The Finnish pilot project - Student house Pohjankaleva

Location

Oulu, 600 km north from Helsinki

Number of apartments

33 flats

Number of buildings

One building

Type of building

Block of flats (eight floors and ground floor)

Year of construction

1970 (renovated in 1993)

Walls

concrete + siporex (U-value 0.55 W/m²K)

Ventilation

Mechanical exhaust from all rooms. Windows are equipped with fresh air slot. The average design exhaust air flow rate with maximum fan speed is 1.0 l/s,m².

Heat source

District heating (The CHP-power plant in Oulu mainly uses peat (79%) and wood (12%) and oil (9%).)

Heating demand

140 kWh/m² (domestic hot water 30 kWh/m², electricity 20 kWh/m²)

Other issues

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Results from occupants questionnaire study:
Main indoor quality problems were too high indoor temperatures during spring and summer. There are also a lot of draught complaints. 

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Existing U-values:

Walls 0.55 kWh/m²

Roof 0.35 kWh/m²

Windows 1.7 kWh/m²

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Air tightness: n₅₀ 6.0 1/h

Renovation

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The goal is to reach passive house standard level which in northern Finland is 30 kWh/m² per year for heating energy (domestic hot water 25 kWh/m²). 

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Each flat will have its own small kitchen and bathroom. The size of a single flat will be between 25 and 36.5 m². All flats will be equipped with a balcony which will also reduce incoming solar radiation to the flats.

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A new solution for external insulation developed in TES (Timber based Element System) project is utilized in this project.

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The targets for the renovation are:

• U-value for outer walls: 0.07 - 0.10 W/m²K

• U-value for roof: 0.06 - 0.08 W/m²K

• U-values for windows: 0.6 - 0.8 W/m²K

• Air tightness of the building envelope n₅₀ 0.6 1/h

• Efficient heat recovery from ventilation air (heat wheel) will be installed

• Kitchen exhaust air flows will be controllable