One family found a way how to create renewable energy for the household by building an energy-efficient house in Jomala, Åland, in 2016. The house was built with the aim of creating a healthy and energy-efficient house that fits a family with children and which is also affordable financially. It is a well-insulated treehouse that produces partly its own electricity and has energy-saving solutions like reusing the heated water from the shower.

The walls of the house are thick and constructed with double rules without cold bridges. The insulation is cellulose. The light inlet contributes to the heating of the house, which takes place through a fan-controlled supply and exhaust air system where the heated indoor air passes a heat recovery unit on the way out. The energy is used to heat the cooler incoming air.

When it gets colder than -5 degrees, the family needs to bring out two small extra batteries. They are considering installing an air-air heat pump for the cooler part of the year. The heating accounts for about half of the energy consumption. The annual consumption for the 142 square meter house is about 10,000-kilowatt-hours, which is about half of the average in Finland.

The 16 solar panels on the house annually generate just over 4,250-kilowatt-hours. Most of it goes out into the electricity grid, which, due to the tariff systems, is an unprofitable business because the family gets little paid for the electricity house produces.

A “Heatsnagger” heat recovery system in the house reduces the energy consumption for water heating. It utilizes heat from the wastewater from the shower on the upper floor and preheats the water entering the water heater.

Key words: private household, energy-efficiency, heating, solar energy, wastewater, Jomala, Åland