Insulated Cellular Shades
Window Shades: Insulated vs. Conventional
Window shades that incorporate a honeycombed cross section with air-trapping pockets that add an insulating layer to help save energy, with single or multiple cells.
Item ID: 474
Building Envelope--Windows & Skylights
Technical Advisory Group: 2014 Commercial Building TAG (#9)
Average TAG Rating: 2.5 out of 5
TAG Ranking Date: 03/17/2014
TAG Rating Commentary:
- This technology and variants of other insulating shades can be very useful in retrofit situations. Applications details are important. LBNL has recently completed new models to predict performance of most honeycomb products. DOE is funding development of a new agency to rate and certify products using these new LBNL tools; so better selection data and tools are on the way
- I am not familiar with their thermal performance, especially the incremental to double glazing. I am also not familiar with their luminous performance, i.e., their light transmittance. They have the potential to play the same role as the diffuse thermally insulated glazing, which are good, but not for view apertures. Are they only for night use?
- There are many different options for shading depending on building type that offer insulating properties. In general I agree with shading to be used as an insulating option.
- Hard to describe as an emerging technology given how widely available and promoted it already is.
- How new is this?
Technical Advisory Group: 2014 Residential Building TAG (#10)
Average TAG Rating: 2.94 out of 5
TAG Ranking Date: 04/10/2014
TAG Rating Commentary:
Savings will depend on how homeowners use the shades; most effective when used in channels that seal the edges
This is not a new technology. If research findings support solid energy savings, then preparing materials for point of sale support of such shades might help increase uptake.
We tried this 30 years ago and found that air leakage around the insulated shades led to condensation on the windows. It also depends on occupant interaction and the savings would be hard to predict. Better to focus on multiple glazing, low E coatings, insulated spaces, inert gas fill, more efficient frame materials ( no steel reinforced vinyl frames), multi-point locking hardware and better weather stripping. Encourage designers and builders to use larger windows (as opposed to multiple smaller windows) that are square of close to square in shape.
An average of 40% of residential winter heating energy is lost through windows, and small commercial buildings aren't much different. Window treatments have long been used to provide functional and aesthetic additions to existing windows. Exterior shutters, for instance, protect expensive glazing from extreme winds, branches and other storm hazards, and provide an attractive exterior feature. Similarly, drapes provide privacy, can reduce light infiltration, and help reduce winter heat loss when drawn closed.
During the 1970s and the 1980s, efforts were made to explore window treatments specifically as energy-saving devices. One type of window treatment – the insulated cellular shade – differs from traditional blinds in that they incorporate a "honeycomb" or cellular cross-sectional pattern that forms air chambers within the shade. These air chambers provide an insulating effect when the shade is closed. Insulated cellular shades are occasionally installed with side tracks or weather stripping to prevent air from moving through the gaps at the edges of the shade, thus greatly reducing convective heat losses past the shade. Most insulated cellular shades have an "ideal" R-value of between 2 and 4.5. Cellular shades can significantly reduce energy losses through windows during the heating and cooling seasons.
Cellular shades are often chosen by homeowners and commercial building owners and operators to enhance comfort and interior decor rather than to save energy. The median cost of cellular insulating shades is about $10 per square foot. These devices have the potential to reduce residential heating and cooling use by 15% to 22% in western Washington, although simple paybacks exceed 15 years.
Baseline Description: Electrically Heated Home with Single-Pane Glass
Baseline Energy Use: 10087 kWh per year per household
The 2014 NEEA "Residential Building Stock Assessment: Metering Study" indicates that the EUI for the region's houses with electric resistance heating is 17.74 kBtu/sf-year. Electric forced air furnace heated houses use 23.37 kBtu/sf-year while heat pump houses (heating only) use 10.55 kBtu/sf-year (Table ES2, Page xiv). Given that baseboard heaters are used in 12.3% of the housing stock, electric forced air furnaces in 6.1%, and air source heat pumps in 11.4%, the weighted average electrical heating system electrical energy use is about 7.32 + 4.78 + 4.03 = 16.13 kBtu/sf-year. Given a typical house size of 2007 sf, this equates to about 9,485 kWh/year. In addition, the mean region-wide energy use for cooling with central AC is about 0.3 kWh/sf-year or 602 kWh/year. The total annual heating and cooling energy use for electrically heated houses is thus taken as: 10,087 kWh/year. (Use would be higher for homes with single -pane glazing, but we don't have the detailed information to calculate this value).
