What is the benefit of thermal insulation?

Properly insulating a single-family house reduces draughtiness and saves energy, due to the heat not escaping through the shell of the building. Thermal insulation is the thermal underwear of the building; it keeps it warm during the winter and cool during the summer. The efficiency of thermal insulation is based on the still air in the insulation and outer layer of the building.

Energy efficiency requirements for new buildings were updated in 2010. For example, the maximum need of heating energy (does not include the heating of water) used to be 75 kWh/m2, however according to today’s requirements it should be 60 kWh/m2. In 2012 a shift to conducting total energy inspections was made; energy efficiency is aimed to be improved by 20%. The R-value eases the measurements during a total energy inspection. The R-value is the overall coefficient of heat transfer of the material or structure.

Where and how much thermal insulation is needed?

The regulations have changed over the years and the requirements have become stricter. The thermal insulation thickness of the exterior wall should be 200-300 millimetres, in passive houses the thickness should be 350-450 millimetres (using mineral wool insulation). The thickness of the thermal insulation is influenced by the material used. For example, the insulating capability of sawdust is not as high as that of modern cellulose wool, therefor sawdust should be used generously.

Thermal insulation is needed for the base floor (the foundation) or floor, frost casing, and walls and roof (cellulose, rock wool, and mineral wool). Cellulose wool insulation goes together best with other wood-based insulation and is also suitable for people with allergies.

How can thermal insulation be improved in older wooden houses?

The connection point of walls, windows, and structural elements should be sealed, especially if draughtiness occurs. In addition to this, supplementary thermal insulation can be provided for the walls (from the inside by adding wood fibre boards), the ceiling (by adding thermal insulation and thickening the insulating layer), and the floor by using a raised floor method (from the bottom up). The easiest, most cost-effective and heat efficient method is to insulate the ceiling and roof, due to heat escaping from above. It is difficult and expensive to change or repair the framework or heat insulation of the floor and walls.

Thermal insulation suitable for wooden houses is cellulose-flax wool. It is not worth it bringing plastic to a renovation or worksite of a wooden house!