Key Elements of and Materials Performance Targets for Highly Insulating Window Frames

Journal Article · Mon Mar 28 04:00:00 EDT 2011 · Energy and Buildings

DOI:https://doi.org/10.1016/j.enbuild.2011.05.010· OSTI ID:1051278

Gustavsen, Arild; Grynning, Steinar; Arasteh, Dariush; Jelle, Bjorn Petter; Goudey, Howdy

The thermal performance of windows is important for energy efficient buildings. Windows typically account for about 30-50 percent of the transmission losses though the building envelope, even if their area fraction of the envelope is far less. The reason for this can be found by comparing the thermal transmittance (U-factor) of windows to the U-factor of their opaque counterparts (wall, roof and floor constructions). In well insulated buildings the U-factor of walls, roofs an floors can be between 0.1-0.2 W/(m2K). The best windows have U-values of about 0.7-1.0. It is therefore obvious that the U-factor of windows needs to be reduced, even though looking at the whole energy balance for windows (i.e. solar gains minus transmission losses) makes the picture more complex.In high performance windows the frame design and material use is of utmost importance, as the frame performance is usually the limiting factor for reducing the total window U-factor further. This paper describes simulation studies analyzing the effects on frame and edge-of-glass U-factors of different surface emissivities as well as frame material and spacer conductivities. The goal of this work is to define materials research targets for window frame components that will result in better frame thermal performance than is exhibited by the best products available on the market today.

• Research Organization: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
• Sponsoring Organization: Environmental Energy Technologies Division
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 1051278
• Report Number(s): LBNL-5099E
• Journal Information: Energy and Buildings, Journal Name: Energy and Buildings Journal Issue: 10 Vol. 43; ISSN ENEBDR; ISSN 0378-7788
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
29 ENERGY PLANNING, POLICY, AND ECONOMY
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
54 ENVIRONMENTAL SCIENCES
DESIGN
ENERGY BALANCE
FLOORS
Fenestration
window frames
heat transfer modeling
U-factor
thermal transmittance
thermal performance
MARKET
PERFORMANCE
ROOFS
SIMULATION
SPACERS
TARGETS
U VALUES
WALLS
WINDOW FRAMES
WINDOWS