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Building Airtightness - it’s time to play catch up!


BKE 3


BUILD ING KNOWLEDGE EX C HANG E


Our awareness of the fragility of our planet’s eco system and the influence mankind has upon it is rapidly growing. There is no doubt that the subject is creating more concern than ever and is now termed by many authorities across the UK as a ‘Climate Emergency’. Unusual weather patterns and a noticeable change in climate have been observed by us all and this is the most visible impact of global warming today. The Intergovernmental Panel on Climate Change has been established to do the research and offer preventative actions, but as individuals we can help the construction industry reduce the impact.


Every year, over 21 billion tons of carbon dioxide are produced through our activities and the burning of fossil fuels for heating our buildings are a major contribution. It is estimated that around 32% of total UK greenhouse gases are produced in this way.


Energy conservation is a logical approach and making improvements in airtightness to reduce convective heat loss is a key component. If the building envelope can be properly sealed, unintentional air movement through cracks, joints and other sources of air leakage can be avoided. Improving our methods in both design and build and adopting a ‘Fabric First’ approach will help us achieve these goals. Lower CO2 emissions, lower fuel bills and a carbon neutral society.


The UK is seriously lagging behind other European countries


Materials There are often various materials, layers or components within the building element that can be used to enhance the building airtightness. During the design stage it is prudent to establish which components are to be used to form the ‘airtightness line’. Commonly, in timber and steel frame construction an external breather membrane can be used. If however, we are to address air- leakage seriously, we should be looking to use an internal AVCL with superior airtightness characteristics, such as DuPont™ AirGuard® Reflective.


As it currently stands in the UK, it is quite common for our buildings to be achieving air leakage levels of between 3 and 5m3 clearly better than the 10m3


/hr/m2 . @50Pa, which is stipulated by Building Regulations. Even so, the UK


is seriously lagging behind other European countries whose upper limits are very often well below 1m3


DuPont™ Tyvek® manufacture a range of membranes, tapes & sealants, which can help us to achieve the airtightness levels the UK so desperately needs. For more information please contact our Building Knowledge Centre.


(Our thanks to Nick Williams, DuPont, for this BKE article) DUPONT TEL: 08444 068722 13 WWW.CONSTRUCTION.TYVEK.CO.UK


Indoor Air Quality Living in a location where fresh air is in constant supply is ideal, but many of us live or work in urban environments where the outside air may be polluted by exhaust fumes or industry. Those with heavy road traffic are most at risk, with high recorded levels of nitrogen dioxide (NO2), a pollutant gas which can create breathing problems. Research from a Friends of the Earth study (February 2019) confirms that there are thousands of towns and cities that exceed safety limits. Cutting down on the rate at which air flows in and out of our buildings is a logical way to establish control of our indoor environments... ...and help keep the noise down too!


Ventilation


It’s important to remember that very good airtightness introduces a need for internal air replenishment. A healthy indoor atmosphere can only be maintained if stagnant air, bacteria, VOC’s, moisture and unwanted odours are filtered out. When airtightness levels of 5m3


extraction should be considered, whereas at 3m3


/hr or better are achieved, mechanical /hr a heat recovery system


will be needed. This tends to create some concern over installation and running costs. But it’s not all bad news, the long-term energy efficiency benefits can be significant, with projected savings in heating costs of up to 20%, when air- leakage rates approach Passive House Levels.


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