Case Study- Passivhaus Classic 2018-06-05T14:08:54+00:00

Passivhaus Classic @ Howe Park Wood, Milton Keynes

The Parks Trust set a challenging brief to develop a home on a derelict, vandalised site. The site is next to a site of special scientific interest that resulted in exacting environmental standards. As a charity the client needed the home to generate a good financial return on initial investment, without compromising it’s environmental principles. Following preliminary discussions the goal of building Milton Keynes first Passivhaus was set, along side additional targets for high levels of water conservation, use of low impact materials and using the project as an education tool. The result is an award winning highly sustainable five-bed executive rental home, which has provided a consistent income since 2012.

The high quality design and attention to detail throughout the project resulted in the Howe Park House achieving full Passivhaus certification. This accreditation reliably demonstrates the project’s environmental achievements in terms of thermal performance and build quality.

A Passivhaus is a much healthier home thanks to the MHVR system which draws fresh air into the house without the risk of draughts and controls the level of humidity. This in turn reduces the risk of condensation and mould growth. The filters within the system remove pollutants and odours from the air which leaves occupants happier and healthier. Additionally residents benefit from a greatly reduced heating bill.

The design of the house is compact, with an open plan ground floor, with large south facing windows, and a further two floors of bedrooms and bathrooms. The main roof slopes to the south allowing the installation of photovoltaic panels, and providing a 2 storey appearance to the front. This also created a link between the adjacent housing estate and the site of special scientific interest. A large overhang provides shade in the summer, preventing overheating, while allowing the lower winter sun in heating the house in the colder months.

The most airtight building in the UK

Overall the greatest triumph on this project we feel is the achievement of such a high level of airtightness. With air changes down to 0.07 per hour at 50 pascals. This was accomplished through quality control, excellent workmanship and a high level of detail. The level of airtightness has greatly reduced the heat losses, a 19% improvement on Passivhaus minimum requirements.

Airtightness plus the MVHR help to deliver the comfort experienced in Passivhaus buildings. Fresh air is efficiently delivered throughtout the home and there is no sitting in drafts. Comfort is the main advantage of Passivhaus design. By designing a home according to this standard we created a place where occupants are comfortable all year round without the use of traditional space heating systems.

Building materials were selected by their environmental credentials for their longevity, low toxicity, low embodied carbon, re-usability and recycled content. Natural materials were used where possible. A very visible example of this is the Kebony cladding, a soft wood treated via a natural process to achieve the longevity of hardwood.

The design includes a laundry room on the first floor, which incorporates an MVHR extract allowing clothes to be dried internally without additional energy usage or a risk of condensation. The location also keeps dirty laundry out of the kitchen and closer to its point of use.

One particular innovative approach we took during construction was to eliminate the sole plate at the base of the timber frame walls. This reduced the cold bridge at the junction with the floor and reduced possible settlement issues. We felt this new approach was a cost effective way of cold bridge elimination.

Another key element of the scheme is the approach taken to landscaping: Howe Park wood is a designated Site of Special Scientific interest, valued by English nature for its wildlife, therefore it was imperative to protect the sites inhabitants.

Reading in the winter sun

Instead of the usual approach of installing newt fencing and removing all newts from the construction site, we took the innovative solution of adjusting the kerbs and gully pots allowing the newts to cross the road and escape, rather than cross the road and the walk along the gutter and fall into the gullies where they are unable to get out. These changes will continue to benefit wildlife beyond build completion. In addition the orchard and pond which had been neglected over the course of time has been revitalised, the paddock has been reseeded and bat boxes have been installed around the site to encourage native species to thrive. These innovative solutions resulted in the project being awarded a green apple award.

Completed in July 2012 the property was let rapidly and enjoyed constant occupation thus fulfilling financial investment requirements. Just prior to the tenants moving in Milton Keynes Parks Trust held Milton Keynes’ first green fair at the house. This event exposed a variety of individuals to environmental messages welcoming the local community to view the building and hear lectures explaining principles and concepts behind the design. There are now a number of Passivhaus projects being planning in and around Milton Keynes. Oxford Brookes University are monitoring the house to produce a post occupancy report.

5 bed rental house in Milton Keynes
Treated Floor Area182 m²
Energy Standard [PHPP]
Space Heat Demand11 kWh/m²a
Heat load (Thames valley data)9 W/m²
Air-tightness (n50-value)0.065 h-1 @ 50 Pa
Construction typeTimber frame
Building Envelope 
U- values
Floor slab0.12 W/m2K
Exterior walls0.14W/m2K
Roof0.12 W/m2K
Windows glass0.6 & 0.7 W/m²K
Windows frame

MVHR

Space heating & hot water system

0.97 W/m²K

Zehnder ComfoAir 550

30 tube  Baxi solar collector, 210 litres cylinder, 2kW Dimplex Girona Panel heater. And electric towel rails.

Renovation and Home Design