Does a VELUX Make a Loft Too Hot in Summer?

A loft room sits directly under the roof, so a VELUX window there faces the sun at closer range than a wall window ever does. Warm air also rises, so heat that builds anywhere in the house tends to collect under the rafters before it goes anywhere else. Add a rooflight set close to horizontal on a low pitch, and the glass is catching the sun almost square on for a large part of the day, rather than at the shallow angle a vertical window gets.

None of that is a fault in the window. It is physics: glass is transparent to short-wave sunlight, which passes through, warms the room's surfaces, and is then re-radiated as long-wave heat that the glass traps, much as a car windscreen does on a summer car park. A well-specified rooflight controls how much of that short-wave energy gets through in the first place, and a blind fitted on the right side of the glass stops a good part of it before it ever reaches the room.

VELUX offers glazing with different levels of solar control, and this is the first place to look if a loft runs hot. A standard low-E pane is built to keep warmth in during winter, which is exactly what you want on a cold night, but on its own it does little to stop solar gain in July. A solar control coating on the outer pane reflects a share of the sun's energy back out before it crosses the glass, so less heat arrives in the room in the first place, without darkening the glass or changing the view.

The frame's own insulation plays a smaller part here, mostly in how quickly a room loses heat overnight rather than how it gains it during the day, but it still affects year-round comfort. VELUX ThermoTechnology describes that insulated frame build, and VELUX glazing options sets out the full range of panes, including the solar control and safety choices, side by side.

Where a blind sits matters as much as what the glass is doing. An internal blind, fitted on the room side of the glass, only intervenes after the sun's energy has already passed through the pane and turned to heat inside the room. An external awning blind sits over the outside of the glass instead, so it shades the pane before that heat gets in at all. That single difference in position is the main reason an awning blind does more for a hot loft than a blackout blind on its own.

• An awning blind extends over the outside of the glass on a hot, bright day and can be drawn back for the view once the sun has moved round.
• A duo blind combines a light-filtering fabric with a blackout layer on the same window, useful where a room needs shade by day and full dark by night.
• A blackout blind is built for darkness, chiefly for sleep, and gives some shade but not the same heat control as a blind mounted outside the glass.

VELUX blinds: blackout, duo and awning sets out how each type sits when open, so the sky is not permanently framed by a folded pelmet of fabric.

Glass and blinds handle the sun's energy; airflow deals with the heat that has already gathered under the rafters. Most current VELUX windows have a small ventilation flap built into the handle bar, which lets a trickle of fresh air through even when the sash itself is closed and locked. What does the VELUX ventilation flap do? explains how it works and when it is worth opening on a still, warm night.

Opening the sash itself, even for an hour in the early morning or late evening, lets the warm air that has collected near the ceiling escape before the room fills again during the day. On a hot afternoon, a closed window with the blind and flap both in use will usually feel more comfortable than an open one letting more sunlight and outside heat straight in.

A manual window only vents or shades when someone is there to operate it, which is awkward on the hottest days, when a room can heat up during a working day with nobody upstairs to open the flap or draw the blind. An electrically or solar-operated window and blind can be set to run on a timer, or closed and opened by remote control, so the room is not left to bake all afternoon. VELUX INTEGRA: electric and solar opening explained covers how that control works, including the rain sensor that closes the window automatically if the weather turns while the house is empty.

Solar gain is one more reason placement is worth planning properly rather than centring a window on a rafter bay by habit. A window set higher on the pitch, further from a south-facing gable, or paired with a slightly deeper reveal can take some of the edge off direct summer sun while still opening a clean stretch of sky from the bed or the desk below. This is the same thinking behind a sightline sketch: it shows where the sun sits in the room across the day, alongside where the frame edges and any bars fall, so heat and view are planned together rather than one being fixed and the other left to a blind to fix afterwards.

A shallow pitch catches more overhead summer sun than a steep one, so a flat-roofed extension or a low-pitch dormer in a Peterborough new-town home, in Bretton, Orton or Werrington, is often the room where solar control glass and an awning blind earn their keep most. A steeper pitch on an older Fletton-brick terrace roof takes the sun at more of an angle for more of the day, though a south-facing slope still runs warm in July regardless of pitch.

Where a loft has run hot in a previous summer, or the room faces a wide stretch of unshaded roof, we look at glazing spec, blind type and ventilation together at survey stage, alongside the sightline itself. What affects the cost of a rooflight sets out how solar control glass, electric operation and blind choice each affect the overall specification. Every quote includes the sightline sketch, drawn from where you actually sit or lie, so the glass, the blind and the view are all decided at the same time rather than the blind being added afterwards to fix a room that runs too hot.

Start from VELUX window installation in Peterborough for the full range of windows, glass and blinds we fit, or read on for the detail behind each choice above.

Does tinted or darker glass stop a loft getting hot?

Tinting on its own absorbs some sunlight rather than reflecting it, so the glass itself warms up and re-radiates part of that heat into the room. A dedicated solar control coating, which reflects energy back out rather than absorbing it, does more for a hot loft than tint alone, and keeps the glass looking clear rather than shaded.

Will an awning blind block the view when it is not needed?

An awning blind retracts back against the top of the frame when it is not in use, so it does not sit across the glass once the sun has moved round or the day has cooled. It only extends over the glass when drawn down.

Does opening the window make a hot loft worse?

It depends on the time of day. Opening the sash in the early morning or evening, when outside air is cooler than the room, helps clear warm air that has collected near the ceiling. Opening it in full midday sun usually lets in more heat than it removes, which is where the handle-bar ventilation flap or a short early or late airing does more good than leaving the sash wide open all day.

Can an existing VELUX be upgraded with solar control glass without replacing the whole window?

The glazing unit sits within the sash, so in most cases the sash and its pane can be renewed to a current specification without disturbing the frame or the flashing. Replacing an old VELUX in the same opening covers what stays and what changes when a window is renewed.