Following the loss of their 100 year-old houseboat to a fire, architect Michelle Lanker and her husband Bill Bloxom decided to design a modern replacement. Named Houseboat H, the high-end floating dwelling features significant environmentally-friendly design, including a burgeoning fish habitat.

Houseboat H is located on Lake Union, Seattle, and comprises a concrete hull, cement fiber board cladding, steel and wood framing, and spray foam insulation. It's topped by a curved roof.

Its most novel feature is hidden from sight under the water. The underside is covered in planters to create a fish habitat. In a neat addition, the basement has a window to allow observation of the water life, too.

"Made from recycled plastic material, the planters allow the roots of native plants to grow through and eventually extend into the water below, creating fish habitats," says a press release. "A large window in the basement float of the house allows observation of the fish inhabiting these islands."

The interior of the home looks relatively spacious. Its living room boasts generous glazing which offers views of the Seattle skyline, with even better views available upstairs in the master bedroom. Elsewhere lies a guest room with Murphy-style bed, a large bathroom, laundry room and a wine cellar.

Although the original houseboat structure was pretty much ruined by the fire, the century-old cedar logs that made it float were preserved. Lanker and Bloxom had them dried out and processed, and the wood now serves as the curved ceiling.

Like BIG's Urban Rigger, Houseboat H uses the water it floats on to help efficiently heat and cool it. The system functions similarly to a geothermal system, but uses water instead of the ground as a stable heat source.

"A titanium plate with an 800-ft [243-m] transfer fluid coil loop is attached to the west side of the deck structure and extends into the water to collect heat from the lake," the designers explain. "The lake water temperature stays at a pretty constant 45°F [7.2°C] during the winter at the 8-ft [2.4-m] depth the plate is submerged to. The 30°F [-1°C] minimum temperature of the transfer fluid in the loop is able to absorb this temperature differential to bring back to the heat exchanger in the mechanical room."

Additional energy-efficient tech includes a 5.32kW rooftop solar array, a green roof section and LED lighting. A water heater powered by the solar array provides hot water for household use and also runs the underfloor heating.

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