Perrette

The name

Perrette comes from Perret.

Auguste Perret rebuilt Le Havre after the war — quickly, and well, which nobody expected to be possible at the same time. The name is a debt. What was taken from him is not a style but a working method, and it shows up in three places.

Le Havre

Rebuilt fast. Rebuilt well.

The centre of Le Havre was destroyed in September 1944 — the port, the housing, most of what stood between them. The reconstruction that followed is the part worth studying. It was designed as one system rather than a thousand buildings, delivered at a speed that should have produced barracks, and it produced a city centre that UNESCO added to the World Heritage list in 2005.

Perret's team did not get there by drawing everything. They fixed a very small number of rules and let everything else vary underneath them. That is the whole idea, and it is why a simulation platform carries the name: the constraint is what makes the speed possible, and the speed is what makes the constraint worth accepting.

A city is a set of voids surrounded by solids.

« Une ville est un ensemble de vides entourés de pleins. » — Auguste Perret

Three motifs

What is actually built into the name.

The module

One number for a whole city.

The reconstruction sits on a single structural grid: 6.24 m, about 20 ft 6 in. One number for an entire city centre — the apartment blocks, the shops, the town hall, the church. It set the column spacing, and through the column spacing it set the room widths, the window rhythm, the fabrication and the cost.

What it did not set is what the bays are filled with. Walk the streets and no two façades are the same. The module is invariant; the composition is not. A single grammar, and no repetition anyone notices.

Figure 1. The grid is fixed and the infill is free. Constraint is what made the variation affordable, not what prevented it. Schematic.

The frame

The structure is the façade.

Perret built in poteau-poutre — a reinforced concrete post-and-beam frame — and the frame is not hidden behind anything. It is the elevation. The infill sits in the plane of the structure rather than in front of it, and the joints are shown rather than covered.

The consequence is that the building can be read from the pavement. Nothing about how it stands up is a secret, and nothing is dressed up as something it is not. That is a harder discipline than it sounds: it means the structure has to be worth looking at, because there is no second skin to hide behind.

Figure 2. Plan cut through a façade. On the right the two lines have become one, which is the whole of it. Schematic.

The lantern

Glass sorted by which way it faces.

The tower of Saint-Joseph is a lantern: an octagonal shaft carrying 12,768 pieces of coloured glass, designed by Marguerite Huré. Perret did not live to see it finished.

The colours are not distributed for pattern. They are distributed by orientation — seven colours, allotted according to which way each facet faces, and therefore according to what light will arrive on it, at what hour and in what season. The building is one object; the glass is a function of azimuth.

That is a design decision taken on exactly the variable an energy model is built around. Huré was treating orientation as the project variable decades before anyone fitted a response surface to one — and the mark at the top of every page is that same plan. Not an ornament lifted off the tower: she sorted the glass by orientation, we sort the analysis by domain, and both of us arrive at eight.

Figure 3. The mark is not an ornament lifted off the tower: it is the lantern in plan, one facet at a time. Huré sorted the glass by orientation and we sort the analysis by domain — the eight colours keep their fixed order and their meaning, here as everywhere else on the site.

The debt

What we took from it.

Fast and well are not opposites

The reconstruction is the proof, provided the rules are settled first. An answer available inside a design meeting is worth more than a better answer three weeks later — but only when the method behind it is fixed, stated, and the same every time.

One module, endless variation

6.24 m did not make the city monotonous. It made variation cheap. Fitting one function per model does the same thing to an energy study: settle the structure once, and every question after that costs a millisecond instead of a run.

Nothing hides behind a skin

Nothing about how a Perret building stands up is concealed. Nothing about how a result here was produced is either: the assumptions, the resolution, the engine version and the refusals travel with the number, in the same place as the number.

Orientation is a project variable

Huré sorted 12,768 pieces of glass by which way they face. Orientation is still the first variable of any energy study, and still the one most often handed to a model as a single raw angle — the one encoding guaranteed to misread it.