Penarth rooflights and skylights

Plymouth and Westbourne Roads are known for imposing three-storey red brick Victorian houses, and a house of that height has a long staircase. By the time it reaches the top landing the stairs have passed several windows, or none at all, and the last flight is often the dimmest part of the house. A roof window set over the stairwell sends light down the shaft.

The top floor is the other beneficiary. A bedroom or a study under the slope gets sky overhead and a view of cloud, in place of the neighbours' chimneys. We note the pitch and the covering, and read the direction of the slope, because a south-west face gets the afternoon sun.

A blind for the top-floor room is chosen alongside the window, taking in what the maker lists for each model. For a bedroom it is the blackout blind that matters, for the summer mornings and the lamp-lit evenings alike. For a stairwell window a plain blind, or none, will do, since nobody sleeps there.

Warmth is where older houses ask more of a window. Approved Document L (Wales) says a new or replacement roof window should meet 1.4 W/m²K, or Window Energy Rating Band B. Where a home has architectural or historic interest, or a front whose character has to be kept, and a replacement window or roof window cannot reach 1.4, the document gives a fallback of 1.2 W/m²K centre-pane glazing or low-e secondary glazing. It offers no such fallback for rooflights.

Those are guidance figures, not law, and the wording is "should". The glazing is chosen with them in mind.

If the house sits inside a conservation area, a rooflight on any slope of it, front or rear, is not permitted development in Wales, so the council is asked before anything is ordered. Our page on rooflights in conservation areas in Wales explains the planning side.

Where the work is notifiable, we handle the Building Regulations notification with local authority building control or a registered building control approver.

July puts a roof window to the test. A top-floor room under a slate slope collects the afternoon sun, and warm air gathers up near the slope as the evening goes on. A window that opens lets some of it out, and a blind takes the edge off the afternoon.

Approved Document F (Wales) deals with purge ventilation, the quick airing of a habitable room. Its test, for a hinged or pivot sash, depends on the opening angle. Opened 30 degrees or more, the sash needs an opening area of one twentieth of the room's floor area. Opened between 15 and 30 degrees, it needs one tenth. A sash opening under 15 degrees is left out of the test altogether. How wide a roof window opens is therefore worth checking against the room it serves, and our Building Regulations guide for Wales gives the full test.

When the sun has gone, the pane turns dark and returns the reflection of the lamp beside the bed. It is a fact about glass above a lit room, and it settles whether a blind stays closed in the evening as well as at noon.

A rooflight on a flat roof asks a different question. Approved Document L (Wales) says a rooflight should have a U-value no worse than 2.2 W/m²K, while a roof window's figure is 1.4 W/m²K or Window Energy Rating Band B.

Summer crowds are part of the town's story. The railway link to the Welsh valleys arrived in 1878 and brought a regular influx of day trippers, often hundreds of them at weekends and bank holidays. In the Victorian era the town was packed with visitors from the Midlands and the West Country as well. The traditional seafront is still a regular summer holiday destination, though numbers are much lower than they were from Victorian times until the 1960s.

From the tall red brick houses of Plymouth and Westbourne Roads to the stone terraces of Cogan, a top-floor room can gather summer heat, and a roof window with the right blind and the right opening suits a room like that.