Will a glass alfresco get too hot or fog up?

The two worries we hear most about glass enclosures are opposite ones: "Won't it be an oven in January?" and "Won't the glass stream with water in July?" Both happen when a glass room can't breathe. Both are easy to design out.

Summer: let the heat out

Glass lets in sunlight, which turns to heat inside. In a room that can't open, that heat builds up, much like a greenhouse. The fixes:

• Panels that open. Sliding or stacking glass on at least one side, ideally two, lets a breeze through. On a hot day you can open most of the wall and it feels like an open alfresco again.
• The right glass for your aspect. North- and west-facing glass gets the most sun. Ask about toned glass, which cuts glare, or Low-E glass, which has a coating that reflects heat.
• Shade over a glass roof. A glass roof on a north or west aspect benefits from a shade blind or sail in midsummer.
• Insect screens on the panels that open, so you can leave them open on summer evenings.
• A ceiling fan keeps air moving on still days.

Winter: let the moisture out

Fogging is condensation. Warm, moist air touches the cold glass and the water in the air turns to droplets on it. In a closed alfresco the moisture comes from people breathing, cooking (especially in an outdoor kitchen), unflued gas heaters and wet coats or umbrellas.

The fixes:

• Crack a panel open. A gap of a few centimetres lets moist air out while the heater runs. Sliding panels make this easy.
• Use an extractor or range hood over an outdoor kitchen.
• Use electric heaters, not gas patio heaters, which add moisture and aren't designed for closed rooms. See how to heat an enclosed alfresco.
• Consider double glazing if you'll heat the room most evenings. The inner pane stays warmer, so less moisture condenses on it.

The room behind needs air too

Many alfrescos sit in front of a living room or kitchen whose windows open onto them. When you glaze the alfresco, that room gets its daylight and fresh air through the enclosure. The building code allows this, but sets minimum glass and opening areas for the enclosure, worked out from the floor area of both rooms together. Your building surveyor checks it as part of the permit. See do you need a permit to enclose an alfresco?.

Design it to breathe from the start

The best time to solve heat and moisture is when you choose the layout: opening panels where the breeze comes from, fixed glass where the weather comes from, and the right glass on the sunny side. Our alfresco enclosure ideas show these layouts, and our alfresco enclosure cost guide shows what they cost.

We supply toned, Low-E and double-glazed glass, and insect screens. We measure on site, look at which way your alfresco faces, and quote in writing with the glass for each side listed. See our alfresco enclosures or ask for a quote.