New rooflights and skylights in Ynysybwl

Check the old window for vents before you order its successor. Approved Document F (Wales) covers ventilation, and it wants a replaced window to leave the home airing as well as it did before. If the old one had trickle vents, the new window should be fitted with vents no smaller than those, controllable by the occupant or automatically. Without old vents, in a house that relies on natural ventilation, one route is to fit vents with an equivalent area of 8,000 mm² or more in a habitable room or kitchen, and 4,000 mm² or more in a bathroom.

Write down what the old vents looked like, and where they sat, before the old window goes.

The words matter on a quote. A roof window sits in line with the slope. A rooflight is raised on a kerb or upstand, and some people call it a skylight. The guidance figures differ between the two, so check which one a quote describes.

The energy side is guidance too. Approved Document L (Wales) says a new or replacement roof window in an existing home should have a U-value no worse than 1.4 W/m²K, or a Window Energy Rating of band B. Ask any supplier to state the figure on the quote, and compare like with like.

A swap in the same opening can keep the structural work small, because the hole in the roof is already there. It is still building work. Where the work is notifiable, we handle the Building Regulations notification with local authority building control or a registered building control approver, and the guide to replacing an old skylight shows how that differs from a new opening.

If the room below is a bedroom or a bathroom, settle the blind alongside the glazing, because it is an easy item to leave until the room is already in use.

At the survey, bring the answers to three questions. Did the old window open, and how far? Who in the house reaches it? And does the room get damp, from a shower or from drying washing? Those three shape the sash, the vents and the controls more than the frame size does.

Ynysybwl grew after the Ocean Coal Company sank Lady Windsor Colliery on 16 June 1884, following test bores begun by David Davies in the early 1880s at Graigddu, the Black Rock. Houses of every age get extended at the back, and a lantern is one way to light a single-storey addition.

A roof lantern stands up from the flat roof as a glazed box with pitched sides, so it takes more of the ceiling than a flat rooflight does and changes the look from the garden. Brett Martin, which makes lanterns, asks in its technical bulletin for a builder's upstand 150 mm high at the least, built level. A lantern from the firm tolerates up to 5 degrees of fall, though the maker's own warning is that it will likely look lopsided. All of this is advice for that maker's lantern, and any other make comes with its own details.

Planning is the first thing to settle. How a lantern built as part of a new extension is treated is something we confirm with the council. Our page on planning and Building Regulations for lanterns goes through it.

Once supper starts the glass overhead turns dark, and the lit room shows through it: the pendant, the table, the people round it. A clean, squared reveal gives a calm edge to that panel, which is why we talk through the plasterboard lining before the lantern is ordered.

Think about heat and steam as well. A room with a cooker and a kettle fills with moisture, and a tall piece of glass is a large surface for it to settle on. A hood that vents outdoors helps, and so does any part of the unit that opens. Ask at the survey which parts of the glass open, and who can reach them.

Sun matters too. A lantern or rooflight on a sunny side of the house can let a lot of afternoon light into the room, so ask what blinds or shading are offered for the model, since the choice differs from one maker to the next.

Finally, think about the ceiling inside. The shape of the lining under a lantern is part of the design, so mark the table position on the floor with tape and bring it up at the survey.