Cold bridging

Some designers may be concerned that steel penetrations through the building envelope may form a 'cold bridge' which can lead to condensation, or in extreme cases, to a risk of corrosion. There is no answer that is appropriate for all applications and the designer must assess the risks and consequences of the cold bridging. If the internal

Steel Construction Architecture

Inside

10.2 Steel column extends outside the perimeter wall, with the interior weather protected by rubber gaskets — Renault building, Swindon (architect: Foster and Partners)

Inside

10.2 Steel column extends outside the perimeter wall, with the interior weather protected by rubber gaskets — Renault building, Swindon (architect: Foster and Partners)

atmosphere is not very humid, and the exposed steel member is not adjacent to materials likely to be damaged by moisture, then experience has shown that steel members passing through the envelope should not lead to problems of cold bridging.

If there is a major concern, an element of trace heating can be introduced along the steel member just inside of the external skin, although this is rarely used in practice. Alternatively, the steel member can be joined at the point of the cladding to another section with an insulating component placed between the two pieces. However, this can be very difficult to resolve elegantly if both inside and outside components are exposed to full view. The following examples illustrate details that have been employed successfully.

Figure 10.2 shows a section through an external wall of the Renault Parts Distribution Centre, which is illustrated in larger scale in Figure 1.2. The perforated vertical members support both the cladding and glazing. At the ends of the glass panels, rubber gaskets abut the steel section and act as a weatherseal.

At the David Mellor Cutlery Factory, a steel bracket was inserted in the plane of the glass. The bracket connects the internal roof structure with a solid steel perimeter ring bar, as shown in Figure 10.3.

Studio Downie's Visitor's Centre in Sussex uses the interplay of planes created by solid and transparent walls to heighten awareness of what is outside. The modest sized steel-frame penetrates the glass skin, which softens the edges between inside and out, as shown in Figure 10.4.

10.3 Detail of steel bracket connecting internal steel structure with perimeter wall — David Mellor Cutlery Factory, Hathersage (architect: Michael Hopkins and Partners; courtesy of Alan Brookes and Chris Grech)

Connecting Steel BeamsConnecting Steel Beams

10.4 Tapered beams (T-sections) penetrating glazed envelope — Hat Hill visitor's centre, Goodwood, Sussex (architect: Studio Downie)

The steel tusks of the Western Morning News building are supported by steel beams which penetrate the sloping glazed façade. A steel plate surrounds the penetration through the glazing, as illustrated in Figure 10.5. The penetration is sealed by a rubber gasket glued to the steel member.

10.4 Tapered beams (T-sections) penetrating glazed envelope — Hat Hill visitor's centre, Goodwood, Sussex (architect: Studio Downie)

10.9 Penetration through glazing at Cologne Airport (architect: Murphy Jahn Architects)

Not all penetrations are visible. Figure 10.6 illustrates the use of a bracket detail which penetrates the roof of the Sainsbury's supermarket to receive the tie-rod ends.

The Enterprise Centre at the Liverpool John Moores University is another example of where tubular members are exposed on both the inside and the outside. Arranged on a diagonal grid, with inverted tripod supports, they give the roof lateral stability without the need for heavy bracing. The tubular beams pass through the perimeter cladding and extend to support the wide overhanging eaves. The ends of the beams are propped by inclined struts as an integral part of the delicate and elegant roof assembly (see Figure 10.7).

The designer should also consider the affect of movement of the structure as it passes through the fabric. Sufficient flexibility should be included in the detail to accommodate movement of the structure and/or cladding. Figure 10.8 shows the detailing of the steelwork which penetrates the cladding and how structural movement is accommodated. Figure 10.9 illustrates this principle for a glazed façade at Cologne Airport.

Greener Homes for You

Greener Homes for You

Get All The Support And Guidance You Need To Be A Success At Living Green. This Book Is One Of The Most Valuable Resources In The World When It Comes To Great Tips on Buying, Designing and Building an Eco-friendly Home.

Get My Free Ebook


Post a comment