A winter garden is one of the most desirable and at the same time most technically demanding glazed structures. Unlike a window, glass here is both wall and roof, so the structure deals with wind, snow, sun and moisture at once. Here are the decisions to make before ordering.
Cold or warm
The first question is how the space will be used.
A cold winter garden (unheated) is a seasonal veranda or buffer zone. Non-insulated aluminium systems can be used, but it will be cold in winter and condensation will form on the profiles.
A warm winter garden is a full living room used all year. The structure becomes part of the building envelope and must meet DBN V.2.6-31 thermal resistance requirements for glazed elements, and for the glass roof — for rooflights and roofs.
Do not mix the two: a cold structure with heating inside produces heavy condensation and large heat losses.
A dedicated system
For warm winter gardens manufacturers offer dedicated systems with thermally broken rafters, purlins and mullions. They solve tasks ordinary facades do not face: the junction of sloped glass with the wall, roof drainage, ventilation and a continuous insulation line around the whole perimeter. Building a winter garden from window profiles is risky.
Snow and wind loads
A glass roof carries snow. Loads are determined to DBN V.1.2-2:2006 (opens in a new tab) “Loads and effects” and depend on the site, roof shape and pitch. On shallow roofs snow lies longer and drifts against the house wall — these drifts must be included in the calculation.
Loads determine rafter sections, spacing and glass thickness. That is why a winter garden starts with a calculation, not with choosing a colour.
Roof glass
Safety is the main requirement for roof glazing. A typical build-up:
toughened outer pane — withstands thermal stress and hail;
laminated inner pane — if it breaks, fragments stay on the interlayer instead of falling inside.
Walls use energy-efficient glazing units, with solar control where needed.
Summer overheating
A glass room in the sun overheats very quickly. Countermeasures:
Solar-control glazing on the roof and south walls.
Ventilation: opening roof vents (hot air rises) and low-level wall openings for intake — the stack effect works well.
Shading: external awnings or blinds work better than internal ones because they stop heat before the glass.
Orientation: a north- or east-facing winter garden overheats less than a south- or west-facing one.
Winter condensation
In a warm winter garden, warm moist air condenses on the coldest surfaces. To avoid it:
choose systems with thermally broken profiles and warm-edge spacers;
provide air movement along the glazing (trench heaters by the walls);
control humidity — especially with many plants.
Drainage
Water from the roof must have somewhere to go. Systems have internal drainage channels in rafters and purlins as well as external gutters. Roof pitch, gutter position and the junction with the house wall are part of the design, not an on-site decision.
Permits
A winter garden added to a house or built on the terrace of an apartment building changes the building’s appearance and structure. Before starting, check whether approvals are required under current law and your building’s rules.
Step-by-step plan
Use scenario. Year-round living room, seasonal veranda or plant conservatory — the whole specification depends on it.
Survey and base. Check the load capacity of the terrace or foundation and the wall the winter garden adjoins.
Roof shape and pitch. Lean-to, gable, with a gable end — the shape affects loads and drainage.
Calculation. Snow and wind loads, rafter sections, glass thickness.
Indoor climate. Heating, ventilation, shading and humidity control are planned together with the structure.
Approvals. Agree changes to the building’s appearance and structure where required.
Production and installation. Only after drawings and details are approved.
Summary
A good winter garden is a properly chosen dedicated system, a snow and wind calculation, safe roof glass, thought-out ventilation and drainage. Made at design stage, these decisions turn the winter garden into the favourite space of the house in every season.
Winter-garden systems are in the Systems section.