AHRC Project 58 (also
referred to as the "Coldicutt Report")
AFIA OVERVIEW
by Tim Renouf, Secretary AFIA - Aluminium Foil Insulation
Association Inc. (Vic 1998)
and quotations by Prof. Richard Aynsley
March, 2003
Publication examined:
Thermal Performance
of Housing Units in Queensland - Phase 1: a study by the Department of
Architecture and Building, University of Melbourne. AHRC Report 58, 1981.
Research was funded by The Australian Housing Research
Council (AHRC).
Research Team: A. Coldicutt (Team Leader), T. Isaacs, T.
Williamson, S. Coldicutt, E. Coldicutt,
F. Moschini. The Project Committee included a member of
CSIRO Division of Building Research.
The 1981 Australian Housing Research Council federally
funded research report examined the thermal performance of ceiling insulation
in housing units across Queensland. Four locations were selected: Brisbane,
Rockhampton, Townsville, Longreach. Two types of ceiling insulation were
compared:
(i) 75mm fibreglass directly on the ceiling, and
(ii) a single layer of reflective foil insulation across
the top of ceiling joists with an airspace beneath.
The 275 page Report explicitly concluded that only foil
insulation should be used. The central reason was that fibrous insulations had
a greater resistance to heat flow up than foils, causing houses to stay hotter
longer by trapping heat in the often difficult to ventilate ‘stagnant heat
zone’ between the top of door heads and ceilings. Foil, on the other hand,
stopped heat penetration successfully during the day and released accumulated
heat beneath the ceiling during night time because of the foil’s inherently
lower resistance to heat flow up compared to bulk insulation.
In warm to hot climates where winter heating is very low or
non-existent, quoting Prof. Aynsley: “Horizontal
reflective foil airspaces in roofs have
the unique characteristic of having
a greater resistance to heat flow down
than up. They act as one-way values for summer heat flow, restricting
daytime heat gain while facilitating night time heat loss. This is important
because indoor discomfort in the evening which inhibits sleep can be very
debilitating". Houses using foil
insulations combined with natural ventilation can readily avoid
airconditioning.
Quoting Prof Aynsley again: "If energy efficiency
regulations, as a matter of convenience, ignore the beneficial effects of
horizontal reflective airspaces in roofs of houses in warm climates, then the
situation could be actionable under
trade practices legislation. Ignoring these effects would be detrimental to
a wide range of aluminium foil insulation products and favour bulk insulation
products in spite of the demonstrable consumer benefits of reflective
insulation in Australia’s warm climates."
*****************
Quotations from:
Richard Aynsley, B.Arch (Hons I), MS (Arch Eng), PhD.
Member : ASHRAE
Former UNESCO Professor of Tropical Architecture, James
Cook University, QLD
Dean, College of Technology, Southern Polytechnic State
University, Marietta GA, USA
*August 2000