Anglesey Abbey Visitor Centre, Lode, Cambridgeshire

Background

Anglesey Abbey is well known for its gardens, which offer superb vistas and an impressive collection of plants within a formal arrangement. Visitor numbers to this National Trust property have risen to over 180,000 per year and in recent years this has placed a strain on the visitor facilities.

Prior to the opening of the new buildings in July 2007, the facilities comprised a teahouse constructed in 1975, which had undergone 11 extensions. Very few buildings look or work well after this many alterations!

The new facilities deliberately straddle the car parking on the east side and the formal gardens on the west. Helping visitors to undertake the transition from arrivals and parking to the much calmer environment of the gardens is a very important goal of the new facilities. Part of the National Trust’s brief to architects Cowper Griffith was to ensure that the gardens definitely remained the main attraction – the centre, whilst being attractive, was to be ‘recessive’, rather than becoming a competing feature to the gardens.

An important factor in achieving this goal was the design of the glazing and associated shading. The client wanted visitors to enjoy seeing the garden from the centre but did not want those in the garden to be too distracted by the building especially reflections on large expanses of glass.

Louvred screens providing ‘filtering layers’ were used in various locations – two particular elements of which are the subject of this Timber Solution. The first is a wooden louvred system constructed in the gable ends of the east and west facing elevations, which was used in combination with other solid and glazed elements in the gable. The second is an external sliding louvred wooden panel arrangement installed in front of three aluminium sliding doorsets on the south elevation.

 

Location of the louvred elements

The main east and west gable walls ‘pick from a palette’ of shaded and non-shaded glass and timber clad wall details, to provide the optimum design, in terms of meeting both the requirements of the building and controlling cost. The site plan provides a general arrangement of the ground floor and identifies the location of the five elevation arrangements, which are described below. The three external sliding louvred frame arrangements, D1, D2 and D3 are shown on the site plan on the south-facing wall. Each of these gives access to the external seating areas and decking in an enclosed garden area, which visitors are encouraged to use on sunny days to increase the capacity of the restaurant. The purpose of these sliding louvred frames is to provide attractive filtered light as well as control unwanted solar heat gain.

 

Design challenge

There were many issues to consider simultaneously in terms of the glazing / wall details – those relevant to this study are listed below.

A. General architectural appearance.

  • Create an external appearance, particularlyfrom the west side, which does not draw too much attention to the building.
  • Provide a consistency of architectural appearance to all elevations, whilst actuallydelivering very different functionalperformance for each.
  • Complement the timber cladding by working to a modular size based on the gauge of the cladding board joint.

B. Light and energy performance.

  • Remove unwanted intense high-level light and convert it into filtered light.
  • Provide good quality views from the restaurant to the gardens.
  • Satisfy Part L2A in terms of heat gain and heat loss.

C. Long term appearance and durability

  • Provide durable, maintenance-free louvres.
  • Ensure long-term durability of the timber.
  • Minimise staining of timber from metal fixings and any other components.
  • Ensure that louvres are of sufficient stiffness to prevent any sagging.
  • Plan for fairly consistent weathering and greying of the timber and minimise raindrop staining from rain.

D. Manufacture and installation.

  • Ensure that it is reasonably easy to erect the structures on site, probably by maximising the amount that could be prefabricated off site.

E. Maintenance and cleaning.

  • Allow for easy periodic cleaning of glass.

 

Elev. ref 'Lower' const'n  'Apex' const'n Comments 
 A Timber cladding.

Timber louvred rain screen. No glass.

Service rooms with low occupancy are located behind this wall, hence no glass is used. However, louvred rainscreens are provided in the gables to match those used elsewhere.

 B Timber cladding. Glass with timber louvres. The retail area benefits from the higher quality filtered natural light provided by the high level glazing. The lower solid walls provide flexible retail display space.
 C Glass without louvres. Timber louvred rainscreen. No glass. The learning / restaurant overspill room benefits from views out to the nearby trees, which provide considerable shade. Room acoustics and flexibility of use of this space dictated a modified ceiling and upper panel finish to this elevation, hence no glazing is required in the gable above this ceiling.
 D Glass without louvres. Timber louvred rainscreen. No glass. The restaurant area has clear views onto the formal gardens. The upper louvres filter the high-level sunlight and control the unwanted solar gains.
 E  Glass.  Glass. This particular glazed wall benefits from a large overhanging roof, providing good shade and is set back from Wall D, making it much less noticeable to those in the gardens than Walls C and D.

