The
fact that ambient air temperature, lad surface and sea surface
temperatures are rising across the Australian continent can no
longer be denied.
 |
GRAPH: Australian Bureau of Meteorology
|
In
New
South Wales generally average maximum temperatures in the month of
January 2024 ranged from around 24°C
to
36-39°C,
spiked by days on end of heatwave temperatures which often broke
temperature records for individual localities.
 |
MAPPING: Australian Bureau of Meteorology
|
In
the north-east
coastal zone of the state the minimum air temperature was 1°C
higher and maximum air temperature 1-2°C higher
than they were between 1981-2010.
In
January the highest
Northern Rivers region minimum & maximum recorded daily
temperature range
was:
Evans
Head
24.8—38°C
Grafton
24.5—37.6°C
Yamba
25.6—37.2°C
Murwillumbah
27.1—36.2°C
Casino
27.1—36.2°C
Lismore
24.5—35.6°C
Tabulam
23.0—34.9°C
Byron
Bay
25.6—32.7°C
Ballina
24.9—34.2°C
Note:
These are the nine official Bureau of Meteorology weather stations in
the Northern Rivers region.
Yet
despite all this new subdivision schemes and housing designs are
paying little more than lip service to sustainability and mitigating the
thermal load of both the internal road networks of these subdivisions
or the collective & individual loads of dwelling contained there
in.
Apparently,
multi-dwelling structures that increasing look like a collection of
boxes are skating through BASIX
requirements on the presumption that each individual box within these
boxes will be fully air conditioned at some point before occupation or that if ceiling fans are fitted to some of the rooms then this will mitigate heat.
An
assumption which:
(i)
takes no account of the increasing stress air conditioning places on a
household's cost of living. Because the price per kilowatt hour &
associated charges of residential electricity supply continues to
rise and commonly these multiple dwelling boxes are not built with
any rooftop solar power grid to mitigate cost;
(ii)
completely ignores the increasing risk of destructive storms causing
levels of damage to power supply infrastructure that cuts power
supply to both collections of streets or entire towns for days/weeks
at a time. As occurred in heatwave conditions in 2024; and
(iii)
appears to leave the thermal load of closely clustered internal
roads out of the equation completely.
I
expect the latest collection of boxes being considered by Clarence
Valley Council will also get the nod because I have yet to see this
local government apply the full suite of climate change policies to every development application before deciding consent. The heat footprint of an application rarely rates a mention in Council-in-the-Chamber debates or elicits questions to senior staff attending. Neither are there many mentions of the heat island affect caused by new roads, pavements and driveways. Nor does the wind resistance factor of a proposed building arise - and given the entire Clarence Coast is now in a cyclone risk zone that borders on the negligent when assessing new development applications.
 |
| Artists impression of street view of 6 Yamba Road, Yamba proposed subdivision. IMAGE: BDA |
Set
out below are some basic facts about how the freestanding houses,
town houses, duplexes, units and flats we live in attract and retain heat.
Australian
Government, Your
Home, retrieved 19
February 2024:
Passive
Design
What
is thermal mass?
In
simple terms, thermal mass is the ability of a material to absorb,
store and release heat. Materials such as concrete, bricks and tiles
absorb and store heat. They are therefore said to have high thermal
mass. Materials such as timber and cloth do not absorb and store heat
and are said to have low thermal mass.
In
considering thermal mass, you will also need to consider thermal lag.
Thermal lag is the rate at which heat is absorbed and released by a
material. Materials with long thermal lag times (for example, brick
and concrete) will absorb and release heat slowly; materials with
short thermal lag times (for example, steel) will absorb and release
heat quickly.
Thermal
mass
Thermal
mass, or the ability to store heat, is also known as volumetric heat
capacity (VHC). VHC is calculated by multiplying the specific heat
capacity by the density of a material:
The
higher the VHC, the higher the thermal mass.
Water
has the highest VHC of any common material. The following table shows
that it takes 4186 kilojoules (kJ) of energy to raise the temperature
of 1 cubic metre of water by 1°C, whereas it takes only 2060kJ to
raise the temperature of an equal volume of concrete by the same
amount. In other words, water has around twice the heat storage
capacity of concrete. The VHC of rock usually ranges between brick
and concrete, depending on density. Most common building materials
with high VHC also tend to be quite conductive, making them poor
insulators.
Thermal
lag
How
fast heat is absorbed and released by uninsulated material is
referred to as thermal lag. It is influenced by:
conductivity
of the material
difference
in temperature (known as the temperature differential or ΔT)
between each face of the material
thickness
of the material
surface
area of the material
texture,
colour and surface coatings (for example, dark, matte or textured
surfaces absorb and re-radiate more energy than light, smooth,
reflective surfaces)
exposure
of the material to air movement and air speed.
To
be effective in most climates, thermal mass should be able to absorb
and re-radiate close to its full heat storage capacity in a single
day–night (diurnal) cycle.
In
moderate climates, a 12-hour lag cycle is ideal. In colder climates
subject to long cloudy periods, lags of up to 7 days can be useful,
providing there is enough solar exposed glazing to ‘charge’ the
thermal mass in sunny weather.
Embodied
energy
Some
high thermal mass materials, such as concrete, cement-stabilised
rammed earth, and brick, have high embodied energy when used in the
quantities required. This highlights the importance of using such
construction only where it delivers a clear thermal benefit. When
used appropriately, the savings in heating and cooling energy from
the thermal mass can outweigh the cost of its embodied energy over
the lifetime of the building. Consideration should be given to using
high thermal mass materials with lower embodied energy, such as
water, adobe or recycled brick.
Why
is thermal mass important?
When
used correctly, materials with high thermal mass can significantly
increase comfort and reduce energy use in your home. Thermal mass
acts as a thermal battery to moderate internal temperatures by
averaging out day−night (diurnal) extremes.
In
winter, thermal mass can absorb heat during the day from direct
sunlight. It re-radiates this warmth back into the home throughout
the night.
In
summer, thermal mass can be used to keep the home cool. If the sun is
blocked from reaching the mass (for example, with shading), the mass
will instead absorb warmth from inside the home. You can then allow
cool breezes and convection currents to pass over the thermal mass
overnight to draw out the stored energy.
Conversely,
poor use of thermal mass can reduce comfort and increase energy use.
Inappropriate thermal mass can absorb all the heat you produce on a
winter night or radiate heat to you all night as you try to sleep
during a summer heatwave.....
