On a house, a solar shading overhang, also called a brise-soleil overhang or brise-soleil canopy, is a horizontal canopy above an opening, and the French 3CL-DPE 2021 method models it as the near-shading class « baie sous un balcon ou auvent ». The factor there depends on projection alone: 0.8 below 1 m, 0.6 between 1 and 2 m, 0.5 between 2 and 3 m, 0.4 from 3 m up, with no orientation split. The geometry, on the other hand, is in no table: the projection that fully shades a 2.15 m opening at solar noon on the summer solstice runs from 1.09 m in Plymouth to 1.37 m in Edinburgh, and that same projection leaves only 0.26 to 0.32 m of shadow on the head of the opening at the winter solstice, 12 to 15% of its height. That ratio, and not a promise of comfort, is what stands up in front of a client and in front of a cheaper quote.
Brise-soleil overhang: what the term covers on a house and on a building
An overhang is a fixed, horizontal projection above one or more openings, solid or louvred, that cuts out the high summer sun and lets the low winter sun in. Unlike a pergola, it has no posts, and unlike adjustable brise-soleil, nothing moves. It is the simplest of all solar protections and one of the four principles of bioclimatic design: capture in winter, protect in summer.
| Form | Where you find it | Usual projection |
|---|---|---|
| Window overhang | small canopy added above a window or a French door, in retrofit | 0.40 to 0.80 m |
| Continuous band on a modern house | slab or box section running above a row of openings, often concrete or aluminium | 0.80 to 1.50 m |
| Louvred overhang | fixed horizontal aluminium or timber louvres that filter the light rather than block it | 0.60 to 1.20 m |
| Building overhang | cantilevered slab at each floor of a block or commercial building, sometimes extended into a walkway | 1.00 to 2.00 m |
The overhang on a modern house, the band that underlines the openings of a contemporary façade, protects if it has been sized, and only shades the head of the glazing if it was shortened to keep a slim line. Unlike glazing with a reduced solar factor, it does not cut winter gains.
What a solar shading overhang is worth in the assessment, and under what name
The near-shading class and its factor table
The 3CL method has no word for overhang. It has four families of near-shading obstruction, and a horizontal projection above an opening falls under « baie sous un balcon ou auvent ». The table is short and not open to interpretation.
| Near-shading recorded | Projection | Orientation | Factor |
|---|---|---|---|
| Opening under a balcony or canopy | under 1 m | all | 0.80 |
| Opening under a balcony or canopy | 1 to 2 m | all | 0.60 |
| Opening under a balcony or canopy | 2 to 3 m | all | 0.50 |
| Opening under a balcony or canopy | 3 m and over | all | 0.40 |
| Opening at the back of a balcony or loggia | under 1 m | South | 0.50 |
| Opening at the back of a balcony or loggia | 3 m and over | South | 0.20 |
| No near shading | not applicable | all | 1.00 |
Two lessons for pricing. The first step is the profitable one: going from nothing to 1 m of projection takes the factor from 1.00 to 0.60, that is 40% less solar gain, while going from 2 to 3 m only removes another ten points. And the table gives no credit for orientation on a canopy, unlike a recessed balcony: a north-facing overhang scores like a south-facing one, which is a limit of the method and not a selling point.
Near times distant, or why an overhang never works alone
The sunlight factor of an opening is the product of the near obstruction and the distant one. A 1.20 m overhang in front of an opening already blocked by a neighbouring wall stacks both coefficients, and the calculation turns pessimistic on winter gains fast. On a fully open façade, by contrast, the overhang carries the whole effect on its own. The distant obstruction is surveyed separately, and how shading enters the assessment calculation is worth checking before you conclude anything about the gain.
What you record on the survey to hold the entry under audit
Three dimensions are enough, and all three are needed. The projection in horizontal terms, measured from the outer face of the glazing to the nose of the overhang. The height from the nose of the overhang to the head of the glazing, which pushes the shadow line down and which the table ignores but the building does not. The orientation of the opening on a compass, for the rest of the calculation. A photo from outside with a tape open in shot beats a round number typed from memory.
Sizing a brise-soleil overhang: solar geometry, not the supplier's catalogue
The simple rule: projection = height to shade ÷ tan(sun altitude)
At solar noon on 21 June, the sun's altitude is 90° minus the latitude, plus 23.44° (minus 23.44° on 21 December). The projection is the height to shade, from the nose of the overhang to the bottom of the glazing, divided by the tangent of that angle.
