Aerogel Insulated Double-Glazed Windows

Summary

Aerogel Insulated Double-Glazed Windows

Double-pane Window Glazing: Translucent Aerogel Insulation vs. Conventional Double-Glazed Vinyl Frame Window

A transluscent or opaque material with an insulating value up to R-20 per inch that can be used in windows, skylights, and walls (Aerogel, Kalwall).

Synopsis:

Silica-based aerogels have low thermal conductivity (high R values), are light weight, and can be sandwiched between sheets of glass or plastic to provide "superinsulating" glazing. This glazing can be used in existing and new residential and commercial buildings. Aerogel glazing is now becoming available in the insulation market.

Aerogels thermal properties can offer R-values of 14 to 105 for 3.5 inch thick bat depending on the structure. By comparison, typical fiberglass or cellulose wall insulation has an R-Value of 3 for a 3.5 inch thickness. A half-inch of aerogel has about the same insulating properties of three inches of fiberglass insulation.

Aerogels are now available in skylights, double glazed windows and translucent wall and roofing materials. Translucent wall and roofing material achieves an R-value of 20---equivalent to a solid wall and four times greater than insulated glass units. R-10 per inch aerogel insulated double glazed windows have no inert gases to leak out, are lighter than triple glazed window units, and provide better light transmittance without requiring low-e coatings. Aerogel filled skylights feature polycarbonate layers with an aerogel fill and provide an R-value of 4.6, making them up to six times more energy efficient than comparable products.

Aerogels offer superior thermal performance, transmit glare free, full-spectrum light; are moisture resistant, do not support the growth of mold or mildew, are UV stable, reduce sound transmission, and do not degrade in performance over time. Cost is the barrier to widespread market utilization. Aerogel production capacity is small scale at present.

Energy Savings: 83%

Energy Savings Rating: Limited Assessment What's this?

Level	Status	Description
1	Concept not validated	Claims of energy savings may not be credible due to lack of documentation or validation by unbiased experts.
2	Concept validated:	An unbiased expert has validated efficiency concepts through technical review and calculations based on engineering principles.
3	Limited assessment	An unbiased expert has measured technology characteristics and factors of energy use through one or more tests in typical applications with a clear baseline.
4	Extensive assessment	Additional testing in relevant applications and environments has increased knowledge of performance across a broad range of products, applications, and system conditions.
5	Comprehensive analysis	Results of lab and field tests have been used to develop methods for reliable prediction of performance across the range of intended applications.
6	Approved measure	Protocols for technology application are established and approved.

Simple Payback, New Construction (years): 35.6 What's this?

Simple Payback, Retrofit (years): 42.8 What's this?

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:

Simple Payback = Incremental First Cost / Annual Savings

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.

Details

Aerogel Insulated Double-Glazed Windows

Double-pane Window Glazing: Translucent Aerogel Insulation vs. Conventional Double-Glazed Vinyl Frame Window

A transluscent or opaque material with an insulating value up to R-20 per inch that can be used in windows, skylights, and walls (Aerogel, Kalwall).

Item ID: 290

Sector: Residential, Commercial

Energy System: Building Envelope--Windows & Skylights

Technical Advisory Group: 2014 Commercial Building TAG (#9)
Average TAG Rating: 3.26 out of 5
TAG Ranking Date: 03/17/2014
TAG Rating Commentary:

Several variants in the market with different properties. Important to sort out the particular application and its needs. Cost is an issue. Need to predict performance for the specific cases of interest
Excellent technology for non-view fenestration. Beautiful distribution of high quality sunlight with high thermal resistance. Best for top daylighting through skylights, clerestories and atria. Can also work with vertical windows at levels above and sometimes below view apertures.
These technologies do not provide the quality of daylighting that you would want to support, given the glare that results from a bright translucent or opaque surface. If people want a translucent glass, these kinds of panels provide improved insulation, but in the grand scheme of things, this is not a significant gain in EE.

Synopsis:

Baseline Example:

Baseline Description: Residential single-glazed window
Baseline Energy Use: 42 kWh per year per square foot of glazing

Comments:

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 gains because of solar heat gain and supplemental heat (wood, etc.), and additional losses due to infiltration, and losses through the window, in the case of a forced air furnace, will be supplied by a furnace with some losses to the outside at the furnace and through the ducts. In an attempt to account for those differences, we make the simplifying assumption that these factors essentially cancel each other out, so we use the calculated value of 42 kWh/sf/yr. (Note: this is per square foot of single-glazed window area).

Manufacturer's Energy Savings Claims: Currently no data available.

Best Estimate of Energy Savings:

"Typical" Savings: 83%
Energy Savings Reliability: 3 - Limited Assessment

Comments:

Use of R10 per inch aerogel in windows results in an overall R-value of R6. This provides an 83% savings relative to an R1 single-pane window.

