Christian Kohler CJKohlerlbl Lawrence Berkeley National Laboratory

1. EWC is a collaborative between Alliance, LBNL, U. Minnesota, and industry, to promote better windows.EWC is a collaborative between Alliance, LBNL, U. Minnesota, and industry, to promote better windows.

2. Goals for Highly Insulating Windows Windows that gain as much heat from the sun as they lose. Ultimately, we see that windows can become an energy-neutral portion of the building shell, and an important part of achieving the ZEH goals. A collaborative team is working with industry to make these improvements in windows more widely available. Before talking about technology developments, need to give some background about how windows perform and how this performance is rated.Ultimately, we see that windows can become an energy-neutral portion of the building shell, and an important part of achieving the ZEH goals. A collaborative team is working with industry to make these improvements in windows more widely available. Before talking about technology developments, need to give some background about how windows perform and how this performance is rated.

3. Defining Zero Energy Windows Zero Energy Windows have a net-zero annual energy balance Approach: Model �standard houses� in 5 different locations Vary windows from very insulating to very bad Vary windows from high solar gain to low gain Plot the results in a graph

4. Performance Goals This diagram illustrates how DOE selected its research targets. The y-axis is insulating value (resistance to heat flow) and the x-axis shows solar gains. The contours are the annual heating and cooling energy for the house. As you�d expect for a climate like Minneapolis, the shape of the contours show that the ideal window is highly insulating yet allows a lot of solar gains. The yellow line shows the threshold of zero net annual energy due to windows. The typical Energy Star window is still pretty far from the line, but it�s possible with static SHGC windows to get close to zero. It�s not shown here, but seasonally dynamic SHGC windows can reach the zero threshold with less insulating value. Main takeaway is that it�s a complicated problem where different products have different performance- ie. you have to think about what you are doing and not look for simplistic answers everywhere.This diagram illustrates how DOE selected its research targets. The y-axis is insulating value (resistance to heat flow) and the x-axis shows solar gains. The contours are the annual heating and cooling energy for the house. As you�d expect for a climate like Minneapolis, the shape of the contours show that the ideal window is highly insulating yet allows a lot of solar gains. The yellow line shows the threshold of zero net annual energy due to windows. The typical Energy Star window is still pretty far from the line, but it�s possible with static SHGC windows to get close to zero. It�s not shown here, but seasonally dynamic SHGC windows can reach the zero threshold with less insulating value. Main takeaway is that it�s a complicated problem where different products have different performance- ie. you have to think about what you are doing and not look for simplistic answers everywhere.

5. Minneapolis

6. Non-structural center-layers Current technologies for highly insulating products use multiple layers of low-e and gas fill All glass is heavy Thin film products expensive Multiple spacers can lead to gas leakage LBNL research aims to develop lower-cost, non-structural center layers Utilize available low-e and gas-fill technologies Research novel center layer designs and materials In the diagram, standard triple glaze window is at top, new technology is at bottom. Key points to DOE research: use existing components, use less expensive center layer, and use only one spacer to reduce cost and gas leakage.In the diagram, standard triple glaze window is at top, new technology is at bottom. Key points to DOE research: use existing components, use less expensive center layer, and use only one spacer to reduce cost and gas leakage.

7. Non-structural center-layers: Acrylic center layer In the diagram, standard triple glaze window is at top, new technology is at bottom. Key points to DOE research: use existing components, use less expensive center layer, and use only one spacer to reduce cost and gas leakage.In the diagram, standard triple glaze window is at top, new technology is at bottom. Key points to DOE research: use existing components, use less expensive center layer, and use only one spacer to reduce cost and gas leakage.

8. FY07: Non-structural center-layers:Thin glass Very thin glass (e.g. .7mm) is now available in large sizes as a result of LCD and Plasma TV markets Prices are falling rapidly as volume increases Samples recently received from Corning IGs to be built in �08 Will center layers bow? � depends on how they are positioned Cost and Handling issues? In the diagram, standard triple glaze window is at top, new technology is at bottom. Key points to DOE research: use existing components, use less expensive center layer, and use only one spacer to reduce cost and gas leakage.In the diagram, standard triple glaze window is at top, new technology is at bottom. Key points to DOE research: use existing components, use less expensive center layer, and use only one spacer to reduce cost and gas leakage.

