The University of Waterloo's Faculty of Architecture building (left), built years ago, is far more energy efficient than modern high-rise condos in the GTA. “Windows are expensive (in terms of energy loss),” he said. The cheap- est solution is to reduce the area ded- icated to them. If the window area is reduced to 31 per cent (with an R2 value) you would have an overall R rat- ing of 5.3. If you do the same with energy efficient R4 windows, you could reach R8.9 overall.” “You make trade offs in design,” he said. “You make intelligent choices about how you spend your money.” There are other issues, he said, with curtain window walls. As much as they leak heat in the winter, they absorb heat from the sun in the sum- mer, creating truly heavy air condition- ing loads. He said buildings built by investor- owners, rather than for quick resale to condo purchasers, are being built to a higher standard. There are solutions, he said, in- cluding solar control glass, thermo/ electronic systems that control the light intensity, and interior and exter- nal shade and blind systems. “Curtain walls have very poor ther- mal comfort performance,” Straube said. “Specifying better products and reducing (window) area reduces costs and significantly improves per- formance.” “Higher industry performance should and will be demanded for our buildings,” he said. “Windows are the last big hole we have to fix.” The Canadian Design and Construction Report — Summer 2014 – 5