Eco friendly Passive House at Athenry Co. Galway
‘Nothing Rattles.’ Says Scott Cook of his Athenry Home. ‘In standard houses, you get doors and windows rattling all the time. That doesn’t happen here, even though we’re in a very windswept spot. Plus it’s quiet. All that insulation also keeps out noise.’
A passive house built by Passive House builders in 2010, Scott says it could hardly be more different from the house he and his family used to live in. ‘Chalk and cheese. It’s far more comfortable. In a standard house, you’re constantly shutting doors to try and keep heat in. Now you get a uniform temperature everywhere.’
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Timber frame house under |
Service cavity insulated with |
Glulam beam supporting |
Construction started in August 2009 with the installation of the insulated foundations. Eliminating cold bridges is central to passive house building. Cold bridges are thermal weak spots through which heat passes from the insulated envelope of the house to the outside. We completely insulated the raft using expanded polystyrene (EPS), plus we used low carbon concrete. This work took ten days to complete, at the end of which we had a totally cold bridge-free foundation for our house to sit on.
We used a timber frame structure with cellulose as the main insulation, though rock wool, wood fibre boards and OSB board were also incorporated at different stages of the build. Whenever possible, we try to use materials with a low carbon footprint, thereby making sure that the house has low embodied energy as well as low energy-in-use.
Glazing is minimised on north, east and west elevations, where bedroom, bathroom and circulation areas are, while extensive glazing on the southern elevation allows for maximum passive solar gains in living areas. The passive house windows are triple glazed with insulated frames to minimize heat loss. Effectively, these windows operate as radiators for the rest of the house.
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South Gable window |
Led lighting |
Certified PassivHaus Front door |
Eliminating uncontrolled air penetration is another vital element of passive design. Installing the air-tight barrier that makes this possible requires a great deal of care and attention, not just from the team who install it, but from all of the tradespeople onsite during the build. Air tightness, it should be said, isn’t about living in a plastic bag. It’s about an end to leaky buildings, and making sure that air only gets in the way it’s supposed to.
An independent air-tightness test gave us a score of 0.28 air-changes per hour (ACH), which is a brilliant result, and indicates that there are effectively no draughts anywhere in the house. It also guarantees long life for the building by eliminating the possibility of moisture penetrating the structure and damaging it, and nor is there any risk of mould growth. Mechanical heat recovery ventilation (MHRV) goes hand in hand with a high level of air tightness. It delivers filtered air without compromising the comfort of the building.
LED lighting was used throughout the house to further reduce energy demand. In all, we installed seventy two-watt lights, so that the total energy demand when all the lights are on is 140 Watts, less than two standard light bulbs.
Evacuated solar tubes are used to provide hot water all year round. We also installed a small wood burning stove to cater for the building’s small space heat demand, and to boost hot water in winter time. The total heat load for the building is eight watts per square metre or 10kwh/m2 per annum. To put it another way, a litre of oil per square meter will heat this house for the year. This is a 200 square meter building, so that works out at 200 litres of oil for the entire year. That’s a reduction of nearly 90% on a standard home.
Planning is everything with passive. Though the house took only five months to build, we took another five months before that to work everything out. We’ve had all sorts of weather since Scott and Ann moved in two years ago, but even during that cold snap early last year, the internal temperature never dipped below 20 degrees.
