Wall Insulation

There are many ways to insulate walls, which we can conditionally divide into two groups: insulation during new construction and retrofit insulation during building operation.

Wall Insulation Methods in New Construction

From a building physics standpoint, the most appropriate solution is to place the insulation material on the outside of the load-bearing wall. In this case, the dew point is shifted into the insulation layer, keeping the load-bearing wall permanently dry. Recall that the 'dew point' is the location within the wall structure where warm indoor air, penetrating into the wall, cools to a degree that it can no longer hold moisture in vapor form and begins to condense into water droplets. The dew point is an indirect cause of wall freezing, mold, and mildew formation.

Method #1. Installation of a ventilated facade.

Support brackets (G- or U-shaped cross-section) are mounted on the load-bearing wall, to which vertical and horizontal guides (substructure) are attached. A layer of insulation 50–200 mm thick, depending on regional climate, building purpose, and internal temperature conditions, is placed under the guides. The cladding – such as ceramic stone, fiber-cement panels, siding, etc. – is then installed on the substructure. The principle of operation for this system is that the dew point is located within the mineral wool (insulation) layer, and the condensate formed there is removed by air movement under the cladding at speeds of 2–4 m/s.

Method #2. Installation of a rendered facade.

First, the insulation material (mineral wool or polystyrene foam) is bonded to the load-bearing wall using cement-based adhesive. After 24 hours, the bonded material is additionally secured with flat-tipped anchors and primed with a cement adhesive mix. Then, a primer layer is applied, followed by adhesive, a reinforcing layer with 3–4 mm mesh glass fiber fabric, and finally, a decorative finish – usually a colored plaster applied in mass.

Method #3. Insulation of a three-layer wall.

This method is most common in modern homes built with brick. The inner wythe (wall) often uses gas-silicate blocks or aerated concrete, while the outer wythe is made of facing brick. The space between these two materials is filled with mineral wool or polystyrene foam. This construction is widespread, though controversial from the standpoint of the fundamental law of building physics, which states that each subsequent layer in a multi-layer structure must be more vapor-permeable than the previous one. With mineral wool, this law is satisfied; with polystyrene foam (PSB), it is violated, potentially leading to wall freezing and excessive heat loss due to moisture accumulation.

Wall Insulation Methods in Renovation (Reconstruction)

Here, the construction 'toolbox' is significantly more limited than in new builds. Numerous reasons exist – not always possible to wrap the facade of an existing building into a scaffold framework, not always possible to anchor into the old wall (especially relevant for all types of suspended facade systems), and so on. What remains? Several options.

Method #1. Any external suspended system.

Try to use rendered or ventilated suspended facade systems if conditions allow. No better solution exists for price-to-energy-efficiency ratio. For old or weak walls, chemical anchors may be used to secure insulation and cladding. If, due to the above reasons, a suspended facade cannot be installed, proceed to the next option.

Method #2. Blown-in insulation.

Applicable to layered walls. An opening of approximately 25 cm diameter is cut into the inner or outer wythe, through which a hose delivers finely shredded glass wool under pressure, uniformly filling the entire wall cavity. This technology originated in Western Europe and Canada, where it gained deserved popularity among building insulation clients for its excellent thermal resistance performance.

Method #3. Internal wall insulation.

Should only be used when all other options are unfeasible. It must be emphasized that internally insulated walls drastically reduce service life, as they freeze completely and undergo repeated 'freezing-thawing' cycles, in effect artificially aging the wall. In this case, mineral wool must be carefully vapor-barriered with a specialized membrane on the indoor side, otherwise moisture will accumulate within.

Choosing Insulation Materials

For non-load-bearing structures (e.g., framed buildings), lightweight, flexible, and resilient boards made from glass or basalt fiber are recommended. For structures subject to wind or other loads (all suspended facades), materials must be sufficiently rigid, prevent fiber emission (blowing out), and have good tensile strength perpendicular to the facing surfaces.