Beware the snake-oil sellers. This is the advice traditionally handed down to any novice seeking to build their own eco-home. But compared with even the boldest of boasts offered by some within the green-build world, Tomás O’Leary makes an extraordinary claim on behalf of his family home. “We hardly spend anything on heating and hot water each year,” says the Irish architect, opening the door to his five-bedroom home, which sits on a one-acre plot of land on the rural fringes of Wicklow, a town one hour south of Dublin that is fast being subsumed into the capital’s commuter belt. “Last year, we spent just €240 (£190) heating our space and water – and that includes our swimming pool. In comparison, a ‘normal’ house this size in this area would cost 10 times that to heat.”
O’Leary has built Ireland’s first certified “passive house”, and he is justifiably proud. The passive idea was conceived 20 years ago in Germany by Dr Wolfgang Feist and it positively drips with common sense. The foundation of passive housing – the standards of which are now overseen by the Passive House Institute in Darmstadt (passiv.de) – is that the building needs to be airtight (sorry, no cat flaps). It’s equally important that the building has an expansive south-facing elevation that contains most of the windows. These two features together give the best chance of using the sun’s free and, even for the British Isles, abundant energy.