Thermal Performance of Opaque Facade Elements Flashcards
Energy Balance of a building
Is a systematic accounting of all energy flows
- Including all heat gains and losses in a building “System”
3 Heat Flows for a buildings energy Balance
- Heat (Thermal) Demand
- Heat Storage
- Heat Loss/gain
Heat (Thermal Demand)
Heat supplied or removed by HVAC equipment
Heat Storage
Building Heat Capacity
What contributes to Heat Gain in a building?
Solar radiation
People
Equipment
Lights
Heat gain and loss mechanisms
Conduction/Convection. Walls, roofs, Glazing
Conduction. Ground
Air exchange
Define Building envelope
The part of the building that physically separates the exterior environment for the interior environment
Building envelope compentents
Walls
Roof
Windows and door
Floor
3 Design features affecting energy Performance
Architecture
Thermal Performance of opaque elements
Thermal Performance of Transparent Building Elements
Architecture
Orientation
Geometric Proportions
Things that change the Thermal Performance of opaque (Not see through) elements
Insulation Materials
Thermal Bridges
Thermal Mass
Reflectance of exterior Materials
Air leakage
Thermal Performance of transparent building elements
Windows
Sun shading
Air leakage
Orientation
Maximise south and north façade exposure for daylight harvesting
Minimise western exposure as its hard to shade from the sun
Benefits of good orientation
Lower lighting costs
reduce heating loads
Natural ventilation Benefit
Thermal properties of opaque materials that determine thermal behaviour of the building envelope
Conductivity
Specific Heat
Thickness
Density
Exposed material Properties
Roughness
Thermal Absorbance
Solar Absorbance
Surface Reflectance
Surface reflectance and different climates
cold = Dark colours to absorb heat
Warm = Light colours in order to reflect the light.
To reduce heat transfer by conduction, an insulation material should:-
Less solid material in comparison to void
The slod material should consist of thin connecting walls or discontinuous fibres
To reduce heat transfer by convection, an insulation material should:-
Contain small voids or air pockets within which air movement is minimised
Reflective foils
Restrict the absorption and emission of radiant heat energy
Doubles as an air and vapour control barrier
Super Insulation Materials means that a material will have
Long term performance of insulating materials in building components and systems
Thermal bridges
- Full or partial penetration of the building envelope by materials with a different thermal conductivity
- A change in thickness of the fabric
- A difference between internal and external areas, such as occur at wall/floor/ceiling junctions
Negative impacts of thermal bridges
Condensation of vapour and mould development
Deterioration of building elemants
Interstitial Condensation
Deterioration of internal air quality
Heat/Energy Loss
