74 — Friday, January 24, 1992 — North Shore News IN THE ongoing battle by homeowners to keep the heat in and the cold out, windows represent an enormous handicap. Twenty-two per cent of the heat lost in a conventionally built home escapes through windows. This lost heat represents a lot of energy — about three per cent of the total energy use in Canada, or the equivalent of 606 million barrels of oil each year. At current energy prices, heat loss through windows costs homeowners a_ significant part of their annual fuel bills. A new generation of win- dows promises to revolu- tionize the industry and ‘transform a serious liability into an attractive, energy- saving option. High-per- formance windows apply advanced technologies and materials to improve all three major window com- ponents: glazing, edge spacers and frame. Super glazings Back in the 1970s, resear- chers discovered that a thin film applied to window glazing acted as a heat bar- rier. The film is virtually transparent and it returns up to 90% of the heat given off by warmed objects in- side a room. The process works equally well in either direction, keeping heat inside in winter and outside in summer. The tesult is lower heating and cooling costs. As an added benefit, the coating also blocks incom- ing ultraviolet light (some manufacturers now claim up to 99% effectiveness), which is responsible for fading carpets, drapes and = fur- niture. These coatings, call- ed ‘‘low-E,” are either hard or soft. ; Soft or ‘‘sputtered’’ coatings are most effective, and can reflect 90% of the heat back into the room. More difficult to manufac- ture, they are more expen- sive. Hard coatings are more durabie, cheaper and can be handled like normal glass. The coating may be applied to the glass or to a thin plastic film suspended be- tween two panes. This ar- rangement performs like a triple-glazed unit, but without the added weight of an extra sheet of glass. Before buying ‘‘low-E”’ coated glass, ask the dealer about the type of coating that is used and its emissivi- ty; the lower the rating is, the higher the insulating factor. “Fill er up” Another mechanism of heat loss in windows is con- REAL ESTATE High-performance windows save energy vection — the migration of heat between the two panes of a sealed unit on currents of air. One way to prevent air movement between the glaz- ings is to replace the air with an inert gas. The inert gases, argon and krypton, are most commonly used for this purpose. In a conventional sealed window unit, gas-filling yields only a marginal im- provement in performance. But in windows equipped with ‘low-E’ glass, gas- filling boosts the thermal performance of the glazing, thereby increasing the in- sulation factor. “‘Low-E,’’ gas-filled windows are now widely available in Canada. A. gas-filled window should be clearly labelled as such by the manufacturer. Before you buy, ask about the warranty on the window and the gas sea’. Edge spacers No matter how effective the glazing may be, the use of conductive spacers can reduce a window’s overall performance by as much as 34%. Conventional windows, use rolled aluminum spacers. Rolled aluminum is light and durable (it lasts up to 20 years), but it conducts 3,000 times more heat than the glass. New, non-conductive spacers are now being de- FARIMA ROBERTS RES: 929-5577 OPEN SAT 1-3/SUN 2-4 A MUST TO SEE veloped for use in high- performance windows. These include plastic, ex- truded foam reinforced with pleated aluminum strips, and dlack steel. An insulating foam spacer is being developed with support from Energy, Mines and Resources Canada. Tests have shown that it can teduce heat loss by 20% compared to a_ standard unit. The effect of insulating spacers on window perfor- mance can be dramatic. The more energy-efficient the glazing, the greater the benefits of a non-conduc- tive spacer. An insulative spacer also keeps the edges of the glass warmer, reducing thermal stresses and lessening the likelihood of condensation during cold-weather. Before buying a_high- performance window, ask the dealer about the type of edge spacer used. Frames and sashes Since the frame can ac- count for as much as 25% of the total window area, it should be at least as well- insulated as the glass. Alu- minum, wood and PVC plastic are widely used as material for frames. Aluminum is durable and requires little maintenance. But unless the inner and outer portions of the frame are effectively separated by a thermal break (a non- conductive spacer), heat will conduct through it rapidly. An aluminum frame — even one provided with a thermal break — will reduce the performance of a standard double-glazed unit window by about 24%. Look for the CCMC (Canadian Construction Materials Centre) number on a metal window frame. It indicates the window has been tested for condensation resistance and is likely equipped with a_ thermal break. Woed is a good choice as a framing material. It is rigid and conducts little heat. In a_ conventional double-glazed unit window, the wood frame has about the same insulating value as the glazing. Wood frames need regu- lar maintenance to resist rot and mildew. Clad wood frames are protected with a covering of aluminum or vinyl. These windows re- quire littie maintenance, but the cladding must be well installed to prevent moisture from collecting behind it. Vinyl frames provide good insulation and do not need painting. However, vinyl frames that are rein- forced with metal on the in- side to increase their rigidity will lose heat. It’s better to reinforce with wood. The suitability of. other materials for frames and sashes is being looked at. Fibreglass frames are now appearing. This material holds considerable promise because it is non-conduc- tive, rigid and, unlike wood, requires little maintenance. Energy savings...and more Typically, high-perfor- mance windows cost I5 to 20% more than their con- ventional counterparts. This additional expense can be quickly recovered in reduc- ed energy costs. Researchers at Energy, Mines and Resources Canada have calculated that if only half of the five million square metres of glazing that is in- stalled in Canada each year were high-performance designs, the annual energy savings across the country would amount to $36 mil- lior. : te High-performance win- dows do more than save energy. Because they lose less heat, the inner pane stays warmer. The warm giass feels more comfortable and is less likely to cause condensation wiien you in- crease indoor humidity. Installing high-perfor- mance windows makes good sense (dollars and cents) for the homeowner and the en- vironment for a variety of reasons. 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