• In Cosswiller, in the Bas-Rhin, a house stands out.

    This is where Eric Wasser installed his “heliodome”.

  • Its “solar house” follows the trajectories of the star, which allows it to be heated at a constant temperature all year round.

  • “In summer, the sun is much higher and does not come in.

    This is the case for four months.

    For four more, it is low and warms us.

    And twice a year for two months, it switches from its summer position to that of winter, or vice versa.

    We follow the trajectories of the sun according to the seasons”, explains the Alsatian.

A small road in the middle of the Alsatian countryside, half an hour west of Strasbourg.

A village with colorful houses here, half-timbered or more modern ones there… And suddenly, a building with an unexpected look.

A few hundred meters before entering Cosswiller (Bas-Rhin), the upper part of the “heliodome” is already visible.

A sign soon indicates its exact location, a little lost next to a farm.

It is here, on family land “since 1680”, that Éric Wasser completed the construction of his “solar house” in 2010.

Up close, it looks like a spinning top, or a fan, as you choose.

With, on one side, this structure composed of a large glass roof of 160 m² delimited by steel bars and on the other, a wooden roof divided by skylights and a terrace.

All for a height of about 10 meters.


"Today, we always want to solve a problem with a new technology, never with architecture", says this trained cabinetmaker, looking like Geo Trouvetou.

His invention is the result of a long process for the sexagenarian.

“I had the idea when I was a student, but I was far from all that, he recalls.

I have always been drawn to geometry and the sun.

It was just logical to come to this, the Greeks were already building whole cities well oriented.

»

He wanted his construction to “follow the trajectories of the sun” So he studied them at length.

“In 1992, I found a book that gave me the angles for every hour of the day over a year.

I had to translate it with a mathematician friend.

To arrive, six years later at… “a paper casserole dish”.

A first model before filing for a patent in 2000 and above all winning the Lépine competition in 2003.

A real boost for his project?

Yes and no because Éric Wasser then struggled for a long time with funding.

“In Switzerland, I was offered to cover it 100%.

But like a good Alsatian, I stayed here”, laughs the one who was also best worker in France at 25 years old.

An energy-efficient house

In 2009, the slab of his “heliodome” was cast on the family land, and work on this prototype was completed the following year.

“We've been in it for a little over twelve years now,” sums up the former designer, who lives with his glass artist wife.

The two also open their house widely, where the works of each are exhibited and for sale on the ground floor and on the first floor.

Only the third and last is fully reserved for them, with a small sleeping area.


The interior is bathed in light.

Not illogical given the glass roof… This September morning, the weather is good.

A little over 20°C but hardly more, despite the reflecting sun.

“We have this temperature pretty much all year round,” assures the owner, who uses very few means of heating.

“Yes, I have a small stove in the basement and I have to spend 3 cubic meters a year”… that's almost nothing for 200 m² of living space!

This is indeed one of the main attractions of its “solar house”: it does not consume energy at all.

Thanks to its structure, its orientation and its insulation (“wood wool but I would put straw today”), the temperature is almost constant.

Even in summer, when the mercury rises very high.

“In summer, the sun is much higher and does not come in.

This is the case for four months.

For four more, it is low and warms us.

And twice a year for two months, it switches from its summer position to that of winter, or vice versa.

We follow the trajectories of the sun according to the seasons.

»


His concept has won over a few families.

Very little.

Perhaps the cost: “That of a beautiful house, I would say around 3,500 euros/m² today”.

A dozen constructions with the same principles have emerged “in Switzerland, Germany and the rest in the Grand-Est.

At the moment, we have about twenty projects in progress”, further details Éric Wasser, who has teamed up with a promoter in order to make the “heliodome” better known.

Especially given the period and the soaring costs of fuel, gas, electricity, wood too...

"It's time to build less energy-intensive buildings rather than thinking about reducing its consumption", pleads the one who refuses the qualifier of architect.

“No, it's nature.

»

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