Integrated Design – Biome Structure, Envelope & Building Services.
pg 46 – The competition winning scheme had worked on the assumption that some combination of optimised glazing transparency with the primary steel structural beams acting as fixed shading elements would be sufficient to provide daylight control and limit excess solar gains. The structure was originally conceived as solid fins with the glazing suspended beneath in a simple mullion system. As the analysis work progressed this proved to be too simplistic an assumption. the deep structure obscured too much of the sky vault in cloudy and low-light situation but was also not effective in dealing with high level of solar heat gain at times when the sunlight is normal to the glazed surface. This would have led to comfort issues for occupancy.The main structural member were deliberately placed outside the glazing to help with shading, they have a clear span of up to 12-m in places and so were of considerable depth.
pg 49 – There were a number of different structural solutions including;
- An optimised solid fin design with non-structural secondary glazing elements (competition scheme)
- an external truss system also with non-structural secondary glazing elements
- a grid shell to hold the glazing tied to more slender primary arches.
We evaluated the output data from the models and compared it with the Eden Project Data.
[the third solution] offered the best balance of daylight and solar control. It also turned out to be the most cost and material effective solution to deliver the enclosure.
With the need for high daylight transmission, the use of body tinting of the glass was not an option and so selective coatings were investigated as the preferred option…. [pg 51] the selective double glazed unit which allows approx 65% of the incident daylight frequencies to pass through with only 35% of the solar heat transferred, primarily by filtering the infra-red frequencies from passing into the space.
pg 51 – ETFE which was used at the Eden Project, was also considered as it offered significant weight benefits [however] the coatings were not sufficiently developed to reliably achieve level of selective solar energy reflection that high-performance glass could achieve.
pg53 – By keeping radiant energy outside the building envelope Internal shading behind the high-performance glazing units would have trapped heat at height level .
pg 56 – The shade are triangular in for, like sails, and are cable tensioned. They are completely concealed within the lower section of the ribs when not in use and are actively controlled to deploy when required to modulate internal daylight levels to the desired level
pg 56- The biomes forms were optimised to allow maximum daylight penetration. The form of the Flower Dome was modified to create an overhand to the north facade, which slopes backwards from a peak. This creates a glass face that is inclined outwards at near the same angle as the peak annual radiation for that orientation at the extreme sun angle and hence is a completely self-shading facade, requiring no external shades.