Massive yet passive

With huge variations in climate from arctic coastal areas in the North, to more temperate areas in the south, building passive houses in the Nordic region can be a challenge. Still, passive houses are popping up all across the region.

Passive, massive and modest. The new passive house in Oslo is designed to consume no more than 15Kwh in heating per square meter annually. (Photo: Stein Stoknes)

Recently the Norwegian capital Oslo got its first passive house. A stylish, yet modest looking villa in a residential area outside city centre. Over the years, simple and functionalist design has become almost synonymous with Scandinavian cool. But architect Karin Hagen from Medplan Arkitekter assures us that their building’s appearances has nothing to do with being "cool". In a city where temperatures can drop to -20C in winter, their focus is rather on how to stay warm.

- The building has a compact design to avoid heat loss, she says.

- All kinds of wings and oriels would only mean more walls, more outer surface and in turn more ways for heat to escape.

A passive house is not for people who enjoy intricate and decorative solutions it seems.

- A simple cube would be ideal, but there is of course always other factors to be taken into accounts. The point is that to achieve a low energy need you have to be aware of the design from the start of the prosess.

The down jacket

Central to making sure the inside stay warm when outside temperatures fall, is to avoid any thermal bridges. This means that no part of the construction are allowed to lead temperature from the outside environment inside, and the other way around. This is solved by practically building a house within the house.

- It is like the house is wearing a down jacket. The inner construction consist of 9cm thick massive wood. The massive wood construction is then padded with insulation, and in turn clad with an outer structure.

The inner structure is climatically tight and stays nice and warm, while a balanced ventilation system ensure a fresh indoor climate. 85 % of the heat is recycled; cold air coming in is heated by hot air going out.

The inner massive wood structure under construction. (Photos: Norsk Massivtre) 

Local timber

The inner massive wood structure consist of elements made from local timber by Norsk Massivtre in Valdres, Norway. The elements were brought to Oslo and assembled on site. Building in wood was a concious choice by the developer.

- It makes sense from an enviromental perspective. Timber is local a natural material. Building the house in metal and concrete would require a lot more energy. Wood as material stocks carbon dioxide, CO2, and plays a positive role in the CO2 budget and the greenhouse gas balance. With massive wood the effect of this is even better, explains Hagen.

The house also has solar collectors that covers 55 % of the energy needed for hot water as well as 15-20 % of the buildings annual heating needs.

Insulation came from Danish insulation experts Rockwool, while Swedish Endovent delivered ventilation and heating solutions. The whole project received support from Innovation Norway, Enova, the municipality of Oslo and the Housing Bank. The villa is a part of a larger research project supervised by the Sintef research institute, on low energy buildings in Norway.

Other Nordic environmentally friendly buildings

Villa Åkarp: Creating energy for the grid, Sweden.

Linesøya House: A Scandinavian pilot project which promotes sustainable architecture. An old school building from 1952 situated on Linesøya, off the coast of Central Norway, will be converted into a demonstration house for passive house retrofitting.

The Green Lighthouse: Denmark's first carbon neutral building.

Hof House: Designed for the extreme weather conditions of the Skagafjörður Fjord, Iceland, the Hof House relies on passive solar design, geothermal heating, and some pretty hefty concrete walls.

Paroc Passive House: Finland's first passive house was finished in may 2009.

A passive house saves energy through passive measures like insulation and designs to avoid heat loss.