An insulated glazing unit (IGU) installed inside existing commercial building glazing that can triple its insulation value and reduce infiltration and outside noise at roughly half the cost of window replacement.
High performance secondary glazing units (also known as insulated glazing units, IGU) for commercial building single-pane retrofits that are installed on the interior side without replacing the existing glass, window frames, or altering the exterior appearance of the building. Annual total building energy savings can be up to 20% - primarily due to minimizing exterior solar heat gain loads and exterior air infiltration. Also increases occupant comfort thermally, visually, and acoustically in existing commercial buildings with single pane windows. Installation time is 2-3 times faster than a full window replacement--and much cheaper. The ideal application is existing buildings greater than 50,000 square feet with low-performance single pane windows in thermally unbroken metal frames constructed before 1990’s. (Curry, Pg 14-22).
Design considerations include fogging and seismic stability.
Simple Payback is one tool used to estimate the cost-effectiveness of a proposed investment, such as the investment in an energy efficient technology. Simple payback indicates how many years it will take for the initial investment to "pay itself back." The basic formula for calculating a simple payback is:
The Incremental Cost is determined by subtracting the Baseline First Cost from the Measure First Cost.
For New Construction, the Baseline First Cost is the cost to purchase the standard practice technology. The Measure First Cost is the cost of the alternative, more energy efficienct technology. Installation costs are not included, as it is assumed that installation costs are approximately the same for the Baseline and the Emerging Technology.
For Retrofit scenarios, the Baseline First Cost is $0, since the baseline scenario is to leave the existing equipment in place. The Emerging Technology First Cost is the Measure First Cost plus Installation Cost (the cost of the replacement technology, plus the labor cost to install it). Retrofit scenarios generally have a higher First Cost and longer Simple Paybacks than New Construction scenarios.
Simple Paybacks are called "simple" because they do not include details such as the time value of money or inflation, and often do not include operations and maintenance (O&M) costs or end-of-life disposal costs. However, they can still provide a powerful tool for a quick assessment of a proposed measure. These paybacks are rough estimates based upon best available data, and should be treated with caution. For major financial decisions, it is suggested that a full Lifecycle Cost Analysis be performed which includes the unique details of your situation.
The energy savings estimates are based upon an electric rate of $.09/kWh, and are calculated by comparing the range of estimated energy savings to the baseline energy use. For most technologies, this results in "Typical," "Fast" and "Slow" payback estimates, corresponding with the "Typical," "High" and "Low" estimates of energy savings, respectively.
Status:
Baseline Description: Baseline Energy Use: 19.9 kWh per year per square foot
Buildings with electric heating and cooling systems have an EUI of 19.9 kWh/sf-year (Table D-EA5).
"Typical" Savings: 20% Energy Savings Reliability: 2 - Concept validated
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.))
The 2009 NEEA "Northwest Commercial Building Stock Assessment" indicates that 27.9% of the windows in commercial buildings have a single glazing layer (Table 12, Page 31). Schools have a higher percentage (46.7%) while office space is lower (22.5%). We also know that 27.1% of the regional floor area is heated by electricity (Table C-GB13). Buildings with electric heating and cooling systems have an EUI of 19.9 kWh/sf-year (Table D-EA5). Given a regional commercial building floor space of 2,704 million sf, the area that would be expected to have single-pane glazing with electric heating and cooling is about: 2,704,000,000 x (0.279) x ((0.271) = 204,446,736 sf.
This is from a presentation given by Rob Curry at the Northwest Energy Efficiency Alliance given April 16, 2014, for the E3T Commercial Technical Advisory Committee (TAG). (Curry, 2014 Pg 14)
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: square foot Emerging Technology Unit Cost (Equipment Only): $10.00 Emerging Technology Installation Cost (Labor, Disposal, Etc.): $0.01 Baseline Technology Unit Cost (Equipment Only): $0.00
The total installed cost, as per a presentation by Rob Curry at NEEA (Curry, 2014 Pg 16), is $40 per square foot of glazing area. The comparison is against no investment. Building energy use and savings percentage are expressed in terms of building floor area, not window area. It will be assumed that the glazing area represents 25% of the floor area. When expressed is terms of cost per square foot of floor area, the technology unit cost is $10/sf.
Simple payback, new construction (years): 27.9
Simple payback, retrofit (years): 27.9
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.
Rob Curry, 04/16/2014. Secondary Glazing Systems for Installation in Commercial Buildings Northwest Energy Efficiency Alliance Special Notes: This was a presentation delivered to the members of the E3T Commercial Buildings Technical Advisory Committee on April 16, 2014
Technical Advisory Group: 2014 Commercial Building TAG (#9) TAG Ranking: Average TAG Rating: TAG Ranking Date: TAG Rating Commentary: