Why should I choose a fabric first approach to house redesign?

If you want an eco home, a fabric first build method is highly effective, but strict design principles must be observed for best results, says Laure Ghouila Houri

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Mole Architects remodelled this 1960s bungalow, wrapping it in insulation and cladding to boost its eco credentials as well as its design appeal

What is a fabric first approach?

This building method is about constructing spaces that require very little energy to heat and cool them. The principles go back to basics: thinking about the structure of a property and the materials used to build it before anything else.

The zenith of this approach is Passivhaus, a stringent set of standards devised in Germany in the late 1980s, which requires meeting certain energy-efficiency performance levels and gaining accreditation. Fabric first prioritises passive design principles over technology. For example, reducing energy consumption by increasing insulation, and utilising heat from the sun through high-performance glazing will be considered before deciding to use solar panels or wind energy.

When redesigning your home, think about increasing the size or number of south-facing windows and reducing north-side fittings, ensuring you clear any alterations with your local planning department. Keep heat in with super-insulated walls and a roof well.

How to make a fabric first approach work on existing homes

It is possible to apply fabric first principles when renovating or extending your home, but, generally speaking, it’s easier if your house is detached. You can ‘overclad’ a stand-alone property and ‘wrap’ it in insulation inside and out, but that wouldn’t work aesthetically in a row of terraces.

For semi-detached or terraced houses, it’s a good idea to change the orientation of rooms, so that the kitchen-diner or living room benefit from most natural heat and light, while the less frequently used spare bedroom, utility and cloakrooms can be sited in north facing areas.

Even small changes can make a huge difference to a home’s energy efficiency. Think about boosting light in dark areas with sunpipes or rooflights, and replace single or double-glazed windows and doors with triple-glazed styles.

How to reap the benefits of the fabric first approach

Boost insulation in walls, floors and the roof, eliminate draughts, make better use of glazing and replace inefficient designs with new high-performance fittings and your home will definitely be more comfortable. A low-energy house doesn’t have hot and cold areas closer or further away from a heat source; everywhere is a good temperature. Best of all, energy bills will be reduced.

Think carefully about windows

To insulate and add high-performance glazing can come at a cost. Placing the largest windows to the south may seem odd if the best view is north, but often a smaller window to frame a view will capture scenery and help retain heat, saving on bills.

Don’t forget materials

Specialists in the fabric first approach, such as Meredith Bowles at Mole Architects, tend to promote building a timber-frame structure with a masonry core inside, and lots of insulation. It’s actually a law of diminishing returns; once you’ve put in about 30cm (or 20cm of high-grade insulation) the amount of improvement becomes far less per extra millimetre of insulation.

At this point it’s better to look at other aspects such as the window performance, doors and eliminating any possible draughts. Frames and windows must be made from high-quality materials with excellent overall performance, with a U-value of 0.8 W/m²K or less. Always ask the manufacturer for the U-value of the whole window and remember aesthetics don’t have to be compromised.

What is a U-value?

Measures how effective a material is as an insulator. The lower the U-value, the better the product or material’s thermal performance.

Laure Ghouila Houri of Architexture