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An innovative approach to airtightness testing - the PULSE method explained

Posted by Sam Tonge on 1 October 2018 at 9:36 am

Air leakage is widely accepted as a major cause of thermal inefficiency within many of our homes in the UK, accounting for 30% of total heat loss on average. The uncontrolled flow of air through small gaps in our properties can rack up our utility bills as well as being very uncomfortable for us as occupants of these draughty houses! Higher CO₂ emissions also result from this lack of airtightness, as any heat produced will quickly escape to the outside.

Cold air can find its way into the home through gaps in the walls, floors and ceilings, resulting in cold draughts. Conversely, leaking of warm air produced inside the house through these gaps is known as exfiltration, which leads to a lot of wasted energy. Too much or too little background ventilation can also be the cause of mould, condensation and issues with indoor air quality and health problems.

Controlling airflow through your home is best achieved through a carefully-designed controllable ventilation system. This may include localised extractor fans to remove excess moisture in wet rooms, e.g. bathrooms and kitchens, alongside well-placed trickle vents in other areas of the home. In cases where dwellings are very airtight, a whole house mechanical ventilation system is recommended to ensure higher air change rates and improved air quality.

With air leakage providing such a big opportunity for energy-saving improvements in our homes, the need to measure airtightness levels is paramount. A traditional airtightness test (known as the blower door fan method) would be carried out as follows:

  • A temporary airtight screen is fitted into the entrance door of your home.
  • Water traps should be filled or temporarily blocked, trickle vents closed and extract vents sealed.
  • A fan is then mounted in this screen and air is blown in or out of your home resulting in a pressure difference
  • The airtightness (or air permeability) of your home is quantified by measuring the rate of airflow through the fan while these pressure differences between inside and outside are maintained.

However a pioneering approach known as PULSE has recently opened up an innovative and effective way of testing airtightness without the disruption caused by a fan. The PULSE technique works as follows:

  • A short burst of air is introduced by releasing compressed air into your property from a tank, which creates a pulse in the internal pressure.
  • During this pulse, a period of quasi-steady flow is established that directly gives the leakage characteristic at the specified level of pressure
  • After adjustment to still air conditions and a small correction for the effective flow rate arising from the compressibility of air, the result can be plotted or read in the same way as the blower door fan technique.

Crucially, the PULSE test is provides an accurate measurement of air permeability within a property at low pressure, thus representing the behaviours of leakage paths and background ventilation under ordinary conditions. The whole test process takes under 15 minutes from start to finish and is also less invasive than having a high pressure fan mounted in your doorway.

The PULSE test is being marketed by a company called Build Test Solutions and it is well worth keeping an eye out for this innovative and exciting new approach. Looking to the future this pioneering technique could offer you an invaluable opportunity to better understand the level of air leakage within your home, which in turn could help inform which actions to take to improve your sense of comfort and wellbeing as well as reducing  utility bills and CO ₂ emissions within your property.


More information about ventilation and draughts on YouGen.

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About the author:

Sam has contributed to our blog since 2016 and previously worked for the National Energy Foundation.

He became interested in green energy after completing a degree in Geography (BSc) at Royal Holloway, University of London. 

Sam is passionate about renewable energy and is committed to spreading the word about the role it plays in delivering environmental sustainability. 

If you have a question about anything in the above blog, please ask it in the comments section below.

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