I am flattered by the interest taken in Kelbrook House in Amersham (Letters, AJ 25.1.00).
It seems that Alan Kennedy and Mike Baldwin quite like the look of the building, but are anxious about how it addresses the issue of energy.
I have spent the past 25 years creating architecture based on a responsible approach to climate and energy use. A hospital in Singapore for which I had prime design responsibility while at YRM in the 1970s remains naturally ventilated, and without air conditioning. A personal obsession with lowenergy architecture has led to my running a 'zero-energy' diploma studio in the Plymouth School of Architecture. I am working in a management role on a new European Union initiative concerned with glass and the interactive building envelope, the COST C13 programme. It is concerned with the reduction of mechanical environmental servicing, and energy use.
Low-energy architecture is something I feel strongly about.
When a domestic client commissions a conservatory, interesting issues affect priorities. Anyone charged with such a commission will try to strike a balance between what the building is for, and the details which bring it to reality, both visible and invisible.
The principle of the sun space in passive solar architecture is well enough established for us all to know its environmental value. At Kelbrook House we were challenged to create such a space which could be used all year, and have an uninterrupted relationship with the garden. The winter condition is easy to assess, and Baldwin is right to say that TA S is not needed. The TA S programme was used to establish summer conditions which are potentially more prejudicial to comfort. The figures for that gain and loss are easy to assess by conventional means, although these fail to take account of thermal storage. We decided to use the mass of the structure behind, and a well insulated floor, to exploit the incoming short wave radiation. The figures for radiation and temperature used are those published in Page and Lebens' book, Climate in the United Kingdom, which gives mean impinging radiation averaged over all weather conditions, mean temperatures, and a host of other climate data crucial to an understanding of the environmental context of buildings.
Anyone reading this useful source of energy information (which allows for cloudy conditions in the relevant tables), will be able to calculate the monthly variations in heat balance.
Of course, it could be argued that the wall should have been double glazed, but the cost (and embodied energy) would have increased as significantly as the transparency would have diminished. The glass wall only comprises 34 per cent of the envelope of the building, but the decision to use single glazing was not taken lightly. The calculations for Kelbrook House showed that the conservatory (taken on its own, as a passive solar space) suffered a net loss of heat for just over two months of the year, in December and January: this uses conventional methods of calculation, but does not allow for the benefit of thermal storage. For the rest of the year it needed to shed heat. Double glazing would mitigate the environment for two months, at the expense of making it far worse for the other 10.
Ultimately, a small glazed extension of 34m 2added to an old brick house, for a family who decide they want it, is possibly a thermal indulgence for two months a year, but our job is to make sure that it is comfortable and usable for our clients, as well as being responsible and efficient. In our view, a possible marginal increase of energy to two months is worth the 'delight' it gives (a word used by our clients, who are now enjoying it).
If Baldwin cares to visit the school in Plymouth, I would be happy to discuss low-energy architecture with him. He will then see how our students are indeed inculcated with sustainability and responsibility from the first year onwards, with our low-energy diploma studio students being more capable in the field than many practising architects.
Michael Wigginton, the Designers Collaborative, Plymouth