Energy Efficient: thermal mass benefits
· High
thermal mass of precast concrete enables it to absorb, store and later radiate heat.
· Using precast concrete in
passive solar designs allows natural heating in winter and cooling in summer, thereby reducing the need to rely on artificial heating and cooling.
Improved internal building amenity
· Use of precast concrete can even out internal diurnal building temperatures.
· Some precast systems (such as
TermoDeckR) can improve indoor air quality, providing fresh air inside the home.
Durable, long life, reuseable, low maintenance structures
· With a long life expectancy of up to 100 years, precast structures are durable.
· Precast structures can be reused, extended and refitted internally. Structures do not need to be demolished and can simply be renovated internally conserving resources, reducing waste and landfill.
· Precast is easy to keep clean, requiring minimal maintenance.
· Precast is tough and can withstand wear and tear, requiring minimal repairs.
· Precast concrete can be moulded into almost any form and finish. Careful design of precast concrete buildings increases the likelihood of reusing the building over again.
· Precast concrete gains strength as it ages, won’t shrink, distort or move and will not deteriorate with exposure to climatic change.
· Being flood resistant, precast concrete does not erode or rot therefore is suitable for river and coastal barriers to protect against high tides and storms.
· As a hardy waterproof construction method, precast concrete underground pipes transport sewerage and clean water across the country.
· Precast concrete is impact resistant and hard to cut, offering security and protection against terrorist acts.
Locally supplied
· Materials used by precast manufacturers are usually supplied locally. This reduces haulage and fuel costs and also diverts resources from landfill.
· Precast elements are usually locally manufactured and supplied to sites meaning reducing haulage and fuel costs.
· Local highly skilled erection crews erect precast concrete elements safely on site.
Uses less concrete, cement and steel
· Less concrete and steel are required for precast concrete because of its higher quality.
· Less concrete is used in precast flooring systems such as hollowcore, bubbledeck and Ultrafloor.
· Precast allows reduced levels of cement in the concrete mix due to higher quality manufacturing processes.
· Long spans of precast flooring mean reduced material use for supporting columns.
Minimises waste during manufacture and on site
· Manufactured in reusable moulds.
· Most waste during manufacture is recyclable.
· Exact elements are delivered to site.
· Less site air pollution, noise and debris.
Reuses waste resources and recycled materials
· Waste materials (such as slag and fly ash) which would otherwise be used in landfill can be incorporated into the precast mix design.
· Recycled aggregate can be incorporated in to the precast mix design.
· Recycled steel can be used in the manufacture of precast elements.
· Grey water and stormwater runoff can be used in the precast concrete mix design, thereby reducing mains water consumption.
Recyclable precast elements
· Precast concrete elements can be crushed and reused as aggregate for road bases or construction fill, providing economic and environmental savings.
Faster construction
· Precast concrete allows other trades to begin work more quickly, speeding the construction time and saving costs.
· Fast construction on site means less disturbance for surrounding properties.
· Precast elements can be delivered just in time for erection, reducing unnecessary handling and equipment use.
Acoustic performance
· The high thermal mass of precast concrete assists with sound insulation to reduce noise and absorb noise impact.
· Noise walls provide an effective sound barrier between roads and urban noises, and outdoor and indoor spaces and provide more aesthetically pleasing and comfortable living environments.
· Precast concrete walls can create.
Fire resistant
· Precast concrete is non-combustible, does not melt and therefore does not require additional fire-proofing applications.
· Precast concrete does not emit toxic fumes under fire and can limit smoke spreading in buildings.
Environmental benefits
· Precast concrete is an inert substance which does not emit or give off gases or compounds. This is a huge relief to allergy sufferers.
· Precast does not attract mould or mildew.
· Precast concrete absorbs CO2.
· Being termite proof means the unlikelihood of requiring chemical spray to reduce termites and vermin which is safer for the environment.
· As landscaping and street furniture features, planters increase biodiversity apart from providing a green environment for birds and a pleasant communal meeting place.
