Can a Sun Tunnel Have a Ventilation Kit?

A plain sun tunnel carries light only. The tube is sealed top and bottom, and no air passes through it. A ventilation kit changes that by adding a way for air to enter or leave the room through the tube, or alongside it.

There are two broad kinds. One uses a small fan that sits in the tube and extracts stale air, with a grille hidden in the diffuser. The other is passive, with an adjustable vent in the ceiling lens that lets air rise through the tube and out of a vent at the dome, so air can flow without electricity.

The best rooms are the ones with no window and no outside wall. That usually means a bathroom in the middle of a terrace or a cloakroom beside the stairs. In such rooms a sun tunnel with a vent can replace both a ceiling light and a separate extractor.

A landing on a 1930s semi can benefit too. Stale warm air collects at the top of the stairs on summer afternoons, and a passive vent gives it somewhere to go. For a windowless bathroom, our page on a sun tunnel for a bathroom covers the whole picture.

A vent kit is a modest ventilator. An opening roof window or an electric opening rooflight shifts a great deal more air, because the whole sash moves out of the way. Part F lets a roof window that opens count as purge ventilation. A small tube vent is not designed to do the same job.

The two can also work together. A loft room might have an opening roof window, while the landing below has a vented tunnel, so the stair and the room both have airflow.

A fan kit needs a power supply. We take a spur to the diffuser, or run a switched feed from the nearest light circuit, and the wiring is done to current regulations. A passive kit needs no wiring at all, which is why it is popular on landings.

The tube must stay sealed to the room, apart from the vent itself, so the vent is fitted with a closing flap to stop draughts when it is off. The route of the tube matters here too, because a long run with bends reduces what a fan can move. If the loft allows a short, straight drop, a rigid tube works best; see rigid vs flexible sun tunnels.

The roof is made weathertight at the end of every day, and floors are protected throughout the job.

Fixing the vent is the fiddly part, so we ask a few questions at the survey: where the nearest electrical feed is, whether the loft above the room is boarded, and whether the ceiling below the tube is plasterboard or lath and plaster, as in many older terraces. Each answer changes the method, though none of them rules a kit out. On an older ceiling we cut the diffuser ring in carefully and support the plaster around it, so it does not crack or crumble.

Adding a vent means a path for air, so the heat question is worth asking again. A closed flap and a sealed lens keep losses small, and our answer on whether sun tunnels lose heat explains why. A fan adds a little sound, so ask for a quiet model if the room is next to a bedroom.

On cost, the kit adds a line to the quote, and adding it on the first visit costs less than coming back. Ask for it priced separately and decide with the number in front of you. The range of tunnel prices is covered in how much a sun tunnel costs, and the wider service is set out in our sun tunnel installation hub.

The free survey and written, itemised quote are the place to settle all of this, with no obligation.

It is worth thinking about where the damp air ends up. A vent that exits at the dome sends it straight outside, which is better than pushing it into the loft, where it can condense on cold timbers. We make sure the vent terminates outdoors and never into the roof void. A fan kit should also be switched with the bathroom light or a timer, so it runs while the room is in use and for a while after. This helps moisture clear after a shower, though it is not a substitute for opening a window when you can.