Lahti builder designs home for a changing climate

Teemu Manninen is building a detached house in Lahti designed to withstand the effects of the climate crisis, Yle reports. The home will be built with particular attention to increasing moisture loads, as summers become hotter and winters wetter.

The 150-square-metre, three-storey house is being built for Manninen’s family of four in Anttilanmäki, a culturally and historically valuable residential area in Lahti.

Manninen has considered both the requirements of the neighbourhood and the durability of the building’s structures if the climate crisis significantly changes local weather conditions. He works as a project manager at the earthworks company YIT Infra.

“The guiding principle in designing the structures has been that precipitation is more likely to increase than decrease,” Manninen says.

The house will have conventional eaves to protect its exterior walls and foundations from rain. It will also have measures to manage stormwater. Water will primarily be absorbed on the plot, in line with the City of Lahti’s approach, through pits beneath the yard filled with coarse gravel. The water will collect in stone-filled drainage pits and gradually seep into the soil.

The waterproofing on the foundations will be designed to withstand pressurised groundwater, even though there is currently no such risk. A drainage mat between the waterproofing and the gravel will collect and remove water while extending the life of the waterproofing.

Manninen does not plan to plant vegetation directly next to the building. Wet plants could prevent the structures from drying, while roots could reduce the empty space between the gravel. A row of old foundation stones will also help prevent stormwater from the street from flowing onto the plot.

The concrete basement will be topped by two timber-framed floors. Their ventilation will receive particular attention, including sufficient ventilation gaps in the walls and beneath the roof. The building will use gravity ventilation based on natural differences in air pressure and temperature.

The colour of the wood cladding has not yet been decided, but the house will not have black walls that heat up the interior. The local planning rules would not allow them.

Janita Rintala, director of sustainable development at the design consultancy A-Insinöörit, says she would also pay particular attention to increasing moisture loads if she were building a small house now. Her areas of expertise include managing climate risks, reducing emissions and the circular economy.

The building site affects moisture risks, Rintala says. She would prefer a sloping plot where rainwater would not accumulate. She also notes that high indoor temperatures during summer are a relatively new phenomenon for Finns and questions whether it makes sense to build a black detached house with very little roof overhang.

The construction replaces a 130-year-old house whose log frame was found to be in poor condition. The historic wooden-house neighbourhood sets its own requirements for new buildings.