Tobin House, Curragh, Cork

Solearth Ecological Architecture

It is not often we undertake one-off houses in the countryside for a number of reasons but principally due to concern over the lack of sustainable rural practice that prospective clients often demonstrate. However the Tobin House intrigued us: it had both a modest design brief and at the same time the clients did indeed have the intention – so often missing in rural housing – of making that all important connection with the land and tying their house into the energy cycles and material flows that make up the site and the wider bio-regional context. This part of county Cork is both beautiful in an undramatic way and also close to the city itself. It has thus become popular with one-off house builders and the narrow lanes are scattered with building projects usually of the ubiquitous concrete block and PVC; it was then very refreshing to find our clients so willing to leave the norm behind them.

The house’s position on the top northern end of the site is necessarily practical in reducing the length of road required whilst giving it some space around; there is also a tentative building line established by a neighbouring older farm. The site is part of the better drained land in the field and allows the house to be orientated to the south in order to maximise passive solar gain. And in a quiet way it is important too to ask permission of the site for the disturbance you will visit upon it – this site seemed accepting.

As such the building is a simple essay in passive solar design: a heavy weight wall to the north-side protecting, durable and well insulating; to the south of this a lighter-weight timber framed element with larger glazed openings and a sun space as a solar collector for the house. The plan follows this logic too; the less inhabited service spaces – bathrooms, cloakroom, utility - form a northern buffer zone to the living and sleeping spaces to the south. The living and sleeping spaces in turn are separated by the centrally placed sun room with the sleeping areas to the east for the morning sun, the living to the west. The building, though compact, is also linear stretching out its form as if to bask in what ever sun rays will come its way. A first floor room sits astride the hall below and ostensibly houses the tank and controls for the solar and geothermal systems but too allows room for a place to sit and gain a wider view across the valley.

We built the north wall in 425mm thick poroton block which formed both a structural wall and – in a single skin – constructed an above-part-L insulated envelope. The blocks – imported by ship from Germany by FBT - are rendered externally and plastered internally; it is understood that FBT are eventually intending to set up a manufacturing plant here in Ireland, continued demand permitting. Their standard 365mm block co-ordinates well with their pre-made lintels and beams; the 425, used because of its higher insulating values, required more site work to create lintels and beams, it is hoped that FBT will eventually too standardise this system to facilitate its usage.

The timber frame is of Irish grown Spruce and constructed by Leitrim based Green-tek who also provided the Panelvent sheeting and the Donegal-sourced western-red cedar cladding. The timber frame was constructed as stick-build on-site with a small crew; it is a low-tech enterprise employing both locals and Green-tek’s Leitrim team: Conor McManus is keen to see a future where each townland would have such a team building domestic scale timber frame and utilising Irish timber. The walls and the timber framed roof are insulated with sheep’s wool bats from Ochre who assure me that they are increasing the Irish wool content of their bats. Both wall and roof are constructed as a breathing wall build-up with internal vapour check membrane and plasterboard to establish a five-time greater moisture-resistivity internally than externally.

The roof is clad in copper in order to give a discreet roof pitch and provide the first floor in the equivalent height of a standard bungalow. Copper looks well and will gently age with the cedar cladding; it is a high embodied energy material but of the metals one of the least toxic and most durable which, on this exposed roof, is crucial.

The house is off-mains for both water and sewerage and so provisions have to be made for this. A well provides most of the water and rain water is to be collected for garden watering; low flush toilets are now standard items and these empty into a septic tank before passing through a Feidhlim Harty designed reed bed system of vertical and horizontal flow beds before percolating back into the ground.

The house endeavours, through high levels of insulation, correct solar orientation and use of thermal mass, to benefit from passive heat gain. Actively it collects the sun’s heat through five square metres of flat plate solar panels mounted on the roof. These tie in with the ground source field collector for the heat pump and together they produce hot water for the underfloor heating pipes and general domestic usage. The design principal being that the heat pump can be switched off come April-May and the house can rely on the solar thermal panels alone until October. Efficient though heat pumps are, they do require an external power supply whereas the solar thermal collectors do not and thus, in terms of sustainability, maximising the solar both actively and passively would be our preferred option. Both systems were installed by Pure Energy Technology and the clients were also keen to utilise active heat recovery with extract fans installed in the kitchen and bathrooms which use the waste heat to pre-warm incoming air for the living areas and bedrooms.

Many of the loops have been closed in terms of the energy cycles on this project and in addition one element which the clients have also invested their time and energy into is vegetable and fruit growing. Before the ground was broken to build the house, they were already establishing the garden which will substantially reduce their dependence on shopping runs in the car and making an important in-road into reducing their ecological foot print.

In many respects the house has been very successful but as in all projects, there are lessons to be learnt. Our client courageously managed the building process and with no main contractor taking responsibility for time and costs the project has been slow with difficulties getting some builders to finish their work; ‘hidden’ costs have emerged too with the client paying for much of the plant hire and scaffolding hire – which due to the time taken has inevitably mounted up in cost. A main contractor would have a tighter rein on sub-bies and have wanted to finish the job faster. On the positive side, the client’s knowledge of the building is now very comprehensive and the hands-on approach has given a sense of belonging and care that is often missing in this otherwise commodity-driven building market we inhabit.