A metal pool ladder is fixed to a wooden veranda outside Jan-Erik Andersson’s house in western Finland. But there is no pool here, and we are 1,000 feet from the sea. The steps to nowhere, says Mr. Andersson, are a provocation, “an artwork to protest about rising waters.”

“We are waiting for our pool,” he adds. “It will not be long. The world is burning.”

More unsettling visual jokes about imminent environmental catastrophe turn up all over his hexagonal home, known as the Spruce House. But Mr. Andersson, an artist, designer and performer, can’t help but envelop them in the beauty that he sees all around the natural world. He’s an optimist, after all.

The Spruce House, newly built on a semirural plot on the island of Hirvensalo, in Finland’s Turku archipelago, resembles a wicked-green wooden head, perhaps some kind of Nordic folk-horror goblin. Its mossy green roof is a misshapen hat, its scarlet door an abstracted bloody mouth, its narrow windows a pair of malevolent eyes.

It is built to high environmental standards, and heated and cooled by geothermal energy, but these technicalities aren’t really what interest its creator. “There are many houses, many architects dealing with purely ecological problems,” he says. “This house is really about symbols, what art can do, and what houses should be. In my opinion, there should be more art interventions.”