Reports

Numerous organizations have been involved in research efforts aimed at collecting data and increasing the knowledge base of the characteristics of window attachments and how users interact with them.

The valuable information gleaned from this research is available in the reports located below. These reports are also available for download in PDF format.

Low-E Storms: The Next “Big Thing” in Window Retrofits

September 2014, Pacific Northwest National Laboratory and Birch Point Consulting

Building America, a program focused on energy-efficient building practices, partnered with Pacific Northwest National Laboratory (PNNL) and other industry experts to conduct and compile research on low-E storm windows. The results revealed that low-E storm windows are a cost-effective energy-saving measure. Storm windows were found to cost about one quarter of the price of new windows, offer air sealing, create “dead air space,” reflect radiant heat, and reduce heat loss. Building America’s presentation includes the results of case studies conducted in Chicago, Atlanta, and Philadelphia, weatherization success stories, an overview of how storm windows can aid in code compliance, future opportunities related to storm windows, and the results of PNNL’s lab home research. Finally, the presentation includes resources to learn more about storm windows and their energy-saving potential.

Energy Savings from Window Shades

October 2015, Rocky Mountain Institute

This report evaluates the potential energy savings of automated Hunter Douglas cellular shade products using simulations of representative new and existing houses in seven U.S. cities. The Rocky Mountain Institute (RMI) also analyzed the impact of cellular shades on thermal comfort, potential for HVAC equipment downsizing, and electricity demand reductions. Results show that the evaluated products could save up to 6% of overall home energy use in new homes and up to 17% in existing homes, with the highest energy savings occurring during the cooling season. In addition, simulations estimated that automated cellular shades have the potential to decrease peak electrical demand in new and existing homes by 9% and 15%, respectively. Finally, RMI found that the evaluated products could improve thermal comfort in heating and cooling seasons, and that they had the potential to decrease air conditioning equipment size by 0.5 tons.

Window Attachments: A Call to Action

October 2016, AERC (Updated February 2018)

Aimed at utility programs, this report outlines the energy saving benefits that window attachments provide, the market size for the product category, and the potential impacts of an energy certification program.

Residential Windows and Window Coverings: A Detailed View of the Installed Base and User Behavior

September 2013, D+R International

Sponsored by DOE, this report on the window attachment market included a behavioral study on consumer usage patterns of window attachments.

Low-E Storm Windows: Market Assessment and Pathways to Market Transformation

June 2013, Pacific Northwest National Laboratory

Field studies sponsored by the U.S. Department of Energy (DOE) have shown that the use of low-e storm windows can lead to significant heating and cooling energy savings in residential homes. This study examines the market for low-e storm windows based on market data, case studies, and recent experience with weatherization deployment programs. It uses information from interviews conducted with DOE researchers and industry partners involved in case studies and early deployment efforts related to low-e storm windows. In addition, this study examines potential barriers to market acceptance, assesses the market and energy savings potential, and identifies opportunities to transform the market for low-e storm windows and overcome market adoption barriers.

Global Lighting Performance

January 2015

This Swiss Federal Office for Energy study focused on the use of movable shading devices in offices and their impact on indoor daylighting. The research explored usage patterns, attachment orientation, and the role of automation on the optimal use of sunscreens. The results demonstrate significant energy savings as result of automation.

Modeling Cellular Shades in EnergyPlus

December 2017, Pacific Northwest National Laboratory

This report builds on previous simulation work and field studies evaluating the energy performance of cellular shades by providing additional energy savings estimates for 13 U.S. climate zones. The simulations in this study used a seasonal operation schedule to maximize energy savings, but does not reflect manual use of cellular shades or account for potential added benefits of automation. The study demonstrates that cellular shades can save 10-34% of the energy associated with heating, ventilation, and air conditioning across all included climate zones during the cooling and heating season.

