External Wall Insulation

From the standpoint of building physics, the most effective solution for insulating external walls is placing the insulation material outside the structural envelope. This approach is based on the property of warm air to hold more moisture in vapor form, and cooling of air masses leads to condensation.

The purpose of external insulation is to shift the so-called dew point from within the wall structure to the external insulation layer. Thus, moisture formed there will not accumulate in the wall, but will be released into the surrounding environment.

To ensure moisture removal from the insulation layer, various solutions exist. One of the most popular is the ventilated facade. This article will focus on this method of insulating external walls.

Construction of a Ventilated Facade

The basic principle of a ventilated facade is as follows. Steel or aluminum brackets are attached to the load-bearing base (which may be a wall made of brick, lightweight concrete, or monolithic material). A layer of insulation is installed between the brackets, with thickness determined by thermal calculations.

Horizontal, vertical, or combined guide rails are mounted on the brackets. This system serves as the base for cladding. Cladding materials may include ceramic granite, natural stone, composite panels, or metal cassettes.

The key element of such a facade is the ventilated air gap – the space between the cladding and the insulation layer. Typically, its width ranges from 3 to 6 cm. A wider or narrower gap is not recommended, as it may excessively increase or reduce airflow velocity.

Excessive airflow velocity in the ventilated gap may cause fiber emission (blowing out) from the insulation layer, while insufficient velocity will not ensure proper removal of condensate or drying of insulation. The recommended gap widths have been experimentally determined through repeated testing and confirmed by verification calculations.

Features of External Wall Insulation in Ventilated Facades

Insulating external walls in ventilated facades has several distinctive features. First, all brackets are divided into primary (load-bearing) and auxiliary. Primary brackets are typically located below window openings, while auxiliary ones are placed above. This division enhances the fire resistance of the entire facade, as the highest fire load occurs precisely in the area above window openings.

The second feature is the placement of guide rails – their spacing should typically be a multiple of 60 cm. In most cases, the horizontal spacing remains at 60 cm, while vertical spacing may reach up to 180 cm. The spacing of guide rails depends on the format of the cladding material and indirectly affects the size of the insulation used.

Mineral wool for ventilated facades can range in density from 19 to 100 kg/m³. The main requirement for the insulator is resistance to long-term air load and inertness to water exposure.