The Great West Quarter, Brentford, West London

Great West Quarter (GWQ) is regeneration on a grand scale. A dilapidated five hectare site located on the Great West Road, it was an agglomeration of disused industrial and office buildings, including the iconic Grade II listed Wallis House that had become run down and neglected since being vacated in 1995.

The site, developed by Barratt West London working with Assael Architecture and NHBC, is being transformed into a striking, vibrant new living quarter within an island site, and comprises a mix of two converted and 17 new buildings, including a new 25 storey landmark tower.

The involvement of NHBC in the design team has allowed issues of Building Regulations compliance to be resolved prior to detailed design work being undertaken, making the process easier for the whole team.

Breathing new life
A key concern for the planning authorities was the site’s status as a designated strategic employment area, albeit one in dire need of redevelopment. Negotiations to find a compromise between declared policy and the move towards mixed use developments led to agreement that a greater diversity of use would be necessary to ensure the long term success of the regeneration effort.

Understanding the complexities of the site, NHBC was approached at a very early design stage to offer guidance on how various elements of the project would work, and importantly meet the requirements of the Building Regulations as well as NHBC Standards.

The vision was to create a balance of commercial and residential uses, with appropriate amenity space to create a vibrant and sustainable community, but also be deliverable and provide long-term stability for the site and its surrounds. The proximity of the Great West Road, M4, railway and Heathrow airport and associated environmental constraints presented many design challenges to ensure the vision became reality.

There are three prominent elements to the development, each with a distinctive character:

*Wallis House, the listed Art Deco building with its ten storey tower at the eastern side.

*Moderna, 17 new builds forming the centre and rear of the site.

*Skylon, a 25-storey counter-balancing structure on the western edge.

Wallis House – delicate refurbishment
Wallis House was built in the 1930s to the design of Wallis Gilbert & Partners. One of the last landmark art deco factories remaining along this gateway to London, it was known as ‘The Golden Mile’ in its heyday, denoting the social and economic progress in this part of London.

Its successful conversion from its industrial past to a desirable residential address is the result of a journey that has negotiated a multitude of planning and technical complexities.

The building’s proximity to the M4 means that a significant amount of the envelope is exposed to a harsh acoustic environment, a factor that might normally have led to a refusal of planning consent for residential use. However, Assael and the design team worked closely with the London Borough of Hounslow, English Heritage, Twentieth Century Society and NHBC to arrive at a solution that has secured the building’s long-term future.

One solution has been to orientate the residential areas away from the noise. Offices and a gym face the road, together with a first floor residential corridor that serves as an acoustic buffer to the apartments at this level. An efficient whole-house ventilation system has been employed to ensure that all occupiers of the building enjoy a safe, clean and quiet environment.

The building’s brick and stone clad steel structure imposed huge challenges from the outset. For Barratt and Assael Architecture, one of the greatest challenges has been the refurbishment of the building’s envelope. A balance had to be struck between preserving the important features of the listed building and upgrading its thermal and acoustic performance, whilst meeting the requirements of Building Regulations.

Exhaustive studies were conducted to ascertain the viability of refurbishing the Crittall-type steel windows. While these were in a very poor condition, they could have been successfully refurbished. However, single glazed thermally unbroken steel windows usually perform poorly in acoustic and thermal terms. To counter this, various secondary glazing options were considered but eventually deemed inappropriate for reasons of operability, obtrusive sightlines and the inherent risk of condensation. A high performance glazing system by the Danish firm MAG Hansen was eventually chosen to replace the original windows.

NHBC was involved from a very early stage to ensure that the considerable amount of bespoke detailing solutions across the project would meet key performance criteria.

Skylon – a 21st Century icon
By contrast, the architectural design of Skylon will establish a 21st Century icon; utilising modern materials and techniques to create a new architectural statement worthy of ‘The Golden Mile’. The 25 storey, mixed-use tower will use an innovative twin-skin façade which is both visually striking and technically sophisticated.

The buildings external envelope has been developed through consultation with specialist façade engineer, Buro Happold. The early involvement of NHBC and cladding subcontractors has assisted in creating a bespoke solution, designed to site-specific parameters.

The twin-skin façade creates a high performance envelope that provides significant environmental benefits whilst maintaining optimum internal conditions, see Figure 1. The glazed outer skin forms the water-tight barrier, protecting the building from the elements and the noise of the nearby M4/A4, whilst the inner skin provides the thermal barrier. The ‘interstitial space’ between the skins varies in depth to provide balcony space at certain locations. A detailed study of the façade shows a pattern of ‘fritting’ on the outer skin, which is designed to provide varying levels of shading in areas that would otherwise experience high solar gains.

To avoid the interstitial space becoming too hot in summer, an attenuated airflow path is provided by acoustic baffles at party wall locations. This air path also allows rapid ventilation of the rooms within each dwelling. In addition, the inner skin profile is eco-centric to the outer skin - providing significant shading to the south (2 metres deep), and minimal shading to the north (0.5 metres deep).

The salient points of the double-skin façade design include the ability to:

*attenuate the noise from the outside air when the external facade is sealed.
*mitigate the pollution of the incoming air through filtration if necessary.
*control the wind pressure inside the living space.

Plus,

*an allowance to control the air into the interstitial space if required.
*have an intra-cavity device to mitigate glare and solar gains.
*use a higher proportion of glazing and still meet the new building regulations. 
*allows the balcony amenity to be used for a larger portion of the year.
*creates a high quality living environment in a residential tower application.  

The twin skin also provides a depth to the building that would appear as an attractive play of light and shadow. In addition, the interstitial space would be treated differently by each resident, providing an active and dynamic façade.

The orientation and form of the tower has been subject to wind tunnel testing and detailed discussion with the wind consultant to balance the urban design aspirations and the optimum wind environment. This has resulted in a unique ‘yacht mast’ plan shape that will create minimal disturbance to the local wind environment. The floor plan is also designed to ensure all accommodation receives sunlight at some point during the day and provides exceptional long distance views in every direction.

The top two floors of the building are set back in plan to provide a double height termination to the tower. The outer glazed skin extends higher than the top floor to provide lightness to the top and a stunning view ‘through’ the top of the building. At night, the building would constantly change character, reflecting occupancy and internal lighting levels.

Constraints become opportunities
Great West Quarter has won numerous awards, and Wallis House and Skylon are examples where a design team has overcome numerous challenges through tenacious design and collaborative thinking to develop unique opportunities.

The project is due for final completion of the last phases in 2011, and there are currently 250 of the 790 apartments occupied on the site.

NHBC’s successful collaborative approach
NHBC Building Control, Assael Architecture and Barratt West London have worked together on this project from the pre-planning and initial concept design stages in 2003.

NHBC has considerable experience dealing with all types of projects in all market sectors. Bringing those skills together for projects such as this shows how versatile our services are, and the importance of early engagement with a proven and experienced building control provider such as NHBC.

For more information, visit www.nhbc.co.uk/bc or contact Colin Blatchford- Brown – Building Control
Manager on 0844 633 1000. For Assael Architecture, visit www.assael.co.uk