Testing the Performance and Dynamic Control of Energy-Efficient Cellular Shades in the PNNL Lab Homes

August 2018, Pacific Northwest National Laboratory

This report describes the experimental design and results of testing the energy performance of Hunter Douglas double-cell cellular shades under various control schemes in the Pacific Northwest National Laboratory’s (PNNL) Lab Homes in both heating and cooling season experiments. Tests were designed to assess the heating, ventilation, and air conditioning (HVAC) savings resulting from the thermal insulating properties as well as the automated and dynamic control strategies of cellular shades. The report reveals that high-efficiency cellular shades have significant energy-saving potential during the winter heating season if the occupant operates at least some of the larger south- and/or west-facing window shades or uses automated shades. The results for the cooling season show that high-efficiency cellular shades have significant energy-saving potential during the summer cooling season (25% HVAC savings) using a control algorithm and out-perform the typical vinyl Venetian blinds by anywhere between 6% and 15%.

Control Algorithms for Dynamic Windows for Residential Buildings

December 2015, Lawrence Berkeley National Laboratory

This study evaluates the effect of control algorithms for dynamic windows on energy consumption, daylight access, and shade operations in residential buildings. Five different control algorithms were used. The results of the simulations were compared with base cases to evaluate energy consumption in Atlanta, Phoenix, Minneapolis, and Washington, DC. The results of this study show that typical manual operation of shade has on average no effect on site (final) energy consumption in comparison to windows without shade; but the use of automated shading with proposed control algorithms can reduce the site energy by approximately 12% on average. Furthermore, the algorithms used in the study did not result in significantly different energy savings, but there were differences in regard to daylight access.

Field Evaluation of Low-E Storm Windows

December 2007, Ernest Orlando Lawrence Berkeley National Laboratory

Lawrence Berkeley National Laboratory (LBNL) performed a field evaluation comparing the performance of low emissivity (low-E) storm windows with both standard clear storm windows and no storm windows in a cold climate. Six homes with single pane windows were monitored over the period of one heating season to assess the energy use with no storm windows and then again with new storm windows. The baseline data was collected before the storm windows were installed. The storm windows installed on four of the six homes included a hard coat, pyrolytic, low-E coating while the storm windows for the other two homes had traditional clear glass. Overall heating load reduction due to the storm windows was 13% with the clear glass and 21% with the low-E glass. LBNL calculated simple paybacks of 10 years for the clear glass storm windows and 4.5 years for the low-E storm windows.

Evaluation of Cellular Shades in the PNNL Lab Homes

November 2016, Pacific Northwest National Laboratory

This study from the Pacific Northwest National Laboratory (PNNL) examines the energy performance of interior cellular shades through a field evaluation using an identical pair of all-electric, factory-built “Lab Homes.” The Lab Homes are located in International Energy Conservation Code (IECC) climate zone 5, which is a heating dominated climate zone that also experiences hot summers. The study evaluated different operational schedules for their effect on the heating, ventilation, and air conditioning (HVAC) energy use. The results showed that the “optimum” cellular shade operation schedule reduced HVAC energy use over the baseline home by approximately 14% during the heating experimental period and 15% during the cooling experimental period.

Evaluation of Cellular Shades in the PNNL Lab Homes

November 2016, Pacific Northwest National Laboratory

This study from the Pacific Northwest National Laboratory (PNNL) examines the energy performance of interior cellular shades through a field evaluation using an identical pair of all-electric, factory-built “Lab Homes.” The Lab Homes are located in International Energy Conservation Code (IECC) climate zone 5, which is a heating dominated climate zone that also experiences hot summers. The study evaluated different operational schedules for their effect on the heating, ventilation, and air conditioning (HVAC) energy use. The results showed that the “optimum” cellular shade operation schedule reduced HVAC energy use over the baseline home by approximately 14% during the heating experimental period and 15% during the cooling experimental period.

Mind the Gap: Summary of Window Residential Retrofit Solutions

2016, Joseph Petersen, Katherine Cort, Sarah Widder, Pacific Northwest National Laboratory Thomas Culp, Birch Point Consulting, Greg Sullivan, Efficiency Solutions

This paper reviews various window retrofit options, the most recent field test and modeling data regarding their performance and cost-effectiveness, and discuss future rating efforts. This information is useful for utilities and energy-efficiency program managers to help effectively implement incentive measures for these technologies.

