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By logging the test buildings’ responses to
the Newcastle climate and smaller
laboratory-based test cells in identical
conditions, the research showed thermal
advantages offered by brick construction:
• The ability of brick construction to store
heat, and delay heat transfer (thermal lag)
increases thermal value beyond merely
their measured insulative properties
(R-value).
• There was no correlation between R-values
and energy consumption; walls with
thermal mass performed better than
lightweight walls with an R-value three
times greater.
• Brick veneer exceeded the thermal
performance of lightweight construction
with the lightweight building being the
worst performer in all seasons.
• R-values alone cannot be used as a
sole predictor of thermal performance
with no correlation between R-value and
energy use.
Note the test cells results are shown for a
Newcastle climate. Check the full report,
which is listed at the end of this article, for
details.
Cavity brickwork
The report notes that
insulated cavity brickwork construction
“provided the most consistent and
predictable behaviour” of any of the wall
types.When air-conditioned, this
construction required less energy to keep it
within the comfort range.This is linked to the
ability of the internal brickwork skin to assist
in regulating temperature.
Brick veneer
Often thought of as merely
cosmetic, brick veneer offered a heat lag of
four hours and when insulated has been
shown in the research to provide an
improvement in thermal comfort over that of
lightweight construction. Brick veneer was
shown to have high summer temperatures,
though adding cavity insulation helps reduce
these.Adding internal thermal mass can also
improve this performance.
Reverse brick veneer
Often thought of as
the ‘holy-grail’ in building, the brick veneer is
placed on the inside where it can be best
utilised to regulate thermal comfort.Testing
showed the performance of insulated reverse
brick veneer was marginally inferior to
insulated cavity brickwork due to the lack of
thermal mass in the external skin. It was more
vulnerable when exposed to high solar gain
than insulated cavity brick which required less
energy consumption under controlled
conditions.
Lightweight (timber-framed) construction
While insulation in lightweight walls reduces
the amount of heat flux through external walls,
the lack of significant thermal lag means
peak internal temperatures will more closely
follow external conditions. Of the four wall
constructions tested, the lightweight assembly
had the highest daytime peaks and the
widest divergence in daily internal
temperatures. Even though the lightweight
wall has a higher R-value than the insulated
cavity brick, the lack of thermal mass means
decreased comfort levels for occupants.And
when air-conditioned, the lightweight test
building “consistently had the highest energy
consumption.”
The inability of lightweight construction to
store heat means it is unable to store
overnight ‘coolth’ to assist in moderating
summer temperatures.
Maximising comfort
with brick
Designers may not control the energy used
by appliances in the home directly, although
through good design they can offer a
significant improvement in thermal comfort
for the life of their buildings.
Increasing internal thermal mass
The
thermal capacitance of bricks can be used
with greatest effect in climate zones that
have large diurnal temperature shifts.The
Newcastle research highlights the value of
insulated cavity brick construction to
produce the most stable thermal comfort of
those tested.The housing market has
traditionally favoured brick for its
appearance and low maintenance, though
this is often achieved with brick veneer at
lower cost.
The goal for designers who wish to increase
energy efficiency is to maximise internal
mass where passive design will allow this
mass to moderate temperature. Building
internal partition walls of brickwork,
particularly in and adjacent to the living
areas of the building where most heating
and cooling loads are incurred, can give a
boost to energy efficiency. By comparing
constructions of hybrid wall types, the
research showed that significantly improved
thermal performance could be achieved.
Insulated walls
The Newcastle research
illustrates the value of insulating between the
external and internal skins of brick walls to
impede the transference of unwanted heat
through the external skin on hot days, and
preserves the warmth or ‘coolth’ retained by
the thermal mass on internal skins.
Windows
Glazed windows and doors, in
thermal terms, are holes in the wall, allowing
unwanted heat loss in winter.The research
showed the addition of glazing can also add
unwanted heat loads to internal and
external wall faces in summer. Careful
placement, sizing and shading are needed
to maximise thermal comfort in rooms while
still allowing for views and natural light.
In warm climates
The research noted the
considerable amount of heat radiated back
into the environment by the exterior face of
brick walls.This can be assisted further by the
use of light-coloured bricks to reduce heat
absorption and shading external walls to
limit the amount of direct sun.
To allow for the night purging of built-up
daytime heat, the design of cross-ventilation
should consider openings that can be left
open without breaches of security or the
penetration of inclement weather, insects or
rodents.Windows for cooling that can’t be
left open will potentially compromise the
value of the thermal systems.
Figure 2:
Combined total energy consumption (all seasons) for the four test buildings at
The University of Newcastle.The heating and cooling demands in the insulated cavity brick
building were the lowest, followed by insulated brick veneer.
(Source: Energy Efficiency and the Environment: The Case for Clay Brick,
published by Think Brick Australia.)
Energy Consumption (MJ)
2500
3000
3500
2000
1500
1000
500
0
CB
InsCB
InsBV
InsRBV
Total
Heat
Cool