Manufacturer's Energy Savings Claims:
Currently no data available.
Best Estimate of Energy Savings:
"Typical" Savings: 16%
Low and High Energy Savings: 16% to 22%
The annual energy savings for a retrofit using a single-cell shade on a single-pane, clear glass, wood-frame window (overall R value of 2.76) in western Washington is 1,745 kWh/year, assuming that the shade is operated in an optimal manner. While the annual heating and cooling energy use for the home is reduced by 15.6%, the simple payback is about 15 years.
A retrofit using a double-cell, light-filtering, tracked insulating shade (overall R value of 4.46) on a single-pane, wood-frame window increases the annual energy savings to 2,332 kWh/year. This is about 22% of the annual heating and cooling energy use of the original structure. But this retrofit has a simple payback of 18.7 years due to the increased cost of the high-performance shades.
Side seals are assumed to be added to these cellular shades as they increase the insulating values of the shades by a factor between two and three; from about R-0.91 to R-2.4 (Dodge). The side seals also reduce light leakage around the edges of the shades. Light-blocking cellular shades have significantly greater insulating values than light-filtering shades, although the choice between the two is usually based on color choice and desire for amount of light to penetrate the shades rather than insulating characteristics.
Energy savings are also highly dependent on the shades being correctly deployed at all times (LBNL, 2013). "Correct deployment" in this case varies depending on the specific environmental factors, and changes from day to day and season to season. For example, on a cold but sunny day, shades should be open to allow for passive solar heat gain. On a hot, sunny day, the shades should be drawn to prevent solar heat gain. The correct deployment for any particular situation may be counter-intuitive to a homeowner, or may conflict with other desires (to have the shade open on a sunny day to enjoy the view, for instance). In most cases, it can be assumed that the shades will be correctly deployed during the heating season in the evening and at night, when they are most effective at preventing window heat losses and when homeowners do not mind shutting out external light or views.
Energy savings can also depend on the window where the treatment is applied. Very leaky windows can completely compromise the ability of the shade to provide energy savings. Additionally, the installation of weather stripping for the shades can greatly increase its resistance to convective heat losses and, thus, improve its efficacy as an energy barrier (GBA, 2013).
Because cellular shades are only effective when they are deployed correctly, there is an energy savings risk due to user operating practice. As a result, it is difficult to predict annual energy savings due to the variations in user practices. Many shading system control strategies or combinations of strategies are available for use by homeowners, including:
- Always lowered/deployed (although lighting system energy savings takebacks may occur)
- Always raised or retracted
- Deployed when high solar radiation strikes a window
- Used when outside air temperatures are high
- Used when outside air temperatures are high and sunlight strikes the window
- Used when room or zone temperature is high
- Used when room or zone cooling is in use
- Deployed when glare is high
- Used at night when outdoor temperatures are low
- Used during the daytime when outdoor temperatures are low
- Used at night when heating system is on
- Used during the daytime when the heating system is on
- Always deployed at night
Energy-saving strategies for insulated cellular shades may be tempered in windows with good views (because the owner may want to have them open when it is not optimal to do so) or where other treatments have been built in, such as overhangs, fins, and awnings; and existing windows that incorporate tinting or reflective or low-E film. Savings are reduced when the home or business already has double-pane low-E or triple-pane windows.
Electrical energy savings will not occur in natural gas-heated building that do not have mechanical cooling. Energy savings are greatest in buildings with existing single-pane windows without existing shades or with poorly maintained shades, blinds, or insulated draperies.
Air conditioning savings are greatest in climates with high cooling degree days and in buildings with south- and west-facing glazing with no blockage of solar radiation by adjacent buildings, overhangs, awnings, or vegetation. Cooling savings are strongly dependent on air conditioning equipment performance because seasonal energy efficiency ratios (SEERs) can range from 10 to about 28. Savings are diminished when the cooling equipment is particularly efficient or an economizer is present.
Space-heating savings are greatest in climate zones with high heating degree days and in buildings with electric baseboard heat and electric furnaces. Both heating and cooling savings depend on temperature settings and setbacks.
