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Window Attachments: A Simple Way to Achieve Financial and Energy Savings for Your Customers

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Gabe Duarte's picture
Senior Associate D+R International

Mr. Duarte supports the ENERGY STAR® program for appliances by providing research and analysis for ongoing ENERGY STAR specification development efforts. For the past 2 years, he has served as...

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Windows typically make up 30%[1] of a home’s heating and cooling energy. For this reason, energy efficiency measures that deal directly with windows offer huge savings potential for utilities. However, full window replacements are often expensive and not typically a viable measure option.  Utilities are increasingly turning to a new product category to solve the problem of inefficient windows and achieve cost-effective savings: window attachments.

Window attachments are interior and exterior products that are installed over windows in both residential single family, multifamily, and commercial buildings. Interior products are often referred to as window treatments or window fashions and include blinds, shades, drapes, shutters, window quilts, and storm windows. Exterior products include storm windows, roller shades, roller shutters, and awnings. These products are typically overlooked as an energy-saving measure because the primary driver of window attachment purchases is their aesthetic appeal.

In addition to improving the appearance of a home, window attachments can save energy by preventing or blocking the transfer of heat. Using these products can keep homes cooler in the summer and warmer in the winter, providing benefits to consumers in the heating and cooling seasons. Operable window attachments (those that can move up or down, or tilt) also enable more control over the amount of heat and sunlight entering a room, which can help regulate temperature and make the living space more comfortable. In addition to manual operation, many window attachments can be automated to open and close on a specific schedule or by integrating with a smart thermostat or other building controls.

The savings opportunity of different product types will vary based on climate zone and season. The table below estimates the potential energy and cost savings of window attachments. All estimates are based on modeling completed by Lawrence Berkeley National Laboratory (LBNL).

Window Attachment Energy Savings* – LBNL Modeled Estimates[2]

 

U.S. Average Annual Household Energy Savings (kWh) on Single-Pane Window

Product Category

25th Percentile

Median

75th Percentile

$ Savings

Blinds**

1,900

2,400

3,300

$220 - $360

Cellular Shades

2,560

3,150

4,230

$280 - $470

Roller Shades

80

750

1,600

$10 - $180

Solar Screens

-80

970

2,400

$0 - $270

Storm Windows
(Interior and Exterior)

3,300

5,200

8,200

$370 - $910

* These savings numbers represent attachments that are operated manually and do not reflect the savings potential of attachments if automated to achieve optimal savings

** Blinds data includes pricing for vinyl, metal, wood, faux wood, and vertical blinds.

Additional modeling and field studies by LBNL and Pacific Northwest National Laboratory have demonstrated energy efficiency and demand response savings from low-E storm windows, cellular shades, and other window attachment products.

Utilities and program implementers interested in exploring a window attachment energy efficiency pilot or program should consider leveraging the Attachments Energy Rating Council (AERC)’s new residential window attachment certification and labeling program, which provides consumers and utilities with third-party verified energy ratings for window attachments. The AERC was created with funding from the U.S. Department of Energy and is an independent, public interest organization whose mission is to provide consumers with credible, relevant, and comparable information about window attachments and their performance.

AERC offers resources and technical support to utilities interested in learning more about window attachments. To date, AERC has worked with multiple utilities to design and implement window attachment programs, including successful low-emissivity (low-e) storm window programs with Efficiency Vermont and Focus on Energy in Wisconsin. Both pilots resulted in large increases in the overall sale of low-e storm windows compared to the same period of time the year prior (125% year-over-year low-e unit sales increase in Wisconsin and 337% increase in Vermont). Additional utility pilots and programs are in the pipeline for launch in 2020.


[1] AERC (Attachments Energy Rating Council). 2016. Window Attachments: Efficiency Program Brief. Silver Spring, MD: D+R International.

[2] LBNL and D+R International. 2018. New Rating Opening Windows to a World of Comfort, Opportunity, and Cost-Effective Savings. Silver Spring, MD.

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Matt Chester's picture
Matt Chester on Oct 25, 2019

Utilities and program implementers interested in exploring a window attachment energy efficiency pilot or program should consider leveraging the Attachments Energy Rating Council (AERC)’s new residential window attachment certification and labeling program, which provides consumers and utilities with third-party verified energy ratings for window attachments

Glad to see this, the utilities can and should become the trusted energy advisors to customers and demonstrate (and make accessible) the benefits of these types of technologies. 

Have there been any particular challenges of notes by utilities trying to implement this type of program for window attachments? 

Gabe Duarte's picture
Gabe Duarte on Oct 30, 2019

While I don't want to speak for utilities, one of the challenges in implementing window attachment programs I often hear in conversations with utilities is the unfamiliarity with window attachments and their energy savings potential. Since this tecnology is only just beginning to be recognized by utilities, many utilities are hesitant to be "early adopters". For this reason, AERC continues to try and make this process easier for utilities by facilitating window attachment pilot programs, submitting window attachments for inclusion in state Tecnical Reference Manuals (TRMs), and collaborating with National Labs such as LBNL, ORNL, and PNNL on modeling efforts to estimate the energy savings potential of window attachments. The goal is to be able to provide utilities with as much verified energy savings and cost effectiveness data as possible.

Matt Chester's picture
Matt Chester on Oct 30, 2019

Since this tecnology is only just beginning to be recognized by utilities, many utilities are hesitant to be "early adopters"

Seems like a big challenge and a key point-- many customers look to their power providers as trusted energy advisors as well, so if the utility is unsure then that's a huge hurdle for the customer as well!

Thanks for your reply, Gabe. 

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