The Black House, Prickwillow, Cambridgeshire

Introduction

In 2003 Meredith Bowles completed a timber frame home for his family and an office for his architect’s practice in the Fens village of Prickwillow near Ely in Cambridgeshire.The windows on the west side provide a view to Ely Cathedral and the black painted fibre cement corrugated cladding lends the building a barn-like quality.

Project Description

The house is tall and narrow, with windows lining up at front and back to give rooms light from both sides and a sense of the house being see-through. At the heart of the house on the ground floor is the kitchen/dining room; circulation on the ground floor takes place through this room. Vertically, a glazed stairway allows views through all three storeys. The same stairway acts as a chimney to draw air through the building and out of the roof window.

Detail Description

The timber frame building is raised above the ground on brick stilts, improving the view, reducing the risk of the property flooding and simplifying the construction. The house is heated by an air to air heat pump and protected from overheating by simple external shades. Excessive heat loss during ventilation is prevented by the use of a cross current heat exchanger.

Structure

The timber structure is raised off the ground on brick clad concrete piers; the piers are extensions of the steel piles below. The lightweight structure reduces the number of piles in the foundations. The horizontal restraint of the piles is carried in the glulam beams that sit on the piers and are bolted down to the pile caps with high tensile steel rods. This dispenses with the need for cast concrete beams in the ground. The glulam sections are either half-lapped or third-lapped at each junction, with the bolt passing through each member. The end grain is protected with galvanised plates. The main structure is constructed with prefabricated timber panels, using 220mm deep timber I-beams. The 250mm roof panels span onto a glulam ridge beam supported on internal spine walls to create the attic bedroom floor.

Architect’s Comment

When Meredith moved northeast to the Fens from London three years ago, his aim was to build an environmentally-friendly family house that would fit in with the flat and solitary landscape of east Cambridgeshire. He also wanted to have a go at a barn conversion free of the cliche-ridden associations with hanging baskets, crazy paving, exposed beams and hexagonal French tiles on the kitchen floor so prevalent in the home counties.

A few years on Meredith says the house works well as a home. Technically, the timber frame has performed well; it deflects a bit, but that’s what you’d expect from a ten metre tall building in the middle of the fens. Active use of the shading and passive ventilation are vital to maintaining comfortable internal temperatures and the intended stack ventilation works well. He has had most problems with the heat system which he says “is too complex for its own good”.

Client’s Comment

Meredith’s wife Jill says ‘I’d been led to believe it (the building process) would be a nightmare, but it was actually very exciting, watching it all going up. I was preparing myself to live in a building site but when we moved in, it felt finished.’ There were also none of the usual coupley rows about the colour of the kitchen walls and stairway carpet. Meredith tried to engage his wife in decor decisions, but to no avail. It was an apathy he now appreciates as ‘very generous’. ‘Jill knew it was of huge value to me - my primary goal as an architect is to produce something of beauty for myself - so she gave me free rein.’ ‘I was the ideal client really,’ says Jill. ‘I trusted him, I had confidence in his taste. I’ve never really taken a big interest in my home environment. But I’ve so enjoyed living in this house that I do now understand why people care about these things, to the extent of wanting to build their own homes’.

For the time being at least, Jill is happy right where she is. “When you’ve had a home that was effectively built for you, you’re very lucky,” she says. “That’s why I don’t think I’ll ever want to move.”

Architect’s Assessment

When Meredith moved northeast to the Fens from London three years ago, his aim was to build an environmentally-friendly family house that would fit in with the flat and solitary landscape of east Cambridgeshire. He also wanted to have a go at a barn conversion free of the cliche-ridden associations with hanging baskets. crazy paving, exposed beams and hexagonal French tiles on the kitchen floor so prevalent in the home counties.

Sustainability

The house is designed to offer a model for inexpensive prefabricated dwellings constructed using some basic sustainability principles:

1. The primary contribution to sustainability comes from the highly insulated building envelope. The walls are constructed from 220 mm deep timber I-beams fully filled with recycled newspaper insulation. Those in the roof are 250mm deep. The U-values of the walls are below 0.16 W/m2k and the roof is 0.14 W/m2k. Windows are high performance with an internal low-e coating and argon filled cavities.

2. The panels are constructed on the ‘breathing wall’ principle, with ‘Paneline’ on the internal face and ‘Panelvent’ on the external face, allowing the omission of a separate vapour control layer.

3. The use of materials eg. metal and concrete with high levels of embodied energy has been restricted. The decision to use softwood timber as the primary structure was largely a result of this choice.

4. The use of a heating system that offers an alternative to fossil fuels. A Danish made air to air heat pump unit provides air heated to 38 degrees. In the future there is the intention to generate energy from pv cells once these become more affordable.

This is complemented by the use of low wattage bulbs, low energy floodlights and fluorescent tubes as a hidden light source.

5. Re-cycled materials are in strong evidence; the floor panels are made from timber waste, the insulation is produced from recycled newspaper and the floor is covered with reclaimed wood blocks. The acoustic underlay is manufactured from recycled rubber, the plinths are from reclaimed bricks, and splash backs made from re-cycled industrial chopping boards. 6. External sunscreens above the large ground floor windows cut out overhead mid afternoon sun in the summer. The first floor windows have a reflective coating on the outside of the glass, and the roof lights are fitted with external sunscreens as well as internal blinds.