In-Roof Solar Installation

What integrated means

An in-roof array replaces part of the roof covering rather than sitting on top of it. The tiles or slates come off the array area, a tray or flashing system goes in, the panels sit within it, and the surrounding covering is weathered into the edges.

The result sits flush with the roof plane, with a shadow line of a few centimetres rather than the ten or so of a rail-mounted array. On some houses that difference matters a great deal; on others it is barely noticeable from the ground.

Where it earns its place

Three situations make in-roof the obvious choice.

The roof is coming off anyway. On a new build or a full re-roof, most of the cost difference disappears. The tiles for the array area were never bought, the scaffold is already up, and the roofer is on site.

Appearance is a planning matter. In a conservation area, or where a planning condition or an officer’s comment concerns the projection of the array, a flush installation can be the difference between an approval and a refusal. It does not remove the need for consent where consent is needed, but it changes the conversation.

You simply want it to look right. This is a legitimate reason and we would not pretend otherwise. An integrated all-black array on a dark tile is a considerably quieter object than the same panels on rails.

The detailing

Integration systems vary, but the principles do not. Water arriving at the head of the array has to be taken over the top flashing and out to the sides without finding a way behind. Water running down the trays has to discharge onto the covering below the array, not under it. The underlay has to be lapped so that anything that does get past the covering still reaches the gutter.

Compatibility with the tile profile matters. A system designed around a flat interlocking tile will not weather neatly into a deep-profile pantile without additional soakers and thought. On slate, the courses and the lap dictate where the array edges can sit.

We set the array out against the tile courses and the rafter centres together. Getting one right and the other wrong produces either a cut-tile mess at the edges or fixings landing where there is nothing to fix into.

The temperature trade-off

Photovoltaic cells lose output as they heat up. A rail-mounted array has a ventilated gap behind it and sheds heat reasonably well. An integrated array has less room and less airflow, so it runs warmer and produces slightly less on hot days.

Good integration systems mitigate this with an air path from eaves to ridge behind the panels, and the difference over a year is small rather than dramatic. But it is a difference, and anyone telling you an integrated array performs identically to an on-roof one is not being straight with you.

Cost, honestly

In-roof on an existing sound roof costs more than on-roof for the same generation. You are paying for the integration system, for stripping and reinstating covering, for more time on the roof, and for the disposal of tiles that were doing no harm.

On a new build or re-roof the gap narrows considerably. If appearance is the driver and the roof is already open, it is often the better value option. If generation per pound is the driver and the roof is sound, on-roof usually wins.

We will tell you which situation you are in.