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Denmark’s 300-yr-aged houses of the future

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Most summer days on the Danish island of Læsø, you are going to obtain Henning Johansen at function. A indigenous islander, Johansen is a thatcher. But on Læsø, a thatcher’s career is unlike any place else.

Nineteen kilometres off the north-east coastline of Jutland, the island appears in Norse mythology as the residence of the large Ægir, and, surrounded by shipwrecks, is mentioned in the course of Danish naval history. Læsø’s most unique attribute, on the other hand, is its houses, which are thatched with thick, heavy bundles of silvery seaweed.

Læsø is the only place in Denmark where eelgrass thatching can be found (Credit: Credit: Carstenbrandt/Getty Images)
Læsø is the only position in Denmark the place eelgrass thatching can be located (Credit score: Carstenbrandt/Getty Photographs)

Seaweed thatching began on Læsø in the 17th Century and is mainly distinctive to the island, nevertheless seaweed roofs had been later documented to have been witnessed on Scotland’s Orkney Islands. Læsø, which had a flourishing saltworks sector, experienced been deforested – trees were burned to feed the salt kilns – so islanders essential to discover an alternate roofing content. The island alone has scant means and, consisting mainly of mudflats and sandbanks, is tough to cultivate, so in its place inhabitants looked to the sea.

“People are often shocked for the reason that they are expecting it to odor or be slimy”

Driftwood was salvaged from shipwrecks to be used as timber and plentiful eelgrass (zostera marina) was dragged from the shore and harvested for the roofs. By the starting of the 20th Century, most of the island’s houses were roofed with seaweed. But, after a fungal disease wiped out a lot of the eelgrass in the 1920s, understanding of the strategy slowly and gradually vanished. These days, only 36 seaweed-roofed properties stay on the 1,800-human being island.

Because 2012, Johansen has been reviving the technique as he replaces the roofs, the 1st in a technology to do so. “It’s one particular of the biggest factors in Læsø’s record, so it is very significant for the island,” he informed me by phone from a roof he was operating on. “It was women’s work,” he added, explaining that since the male islanders were being frequently out at sea, the ladies ended up still left to look just after the farms and residences. “They ended up by yourself on this island and getting treatment of by themselves. They found a way to make these roofs, which is not found elsewhere in the entire world. So, of training course we are pretty happy of the heritage.”

Eelgrass is carbon neutral when harvested and used locally (Credit: Credit: Torstengrieger/Getty Images)
Eelgrass is a carbon neutral making product when harvested and made use of regionally (Credit score: Torstengrieger/Getty Illustrations or photos)

All-around 40 to 50 gals would get the job done on the roofs with each other. They would collect the seaweed immediately after autumn storms, then unfold it out on a area to dry for around 6 months, which would eliminate microalgae and make it rot resistant. When setting up started, they’d address the eelgrass pretty much as if it have been wool by twisting it into large vasks (ropes) then tying them to the rafters to serve as the base. Additional seaweed would be piled on top and weighed down with peat: the normal roof was a lot more than 1m thick and weighed 35 to 40 tonnes. The gals would choose chairs up onto the done roofs, the place they would sit and scan the treeless horizon for shipwrecks (and doable salvaging options) and move all around, even dance, on the seaweed to compress it.

They could make a roof in just one day, reported Johansen. For his crew of 5 regional thatchers, it usually takes close to 21. “Because I really do not have 50 females.”

But it’s not only for the sake of heritage that Johansen is reviving seaweed thatching. “[Eelgrass] is a pretty intriguing content,” he said, “because it will not burn there is so considerably salt in the straw.”

An average roof is more than 1m thick and weighs 35 to 40 tonnes (Credit: Credit: Hanspw/Getty Images)
An average roof is far more than 1m thick and weighs 35 to 40 tonnes (Credit: Hanspw/Getty Images)

When eelgrass is generally referred to as “seaweed”, it is essentially a type of seagrass, which has extended leaves and can increase up to 2m in duration. It’s identified all about the world, nevertheless largely in the northern hemisphere. Not only is eelgrass by natural means hearth-, rot- and pest-resistant, it also absorbs CO2, and as it doesn’t require warmth to produce, is carbon neutral when harvested and utilised regionally.

Eelgrass becomes completely water-proof right after about a yr and has insulation houses equivalent to those people of mineral wool, a dense, fibrous materials produced from molten glass, stone or industrial squander. A roof can very last hundreds of several years – just one of island’s remaining seaweed roofs dates additional than 300 several years – for comparison, a concrete tile roof generally lasts around 50.

