The answer
Yes. A loft is where most sun tunnels spend their length, running from the dome in the roof down to a diffuser in the ceiling below. The route needs a clear path, a gap in the roof timbers wide enough for the tube, and enough room to insulate the part that crosses the cold roof space. Trussed roofs, water tanks and boarded storage can all complicate it. A survey from inside the loft settles the question.
How the route works
In a house with a pitched roof and a loft, the sun tunnel goes in three stages. The dome and its flashing are fitted to the roof covering. The tube then runs from the underside of the roof, through the loft void, to a hole cut in the ceiling. The diffuser closes that hole from below.
The loft is a convenient place to be, since nobody sees it. The tube can lean, step sideways or drop straight down, subject to the structure. Because the room below is usually a landing or bathroom, the ceiling is at a regular height and the diffuser sits flush.
If the loft is converted, the picture changes. A conversion has plasterboard on the rafters and a floor over the joists, so the tube may have to run through the sloping ceiling and a stud wall, or be replaced by a roof window. We look at what is there and say which works.
What can get in the way
Most lofts have something between the dome position and the ceiling below. These are the usual ones.
- Roof trusses. Modern roofs often use thin timber triangles, and the diagonal members are part of the structure. They are not cut for a light pipe. A tube usually threads between them, but the gaps limit how wide it can be.
- Purlins, braces and hip timbers. Older cut roofs have heavier timbers in awkward places. A rafter can sometimes be trimmed and framed round, as long as it is done properly. A purlin is a different matter.
- Cold water tanks and pipes. A tank can often be moved a little, and a pipe re-routed, but both add to the job.
- Cables and extractor ducts. These are usually easy to work around, and you should not drill through them.
- Stored boxes and boarding. Not a structural issue, just something to clear before the survey.
Where the straight route is blocked, an angled elbow or a short flexible link gets round it, with some loss of brightness. Our guide to rigid or flexible sun tunnels explains the trade-off.
Loft hatches deserve a mention. If yours is the small kind, a tube section may not pass through it whole, and we cut lengths to suit. It is rarely a problem and it never changes the outcome.
Insulation and condensation in the roof space
The loft is cold in winter, and the tube crosses it. Warm room air that reaches the cold tube condenses, so the cold section needs insulating. The usual approach is an insulating sleeve or wrap fitted tight to the tube, and a seal at the ceiling so room air cannot travel up inside it.
There is a second point on the loft floor. Many lofts hold insulation laid across the joists. The tube has to pass through it, and the insulation should be brought up round the tube so there is no gap, because a hole in the blanket is a patch of heat loss. Dealing with this is routine for a proper installation.
Where the loft insulation is thick, the tube needs a collar or upstand to stop the blanket drifting into the opening, and to keep it from being compressed. We explain how we treat that detail at survey.
When the loft is not an option
Some houses have no usable loft above the room. A flat-roofed extension has only a thin roof build-up between the ceiling and the membrane. A room on the first floor of a two-storey house may have another bedroom above it. A loft conversion has used the space.
In a flat roof, the tube is short and the result is bright. In a room with a bedroom above it, the tube would have to climb through that floor, which only works through a cupboard or boxed corner, and often not at all. In a converted loft, a roof window, a flat rooflight or a slim conservation-style unit may suit better. See where sun tunnels work best for the rooms that suit a tube and the ones that do not.
Before recommending anything we go up into the loft and look at the roof from the inside as well as the outside. Our survey costs nothing, the quote that comes after it is written and fixed, and the Building Control notification is ours to deal with where one is needed.
What to expect on the day
A loft run is usually a tidy job. We mark the ceiling position from below and transfer it up to the roof, so the dome and the diffuser line up. The roof covering is lifted around the dome position, the flashing is fitted and the tube is run, supported and wrapped. The ceiling is then cut and the diffuser set and sealed.
We cover the floor below and keep the dust down. You will want the loft hatch clear and any boxes moved. The work is covered by our 10-year workmanship guarantee, in writing, and it is done to current Building Regulations. Details are on the guarantee page.
Afterwards, the loft is left as we found it, with the insulation back in place around the tube and nothing stored in the way of the route. The diffuser is the only part you see, and from the landing it looks like a plain round fitting in the ceiling.
If the dome is the part you are wondering about, the planning position is covered in our answer on sun tunnels and planning. One visit often settles both questions, since the person who looks at the roof can also check the route below it.