Worked example in London (51.5° N, sun at 61.9° on 21 June, tangent 1.87):
- A 1.25 m window, overhang level with the head: 1.25 ÷ 1.87 = 0.67 m of projection.
- A 2.15 m opening, overhang set 0.30 m above the head: 2.45 m to shade, so 2.45 ÷ 1.87 = 1.31 m of projection.
- On 21 December, sun at 15.1° (tangent 0.27): the shadow of that 1.31 m overhang drops 0.35 m below its nose, so barely 0.05 m onto the glazing.
Lifting the overhang above the head means making it deeper, but it keeps the same shade in June and frees almost all the glazing in winter. Two corrections complete the rule: extend the overhang past each side of the opening by about half the projection, or the sun comes in at an angle from the sides; and record the façade's actual orientation. The orientation of the building therefore decides the overhang before any calculation.
The projection that shades the opening at the solstice, latitude by latitude
Applied to a common 2.15 m opening with the nose of the overhang level with the head, the same rule gives figures that vary by a quarter across the country.
| City | Latitude | Sun altitude on 21 June | Projection to shade 2.15 m | Sun altitude on 21 December | Shadow left on the opening on 21 December |
|---|---|---|---|---|---|
| Edinburgh | 55.9° N | 57.5° | 1.37 m | 10.6° | 0.26 m |
| Manchester | 53.5° N | 60.0° | 1.24 m | 13.1° | 0.29 m |
| Birmingham | 52.5° N | 61.0° | 1.19 m | 14.1° | 0.30 m |
| London | 51.5° N | 61.9° | 1.15 m | 15.1° | 0.31 m |
| Plymouth | 50.4° N | 63.1° | 1.09 m | 16.2° | 0.32 m |
Cross that with the factor table and the reading is clear. Everywhere in the UK the geometrically correct projection sits between 1.09 and 1.37 m, that is above the first threshold, so a correctly sized overhang lands in the 0.60 band rather than the 0.80 one. Northern latitudes pay for that in depth: Edinburgh needs a quarter more projection than Plymouth for the same shadow, which is a structural cost, not a detail of the finish.
What that same projection costs in winter gains
The standard client objection is that you are taking January sun away. The arithmetic answers it. At the projection above, the shadow on the opening at noon on 21 December stays within 0.26 to 0.32 m whatever the city, 12 to 15% of the height of a 2.15 m opening, and it falls on the head of the glazing, the part that lights the back of the room but does not warm the storage surfaces. So the ratio is roughly one to seven between what you cut in June and what you lose in December. That is the one sentence in this article that argues itself in a meeting.
East and west: where a horizontal projection stops working
Facing south, the sun's altitude differs by more than 46° between the two solstices, and that difference is what the overhang exploits. East and west, the sun that causes the problem is low on the horizon early and late in the day, whatever the month: a 1 m horizontal projection cuts almost nothing there, and the factor table still awards it the same 0.60. The answer is vertical, side fins or adjustable brise-soleil, and the client should hear it rather than buy an overhang that will never work.
Where the overhang belongs in the works programme
Its rank against insulation and ventilation
An overhang acts on solar gains, not on fabric heat loss: it does not move the EPC band and it opens no grant. So it is proposed after the fabric and the ventilation, and justified opening by opening rather than dwelling by dwelling. On a well-insulated post-1975 house, large south-facing openings are often the first overheating source, ahead of the roof, and the measure moves up the list. The full list of passive measures to work through before any cooling is there to place the overhang in that order, not to force it in.
House, block, commercial: what changes on the quote
On a house, an overhang is a façade element: structural fixing, weathering, finish, and a line for scaffold or a platform that often costs as much as the profiles. In a block, the façade is common structure and the works go through the freeholder, which moves the signature by a year or two. In commercial work, the glazed area changes the scale: wind loads become the governing case, a structural calculation is expected, and maintenance goes into a contract. Those three cases do not price at the same rate per linear metre.
The protections to pair it with, by exposure
An overhang on its own answers one orientation and one time of day. The rest is made up elsewhere.
- Adjustable brise-soleil on east and west façades, where the sun is low.
- External blinds and shutters, which work in front of the glazing rather than above it.
- Roof overhangs and pergolas where the existing geometry allows an extension.
- Deciduous planting, which shades in August and lets light through in January.
