Affordable housing drives timber innovation in Denmark
A search for improved quality and sustainability combined with increasing prices and long delays on conventional construction, has lead Danish social housing companies towards timber construction.
Current timber technology takes off in manifold directions with promises beyond lower costs and shorter erection time. Compared to concrete, wood also provides a cleaner environmental footprint, reduced overall energy consumption, curbing of climate change, a healthy indoor climate and support for circular economy (recycling), as well as seamless integration between BIM and computer aided manufacturing.
This has put the spotlight on timber construction to produce energy efficient and truly affordable housing, which also supports political ambitions to further responsible environmental and social values, as well as city-central housing for the average civil servant, such as policemen, school teachers and hospital staff.
The big questions for architects are: can we design good, sustainable and socially cohesive housing schemes at low cost? Do we still believe in ’the good life’ for the average middle class worker, as well as for a growing class of ’urban poor’, such as unskilled migrants and unemployed?
Together with non-profit housing administrator, KAB, Domea and Al2bolig, Vandkunsten Architects are trying to provide positive answers to these challenges, without making claims to final thruths.
While the traditional construction industry has not produced many new answers to such contemporary problems, it appears that relevant innovation is happening in the timber industry, which is booming with inventive spirit, excitement, as with the entry era of reinforced concrete 100 years ago.
Incentives to look for new options are further provided in the current building boom: Considerable delays in the prefab concrete industry, which dominates the Danish construction sector, make room for alternatives.
To show the span and current trends in affordable timber construction we will here introduce three current building cases from the office. All are social housing schemes and display different use of timber .
Almen+ modular housing concept. 5th generation
The housing concept Almen+ (Non-profit Housing Plus) keeps the rent low by optimizing efficiency and architectural quality. The concept uses traditional light frame timber prefabrication, based on factory-line module assembly.
Each of the new Almen+ concepts are based on evaluation of the former generation, changes to building regulations, new energy requirements, as well as improvements in construction, logistics, architecture and HVAC technology.
The concept is inspired by one of the most popular Danish ’workingclass’ housing - the nineteenth century three-story townhouses (’the potato rows’) that is dense living with a high degree of social interaction. The average rent in Almen+ developments is about 23% less than in other, comparable non-profit housing. This is made possible in part by means of energy optimization, by using durable low-maintenance façade materials, and by replacing traditional but also costly craft methods with pre-fab wood-based units.
The box module construction system is cheaper than conventional concrete structures – and has also cut resource consumption in half.
The three-storey homes are simply three modular timber boxes, placed on top of each other, creating a minimum of three rooms plus bathroom.
The homes are delivered partly as empty ’lofts’, with few walls, minimal kitchens and without built-in domestic appliances. This to keep building costs low - and allowing DIY residents to exert their own influence on the interior design.
The 5th generation Almen+ challenges the basic genericness of ’the box’ (which has a tendency to make all rooms look the same) by protruding the ground floor level, creating a better functional hierachy between living and sleeping areas, and a better overall sunlight distribution.
The newest settlements are mixed with 25-30% ’micros-appartements’ (30-45 m2), of one and two rooms, reserved for financially poor inhabitants, but prepared to merge into 90 m2 family units - which is made easy by the light frame construction.
The urban dwelling concept is very popular with long waiting lists. There are currently four new settlements of the 5th generation Almen+ houses under way.
The Thyme Garden. Affordable rowhouses in solid timber.
’The Thyme Garden’ (Timianhaven) is a simple two-story rowhouse project in greater Copenhagen. The apartments are family units built for the Domea non-profit housing cooperation.
Interestingly the decision to use solid CLT-timber construction derives from the contractor.
The contractors at Adserballe and Knudsen have stated that they fell for timber’s extremely fast and accurate erection, which allows different teams to work simultaneously on the building site, thus saving time and money.
But the contractor also emphasized that the building site ’smells good’ compared to a concrete based site and that it is unusually quiet, dust free and clean. The building components can be worked with simple tools: ’two guys and a drill’ - bringing greater satisfaction to the workplace.
The ambition is to build as simple and affordable as possible, without vapor barrier, leaving parts of the interior solid timber panels exposed, making the walls breathable, and thereby creating a warmer and healthier interior climate.
The Wood Stock building system.
Buckminster Fuller once asked Norman Foster ’how much does your building weigh?’ The question can be seen as a measure of the poetic elegance of a lightweight construction as well as a rough measure of the environmental footprint of a building.
The American writer and ecologist Stewart Brand nuanced this in the book How Buildings Learn (1994), asserting that there exists no correlation between a buildings durability and the use of heavy materials (such as brick, steel or concrete), because building durability is always a function of ’weak links’ - and it’s inherent adaptability to changing circumstances over the course of its lifespan.
Therefore any building should be built with ‘shearing layers’, separating the structural layers according to their individual lifecycle.
The Wood Stock building system (invented by Vandkunsten Architects and Moe AS), takes its cue from Stewart Brand, and devise of a multi-story building concept for three to eight stories, optimized in terms of weight, but also in regard to adaptability of the primary structure and its connected subsystems, such as facade panels.
The multi-story building is inspired by current trends in hybrid building construction, and consists of 90% timber and approximately 10% of steel and concrete, using each material to its best advantage.
This allows for an extremely fast and lightweight building system that is both internally flexible and easily adaptable to future needs, thereby reducing lifetime costs.
The building system is put to the test in the Aarhus suburb Lisbjerg where six individual building types are currently erected with a program mix of social housing for students as well as families.
As one of the first housing projects in Denmark, the settlement will be certified in the DGNB system to ’gold standard’, Approximately 50% of certificate points are provided by the environmental credentials of certified timber and the affiliated adaptability and cost-efficiency of the structure.
As a point of notice, both interior and exterior cladding consists of easily replaceable and untreated spruce boards. Untreated wood that on the interior will allow the walls to breathe and improve the interior climate. On the exterior the wooden facade is allowed to weather naturally, without treatment.
text from ´'Go2Wood COMPENDIUM' / kim dalgaard