Buildings are Critical to the Global Challenge of Sustainable Development.


The School Building Authority optimized a rooftop repair program with a code-compliant, energy-saving natural interior daylight system that enhanced the school building’s interior environment.

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A significant design element to modernizing the repurposed third floor space was the intelligent use of natural interior daylight at Cornell department of architecture.

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Volvo’s energy reduction success began with a comprehensive plan, including the installation of heat-reflective white roofing and extensive use of natural interior daylight with rooftop skylights.

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Key Facts


For detached single-family homes, the most comprehensive retrofit packages have achieved reductions in total energy use by 50–75%.

Heating and cooling

Heating and cooling energy use in residential and commercial buildings is expected to grow by 79 % and 84 %, respectively, over the period 2010 – 2050.


878 million people with an average 2 USD2010 per day of gross national income (The World Bank, 2013) live in the LDCs group. Rapid economic development, accompanied by urbanization, is propelling large building activity in developing countries

Eneref Roofing Initiative

Here’s how people responded to energy efficiency solutions.

There’s one thing that you don’t want, it’s aggravation and unhappy customers, so you want to sell them a good product. That’s a good product.

Howard Blady - Owner > View Eneref Report

I know about the filters because I’m friends with the custodian, but I don’t know if everyone else knows. It would make them feel like I feel—a little bit safer.

Ieisha Borden - Secretary > View Eneref Report

I think that the construction of the Velux skylights I specified in properties are just phenomenal. Just a beautiful piece of engineering. They're beautifully made… very thoughtful.

Shelley James - Founder > View Eneref Report

We absolutely love the Velux skylights in our artisan house. You can get really nice cross ventilation. You open up those skylights and it brings a gentle breeze right in that flows through the space.

Jeff Julian - Vice President > View Eneref Report

Skylights are not that expensive. It’s a really nice way to add some additional natural light if someone’s interested in feeling more outdoor-indoor.

Sarah Cooper - New Home Sales Consultant > View Eneref Report

We should all have inverter-driven variable speed technology systems because we’d save energy and operating cost, be more comfortable, and reduce our carbon footprint. There’s really no downside.

Bill Goetzler - Navigant Managing Director > View Eneref Report

The school facilities division is implementing a strategic approach to help maintain the health and safety of all building occupants.

John Shea - Chief Executive Officer > View Eneref Report

Skylights add to the room’s aesthetic. Everybody who’s got a sunroom says it’s their favorite room in their house.

Michael Hoy - President and CEO > View Eneref Report

Energy Savings

As buildings are very long-lived and a large proportion of the total building stock existing today will still exist in 2050 in developed countries, retrofitting the existing stock is key to a low-emission building sector. Numerous case studies of individual retrofit projects (in which measures, savings, and costs are documented) are reviewed in Harvey (2013), but a few broad generalizations are:

(1) For detached singlefamily homes, the most comprehensive retrofit packages have achieved reductions in total energy use by 50–75%;

(2) in multi-family housing (such as apartment blocks), a number of projects have achieved reductions in space heating requirements by 80–90%, approaching, in many cases, the Passive House standard for new buildings;

(3) relatively modest envelope upgrades to multi-family housing in developing countries such as China have achieved reductions in cooling energy use by about one-third to one-half, and reductions in heating energy use by two-thirds;

(4) in commercial buildings, savings in total HVAC energy use achieved through upgrades to equipment and control systems, but without changing the building envelope, are typically on the order of 25–50%;

(5) eventual re-cladding of building façades—especially when the existing façade is largely glass with a high solar heat gain coefficient, no external shading, and no provision for passive ventilation, and cooling—offers an opportunity for yet further significant savings in HVAC energy use; and

(6) lighting retrofits of commercial buildings in the early 2000s typically achieved a 30–60% energy savings. 

Technological Developments

There have been important performance improvements and cost reductions in many relevant technologies, and further significant improvements are expected. Examples include (1) daylighting and electric lighting; (2) household appliances; (3) insulation materials; (4) heat pumps; (5) indirect evaporative cooling to replace chillers in dry climates; (6) fuel cells; (7) advances in digital building automation and control systems; and (8) smart meters and grids as a means of reducing peak demand and accommodating intermittent renewable electricity sources. Many of these measures can individually reduce the relevant specific energy use by half or more. In addition to the new technologies, practitioners have also increasingly applied more established technology and knowledge both in new building construction and in the existing building retrofits.

The metrics of interest are the on-site energy intensity — annual energy use per square meter of building floor area (kWh / m2 / yr) — for those energy uses (heating, cooling, ventilation, and lighting) that naturally increase with the building floor area, and energy use per person for those energy uses — such as service hot water, consumer electronics, appliances, and office equipment — that naturally increase with population or the size of the workforce.

Dehumidification energy use is less amenable to reduction but can be met through solar-powered desiccant dehumidification with minimal non-solar energy requirements. Advanced lighting systems that include daylighting with appropriate controls and sensors, and efficient electric lighting systems (layout, ballasts, luminaires) typically achieve a factor of two reduction in energy intensity compared to typical new systems.  

  1. Does natural interior daylighting on the roofs pay for itself?

    Lighting accounts for roughly one third of electricity used by commercial or educational facilities in the United States. Whereas natural interior daylight requires no energy beyond sunlight. And Natural interior daylight is about 10-times more efficient than rooftop PV cells for lighting a room.

  2. How do students preform under natural interior daylight?

    There is also plenty of evidence that daylighting improves occupant productivity in both schools and offices. Especially in learning environments, skylit classrooms provide a natural and stimulating space for teacher and student. While studies show that poor lighting adversely affects learning, daylighting has been proven to increase student performance in math and reading scores, as well as improving attendance. t button to change this text.

  3. How do office workers perform under natural interior daylight?

    Studies show that office workers have few sick days. The human performance numbers in daylighting systems are important because the ROI for daylighting installations can sometimes be a difficult sell. In fact, the human performance gains can outweigh the energy savings, where human performance can be measured in financial terms.

  4. Sustainable buildings reduce 80% carbon foot print

    According to Buildings Commissioner Rick Chandler, small steps towards designing more sustainable buildings can make a big dent in the City’s carbon footprint – reducing emissions as well as energy bills. Through expanded benchmarking Mayor de Blasio’s vision of reducing 80 percent of our carbon emissions by 2050 might be realized.

Portrait of senior black man in eyeglasses with serious expression.  Horizontal shot.
Cool Room Cool Earth Campaign

“I would hope we would all have inverter-driven variable speed technology systems because we’d save energy and operating cost.”

FAQ: Why don't we see more natural interior daylight in buildings today?

Eneref Institute has identified seven primary reasons we don’t see more natural interior daylight in our buildings. To learn the seven market obstacles to daylighting, download Eneref Institute’s report.