Case Study – New Build PassivHaus 2017-07-07T13:11:20+00:00

New Passivhaus @ Howe Park Wood, Milton Keynes

This home of the future has been designed to provide a highly sustainable five bed executive rental house to provide income for Milton Keynes Parks trust. Eco Design consultants had a challenging brief to develop a home next to a site of special scientific interest that met exacting environmental standards and generated a good financial return on initial investment. Following preliminary discussions the aim of the building Milton Keynes first Passivhaus was set, with additional targets of high levels of water conservation, use of low impact materials and using the project as an education tool.

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 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.

The land was given to the Milton Keynes Parks Trust from the Homes and Communities Agency in autumn 2010 on a 100 year lease which meant that the Trust could not sell the derelict burnt out building on the site. They instead chose to demolish the existing uninhabitable house and replace it with a new eco-friendly property that would do justice to the location and aspirations of the Parks Trust, while generating income to support the work of the trust an independent charity who care for the parks and green spaces of Milton Keynes.

One of the main advantages of Passivhaus design is comfort. 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.

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 winter. To reduce the visual height at the rear of the building, tile hanging was used on the top floor. In order to maintain the open ground floor three storey house work, an egress window was installed on the top landing. The design of the house is specifically aimed at the rental market.

5 bed rental house in Milton Keynes
Treated Floor Area 182 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
Construction costs 2000 £/m²

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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.

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 within the house, down to 0.07 air changes per hour at 50 Pascal’s. This was accomplished through quality control, excellent workmanship and a high level of detail. This high level of air tightness has greatly reduced the heat losses, a 19% improvement from the minimum Passivhaus requirement of 0.6.

Building materials were selected by their environmental credentials for the longevity, low toxicity, low embodied carbon, reusability and recycled content. Natural materials were used where possible. A very visible example of this is the Kebony cladding, a soft wood treated with 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 and risk of condensation, normally associated with clothes drying internally. The location also keeps dirty laundry out of the kitchen, and closer to its point of use.

One particular innovative approach we took in the construction was to eliminate the sole plate at the base of the timber frame walls, to reduce the cold bridge at this location also reducing possible settlement issues.  We are not aware that sole plates have been eliminated previously. However we felt that this new approach was the only way of achieving cost effective elimination of cold bridging. Following their initial scepticisms the timber frame providers became enthusiastic about this new method and now routinely applying the details in other projects.

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. 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.

Renovation and Home Design
Reading in the winter sun