The Secret of Extreme Energy Efficiency in Buildings

I was recently asked what is the secret to achieving extremely high efficiency in buildings? It took me a while to think about it, because I have never thought of it as a kind of secret. All the information required to make a building highly energy efficient is already out there.

I even wrote two books on it and have put all my ‘secrets’ there. Anyone can download it for free from here at Downloads – CK at Work, courtesy of the BSEEP (Building Sector Energy Efficiency Project), funded by UNDP, GEF, and JKR in 2012/13.

If I must name one secret to achieve extreme efficiency in a building, it would be hard work, to nail down every opportunity. There are hundreds of opportunities in every building, we just need to hunt it down one by one.

Often, I see energy auditors being too focused on the chilled water system. Yes, it is the biggest chunk of energy consumption in tropical climate buildings. But this is not where you start. If you start here, you will lose all the opportunities to cut capital cost because you will be replacing a huge chiller with another huge chiller with a higher efficiency. You may think you have made progress, but this is not enough for a Net Zero future.

A Net Zero future must capitalize on every opportunity for energy efficiency and renewable energy. As mentioned in my previous articles, energy efficiency has the fastest payback. Renewable energy second fastest. Carbon offset has no payback. Energy efficiency and renewable energy will improve our economy because our money is not wasted on fossil fuels or carbon offset (paying someone else to reduce our carbon emission).

To achieve extreme energy efficiency in a building, I recommend starting with passive features first, such as daylight harvesting, infiltration control, insulation, shading, etc. Then move on to active features such as lighting, plug loads, and heat recovery. Done well, I have seen buildings reducing more than 90% lighting power and 90% plug load from these activities. In a new building design, we must also try to maximize daylight harvesting, minimize infiltration, and implement heat recovery.

If the work on passive and active features were done exceptionally well, the cooling load will drop by a minimum of 50%. This is the time to address the cooling system. A low cooling load reduces the peak flow rate requirement from an existing air-conditioning system. Then, on an existing building we must find a way to reduce the fan speed on the air-conditioning system due to a lower cooling load. The existing system, the entire duct and AHU/FCU will be oversized at this point, which is a good thing. Lower flow rates on a big system have much lower pressure losses, reducing fan power significantly. The affinity law dictates that reduction of 50% flow rate will reduce the fan/pump power by ~80%.

After these are done, it is time to replace the entire air-conditioning system with higher efficiency but with smaller fans, pumps, chillers, and cooling towers, thus reducing capital cost of such replacement. Done right, it is cheaper to retrofit a building into Net Zero than to keep business-as-usual approach of changing each equipment one to one whenever a piece of equipment breakdown.

That is, it. It is this simple. There is no secret.

Unfortunately, in an actual environment, each building has its own characteristic and features. This is where the hard work begins, to drill down on all the opportunities offered by different buildings. The concept is the same, but the work to hunt down different opportunities differ from building to building. One building may have more opportunity for daylight harvesting than the other. Another building may have a heating system for water or climate control. Another building may require a solution for their plug load. Thanks to the architects and the people occupying it, every building is unique on its own. They made our world more colorful and created opportunities for engineers to fix.

Therefore, we must have a good understanding of building physics, engineering understanding of all equipment (how each equipment can be tuned and/or selected for high efficiency), and a clear understanding of human behavior. Human behavior is not limited to the building occupant, but also the architects, engineers, and contractors. They often have their own beliefs on energy efficiency that may screw up our intent. For example, we may have reduced the cooling load and flow rate, the engineer then sizes down the ducts and the supplier reduce the size of the AHU, causing high face velocity across the air filters and cooling coil, hence, causing higher pressure losses. Then the system was operated at constant speed by the facility manager. All our previous efforts would have gone down the drain.

In short, all three elements of building physics, engineering, and human behavior, must be satisfied, for it to be successful, or we will fail. My priority is always addressing human behaviors first, then optimize the engineering and physics around it. Just keep in mind that human behavior is beyond building’s occupant, it also involves the entire chain of people during project implementation and operation.

So, what is the secret again? The secret is pure hard work identifying all the possibilities of energy efficiency in a building and the possibilities that it will fail due to human behavior along the chain of implementation and operation.

Good luck and go aggressively on energy efficiency first, and renewable energy second. Lastly, as the final option (and only when absolutely necessary), to spend miniscule amount on carbon offset to achieve Net Zero. I will say it repeatedly, 70-80% reduction of carbon emission on site is achievable if we set our mind to do it. Necessity drives innovation.?