN CONTRACTOR: WILLMOT DIXON CONSTRUCTION

Building Data

• COMPLETED: AUGUST 2003
• NET: 2,149 m²
• GROSS: 2,697 m²
• EFFICIENCY: 80%
• FLOORS: 2
• COST: £4,213,453 TO CAT A

The brief required that the former egg farm be converted to provide 2,700 m² of flexible office accommodation (as well as lecture and exhibition facilities) by employing best practice sustainable strategies. The project received EU assistance in return for involving a pan-European design and development team. The project team included contributions from the Netherlands Energy Research Foundation, Amsterdam-based Shell Solar Energy and Esbensen Consulting Engineers from Copenhagen. The energy performance of the building was eventually posted on Esbensen’s website.

Studio E Architects had to exercise a series of practical and aesthetic judgements during the design of this complex project. The transformation of farm buildings intended for chickens to modern office space required extensive and radical alteration. However, the existing buildings had to be more or less preserved (at least externally) but the architects decided not to replicate the Arts and

This Project Represents the Conversion of a Former Egg Farm Into the HQ of Renewable Energy Systems, Which Was Provided With 2,700 m² OF OFFICE SPACE.

© Peter Mackinven

Crafts style of the farm for the new structures. ‘The additions and replacements are expressed in a clean, modern, albeit sympathetic idiom, reflecting the contemporary concerns of RES and the leading-edge energy systems deployed over the site and concealed within the buildings,’ said the architects.

The Principal Building Was Extended by Wrapping New Space Within The Courtyard Perimeter. The Roof Of The Extension Was Grassed Over, While The Ends Of The Horseshoe-Shaped Building Were Tied Together To Provide An Entrance.

© Peter Mackinven

Internally, the two principal elderly buildings were considerably adjusted. In the larger horseshoe-shaped building, masonry cross walls which provided lateral stability were removed (and replaced by a steel frame) to open the space up for office accommodation. Also, this building was extended by wrapping a simple ‘lean-to’ structure around its courtyard face, while a single-storey entrance structure was built to tie the ends of the horseshoe together. A coach house was given similar treatment, and an extension was constructed across its courtyard. An entirely new building was built at the perimeter of the site, partly sunk into the ground with excavated earth banked up against its northern wall; this third building provides a store for harvested biomass crops, and the hybrid PV/thermal array sits on its roof.

During the winter, fresh air is warmed by the heat collected from hybrid PV/solar-thermal panels; also, the summer heat collected in the large volume of water on site is released during the colder months, backed up by the heat from the biomass. During the summer, the air supply is cooled and dehumidified with 11°C ground water from a 75 m deep borehole, which also serves chilled beams. A building management system controls and coordinates these technologies and provides data for an ongoing monitoring programme.

First-Floor Office Space. The Horseshoe Form Of The Original Building Can Be Seen From The Curve Of The Wall. Much Of The Exterior Of The Building Has Been Preserved, But A More Contemporary Architectural Language Has Been Applied Where Appropriate.

© Peter Mackinven

The client says that the building has more than met its expectations. ‘Its status as the first refurbished commercial office space to be carbon neutral is very important to the company. We are now working in a highly sustainable space that directly reflects the objects of our business and the natural aspirations of our staff as, almost without exception, we all believe in what we do … The office is expected to have substantially lower running costs than our previous headquarters, with a low energy requirement (approximately half that of a conventional office) and mostly “free” energy. It also has a financial value as a marketing tool, demonstrating the value and application of renewable energy and the skills and vision of the company.’

Lemsford Mill
Hertfordshire

Building Team

• CLIENT: RAMBLERS HOLIDAYS
• ARCHITECT: ALDINGTON CRAIG + COLLINGE
• INTERIOR DESIGNER: ALDINGTON CRAIG + COLLINGE
• BRIEF CONSULTANT: ALDINGTON CRAIG + COLLINGE
• QUANTITY SURVEYOR: NORTHCROFT
• PROJECT MANAGER: ALDINGTON CRAIG + COLLINGE
• STRUCTURAL ENGINEER: WHITBYBIRD
• SERVICES ENGINEER: WHITBYBIRD
• CONTRACTOR: T&E NEVILLE

