文章 Articles

A fallacy of steel and glass

America's flashy skylines consume far more energy than buildings in China, explains James Connelly. As Chinese cities modernise, they would be wise to avoid the mistakes of the west.

Article image

Among its many environmental challenges, China faces an enormous increase in energy consumption by buildings over the coming decades. Bricks and mortar already account for 25% of China’s total primary energy consumption, but are currently consuming energy at a very low level compared to developed countries. In fact, Chinese urban buildings consume three times less energy per unit of floor area, and 10 times less energy per person than those in the United States.

By examining the historical trajectory of building energy consumption in developed countries like the United States and Japan, we can find clues to what lies ahead for China. As per capita GDP rises, building energy usage intensity (EUI) – a measurement of the amount of energy used per unit of floor area – also increases.

China’s EUI is currently the same as Japan’s was in the 1960s and America’s in the 1950s.
Since then, advances in heating and cooling technology have transformed how buildings are designed and operated. Along with the changes in lifestyles and consumption habits that have come with rising incomes, this transformation has led both the United States and Japan to double their building EUI. Unless this shift in design mode can be slowed or prevented, China can be expected to see a similar surge.

Most western architects and engineers are surprised that China’s buildings consume such a small amount of energy. In general, Chinese buildings have less insulation, leakier skin and windows and less advanced and efficient heating and cooling technology than their counterparts in developed countries. But they still manage to consume much less energy. Why? The explanation for this paradox lies in two interrelated factors: lifestyle and system design. Understanding how the combination of these factors drives increased energy consumption is critical to preventing a future boom in the amount of energy used by Chinese buildings.

In China, energy-consuming appliances – most importantly clothing dryers – are less widely used and Chinese occupants are more willing to accept larger ranges of temperature in their indoor environment. Utility bills also make up a greater proportion of disposable income, which encourages people to save money by saving energy.

But differences of habit and income don’t alone explain the large gap between the energy usage of Chinese and western buildings. The culture of low energy consumption is also influenced by design of heating and cooling systems
, as well as architectural form. Professor Jiang Yi at Tsinghua University describes China’s standard heating and cooling system as “part-time part-space”, while the US most commonly uses a “full-time full-space” method.

Advances in Heating Ventilation and Air Conditioning (HVAC) system technology in developed countries have made possible the rise of fully enclosed glass structures, in which one very large system provides all the services for the building in nearly continuous operation. A standard Chinese building, on the other hand, uses operable windows and decentralised systems, where each room has its own air-conditioning unit or heater. In “part-time part-space” operation, building occupants actively control the temperature
in individual rooms, while in “full-time full-space” operation, the system generally has automatic controls based on a set schedule.

As GDP rises, the preference
for centralised systems over decentralised systems has played a major role in the increase of building energy consumption. A study by the building science department at Tsinghua University in Beijing found that residential apartments with centralised HVAC systems consume up to 10 times more energy than those with decentralised systems.

While counterintuitive, the explanation is simple: decentralised system
s allow users to individually control the system to maximise efficiency, while centralised systems provide continuous heating and cooling, regardless of what the residents actually require. Although centralised systems may be more efficient at converting energy into heating or cooling, the continuous operation and energy wasted by heating every room for the entire day far outweigh the efficiency gains. In fact, it is impossible to individually control temperature in order to save energy in many sealed office buildings that use a “full-time full-space” system. System design influences an occupant’s lifestyle and energy consumption, and it is system design that is the main cause of American buildings’ high energy consumption.

The transition to developed-world design standards is already under way in China. Energy data from a sampling of buildings in different Chinese cities shows that the energy use distribution is developing a two-peaked arrangementa large number of buildings clustering around a consumption rate of 30 to 50 kilowatt hours per metre squared per annum (or Kwh/m2×a) and another smaller group cluster around the 120 to 150 Kwh/m2×a rate.

The first of these groups comprises standard Chinese projects consuming energy at China’s average rate, while the second are the
buildings designed according to developed-country standards. This phenomenon is not only clear in charts, but is also noticeable in any Chinese city skyline: huge numbers of developing-country housing blocks are clustered around a core of modern buildings that would make any foreigner feel they were in a new and flashier version of New York, with correspondingly flashy levels of energy consumption.

What, then, can be done to stall this transition in China to an age of more energy-intensive buildings?

