Passive Attack by John Moorehead

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All was not well when work began on this impressive Co Cork home and its architect had to pull out the stops to make the eco-home fit the brief

A problem with the design of a passive house in Co Cork made its designer, John Morehead, go hot and cold. A fault in the climate information, that was used to regulate the airtight, ventilated and draught-proofed house, meant the house was too cool. Passive house designs are so sensitive to the environment and climate that even heat from a plasma television can throw the controlled temperature off kilter.

Morehead, an architect with the Cork firm Wain Morehead Architects who specialises in designing passive homes, was concerned to get all the details right when he embarked on a new project on the shoreline of the upper Owenabue estuary, in Carrigaline.

Building had just started on the two-storey, four-bedroom family home and, while the greatest care had been taken to find ecological and energy-efficient materials, it was clear that everything was not as it should be.

“We commissioned the job of sourcing climate data to specialists in Britain,” says Morehead. “We were working off Dublin data, not local data, and suddenly we found we didn’t meet the passive-house criteria. By this stage, we were already on site. We didn’t eat for a week — it was that serious.”

It took three weeks for Morehead and his team to put the mistake right. Intensive research was carried out to try to find out what was putting the data out of sync. Readings put the house at a temperature that was far cooler than first anticipated. There was also less radiation, which can have a big impact on passive-house technology.

“It turned out there was a fault in the way the climate data was being generated,” says Morehead. “It operated on peak-data information — the extremes rather than the averages. To make the house passive again, we had to tweak the specifications. We did this with the help of a local climatologist, but it was three weeks before we were back on an even keel.”

The result, though, is an impressive and unusual contemporary house in a lovely setting with striking views. It is the home of Sally and John O’Leary and their three children. The couple approached Morehead about building an energy-efficient home in August 2008, and work began the following year. They had been refused planning permission to build a previous modern design on the site.

The refusal was based on context rather than aesthetics, and the fact it would be built on a sloping site that ran into the Owenabue estuary was also a concern.

Around that time a neighbouring house was being developed, so it was important for both the O’Learys and their new neighbour to maintain privacy and preserve views, as well as to keep the planners on side.

“Our brief was to design a four-bedroom family home and to be as ecologically friendly as possible while sticking to a budget,” says Morehead. “Our clients were interested in an energy-efficient home and one that would bring the outside space in, merging into the interior.

“The family also wanted natural finishes and a design that was relatively simple. There had to be a focus on food and cooking because that is what they love to do.”

Morehead came up with the modern yet simple passive house in Carrigaline, which was completed in April this year. It has almost 2,600 sq ft of living space over two floors. The home is at the cutting edge of passive-house design, and is one of six certified passive homes in Ireland. A name plate by the front door proudly displays its Certified European Passive House status.

The project did not begin with the intention of building a passive house. “It was originally intended to be an A-rated passive solar project and the decision was made to seek passive-house certification as late as the tender stage,” says Morehead.

Passive house certification is a quality-assured energy-performance and comfort rating that demands stringent control of both the design and construction process.

To make the most of the views and to accommodate the sloping site, the living area was put upstairs. It overlooks the estuary and contains a central winter garden, which enhances the notion of bringing the outdoor space in.

The area has become a multipurpose room, whose use changes with the weather and the seasons. “It is a busy spot, encouraging participation in activities by young children at the principle accommodation level, irrespective of weather,” says Morehead.

“The room is fully insulated from the remaining accommodation, so it can become an outdoor space without compromising the rest of the house or thermal envelope,” he adds.

“Both the expansive glass wall from this room to the hall and the screen to the deck fold away to make a versatile indoor/outdoor space penetrating deep into the bowels of the dwelling.”

Particular care was taken to ensure the home was as airtight and insulated as possible. A cement substitute made from the by-product of the iron and steel industry was used instead of conventional concrete, a decision that saved more than 16 tonnes of CO2. The walls were clad in panels of fibre-cement. It is a low-maintenance material, a consideration that was important in the coastal setting.

Because so much of the work was undertaken during the recession, Morehead and the O’Learys hired local tradesmen and builders when they could.

The upper walls and roof were made from closed wall timber-frames, also manufactured locally. “This construction had exemplary insulation and airtight characteristics,” says Morehead.

“These walls also assist with moisture transfer during periods of high humidity. The upper walls were covered with a rain screen of a carefully selected and detailed untreated Austrian larch cladding.”

To achieve a home that maximises heat gain, Morehead sought out technology to minimise heat loss. Triple-glazed windows with low-iron glass increase transmission of solar heat. The air temperature is controlled to such an extent that no internal surface temperature within the house deviates by more than 4C, even if it’s -10C outside.

The kitchen is an important feature for the O’Learys, who had stressed that they were keen cooks, and it has been given a linear corner window that not only frames views of the river, but also maintains privacy by preventing it from being overlooked by the neighbouring house. The room has direct access to the multipurpose area and the upper garden.

On the upper level there is also a guest bedroom, laundry, study and family room.

The brief had also asked that the needs of a growing family were taken into account. The house should adapt to the children as they grow. To meet this request, the children’s bedrooms surround a large, open multipurpose play area.

The kitchen, along with the living and winter garden areas, has an innovative infrared heating system that Morehead developed himself and is now patenting. “The infra-red emitters heat the occupant, not the air,” he says. “Therefore a level of individual comfort control can be enjoyed independently.

“As with the sun’s energy, 40% of which is infrared, the occupant and indeed any warm-blooded creature, absorbs and responds to this energy through their skin and their inbuilt circulatory system. Heat is then distributed evenly and at a pace to suit the comfort criteria of the body.”

Solar water heating comes courtesy of tubes at roof level and rain water is used for both sanitary and gardening use. While Morehead is coy about the overall cost of the build, he is keen to press home the savings that can be made on home heating, especially at a time when energy companies are raising prices.

“You can heat a home like this for just €150 to €200 a year,” says Morehead. “You are independent of all the price hikes and can live with consistent comfort levels.

“The project confirms that a carefully tuned passive solar design can meet the passive-house standards cost effectively.”