Building Data

• COMPLETED: NOVEMBER 2006
• GROSS: 1,115m² (MILL AND MILL HOUSE)
• 465 m² (NEW BUILD)
• FLOORS: 4
• COST: £1,957,000

Ramblers Holidays, a sister organisation of the Ramblers’ Association, was in 2003 planning to move from its Welwyn Garden City headquarters. Lemsford Mill appealed because the principal building (the mill itself) provided multiple levels of open-plan space, while a cottage alongside provided more intimate spaces for meeting rooms, library, eating facilities and so on; moreover, the estate also came with planning consent for a number of business/light industrial (B1) units (of approximately 460 m²) which could provide a rental income and space for expansion as necessary. Aldington Craig + Collinge took on the entire project, as well as the landscaping.

What makes this project particularly exciting is that this redundant mill is once again drawing power from the stream which runs beneath it. The original wheel had long since disappeared, but researchers from Southampton University, working with German manufacturer Hydrowatt, designed and installed a 4.2 metre diameter breast-shot waterwheel that provides, on average, 60% of the building’s daytime electricity needs. While soundproofed, the wheel is clearly visible through glazed screens and floor panels.

The architects have also responded elegantly to the awkward topographical relationship between the principal buildings – the mill and the mill house, both Grade II listed and separated by a gap just 1.3 m wide. It made sense to roof this space over and create a new link and circulation zone. However, the floors of the two buildings

Rehabilitated For Ramblers Holidays, The Mill Building And An Adjacent House Are Just 1.3 M Apart. The Mill Is A Very Early Industrial Building With Two Storeys Of Solid Brickwork Topped By A Pair Of Timbered Floors.

© Paul Collinge

have a rather staggered relationship, so designing the new link was far from straightforward; nonetheless, the steps and level changes have been neatly done. The use of galvanised mild steel and frameless glazing allows the original buildings to be easily distinguished from one another, rather than being merely joined.

The Refurbished Mill Contains Primarily Open Space, With Two Transparent Offices, Toilet Pods And Tea Bars.

© Paul Collinge

Most office accommodation has been located in the mill building, which is provided with toilet pods and just two separate office spaces; the cellular spaces of the old house accommodate ancillary functions, while showers are located in the basement. The B1 units (which had to be designed and begun relatively quickly as planning permission was close to running out) have been designed in sympathy with the mill and its house, while being unmistakably contemporary. The three single-storey, highly insulated, timber-framed units are each of a different size to allow potential occupiers a choice of accommodation.

The client also secured permission to build a lodge, a derivative of the B1 concept, to provide sleeping accommodation for staff. The entire estate contains an eclectic range of buildings, but the ensemble is tied together with an intelligent use of materials (including timber boarding) that caused the BCO judges in 2007 to describe it as a ‘rare joy’.

‘All three components [the mill, the mill house and the B1 units] demonstrate a sensitive and sustainable approach which has created a memorable and stylish working environment in harmony with the historic context. It is the sort of place where everyone would like to work,’ said the judges. ‘Linking house and mill has been done with a visual connectivity that belies awkward level differences. … Despite the challenges of the historic fabric, workspaces are well planned and provide a stimulating environment, daylit and naturally ventilated.’

These B1 Units Allow The Client Scope For Expansion Or For Generating Income Through Rent. These Highly Insulated Timber Structures, Clad In Horizontal Feather-Edge Boards, Have Walls Just 180 mm Thick.

© Paul Collinge

The Link Between Mill And House Negotiates An Awkward Change In Levels – The Floors Of Each Building Are Staggered In Relation To One Another. Original Materials Are Deliberately Contrasted With The New.

© Paul Collinge

Skyways House
Liverpool

Building Team

• CLIENT: LITTLEWOODS PROPERTY HOLDINGS
• ARCHITECT: CDA
• DEVELOPER: SJS PROPERTY MANAGEMENT
• STRUCTURAL ENGINEER: CURTINS CONSULTING
• SERVICES ENGINEER: CUDD BENTLEY CONSULTING
• QUANTITY SURVEYOR: CHRISTOPHER SMITH ASSOCIATES
• PROJECT MANAGER: HIGH-POINT RENDEL
• LANDSCAPE ARCHITECT: BARRY CHINN ASSOCIATES
• CONTRACTOR: SHEPHERD CONSTRUCTION

