@techreport {1846, title = {State-of-the-Art Highly Insulating Window Frames - Research and Market Review}, number = {Project report 6}, year = {2007}, institution = {INTEF Building and Infrastructure}, address = {Olso}, abstract = {

This document reports the findings of a market and research review related to state-of-the-art highly insulating window frames. The market review focuses on window frames that satisfy the Passivhaus requirements (window U-value less or equal to 0.8 W/m2K), while other examples are also given in order to show the variety of materials and solutions that may be used for constructing window frames with a low thermal transmittance (U-value). The market search shows that several combinations of materials are used in order to obtain window frames with a low U-value. The most common insulating material seems to be Polyurethane (PUR), which is used together with most of the common structural materials such as wood, aluminum, and PVC.

The frame research review also shows examples of window frames developed in order to increase the energy efficiency of the frames and the glazings which the frames are to be used together with. The authors find that two main tracks are used in searching for better solutions. The first one is to minimize the heat losses through the frame itself. The result is that conductive materials are replaced by highly thermal insulating materials and air cavities. The other option is to reduce the window frame area to a minimum, which is done by focusing on the net energy gain by the entire window (frame, spacer and glazing). Literature shows that a window with a higher U-value may give a net energy gain to a building that is higher than a window with a smaller U-value. The net energy gain is calculated by subtracting the transmission losses through the window from the solar energy passing through the windows. The net energy gain depends on frame versus glazing area, solar factor, solar irradiance, calculation period and U-value.

The frame research review also discusses heat transfer modeling issues related to window frames. Thermal performance increasing measures, surface modeling, and frame cavity modeling are among the topics discussed. The review shows that the current knowledge gives the basis for improving the calculation procedures in the calculation standards. At the same time it is room for improvement within some areas, e.g. to fully understand the natural convection effects inside irregular vertical frame cavities (jambs) and ventilated frame cavities.

}, keywords = {energy use, Passivhaus, thermal transmittance, U-value, window frame, windows}, isbn = {978-82-536-0970-6}, author = {Arlid Gustavsen and Bj{\o}rn Petter Jelle and Dariush K. Arasteh and Christian Kohler} } @article {1861, title = {Subject Response to Electrochromic Windows}, journal = {Energy and Buildings}, volume = {38}, number = {7}, year = {2006}, month = {07/2006}, pages = {758-779}, chapter = {758}, abstract = {

Forty-three subjects worked in a private office with switchable electrochromic windows, manually-operated Venetian blinds, and dimmable fluorescent lights. The electrochromic window had a visible transmittance range of approximately 3-60\%. Analysis of subject responses and physical data collected during the work sessions showed that the electrochromic windows reduced the incidence of glare compared to working under a fixed transmittance (60\%) condition. Subjects used the Venetian blinds less often and preferred the variable transmittance condition, but used slightly more electric lighting with it than they did when window transmittance was fixed.

}, keywords = {Electrochromic windows, energy use, Subjective response, Venetian blind use}, doi = {10.1016/j.enbuild.2006.03.011}, author = {Robert D. Clear and Vorapat Inkarojrit and Eleanor S. Lee} }