How do you choose insulation for a house made of ceramic blocks before finishing the façade?

Inspect the lintels, ring beams and the junction with the floor slab. Establish where the reinforced concrete elements occur. They must be taken into account in the insulation solution. Insulating the flat field of the wall does not guarantee correct performance at the balcony corner or the reveal.

Before gluing, assess the evenness and condition of the surface. Remove the causes of damp. Loose fragments and dirt can weaken the fixing. Large unevennesses are not levelled with an arbitrarily thick layer of adhesive unless the system allows such work.

Calculate the resistance of the existing layers, then select the insulation for the adopted target. For example, assume that the wall together with the renders and surface resistances gives a total of R = 1.10 m²·K/W. This is an agreed value for the calculation, not a parameter of every ceramic block.

If the target is U = 0.20 W/(m²·K), the total resistance should be, in simplified terms, 5.00. About 3.90 m²·K/W is therefore missing. At a lambda of 0.026 W/(m·K) this corresponds to about 101 mm of insulation. The result requires selecting an available thickness and checking corrections and details. It should not be rounded down merely to fit the price.

The 120 mm variant may have a different declared lambda than a thinner board from the same family. The calculation must then be repeated with the parameter specific to the ordered product. Assuming one lambda for every PIR leads to errors.

For insulation systems with render, boards with a surface intended for such use are used. An example is a suitable glass fleece. The smooth aluminium facing of another board does not automatically become a substrate for adhesive and mesh. The whole set matters: insulation, mortars, fixings, reinforcing layer and finish.

For a hollow clay block wall, enter the λ-value for the insulation thickness you intend to order. In the render-grade board range discussed here, boards at least 120 mm thick have a λ-value of 0.025 W/(m·K). Use 0.026 W/(m·K) for thicknesses from 80 mm up to but excluding 120 mm, and 0.027 W/(m·K) for thinner boards in this range. If you change product ranges, check the new board’s data sheet.

During installation, observe the indicated side of the board. Do not swap adhesives or meshes arbitrarily. The number and arrangement of fixings must also be selected to suit the substrate and loads.

Determine the projection of window sills, the width of flashings and the position of downpipes. Allow for the finishing layers. A narrow eaves overhang may require a change of detail once the wall has been thickened. Likewise, brackets for balustrades, canopies or air-conditioning units need a planned transfer of loads into the masonry.

In the example extension in Przeworsk, the new wall can be insulated together with the old one if both substrates are assessed. The junction between the parts of the building nevertheless requires a separate solution. Different structural movement does not disappear under the mesh. Gaps and movement joints must not be covered without checking the design.

Plan scaffolding access and the sequence of work on the roof. The finished facade layer should not later be damaged during replacement of flashings. Every service penetration must have a defined method of sealing.

Prepare the material schedule after measuring the walls. Calculate the areas of reveals and the cuts at openings. Check the actual coverage of grooved boards and the pack sizes. The same facade area can give different consumption with a different cutting layout. Do not add an allowance at random, however, without reviewing the layout.

Before covering the insulation, check the joints, the corners of openings and the continuity at the plinth. Acceptance should take place in stages. Once the render has been applied, every fixing can no longer be easily checked. Keep the markings of the delivered batches and photographs of key details. They will help establish what was actually installed.

Also order solutions for fixing later equipment. A canopy, lamp or downpipe requires different preparation from a light decoration. Recording them before insulation reduces the number of later penetrations.