Interior Automated Window Shades
Window Shade Control: Automated vs. Manual
Interior window shades controlled by an automated system in response to available sunlight and need for controlling solar heat gain and glare.
Item ID: 538
Building Envelope--Windows & Skylights
Technical Advisory Group: 2014 Commercial Building TAG (#9)
Average TAG Rating: 2.63 out of 5
TAG Ranking Date: 03/17/2014
TAG Rating Commentary:
- Only in combination with dimming lighting controls
- Widely used in Europe; overdue in US; lots of technical options but some integration challenges and cost challenges
- This is a subcategory of the automated dynamic daylighting systems, mentioned above.
- Variants of this technology already on the market but quite expensive.
- I have seen these are generally manually overridden. Hence the energy savings may not be as expected.
Multiple companies are offering wireless remotes, wall switches, and Apple mobile devices that can activate motorized lifting systems to raise or lower shades or to tilt the slats of blinds. The devices can be programmed to control single window coverings or groups of shades with the touch of a button.
Managing window blinds can keep your house cool in the summer and lower your energy bill. In the summer, closing highly reflective blinds can prevent solar heat gain by as much as 45% and reduce heat transfer through windows. In the winter, properly used window treatments can help keep cold air out and warm air in. As a result, both heating and cooling bills can be reduced. As part of a home energy automation system, blinds or shades can be equipped with a lighting sensor to automatically open during the day and close at night. An add-on temperature sensor can close blinds and shades during the day depending upon ambient temperature readings. Another option is to include a motion sensor so you can adjust them to provide a view with a wave of your hand. The motorized driver is so small that it can fit inside the header at the top of the blinds, rendering it effectively invisible.
Many energy-efficient window covers have insulating values equivalent to R-2 to R-4. Honeycomb shades can have an R-value up to 5 although some manufacturers claim R-7 to R-8. These shades and blinds can double the insulating value of a standard vinyl frame window with double-pane glazing and a Low-E coating (McNutt, HouseLogic, "Guide to Energy Efficient Window Coverings", January, 2010).
Baseline Description: Single pane, clear window in metal or wood frame
Baseline Energy Use: 21 kWh per year per sf of glass
To estimate the electrical energy use of a square foot of single-pane glass in a window in a building in the Northwest, we use the traditional heat-loss equation of
H = UAxHDDx24. In this case:
- U = A = 1
- Typical HDD (heating degree days) in the Northwest is 6000
So heat loss (H) = 144 kBtu/sf/yr = 42 kWh/sf/yr
There will be heating system benefits due to reduced infiltration, and cooling system benefits or losses due to increased or decreased solar gain through the window. Houses are heated by a mix of electric baseboard, heat pump, and central forced air furnaces. An average heating system COP of 2.0 will be taken, yielding a heating system loss of 21 kWh/sf-glass/year.
Manufacturer's Energy Savings Claims:
Currently no data available.
Best Estimate of Energy Savings:
"Typical" Savings: 75%
Assume an incremental R-value of 3 due to the installation and proper use of automated shades and blinds. Heat losses through the windows will be reduced by 75% while air conditioning (cooling) loads can be reduced by 45%. Northwest homes are heating dominated, so a savings of 75% of the heat loss through the windows will be assumed (R increases from 1 to 4). Note that the insulating effect of draperies is unknown and neglected.
Energy Use of Emerging Technology:
5.3 kWh per sf of glass 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.))
sf of glass
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 automated shades 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. According to the RBSA, the square footage of glazing is approximately 12% of the floor area. 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 estimated 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 || Avg. sf per Home || Total sf || % Glazing || sf Glazing || % Single-pane || % Storm Windows || sf Potential |
| SF || 4,023,937 || 34.2% || 1,376,186 || 2,006 || 2,760,630,027 || 12% || 331,275,603 ||12% || 10.8% || 4,000,000 |
| MH || 543,730 || 70.1% || 381,155 || 1,280 || 487,878,054 || 12% || 58,545,367 ||20% || 8% || 7,000,000 |
| Total || 4,567,667 || || 1,757,341 || || 3,248,508,081 || || 389,820,970 || || || 11,000,000 |
Source: (Baylon, 2012)
Regional Technical Potential:
0.17 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)
Currently no data available.
Simple payback, new construction (years): N/A
Simple payback, retrofit (years): N/A
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.