UK's first oak-framed Passive House completed

The UK’s first Passive House oak framed house has passed its initial air pressure tests.

Award winning oak framed house builders Oakwrights of Hereford last week carried out successful preliminary air pressure tests on the house, which is being constructed for self-builder Dr Phil Garnett in Yorkshire.

Passive House (also known as Passivhaus) is the fastest growing energy performance standard in the world.  Over the course of a year a Passive House typically uses up to 90% less heating and cooling energy compared to consumption in typical homes.

Oakwrights Certified Passive House Consultant David Bryan said: 'We are often asked about eco-friendly new build designs which meet the planning requirements for energy efficiency and constructing to the Passive House standard can be the ideal solution.

'The key to the success of this type of building is having structural oak frame internally with an airtight, insulated envelope surrounding this, to avoid all penetration of this skin to reduce thermal bridging and possible issues with airtightness as the oak dries out.'

The Oakwrights team found that the preliminary air pressure test results were 0.4ach @ 50Pa which is 25% better than that required for Passive House requirements and also below the design limits of the property which will mean that potentially even less energy will be required than the original calculations in PHPP (the Passive House Planning Package) suggested.

Passivhaus Design principals require a building to have a minimum airtightness standard of 0.6ach @ 50Pa (air changes per hour at 50 pascals); that means that a maximum of 60% of the entire volume of air in the building can be replaced by means of leakage around windows etc in one hour when the air pressure difference between inside and out is 50Pa. It is difficult to directly compare this to current Building Regulation standards as the units of measurement are different, however, this equates to slightly less than one tenth of the current requirement for new UK dwellings.

As these tests were carried out without the final internal finishing in place, it is usual that this result will improve once the building is complete so the company is looking forward to the final approval blower door test to see how much better it can get.