Wall Cladding
Insulation
Wall Cladding
ELEMENT:
James Hardie 'Hardiflex' fibre cement sheet cladding 6mm thick
Stramit corrugated steel wall sheeting; Colorbond finish
AIM:
The role of the external wall cladding is to provide a barrier to protect
the inside from excessive heat gain from the sun and the external environment.
The walls are designed to reflect as much sunlight away from the building
as possible, which means less heat is absorbed into the wall.
STRATEGY:
Minimise Life Cycle Maintenance
Fibre cement sheeting is made from cellulose fibre, portland cement
and sand. The fibre cement is non-combustible, termite resistant, easy
to paint and resistant to weathering.
Corrugated steel wall sheeting is hard wearing, durable and has a very
good product life span. Both steel sheeting and fibre cement sheeting
are lightweight and flexible which makes them easy to install and to handle
on site.
Optimise Passive Design
The internal temperatures of the house can be moderated by the assistance
of insulation, shading and reflected light. Expandable reflective foil
insulation is used in the walls to help reduce the amount of heat penetration
due to the sun striking the wall.
Shading of the walls with sufficient roof overhangs also helps to control
the amount of heat absorbed by the wall.
Painting the walls light colours tends to reflect the solar heat away
from the house rather than absorb heat.
REFERENCE:
Hyde, R, Climate Responsive Design. A Study of Buildings in Moderate
and Hot Humid Climates. E and FN Spon, London 2000.
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Insulation
ELEMENT:
Wrenn Industries Foil Batts
AIM:
Insulation installed in the walls and roof helps to regulate the flow
of heat through the walls and roof of the building. The purpose of the
roof and walls for a house on the Gold Coast is to exclude heat from the
summer sun and hold warmth inside in winter. The foil batts used are a
combination of a reflective foil and bulk insulation. The reflective foil
reflects the heat to the outside and the bulk insulation resists heat
loss from the inside.
If insulation is installed to help moderate the temperatures inside the
house the need to use electrical appliances or systems to cool or heat
the house is less.
STRATEGY:
Optimise Passive Design
The strategies adopted by the house to reduce the transfer of radiant
heat from the sun through the skin of the building are solar defences
and lightweight construction.
The importance of designing a solar defense system for the building was
recognised as a major priority. Direct solar radiation creates a heat
load of 1000 Watts per m2. Heat gain to the building through the envelope
is avoided at all costs. The elements used in the house are as follows.
- A R rating of 2.5 for walls and roof. To achieve this resistance
rating the insulation used is concertina expandable reflective foil
insulation which is a combination blanket and foil insulation
- Shading to windows, doors and external spaces to provide solar exclusion
in summer
- Reduced number of west facing windows as these create a large heat
gain
- Bathroom and service spaces located to the west to act as a buffer
from westerly sun and heat gain
- Light external colours to reflect and reduce heat gain
- Tinted glass in the windows to reduce glare and heat gain thorough
the windows by reflection and reduced transfer.
- Large unshaded glazed areas are avoided as these have low resistance
to heat gain
Lightweight construction is made of materials and components that have
a low mass. Timber and steel roofing is an example of a low mass roofing
system. Heavy weight construction is the converse, comprising building
materials such as masonry and concrete. The mass of the building affects
the thermal performance and the way the building works with climate, hence
buildings with a high mass store heat whilst low mass materials readily
release heat back to the atmosphere.
In the case of the Healthy Home a combination of lightweight construction
elements were chosen for their ability to heat up and cool down quickly.
This means that on hot summer nights as the external temperatures drop
the building will respond quickly and also cool down improving thermal
comfort. In addition the effect of the ground as a source of thermal mass
was also used.
The elements of lightweight construction that have the main influence
of this response are:
- Suspended timber floor with a skirt around the perimeter to retain
heat in winter
- Lightweight construction for bedrooms
REFERENCE:
Hyde, R, Climate Responsive Design. A Study of Buildings in Moderate
and Hot Humid Climates. E and FN Spon, London 2000.
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