Most solar on most buildings is an addition. The building is finished, the roof is there, and an array is fixed on top of it. It works, it generates, it pays for itself, and it was never part of the design. For the overwhelming majority of commercial roofs in Sri Lanka that is the correct answer and there is no reason to complicate it.
Building-integrated solar is a different proposition. Instead of adding a generating surface to the building, you replace a building element with one. The canopy, the skylight, the facade panel, the roof sheet itself becomes the thing that generates. The industry calls it BIPV. The distinction is not marketing: in a conventional installation you could remove the array and still have a complete building, and in an integrated one you could not.
What this actually looks like
The clearest example is a roof you can stand under. A pergola over a terrace, built as a proper architectural roof — structurally sound, fully waterproof, designed to be seen from below — in which the modules are the roofing material. There is no roof sheet underneath. The glass is the roof.
That changes the specification of almost everything. The module has to survive wind loading as a building element rather than as a panel bolted to one, which usually means thicker glass. It has to be watertight at every joint, which is a facade problem rather than an electrical one. It has to fit a dimension the architect has set, which is the part that most often breaks the project — standard modules come in standard sizes, and a drawing with a set rhythm to it rarely happens to land on them.
At that point there are two options. Change the architecture to suit the catalogue, or have the part made. The second is possible — specialist manufacturers will produce modules in non-standard dimensions with the glass specified for the application — and it is how integrated projects that keep the architect’s intent actually get built.
What it costs you
Honesty is more useful here than enthusiasm, so: integrated solar costs more per kilowatt than conventional rooftop solar, and it generates less.
It costs more because the parts are made rather than bought, because the engineering hours per kilowatt are higher, and because a waterproof structural roof is a more demanding thing to build than a mounting frame. It often generates less because the orientation and tilt are set by the architecture rather than by the sun — a facade is vertical, a pergola sits where the terrace wanted it, and neither is the angle you would choose if generation were the only consideration.
Anyone who tells you otherwise is selling. The case for integrated solar is not that it beats conventional solar on cost per unit. It is that it is available where conventional solar is not.
When it is worth it
Three situations, in our experience, are the ones that justify it.
The building has run out of roof. A tall building has the same footprint as a low one and many times the consumption. Once the roof is fully used, the only surface left is vertical, and a facade that generates is better than a facade that does not — even at a worse angle.
The element has to exist anyway. If the design already calls for a canopy, a pergola, a skylight or a shading louvre, then part of the cost is already committed. You are paying the difference between a non-generating element and a generating one, which is a much smaller number than the cost of the whole installation.
The building is making an argument. Some buildings are built to say something about the organisation inside them. A visible integrated system does that in a way a roof array cannot, because nobody on the ground can see a roof array.
When it is not
If you have unshaded roof space you are not using, use it. Conventional rooftop solar on available roof will beat integrated solar on every financial measure, and a consultant who steers you towards integration when you have a clear warehouse roof is not acting in your interest.
If the building is already finished, the moment has largely passed. Integrated solar works by displacing something — a roof sheet, a facade panel, a canopy — and on a completed building there is nothing left to displace. What remains available is a conventional system, which is usually the right recommendation anyway.
The one thing that determines whether it is possible
Timing. Integrated solar is decided at design stage or it is not decided at all.
That is the single most useful thing to take away from this article. It is free to ask the question while the drawing is still open — an hour with an engineer and a conversation about whether any element in the design could reasonably generate. Asked after the facade is specified and the roof is closed, the answer is almost always no, and it is no for reasons that have nothing to do with solar.
First Energy has built integrated systems in Sri Lanka, including a fully waterproof architectural pergola roof at the top of a commercial tower in Colombo, using modules made to sizes no mainstream supplier carries. It is one of the smaller systems we have built. It is the one we are asked about most.
If you are designing a building and you want to know whether any part of it could generate, ask while it is still a drawing. First Energy SL (Pvt) Ltd — Performance. Quality. Care.