Sarah Lonsdale: A more eco-friendly way of life With two housing projects on this year's Stirling Prize shortlist, the debate over what modern homes, particularly modern eco homes, should look like has reignited. One shortlisted project is a development of geometric, black timber new homes in Harlow, Essex, by award-winning architect Alison Brooks. Built with high levels of insulation, the houses have achieved Code for Sustainable Homes Level Three, meaning they are 25 per cent more energy efficient than homes built to 2006 Building Regulations. Although partly inspired by traditional Essex barns, the homes are unmistakably 21st century in design, with first-floor courtyards and angular roof lines creating a bold effect. Farther west, just outside Watford, a smart young couple have been living in a handsome Regency-style house for a year. The front garden is thrumming with bees visiting the alliums and the eaves provide welcome shade in the stifling July heat. Cosmin Ticleanu and Elena Coltea are "volunteer occupants" and have been test-driving this house, an eco home every bit as modern as - and even more energy efficient than - the clean-lined Harlow homes. While eco, the "Princes House," one of several new homes being tested here at the Buildings Research Establishment (bre.co.uk), embraces the past, from its hexagonal Egyptian-inspired balcony columns and oak parquet floor. From this year all new homes must attain increasingly stringent energy efficiency requirements, and Cosmin and Elena's experience in the Princes House will influence the direction of modern environmental architecture. At the heart of their year of living experimentally is the eternal question: what type of new houses do people want to live in? Post-modern, angular, flashing their eco-bling with plant rooms and roofs shiny with solar panels, but which require an engineer if anything goes wrong? Or cosily traditional, borrowing features from the past, but open to accusations of being ersatz, backward-looking and unimaginative? The Princes House was designed and built after Prince Charles, known for his green credentials and love of traditional architectural styles, expressed dissatisfaction with modern eco home design. Can you not have an energy efficient home that also offers what survey after survey suggests that people want: traditional architecture? he asked. When completed, the house, a prototype for developers to use, looked handsome: but what would it be like to live in? Cosmin and Elena have no doubts. Their year in the Princes House was informed by their previous stay in a hi-tech "House of the Future" built in 1998 with solar thermal and pv panels, geothermal heating, electronic locking and other whizzy gismos. Which did they prefer? "The traditional house definitely," says Elena, a psychotherapist. It feels like a proper home. When you come in, it wraps itself around you. Ultra modern homes often look and feel like offices. After spending all day in an office, I don't want to come home to one. Of course aesthetics are personal and for every Elena and Cosmin who want a cosy, traditional home, there is a couple that prefers bright, angular and contemporary spaces with plenty of technology. The point the Princes House is trying to make is that even if you want high levels of efficiency, there are alternative designs. "The Princes House is made with natural materials," says Ben Bolgar, architect and senior director of the Princes Foundation (princes-foundation.org). "The wall construction is breathable aerated clay 'Ziegel" blocks and lime render; the insulation is wood fibre and sheep's wool. The house is deliberately low tech, making use of features like deep eaves for shade and a wood-burning stove. I wanted to keep it simple. I thought about my children and how they would cope, when adults, if there was an energy crisis. I would prefer it if they lived in a solid, simple well-built home that they could heat with wood if the gas ran out, not heat pumps that need electricity. I also wanted a house that doesn't require an expert when something goes wrong. He asks why it is that so many people would rather live in a draughty period home than an efficient modern one, when fuel bills are so high. It's not because they like draughts or paying high gas bills, but because traditional homes create a sense of belonging.