Book - School of Science and Technology

78 The building in summerTable 3.3 Relative efficiency of shading devices in reducing solar heat gain (plainsingle glazing (0)Relative exclusion efficiency (%)Type of solar protection Single glazing Double glazingExternal dark green miniature louvred blind 83 87External canvas roller blind 82 85External white louvred sunbreaker, 45 blades 82 85External dark green open weave plastic blind 71 78Heat reflecting glass, gold 66 67Clear glass with solar control film, gold 66 67Densely heat absorbing glass ± 67Mid-pane white venetian blind ± 63Internal cream holland blind 57 61Lightly heat absorbing glass ± 50Densely heat absorbing glass 49 ±Internal white cotton curtain 46 47Internal white venetian blind 39 39Lightly heat absorbing glass 33 ±Internal dark green open weave plastic blind 18 26Clear glass in double window ± 163635Light weightbuildingHeavy weightbuilding34Peak internal temperature (°C)333231ABA3029Peak outside temperatureCDEBCDE282 4 6 8 10Air changes per hour2 4 6 8 10Figure 3.7 Room temperature profiles for a selection of window glass and shading devices