Heat and moisture response of vented and compact cathedral ceilings: a test house evaluation
Hens, H. and Janssens, A.
1999
ASHRAE Trans
Hens, H. and Janssens, A., (1999), Heat and moisture response of vented and compact cathedral ceilings: a test house evaluation, ASHRAE Trans.
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In the last decade, public awareness of the greenhouse effect has pushed the building sector toward higher energy efficiencies. This move has had consequences for roofs with a cathedral ceiling. A U-factor in the vicinity of 0.2 W/(m2¡¤K) instead of 0.6 W/(m2¡¤K) became the new target value. The move toward such a low U-factor for cathedral ceilings was evaluated in an extended test house program. The major objective of the research was to find answers to the following three questions: (1) What is the impact of air ingress and wind washing on the hygrothermal performance and durability of such well-insulated roofs? (2) Is a vented air space above the thermal insulation needed to prevent concealed condensation? (3) Is a vapor retarder underneath the insulation equally efficient? The traditional answer to questions (2) and (3) is built on five assumptions: (1) heat is transported through all materials by conduction only, (2) moisture moves through the materials by diffusion only, (3) air ingress is restricted to the air space, (4) outside air ventilation functions under all circumstances, and (5) it always means additional drying capacity. The test house measurements confirmed that in the cool, maritime climate of Western Europe, air ingress and wind washing overthrow assumptions (1), (2), and (3). Also, assumptions (4) and (5) are not true under all circumstances. The research resulted in the redrafting of the performance requirements for highly insulated roofs with a cathedral ceiling. |
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Related Resources:
 ASHRAE-American Society of Heating, Refrigerating and Air-Conditioning Engineers
"the sole purpose of advancing the arts and sciences of heating, ventilation, air conditioning and refrigeration for the public's benefit through research, standards writing, continuing education and publications."
- IRC: Institute for Research in Construction
"Canada's research, building code development, and materials evaluation services, .. issues that have a large economic impact, assisting industry to innovate and develop technologies that are safe, durable and cost-effective. "
- Laboratory of Building Physics, Leuven, Belgium
"...research and educational activities in the field of heat and mass transfer in building materials, building parts and buildings, the energy use in buildings, building installations and building acoustics. Also research in urban physics is part of our activities.
- Journal: ASHRAE Transactions
- Laboratory of Building Physics- Leuven, Belgium
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