OHS benefits
· Less trades on site means safer sites with less equipment, workers and materials.
· Reduced congestion - construction sites are cleaner and tidier, with minimal waste on site.
· Precast floors can provide a safe immediate working platform for the erection crew.
Sustainable Design Solutions:
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Specific Examples where Sustainable Designs using Precast Construction can make a Considerable Environmental Impact.
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Design Strategy
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Sustainability Issue
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Use hollowcore floor planks as ducting system to channel air around the building
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The longitudinal ducts in the floor/ceiling increase the effectiveness of the building mass as an energy store and serve as heat exchangers between rooms and spaces having different temperatures.
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Use prestressed concrete design for structural elements
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Prestressed precast concrete allows the designer to create longer spans, using less material which may use less concrete than does conventional design.
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Use thermal mass in combination with appropriate insulation levels in walls
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Thermal mass with insulation provides energy benefits that exceed the benefits of mass or insulation alone in most climates.
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Use precast as sustainable design for fire resistance
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Precast concrete is non-combustible and does not require additional fire-proofing applications.
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Re-use of intact precast concrete elements for building function changes or relocation of building
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Wall panels can be designed to be disassembled, saving materials and extending service life of panels.
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Maximise the benefit of re-use of moulds
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Steel moulds have long life span providing thousands of re-uses and also reduces waste.
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Use loadbearing precast
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Efficient use of materials due to combining structural, thermal and acoustic functions.
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Use colouring oxides and polished finishes for precast elements
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Eliminates additional trades (painting) and reduces maintenance.
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Use self-shading precast wall elements
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Reduces heat transfer.
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Use self-compacting concrete
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Minimises the energy used to place concrete.
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Source: Precast Concrete Handbook, edition 2, 2009.
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Insulated Sandwich Panels
Sandwich panels are comprised of three layers - an outer thinner skin of non-structural reinforced precast concrete, an insulation layer and an internal layer of structural reinforced precast concrete (which creates the thermal mass). The three layers are held together by non-conductive connectors (or ties). These connectors allow the layers to move independently of each other, allowing for thermal expansion and contraction without affecting the structural integrity of the wall.
Sandwich panels offer reductions in energy usage for both heating and cooling, and when combined with other energy saving elements such as double glazed windows may eliminate the need for air-conditioning or heating all-together in some climates.
Produced in a controlled factory environment, precast concrete sandwich panels are similar in appearance to solid precast panels, with the distinct difference being their thermal insulating properties which make them ideal for air-conditioned spaces and residential dwellings.
Unlike most alternative systems, sandwich panels have the majority of their thermal mass on the interior of the building. Their high thermal storage capacity makes them capable of storing and releasing heat very slowly, thereby minimising fluctuations in the internal temperatures of the building. Sandwich panels also insulate against noise transmission of both airborne and impact sound. In addition they are fire resistant and incredibly durable.
Sandwich panels can be used as both the external and internal wall. They can be used as cladding or as a structural element to the building and can have a variety of architectural finishes.
TermoDeckR
TermoDeckR is a fan-assisted, heating, cooling and ventilation system that uses the high thermal mass of structural, hollowcore floor slabs through which warmed or cooled fresh air is distributed. The supply air passes through the hollow cores at low velocities, allowing prolonged contact between the air and the slabs. This enables the slabs to behave as passive heat exchange elements that release heat to, or absorb heat from, the air in the slabs. The temperature difference, between the slab and the air that exits the slab, is not more than 1 and 2 degrees Celsius.
The air is further tempered by contact with the exposed mass surfaces in the room, of which the major proportion is the TermoDeckR soffit. The slabs also serve as heat exchanging elements between rooms with varying room temperatures, because the slabs can span up to 18 metres enabling them to cover more than one room.
If a building is well insulated, air tight and has heat recovery, the utilisation of thermal mass of the TermoDeckR in combination, will produce a very efficient control solution. As a result, a building's requirements for cooling machinery, storage heaters and related equipment will be less, and costs significantly reduced.
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