Assessing a residential house construction project

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Scenario
You are part of a design team for a small building contractor tasked with assessing a residential
house construction project, your focus will be to look at construction methods and materials.

Your client is an individual who is looking for a high level of sustainable technologies to be
incorporated in their project, to achieve low embodied energy, high levels of insulation and good
airtightness, energy efficiency, low maintenance and a long service period.

The project consists of detached house to be built on soft clay, which is classed as a high shrinkable
clay soil, the building is not expected to exceed 30kN/m. Although, soil type has been established,
please state your assumed local climate conditions as this will influence your assessment of
methods and materials.
Task
Your assessment will take the form of a technical report and will be aimed at a client with some
basic knowledge of standard construction methods. The technical report should contain an
introduction, some titled sections for discussion topics with illustrations, tables for comparison and
conclusions.
a. For each of the four primary elements (listed below), pick two methods of construction
(including the materials) that would be the most sustainable in the long term, compare and
contrast these and recommend one:
• Foundation type
• Structural ground floor
• Structural external walls
• Roof structure.

 

For each element, focus on methods and materials that are appropriate for your country
(local climatic conditions). Clearly describe the technology, and provide justification for your
recommended choice, explaining how it satisfies key performance criteria and why it is best
suited to local circumstances.
b. Outline which building services system would give the best balance between energy
efficiency, running costs and carbon dioxide emissions. Your discussion should focus on
one specific item, from the following:
• Cooling and ventilation systems; or
• Space heating systems; or
• Hot water systems.

Provide at least one illustration with annotation for each of the following five drawings
(sketches) of the report. These illustrations should be in the appropriate discussion topic of
your technical report and include (as a minimum):
• a composite sketch or suitable illustration (with annotations) of the foundation; and
• a composite sketch or suitable illustration (with annotations) of the ground floor with
footings and Damp Proof Course (DPC) and Damp Proof Membrane (DPM); and
• a composite sketch or suitable illustration (with annotations) of the exterior structural
wall; and
• a composite sketch or suitable illustration (with annotations) of the roof with eaves
(fascia and soffit) and wall plate detail; and
• a schematic diagram related to the building services outlined.

Sample Solution

Sustainable Construction Methods for Residential House: A Technical Report

Introduction:

This report outlines sustainable construction methods and materials suitable for a detached house built on soft clay with a maximum load of 30kN/m². The client prioritizes low embodied energy, high insulation, airtightness, energy efficiency, low maintenance, and a long lifespan. Local climatic conditions are assumed to be [insert details – temperate, hot & humid, etc.].

Foundation Type:

  • Slab Foundation: A concrete slab directly cast on a prepared, reinforced sub-grade.
  • Engineered Pile Foundation: Driven piles transfer building weight to a lower, stable soil layer.

Comparison:

Feature Slab Foundation Engineered Pile Foundation
Sustainability High embodied energy in concrete Lower embodied energy in piles, minimal excavation
Suitability for Clay Not ideal for shrinkable clay, prone to cracking Suitable for unstable soils, minimizes settlement risk
Cost Generally lower initial cost Higher initial cost

Recommendation: Engineered Pile Foundation. While the initial cost is higher, it offers superior stability on shrinkable clay, reducing the risk of cracking and ensuring long-term performance.

Illustration:

  • A sketch showing a side-by-side comparison of a slab foundation (concrete slab on sub-grade) and an engineered pile foundation (piles driven into stable soil layer).

Structural Ground Floor:

  • Suspended Timber Floor: Timber joists supported on pre-cast concrete beams or timber walls.
  • Insulated Concrete Floor (ICF): Pre-cast hollow concrete units with integrated insulation filled with concrete.

Comparison:

Feature Suspended Timber Floor Insulated Concrete Floor (ICF)
Sustainability Renewable timber resource, good thermal insulation High embodied energy in concrete, excellent thermal insulation
Suitability for Clay Requires stable sub-floor to prevent joist deflection Less susceptible to movement on clay due to rigid structure
Airtightness More challenging to achieve airtightness Excellent inherent airtightness

Recommendation: Insulated Concrete Floor (ICF). While ICF has higher embodied energy, its superior thermal insulation, airtightness, and suitability for clay soils make it a better long-term choice.

Illustration:

  • A sketch comparing a suspended timber floor (showing joists, beams, and subfloor) with an ICF floor (showing pre-cast units filled with concrete).

Structural External Walls:

  • Timber Frame Construction: Timber studs with insulation and cladding materials.
  • Straw Bale Construction: Compressed straw bales with internal and external render finishes.

Comparison:

Feature Timber Frame Construction Straw Bale Construction
Sustainability Renewable timber resource, good insulation Excellent thermal insulation, low embodied energy
Suitability for Climate Can be adapted to various climates Particularly suited to moderate climates
Durability Requires proper moisture management Proper detailing crucial for long-term durability

Recommendation: Straw Bale Construction. Assuming a moderate climate, straw bale offers exceptional thermal insulation, low embodied energy, and good structural performance with proper detailing.

Illustration:

  • A sketch comparing a timber frame wall (showing studs, insulation, and cladding) with a straw bale wall (showing bales, internal render, and external render).

Roof Structure:

  • Timber Truss Roof: Pre-fabricated triangular trusses supporting roof deck and coverings.
  • Light Gauge Steel Frame with Rafters: Cold-formed steel sections forming a lightweight frame with timber rafters.

Comparison:

Feature Timber Truss Roof Light Gauge Steel Frame with Rafters
Sustainability Renewable timber resource Steel is recyclable, potentially lower embodied energy
Span Capabilities Can handle larger spans Limited span capabilities compared to trusses
Fire Resistance Requires additional fireproofing measures Steel offers inherent fire resistance

Recommendation: Timber Truss Roof. While steel offers recyclability, timber trusses are more suitable for larger spans commonly found in detached houses. Fireproofing considerations can be addressed during construction.

Illustration:

  • A sketch comparing a timber truss roof (showing trusses, decking, and coverings) with a light gauge steel frame with rafters (showing steel sections, rafters, decking, and coverings).

Building Services System: Space Heating

A highly efficient Air Source Heat Pump (ASHP) system is recommended for space heating. ASHPs extract heat from the ambient air and transfer it to the building interior, offering excellent energy efficiency and lower running costs compared to traditional gas boilers.

Illustration:

  • A schematic diagram of an ASHP system showing the outdoor unit, indoor unit, hot water storage tank (if applicable), and distribution system (hydronic or air ducts).

Conclusion:

This report explores

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