One of many on-going construction projects that Hilsdon Holmes are currently involved with, is a multi-residential Passivhaus development in Plymouth. To date this project is the second largest multi-residential Passivhaus development in the UK.


While the general principles of a passively heated or cooled house are not new, a scientific approach to passive design has gathered momentum in recent decades, with an industry recognised standard, developed from research carried out by Dr Wolfgang Feist, introduced in the 1980’s. The key principles of Passivhaus design are:

  • Good levels of insulation with minimal thermal bridging
  • Excellent levels of airtightness
  • Good indoor air quality
  • Passive heat gains through solar radiation and internal heat sources

The reason that a Passivhaus is required to be of a highly airtight construction is because the level of airtightness for a building will directly affect the heating demand. As a result, the financial and environmental costs of maintaining a good level of thermal comfort in less airtight properties is greater.

For the majority of newbuild properties, it is only necessary to test the airtightness as part of the completion assessment. For a building to comply with the Passivhaus standard, air permeability should be no more than 0.6 volumetric air changes per hour. To ensure the finished properties would comply with such a high degree of airtightness, Hilsdon Holmes have been conducting air tightness tests at both first fix stage (when the main building services are installed prior to dry lining), and for the standard final test for compliance with Passivhaus standard and building regulations.

Our testers have an excellent understanding of airtightness construction, so we can offer comprehensive advice on potential problem areas, and practical guidance when locating leakage during first fix tests. This cooperative approach to first fix testing has resulted in plots achieving very low results with many attaining less than 0.55 air changes per hour.

Ensuring a completely airtight seal around the testing frame is critical when it is placed into the properties external door opening. Due to the extremely airtight standard of a Passivhaus, our testers have developed methods to ensure a completely airtight seal around both the blower door frame and the fan drum.

Looking to the future, our current governing body ATTMA is in the process of launching a dedicated Passivhaus testing standard, which we will be affiliated with once it is up and running.

If you would like to discuss this further with us please call today on 01579 382202 or by email:

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