thermal implications of radiant roof barriers: a field...
TRANSCRIPT
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Thermal implications of radiant roof barriers:
A field study in a hot and humid climate
V. Müller, U. Pont, P.H. Tan & A. Mahdavi
Department of Building Physics & Building Ecology
Vienna University of Technology
Title - 1/15
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Content:
• Introduction
• Overview || Climate || Research Questions || Literature
• Approach
• Test Cells||Radiant Roof Barriers ||Ventilation || Rounds ||Monitoring ||
• Results & Discussion• Results & Discussion
• Temperatures
• Data distribution || PMV & PPD
• Conclusion
ToC - 2/15
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Introduction:
• radiant roof barriers impact on thermal performance of test buildings
Climate:
• Malaysia: hot-humid tropical climate
Introduction - 3/15
• Malaysia: hot-humid tropical climate
Buildings:
• Traditional: light weight wooden
structures (low thermal mass)
• Modern: more and more brick
buildings
• Natural ventilation during night
• Massive use of A/C s…
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Literature:
Research Questions:
• Do minor changes in the roof design of test-buildings (roof tiles, layer construction
influence the heat flow to the room(s) below)
• Does the application of radiant roof barriers and counter batten air spaces change the
thermal behavior of the indoor climate?
• Miller et al. (2010): Solar Reflectance Index for different materials and combinations
• Suehrcke et al. (2008): Clay vs cement tiles (in Australia) – no significant differences
concerning heat gains.
• Michels et al. (2008): Radiant barriers as reduction method against solar heat up
• Vandewater (2007): CFD study of the effect of counter-batten systems
Literature /Research Questions- 4/15
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Test-Cells:
• Three per-se identical, free-standing test cells („A“, „B“
& „C“)
• 3x3 m floor area, 3.6 m room height
• 110 mm brick/mortar, ceiling insulated with 50 mm EPS
Approach – Test-Cells - 5/15
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Test-Cells:
Approach – Test-Cells - 6/15
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Test-Cells („A“ and „B“):
Approach – Test-Cells - 7/15
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Test-Cells set up:
• 4 rounds (7 days monitoring
each)
• Increasing ventilation (in roof
space)
• Constant ventilation regime in • Constant ventilation regime in
room below.
Approach – Test-Cells - 8/15
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Test-Cells set up:
Approach – Test-Cells - 9/15
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Results (exemplaric for Round 1 – no ventilation in the roof):
Results- 10/15
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Results (exemplaric for Round 4 – max. ventilation in the roof):
Results- 11/15
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Results PMV/PPD / Data - Distribution
Results- 12/15
Day Night
„Comfort Zone“ 22-27 °C
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Results PMV/PPD / Data - Distribution
Results- 13/15
Percentage of time with a PMV
between +1 and -1
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Conclusion:
• Attic spaces with very low ventilation: Radiant roof barriers
showed a slight positive effect
• With increased ventilation, this effect disappears (test cells
without radiant roof barriers performed better)
• Clay vs cement: Clay test cell performed slighly better• Clay vs cement: Clay test cell performed slighly better
• Application of radiant roof barrier systems should be evaluated
case by case.
• Radiant Roof barriers in very good ventilated roofs might be
counterproductive, as night-time radian cooling is diminished.
Conclusion- 14/15
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Thank you for your attention!