Revolutionary design principles keep a lid on energy costs
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Klinikum Frankfurt Höchst is the world’s first certified passivhaus (Passive House) hospital. The German term refers to design standards, which include harnessing the power of the sun and internal energy sources as well as conserving heat with airtight building methods that drastically reduce the energy a building must consume to keep it warm.
In the five years following 2010, the total area of buildings certified by the Passive House Institute — the industry body based in Darmstadt, Germany — increased from 380,000 to 1.3m square metres, according to Zeno Bastian, head of building certification at the organisation. A further 500,000 square metres have been added since.
While the majority of these buildings are residential homes, Passive House methods pay large dividends when used in buildings that guzzle power, such as those related to healthcare.
The Passive House Institute estimates electricity consumption in a hospital is three to four times higher per square metre than that of an equivalent-sized residential building. Patients require warmer temperatures than office workers — at Klinikum Frankfurt Höchst, a new 664-bed hospital building, the temperature will be set at 22C.
Maintaining a sterile and odour-free internal environment, meanwhile, means there are unusually high air-circulation requirements. Much of the lighting must be left on all night. Power-hungry technical machines — from those required in the accident and emergency department to those that support the operating theatre and patient rooms — are a huge drain, too. Magnetic resonance imaging equipment alone, in the new Frankfurt building, will account for 7 per cent of the total power consumption.
The Passive House Institute estimates that 40 to 60 per cent of energy in a hospital can be saved using a passive house construction compared with a conventional building.
Passive House buildings are not only for cold climates. “All of the five principles of passive house design work to keep buildings cool as well as to keep them warm,” says David Grindley, an energy expert at the estate agent Savills in the UK.
So-called “ventilation with heat recovery” sees the stale air containing heat from devices such as a TV or fridge passed out across a lamella — a thin plastic membrane — through which it either transfers the heat to the incoming fresh air or sucks additional heat from it to keep the building cool. In humid climates, adapted lamellae affect the opposite process for moisture, sucking this out from the incoming air and expelling it.
The three remaining principles — glazed windows, insulation and airtight construction — all work to keep the air at the right temperature in the building until it is time to get rid of it.
In Mexico, the US border town of Nogales is completing a building project of duplex homes on the edge of a desert that each require 13cm of insulation and triple-glazed Passive House-certified windows. “Two low-energy units [per house] will provide the only heating and cooling needed throughout the year,” says Mr Bastian. In spite of a local construction sector that is generally unfamiliar with passive house building techniques, the project has already passed the airtightness test.
Where economies are expanding quickly, Passive House techniques are most efficient in new homes. In China, the Gaobeidian Railway City development, which is under construction, will comprise 1.2m square metres of homes and offices as well as a kindergarten and a school when complete — making it the world’s largest certified Passive House settlement. Other developments are in train in Tianjin, Beijing and Qingdao.
In developed economies, population growth is lower and planning laws often favour the retrofitting of older buildings, says Mr Bastian. He estimates that two-thirds of certified Passive House units in Germany are adapted buildings rather than newbuilds.
Financial incentives spurring the adoption of Passive House construction techniques take various forms. In Mexico, funding from the EU’s Latin America Investment Facility is aimed at developers through loans and grants to cover the expenses related to achieving greater energy efficiency (technical support from an international consulting firm is also available). The initiative aims to fund up to 600 houses built under the Passive House standard, to achieve a reduction of 80 per cent in greenhouse gas emissions.
Other efforts focus on incentives targeting homeowners. Grants for triple-glazed windows in Germany are available through KFW, a government-owned development bank. In Wales, the government has just made energy-efficient homes more appealing, mainly to first-time buyers of new homes under the UK government’s Help-to-Buy scheme. Since more energy-efficient homes can be run at less cost — meaning there is more money left over for mortgage payments — those buying them are now eligible for larger mortgages.