One established tool for encouraging a more environmentally friendly built environment is the suite of green building rating systems. By providing an objective certification of a building’s environmental performance, such systems can help transform the building marketplace so that developers, governments and designers have an economic incentive to pursue environmental objectives. The rapid growth of the two most popular rating systems in China, Leadership in Energy and Environmental Design (LEED), created by the United States Green Building Council, and 3-Star, a Chinese system designed by the Ministry of Housing Rural and Urban Development, is an encouraging development. 



There are some question marks, however, as to how effective these rating systems are at reducing building energy consumption in China’s current state of development. A big problem with LEED is that, on average, Chinese projects are already much more efficient than the American standard. LEED has been shown to decrease energy consumption by 24% percent over the commercial baseline in the United States, but even the best LEED projects are barely more efficient than the average Chinese building. 

Is 3-Star better? Anecdotal evidence suggests that the energy performance of some of the best 3-Star building is very impressive – around 79 Kwh/m2×a, much lower than the LEED performance average of 218 Kwh/m2×a. However, according to green building experts with experience on these projects, there are still problems maintaining comfortable indoor temperatures and humidity levels. Even though 3-Star projects are performing well in terms of energy consumption, if the indoor environment is suffering, they cannot necessarily be considered efficient.

On the other hand, one of the main drivers of increased energy consumption in developed countries is round-the-clock operation of building systems in order to provide a consistent indoor temperature. It may simply be the case that some sacrifices in indoor environment, and adjustments in occupant behavior and requirements, are necessary to build a truly efficient building.

For the moment, the best answer for China seems to be complementary use of both LEED and 3-Star. It is inevitable that China will continue to build US-style sealed office towers in the near future, even though they are less efficient than buildings with decentralised systems and should be discouraged. And in these types of projects, which employ fully centralised HVAC systems, LEED has proved effective at reducing energy consumption.

3-Star is more likely to be applied to projects that are heated in a decentralised manner, and the low energy consumption number demonstrates that it is a successful system for these types of projects. In short, both rating systems are effective in their respective market in China: LEED for high-class office and residential projects that are already designed to
western norms and 3-Star for more standard decentralised projects.

More research into the actual performance of building
s from both rating systems is necessary in order to accurately assess the potential environmental impact of the different approaches and efficiency measures taken. Only by clearly understanding how much energy each certified project is consuming can we ensure these rating systems are effective tools to slow the growth of China’s building energy consumption.

And let’s hope we can, because if China and the rest of the world’s developing countries follow in the architectural footsteps of the United States, then the global climate is in a lot of trouble.

James Connelly is
Fulbright China Research Scholar sponsored by the US Department of State based at Tsinghua University in Beijing and a LEED accredited professional. He blogs about his research at ChinaBuildsGreen.com.

Homepage image by  Stuck in Customs

Now more than ever…

chinadialogue is at the heart of the battle for truth on climate change and its challenges at this critical time.

Our readers are valued by us and now, for the first time, we are asking for your support to help maintain the rigorous, honest reporting and analysis on climate change that you value in a 'post-truth' era.

Support chinadialogue

发表评论 Post a comment

评论通过管理员审核后翻译成中文或英文。 最大字符 1200。

Comments are translated into either Chinese or English after being moderated. Maximum characters 1200.

评论 comments

Default thumb avatar
chs

促进评估体系的运作

评估体系显然是一个节约建筑能耗的可行方法。可是,政府方面必须予以鼓励和制定法规以确保评估体系的顺利运作。此外,中国能否以经济激励的方式推动绿色建筑评估体系也是一个问题。

Incentives for rating systems

Rating systems are clearly a promising method for promoting building energy efficiency. I'm curious about the interface between regulations and rating systems - government incentives and regulations are necessary to make sure that these rating systems are implemented widely and effectively. Additionally, are there way to economically incentivize the adoption of green building rating systems in China?

