Façade engineering Cooling
is the reduction in solar transmission of the glazing for extended periods of time due to the resulting increase in solar angle of incidence. The bay window design inevitably leads to an
increase in thermal transmittance due to the greater developed transmission area and, more importantly, the bay window (‘collar’) framing leading to some degree of linear and point thermal losses. Previous research has shown that relatively minor changes to the thermal transmission of the building envelope may not be critical for a commercial building with relatively high internal gains. The design team carried out a series of studies to
assess the overall energy performance, taking into account the expected increase in thermal transmittance and gauging the combined effect in heating and cooling mode.
Early-stage FE The façade engineering input during the concept stages for both projects was crucial in terms of testing the feasibility of the proposed design, and exploring ideas in informed dialogue with selected specialist cladding contractors. The initial idea, which was based on considerations of solar shading and reduction of solar gains, was quickly interpreted and presented as a series of conceptual hand sketches in an effort to gauge the complexity and the viability of the concept (see Figures 3 and 4). The conceptual studies were linked with building
physics input – initially as general considerations and gradually as more specific estimates of required and achievable thermal and solar performance. Clearly the single biggest impact on solar gains is given by factors >
Figure 3: Ropemaker Place, east/west façade concept
Figure 4: Ropemaker Place, south façade concept
While the lower levels on the windows of Plantation Place are sealed (left), Ropemaker has a tilting design for its façade, which reduces the energy used for cooling
www.cibsejournal.com August 2010 CIBSE Journal 27
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