Energy Savings from Window Attachments

October 2013, Lawrence Berkeley National Laboratory

This DOE-sponsored study conducted by LBNL used the installed base and user behavior data collected from D+R International’s Residential Windows and Window Coverings report to estimate the energy performance of different window attachment product categories. This modeling study evaluated the thermal and optical properties of eleven window attachments for twelve cities, four residential building types, two HVAC systems, and three baseline window types. The results of the study allowed researchers to make generalizations about the energy performance of window attachments to help demonstrate their energy savings potential.

Saving Windows, Saving Money: Evaluating the Energy Performance of Window Retrofit and Replacement

This study from the National Trust for Historic Preservation builds on previous research and examines multiple window improvements options, comparing the relative energy, carbon, and cost savings of various choices across multiple climate regions. Results of this analysis demonstrate that a number of existing window retrofit strategies come very close to the energy performance of high-performance replacement windows at a fraction of the cost.

Thermal and Optical Properties of Low-E Storm Windows and Panels

July 2015

This study conducted by Pacific Northwest National Laboratory aims to characterize the key energy performance properties of clear and low-e storm windows and panels when installed over different types of primary windows. The study presents the representative U-Factors, solar heat gain coefficients, and visible light transmittance properties of the combined applications of various storm windows over single- and double-pane windows with nonmetal and metal framing. Both fixed and operable windows and panels were evaluated in the study.

Researchers at Architectural Testing, Inc. conducted detailed thermal and optical simulations using WINDOW and THERM software in accordance with National Fenestration Rating Council (NFRC) procedures but also accounting for how storm windows and panels are realistically attached to base windows. The study found that low-e storm panels could reduce U-Factor by 59 – 64% with low-e storm s over single pane windows, and by 43-57% over double pane windows. The authors also noted that storm windows and panels help to reduce air leakage through existing windows, particularly windows that are older.

Database of Low-e Storm Window Energy Performance across U.S. Climate Zones

September 2014, Pacific Northwest National Laboratory

This is an update of a report that describes process, assumptions, and modeling results produced Create a Database of U.S. Climate-Based Analysis for Low-E Storm Windows. The scope of the overall effort is to develop a database of energy savings and cost effectiveness of low-E storm windows in residential homes across a broad range of U.S. climates using the National Energy Audit Tool (NEAT) and RESFEN model calculations. This report includes a summary of the results, NEAT and RESFEN background, methodology, and input assumptions, and an appendix with detailed results and assumptions by climate zone.

Evaluation of Low-E Storm Windows in the PNNL Lab Homes

May 2014, Pacific Northwest National Laboratory

This report describes whole home experimental research conducted in support of the Building America’s Low-e Storm Window Adoption program. The purpose of the project was to evaluate the energy savings potential of installing low-e storm windows over typical double-lane clear aluminum frame windows in the Pacific Northwest National Laboratory’s (PNNL) matched pair of Lab homes.

High Performance Dynamic Shading Solutions for Energy Efficiency and Comfort in Buildings

May 2015

This European Solar Shading Organisation (ES-SO) funded study explored the energy performance of shading systems and their impact on overall building energy performance. The study analyzed thermal and optical properties for numerous combinations of glazing and shading (interior and exterior). The results of this study highlight the impact of solar shading on heating and cooling loads, energy savings, and CO2 reduction potential in European buildings.

Low-E Storm Windows Provide a New Way to Solve the Window Conundrum

December 2015, Efficiency Vermont

This report details a 2015 pilot project by Efficiency Vermont to increase customer awareness and eliminate the incremental price barrier by marking down the price of Low-E glass storm windows to the price of clear glass storm windows at Lowe’s and The Home Depot stores in Vermont. Marketing materials developed for the pilot include stack-outs and other point-of-purchase materials, and Efficiency Vermont reached out on social media to make customers aware of the promotion. Overall storm windows sales increased by more than 37 percent and sales of Low-E storm windows increased by 337 percent during the 2015 pilot period in comparison to the same period in 2014.

