Ultra-low energy homes are not necessarily architectural boutique projects: above are low-income “passive” terrace houses in Lindas, Sweden
It’s been one of the most challenging articles I’ve had to write, as I had to leave out so much, but at the same time one of the most satisfying. This is a hugely important topic. Buildings account for up to half of all energy consumption, and are the biggest single contributor to greenhouse gas emissions. Much attention is given to exotic future remedies, such as carbon sequestration and clean coal. But a way to slash emissions using existing technologies is sitting under our noses: simply rethinking how we design the buildings we live and work in, to use much less energy.
The arguments for building with energy needs met largely by marrying with the local environment and passive strategies are so compelling that the research for this article is persuading me to switch my own plans to buy a place in French Touraine, where I live, to instead build a zero-energy home — no small challenge though, given that French builders are far behind their German, Swiss, and Austrian neighbours here.
I’ve posted just a few of the links I collected during the research to here on Connotea, and hope to add more.
It’s impossible to excerpt from an article of this length in any sensible way, but just to give you a flavour, here below are a few:
The latest report from the Intergovernmental Panel on Climate Change (IPCC) estimates that improvements in the energy efficiency of buildings could potentially reduce projected global carbon emissions up to 29% by 2020, and up to 40% by 2030. Moreover, the IPCC’s estimates are deliberately conservative, based on a pessimistic view of how rapidly the building industry can reform its practices. If the reforms could somehow be accelerated, the reductions in fossil-fuel energy needs could be that much more dramatic.
Such a speed-up is certainly possible — in principle. Voss and his fellow ‘green-building researchers’ have already developed and tested many of the necessary tools and strategies, to the point where they can now build homes, offices and other buildings that use 80–90% less energy than existing buildings. The most efficient of these structures are almost completely ‘passive’, meaning they require very little, if any, traditional heating or air-conditioning. Yet the overall comfort they provide is, if anything, superior to existing buildings. Nor is there necessarily a cost penalty: these ultra-energy-efficient buildings are often no more expensive to build than conventional structures, and work out far cheaper if energy bills during their occupation are taken into account.
In practice, however, getting the construction industry to change its ways is a daunting prospect. Especially in the developed world, more than a century of cheap energy has divorced the architecture of buildings from energy considerations, and from their environment. Most builders and architects today haven’t got a clue how to design buildings with ultra-low carbon emissions.
And even if they did, there is the sheer scale and diversity of the trillion-dollar worldwide building industry — a vast labyrinth that involves as many different professions and sectors as there are sorts of wallpaper, plus an almost unlimited number of types of buildings, regulations, norms, materials and environments. In the face of all that, “the major impediments to increase energy efficiency in the building sector are institutional barriers and market failures rather than technical problems,” notes a report on green buildings published last year by the United Nations Environmental Programme.
There is a “sea change” underway, says Gregor Henze, an architectural engineer at the University of Nebraska-Lincoln in Omaha. Carbon emissions weren’t even on the radar of most architects five years ago, he says, adding that the number of architect firms, construction companies and other members of the US Green Building Council is “exploding”
Many of the technologies are already mature. Almost two decades of research, mainly in Europe, has resulted in designs for fully passive houses that require primary energy needs of 15–50 kWh/m2/year — compared with current-generation European houses that typically require 160–300 kWh/m2/year — and need only supplementary heating or cooling, in tiny amounts, or just on the coldest and hottest days.Such efficiency levels make the buildings amenable to being made zero-carbon by meeting their low energy needs, either from small, local renewable sources, or using grid electricity generated from renewable sources.
Passive-house design uses extreme insulation of the building envelope — including triple-glazed windows, often filled with an inert gas — in particular, in an effort to eliminate what engineers call ‘thermal bridges’. These are fault lines, typically at the window frames and at the intersection of floors and walls, where large, unwanted energy transfers occur with the outside. The result is an airtight ‘skin’ that prevents energy leakage. Thermograms of buildings then show impressive gains in ‘nega-watts’ (see photos, right). With insulation like that, the building can get its heating from the solar gains through glazing as well as through waste heat from appliances and even our bodies.
