A curtain wall enquiry looks like a large version of a normal glazing job and behaves nothing like one. The panes are bigger, the frames are engineered rather than fabricated, the units move with wind and temperature, and the access is a project in itself. Most of the problems on these jobs are decided before anyone opens a roll of film.
Start with the unit, not the elevation
A curtain wall is a sealed unit in an aluminium grid, usually with a drained and ventilated cavity behind the glazing. Two facts about that assembly decide whether an interior film is viable: the position of any low-E coating, and the depth of the rebate.
If the coating is on the second or third surface — inside the cavity — the film can be applied to the internal face without touching it. If the coating is on the internal surface itself, an interior film goes on top of it, and the thermal behaviour of the unit changes in a way that has to be assessed rather than assumed.
The rebate matters for a different reason. Deep rebates limit how much of the glass edge an installer can reach, which affects trimming and edge sealing. On a shallow rebate the film can be worked into the frame; on a deep one it stops at the sight line, and the client should know that before the job starts.
Access is usually the deciding cost
Interior access on a curtain wall means working at height behind the facade, often over a finished floor, sometimes over occupied desks. That drives three costs that have nothing to do with film: access equipment, out-of-hours labour, and protection of the interior.
Where interior access is impossible or unacceptable, an exterior film changes the economics. The work moves outside, the building stays in use, and the film rejects solar energy before it enters the assembly rather than after. The trade-off is a shorter service life and a hard dependence on edge sealing.
The wrong answer is to assume exterior is expensive and interior is cheap. On an occupied tower, exterior work from a suspended platform is frequently the cheaper and faster route — and it is the only route when there is no interior access at all.
Movement, and why edges lift
Curtain wall units deflect under wind load and expand thermally. The film moves with the glass, but the frame does not, so the perimeter is worked continuously. That is why edge lift shows up first on tall buildings and on elevations with large temperature swings.
Two things reduce it: a proper edge seal, and leaving the specified gap at the frame rather than trimming tight. Neither is expensive. Both are routinely skipped on projects where the film was priced as if it were a shopfront.
Sequencing with the rest of the build
Film on a curtain wall should follow the wet trades and the facade cleaning, and precede the interior fit-out. On a new build that window is narrow. On a refurbishment in occupation, the work is usually phased by floor, which is also the best way to manage the client relationship — one floor visible, then a decision, then the rest.
Ask for the facade cleaning schedule before quoting. Film applied to glass that is about to be cleaned with a scouring pad and a scraper is film that will be replaced.
What to send us
Elevation drawings with pane sizes, the unit construction including coating position, the floor count and access method, and the required outcome — heat, glare, or both. With those four, a quotation is a specification. Without them, it is a range and a list of questions.
