Construction Technology
Technical Report: Sustainable Construction Methods and Materials for Residential House
Introduction:
This report assesses construction methods and materials suitable for a sustainable, low-maintenance residential house to be built on soft clay with a maximum load of 30kN/m². The client prioritizes sustainable technologies for low embodied energy, high insulation, airtightness, and energy efficiency.
Local Climate Assumptions (temperate climate):
- Mild winters with occasional freezing temperatures.
- Warm summers with moderate humidity.
- Moderate rainfall throughout the year.
a. Sustainable Construction Methods and Materials:
i. Foundation Type:
1. Pile Foundations:
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Description: Precast concrete piles are driven into the soft clay until they reach a stable load-bearing stratum. A pile cap distributes the weight of the building across the piles.
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Sustainability Considerations: High embodied energy in precast concrete piles. Requires specialist equipment for installation.
2. Engineer Designed Shallow Foundations:
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Description: A reinforced concrete raft foundation spread across a wider area to distribute the building load on the clay.
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Sustainability Considerations: Lower embodied energy compared to pile foundations. Requires careful engineering design to optimize concrete usage.
Recommendation: Engineer Designed Shallow Foundations are recommended. While concrete has embodied energy, careful design can minimize its use. This method avoids the high embodied energy and disruption of pile driving.
Illustration 1: Foundation Systems
ii. Structural Ground Floor:
1. Suspended Timber Floor:
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Description: Timber joists supported on brick or concrete walls with a subfloor and finished floor above.
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Sustainability Considerations: Renewable timber resource, but requires treatment for durability.
2. Insulated Concrete Slab:
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Description: A layer of concrete poured over a layer of insulation and a damp-proof membrane (DPM).
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Sustainability Considerations: Concrete has high embodied energy, but the insulation layer improves thermal performance and reduces heating/cooling needs.
Recommendation: Insulated Concrete Slab is recommended. While concrete has embodied energy, the excellent thermal performance reduces long-term operational energy and carbon emissions.
Illustration 2: Ground Floor Construction
iii. Structural External Walls:
1. Cavity Wall Construction:
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Description: Two brick leaves separated by a cavity filled with insulation.
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Sustainability Considerations: Brick production has embodied energy, but the cavity provides good insulation.
2. Timber Frame Construction with Cladding:
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Description: Timber frame with insulation panels and external cladding like weatherboard or brick slips.
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Sustainability Considerations: Renewable timber resource, offers good insulation properties with careful selection of insulation materials.
Recommendation: Timber Frame Construction with Cladding is recommended. Timber is a renewable resource, and the construction method allows for thicker insulation layers compared to cavity walls, leading to superior thermal performance.
Illustration 3: External Wall Construction
iv. Roof Structure:
1. Traditional Trussed Rafters:
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Description: Timber trusses support the roof covering and ceiling.
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Sustainability Considerations: Renewable timber resource, but complex trusses can require more material.
2. Prefabricated Timber Roof Cassettes:
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Description: Factory-made insulated panels combining roof structure, insulation, and an internal ceiling finish.
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Sustainability Considerations: Efficient use of timber with good insulation properties due to factory-controlled manufacturing.
Recommendation: Prefabricated Timber Roof Cassettes are recommended. They offer excellent thermal performance, efficient use of materials due to prefabrication, and faster construction times.
Illustration 4: Roof Construction
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