Sunrooms near you

The label on a quote matters less than what the room is built to do. Ask each contractor which months the room is designed for, whether it will be heated, and whether it will be treated as living space connected to the house.

A four-season sunroom and a conventional addition look alike on a site plan, since both extend the house, but they behave differently once built. An addition has mostly solid, insulated walls with ordinary windows and is heated and cooled like the rest of the house. A sunroom trades wall insulation for glass, so it gains heat fast on sunny days and loses it fast at night, and its comfort rests on the glazing, the orientation and the shading.

Glass doesn't tolerate movement, so the base of a sunroom has to stay still. A four-season room usually gets a full foundation, a frost-protected slab or footings that reach below the frost line, much like an addition. A three-season room may sit on piers, helical piles or an existing deck or porch, but only once a contractor has confirmed that the structure below can carry the new walls, glass and roof. A footing that heaves in winter shows up as cracked panes, doors that bind and leaks at the seams.

Where the room meets the house is the other critical detail. The new roof ties into the existing wall or roof with flashing that sends water outward, and the connection has to be fastened into solid framing rather than just the siding. When that detail fails, water gets into the house wall, where rot can go unnoticed for years.

In a room that is mostly glass, the glazing sets the comfort. Natural Resources Canada rates windows and doors by U-factor, where a lower figure means less heat escapes, and by Energy Rating, where higher is better, while the solar heat gain coefficient shows how much of the sun's heat passes through. NRCan lists triple glazing, low-e coatings, inert gas between the panes and thermally improved spacer bars among the features that make windows more efficient and less prone to condensation, which matters most in a four-season room.

A sunroom is generally treated as an addition to the house. Toronto's permit guidance lists solariums among the additions that need a building permit, and it requires a permit to enclose an existing deck, porch or patio of any size, so glazing in a low deck that never needed a permit still does. Zoning rules on setbacks and lot coverage apply too.

Montreal handles permits by borough, so start with your borough's permit office. When the sunroom sits on a new or replaced raised deck or porch, the borough's deck rules come in as well: in Ahuntsic-Cartierville, for example, building or replacing one whose floor is more than 60 cm above the ground requires a permit. Wherever you live, have the drawings show the foundation, the roof framing and how snow loads are carried before you order a kit.

Natural Resources Canada explains that condensation forms in cold weather when moist indoor air meets a cooler surface, and in a sunroom the cool surfaces are everywhere. Water running down the glass points to glazing that isn't warm enough for how the room is used, to humidity from plants, a hot tub or the house, or to air that can't move across the glass. NRCan notes that air flowing across the glass helps keep it warmer, and that deep sills, closed blinds and furniture can block it.

Snow is the other winter test. A sunroom roof has to be designed for the snow your region gets, including drifts that build where a low roof meets a taller house wall and snow that slides off the main roof above. The manufacturer's or designer's snow-load information should match your location, not a generic figure.