Understand
The façade is the forgotten lever of energy retrofit.
We insulate walls, we replace boilers — and we look away from what exchanges the most energy with the outside: the glazed opening. This page explains why, and what can be done with it.
The weak point of the pre-1990 stock.
Multi-family and office buildings built before 1990 make up the core of the European stock, and their façades concentrate the problem: for the same area, a window loses several times more heat than a wall in winter, and lets radiation in unfiltered in summer. Energy retrofit tackles walls, roofs and heating systems; the glazed opening is usually addressed by replacing the frames, nothing more.
Yet replacing a window improves its insulation, not its intelligence. The new window experiences the sun exactly like the old one: too little used in winter, too present in summer.
Summer comfort becomes the issue.
Heatwaves have turned overheating into a health and regulatory issue: energy performance certificates now assess summer comfort, and consumption targets are hard to meet with air conditioning. Cooling costs energy; keeping the heat out costs almost none.
Movable solar protection — shutters, blinds, louvres — is the most effective tool against overheating, because it stops radiation before the glass. It is documented, it is standardised, and it is massively under-deployed on the existing stock.
What a shutter can do — and what it cannot.
A conventional motorised shutter protects in summer and insulates a little at night. But it can do nothing with the winter sun: closed, it blocks it; open, it lets it warm the room for a few hours, nothing more.
That asymmetry is what Kelveen corrects. The same shutter tilts to send winter radiation back indoors, presses against the opening to reinforce night-time insulation, deploys to protect from summer overheating, and exposes a photovoltaic face when the opening is free. Four uses, one installation — on the existing opening, no structural work, reversible, in occupied buildings.
What it changes, and how we measure it.
All our results are computed, not measured: hour-by-hour simulation over a full weather year, cross-checked with a second independent tool. The orders of magnitude — heating avoided, overheating reduced, electricity produced — are shown on the home page and detailed by Albedo, our simulator.
The first equipped building will turn these calculations into measurements. That is the current step: a test rig is in fabrication, and a first pilot site is being sought.