Glass room is a marketing term covering everything from an aluminium framed veranda with sliding screens to a fully insulated glazed extension. The products are not comparable and the quotes look similar, so the only way to judge them is to ask what the roof is, what the glazing specification is, and whether the space is heated or seasonal.
Three products under one name
The first is an unheated glazed shelter, often frameless sliding panels under a veranda roof, which extends the season by a few weeks at each end and is never a room you sit in during January. The second is an insulated garden building with large areas of glass, which is a year round room. The third is a glazed extension attached to the house and built into its thermal envelope. Price per square metre rises sharply across those three and so does what you get.
What to ask glass rooms UK suppliers
What the roof is made of and what it is insulated to. Whether the glazing is double or triple, what the coating is and whether it has solar control. Whether the frames are thermally broken. Whether the floor is insulated and what the base is. How the space is heated and ventilated. Those six answers separate the products far more reliably than the brochure photography does.
Summer and winter in a garden glass room
Glass loses heat in winter and gains it in summer, so a glass room without shading is uncomfortable at both ends of the year. External shading, solar control glazing and openings on two sides for cross ventilation are what make it usable, and thermal mass in the floor evens out the swings. Internal blinds help with glare and do little about heat, because by the time they act the energy is already inside.
Small garden sun rooms, in the garden or against the house
A detached glass garden room under the outbuilding rules is usually quicker and simpler to build and keeps the house untouched, and a small one is often the better value because the area of glass is smaller and the comfort problem is proportionally smaller. Attached to the house it becomes an extension or a conservatory, judged on the extension limits and, where it is thermally separated by external quality doors, treated differently from a heated room.
Questions people ask about glass rooms
Is a glass room usable in winter?
Only if it is insulated, heated and the glazing is specified for it. An unheated glazed shelter extends the season rather than adding a room.
Do glass rooms need planning permission?
A detached one is judged under the outbuilding rules on height, position and garden coverage. Attached to the house it is judged as an extension.
What stops it overheating?
External shading, solar control glazing and cross ventilation. Internal blinds mainly help with glare.
How do I compare two quotes?
On the roof construction, the glazing specification, the frames, the floor and how it is heated and ventilated. Those decide the product you are buying.