SUPER INSULATION

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SUPER INSULATION
Jake Roos Energy Efficiency Surveyor
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Overview

• The building envelope
• What determines thermal performance?
• Insulation and U-values
• U-values of typical elements
• Infiltration (air leakage)
• Energy ratings
• Thermal performance of different houses
• Achieving super insulation

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The building envelope

• The elements of the building that enclose the
  heated space
• Roof, walls, windows, floor, doors
• The ability of a building envelope to prevent
  heat-loss or heat gain is its thermal
  performance

• Super Insulation means little or no heating is
  required

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What determines thermal performance?

• Size of dwelling
• Shape/surface-area to volume ratio
• Climate and exposure
• Insulation value of elements
• Air-tightness

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Insulation and U-values

• Heat loss rate of element is equal to
• Temperature difference x area x U-value
• U-value is determined by the sum of the thermal
  resistances R the components of the element
• The lower the U-value, the better
• Uwall 1/(Rsurface1 R1 R2 R3 R4
  Rsurface2)

Toutside
Tinside
Rsurface1
Rsurface2
R1
R2
R3
R4
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Insulation and U-values (cont.)

• For solid materials, insulation value is affected
  by thickness and conductivity
• For outer surfaces, insulation value is affected
  by colour (emissivity) and air-flow
• For air gaps, insulation value is affected by
  emissivity of each surface, gap width and the
  type of gas in the space

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U-values of typical elements
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Infiltration (air leakage)

• Heat is lost/gained by air leaking through gaps
  in the fabric
• Air tightness is determined by how well the
  envelope was built
• Air tightness tested by pressurising dwelling to
  50pa with a blower door, measuring air flow rate
  exchange rate
• 3 m³/hr/m² minimum for health

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Infiltration (air leakage) (cont.)
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Energy Ratings

• Standard Assessment Procedure (SAP) gives a
  rating from 0-100 for heating cost effectiveness.
• Heating and hot water energy use only
• SAP 100 no bills
• SAP 0 very, very expensive
• Not a true measure of energy performance, as
  cheaper fuels will get better ratings
• SAP rating part of the new Energy Performance
  Certificates
• New SAP system will give ratings higher than 100
  for dwellings that export energy

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Energy Ratings (cont.)
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Energy Ratings (cont.)

• Energy Performance Certificates must be issued
  for all dwellings bought and sold in England and
  Wales from June 2007
• SAP rating and Environmental (CO2) rating on A-G
  scale
• Possible energy efficiency measures and potential
  of dwelling described

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Achieving Super Insulation

• Much easier to achieve in a new house than
  existing
• As much insulation as possible very thick walls
• U-values walls 0.15 0.10 W/m²K
• Triple glazing
• Extremely air-tight. Mechanical heat recovery
  ventilation
• Back up heating (just in case!)

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Further Reading

• Energy Saving Trust - Best Practice in Housing
  Free publications
• For existing housing recommended reading
  Domestic Energy Efficiency Primer CE101/GPG171

• www.est.org.uk/housingbuildings/publications
• 0845 120 7799