In addition to user shade deployment strategies, energy savings from installing insulated cellular shades depend on many other variables, including:
- Baseline window (single pane, double pane, Argon filled, triple pane)
- Existence and use of shutters or storm windows (the NEEA Residential Building Stock Assessment indicates that about 10.8% of the region’s homes have storm windows)
- Presence of existing shades or blinds
- Local climate
- Building orientation
- Window-to-wall ratio (in each cardinal direction),
- Presence of shading produced by vegetation, other buildings, overhangs, fins, or awnings
- Building heating and cooling temperature setpoints and setbacks
- Heating and cooling system performance, including use of economizers or operable windows
- Type and performance of HVAC system (natural gas, wood heat, electric baseboard, heat pump, forced-air electric)
Energy Use of Emerging Technology:
8,473.1 kWh per household per year
Energy Use of an Emerging Technology is based upon the following algorithm.
Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Potential number of units replaced by this technology:
We can only count in the technical potential of those homes currently heated by electrical appliances. We assume that indoor storm windows will get minimal penetration in the multifamily market in the foreseeable future. According to estimates in the Northwest Energy Efficiency Alliance's (NEEA's) 2011 Residential Building Stock Assessment (RBSA), 34.2% of single-family homes and 70.1% of manufactured homes in the Northwest are heated with electricity (Baylon, 2012 Pg 53, Table 51). We make the simplifying assumption that electrically-heated homes are the same average size as each category of home with all heating sources, so to get an estimate of square footage, we multiply the total square footage of each type of home times the percentage of homes that are electrically heated in that category. Also according to the RBSA, about 12% of glazing is single-pane, but 10.8% of homes have storm windows. Assuming that most of the storm windows are on homes with single-pane glazing, that leaves only 1.2% of single-family homes with single pane and no storm windows. The corresponding numbers for manufactured homes are not available, so we estimate by the given numbers (20% single-pane and 8% with storm windows).
Square Footage of Single-Pane Glazing in Electrically-Heated Homes
| Type Home || Homes || % Electric Heat || Electrically-Heated Homes || % Single-pane || % Storm Windows || Total Number of Homes || || || || |
| SF || 4,023,937 || 34.2% || 1,376,186 || 12% || 10.8% || 16,514 || || || || |
| MH || 543,730 || 70.1% || 381,155 || 20% || 8% || 45,739 || || || || |
| Total || 4,567,667 || || 1,757,341 || || || 62,253 || || || || |
Source: (Baylon, 2012)
Regional Technical Potential:
0.10 TWh per year
Regional Technical Potential of an Emerging Technology is calculated as follows:
Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)
Installed first cost per: household
Emerging Technology Unit Cost (Equipment Only): $2875.00
Emerging Technology Installation Cost (Labor, Disposal, Etc.): $0.01
Baseline Technology Unit Cost (Equipment Only): $0.00
The median price of an insulated shade $9.58 per square foot, though the prices range from as low as $1 per square foot to as high as $60 per square foot. Insulated cellular blinds can generally be measured, ordered, and installed by homeowners, though professional help is commonly needed to ensure proper fit and installation, which can add to the cost of the measure. Insulated shades can be ordered over the Internet, thus avoiding dealer markup and sales tax in some locations. With a total window area assumed to be 300 square feet, the costs of adding insulated shades to a home are about $2,875.
Insulated cellular blinds can generally be measured, ordered, and installed by homeowners, though professional help is commonly needed to ensure proper fit and installation, which can add to the cost of the measure. Specialty features such as wireless controls, custom graphics or weather stripping also add additional cost (though, in the case of weather stripping, this can also increase the performance of the measure). Installed costs are provided per square foot of window area.
Average installed costs for the Symphony brand single cell and tracked double cell light filter shades analyzed are $6.96 and $11.64 per square foot, respectively. Insulated shades can be ordered over the Internet, thus avoiding dealer markup and sales tax in some locations.
Simple payback, new construction (years): 19.8
Simple payback, retrofit (years): 19.8
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.
Simple paybacks for a retrofit using cellular insulated shades are determined by dividing the total cost of the shade by the value of the energy savings assuming a typical utility residential sector energy rate of $0.08/kWh. The total window area is assumed to be 300 square feet. Average installed costs for the Symphony brand single-cell and tracked double-cell light filtering shades that were analyzed are $6.96 and $11.64 per square foot, respectively.
Shade costs are based on direct order over the Internet (thus avoiding dealer markup and sales tax in some locations) and homeowner installation. Energy savings would increase given the use of a baseboard electric heating system and greatly decrease if the shades were installed in conjunction with energy code-compliant housing or onto existing metal- or vinyl-framed double-pane windows.
