Preston Springs Passivhaus

Preston Springs certified Passivhaus
Green Building Store are our trusted partners for windows and MVHR systems. When we’re working on a project they are the first people we contact, due to the combination of good quality products, knowledgeable technical support and great service.

Mark Siddall – Architect

The Preston Springs Passivhaus is 4 bed Passivhaus home designed by Architect and Passivhaus Designer Mark Siddall from LEAP architecture. The project is an evolution from Mark’s previous award winning Passivhaus at Steel Farm, also built using cavity wall construction. He helped keep costs down by a refining the design and construction process. This meant evolving ever more simple and easy to build construction details. Mark worked with the same building team (JD Joinery and Building) as he’d worked with on Steel Farm. This ensured excellent quality assurance and a great team working relationship.

The clients Richard and Helen were looking for a comfortable family home and aspired to a Passivhaus but were concerned that it could break their budget. In the end, the house was built for less than the contract value and the project achieved Passivhaus certification in December 2017. The completion airtightness test on the project came in at 0.31 ach/ hour @ 50 Pa.

The project was built in cavity wall construction with a truss rafter roof all sitting on a raft foundation. Green Building Store supplied the PERFORMANCE triple glazed timber windows and doors and the MVHR system for the project.

Feedback from clients during the ‘Beast from the East’

Richard: “The house is facing down the ‘Beast from the East’ and succeeding. The radiators have barely been on for last few days. The Passivhaus is doing well!”

Helen: “The house was up to 19.8 degrees C inside yesterday without the heating on, as far as we could tell. It was very sunny in the afternoon, but when I ventured out the car said it was -6c outside, so pretty impressive, I think!”

Triple glazed timber windows and doors

Unusually, Green Building Store’s PERFORMANCE timber windows and doors were chosen for the Passivhaus project. Although not Passivhaus certified, the windows offer a whole window U value of 0.85 W/m2K and in this instance were deemed acceptable by the Passivhaus Certifier. NOTE: Do not assume this will work with your project, speak to your certifier before going down this route.

Mark Siddall explained: “The choice of the PERFORMANCE range was driven initially by cost when we weren’t 100% sure if the project was going for Passivhaus certification. The use of the PERFORMANCE range did lead to some distinct challenges for certification, including the preparation of a detailed report analysing the condensation risks for the specific climate where the project is based. Also to help with the assessment of condensation risk thermal bridging calculations were undertaken for every opening. This was all very time consuming. Next time, to avoid similar headaches during Passivhaus certification, I would simply just choose windows from Green Building Store’s high performance ULTRA range .”

As part of a way of keeping costs down, Mark was careful to design uncomplicated window openings, with fixed windows where possible. The windows were larger on the south elevation, with the size optimised for daylighting and wellbeing.

Mark Siddall added: “Green Building Store are our trusted partners for windows and MVHR systems. When we’re working on a project they are the first people we contact, due to the combination of good quality products, knowledgeable technical support and great service.”

MVHR heat recovery ventilation

Alan Clarke designed the services on the project, including the PAUL Novus 300 MVHR system, which Green Building Store’s MVHR Design Service set out in CAD. An interesting development on the MVHR design on the project was the use of attenuators on the system’s exhaust, to reduce any noise from the MVHR system going to the outside and disturbing neighbours. Green Building Store also commissioned the MVHR unit.

Pro Clima airtightness tapes

Green Building Store also supplied various Pro Clima airtightness tapes and membranes for the project. The were used around windows, and at roof level to form both the air barrier and the wind barrier.

Cold roof research

The cold roof construction will be subject to detailed monitoring program over a 12 month period to help develop an understanding of how these spaces work with low U-values, excellent airtightness and breathable roof membranes.

In preparation for the research the loft was subjected to what could be the UK’s first pressure test. It achieved an air leakage rate of 7 air changes per hour at 50 pascals.


More information

Architect: Mark Siddall, LEAP Architecture

Building Contractor: JD Joinery and Building

Mechanical services: Alan Clarke Tel: 01594 563356

To watch the Passivhaus Secrets documentary on Steel Farm Passivhaus go to:



7th March 2018

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