This mix of sustainability and heritage caught the eye of Copenhagen-centered American architect Kathryn Larsen, who is presently looking into how Læsø’s traditional seaweed thatching could be current into a sustainable modern building material all around the globe.

Though studying at KEA – Copenhagen Faculty of Design and Engineering, Larsen targeted her thesis on Læsø’s seaweed roofs, a topic with several English-language assets. “It became this significant secret for me because almost all the information and facts was in Danish,” she mentioned. “I was actually consumed by that for a couple years: I would study much more Danish and then I would master additional about this and go back again and forth. It turned a real obsession.”

Since Læsø has few resources, islanders had to look to the sea for their building materials (Credit: Credit: Torstengrieger/Getty Images)
Due to the fact Læsø has few methods, islanders experienced to search to the sea for their making components (Credit history: Torstengrieger/Getty Visuals)

Just after finding that her faculty had a supply of eelgrass, which it had acquired from area seaweed farmers, Larsen started out experimenting “for fun”. She developed prefabricated panels to be utilised on facades and roofs to act as supplementary, sustainable insulation and put in the panels on the roof of her faculty to research how eelgrass reacts above time to the things.

“In 50 decades all the understanding about eelgrass disappeared,” Larsen claimed.

She before long realised, nonetheless, that she necessary to generate a a lot more community set up. “A lot of people were seriously sceptical,” she mentioned about the use of eelgrass. In late 2019 she begun operate on The Seaweed Pavilion, an set up incorporating her panels into a wood construction in a courtyard at KEA. “I wished individuals to be able to sit beneath it and practical experience this material in individual. People today are often shocked for the reason that they are expecting it to scent or be slimy, so by getting a far more positive conversation with it, I was hoping to modify that notion.”

“What I definitely required to push dwelling was that this is a actually great type of purely natural installation,” she mentioned, outlining that with this style of installation you don’t require a vapour barrier, which is not air permeable. “You can use a good deal of it and air will go as a result of your constructing and not get blocked, so the entire building will breathe and the air high quality will be a large amount larger.”

A roof made of eelgrass can last for hundreds of years (Credit: Credit: Torstengrieger/Getty Images)
A roof produced of eelgrass can past for hundreds of several years (Credit rating: Torstengrieger/Getty Visuals)

Larsen desires to improve the way the constructing industry appears at older tactics, which ended up “not only improved for our atmosphere, by utilizing natural renewable sources, but had been also building structures that were a great deal much healthier for us. Mainly, we figured it out, [then] we dropped all this information and [now] we’re setting up ourselves into a even bigger gap where by buildings are having even worse and worse in air high quality.”

Simply because eelgrass grows globally, she sees a large world wide potential for it to be used as a sustainable making material, “as prolonged as it is harvested and employed locally”.

The eelgrass that she employed in The Seaweed Pavilion was harvested and prepared by Kurt Schierup, who works by using the identical farming and drying system as individuals of Læsø’s women of all ages, albeit with a equipment alternatively than by hand. While he proven his eelgrass harvesting organization, Møn Tang, in 2016, Schierup has been undertaking this function because his childhood in the 1950s on the Danish island of Tærø, when eelgrass was exported internationally for use in upholstery, insulation and mattresses. It is a nugget of background that underscores how widespread a materials eelgrass utilised to be.

Today, only 36 seaweed-roofed houses are left on the island of Læsø (Credit: Credit: Thomas Kyhn Rovsing Hjørnet/Alamy)
These days, only 36 seaweed-roofed properties are left on the island (Credit: Thomas Kyhn Rovsing Hjørnet/Alamy)

“When I was a child, 50 yrs in the past,” reported Johansen, “everybody was sleeping on eelgrass in Denmark. But then the plastic arrived, pretty low-priced. So, in 50 yrs all the understanding about eelgrass disappeared”.

On Læsø, Johansen continue to has 10 extra roofs to change. It’s been a long project, but just one that he claims he does not want to complete “because it is much simpler to inform you the heritage when you appear and see me fix outdated houses”. People to Læsø are invited to check out him at operate on weekdays all through the summertime where they can see very first-hand “the way it operates, the product, and how intriguing it is”.

Eelgrass is portion of the world’s heritage, he mentioned. “You can come to Læsø and I can exhibit you your individual record from your country” because it was when usually applied close to the planet – everywhere from the Dutch Wadden Sea in which it was used for building sea walls to New England where homes were insulated with Cabot’s Quilt, a thermal and sound insulator manufactured of dried eelgrass.

“It has a massive record, which was pretty rapidly overlooked and now I’m starting up to notify it all over again. It is really effortless to notify when you stand beside a incredibly outdated roof, wanting at it, and people today say, ‘what a amusing material’.”



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