Zero Net Energy Building – the new standard

Posted on Posted in Blog, Green Building

Bullitt-CenterMy professional background is in construction and the building industry, and so I tend to pay close attention to information about green building initiatives and sustainability developments in the built environment. Thus, it was with interest that I learned this year marked the first time ever at a UN climate conference that a day was devoted specifically to the building sector.

Paris Conference “Buildings Day”

The COP21 “Buildings Day” gave special focus to the building industry and the contribution it can make to help with achieving the overall targets of the conference. Despite granting limited attention in the past, it seems the international community is now acknowledging the importance the role buildings play in climate change, and is recognizing that without significant action by the building sector, the targets will not be met.

Between 30%-40% of all energy use occurs in operation of buildings through lighting, heating and cooling, plug loads and other building functions. Yes, that’s a percentage of all energy used in the in the developed world. As such a large contributor to climate problems, finding solutions to reduce this energy demand and simultaneously generate renewable sources of energy is a necessary focus to take in the overall discourse.

As part of the conference commitments, the Green Building Council of Australia has announced that in 2016, it will introduce a new label for that recognises “NetZero” building achievements for energy with the goal of pushing the building industry further in the direction of a net zero philosophy for new buildings and for retrofits.

Zero Net Energy (ZNE) building is a rapidly emerging trend that combines modern energy-efficiency technologies, integrative building design principles, and renewable energy systems to deliver resilient buildings that have little to no net consumption of fossil fuel produced grid energy.

This is a significant step by the GBCA to provide ambitious targets for owners, designers and builders to strive for that could lead to significant advancement in building best practice and reduction of fossil fuel usage. The Zero Net Energy benchmark for buildings represents unprecedented potential to transform the way buildings use energy, and is a revolutionary approach in how we think about new construction, building renovation, campuses and even whole communities.

Zero Net Energy target 

While there are various technical definitions for different types of ZNE buildings, the basic concept is that of a building that consumes no more energy over the course of a year than it generate with onsite renewable sources. This is achieved by significantly improving the overall operating efficiency, employing the use of passive heating and lighting systems, and in some respects modifying occupant behaviour to minimise energy use. As a result, typical ZNE buildings require only 25% of the energy when compared to a similar traditional building, and thus the requirements for on-site produced energy in the form of solar, wind or cogeneration are greatly reduced and achievable.

Common to ZNE and ultra-low energy projects is a critical design approach: the inclusion of an explicit energy performance target in the design program as an outcome requirement. This performance energy specification gets included in all design documentation and is carried through to terms with contractors and subcontractors to ensure proper implementation.

The green building movement and the focus on energy efficiency in buildings, resource use and lifecycle analysis has had steady momentum for decades, but previously the goal of zero net energy has been just a lofty endeavour associated with high costs, complicated design and experimental demonstration. However, recently (in just the last few years) the pursuit of ZNE has become a real and possible benchmark as design teams gain experience and renewable energy generation costs have fallen.

Additionally, incentives and policy changes are encouraging the building industry to strive for ZNE with some jurisdictions already mandating hard targets in the near future. California has stipulated that 50% of new state buildings beginning design in 2020 must be Net-Zero Energy, and all new state buildings and major renovations that begin design after 2025 must be Net-Zero Energy. Check out the ambitious action plan presented by the California Public Utilities Commission (CPUC) and the California Energy Commission (CEC) to build a self-sustaining market for all new homes to be net-zero energy by 2020.

ZNE Techniques and strategy 

It is well beyond the scope of a simple blog post to detail the techniques and strategies in achieving ZNE, but some of the basic principles include:

Passive design features heat cool
– Strategic window placement and sizing
– Daylighting for primary lighting source
– Natural ventilation and operable windows
– Passive and evaporative cooling

Improved building envelope
– Increased insulation
– Minimised thermal bridging
– Efficient envelope

Advanced heating and cooling systems
– Ground source heat exchange
– Energy recovery ventilation
– Chilled beams
– Zonal control systems

Advanced lighting and controls
-Spot lighting and dimming
-Occupancy sensors
-LED and other high efficiency  

Central to a successful strategy of a ZNE building process is the commitment of the building occupants to participate in the ongoing optimisation of the implemented systems.  By introducing initiatives to actively engage the occupants, research has demonstrated positive behavioural changes can be realised leading to successful interaction with the building systems. Energy monitoring and dashboards, email reminders, and real time notification help to contribute to behavioural changes such as opening or closing windows and shutting down computers at night.

With increases in our use of electronic technology, a large focus of building energy is on “plug loads” which is essentially the aggregate electrical demand of all hardware that is plugged in. Once other efficiencies are introduced, plug loads can account for as much as 50% of the total building use. With low to no cost small behavioural changes, you can reduce your energy demand today in your current office or home by following this practical guide.

ZNE already underway 

The goal of ZNE is gaining traction. Two years after its completion, The Bullitt Center in Seattle is demonstrating its success in exemplary form and living up to the title “Greenest Building in the World.” Apple’s new headquarters in Cupertino and Tesla’s gigafactory are aiming for ZNE.  IKEA has recently invested in 98MW of wind energy to help the company reach its goal of being entirely ZNE by 2020. Bloomfield, Iowa – with its population of 2,640 – is heading down a path to become a  ZNE community by 2030.

The building sector offers one of the most cost-effective and economically beneficial paths for reducing energy demand and associated emissions while at the same time supporting adaptation and resilience to climate change. Successful ZNE projects demonstrate that proven technology, design and implementation methods now exist and are available today.


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