Solar Panels on New Homes: What to Check Before the Roof is Built

From 24 March 2027, new homes in England will in most cases have to include on-site renewable generation. The size and position of the array are settled long before the first tile is laid.

The Future Homes Standard was confirmed in a written statement to Parliament on 24 March 2026. The amending regulations come into force on 24 March 2027 and add a requirement for on-site renewable electricity. The government says solar panels will be installed in the majority of new homes. For roofers and specifiers, that puts an array on drawings that used to show only a covering.

A 12-month transition period applies. A building whose building control notice or plans are submitted before 24 March 2027 can still follow the current rules if work on it starts before 24 March 2028. The standard applies in England, and this article covers houses; the guidance treats blocks of flats separately. Wales, Scotland and Northern Ireland set their own building regulations.

What Does the Standard Ask of the Roof?

The legal test is for a reasonable output, given the building’s design and surroundings. Some buildings are exempt, including those with a storey 18 metres or more above ground. Approved Document L, the government’s guidance, describes how to meet the test.

One route is to design the system to reach at least the annual output of a reference array. The reference array is made of panels rated at 0.22 kWp per square metre. They cover an area equivalent to 40% of the home’s ground floor area, face south-east to south-west at a 45 degree pitch and have no overshading (Approved Document L). For a house with a 50 square metre ground floor, for example, that benchmark is 20 square metres of panels, or 4.4 kWp.

Where a roof cannot reach that output, the developer shows what an array covering the “reasonably practicable roof area” would produce and justifies that area to the building control body. Orientation and overshading are built into the output calculation. The government’s FAQ says a north-facing roof or heavy overshading is unlikely, on its own, to justify excluding a roof from that area.

Where Does the Array Meet the Rest of the Roof?

The reference array is a benchmark, but it still puts pressure on roof design. Three points follow.

• Roof features take up space. The guidance lists offsets from features such as vents and flues, windows, the ridge and the roof edge. They are measured to the edge of the panel and help size the usable roof area. Rooflights, vents and architectural features such as dormers and chimneys therefore reduce the area an array can use.
• Orientation, pitch and shading set the output. The reference array is idealised, so a less favourable roof needs more panel area or higher-rated panels. The guidance also suggests adjusting the position of vents or architectural features.
• Fixings and penetrations need detailing. Panels that sit on the covering and panels that replace part of it call for different details. Where the roofer and the solar installer are different firms, the drawing is where their work meets.

When Will a Roofer or Specifier Meet a Visualisation?

Developers and design teams use computer-generated images to market homes before they are built, and images also appear in planning submissions. Roofers and specifiers can be asked to price a job, approve a colour or confirm a covering from those images. If most new homes will carry panels, a view showing an unbroken plane of tile or slate no longer describes the building.

Studios that offer 3d architectural visualisation typically work from drawings or CAD files supplied by the client. The roof in an image can therefore only be as current as the drawings it was built from. Evermotion is a Polish studio that, by its own description, delivers architectural visualisation for architecture studios and property developers. It says one model can produce exteriors at different times of day and aerial views of a whole scheme. It adds that early previews let clients adjust views, materials and lighting before final rendering, and that the number of revision rounds is agreed in the quote. A preview is a natural point to check the array and its clearances, and to ask how a late change to the roof would be handled. A visualisation does not replace the roof drawings.

What Should You Check on a Roof Visualisation?

Ask for these at the preview stage, while changes can still be made within the agreed revision rounds.

1. Does the array appear at the size, position and orientation in the PV design, with clear space around rooflights, vents, chimneys and dormers?

2. Which revision of the roof plan and PV layout was the model built from, and is it the current one?

3. Is the covering the one specified, in the right colour, profile and finish? Treat screen colour as indicative and ask for the manufacturer’s reference or a physical sample.

4. Do the ridge, hips, verges, eaves and rainwater goods match the drawn details?