ETFE-foils that are typically used in the construction of single, two- and, three-layer ETFE-foil cushions, were selected. In two-layer and three-layer foil panel construction, the top and bottom layer were 200 μm thick foils, while the middle layer was 100 μm thick. This was because, in an ETFE-foil cushion construction, top and bottom layers are usually composed of thick layers, to carry wind load and the pre-stress developed in the top and bottom layer in an inflated cushion. Alternatively, top layers usually consist of fritted foils with different percentage of fritting, such as foil with 75% fritting comprised of 75% fritted area and, 25% transparent area.
Foil samples were provided by Architen Landrell Associates Ltd. Selected ETFE-foil foil samples for test-rig experiment were:
• 100 µm transparent
• 200 µm transparent
• 200 µm transparent with 75% fritting (75% fritted and 25% transparent foil)
• 200 µm transparent with 25% fritting (25% fritted and 75% transparent foil)
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(a) (b)
Figure 5-8: (a) 200 µm transparent with 75% fritting, (b) 200 µm transparent with 25% fritting
Figure 5-8 presents 200 µm transparent foil with 75% fritting and 200 µm transparent foil with 25% fritting. Among the selected types, foils similar to the 200 µm transparent with 75% fritting [see Figure 5-8 (a)] and, 200 µm transparent foils were used to construct the cushion roof of one of the case study buildings (Nottingham High School), presented in Chapter 6.
5.3.3 Weather data
Weather data e.g. outdoor air temperature and humidity was monitored by a Tiny tag Plus 2 - TGP-4017 data logger. This data logger was attached to the exterior of Test-rig 1. Although this sensor was water proof, extra care was taken to avoid contact with rain water and direct solar radiation by placing a steel frame around the datalogger. A sampling period of one minute was applied. External incident solar radiation was measured by a Kipp & Zonen CMP 3 pyranometer, located adjacent to the test-rigs which was already mentioned in section 5.3.1.1. Figure 5-9 presents sensors used to measure environmental parameters and Table 5-4 presents sensor types used to measure environmental parameters. Table 5-5 presents identifications of environmental data used in the analysis.
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(a) (b)
(c)
Figure 5-9: (a) Temperature sensor measuring external ambient temperature and humidity, (b) steel frame around the sensor, (c) pyranometer measuring total horizontal solar radiation
Table 5-4: Description of measurement sensors
Measurement type Sensor type
Data logger DataTaker DT 85
External total horizontal solar radiation (external)
Kipp & Zonen CMP3 Pyranometer (spectral range: 0.3-2.8µm) Outdoor air temperature Tinytag Plus 2 (-40°C to 0+85°C)
Table 5-5: Measured environmental parameters and identifications
Environmental data Identification
Outdoor ambient temperature OAT
Relative humidity RH
External total horizontal solar radiation ExIR
5-114 5.3.4 Timescale of the monitoring
Continuous monitoring commenced on 15 April 2014. A number of observations were made and the test-rig position was changed depending on the sun’s position so that the ETFE-foil panels had the largest view of the sky dome. The position of the pyranometer measuring incident solar radiation was changed so that the view factor of the pyranometer would not be obstructed by adjacent structures. After completion of all necessary steps, it was possible to start the experiment from 1st July 2014. The priority of this study is to observe and analyse the optical and thermal performance of single and multi-layer ETFE-foil under different weather conditions. The orientation of both test-rigs was the same throughout the monitoring period to obtain sufficient data to represent the thermal performance of ETFE-foil panels.
This test-rig experiment was conducted in two different phases. The first phase was conducted between July 2014 and October 2014. In this phase solar transmittance of different types of single, two- and three-layer flat ETFE-foil panels was measured.
During this experiment Test-rig 1 was capped with ETFE-foil panels of different single and multiple layer configuration while Test-rig 2 was kept open. Each box contained one Kipp & Zonen CMP3 pyranometer which was placed internally and at the same height. So pyranometer in one of the test-rig with ETFE-foil panel measured transmitted radiation while another pyranometer in another test-rig without any cap measured incident solar radiation. The results were obtained from the ratio of transmitted and incident solar radiation. Using this procedure the solar transmittance of single, two- and three-layer ETFE-foil panels were determined. Table 5-6 presents the schedule of monitoring for the first phase experiment.
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Table 5-6: Different combinations of ETFE-foil in Test-rig 1 (First phase)
Test rig 1 Test rig 2
ETFE-foil layer number in panels
Combination Foil type Thickness ETFE-foil layer
Single-layer Layer 1 Fritted (25%
fritted and
The second phase test-rig experiment was conducted between May 2015 and October 2015 to examine the thermal performance of a variety of single, two-layer and
three-5-116 layer flat ethylene-tetra-fluoro-ethylene (ETFE) foil panels under different weather conditions. A number of multi-layer combinations incorporating different thicknesses of transparent and/or fritted ETFE-foils were examined. A part of this test-rig experiment also included rain suppression mesh which was placed on top of the ETFE-foil panel of one of the test-rigs while the adjacent test-rig was capped with an ETFE-foil panel without mesh. The purpose was to determine the effect of rain noise suppression mesh on the thermal performance of ETFE-foil panels. Table 5-7 presents the schedule of monitoring of second phase experiment.
Table 5-7: Different combination of ETFE-foil in Test-rig 1 and Test-rig 2 (Phase 2)
Test-rig 1 Test-rig 2
Transparent 200μm Layer 2 (Middle