Installation: what your liability cover answers for
Concrete, aluminium louvres, timber: choosing the material
| Material | Weight | Light under the overhang | Typical use |
|---|---|---|---|
| Cast or precast concrete | heavy, structural fixing required | full shade | new build, modern house, blocks |
| Solid aluminium, box or folded sheet | light | full shade | retrofit, façade under external insulation |
| Fixed aluminium louvres | light | filtered shade, diffuse light kept | living-room openings, commercial |
| Solid or glulam timber, louvred | medium | filtered shade | timber-frame house, clad façade |
On an existing house, aluminium louvres are the most common choice: light, fixed on brackets, they keep the room bright.
Powder-coated aluminium remains the standard for its weight and stability, provided galvanic couples with steel, copper or stainless are separated, particularly in a marine atmosphere. Steel needs hot-dip galvanising and systematic touch-up on cut edges, or corrosion starts at the cut. Timber calls for a use class that matches the exposure and a design that does not hold water. Concrete is robust but heavy: loads, cracking and the drip edge all need checking before you propose it in a retrofit.
Fixings and getting through external wall insulation
The fixing goes into the structural substrate, never into the insulation. On solid masonry, an anchor or a resin fixing depending on the embedment available. Through external wall insulation, set-out brackets or thermally broken plates sized for the site's wind and snow loads, with weathering returned to the breather membrane: this is where thermal bridges at junctions and water paths are manufactured. The constraints specific to an insulated substrate are set out in our article on external wall insulation.
- Pre-drilling and packing, so the insulation is not crushed under the plate.
- Insulating washers between dissimilar metals, standard on the coast.
- Seals compatible with UV and differential movement, replaced under the maintenance contract.
Fitting an overhang to an existing house: planning and consents
An added overhang changes the external appearance of the façade. On a house it can often go ahead without a planning application, but a conservation area, an article 4 direction or a listed building (listed building consent) changes that, and the local planning authority is the one to ask before ordering. Local policy may limit the depth of projections, their colour and their material. Cantilevered, it usually adds no footprint; on posts, the authority may treat it as a covered pergola. In a block of flats, the freeholder signs off before any order.
Water, corrosion and the sheets that belong in the O&M manual
A fall to the outside, a drip that throws the water clear of the façade, no standing point anywhere: that is the trio that decides how long the element lasts. Stainless fixings are chosen compatible with the profile, not to the shortest lead time. On the paperwork side, the O&M manual takes the load calculation, the fixing detail signed off by the supplier, the third-party approval where one exists and the exact references of the profiles installed. When a claim lands, that bundle answers instead of the contractor.
Holding your price against a cheaper quote
How much a fitted brise-soleil overhang costs
Market orders of magnitude, excluding VAT, supplied and fitted, for a projection of about 1 m, excluding access: only a quote after a survey sets the price.
| Type of overhang | Order of magnitude per linear metre | What makes it vary |
|---|---|---|
| Solid aluminium or louvred timber | £250 to £600 | girth, species or powder coating, soffit |
| Fixed aluminium louvres on brackets | £350 to £800 | number of louvres, thermally broken brackets through insulation |
| Added precast concrete | £600 to £1,300 | lifting, structural fixing, load calculation |
For an opening 2.40 m wide extended by 0.50 m on each side, so 3.40 linear metres of aluminium louvres, that puts the element between £1,200 and £2,700 excluding VAT, with scaffold or a platform on top. Do not count on a grant to bring it down: an overhang is not a fabric or heating measure and is not funded as a stand-alone measure.
What you can demonstrate, and what you must not promise
What you can demonstrate: the projection chosen, the sun's altitude at the latitude of the site, the shading factor that follows, the exact period during which the opening is shaded. What you must not promise: an internal temperature, a number of degrees gained, a substitute for cooling. An overhang treats neither internal gains, nor thermal mass, nor night ventilation, and a dwelling with no scope for night purge ventilation will stay hot in spite of it. Saying so up front is what separates a technical offer from a sales one, and the Confort d'été tool, which simulates a house's warm season at its address, helps place the weight of the openings among the other measures.
What goes on the quote
The line gets itemised: projection in horizontal terms, girth and material of the profile, fixing method and number of brackets, weathering, soffit finish. The soffit deserves its own mention, because a light colour bounces light into the room and produces glare late in the day, which turns into a dispute if nobody wrote it down. Access equipment goes on a separate line. A quote carrying those five lines no longer compares to the competitor's lump sum.
Which opening to start with
Start with one to three openings, the ones that combine a large glazed area, a south or south-west orientation and a living space used in the afternoon. That assumes you have the inventory: Argile's AI picks out the openings on each façade and works out their areas, which gives you the list to sort by orientation before the survey even happens. The remaining openings go in as a priced option, which leaves the client a decision to make rather than a price to accept.