Low-E Storm Window Market Expansion Pilot

December 2017, Focus on Energy Wisconsin

This report details the results of the Focus on Energy pilot conducted in the fall of 2017 to assess the potential to generate energy savings from and increase market share of low-emissivity (low-E) storm windows in single-family and multifamily residences in Wisconsin. Eligible Milwaukee-area residents could access a 25% instant discount on low-E storm windows produced by Larson Manufacturing and Quanta Technologies. Larson products were available through big box retailers Menards and The Home Depot, whereas customers could purchase Quanta products directly through the manufacturer. The pilot proved a success by generating a 125% increase in low-E storm window sales compared to 2016. In addition, low-E market share increased during the pilot compared to clear glass storm windows (30% in 2016 to 62% in 2017) and demonstrated higher low-E market share in the treatment region (Milwaukee) compared to the control region (Madison). Based on the pilot results, Focus on Energy launched a statewide low-E storm window retail program in 2018.

Transparent Building Envelope: Windows and Shading Devices Typologies for Energy Efficiency Refurbishments

University of Florence, 2014

Individual window types, interior shading, and exterior attachments were individually assessed for thermal efficiency, noise control, energy use, and natural light transmittance in both residential and commercial settings. The study details several aspects to take into account when considering the installation of shading systems, including the climate location, window orientation, costs of maintenance, building age/surroundings, and specific purposes of the system (e.g. to control solar radiation, glare reduction, acoustic comfort, etc.).

Responsive Shading and Energy Efficiency in Office Buildings: an Australian Case Study

University of Melbourne, 2012

This study assessed the impact of automated venetian blinds (both interior and exterior) on the energy efficiency of typical office buildings in Melbourne and Brisbane, Australia, in comparison to static shading alternatives. By adjusting the blinds to respond to differences in sky clearness, angle of the sun, and orientation of the building façade, the results showed that exterior automated venetian blinds have the highest potential to reduce overall annual energy use, with savings of 27%. The study also assessed the effects of climate and seasonal weather on venetian blinds, and discussed how the choice of venetian blinds can influence space daylighting.

Potential Energy Savings with Exterior Shades in Large Office Buildings and the Impact of Discomfort Glare

Lawrence Berkeley National Laboratory, 2015

Using EnergyPlus software, Lawrence Berkeley National Laboratory modeled the energy efficiency of various exterior shading products in a representative large office building in two climates: hot/cold (Chicago) and hot/humid (Houston). The study outlines the aesthetic, cost, and maintenance advantages/disadvantages of each product type, and evaluated performance both with and without daylighting and glare controls. Results showed that exterior shades could reduce window-related annual energy consumption by 70% without daylighting controls and 86% with daylighting controls in both climates, but that the additional use of glare controls significantly counteracted this reduction, particularly in buildings with very small windows.

Demonstration of Energy Efficient Retrofits for Lighting and Daylighting in New York City Office Buildings

Lawrence Berkeley National Laboratory, Lighting Education & Design, and Building Energy Exchange, 2017

Lawrence Berkeley National Laboratory, Lighting Education & Design, and Building Energy Exchange collaborated to observe the interaction between commercial building occupants and new lighting/shading technology over the course of a year (from 2015-2016). The study was carried out in a 2009 LEED Gold Standard building in New York City, where one floor (dubbed a “Living Lab”) was outfitted with LED lighting, complex lighting controls, and automated, motorized interior shading systems. Results revealed that the automated systems optimized energy savings, indoor environmental quality, and comfort.

Let There Be Daylight: Retrofitting Daylight Controls in NYC Office Buildings

Building Energy Exchange, Green Light New York, 2012

Building Energy Exchange and Green Light New York collaborated on this study of the benefits, challenges, and opportunities associated with implementing new daylighting technologies in existing office spaces in New York City. New York City is an optimal location for transforming the lighting control market due to its high density of office space, relatively small group of building owners and managers who are the primary decision-making parties, and evolving regulations for office light retrofitting and building codes. This report estimates that daylighting technologies have the potential to reduce the annual electricity consumption in New York City office buildings from 5.1 to 2.1 kWh per square foot per year, translating to a total potential reduction of 160 MW of electric demand and 340 GWh of electricity savings. Finally, the report proposes a multi-phase plan to integrate and popularize advanced lighting control systems in commercial office spaces.

