No. 4 St Paul's Square

Regarded as one of the most significant commercial developments in Liverpool city centre, the building provides a total of 10,000 m² of high quality Grade A office space over eight floors and is the focal point for Liverpool’s Central Business District.

No. 4 St Paul's Square is rated BREEAM 'Excellent' and won an RICS award for best commercial development in the North West and includes sustainable features, such as a sedum roof, water-efficient taps, cycle racks and a lighting system designed to minimise light pollution and to reduce carbon emissions by more than 22 %.

Unitised curtain wall facade

The main envelope installation was achieved using a pre-fabricated and pre-glazed unitised form of construction and without the need for costly scaffolding. Elements were installed using our own floor cranes and the "Table Method" as shown below. This method allows facade elements to be passed over the top of the handrails and installed with the slab edge protection remaining in place providing a safety barrier for our operatives and others on site. The bespoke curtain wall elements, typically 1.5 m wide by 3.905 m high, were manufactured off-site at our Head Quarters in Arnstorf, Germany and delivered to site by road. The vertical feature fins, where required, were fitted to the elements before installation.

Unitised Facade to Office Areas

The main envelope is comprised of pre-fabricated and pre-glazed curtain wall elements with a natural anodised finish. The system is a structural silicone glazed (SSG) design which incorporates a small sub-frame to aid re-glazing. Vertical feature fins have an aluminium perimeter frame that has a double glazing unit with Kapilux capillary tube type insulation inside. This material is also used in parts of the vision glazing to add visual interest.

Technical details

- Watertightness static and dynamic: 600 Pa

- Air permeability: 600 Pa

- Thermal insulation curtain wall (typical): Ucw 1.4 to 1.6 W/m² K

- Thermal insulation glazing: Ug 1.1 W/m² K

- Solar shading / glazing g value: 0.33

- Light transmission: 60 %

The facade was tested to CWCT sequence B to 600 Pa, including dynamic aero engine test. Double glazed units to the vision areas had a combined high performance solar control and low-e coating to give high thermal insulation and high solar shading yet allow high light transmission through the glazing.


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