A Low Tech Approach to Energy Saving with Porotherm Clay Blocks

Featuring solid Porotherm Clay Block walls, the six-storey '2226' house ensures that temperatures will remain between 22°C and 26°C.

While buildings require less and less energy, more and more is being spent on the maintenance and service needed to sustain this reduction. The prospect of buildings functioning as mini power stations is highly reminiscent of the promises of Modernism.

More comfort with less energy '2226' is an archetypal sustainable building. The basic idea is to achieve an extraordinarily high level of comfort whilst using as few technical systems as possible. As a result, the six-storey building does not require any heating, cooling or mechanical ventilation.

Architect Baumschlager Eberle focused his attention on reducing to a minimum the number of elements within the building that require costly maintenance and technical servicing and relied instead on solid Porotherm Clay Block walls and the air-cleansing effect of lime, high ceilings and large room depths, elegant materials, effective air circulation and the optimum use of daylight.

The building is named '2226' expressing exactly the temperature range — between 22°C and 26°C which the indoor climate is designed to arrive at by totally natural means. In other words, the new building is basically a passive house in the original and actual meaning of the word.

The necessary temperature stability is ensured first and foremost by an enormous thermal mass: the outer walls consist of 76cm thick brickwork, divided into an inner, 38cm thick layer of load-bearing vertical coring bricks and a further 38cm of insulating bricks with a high percentage of core holes — specifically for the European winter.

The six-storey building has a square-ish plan with centrally located structural core walls forming a pinwheel configuration that divides the internal spaces. Floor heights of 3.5m and the vertical orientation of the windows ensure natural light reaches deep into the spaces.

External walls are constructed with two layers of masonry block, each 36cm thick, and are rendered externally and plastered internally. The specified masonry units are from Wienerberger's Porotherm range of hollow clay blocks. These are laid with 1mm bed joints and, due to their interlocking plan shape, no perpend joints.

Insulation is only used for the floor and roof slabs; the air pockets within the clay blocks provide the walls' thermal resistance. Both skins of block are in Porotherm, although the specification differs to provide greater strength to the inner skin and greater thermal efficiency to the outer skin. The building has no heating, ventilation or cooling system, the flow of energy being controlled by human hand.

Stellaria NZ currently has several projects across NZ at varying stages of planning/construction to achieve this exact same result — '2226'. Stellaria's buildings use single-skin Porotherm R25 Th+ with triple glazed windows by Internorm, and will meet an energy requirement of 7kw/m²/a. Passive house criteria is 15kw/m²/a.

Working with thermal and Sound Engineer, Lubos rajci from Soundtherm, New Plymouth, NZ's Porotherm houses will provide all year-round comfort and ventilation with minimal heating and cooling — everyday appliances and human activity will be sufficient to heat these homes.