Highly Insulating Window Panel Attachment Retrofit

Lawrence Berkeley National Laboratory, Green Proving Ground Program, 2013

To assess thermal insulation performance, single-pane windows of an office building in Provo, Utah, were retrofitted with “triple pane Hi-R panels,” framed window units that significantly increase the thermal insulation of existing windows. The panels were easily installed over existing window frames, and thermal measurements of the retrofitted windows were monitored over a six month period (December-June) to examine performance during both winter and summer months. The window panels significantly increased occupant comfort, saved roughly 11% of total building energy demands, and reduced winter heating demands by 30-40%.

High Performance Dynamic Shading Solutions for Energy Efficiency and Comfort in Buildings

European Solar Shading Organisation, 2015

Exterior shading varieties were evaluated for energy saving and CO2 reduction potential in four different European climates using energy simulations. Results showed that the installation of exterior shading consistently produced energy savings and CO2 reduction, boasting an annual maximum of 30% savings in cooling energy, 14% savings in heating energy, and a carbon emissions reduction of 22% (i.e. 137.5 megatons of CO2). Exterior shading was also shown to have positive effects on occupant thermal comfort and glare reduction.

Effective Daylighting: Evaluating Daylighting Performance in the San Francisco Federal Building from the Perspective of Building Occupants

University of California, Berkeley, 2012

This case study evaluates the occupant experience resulting from modern daylighting strategies implemented in the San Francisco Federal Building. The results show a large disconnect of what were perceived to be effective daylighting techniques by architects, designers, and construction management companies (e.g. increasing window size or incorporating exterior shades) and what is actually experienced by building occupants (visual and thermal discomfort caused by obscured views and/or excessive daylight). The study offers suggestions for future daylighting strategies that more effectively evaluate occupant comfort and health.

Daylighting Case Study: NRG Systems, Hinesburg, VT

Heschong Mahone Group on behalf of the New York State Energy Research & Development Authority, 2011

This case study focuses on a small office building in a temperate climate that uses a very open floor plan with low partitions to allow for higher daylight penetration into the office space. Highly reflective blinds in combination with reflective ceiling and wall designs increase interior daylight levels, while photocontrols help adjust luminaire light output. The overall daylighting system saves 20-30% of lighting energy use, and is generally well-received by building occupants. The study suggests that automated blinds and/or automatic occupancy sensors might offer additional savings.

Daylighting Case Study: Genzyme, Cambridge, MA

Heschong Mahone Group on behalf of the New York State Energy Research & Development Authority, 2011

This case study focuses on a LEED Platinum, 12-story office building that uses a variety of daylighting features to maximize illuminance by natural light. The features include perforated/automated blinds, clear windows and glass walls, photocontrols, occupancy sensors, and dimming controls. The case study found that the overall daylighting system is working efficiently with strongly positive responses from occupants, and saves over 35% of electric lighting energy use per year.

Windows and Offices: A Study of Office Worker Performance and the Indoor Environment

Heschong Mahone Group on behalf of the California Energy Commission, 2003

This case study evaluates the influences of indoor physical environment(s) on officer worker performance, largely focusing on the contributions of windows and daylight. Results indicate that having a better view out of a window, reduced glare potential, improved ventilation, and higher daylight illumination levels resulted in improved office worker productivity, health (both physical and mental), and attention span.

Daylight and Retail Sales Technical Report

Heschong Mahone Group on behalf of the California Energy Commission, 2003

This case study reveals that a major US retailer experienced nearly a 40% increase in sales in stores with increased daylight (via skylights) as opposed to stores with less daylight from 1999 to 2001. Additionally, with the use of photocontrols and other state-of-the-art daylighting techniques, building owners could increase energy savings up to $0.24-0.66/sf, making total profits even higher. Occupant comfort was also reported to be slightly higher with increased daylight.

Shading, Film, and Window Attachment Market Overview

Consortium for Building Energy Innovation, 2016

The Consortium for Building Energy Innovation (CBEI) created a market analysis presentation that describes current and future commercial market trends in the Shading, Film, and Window Attachment (SFWA) industry. The report highlights opportunities for innovation in SFWA technology, discusses initial cost and potential payback timeframes, and also identifies market challenges brought to light by stakeholder survey participation. CBEI also uses stakeholder input to recommend market growth strategies for the U.S. Department of Energy.