Energy Use of Emerging Technology:

7.1 kWh per square foot of glazing per year What's this?

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.))

Technical Potential:
Units: square foot of glazing
Potential number of units replaced by this technology: 22,000,000
Comments:

Residential

We can only count in the technical potential of those homes currently heated by electrical appliances. We assume that aerogel-filled 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. 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). Note: Aerogel-filled windows can also be used in the commercial sector (particularly the small businesses). Note that aerogel-filled windows will also provide a substantial savings over double pane windows in either residential or commercial applications. Large commercial buildings tend to be cooling-dominated and utilize a 1/2-inch thick single layer of glazing that is often tinted for limiting solar heat gain.

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:
0.77 TWh per year
88 aMW
What's this?

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)

First Cost:

Installed first cost per: square foot of glazing
Emerging Technology Unit Cost (Equipment Only): $134.16
Emerging Technology Installation Cost (Labor, Disposal, Etc.): $0.01
Baseline Technology Unit Cost (Equipment Only): $22.36

Comments:

Riffat and Qui, in "A Review of State-of-the-Art Aerogel Applications in Buildings" (Int'l Journal of Low-Carbon Technologies, April 20, 2012) state that aerogels are still relatively expensive, with the cost of an aerogel window six times that of a conventional double-glazed window. The reference that they extracted this information from, however, is somewhat dated. Aerogel is a technology that is still hoping for a reduction in unit costs given large-scale manufacturing. That is unlikely to occur, however, until aerogel products achieve cost competitiveness with conventional products. The material cost of a conventional insulation material is about 10 times lower for the same thermal resistance. In a niche application, Thermoblok offers 1-1/2″ wide strips, which are used to cover framing studs and help prevent thermal bridging. The cost is about $1.99/ft.

For lack of better information, we will assume six times the cost of a conventional double-pane window. HomeWyse indicates that the cost of a 42 in x 48 in window is $261 to $365 (equipment only) with a midpoint of $22.36/sf. Six times this value is $134.16/sf.

Cost Effectiveness:

Simple payback, new construction (years): 35.6

Simple payback, retrofit (years): 42.8

What's this?

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.

Reference and Citations:

NEEA, 01/01/2014. Total Pacific Northwest Building Stock Based on Preliminary Numbers from the 2013 Update to the CBSA
Northwest Energy Efficiency Alliance

CADMUS, 12/21/2009. Northwest Commercial Building Stock Assessment (CBSA): Final Report
Prepared by the CADMUS Group for the Northwest Energy Efficiency Alliance

University of Minnesota , 01/01/2011. Windows for high-performance commercial buildings
University of Minnesota

Douglas Page, 01/01/1998. Aerogels: Much Ado About 'Nothing'
High Technology Careers Magazine

Jeffery Kahn, 01/01/1991. Aerogel Research at LBL: From the Lab to the Marketplace
Lawrence Berkeley National Laboratory

Aspen Aerogels , 10/28/2003. Highly Insulating Windows With a U-Value Less than 0.6 W/m2K
Aspen Aerogels

K.I. Jensen, 10/01/2004. Development of windows based on highly insulating aerogel glazings
Technical University of Denmark

Arlon Hunt, 01/01/1995. Aerogel: Energy-Efficient Material for Buildings
Center for Building Sciences Newsletter

Steve Roy, 03/06/1997. NASA Research in Space May Redesign Household Windows
NASA

Saffa Riffat, 12/29/2011. A review of state-of-the-art aerogel applications in buildings
International Journal of Low-Carbon Technologies

Mick Skolnick, 09/04/2008. Breakthrough Aerogel 37x Better than Fiberglass
ecogeek.org

Reuben Baetens, 04/01/2011. Aerogel Insulation for Building Applications: A State-of-the Art Review
Energy and Buildings , 43

Rank & Scores

Aerogel Insulated Double-Glazed Windows

2014 Commercial Building TAG (#9)

Technical Advisory Group: 2014 Commercial Building TAG (#9)
TAG Ranking: 5 out of 44 Technologies (2014 Commercial TAG strategies ranked separately)
Average TAG Rating: 3.26 out of 5
TAG Ranking Date: 03/17/2014
TAG Rating Commentary:

Several variants in the market with different properties. Important to sort out the particular application and its needs. Cost is an issue. Need to predict performance for the specific cases of interest
Excellent technology for non-view fenestration. Beautiful distribution of high quality sunlight with high thermal resistance. Best for top daylighting through skylights, clerestories and atria. Can also work with vertical windows at levels above and sometimes below view apertures.
These technologies do not provide the quality of daylighting that you would want to support, given the glare that results from a bright translucent or opaque surface. If people want a translucent glass, these kinds of panels provide improved insulation, but in the grand scheme of things, this is not a significant gain in EE.