Dating from the 1860s, 100 Princedale Road in the Holland Park area of London doesn’t, at first glance, look to be much different from any of the other houses in the terrace. But it is. Octavia Housing is aiming to register it as the UK’s first certified retrofit to Passivhaus standards.
Passivhaus buildings are designed to provide high levels of occupant comfort while using very little energy for heating and cooling because space heating requirements are drastically reduced. All this is achieved through meticulous attention to detail and rigorous design and construction according to principles developed by the Passivhaus Institute in Germany.
My past experience of houses built to these standards has been of projects very much in the grand designs mould, indeed I went to visit one house just north of Dublin in Ireland to write it up for Grand Designs magazine. As I walked up Princedale Road I knew that retrofitting a Victorian house to Passivhaus standards was something very different and, in many ways, much more challenging. Indeed the press release asked the question ‘Can a Victorian home reach strict Passivhaus standards?’.
Judging by what I saw the answer appears to be yes. The Passivhaus standard required the home to use less than 15kWh of energy to heat it per m2 per year, compared to the UK average of 130kWh. The refurbished home’s CO2 emissions and energy consumption will be cut by an estimated 83% and 94% respectively through the energy saving works – an estimated £910 a year saving on fuel bills.
This is achieved through a variety of measures including high levels of insulation, air tightness and the minimisation of thermal bridging. The reduction in energy consumption means that there isn’t a conventional heating system. Instead, a self-designed ‘labyrinth’ heat exchanger beneath the insulation in the basement provides pre-heating in winter and cooling in summer. Hot water is supplied by a combination of solar thermal, air source heat pump and waste water heat recovery. Triple-glazed, imitation sash windows were developed in-house to meet strict conservation area requirements.
The question for me is at what cost was all this achieved. And I don’t just mean the financial cost – funding for the project came through the Technology Strategy Board’s Retrofit for the Future competition – but the cost in terms of the potential loss of historic fabric and what might potentially end up in landfill as a result. In the case of Princedale Road, I’m assured that very little of the original remained due to the many alterations that the building had undergone over the years. Even so, the chimney breasts were removed to compensate for the space lost through installing internal insulation and one senses that the gutting of the interior was pretty thorough.
The question of whether this is wrong, and whether it precludes the Passivhaus approach in old buildings, is undoubtedly one that must be considered. Indeed, it brings us to the wider retrofit debate and the degree to which original fabric is dismantled or disturbed. The means of achieving the sort of energy savings being sought are often, by their nature, invasive and there certainly appear to be few easy answers.
Image credit: Octavia Housing