Insulated cellular Window Shades are a relatively recent addition to the many window treatment options available in the residential and small commercial sectors. They can be used as a retrofit technology, or specified in new residential or commercial construction. They fulfill the basic functionality of all shading devices by providing privacy and through reducing and diffusing incoming exterior light. Insulated cellular shades can also be raised and lowered by the user, allowing for the window to be either covered or uncovered as desired. Insulated cellular shades differ from more traditional blinds in that their cross section incorporates a "honeycomb" or "cellular" pattern which forms air chambers within the shade. These air chambers serve to provide an insulating effect when the shade is in the closed position. More recently, some Insulated cellular shades are designed to be installed with side tracks or weather strips which prevent air from moving through the gaps at the edges of the cellular shade, thus greatly reducing convective heat losses past the shade.
Insulated cellular shades differ from more traditional blinds in that their cross section incorporates a "honeycomb" or cellular pattern that forms air chambers within the shade. These air chambers produce an insulating effect when the shade is closed. Recently, insulated cellular shades have been installed with side tracks or weather stripping to prevent air from moving through the gaps at the edges of the cellular shade, thus greatly reducing convective heat losses.
Most insulating cellular shades have an "ideal" R-value (the measure of the resistance of the material to conductive heat transfer) of between 2 and 4.5. The shades also reduce the Solar Heat Gain Coefficient (SHGC) of the combined window/shade system by between 60% and 80%, depending on the shade and the baseline window (Mattingson, 2002). These values affect energy losses in multiple ways. The R-value of the shades increases the overall insulating values of the window/shade system, which reduces heat losses in the cooling season and decreases conductive heat gains during the summer. The decrease of the window/shade system SHGC also reduces the radiant heat gain during the summer months. These effects significantly reduce energy losses through the window.
Insulated cellular shades are now widely available and are sold at window covering specialty shops, window suppliers, floor and interior stores; through decorators; and at major outlets like Home Depot. Major insulated shade manufacturers include: Laura Ashley, Graber, Levolor, Blinds.com, Bali, Norman, Lutron, Comfortex, Symphony, Serena, Hunter Douglas, and YourBlinds.
Generic performance of different kinds of shades are typical as in the following table:
| Table 1. Compare R-Value by Fabric Type |
| ||Shade Only ||Single Pane |
|Double Pane |
|Triple Pane |
|Double Cell Light-Filtering || 2.8 ||3.8 ||4.6 || 6.3 |
|Double Cell Light-Filtering with Tracks || 3.3 ||4.3 ||5.1 ||6.8 |
|Double Cell Black Out || 4.0 ||5.0 ||5.8 ||7.5 |
|Double Cell Black Out with Tracks || 4.7 ||5.7 ||6.5 ||8.2 |
|Single Cell Light-Filtering ||1.6 ||2.6 ||3.4 ||5.1 |
|Single Cell Black Out || 2.5 ||3.5 ||4.3 ||6 |
Note: Single cell shades are not available
with side tracks
| || || |
A wide variety of window treatments are available, many of which can provide privacy, shading and light diffusion. Most window treatments sold are blinds, including Roman, Venetian and mini blinds. A smaller – but still significant – portion of sales are of shades, including exterior solar shades, pleated shades and other varieties (Barrett, 2012). Most installed window treatments are designed primarily for aesthetics and privacy, not as energy-saving measures, though many window treatments do provide modest energy benefits, including reducing solar heat gain and some insulating benefits (LBNL, 2013). It is also standard for windows to have no treatment at all, which is the baseline condition used for energy savings calculations.
Insulated cellular shades were first developed by Hunter Douglas, one of the largest manufacturers of window treatments in the world. They introduced the Duette honeycomb shade in 1985, in response to the energy crisis of the 1970s (HunterDouglas, 2013). The honeycomb shade was specifically designed to fulfill the traditional aesthetic and privacy roles of a window shade, as well as to effectively reduce energy losses through the window.
In recent years, companies have further innovated the basic design by adding additional layers of cells; current product selections include single-, double-, and triple-layered shades. Additionally, new materials, such as mylar or aluminum, are used to line the insides of "blackout" versions of the shades, further increasing their resistance to heat and air flow.