9. Prototype Testing Results:Simple insert performs as well as fixed layer The window cross-section on the left shows one of the prototypes tested. The colored image is an IR thermograph of the interior surface of the window, and the graph shows a vertical profile of window interior temperature. The prototype shows a fairly uniform temperature close to the indoor air temp (20 degC), and very similar performance to what one would see from a window with a full glass center layer. So from a thermal standpoint, these inexpensive center layers seem to be as good as standard triple glazed. There are still details to be worked out with manufacturability, which is where DOE is focusing its research efforts now.The window cross-section on the left shows one of the prototypes tested. The colored image is an IR thermograph of the interior surface of the window, and the graph shows a vertical profile of window interior temperature. The prototype shows a fairly uniform temperature close to the indoor air temp (20 degC), and very similar performance to what one would see from a window with a full glass center layer. So from a thermal standpoint, these inexpensive center layers seem to be as good as standard triple glazed. There are still details to be worked out with manufacturability, which is where DOE is focusing its research efforts now.

11. Modeling

13. Chinese version of WINDOW6

15. FY07: Non-structural center-layers:Structural Issues: Acrylic CYRO, leader in production and development of acrylic for fenestration products, is supplying us with various types of acrylic sheet to better understand which type of acrylic sheet is suited to center-layer applications In the diagram, standard triple glaze window is at top, new technology is at bottom. Key points to DOE research: use existing components, use less expensive center layer, and use only one spacer to reduce cost and gas leakage.In the diagram, standard triple glaze window is at top, new technology is at bottom. Key points to DOE research: use existing components, use less expensive center layer, and use only one spacer to reduce cost and gas leakage.

16. Heat Transfer through Windows To achieve these goals requires reducing heat losses through all mechanisms. The heat loss paths on the left are addressed using the strategies listed on the right. For this talk, I�m focusing on winter heat losses, not limiting summer solar heat gains (although that is also an important function of windows). We�ll come back to the heat loss reduction strategies later in the talk.To achieve these goals requires reducing heat losses through all mechanisms. The heat loss paths on the left are addressed using the strategies listed on the right. For this talk, I�m focusing on winter heat losses, not limiting summer solar heat gains (although that is also an important function of windows). We�ll come back to the heat loss reduction strategies later in the talk.

17. FY07: Non-structural center-layers:Spacers and sealants Super spacer, Swiggle-strip grooves for 3 layer design used in prototyping New BASF TPS technology; BASF visit to LBNL and continued discussions In the diagram, standard triple glaze window is at top, new technology is at bottom. Key points to DOE research: use existing components, use less expensive center layer, and use only one spacer to reduce cost and gas leakage.In the diagram, standard triple glaze window is at top, new technology is at bottom. Key points to DOE research: use existing components, use less expensive center layer, and use only one spacer to reduce cost and gas leakage.

18. Non-structural center-layers � FY08 Resolve issue of why acrylic layers deflect and determine what if any �upgrades� are needed Field-expose (at LBNL) samples Understand potentials of thin glass Continue/expand contacts with industry to explore cost, availability, business issues Window and IG manufacturers Spacer manufacturers Production Equipment manufacturers

19. FY07: Low-conductance Frame Heat Transfer For residential sized windows (6-10 sf total) the frame is 20-30% of area and thus a critical element of a high R window Little experience in the U.S. with highly insulating frames Turn to Europe for Review of European low-conductance frames How do we assess actual performance of a low-conductance frame? (see related Software Tools effort)

20. FY07: Low-conductance Frame Heat Transfer: Review of European frames Driven by Passivhaus requirement U< 0.8 W/m2-C (.14 IP) Literature review in collaboration with Arild Gustavsen, Norway Two themes More highly insulating frames Lower profile frames to capitalize on solar gains

21. Low-conductance Frame Heat Transfer: Insulating European frames Wood Frame with PUR

22. Low-conductance Frame Heat Transfer: Insulating European frames Wood Frame with Insulation Filled Al cladding

23. Low-conductance Frame Heat Transfer:FY08 plans Analysis of methods used in European frames Use/positioning of thermal breaks, cavities Hardware impacts Spacer impacts Analysis of other issues low emittance cavities phase change frames Testing IR (LBNL) Hot box (Norway) Performance issues (see Tools work; multi-year effort not currently funded) Continued collaboration with A. Gustavsen

24. Field Tests Objectives Document field energy performance and non-energy benefits of today�s highly insulating windows Improve homebuilders� familiarity with highly insulating windows Generate manufacturer interest in applications Projects Field demonstrations in Building America test houses Installation and monitoring of highly insulating windows vs. standard ENERGY STAR in collaboration with Cardinal IG in identical houses in Ft. Wayne, Indiana

25. Low-Energy Home Demonstration � FY07 Affordable home in MA (CARB Building America team) Heat Mirror (U=0.2) windows provided by builder�s normal supplier at no price premium Typical price premium strongly related to special order process Compared window-surface temperatures against baseline windows

26. Interior Surface Temperatures

27. Standard low-solar gain low-e vs. triple-pane with high-solar gain and insulated frames (U<.2) Side-by-side houses have been monitored, empty, since Jan 2007 Prior year�s data on typical Energy Star windows also available Cardinal Test Houses - Indiana