A new aesthetic has taken over Calgary's condo industry over the past decade.

Buildings featuring floor-to-ceiling windows, rather than walls, are all the rage because many find them attractive and like the views that are offered. 

However, some in Calgary's building industry are raising concerns about the long-term sustainability of these glass towers.

The Alberta Building Code specifies regular walls need to have an insulation value — or R-value — of 20.

However, regulations do not specify how much insulation developers need to put in windows.

That means developers can install windows with any insulation value they like and residents say they can feel the difference.

"When it's really cold, like -25 C, and we have so many windows, then it's really cold in that area," said Ester Pila, who has lived in a glass-walled Beltline condo for the past eight years.

Still, one of the big draws of glass-windowed condos is the views — and Pila says that makes a big difference when it comes to urban living.

"When you're in a condo and you have a limited amount of space, having windows makes you think you're in a bigger place," she said. "Plus, it's beautiful. It's great on a snowy day to look outside and see how stunning it is. I can't look out a wall."

Windows come with multiple problems

Brian Sheddon specializes in condo exteriors and calls himself the "window doctor."

He says in his experience, most developers install window walls with two panes of glass which typically only have an R-value of two — at most, of three.

Sheddon says he gets calls every week about window walls and the problems with their design, assembly and seal.

"We've got issues of moisture penetration coming from the exterior, such as rain or snow melt, and we also have a lot of very cold surfaces on the interior," he said. "Any moisture that's present in the air just from living in your house — taking a shower, boiling a pot of water for tea — it likes to condense on the cold surfaces and run down and damage the drywall or the flooring or whatever happens to be below this window system.

Architect Tang Lee says the big concern is the sustainability of the walls and their energy efficiency.

"These buildings that [are] being built today are going to consume so much energy that the public is not going to be able to afford to pay for the heating and cooling of these buildings," Lee said. "You may find that a lot of these buildings may become abandoned, they would actually be 'white elephants' in the future they're just too expensive."

Part of the problem lies in the fact that glass is not good at blocking solar radiation.

When the sun beats through the floor-to-ceiling windows in summer, it can feel like living in a greenhouse.

'Tremendous amount of heat loss'

In winter, it's exactly the opposite — and Lee says even with double-glazing, those window walls are providing about as much insulating power as two pieces of paper.

"Between the -30 C outside and 20 C inside, there's a tremendous amount of heat loss," he said.

Some developers of glass-walled condos, like The Montana in Connaught, say they use triple pane glass to increase energy efficiency.

The units in that building sell for roughly $450,000 and like many things, homeowners get what they pay for when it comes to glass windows.

But triple pane glass is much more expensive — an expense that is typically passed along to the condo buyer.

If a triple pane window wall is out of your price range, Sheddon recommends narrowing the condo hunt to focus on newer buildings.

The City of Calgary only started inspecting window walls this year and as of Feb. 1, every new home in Alberta — including new condos — has a mandatory five-year warranty on the building envelope under Alberta's New Home Buyer Protection Act.