Author: Niall Crosson, BTech, MEngSc, MIEI, CEPHC, senior technical engineer, Ecological Building Systems
Five pioneering low-energy buildings were chosen by the German-Irish Chamber of Industry and Commerce to showcase the coming together of German technology and the Irish appetite for energy efficiency. The five projects were presented at the Chamber’s event, ‘Showcase – Made in Germany’, which was held recently at the Aviva Stadium, Dublin.
The projects featured a range of energy efficient technologies applied across domestic, industrial and commercial projects. They reflected an Irish energy policy and building regulations that are ambitious, progressive and sustainable and illustrate how the rapid change in Irish building regulations has led to an increase in energy efficiency and building quality.
One of the award-winning projects was a certified ‘Passivhaus’, which was completed in Mount Merrion, Dublin in 2012. The Passivhaus was a collaboration between Ecological Building Systems Ltd, Fahy Fitzpatrick Consulting Engineers, Des Crabbe OA Studios and Advanced Timbercraft.
The concept originated in Germany and refers to a rigorous, voluntary standard for energy efficiency in a building. The first Passivhaus was built in 1990. These buildings are not limited to domestic premises and may also include non-domestic buildings, some of which are already constructed in Ireland.
Passivhaus buildings focus on a ‘fabric first’ approach to building design, with an emphasis on high levels of insulation, no thermal bridges, exceptionally high levels of airtightness combined with an effective ventilation strategy. Once these variables are optimised, the heating and cooling energy required to maintain a comfortable healthy living environment is minimised.
While this two-storey house in Dublin city does not aesthetically stand out from adjacent buildings, from an energy performance perspective, the house is extraordinary and performs on a completely different level. For between 10% to 20% of the cost paid by the homeowner’s neighbours, the owner can heat the house for an entire year. This 256-square-metre certified Passivhaus, completed in 2012, used German products and technology to ensure maximum energy efficiency, comfort and minimum energy costs.
Building a Passivhaus in Ireland
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Internal view of the Passivhaus[/caption]
The Passivhaus was commissioned by a client who wanted an eco-friendly building, built using the highest quality materials. During the building process, which began in 2010, the only major hurdle was the weather in Dublin, as it was the coldest winter in 130 years.
Architectural technician Des Crabbe took over the management of this project for the clients, after a previous architect had completed drawings.
According to Crabbe, convincing the planners to allow him to knock the existing house and rebuild was a challenge, as the local authority was keen to see the dwelling renovated instead. But once he compiled a report demonstrating the energy performance of the proposed Passivhaus, they were convinced, provided he maintained the oriental aesthetic appearance of the original building on the new house.
The new building is a timber-frame construction, manufactured and erected by Advanced Timber Craft. Building with timber frame presented many benefits, including a short turnaround on the erection of the building and thermal insulation. It also meant that airtightness continuity could be more easily planned at the planning and erection phase, trades could also be streamlined with Advanced Timber Craft’s in-house installation team and utilising timberframe reduces complexity and the carbon footprint of the building.
The use of the German building materials and their configuration in the building envelope created a ‘healthy and breathable’ wall, while maintaining the high level of insulation required for Passivhaus certification.
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GUTEX Thermowall woodfire insulation[/caption]
The house’s external walls are insulated with 80mm GUTEX Thermowall wood fibreboard insulation, manufactured from wood sourced from the Black Forest in Germany. THERMOWALL combines a thermal insulation with a durable, diffusion open-plaster system. Applying the woodfibre insulation externally ensured thermal continuity was optimised and thermal bridges were eliminated, a crucial part in realising Passivhaus certification. The woodfibre board also features outstanding acoustic properties.
The architect was keenly aware of the importance of combining high levels of energy performance with optimal building durability. The GUTEX woodfibre insulation complimented this as it features exceptionally high levels of breathability. In this way, the timberframe walls have a high drying capacity in the event that unforeseen moisture was to penetrate the building envelope.
This type of insulation was also chosen as the home owner insisted that only CO2 neutral/ negative products were used in the build. Finally, the woodfibre insulation also features very effective heat-storage properties, an important part of reducing the risk of overheating in summer months.
Airtightness and air quality
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Attention to detail to meet airtightness targets[/caption]
High levels of airtightness are a central part of attaining Passivhaus certification. To meet the standard, buildings must achieve an air-change rate of less than 0.6 air changes per hour at 50 Pa, over 10 times more airtight than the current backstop values required to comply with TGD Part L for new Irish domestic dwellings. To attain the high levels of airtightness required, the building design and building schedule had to be rigorously planned to ensure the potential for air leakage was minimised.
Pro Clima INTELLO PLUS intelligent airtightness membrane and associated tapes and seals, forms an airtightness and vapour control layer for the building. On completion, the building achieved 0.52 air exchanges per hour under a pressure difference of 50Pa, almost 20 times tighter that the level of air leakage required to comply with Irish Building Regulations at the time (TGD Part L 2008).
This level of airtightness, the quality of the installation and the quality and performance of the airtightness components ensures this level of airtightness is not just reliably attained when the building is built, but durable for the lifetime of the building. A Paul Novus 300 mechanical ventilation system with heat-recovery system ensures healthy indoor air quality is maintained at all times.
The homeowner only needs to have the heating on for a maximum of 20 days a year (at just a lukewarm level) and consequently pays about €300 to €400 annually for heating and hot water. There are three radiators in the whole house, two in the open-plan TV room and kitchen, and one in the bedroom which has never been turned on.
Plans for the future include the expansion of the house’s KNX energy management system, which helps control the already very limited energy usage, in order to further monitor and therefore eliminate energy waste completely.
Niall Crosson BTech, MEngSc, MIEI, CEPHC is a senior technical engineer with Ecological Building Systems. He can be contacted at046 94 32104 or niallcrosson@ecologicalbuildingsystems.com. See www.ecologicalbuildingsystems.com for more details.