 

Options considered

Option Commentary
Using glass with louvred shading for the top gable section of all east and west gables. The Architect was initially keen to use the shaded glazing in the gables to achieve the desired visual effect from inside and outside. However, the cost of this was far greater than a solid wall and further thinking led to the conclusion that not every wall benefited from glass at high level. To maintain architectural consistency it was decided to use the louvres in a different capacity, namely as a rain screen cladding, allowing all elements to perform different functional goals, yet remaining architecturally consistent.
Construct the glazed curtain wall framework system using wood rather than aluminium. The original designs were based on standard aluminium curtain walling details. It was decided that moving over to an entirely timber framed glazing system part way through the design process could not realistically be accommodated.
Use of aluminium louvres. This was an obvious option given that the curtain walling was aluminium. However wood proved a better choice both technically and financially, mainly because creating bespoke solutions is much easier in wood.
Large gap between the curtain walling and fixed louvres to allow easy access for cleaning of the glass externally. Cowper Griffith recognised that excessive slenderness could compromise the durability and stiffness of the louvres and therefore employed TRADA consultants to advise on this and other related matters. The steel framework system discussed above created an arrangement of three units in width, between the four uprights. Two and three panels per unit were considered with three being chosen. This was because:
–With a shorter span it allowed more slender sections of louvre
– The use of an odd number of panels, within an odd number of units (nine in total), created a more aesthetically pleasing symmetry.
Oak was initially considered because it had been used on the previous buildings.  Western red cedar was chosen. At approximately 720kg/m3, oak is considerably denser than western red cedar at 390kg/m3. Whilst the higher density was not a problem for the cladding,it presented much greater challenges for the louvred panels in terms of being structurally supported by the curtain-walling framework.

 

Design detail chosen

Gable – steel framework

The slender and virtually non-visible steel framework, into which the timber louvred panels are seated, allowed the whole system to be supported back to the four aluminium structural upright members using only six fixings.

These were constructed by the curtain-walling sub-contractors and temporarily fixed to check for accuracy before being sent to Coulsons, the joinery sub-contractors. Working to the actual steel framework allowed Coulsons to make the timber panels to a precise fit within their workshop.

The steel framework simply comprised 6mm thick ‘L’ and ‘T’ sections, with a grey powder coat finish matching the aluminium to prevent staining of the timber from contact with the steel. To connect it to the aluminium members, simple cleats with bolt holes were welded to the back with similar partner members, secured via cut-outs in the cover caps, to the vertical aluminium structural supports. The framework can be removed reasonably easily if necessary, for example if replacement glass units are required.

The whole arrangement is set forward from the aluminium curtain walling by approximately 150mm. The aim was to:

  • Provide sufficient space to install the components.
  • Create two visually distinct entities in terms of the curtain walling and louvred panels.

 

Gable – western red cedar panels

The louvres are held within their own timber framework, which incorporates mortice and tenon, glued joints for long term durability and stiffness. The vertical frame members are routed to receive the louvres, which are glued and pinned in place.

Each panel is hung using 100mm high projecting stainless steel hinges (to prevent staining on contact with the timber), to ensure they open clear of the front edge of the louvres which project beyond the outer frame. The hinged panels are opened to allow easy access for cleaning. The hinges themselves are quite discrete, as can be seen by the photo of Elevation B. To latch the panels in position a simple stainless steel budget lock was recessed into the back of the louvre.

Because some of the triangular sections at the top of each panel would hit the underside of the projecting roof, these have been fixed in position and are not part of the hinged arrangement. The gap behind is sufficient to reach the top part of the glazing for cleaning purposes.

The top ‘rail’ of the hinged panels is effectively formed using a ‘modified’ louvre with a deeper blade for increased strength and provides a virtually invisible detail to maintain the consistent vertical spacing of the louvres.

 

Gable – louvres and detailing

 The services consultant advised that a 45° downward angle on the louvres would produce the desired shadowing effect internally based on the architect’s preferred centres for the blades. These centres were based on half the distance of the expressed open joint of 204.5mm on the cladding below. It is also a large enough angle to ensure that rain runs off at the bottom of the louvres, rather than running up the underside of the louvre.

The roof overhangs by a generous 1200mm, which will considerably minimise the wetting due to rain. Using no treatment, stains or coatings, the intention is to allow all the timber to naturally ‘grey’ over time. By avoiding unwanted raindrop and metal-related staining this should occur reasonably evenly.

 

Sliding louvred frames to double doorsets

These are controlled using the simplest of human intervention – they can be shut, open or half open and locked into each position to prevent visitors from interfering with the chosen setting.

The weight of the frames themselves is supported on a roller system and track at the base. The top rail acts as a guide track only.

On this occasion the blades have a much shallower angle to maximise visibility of the picnic area from inside. This does however run a higher risk of staining from rain than the steeper angle used in the gable ends.

The vertical spacing of the louvres matches both the gable detail and the cladding below. It was not possible to use the same thickness of blade across the full width of the ‘doors’ without intermediate support. A discrete mullion detail was used, therefore, set back from the front of the blades to provide additional support at the mid-point. 

Year Published:

June 2008

Client:

National Trust

Completion Date:

January 2008

Architect:

Cowper Griffith Architects

Main Contractor:

Haymills (Contractors) Ltd

Joinery Contractor:

Coulson Building Group

Timber Supplier:

Capricorn Timber

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