Green Building Lecture: One Low Energy House's Search for Zero Carbon

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moycullen_house.jpgWith Dr Shane Colclough, University of Ulster


Tuesday 20 November 2012 | 18.00 – 20.00 | Central Hotel, Exchequer St | €20 | Buy online or 'Pay Now' | Discounts available for Éasca, PHAI, IGBC and Cultivate Members - Call 01 674 5773

The second in our Green Building Lectures Series.

The combination of a low energy house and the Irish climate is a winning one. It has already been demonstrated that it is possible to reduce the space heating demands of a house by 80% through building to standards such as the Passivhaus standard.

During this talk we go one step further and show that for such houses the Domestic Hot Water (DHW) and space heating energy consumption can be reduced by another 70%, bringing the house very close to Zero Energy.  We focus on a real house that was monitored for three years. We review the theory, the actual results achieved and also see if the approach makes financial sense. We also review whether the approach makes “Carbon Sense” as we try to approach Zero Carbon, i.e. are we using too much embodied energy compared with the amount we are saving?


Computer Modelling has demonstrated that Temperate Maritime Climates experienced in cities such as Dublin, offer the greatest opportunity for solar assisted space heating in Europe. While the modelling shows that a theoretical maximum combined Solar Fraction (SF) of 77% is achievable for a house under study, during the talk we review the actual solar heating results achieved in practice.

The paper also demonstrates the viability and potential of Inter Seasonal Energy Storage when combined with solar domestic hot water and space heating systems. Figures are presented giving the extent to which direct and stored solar energy assisted in approaching zero carbon heating in the Passivhaus under study.

A Life Cycle Cost Analysis is carried out for the Solar and ISES installation. It was found that the least cost option in the long-term for providing domestic hot water and space heating was through the use of a solar heating system comprising Solar panels, DHW installation, direct solar space heating and an Inter Seasonal Energy Store.

When Annual Energy Usage is reduced to very low levels, a focus is required on the embodied energy of the systems employed in order to ensure there is a net benefit. Thus, a carbon analysis is carried out and an analysis of Annualised Embodied Energy and savings in Annual Energy Usage is presented. The carbon analysis showed the solar system enabled an annual operational avoidance of 874 kg of CO2, representing a reduction of 75.3%. The life cycle energy analysis demonstrated an annual operational benefit of greater than 4.5 times the Annualised Embodied Energy of the solar heating system.