Alustaeristys

Alustaeristys, or base insulation, refers to the insulation layer placed on the base or underneath a building’s floor or foundation. It is a form of foundation insulation aimed at reducing heat loss to the ground, minimizing frost-related movement, and managing moisture. In cold climates, alustaeristys plays a key role in energy efficiency and structural durability by limiting heat escape and protecting under-foundation components.

The technique is used in various parts of a building envelope. It can be installed around exterior foundation walls, under concrete slabs-on-grade, or beneath other floor systems. Often it is combined with waterproofing, vapor barriers, and drainage considerations to prevent moisture problems. The installation aims for continuous insulation with careful detailing to avoid thermal bridges at corners, edges, and around penetrations.

Common materials for alustaeristys include rigid foam boards such as expanded or extruded polystyrene (EPS or XPS) and sometimes polyisocyanurate (PIR) or mineral wool, depending on climate, moisture conditions, and structural requirements. Finishing layers or protective boards may be used to guard the insulation from mechanical damage. The choice of material and thickness depends on climate, building design, and energy targets, as well as local standards and regulations.

In practice, alustaeristys requires proper design to ensure compatibility with waterproofing, drainage, and moisture control systems, as well as accurate detailing to prevent condensation and moisture buildup. It is governed by national or regional building codes and energy performance requirements, which specify performance targets and installation guidelines for foundation and floor insulation.