Building Data

• COMPLETED: SEPTEMBER 2005
• NET: 10,783 m²
• GROSS: 12,245 m²
• EFFICIENCY: 88%
• FLOORS: 3
• COST: £15,312,500 TO CAT A AND B FIT-OUT

The Grade II* hangar was built in 1940 as a military facility. It comprises a lamella roof structure, composed of identical steel components arranged to form a barrel vault which sits on vertical columns at the periphery. One of the fundamental principles underlying the project was that the historic structure should be changed as little as possible, and interventions should be removable, leaving the original hangar intact. There was also a structural reason for such a ‘hands-off’ approach – the roof structure was designed purely as a canopy and therefore lacked the strength to support anything but itself. The architects could not blithely suspend lighting and air handling equipment from the structure. ‘The success of the project depended on solving many technical problems in an effective and unobtrusive way,’ said the architects. ‘Those challenges proved to be tougher than everyone in the project team anticipated at the start. However, the outcome is all the more rewarding as a result.’

Architects CDA have made a virtue of the vast size and limited natural daylight of this building. Daylight is admitted through glazed end walls and three rooflights which run the length of the hangar; floor plates were inserted to mirror this configuration. The result is a central ‘street’ which bisects the space, along with perimeter routes which allow natural light to penetrate to ground level. This arrangement also has the effect of creating discrete office areas rather than inserting vast, monolithic floor slabs. Here, the size and rhythm of the hangar is preserved, while the palette of materials (painted steel, timber, glass and stainless steel) has a contemporary yet

Three Internal Levels Have Been Added To The Building, Accommodating 1,450 Employees. The Palette Of Materials Is Deliberately Restricted To Painted Steel, Plasterboard, Glass And Stainless Steel. The Use Of Conventional Suspended Ceilings Is Kept To A Minimum.

© Martin Sellars Photography

The Original Structure Was Built In The 1940S As A Military Aircraft Hangar. New Office Floors Have Been Inserted, Providing Space At A Density Of 12 m² Per Person. The Existing Ground Floor Has A Depth Of 46 m.

© Martin Sellars Photography

industrial feel that is sympathetic with the original building without imitating it. The main electrical and mechanical services are carried within the new floor plates.

Long And Short Sections Through The Former Aircraft Hangar. New Floors Do Not Run The Full Width Of The Building To Maximise Daylight Penetration.

© CDA Architects

The finished development comprises office space on three levels: ground, first and second floors. The upper floor is smaller than the one below to respond to the curve of the roof. The distance between floors is generous (2.85 m) to maximise daylight penetration, views and airflow, while the upper floor is anywhere from 2.4 m to 7 m beneath the lamella roof structure. In fact, having arrived at an arrangement to make the most of natural light, the architects then had to deal with the issue of glare and heat gain. Extensive research resulted in the use of a Dutch fabric shading system that is more commonly found in horticultural glass houses. This, say the architects, was the only solution which was sufficiently lightweight, effective and capable of installation and maintenance without extensive scaffolding. Artificial lighting is provided through the provision of lighting rafts containing both up- and downlighters.

The heating, ventilation and air-conditioning system supplies free cooling by feeding external air (via the floor plenum) into the building when external conditions allow. A night purge facility can also operate in the summer months to dissipate stored heat. The system also utilises

high-temperature recirculated air to heat incoming fresh air when in heating mode. The building was also upgraded to exceed, where possible, the U-values specified by Part L of the 2000 Building Regulations – a programme which involved lining walls and replacing original glazing with high-efficiency glass. Brise soleil and internal blinds were also added for summer shading.

Skyways House brings a historic building back into use and provides the client with a landmark headquarters which demonstrates that rehabilitation is often just as good as new-build. What is more, the project was completed as part of a wider development within 48 weeks and within a relatively modest budget: £470 per m² for construction, £100 per m² for partial demolition and £780 per m² for fitting out. ‘Cleverness abounds,’ said the BCO judges in 2006. ‘The result is a remarkable, distinctive building that is also highly efficient’.

