Low-energy houses

Low-energy houses have been built in Ireland since 1991. That is at least how long Scandinavian Homes Ltd. have been providing pre-manufactured low-energy Swedish timber-frame houses to the Irish market. The company was founded in Galway in 1991 by Lars and Linda Pettersson. At that time these types of houses were considered very radical and the general public was quite skeptical. Only one house was sold the first year. Since then a total of 301 individual houses have been built by the company in Ireland. The emphasis is energy-efficiency and here the Swedish building methods and traditions play a large role. High levels of insulation and an air-tight building envelope in conjunction with ventilation heat-recovery systems and triple glazed low-emission-argon filled glass are important factors. A cost efficient approach to build Low-energy houses must follow rules of simplicity. The designer of a house must be aware of the negative implications of complex architectural shapes. Some features might be culturally correct and fashionable – but be aware of their energy consequences.  Dormers, roof-windows, bay-windows, long and narrow extensions to the main body, split levels are examples of  features that cost energy in practice.

The components of a building which are necessary in any case can  be optimized for low energy losses.

  • The building envelope: shape and orientation.
  • The windows and doors: performance and orientation
  • The ventilation-system: performance

The standard houses offered can be described as  “low-energy”. By optimizing these components further to the point at which a separate heat distribution system is no longer needed yields savings which help finance the extra costs of improvement of the energy performance.

The introduction in 2005 of the completely Passive-house upgrade redefines what is possible to accieve and sets a new standard of energy-preservation.


A passive house is a house in which heat-losses are reduced to such a degree that no separate heating is necessary. Superinsulation, absolute air-tighness, elimination of all cold-bridging combined with a heat-recovery ventilation system are the key elements of a Passive house. The U-values of the exterior building components generally range between 0.1 and 0.15 W/m2C. The standard has been named “Passive House” because the passive heat inputs – delivered externally by solar irradiation through the windows and provided internally by the heat emissions of appliances and occupants – essentially suffice to keep the building at comfortable indoor temperatures throughout the heating period. It is a part of the Passive House philosophy that efficient technologies are also used to minimize the other sources of energy consumption in the building, notably electricity for household appliances.

Passive house is the term mostly used, but this type of house can also be called: Zero-energy house, Body-heat house, House without heating. First we try to define a passive house. A passive house is a building in which a comfortable interior climate can be maintained without active heating and cooling systems. (Adamson 1987 and Feist 1988) Criteria for a Passive House per m² living area:

  • Max. 10 W/m² constant heating-load or
  • Max. 15 kWh/m²yr annual space-heat requirement
  • Max. 42 kWh/m²yr annual total amount of energy input

Sustainable houses

Amazing reductions in energy demand and the economic advantage of extremely low running costs are the obvious plus-factors for the passive house concept. As well as this, a building-ecological advantage can be recognized. At the projecting stage careful considerations are made for every minuscule detail of the building. The physical performance, as well as the environmental impact of all materials used are analysed. The passive house represents the most consistent concept of sustainable building today. During the construction stage the Passive house concept requires quality workmanship emanating from a good understanding of the passive principles by all participants. This inclusive approach has been highly appreciated by the workmen and has further increased the motivation and work-satisfaction.

Will the number of passive and low-energy houses increase dramatically in the coming years?

In Germany, experts predict a substantial development in the passive and low-energy house market. In a survey done in 2004 among 180 architects, engineers and house-manufacturers it was estimated that on average, nearly every fifth new building will be a Passive house, and every third, a Low-energy house by the year 2010.


There are few reasons not to build all new houses to the Passive-house standard or at least to the Low-energy-house standard says Lars Pettersson. The advantages are so clear – low or no heating costs, increased living comfort – provided that the building costs are manageable.

The identified drawbacks are few. Condensation occuring on the outside of the triple glazed super energy glazing in the morning. Some people will miss the traditional fireplace, and some people do not like the complete silence – no noise from the wind or birds singing can penetrate the layers of insulation.

Public awareness

During 2004, Sustainable Energy Ireland, SEI, the renewable energy information office, REIO, in Cork has managed to increase the public awareness of the passive house concept. Scandinavian Homes Ltd. in Galway  has noted an increased interest in this desirable concept. However, there are many terms to keep track of. How many people know the difference between: kW and kWh, heat energy rating and primary energy requirement? There is Passive-house concept and Minergie concept. We also hear about passive solar design meaning sunlight through windows in any house. Lars Pettersson says that it is confusing to the general public, and that he has a feeling that the term Passive house will soon degenerate into catch- phrase to promote all sort of products. Just like the phrase fat free is used to sell Cheerios and Frosties!

The first production-line passive house in the world in Galway

By simply improving the standard low-energy house Scandinavian Homes has built the first standardized passive house in Galway in March 2005. The company expected to build the house at marginally higher costs than their normal Low-energy house. A passive upgrade package is available that makes the standard Scandinavian Homes house a Passive house. Many of the prerequisites of a Passive house are already in place in the standard house.

Passive houses – but where?

The modern pattern of development with various functions of life separated has contributed greatly to the almost complete car-dependence of today’s Ireland. It started over hundred years ago with the French “zone industrial” and the English “industrial estates”. Work activities were more or less forced by the planners to be concentrated to designated areas. Uniform housing was built in planned developments lacking a natural mix of activities such as shops, workplaces and schools.

The older natural pattern of development grew organically with local and regional variations, often resulting in the charming older villages and towns that are still so attractive. Maybe it is time for the establishment to rethink what has been done the last 100 years?



All this about passive houses is fantastic – isn’t it?  But where can they be built? In Ireland there seem to be two ways of building today: Either cram in as many poorly built houses as possible in estates around urban centers. They are built on very expensive residentially zoned land,  and often there is no scope for sustainable design at all. Or suburban sprawl along the country roads. Sometimes, if you are lucky, you can apply passive solar design at the same time as you follow the rules of building line and entrance-door facing the road.

Sustainable design should include proximity of public transport and possibilities for car-pooling. Eco-clusters of mixed housing possibly including houses with apartments.

Lars Petterssons idea is to allow the building of medium to high density small eco-clusters of sustainable houses adjacent to major roads. These roads have bus services leading to towns and villages and the people in such clusters can easily car-pool. Affordable by location away from the most expensive land and by increasing the density. They could consist of, say,  a couple of houses with 4-6 apartments  and 5-10 individual houses of varying size and cost. In such clusters it is possible to integrate social housing in a natural way. Rich and poor, people in different stages of life – young and old – could live here.

These eco clusters can be built concealed from view from the road but still be walking distance from a bus stop. They can be built by people forming a coop or by people just getting together to realize their dream of a reasonable sustainable and affordable life.