What type of glass should I use for a sunroom in Ottawa's extreme climate?

Glass is one of the most important decisions in a sunroom, because it has to perform in both deep winter cold and summer sun. In Ottawa, where winters regularly reach well below -20°C, the right glass controls heat loss, limits overheating and keeps condensation from forming on the inside. The wrong choice shows up every winter for the life of the room.

For a four-season sunroom, triple-pane insulated glass units are a common recommendation. Two sealed spaces between three panes insulate better than double-pane, and the difference matters most in the coldest weeks. Ask your supplier for the rated performance of the complete window or panel assembly, not just the centre of the glass, so you can compare options fairly.

Gas fill between the panes improves insulation compared with air. Argon is the usual upgrade; krypton performs better but costs more. Your supplier can show the rated difference for each option so you can judge whether it is worth paying for.

Low-emissivity coatings are thin layers that reflect heat back into the room in winter and can reduce solar heat gain in summer. How much solar heat you want to let in depends on orientation. A south-facing room can benefit from winter sun, while a west-facing room may overheat on summer afternoons. Ask the supplier or designer to recommend a solar heat gain level for each wall based on its orientation.

Spacers, the strips that separate the panes at the edges, are easy to overlook. Traditional metal spacers create a cold edge where condensation and frost form first. Ask for warm-edge spacers made of low-conductivity material to keep the edge of the glass warmer.

Overhead and sloped glass is a special case. Glass in a roof has to meet safety requirements so broken glass does not fall into the room, and it must be designed for the snow load the Building Code sets for Ottawa. Glass near the floor and in doors also has safety glazing requirements. Your designer will confirm what each panel needs; make sure it is written into your contract. Many designers suggest a solid insulated roof with skylights instead of a fully glazed roof for better winter performance and less snow on the glass.

Glass is a large share of a sunroom's cost, and price depends on room size, specification and how much of the wall is glazed versus solid. Be wary of trimming the glass specification to save money upfront, since comfort and heating costs depend on it. Ask for itemized quotes that list the glass specification for each option, and compare contractors in the Ottawa Construction Network directory.

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Looking for experienced contractors? The Ottawa Construction Network connects homeowners with qualified professionals:

• Justyn Rook Contracting
• RenoMotion Inc.
• Diamond renovations
• Eastern Residential Solution
• MAK Construction and Development Inc