Skylights and rooflights in Penperlleni

A bungalow puts every room on one level, and the middle of the plan is often left without a window. The hall, the bathroom and sometimes a bedroom corridor sit between rooms that do have outside walls, so they rely on electric light from the moment the alarm goes.

The usual answer is a sun tunnel, which some makers sell as a light tube. A small dome sits on the roof slope, a tube runs down through the loft, and a diffuser is set into the ceiling of the hall. In a one-level house the loft is directly above the rooms, which often makes the run between slope and ceiling a short one. Where the route needs a bend, or the loft is crowded, the choice between rigid and flexible tubes counts, and that comparison explains the difference.

Early on a June morning the tube passes daylight down to the hall, and the bathroom door can stay open to share it. In the evening the tube has nothing to carry, and the diffuser is a pale disc until the ceiling light is switched on. That is how the product behaves, and it is worth knowing before ordering, so that a hall is not expected to be bright after dark.

Bedrooms are less suited. A tube has no way of being darkened, so a sleeping room does better with roof-window glazing that has a blackout blind chosen to go with it. The rooms for a tube are the hall, the corridor, a walk-in wardrobe and a small bathroom.

The covering on the roof affects the dome's flashing, so slate, clay tile and concrete tile are each noted at the survey, together with whichever slope sees the widest patch of sky. Our guide to sun tunnels and Building Regulations in Wales covers the paperwork side.

Placement in the hall deserves a moment. The diffuser is best where it reaches the doors and the way through to the other rooms, and in a one-storey plan that may be nearer the front door than the middle. If the hall is long, the tube can be positioned over its darkest stretch, and the loft hatch shows what the route allows.

A bathroom is a second candidate. A small inner bathroom has no window, so it depends on an extractor and the light switch, and a diffuser overhead gives it daytime light. An extractor remains the way to clear the air.

The loft hatch is the place to start, and the survey is arranged around it.

The A4042 is the Newport to Shrewsbury trunk road, and Penperlleni lies on it, 12.25 road miles north of Newport. For a house near any main road, the question after dark covers sound as well as light, since a passing vehicle is most noticed in the quietest hours.

Glazing is where the choice sits. On the VELUX side, flat and curved glass units can be had in double or triple glazing, which the maker describes as better for energy efficiency and sound, and its roof windows can carry a rain noise reduction build. Which options are on offer varies by window, so we read the maker's sheet for the model rather than assume. Our comparison of double and triple glazed rooflights covers the trade-offs.

Cold weather brings its own point. Bedroom air carries moisture from breathing, and overnight it meets cold glass before anything else, so condensation can gather there first. A sash that opens helps to clear it, and so does a trickle vent where the room has one. The maker's sheet shows what a given window offers.

Position counts as much as specification. A roof window on the slope away from the road sits further from the traffic than one facing it, and the survey notes which rooms face which way before a window position is proposed.

The energy figures are guidance. Approved Document L (Wales) says a roof window should have a U-value no worse than 1.4 W/m²K or a Window Energy Rating of band B, and a rooflight 2.2 W/m²K. These values apply to roof windows and rooflights respectively, and not to one another.

A bedroom facing the road benefits from a blind as well. A blackout blind darkens the room, which suits a light sleeper. Cold glass can collect moisture overnight, so an opening sash or an extractor in the room belongs in the plan.

Daylight and sound are two parts of a single specification. The room's use matters: a bedroom used mostly at night has different priorities from a kitchen used mostly by day. The survey asks which rooms face the road, which are used at night, and where the existing windows are, and the answers go into the specification.

The energy side has its own page, energy-efficient rooflights, for anyone who wants the detail before the visit.