Low-carbon construction is composed of multiple components

The built environment is the source of up to a third of emissions that are harmful to the environment, so it is no wonder that the carbon footprint is talked about so much. However, one low-carbon part of a house does not make the rest of it environmentally friendly. Low-carbon construction is the combined effect of carefully considered floor plan, material choices and a method of heating that causes the least damage to the environment.

A low-carbon building lasts long and serves multiple functions

“An environmentally friendly building is low on carbon, durable and can be used for a variety of purposes. The environmental friendliness of a building is like a jigsaw puzzle: one missing piece affects the whole picture. In Finland, the Ministry of the Environment defines a low-carbon building as one that has as small a carbon footprint throughout its life cycle as possible. Low carbon emissions are achieved through energy-efficient planning and the use of construction materials that have a small carbon footprint and are durable and easy to recycle. Sensible use of space is important: the less space you need and the more versatile it is, the fewer materials and less energy you need,” says Matti Kuittinen, Senior Advisor at the Ministry of the Environment of Finland.

A building’s carbon footprint consists of the construction stage, use and the demolition stage, all of which affect the environmental friendliness of the building. Construction that aims at a long life of the building plays a key role in the aim for a low-carbon solution.

“By flexibility, we not only refer to versatility of use but also a long life cycle and the simple fact of not even building single-use buildings. The objective should be that instead of demolishing houses, they could be reused as far as possible,” says Eino Hekali, Product Director at Honkarakenne.

Long life is also another aspect of environmental friendliness: building in a way that the buildings last from generation to generation.

The climate-friendliness involves many things

Carbon footprint begins with design

Design is the key stage in low-carbon construction. “Since changes are difficult to make in the construction stage, the decisions must be made in the design stage. A building’s carbon footprint is affected by its architecture and size as well as the choices made in, for example, structures, technological coefficients and energy sources,” says Tuomo Koskimaa, HVAC specialist of Hoivarakentajat, long-time partner of Honka.

Environmental goals guide building design for companies and cities. Partners are increasingly chosen on the basis of their sustainability and the concrete action they take to help the environment.

The most important thing is the desire to build in a low-carbon manner, the solutions are there if you want them.

Eino Hekali, Product Director at Honkarakenne.

Wood construction – best alternative for the environment

A locally harvested tree is naturally an energy-efficient low-carbon choice, because it sequesters carbon from the atmosphere. A log building functions as a carbon sink and prevents, for the duration of its entire life cycle, carbon dioxide from entering the natural cycle.

For example, the wood-based materials of a 2,500 m² log school in Toppilansaari, Oulu, have sequestered 300,000 kilogrammes of carbon dioxide. When the school eventually reaches the end of its useful life, its solid wood materials can still be recycled to a high degree.

 The wood-based materials of a 2,500 m² log school in Toppilansaari, Oulu, have sequestered 300,000 kilogrammes of carbon dioxide

Hear what Oulu Christian School principal Mikko Saukkonen, former principal Petri Ojala and students at the primary and lower secondary school have to say about the new building.

Logs have a natural ability to retain an even level of humidity in a building, keeping it very well at the optimal level of 30–55%. A study by VTT Technical Research Centre of Finland shows that fluctuations in indoor relative humidity are significantly lower in log houses. Indeed, many parties in Finland have sought to solve problems with poor indoor air and meet climate goals by increasing wood construction.

Choice of energy is important for the climate

In environmentally friendly construction, it is important to choose a heating method that has as low an impact on the environment as possible. The choice of source of energy for a building should also take account of the heating system’s life cycle, including the manufacturing emissions, length of usable life and recyclability. This means that what may appear to be an environmentally friendly system is not automatically one with the lowest carbon emissions. “For example, solar panels are good when they produce energy, but the emissions for making them are high,” says Koskimaa.

The crucial thing in the choice of forms of energy is the big picture during the entire life cycle. The life cycle of a heating unit affects the big picture of environmental friendliness the same way as that of a building. An environmentally friendly heating system takes account of the equipment manufacture, implementation and recycling. According to Koskimaa, geothermal heating is a good choice that considerably reduces a building’s carbon footprint during its life cycle.

A log building is structurally airtight

An environmentally friendly building is structurally airtight with minimal heat loss. “Years of product development has resulted in very airtight log houses,” says Jukka Rintamäki, Product Development Manager at Honkarakenne.

If construction is done properly, using the best sealing materials, the best airtightness category (A) is easily achieved.

Jukka Rintamäki, Product Development Manager at Honkarakenne

In an airtight building, air changes in a controlled way through mechanical ventilation. “Controlled ventilation means that always the right amount of indoor air is changed mechanically. This also saves energy and increases ecology, because the ventilation unit recove

Ecology continues throughout a building’s life cycle

Time is the most important piece in the jigsaw of low-carbon construction. Responsible builders look into the future. It is important to build in a way that ensures, for example, that buildings can withstand not only the current climatic conditions but also the challenges brought about by climate change. The technical and physical properties of structures must be selected so that the structures withstand the higher temperatures of future and diagonal rainfall caused by high winds.

According to Matti Kuittinen, there is a clear new trend in the debate about low-carbon construction – recycling. “The debate on reusing construction elements has been active and will probably remain so,” says Kuittinen.

The good thing about logs is that they can be easily recycled. When a log building is no longer needed in its original location, the logs can be taken down and used for a new building. Logs can also be utilised in energy production or processed further into biofuel, for example.