Thermal bypass risks – a PassivHaus report by Mark Siddall

Known as thermal bypass, air movement across, within and behind insulation increases heat loss, causes discomfort and enables mould growth. With the correct knowledge and skills, both in practice and onsite, failures in design and construction can be avoided and deliver buildings that perform as predicted.

Whether it’s a newbuild, a conversion or a renovation, this guide draws upon a sound evidence base which reveals simple practical steps policymakers, developers, certifiers, designers and constructors can take to create successful high-quality, high-performance and robust buildings at speed and scale to meet climate targets.

Read this paper to gain new insights, build confidence and discover how you can make informed, intelligent decisions that will:

  • improve the health, well-being and energy security of building occupants and owners
  • reduce carbon emissions and fuel poverty
  • close performance gaps
  • avoid costly mistakes
  • protect the building fabric from moisture damage

 

Types of thermal bypass (a) closed loop (b) open loop: wind washing (c)open loop: air leakage (infiltration or exfiltration) (d) reality

 

By contextualising an understanding of thermal bypass, this paper provides a comprehensive and technical demonstration of how Passivhaus reliably closes the performance gap. If thermal performance gaps are to remain within an acceptable tolerance, then continuous insulation should be encapsulated on all sides by uninterrupted, unbroken air and wind barriers.

The paper emphasises the invaluable opportunity of implementing Passivhaus at scale to provide a robust solution that delivers high performance construction, energy savings, carbon emissions, comfort, health and well-being that owners, investors, occupants can rely on both now and in future.

This paper has been authored by AECB expert advisor Mark Siddall, of LEAP.

Download the report here