BIPV Products & Formats

The roof is BIPV's most established territory, and its products divide by grain - how small and discrete, or large and planar, the generating units are.

At the fine-grained end are solar tiles and solar shingles: small PV units, roughly the size and proportion of conventional roof tiles or slates, that lay up course by course to form the actual roof covering. Their appeal is visual and contextual - from the street a good solar-tile roof can read as an ordinary (if sleek) roof rather than a bolted-on array, which makes them attractive for houses, pitched roofs and heritage-sensitive or design-led contexts. Their honest costs are that many small units mean more joints, more fixings, more wiring interconnections and usually a higher price per watt and a fiddlier install and repair than large panels; a single failed shingle in a large field can be tedious to trace and replace.

At the coarse-grained end are in-roof panels and solar roofing systems: larger PV modules designed to sit flush within the roof plane - replacing a patch of tiles or metal roofing - rather than on racking above it. These recover some of the efficiency and lower cost of big panels while still integrating (the module is the roof over its area). A related family is standing-seam and metal-roof laminates, where thin-film or flexible PV is bonded directly onto or between metal roofing profiles, common on large industrial and commercial roofs.

For flat roofs, the characteristic product is the PV membrane: flexible photovoltaic material bonded to, or integrated into, a single-ply waterproofing membrane, so the same roll both waterproofs and generates - lightweight, low-profile, and useful where a structure cannot carry heavy racked arrays. Its trade-off is lower efficiency (usually thin-film) and generally a flat, sub-optimal angle. Across all roof formats the discipline is the same: the product must be a genuinely good roof first - shedding water, surviving decades, safe to walk or work near - and a generator second, and the binding weathertightness, structural and fire questions belong to the engineers, the manufacturers' certified details and the codes.

On the vertical envelope, BIPV products take over the language of the facade - cladding, rainscreen and curtain wall - and, most distinctively, the glass itself.

PV cladding panels are opaque (or semi-opaque) modules that replace conventional rainscreen or cladding boards on a facade. Typically a PV laminate on a backing, hung on the same kind of rails and brackets a stone, terracotta or metal rainscreen would use, they turn a large wall area into a generator while doing the cladding's job of shedding rain and finishing the surface. On tall buildings, where facade area vastly exceeds roof area, this is where BIPV's biggest opportunity lives - tempered by the honest fact that vertical surfaces receive less sun and are more shaded.

PV curtain-wall units integrate PV into the curtain-wall system itself - the glazed, framed skin of commercial buildings. Here PV can replace the spandrel (the opaque panels concealing floor slabs and services between vision glass) - an especially neat move, because spandrel is opaque anyway, so making it generate costs nothing in view or daylight - or it can replace vision glass with PV glazing.

PV glazing units are the seductive heart of facade BIPV: glass that is simultaneously the window and the generator. Cells (spaced crystalline, or a semi-transparent thin-film coating) are laminated between the panes of an insulated glazing unit, so the glass admits daylight and view while generating, and can also carry the insulation and solar-control performance a good window needs. This is where BIPV meets the interior, and where the aesthetics-and-transparency-versus-yield trade is sharpest: every bit of light let through is energy not converted, so the transparency is a designed compromise, not a free lunch (the whole of lesson 3.4). Facade and glazing products are almost always more bespoke, more expensive and more coordination-heavy than roof products - they sit in the building's most visible, most performance-critical, most liability-laden surface - so their weathertightness, structural, glazing-safety and electrical design defer firmly to the facade engineers, the manufacturers and the codes.

Cutting across every format is a single decision that shapes budget, programme and appearance more than any other: standard or custom?

Standard (catalogue) products are made in fixed sizes, colours and specifications, produced at volume, and bought much like any building product. Their advantages are real and often decisive: lower cost per watt, shorter lead times, proven and certified performance, established warranties, and easier replacement of a damaged unit years later. Their limitation is that the building must accommodate the product - its module sizes drive the setting-out, its available colours and transparencies constrain the look, and awkward edges and corners need filler or non-generating infill. For many projects, disciplining the design to a good standard product is the smart, honest choice, and it keeps BIPV closer to BAPV on cost.

Custom (made-to-order) products let the module become whatever the architecture needs - bespoke sizes to suit a setting-out grid, specific colours and finishes, chosen transparencies, curved or shaped units, particular cell layouts. This is what makes truly seamless, intentional solar architecture possible, and on a flagship or design-led facade it can be worth every rupee. The honest costs are steep: higher price (often much higher per watt), longer lead times, more engineering and coordination, smaller production runs with their own quality and warranty considerations, and harder future replacement of a one-off unit. A custom transparency or colour also usually generates less than a plain standard module.

The mature approach is to push standard as far as it will go and reach for custom only where it genuinely earns its place - where the visible architecture, a specific surface geometry, or a displaced premium material justifies the premium and the programme. A common and sensible hybrid is standard modules across the bulk of a surface with custom or infill pieces only at the edges and special conditions. As with everything in BIPV, judge it honestly against the cheaper alternative, and remember that manufacturers' minimum orders, lead times, certifications and warranties are binding project facts to confirm early, not assumptions to make late.

Whatever the format, a BIPV product is fundamentally a laminate that also seals a building, and understanding its construction and fixing keeps the designer honest about what integration really demands.

Most BIPV modules are built by lamination: the PV cells (or thin-film coating) are sealed between protective layers - typically front glass, an encapsulant that embeds the cells, and a back sheet or, very commonly in BIPV, a second sheet of glass (a glass-glass module, durable and suited to facades and overhead glazing). Wires are brought out to a junction box, and for architectural work the module can be given the size, edge treatment, colour and transparency the design needs. Glass-glass construction matters for BIPV because these elements are often overhead (canopies, skylights) or in the facade, where safety-in-breakage, durability and appearance all demand more than a standard back-sheet panel.

Mounting is where BIPV rejoins the building trades. A BIPV element is fixed to a real substructure - roof battens and underlay, curtain-wall transoms and mullions, rainscreen rails and brackets - exactly as the conventional element it replaces would be, and it must be weathertight at every joint and penetration, carry its own and environmental loads, and leave room for the electrical cabling and, ideally, an air gap behind it for ventilation (which both cools the modules, recovering some of the heat-related efficiency loss, and helps manage moisture). That ventilation gap is a recurring theme and a real design task, especially in hot climates.

This is precisely why BIPV is harder and its liabilities cross trades: the product must be procured, coordinated, fixed, sealed and wired as a building element and a generator at once, on site, by people who must understand both. The designer's job is to select the format and the standard-or-custom path, integrate it into the envelope, and detail the intent - while the binding structural fixing, weathertightness, glazing safety, fire behaviour and electrical connection defer to the qualified structural, facade and electrical engineers, the manufacturers' certified systems and details, and the governing codes and standards. Get the format right, respect what mounting it truly involves, and BIPV stops being a brochure image and becomes a buildable, honest piece of architecture.