Most recently, insulating cellular shades have been designed for use with "side tracks" such as the Gordons EcoSmart shades with ComforTracks (Gordons, 2013). The shade, with side tracks, was shown to have an effective R-value much higher than the same shade without side tracks, suggesting that the tracks effectively reduced convective heat losses around the edges of the shade (GBA, 2013).
Vendors are also offering automatically operated insulated cellular shades, which have an integrated, battery-powered motor to raise and lower the covering (Lutron, 2012). These automated shades can be operated by remote control and can be integrated into a home energy management system in which the shades are raised and lowered in response to environmental conditions to maximize energy savings.
Permits are not required to install insulated cellular shades. Codes, standards, and regulations do not require or prohibit this technology. Additional information is available through the Window Coverings Association of America, http://www.wcaa.org/.
Insulating cellular shades provide benefits that are very comparable to traditional window treatments that are not designed to save energy. These include light-level reduction, improved comfort, enhanced privacy, elimination of glare, and reduction of hot spots within a residence due to solar heat gain.
Because aesthetics, design, and fabric quality are of great importance to homeowners when selecting window treatments, insulating cellular shades are available in a wide variety of styles and colors, and can also be purchased with custom graphics and patterns from certain vendors (Gordon's, 2013). Honeycomb shades admit diffused light when drawn, but they do obscure the outside view.
High tech efficiency approaches are sometimes selected by innovators due to their “cool” factor.
End User Drawbacks:
Insulating cellular shades are generally more expensive than window treatments such as traditional Venetian blinds or curtains. And unlike treatments such as Venetian blinds, cellular shades – when deployed – completely block the view through the window (though only some varieties block the light). They can also be difficult for the owner to clean, given their unique construction and geometry. Finally, insulating cellular shades can crease, and these creases may be difficult or impossible to remove.
Operations and Maintenance Costs:
O&M costs are relatively minor and include periodic repair of worn draw cords. Cellular shades are a passive technology with simple and robust components. Depending on material and quality, periodic cleaning in place with a mild detergent might be recommended.
Most manufacturers offer limited lifetime warranties for any defects or failures in the mechanisms of the shades. Various sources indicate that cellular shades have an "extremely long" life cycle and are considered to be environmentally conscientious devices because of their energy savings and because their durability keeps them out of the landfill for many years.
While shades generally have a useful life of 15 years, the life of cellular shades could be reduced by wear or by the desire for an aesthetic change during a remodel or home sale. Shades can be replaced by drapes, blinds or shades with a more pleasing or different appearance.
Virtually any window treatment might be considered to be a competing technology to cellular shades. This includes external shades; internal, non-insulated shades; and blinds of all varieties. Many window treatments provide some reduction of solar heat gain and insulating benefit to varying degrees (LBNL, 2013).
Additional technologies that are available include advanced windows (double- and triple-pane, Argon-filled, Low-E); reflective, spectrally selective, or low emissivity window film retrofits; awnings or shutters; and insulated window panels. Future technology and cost breakthroughs may occur in the areas of battery-driven automated shades tied into a building energy management system, dynamic glass (equipped with electrochromic window film that is capable of transitioning between clear and variable tint states to control light, heat and UV rays), and superinsulated windows (perhaps with an aerogel fill). At this time, none of these competing technologies is cost-effective in the Pacific Northwest (although insulated window panels have not yet been assessed). High-tech efficiency approaches are sometimes selected by innovators due to their “cool” factor.
Reference and Citations:
What Should I Do About My Windows?
Provides a summary of various window treatments, including a table of U-value and SHGC for treatments.
Window Coverings and Attachments
Provides an overview of the various window treatments which might be used as efficiency measures, and discusses their characteristics.
Guest Blogs: Insulating Window Shades
Discusses R-values of cellular shades, as well as the efficacy of weather stripping for shades.
Blind and Shade Industry Snapshot
Discussion of market penetration of various types of window treatments.
About Us - A History of Innovation
Discusses the origins of the Insulating Cellular Shade by Hunter Douglas.
ComforTrack Plus: Energy Saving Side Track System
Vendor site for airsealing side tracks.
Persona™ Custom Graphics Cellular and Roller Shades
Comfortex Window Fashions
Vendor site for custom graphic cellular shades.
Sivoia® QS Triathlon® Shading Solutions
Vendor source for automated, wirelessly controlled shades.
Thermal Insulating Value of Cellular Shades with and without Side Seals