Air tightness
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Air tightness

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DT117/4 Sustainable Build & Design - Class Presentations

DT117/4 Sustainable Build & Design - Class Presentations

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  • 1. Air tightness Cathal Mac Séalaigh
  • 2. Areas to be looked at
    • What is air tightness?
    • Building Regulations
    • Common air leakage paths
    • Impact on BER
    • Why is it important?
  • 3. What is air tightness?
    • Unintentional movement of air through a building
    • Also know as air permeability
    • Draughts- cold air penetrating the external envelope into the building
    • Heated air escaping through the external envelope to the outside
  • 4. Air tightness
  • 5. Building Regulations
    • Technical Guidance Document
    • Part L 2008
    • Conservation of fuel and energy- Dwellings
    • Ammendments to Part L requiring new dwellings to be subjected to Air Permeability Pressure Testing
    • Ensuring new housing stock is built to highest international standards
    • A step towards lowering carbon emmisions
    • Improvement in energy efficiency
  • 6. Building Regulations
    • Regulation L2 (c) requires heat losses from a dwelling should be limited
    • Heat gains through the fabric of the building should be availed of where appropriate
    • Limit air permeability through building elements adjoining heated and unheated spaces
  • 7. Building Regulations
    • Clause 1.3.4.4 of TGD L 2008 requires air permeability testing be carried out on a proportion of dwellings on all development sites
    • From 1 st July 2008
  • 8. Number of Tests At least 2% of units At least 5% of units, until 5 successful consecutive tests are achieved, 2% thereafter
    • More than 100
    • where the first 5 tests achieved the design air permeability
    • where one or more of the first five test do not achiveve the design air permeability
    At least 5% of the dwelling type >40 but ≤100 2 tests >4 but ≤40 1 test 4 or less Number of Tests Number of Units
  • 9. How is it measured?
    • ‘ The airtightness of a dwelling, or its air permeability, is expressed in terms of air leakage in cubic metes per hour per square metre of the dwelling envelope area when the building is subjected to a differential pressure of 50 Pascals (m3/(h.m2)@50Pa)’.
    • Limiting Thermal Bridging and Air Infiltration Acceptable Construction Details
  • 10. Air permeability testing
  • 11. How is it measured
    • Blower door test
    • Variable speed fan inserted into a sealed aperture (usually in front door)
    • Intended ventilation opening are closed
    • Extractor fans and chimneys are sealed
    • Fan creates a pressure difference inside the building different to that outside forcing air out.
  • 12. How is it measured?
    • The air flow through the fan is measured and calculated to give an air flow rate in m3/(h.m2) of building envelope at 50 Pa
    • The quantity of air added to or drawn from building to maintain pressure levels will approximately equal air escaping through unintentional air paths
    • Test result of 10 m3/(h.m2) resonable upper limit
  • 13. Air Permeability Testing
  • 14. Air Permeability Testing
  • 15. Common air leakage paths
    • To achieve an airtight dwelling a continous uninterupted air barrier must be formed between the inside and outside
    • Air barrier will be in the form of external walls, party walls, ceilings and floors.
  • 16. Common air leakage paths
    • Poorly fitted windows and external doors
    • Through trickle vents that leak when closed
    • Gaps around attic doors
    • Waste/service pipes throught external walls
    • Fiiting and services through ceilings
    • Chimneys without dampers
    • Gaps/ tears in vapour barriers
    • Gaps in masonry mortar joints
    • Gaps in Plasterwork
    • Joists/slabs built into external walls
    • Poorly fitted vents
    • Underfloor ventilation grilles
    • Gaps at floor/external wall junction and wall/roof junction
  • 17. Why is it important?
    • By limiting air leakage from a dwelling it is possible to reduce energy consumption
    • Extra energy generated to replace heated air that is lost through air leakage
    • The warmer the air the greater its ability to carry moisture, can lead to cooling in voids leading to condensation, mould growth etc.
    • Cold air infiltration can lead to localised draughts, causing occupant discomfort
  • 18. Impact on the BER
    • The better the air permeability levels the better the possible BER of a dweling
    • Levels better that the upper limit of 10m3/(h.m2) needed to satisfy the building regulations will lead to an improved BER
    • Better airtightness leads to less energy consumption and a better BER
  • 19.
    • Questions