- Future Windows: A View to 2050
July 19, 2018
Future Windows: A View to 2050
In a presentation at the June AAMA Western Region Summer Summit, Stephen Selkowitz, recently retired from Lawrence Berkeley National Laboratory (LBNL), put forward his vision for a “net zero building envelope,” by moving the energy impact of a building’s façade from today’s net loss to zero and then to net positive. Selkowitz sees this as a challenging concept, but one that means new business opportunities, greater occupant benefits and increased value in the real estate market as well as very large energy and cost savings.
In 2005, California set ambitious greenhouse gas (GHG) reduction targets to eventually reduce use to 20 percent of 1990 levels by 2050. This was to be achieved by 1) reductions in energy needs based on lifestyle changes (more walking/cycling, recycling, etc.), 2) use of more efficient products (e.g., LED light bulbs, better windows) and 3) using more “decarbonized” sources (wind, solar, biofuels). All new residential construction would be “net zero energy” (ZNE) (producing as much as it uses) by 2020; all new commercial buildings would be ZNE by 2030. Greater energy savings in existing residential and non-residential building stock would also be needed.
The latest round of new 2019 energy standards in California (effective January 1, 2020) in the ZNE quest is that all new California residences now must incorporate solar PV to generate power. Window U value requirements drop slightly from .32 to .30 but there Is now an opportunity for a builder to substitute triple glazing (U = .21) in place of a stringent new wall insulation package. This could represent a big potential increase in sales of triple glazed windows.
Progress is being made in the cost-effective use of renewables. Wind energy has experienced a two-thirds reduction in cost since 2009 while solar energy has experienced an 85 percent reduction over the same period. These costs are now on a par with those of natural gas, and actually less than coal and nuclear. The capacity of photovoltaic (PV) installations in the U.S. rose from 851 gigawatts (GW) in 2010 to 14,626 GW in 2016. Industry is “voting” with their investments on a future based on these renewable sources.
“We can meet the challenge with these new technologies,” Selkowitz asserted. After all, he said “the stone age didn’t end because we ran out of stones.” This implies that the fossil fuel age won’t end because we run out of coal, oil and gas but rather because a better alternative emerges.
Building Integrated Photovoltaic (BIPV) – in essence, using “see-through” solar cells (opaque, semitransparent or clear) in windows – has the potential to turn the building envelope into a power source. This is a big opportunity, but there are numerous technical, design and cost challenges. Who will design, fabricate, sell, install and repair these systems? What will be the role of window companies? Will they be offered as independent systems assembled and integrated on site, or as an integrated package delivered to the job site?
An “intelligent” window or building façade could provide, in addition to the traditional benefits of glare-free daylight, fresh air and enhanced occupant comfort and health, the management of thermal loss or gain, dynamic solar control and power generation through PV.
Selkowitz stated that in addition to traditional insulating and solar control technologies, where potential lies at all levels from the nano (coatings) to the macro (entire building), new dynamic daylight redirecting systems, BIPV and thermal or electric energy storage can be capitalized on. And beyond the high-performance components, integrated and responsive intelligent systems are the key, providing these functions as links to other building systems, such as lighting and HVAC, responsiveness to occupancy and electric grid conditions, and “smart” adaptiveness to changing needs.
Regarding window innovation, the last 30 years has seen the advent of low-e coatings, low-conductance gas fills, “warm edge” spacers and insulating frame systems. There are still a number of new directions to go, Selkowitz affirmed. Some of the emerging insulating technologies are still in more basic R&D like aerogel, but others are already nearing the practical stage, such as vacuum glazings and new configurations of triple or even quadruple glazing, capable of reaching U-factors below 0.10.
Dynamic control of solar gain and daylighting includes choices among or combinations of mechanical shading (interior, exterior or between glass options), passive control using photochromic (light sensitive) or thermochromic (heat sensitive) glazing, or active control using liquid crystal, suspended particle display (SPD) or electrochromic glazing. It involves intelligent control systems that integrate with other building systems. Tests of these systems validating their performance potentials have been underway using room mock-ups at LBNL for many years and there are now 100s of buildings using market-viable smart glazing solutions. But these have not yet reached the adoption and impact levels of low-E glazing technology for a variety of reasons that Selkowitz reviewed.
Of course, part of the challenge in bringing all this to market will be bringing new material technologies on line, forging different supply chain configurations and determining appropriate, cost-effective “packaging” of operational features for different market segments. The complex business landscape that these innovations imply is a challenge. Perhaps an industry coalition is needed to define an open integration platform, data semantics, and other matters, said Selkowitz, to speed adoption of these solutions. Occupant expectations may need tuning, he noted, citing Steve Jobs’ famous observation that “people don’t know what they want until we show them.”
Daylighting as a design strategy has much to recommend it backed by hard evidence as to factors ranging from visual comfort to quantified energy savings. There is growing interest in additional human factors including productivity and wellness advantages, but it is proving very difficult to attribute measurable impact to a specific window design variable. Because of these complexities not all daylighted buildings are actually operated to realize the projected savings. Better design practices are needed, and various studies are underway to better define and promote these new approaches.
In noting some of these challenges Selkowitz remains an enthusiast for the future potentials of window systems and an optimist that they can be achieved, closing by reiterating an earlier admonishment: “Thing Big, Start Small, Act Now.”