Default thumb avatar Reply arrow
jamesc

回复:促进评估体系的运作

LEED和三星体系都是非强制性的建筑能效测评体系,因此这两体系的普及率高度依赖开发商的使用意愿。开发商以这两个体系对销售价格的影响以及能否使项目更受欢迎为考量。此外,政府的补贴方案也有助于绿色节能建筑的开发;中国政府在四月发布了一份政策文件,着重推广三星评估体系的使用。此政策建议给予获得二星认证的建筑45元人民币的补贴,而获得三星认证的建筑则可以获得80元人民币的补贴。与此同时,政府也希望能在2020年时可以实现30%的新建筑通过绿色建筑认证。如果这个补贴项目的申请程序能够精简且透明化,我认为这对绿色建筑的推广会是个极大的推动力。

reply: Incentives for rating systems

LEED and 3-Star are both voluntary rating system, which means for the most part their growth is dependent on developers choosing to pursue them for the market benefits, either through higher lease prices or better project visibility. Subsidies could potentially also play a role in encouraging developers to build green. In April China released a policy document outlining a subsidy system to encourage 3-Star development. The document proposes a 45 yuan subsidy for projects that achieve 2 star and a 80 yuan subsidy for 3-Star. It also calls for 30 percent of China's new construction to achieve green building certification by 2020. If the application process for the subsidy is streamlined and transparent, then it should make a significant difference.

Default thumb avatar
melody

改变行为很重要

这真是一篇好文章,感谢你的分享!如同你所说,生活方式和系统设计确实会影响建筑物的能源消耗量。

除了政策驱动,三星体系或LEED体系外,我认为公众行为改变是关键,也是达到节能目标的可持续之路。透过一系列的教育计划,公众的行为可以得以改变和管理。另外,考虑公众需要什么信息,以及如何通过技术进步构建节能需求至关重要。新科技产品能对消费者的生活方式产生直接影响,因此这也是一个更好的交流渠道。要避免能源的使用率上升,必须从工业及居民两方面著手。

The importance of changing the behavior

That is really a very good article! Thanks for your sharing! I agree with your statement that lifestyle and system design are interrelated factors influencing the building energy consumption.

Besides the policy motivating, 3-Stars or LEED, I think the behavior changing of the public is essential and a more sustainable way to reach the energy saving goal. It could be changed and managed through a series of "education" plans. And considering more about what information the residents need, how to build their energy-saving requirement through the technology progress is vital. New products maybe the closest stuff to affect consumers' lifestyle, so it will be a much better communication channel to educate consumers.Therefore, the establishment of green power and green sight both in industry and residents is equally important to prevent the increasing energy-consumption.

Default thumb avatar Reply arrow
jamesc

回复:改变行为很重要

我完全同意行为和生活方式很重要,教育亦能影响生活方式。建筑师和工程师必须考虑系统设计对行为的影响。人们根据周围环境调整行为模式,比如在能源意识高的社会长大的人,如中国,总会记得关上房间里的独立空调;但是当他们遇到没有独立开关的中央空调是,就会产生完全不同的消费行为。让人们自己控制操作系统是鼓励节约能源的最佳方法。因此,我们必须注意系统设计,如同重视环境教育一样。如果中国像美国一样建造完全中央控制的摩天大楼,教育也难以防止日益增长的能源消耗。

Reply: The importance of changing the behavior

While I absolutely agree that behavior and lifestyle are important, and that education can impact lifestyle, it is equally important that architects and engineers must consider the impact of system design upon behavior. People adapt their behaviors according to their environment. For example, someone growing up in an energy conscious society, such as China, who always remember to turn their decentralized AC unit off when they leave a room, will have a completely different energy consumption behavior when they interact with a centralized system that has no easy on/off switch. Giving people individual control over their system is the best way to encourage them to save energy. Therefore we must pay attention to system design just as much as we pay attention to environmental education. If China's builds completely centralized skyscrapers like the US, there is no amount of education that could prevent huge energy increases.

Default thumb avatar
energy-rm.com.hk

2022年形势依旧如此?

10到15年前,传统建筑(低舒适度)及新式建筑(高能源使用率)之间的建筑物能源消耗强度(EUI)差异是绿建筑会议的常见讨论话题。到2022年及之后,情况会依旧如此吗?作者在回答Melody的同时,指出了一个重要但常被忽视的因素——可管理性。不仅是工程师,建筑师应尽快将可管理性纳入设计。可管理性是一个降低由居住者行为造成的高建筑能源使用率的超低成本方案。

Will the 2022 story remain the same?

This disparity in EUI between traditional (low comfort) buildings and new (high energy use) buildings was a common topic at green building conferences 10 to 15 years ago. Will the story remain the same in 2022 and beyond? The author's answer to Melody's question points to a significant and under-addressed factor: manageability. Not just engineers but also architects need to take it upon themselves to design-in manageability at the earliest possible moment. Manageability is the ultra-low-cost way to harness the high percentage of building energy use attributable to occupant behaviour.