To house our growing population, it’s estimated that the world will add 2 trillion square feet of new buildings by 2060 – the equivalent of putting up another New York City every month for the next 40 years. All those buildings consume energy while delivering lighting and comfort from the heat and cold to its occupants. And not even a little bit – the statistics defining building energy consumption are sobering. Buildings account for 36% of all the energy used in the United States and are responsible for generating nearly 40% of all CO2 emissions globally. More than half of this energy is used for heating, cooling, and lighting and is, therefore, a perpetual and accruing problem as we grow our society.
Progressive leaders around the world are developing and implementing strategies to meet the goals of the Paris Climate Agreement. And they are not overlooking buildings in those strategies. In the US, Joe Biden included in his Clean Energy Plan an upgrade of 4 million buildings to make them more energy-efficient.
Improving building energy efficiency is a clear priority in the strategy to curb CO2 emissions and global climate change – but how? Contrary to what a lot of us think, it is not the lights and appliances that are the biggest energy hog in our buildings. It is the heating and cooling of the building that drives energy inefficiency and windows play an outsized role in that equation – 30% of the energy is directly attributable to inefficient windows. It would be more impactful to fix these than to, for example, place solar panels on our building’s roof. In fact, improving window energy efficiency should be viewed with renewable energy as top priorities for human sustainability.
We love our windows and can’t replace them with walls, or we will all go crazy. We pay for them dearly and continuously through electric and gas bills; we wash, drape, and fix them when they break. Why? The reason people want the corner office is not born from the love of right angles, but for the panoramic views those windows provide. Windows give us access to daylight and a connection to the outdoors while we can stay comfortably inside. In fact, we need natural light and a connection with nature to be productive and happy while existing for most of our life indoors.
The same windows also sometimes blind our eyes and make us uncomfortably hot or cold at certain times of the day or year. The most well-known way to keep the sun out are shades and blinds. Shades were invented in large part to manage the amount of natural light coming into a space, mitigate glare and room heating. Shades are effective but block the view, are challenging to maintain, and typically stay down when put down.
The fight with (too much) sunlight has long driven window technology innovation and eventual adoption by a risk-averse and highly evolved building construction industry. Most everyone is familiar with double-paned windows and how they help keep the house warm during the winter and cool in the summer – we see both panes and understand how a thermos works. The use of multi-pane windows to reduce energy lost because of the temperature difference between inside and outside the building is estimated to save 20-30% of heating and cooling costs in comparison to single-pane windows.
Another major step forward is the use of transparent coatings that reflect infrared radiation from the sun, in the industry referred to as low emissivity (Low E) coatings. About half the energy coming through a window not coated with these reflective Low E coatings is from the infrared portion of the solar spectrum and is not visible to the human eye. In this way, we eliminate half of the sun’s energy from heating building interiors while preserving an un-tinted window appearance as shown below.
The path to full implementation of Low E in the window industry began in the 70s with the founding of another Silicon Valley start-up, Southwall. Low E coated glass is now fully deployed and required for code compliance throughout the world. Over time Low E coating technologies have improved in terms of optical appearance in both transmission (initially more yellow than desired) and reflection (uniformity and color control). This combined with ever improving manufacturing processes has enabled full deployment of this technology throughout the world, saving a significant amount of energy.
The other 50% of the energy coming from the sun reaches us in the form of visible light. If we eliminated all of that, it gets dark, you lose the view, and your room turns into a closet. With windows, we get the view, but in the summer the bright sun shining through a clear window heats the room. The AC then removes this heat to maintain a constant room temperature. We not only waste energy pumping this heat out of the building, but we suffer from the discomfort of local heating near windows and high glare conditions at certain times of the day and year.
Our eyes are very sensitive and views during the daytime are preserved even after tinting the window to remove 99.9% of daylight coming in. Tinted windows were invented to manage glare and heat and we saw highly tinted windows become a trend in the 70s to augment energy savings from Low E and double-paned windows. This solved the energy and glare problems but energy consumption for lighting increased and rooms often felt “dreary”.
Electrochromic (EC) windows that can change their tint levels upon demand and for the life of a typical window product have been described as the “holy grail” by veterans in the window industry. The first generation of these products was developed over the last 25 years and are now being installed in commercial buildings globally. The path to full deployment of this technology will require further innovation to improve performance and adapt its products to a broad and evolving market. Implications for building energy efficiency on sustainability are on par with those achieved by Low E glass and the deployment of solar energy. The good news is that EC windows are here: we are at the beginning of the S-curve in innovation – and all with just a fraction of the investment that has been made in the photovoltaics, wind, or other very important renewable energy vectors.
We can expect technological progress and adoption to be rapid and gated by supply, not demand. First, people want it, they always wanted it but now they can get it. Historically, EC has been sold as an alternative to the Low E glass that was specified. Today, with multiple suppliers of EC windows, smart-tinting glass is being specified into projects by leading architects and developers.
In addition to this organic demand, we can expect building codes to get more and more strict, further driving demand for electrochromic products. In fact, Biden’s Clean Energy Plan specifically calls out installing more efficient windows as one of the key solutions to improve energy efficiency of buildings. Electrochromic technologies are even specifically mentioned in the recently published Energy Act of 2020. The pandemic increased awareness for the importance of health and wellness of the buildings we live and work in. As the stars align for the implementation of window innovations that provide health, wellness, and energy savings, we are paving the way for the mass adoption of window technologies that were once only possible in science-fiction movies.
Howard is a co-founder of HALIO, Inc. He was formerly VP R&D at Symyx Technologies where he pioneered the use of combinatorial methods for the discovery and optimization of functional materials. With a Ph.D. from MIT, Howard started his career with Exxon. He has authored more than 60 scientific publications and 100 issued patents.