Air tightness


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Air tightness

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