Wellcome Trust Gibbs Building
London

Building Team

• CLIENT: THE WELLCOME TRUST
• ARCHITECT: HOPKINS ARCHITECTS
• STRUCTURAL ENGINEER: WSP
• INVESTMENT/PROPERTY COMPANY: THE WELLCOME TRUST
• SERVICES ENGINEER: CUNDALL JOHNSTON & PARTNERS
• QUANTITY SURVEYOR: TURNER & TOWNSEND
• PROJECT MANAGER: MACE
• CONTRACTOR: MACE

Building Data

• COMPLETED: 2004
• GROSS: 29,263 m²
• COST: £91,226,798

The building is designed to bring the Trust’s whole administrative team together from disparate workplaces into a single, inspiring, comfortable, ergonomic and socially dynamic space. The building comprises two parallel blocks of open-plan, flexible office space: a ten-storey high, 18 m-deep block faces the Euston Road, while a 9 m-wide atrium links this main building to a lower, slimmer block (five storeys, 9 m deep) facing Gower Street.

Almost entirely clad in glass, the building incorporates a series of triple-glazed, prefabricated facade cassettes which help to reduce solar gain and heat build-up during the summer, while providing a preheated buffer to insulate the building during winter months. This multilayered facade comprises a single-glazed outer skin and a sealed, double-glazed inner unit; the ventilated cavity contains a motorised venetian blind linked to a central control system.

Located On A Busy Central London Road, This Building Manages To Deal With Its Noisy And Polluted Environment While Employing A Range Of Sustainable Measures For Heating And Cooling. The Building Comprises Two Parallel Blocks Of Open-Plan, Flexible Office Space, Separated By An Atrium.

© Nicholas Gutteridge / VIEW

Typical Floor To Ceiling Heights Are 2.8 M; Ground Floor Areas Are Provided With A More Generous 4.7 M Height. The Planning Grid Has Been Set At 1.5 M.

© Nick Kane / ARCAID

This Section Shows The Building’S Principal Components – Office Structures Of Different Heights, Linked By A Central Atrium.

© Hopkins Architects

High-performance glass with ceramic fritting also serves to reduce solar gain.

The atrium is the central feature of the building, but Hopkins was determined that this large volume should not become an excessive energy burden. The atrium space is therefore ‘tempered’ but not air-conditioned, which means that a variety of temperatures will be experienced in this space depending on the time of year. ‘Conditions are maintained to reflect the external season; consequently the occupants should be comfortable lightly dressed in peak summer, and more heavily dressed in winter,’ say the architects. A lower temperature limit is fixed, however, to provide condensation control and maintain conditions for planting. Much of the air exchange within the atrium is free, in the sense that this is where exhaust air from the offices ends up; the atrium provides a natural return air path from the offices to the roof-level plant, allowing excess heat to be reclaimed or rejected. Cooling can also be provided by night purging using the smoke ventilation system. Comfort heating and cooling units are strategically located to ensure that air temperatures do not become extreme.

The offices, however, benefit from radiant chilled ceilings and displacement ventilation. The provision of these features provides good comfort conditions and consumes less energy than a traditional fan coil or variable air volume air-conditioning solution. The system is largely passive, with few moving parts, and will therefore require less maintenance and component replacement than for the more typical alternatives. The displacement system provides 100% fresh air at low velocities through 300 mm raised floor voids; the chilled ceilings are used in conjunction with the displacement ventilation strategy, and both systems are more energy-efficient than more traditional mechanical solutions. The result, apart from offering energy savings, is a more comfortable, draught-free working environment with fresher, cleaner internal air. A slight pressure differential between offices and atrium means that air will naturally flow away from the offices into that large central void. The control of both the chilled ceiling and the floor heating systems is zoned every 6 m along the length of the facade, and pipework is designed to allow tighter control on a 3 m basis with only minor modifications; the partitioning of offices is therefore possible on a 1.5 m grid.

The Atrium Is The Central Internal Feature Of The Building. The Air In This Space Is Tempered, But Not Conditioned, Therefore Temperatures Will Fluctuate Throughout The Year. The Minimum Temperature Is Set To Prevent The Build-Up Of Condensation.

© Nicholas Gutteridge / VIEW

A further sustainable feature of this development is the generous amount of daylight that can flood through the building, reducing the need for artificial lighting.

In 2006, this building was a BCO regional winner, and judges rightly praised its execution: ‘This cathedral-like building boasts the precision and grace of medieval craftsmen, but uses an abundance of glass rather than stone.’