The short answer
It can be, if your conservatory overheats or glares in summer and you want to keep a glass roof. A thin coating or tint on the glass turns away part of the sun's energy, so the room stays cooler and softer. The price is a slightly dimmer, tinted view and a higher cost than clear glass. Blinds, ventilation or a solid roof are the alternatives to weigh against it.
What the coating does
Ordinary glass lets the sun's energy straight through, which is why a glass roof can turn a conservatory into a greenhouse. Solar control glass carries a very thin coating, or a tint through the glass, that reflects or absorbs part of that energy before it reaches the room.
Makers describe the effect with a g-value, the share of the sun's energy that passes through. A lower g-value means less solar heat in the room. You will not find one number that suits every house, so ask for the g-value of the unit offered and compare it with the alternatives.
Heat is one thing and glare another. The coating also cuts the brightness of direct sun, which makes the room more comfortable to sit in at midday and kinder to screens, furniture and floors. Fading from sunlight is slowed, though not stopped.
Solar control glass is normally built into a sealed double-glazed unit, with the coating on an inner surface where it is protected from the weather. That is why it is specified when the roof is made, and not added afterwards as a coating on the outside of an existing pane.
There is a link to insulation too, as some coatings also reduce heat loss, but that is a separate property with its own figure.
The light you give up
No coating is invisible. Solar control glass has a faint tint, usually blue, green or grey, and it reduces the amount of daylight reaching the room. A conservatory that already gets little light, because it faces north or sits in the shade of the house, may feel dim under it.
The effect shows in the view as well. Looking up through the roof, the sky can look slightly different in colour, and some owners notice it more than others. Ask to see a sample pane against the sky before you order, in daylight, not under shop lights.
The trade-off is between comfort and brightness. A south-facing room that overheats and glares may gain a great deal. A shaded room may gain little and lose light it needed.
Roof windows or a lantern with solar control glazing can help in a solid roof, as they let the light in while handling the heat. Our answer on a tiled roof making the room darker looks at lighting in a solid roof, and the same ideas of balance apply.
If you want more daylight and less heat at the same time, ask about the visible light transmission of the glass as well as the g-value.
Cost and the rules that apply
Solar control glass costs more than clear glass, because of the coating and the sealed unit. The price depends on the size, the number of panes, the frame and the supplier. A price comparison is only fair between units of the same specification, so ask each firm for the same details.
The Planning Portal's own wording is that a new roof must comply with building regulations, and that covers this one. Where the energy rules apply, Approved Document L gives a limit of 2.2 W/m²K for rooflights, and a solar control coating is about sunlight, not about heat loss, so ask for the U-value and the g-value separately. Building control will confirm which figures fit your conservatory.
A glazed roof also has to carry the weight of heavier double glazing. An older frame may have been built for thinner glass or polycarbonate, and a structural check may be needed. Our answer on dwarf wall strength covers the question for solid roofs, and the principle is the same for heavy glass.
Condensation can still form on the cool inner face in winter, and the glass does not remove the need for ventilation.
Alternatives to compare
Several cheaper or different routes tackle the same problem. Blinds on the inside, or better still on the outside, stop the sun before it reaches the room. A solar film applied to existing glass cuts glare and heat, though it can affect the sealed unit's warranty and may not suit every pane.
Ventilation does a lot. Opening roof vents and doors lets hot air out, and an opening roof window or lantern in a solid roof works at the top of the room, where the heat collects.
A solid roof is the most complete answer. It blocks the sun overhead, adds insulation and removes most of the glare, though it cuts light too. Our guide to the polycarbonate vs glass roof compares the other glazed choices.
Whichever route you take, ask for the figures in writing: the U-value, the g-value and the light transmission of the glass. They let you compare like with like, so ask any firm that cannot give them why not.
The conservatory roofs hub explains the options, and our survey records the aspect, shading and frame before any glass is suggested.
