Neues Rathaus Freiburg

Plans for one of the largest “passive house” social housing estates in Europe have been approved in Ireland. But the designers could still learn a thing or two about the latest thinking in sustainable social housing from Germany.

A total of 597 homes will be built on a nine hectare site by scenic Shanganagh Castle, on the coast, in Shankill, Co. Dublin. The estate will contain a mix of social homes to rent, affordable homes to purchase, and affordable “cost rental” homes.

Social housing estate near Shanganagh Castle in Dublin will be offered at cost rental, that is, when the rent is just sufficient to cover current and capital costs incurred by the housing provider, or no profit.

In Ireland, cost rental is when the rent is just sufficient to cover current and capital costs incurred by the housing provider – that is, they make no profit. Anyone not able to afford this level of rent gets housing support.  More than half – 306 of the homes – will be rented on this basis.

The estate – Ireland’s largest proposed social and affordable housing scheme – will also feature high bicycle parking provision (1318 spaces compared to parking for 365 cars), features to make it easy to work from home, and features to encourage a sense of community.

To further reduce the carbon impacts of travel, high frequency public transport will pass the site, and electric vehicle charging points will be provided.

Construction is expected to start in six months. It is being developed by Dún Laoghaire-Rathdown County Council and the Land Development Agency.

An Cathaoirleach, a local Green party councillor, said: “The development will offer people an attractive place to live that is close to key transport links and supported by a wide range of local amenities.  It will also serve as a flagship for sustainable development – with best in class environmental practice incorporated into the project from the outset.”

The Greens are now in a coalition in the Dublin government.

According to the architects, the development has been designed to achieve Part L Net-Zero Energy Building compliance and “a significant reduction in Primary Energy and CO2 emissions compared to a Building Regulation Compliant Residential Building to Part L 2018”.

A “fabric first” approach will be taken, with thermal bridging minimised, mechanical ventilation with heat recovery in each dwelling, automatic lighting controls, and a green roof system.

Site layout, separation distances and apartment layouts are designed to optimise natural light and views. Day lighting and views are also provided to communal corridors.

The project is expected to achieve an air tightness test of 0.6 cubic metres of air per cubic metre of room space per hour – an 88 per cent improvement on the Irish Building Regulations advised upper limit figure.

Multi-occupancy residential buildings will be served heating from an Energy Centre which will incorporate air-source heat pumps with back-up gas boilers, with the heated water distributed via a pumped low temperature distribution network.

Apartments will be fitted with a heat interface unit or heat exchangers to provide heating through radiators and instantaneous hot water.

If you think this is state-of-the-art, however, think again

The Dublin development will have external walls made from precast concrete, brickwork and render, the structure itself is prefabricated concrete, with internal party walls made a block work and in situ cast concrete.

In other words it comes with a huge embedded carbon bill that will have to be repaid. How can architects get around this problem?

Answer: by building with timber. In Germany, specifically Freiburg, cradle of the German green movement,is a eight-storey mass timber baugruppe with a grocery store on the ground floor.

Bugginger Strasse 52 in Freiburg-Weingarten

Project developer Willi Sutter and his client company IG Klösterle developed a concept together for Bugginger Strasse 52 in Freiburg-Weingarten (above), together with the city of Freiburg, for a timber building with construction costs, a total of 11 million euros (AU$17.9 million) no higher than for the solid construction method.

It is next door to a previously completed (in 2011) high-rise passive house accommodation renovation project.

By the end of May next year, 30 timber-frame rental apartments of various sizes from 35 to 80 sq m will be built on the six floors above the grocery store and basement – which will be built in concrete to provide a secure base.

Features include a day care centre, different floor plans for individual forms of living, assisted living groups, and six units for people from an emergency homeless shelter.

At almost 22 metres high, it is just below the high-rise boundary. Even the elevator shaft, the staircase, the insulation and the outer facade are made of wood.

The biophilic resource-saving and ecological timber construction means active environmental protection. The timber used is Germany-grown silver fir. The carbon dioxide that the trees absorb while growing remains permanently stored in the building and is not released back into the atmosphere, improving its carbon balance.

The architect, Weissenrieder, is responsible for many timber buildings.

The building is said to be the first in Germany to be FSC-certified. The project was funded by means of the timber construction offensive “Landesinnovationspreis” as part of the Holz Innovativ program.

Freiburg boasts several positive energy and timber buildings, including a city hall and day care centre (above), believed to be the world’s first public building with a net plus energy standard.

As the first phase of a comprehensive upgrading of the town of Stühlinger, located northwest of Freiburg’s old town, the buildings has larch wood facades from local stocks, with screwed-in and cantilevered facade modules equipped with photovoltaic cells and high-quality thermal insulation.

Add in thermal suction, solar thermal energy, heat pumps and other electrical photovoltaic panels on the roof, triple glazing and mechanical ventilation with heat recovery, as well as a heating and cooling ceiling system in the visitor areas, and the building generates more power than it uses.

You want a marriage made in heaven in the building sector? Go for passive house, plus-energy, timber build.

As American architect Mike Eliason says: “Passive house is the secret ingredient that makes mass timber buildings truly sustainable (bonus: nearly every other building, as well).”

David Thorpe is the author of Passive Solar Architecture Pocket Reference, and ‘One Planet’ Cities: Sustaining Humanity within Planetary Limits. He also runs the online course, a Post-Graduate Certificate in One Planet Governance. He is based in the UK.

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  1. Technical correction: “The project is expected to achieve an air tightness test of 0.6 cubic metres of air per cubic metre of room space per hour” should actually be *an airtightness test result of 0.6 air changes per hour at 50 Pascals.* (aka 0.6ACH50) This means 60% of the air volume in the house is changed by infiltration every hour when subjected to 50 Pascals of pressure during a blower door test. It is not representative of how much infiltration there is under typical conditions (i.e. much less than 50 Pa and varied on different facades etc) or what ventilation fresh air will be supplied (typically approx 30m3 per person per hour in a Passivhaus)