Another key technique for temperature control in passive houses is at first counterintuitive: simply let fresh air in from the outside. A pump draws fresh air through a grid of pipes buried several metres underground, where the temperature is relatively constant throughout the year, 10–14 °C in the United Kingdom, for example. When this fresh air arrives at the house, its temperature has already been modulated — warmed up or cooled down by the ground, depending on the season. Then, in a second trick for heating, the incoming fresh air is put through a heat exchanger to recover 80% of the heat from the warmer stale air being expelled from the building. This system of air-based cooling and ventilation not only saves energy by recycling heat, but vastly improves air quality.
Another concept tested in the study was to circulate water in boreholes drilled up to 100 metres down, and then pass the water in closed circuits through concrete slabs in the ceilings of the building. The water was a relatively warm 17 °C. But there was so much of it that the cooling effect was comparable to that achieved by air-conditioning compressors. “We use the environment, the ground, as a heat sink,” says Wagner.
Many new German houses now use such slab cooling, or ‘thermally activated building systems’, which were pioneered in Switzerland. The buildings require only very small amounts of energy; all they need is a small pump. A multi-million-euro renovation of the United Nations offices in Geneva, Switzerland, will use a similar system, drawing water from Lake Geneva.
These systems will work in even the hottest areas of California, Wagner maintains, although a small amount of conventional air conditioning might have to kick in during the late afternoon to keep temperatures below what people have become accustomed to. “But it would reduce most of the current needs for air conditioning.”
“The need is to build more demonstration passive buildings, to show everyone from carpenters to house purchasers that it is not such a strange thing to build an energy-efficient house,” says Wall, “and that not only do these buildings work, but they are actually superior to conventional buildings.”
The article opens with a quote from a pioneer of low-energy buildings in Germany
“It felt surreal,” says Karsten Voss, thinking back to January 2008 and the winter meeting of the 50,000-member international heating, cooling and ventilation research association, ASHRAE. “Here we were sitting talking about zero-energy buildings, one of the biggest topics on the programme, inside a hotel that had no proper glazing or insulation — while it was ?10 °C outside.”
and ends with this:
Nonetheless, it is still an open question how quickly passive architecture strategies, combined with renewable energy sources, will become the mainstream of construction. The good news is that the interest is there. Witness the turnout of 30,000 delegates in Chicago last November at the “Greenbuild” conference — which was opened by former US president Bill Clinton. On the last day of the conference, Maria Atkinson, head of sustainability at Lend Lease, a multinational real-estate company, threw out a challenge that should please Voss. “The hotels of Boston have 12 months to step up to the challenge of ensuring they are green for Greenbuild 2008, because this year’s delegates will be demanding green hotels as part of their commitment to green buildings.”
Green buildings are too often a nebulous concept, and for the purposes of this article, devoted to potential impact of design on energy efficiency and climate change mitigation, I strived in much of the initial research to define what the article is, and is not, about:
1. Not green buildings in general, including water, air quality, local ‘green’ materials etc, but strictly energy, as this article is about sustainable architecture and climate change. An analysis of the life cycle energy consumption of a building reveals that the big three energy consumers – heating, cooling, and lighting – are all affected mainly by architectural DESIGN. Yes, energy efficient appliances and lightbulbs are important, but if you want to take out the biggest energy wedge, then it’s about building in energy efficiency in design from the outset. There is too much muddle out there on what is ‘green’ building – faced with climate change we need a very sharp focus.
2. It is about the residential mass market that needs to be hit if we are to impact on climate change, and the problems of getting green architecture widely adopted, and not on some of the exorbitant, if sexy, green skyscrapers, and office complexes etc being built.
3. It is not about future elegant new materials etc, no matter what their scientific and technological appeal, but on the bread and butter technologies we already have
4. It is about architectural and engineering design, not renewable energy, though there is some overlap in control systems and storage. This vast renewable energy debate is important re buildings, but is somewhat separate, and an excessive focus on solar panels etc can sometimes detract from the gignificance of the basic issue of designing for energy performance in the first place.
5. Unfortunately, I regret, not about urban planning, in particular in emerging economies such as China, India, and Brazil — this is enormously important, but will require a complete separate article.