The forgotten 90 per cent

A window's design and look is very important, but so to is its efficiency. File photo
A window’s design and look is very important, but so to is its efficiency. File photo

While a window’s style, frame and parts only contribute to about 10 per cent of what you get in a window unit, these details usually receive most of the attention from potential buyers. And that’s fair. Looks, color, and means of operation, are key, to be sure.

However, when shopping for windows, don’t dismiss what can often be the make or break feature in a windows efficiency, a.k.a. the forgotten 90 per cent, with that factor being of course the glass.

It wasn’t so long ago that dual, or thermal pane glass, hit the market. Basically two single panes of glass bonded together with a half-inch air tight seal in between, dual pane glass allowed homeowners their first true glimpse of winter from the inside.

Before the thermal unit, single pane glass provided the perfect surface for condensation, where on a really cold day, this natural phenomenon would often cover the entire pane with a sheet of frost. Quite decorative, in a way, frosty glass would provide youngsters with hours of creative fun time. Pressing your nose up against the glass would of course create a spot, and if you made a fist, then pressed the side of your hand up against the glass, then dotted the top of this image with your thumb and finger tips, you could simulate little bare feet walking across the glass, hilarious stuff.

Unfortunately, dual pane glass, along with further advancements including argon gas and Low-e film, and perhaps the introduction of the in-home computer and X-Box, totally killed this once cherished pastime. A good, or necessary thing I suppose, since the frost would eventually melt and puddle on the window sill, causing the paint to peal, and if left totally uncared for, would lead to the ultimate demise of the sill due to rot.

So, where are we today? Well, the standard dual glass, argon filled, Low-e panes stay relatively clear, with there being the occasional few inches of condensation at the bottom of a thermal pane, should there be an excess of humidity in the home. However, just like the transition days of single pane glass to the dual pane thermal unit, if your plan is to renovate this spring, or build a new home, it’s time to bump things up the efficiency ladder again. Why? Because with the costs of heating and cooling a home forever on the rise, adding energy efficiency, or improving the efficiency of any particular element of the home, be it insulation levels, furnace systems, or in this case, almost doubling the R-factor of your window panes, just makes good financial sense.

Where’s the bar set for window glass now? Triple pane, double Low-e coating, with argon gas. This triple pane version delivers a thermal resistance value of R-7.51, basically crushing the R-3.8 value of today’s regular dual, Low-e/argon glass pane, and eclipsing the R-2 value of the original, but cutting-edge in its day, thermal pane glass. The triple pane glass essentially eliminates the condensation issue, and acts as an excellent sound barrier, which can be of great value to those persons whose homes are situated along the 401, or who are regularly awakened by the toot of the Via rail locomotives. The double Low-e option does what Low-e film is designed to do, only at twice the efficiency of course, and basically reflects your furnace heat back into the room. Further to the Low-e strategy is a system called ‘Sunstop’, which effectively modifies the reflective values of the Low-e film in order to keep solar heat out. Why keep solar heat out? In most cases, our homes should welcome all the solar heat we can get. However, some home or renovation plans call for a southern facing wall that is practically all glass. Neat concept, but on a typical summer day, this type of scenario will roast you quicker than the chicken you just put on the BBQ. So, in the case of massive southern facing windows, the Sunstop system certainly has its purpose.

Therefore, when window shopping, don’t forget it’s 90 per cent glass.

Good building.

As published by the Standard-Freeholder
Handyman's Hints Standard-Freeholder Cornwall Ontario by Chris Emard

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