Dr Satish Kumar | PhD and LEED Fellow |President and Executive Director of the Alliance for an Energy Efficient Economy (AEEE)
Be Lean, Be Mean and Be Green – Strategy for Design and Performance of NZEB
To me, a Net or Near Zero Energy Building symbolises a building that delivers extraordinary high energy performance. The very low amount of energy required should be covered, to a very significant extent, by energy from renewable sources produced on-site or nearby. The symbolic power of NZEB denoted by solar panels on the rooftop is important but it is critical to place it in context and the impact that those steps will have, as NZEB is used as one of the solutions to reduce the impact of our built environment on our planet.
Be Lean, Be Mean and Be Green
When it comes to NZEB, I believe the above philosophy has served the design/engineering, technology providers and construction team very well. It should also be the mantra of policymakers so that the market is incentivised to take steps that are based on fundamentals and first principles rather than gimmicks that are not consistent with the whole philosophy of NZEB.
When it comes to design and construction of NZEBs, it is strongly recommended that the emphasis is on following the right process at the right time during the entire project. The following points illustrate the concept in a more tangible fashion:
- The owner/organisation must be clear about the objectives, requirements, the kind of design and consulting team that will be entrusted with the job along with a clear idea about the budget for the project. Getting the right team in place right at the beginning of the project will go a long way in achieving the objectives of the project.
- Pay close attention to develop the design and performance brief of the NZEB project. For example, a) The EPI of the building cannot exceed 25-50 kWh/m2/year; b) The cooling system efficiency must not exceed 0.65 kW/ton; c) Exceed minimum ECBC building performance criteria by 75% at the whole building level. Every effort should be made to ensure that the owner sticks with it and holds the design team accountable to the brief.
- Get the building design right through a combination of right selection of technology and design performance brief. This may sound like a simple and straight forward exercise but is fairly challenging. While many people associate NZEB with solar PV panels on the roof, there are others who believe that NZEB will be prohibitively expensive because of the high cost of super efficient technologies that has to be used to build them. These people, often overlook the large performance gains that one can have while designing the building from the first principles approach that can lead to significant load reductions.
- Select the right technology for energy-efficient equipment and systems keeping in mind the performance brief and the budget. Further, the competency and skill level of facilities management team and the resources that will be made available for regular and preventive maintenance will also be equally important. For example, most large commercial buildings today have an Integrated Building Management System – a fairly high-tech, networked, control system that relies on the meter and sensors in the building to collect data and use sophisticated built-in control algorithms to run the HVAC system without manual intervention. However, it is extremely rare to find such ideal scenario in a real world situation for a variety of reasons. Careful planning and assessment of technology being considered as well as a proficient operations team can spare a lot of heartburn down the road.
- Make a sound and rational decision about the on-site power generation from renewable technology by looking at the total amount of power generation (both in absolute terms and % requirement for the building) and how much it will cost. Make an informed choice about the impact the resources that are being set aside for on-site renewables if they are directed towards better design of building or more energy-efficient technologies.
If “Be Lean (load reduction through better design), Be Mean (meeting the loads with the most appropriate energy efficient technology), and Be Green (making an informed choice about the use of on of off-site renewables to power the building)” is deployed in this fashion, one can reduce the energy consumption by 50% at each of the above steps and bring down the EPI of an average building from 200 kWh/m2/year to 25 kWh/m2/year, making the job of building a NZEB very close to reality. The trick is to stick with the fundamentals and do the above things in the right order.
Automating the Measurement and Verification of Energy Performance in NZEB
As mentioned at the beginning of the article, it is imperative for any NZEB to have superior energy performance – a prerequisite in my opinion. Every green building or NZEB project starts with the intent to deliver high performance once the building is operational. And yet, we know that many buildings fall short of achieving that critical objective. Is there a solution and what can avoid this pitfall? Here is a three-point recipe, which if followed properly, should substantially reduce the risk of under performance and help achieve the goal of superior performance.
- Prepare a sound design and performance brief and hold the design team accountable to it. This has already been discussed earlier but it is easier said than done. The biggest challenge that will be encountered is the argument put forth by the design team that it is not possible to do this because of the distributed responsibilities and dependencies between teams and systems. My response to that is that designing an airplane or a ship is probably much more difficult and challenging with many more dependencies between critical systems and yet it is routinely performed in that industry. Of course, building industry is not as advanced as aircraft manufacturing, but the point to note is that it can be done. Is it easy? Of course not. Is it possible?Absolutely! And there are examples in India where some organisations are able to hold the design teams to performance briefs.
- Identify major load centres during the design phase, segregate those loads and specify a sub-metering infrastructure as the foundation for performance validation. This is the single-most important decision that MUST be required of the design team to ensure that accountability with respect to performance validation will automatically happen in the project. The beauty of this approach is that the sub-metering infrastructure is ridiculously inexpensive if designed at the right time and implemented as part of the electrical distribution network inside NZEB.
- Evaluate and specify the right Energy Management System (EMS) to not only validate the energy performance but also make the energy visible. It is a cliche to say that what is not measured can’t be managed and it is the same for NZEB. These days, EMS comes in different shapes and flavours – from cloud-based to on-site installation with different communication capabilities that can be seen on the web, on the tablets or on your smart phones. The trick is the remember and enforce that measurement and verification is done best by the energy management system and not by a Building Management System, which is designed for building controls, not energy management. You don’t use an airplane for traveling 100 KM, then why do you want to do a force-fit by asking your BMS vendor to customize the product for something that it is not designed for in the first place. Once the EMS has been specified, it is critical that the design or Facilities Management team sits down with the EMS provider to lay out the requirements clearly so that the technology platform can provide the data, visualisations and actionable reports in a way that will make the performance validation and corrective action relatively simple.
By adopting the above two principles in the design and performance phase of the NZEB construction, one can tackle the complex issues in a relatively simple and effective manner and reap the rewards of a high performing Net Zero Energy Building.
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