Protection (T4) Flashcards
Building as a system
requires designers to consider the interactions between the for primary elements comprising the system
protection for buildings
- Building envelope (enclosure system)
- Occupants (humans, animals and/or plants)
- Building services (electrical/mechanical systems)
- External environment (site with its landscape and services infrastructure and micro-climate)
Integrated dynamic system
- Large number of materials, components equipment, and assemblies must be properly integrated or achieve a high-performance building
- Most performance problems involve the building envelope.
Functions of the building envelope
- Waterproof to wind-driven moisture
- Permit access in and views out
- Admit natural light
- Avoid summer overheating
- Retain heat in winter
- Be free from damp and condensation
- Provide adequate ventilation
- Permit entry of electricity, fuel and water supplies and exit of waste
- Provides structural support
Physical mechanisms associated with climate and weather
For primary mechanisms
- Heat flow = conductive, convective and radiative
- Air flow = air flow across and within the building envelope due to air leakage and ventilation
- Moisture flow = flow of water and vapor across and within the building envelope
- Solar radiation = influence of solar radiation on the opaque and transparent envelope components
Rain and moisture penetration
- Includes moisture vapour and snow
- Permanent damage mainly occurs to finishes rather than the construction (unless major errors are made)
- In solid walled construction rainwater soaks in, spreads and then evaporates
- Traditional details seek to protect vulnerable aspects & locations
- Long term water penetration associated with timber failure (rot) and corrosion of metallic components
- Guidance available in Building Regulations Part C2 - resistance to moisture
Factors affecting ‘as-designed’ envelope performance
Regulatory and planning constraints which must be considered
- Structure
Approved document part A – structure (loading, ground movement, disproportionate collapse) - Containment of fire
- Approved documents part B – fire safely
- British standards e.g. BS 476-10:2009
- Conservation of fuel and power
- Approved document L (specifies backstop U-values and minimum carbon compliance targets)
- Ventilation
- Approved document F (specifies acceptable means of ventilation and minimum rates)
Factor’s affecting ‘as-built’ envelope performance
- Integrated design must consider real-world constraints inclosing construction methods, buildability and quality control during construction phase
Quality assurance = two main objectives - Clean robust brief, integrate quality control during design and construction
- Construction sequencing, on-site checks, compliance testing
House construction methods
- ‘traditional’ methods = typically masonry
- Modern methods of construction (MMC)= offsite manufacturing
- Others = alternative, hybrid, natural or more sustainable
Traditional methods of construction
- Masonry = defined as brick and block construction
- Built in situ using fired clay bricks or concrete blocks and mortar
MMC
- Off-site production methods
- Advantage = factory conditions, fewer material delivers, reduced construction time, reduced labour, reduced energy use
- Model: timber, straw and hemp panel system that can be produced, then delivered and erected on-site.
- Timber ‘cassettes‘(e.g. Facet Homes); major components of superstructure are manufactured offsite
- Structural insulated panel (SIP) are a lightweight sandwich construction method
- Common aim = reduction in construction time on site
Insulating cavity walls
- HW block – 100mm filled cavity = U=0.32 W/m2K
- LW block, 75mm filled cavity U=0.35 W/m2K
- Remedial filled cavity wall
- Installer drills a small hole then blows insulation into the cavity, when finished they will then fill the holes
Timber frame detail
- Mineral wool insulated stud wall system
- Polystyrene foam insulated floor system
- External wind barrier membrane
Suspended concrete floor (‘block and beam’)
- Used in areas with a high-water table or on sloping sites
- Usually insulated internally
- Continuous external insulation retains the thermal mass of the floor slab with in the thermal envelope
Roof insulation
- Cheap
- Easy to apply
- Cost effective
- Thickness 150mm
- U-value ≈0.25W/m2K