Award Winning Low Energy Passivhaus in Mount Merrion, Dublin

Award Winning Low Energy Passivhaus in Mount Merrion, Dublin


Five pioneering low-energy buildings have been 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 on November 27 2014 at the Aviva Stadium, Dublin.

Opening the event, Reinhard Giese, of the German Federal Ministry of Economics and Energy, spoke of the mutually beneficial relationship between Ireland and Germany in the area of energy efficiency.

The projects featured a range of energy efficient technologies applied across domestic, industrial and commercial projects. They reflect 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 featured at the event was a certified Passivhaus completed in Dublin in 2012. Passivhaus refers to a rigorous, voluntary standard for energy efficiency in a building which originated from Germany, the first of which was built in 1990. Passivhaus’s are not limited to domestic buildings and may also include non-domestic buildings, some of which are already constructed in Ireland. Passivhaus building 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 doesn’t aesthetically stand out from adjacent buildings, from an energy performance perspective, the house is extraordinary and performs on a completely different level. For 10 to 20% of the cost which the homeowner’s neighbours pay, the owner can heat the house for an entire year. This 256 square metre certified Passive House completed in 2012 used high quality German products and technology to ensure maximum energy efficiency, comfort and minimum energy costs. The passive house 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 Des, convincing the planners to allow him to knock the existing house and build new, 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, thermal insulation and airtightness continuity could be more easily planned at the planning and erection phase, trades could be more streamlined with Advanced Timber Crafts experienced in house installation team, and utilising timberframe reduces complexity and reduces the carbon footprint of the building.

The use of the German building materials and their configuration in the building envelope created a very healthy and breathable wall, while maintaining the high level of insulation required for Passive House certification.

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 highly 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 were to penetrate the building envelope. The GUTEX woodfibre board 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.

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 exceptionally 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 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 high 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 high performance 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 in a year (at just a lukewarm level) and consequently pays about €300- 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.

The owner of this building, who works in building services engineering, has a great trust in the “Made in Germany” brand as being synonymous with high quality and best engineering practise. In fact, many other state-of-the-art German products and technologies have been used within the building’s timber-frame fabric: Daemstatt cellulose and Thermo Hemp natural insulation, KNX energy management system, switches sockets, kitchen appliances, fuse box etc. Even the car sitting in the driveway is German!


Internal view of completed Passivhaus


Plans for the future include the expansion of the house’s energy management system, which helps control the already very limited energy usage, in order to further monitor and therefore eliminate energy waste completely.

 Presenting the award for the Showcase; Made In Germany. From left to right: Des Crabbe, Aideen Keenan, Niall & Monica Walsh, Reinhard Giese, Peter Smith, Neil Orr

Presenting the award for the Showcase; Made In Germany. From left to right:

Des Crabbe, Aideen Keenan, Niall & Monica Walsh, Reinhard Giese, Peter Smith, Neil Orr


  • Featured German products: pro clima Intelligent airtightness system; external wood fibre insulation from GUTEX
  • Irish supplier: Ecological Building Systems ltd.
  • Project architect: Des Crabbe OA Studios
  • Engineering company: Fahey Fitzpatrick
  • Construction Company: Advanced Timbercraft

Building information

  • Size of building - 286sqm
  • Number of stories - 2

Energy Efficiency

  • Space heating demand: 11 kWh/m2/year
  • Heat load (PHPP): 7 W/m2
  • Airtightness: 0.53 air changes per hour at 50 Pa

By Niall Crosson, Technical Engineer, BTech,MEngSc,MIEI, CEPHC

GUTEX THERMOWALL woodfibre insulation fitted to external walls of the building
High levels of attention to detail was required to meet onerous airtightness targets