A centimetre of EPS does not provide the same thermal resistance as a centimetre of any PIR board. The comparison must be based on the lambda value of the specific material. The whole wall build-up and its finish are then checked. A thinner layer may make the reveal detail easier to resolve, but the difference in thickness alone does not determine the choice. First read the lambda value of both products under consideration. Do not assume a single figure for all EPS or for the entire PIR group. Properties depend on the variant. A board with a metallised facing may have a different application and parameter from a board intended for plaster.

On an aerated concrete wall, the entire insulation system must be selected. The properties of the masonry, the type of PIR facing and compatibility with the render layer are important. Not every insulation board is suitable for such an application. The required thermal performance is set by the design, and the thickness results from calculations and the available details. Record the variant, thickness and declared properties of the blocks. The density and method of constructing the wall affect its parameters. A single thermal resistance should not be attributed to the entire group. Joints, renders and areas with other materials are also needed to assess the wall.

A wall made of ceramic blocks does not have a single common thermal parameter. What matters is the type of block, the wall thickness and how the joints are made. Insulation is selected only on this basis. In practice, it must also fit at the windows, the eaves and the plinth. Choosing the number of centimetres alone does not complete the design. In a new house, refer to the material schedule and check what was actually built in. In an older building, an inspection opening at a window or door opening can help. Do not determine thermal properties solely from the colour of the ceramic. Blocks of similar appearance may have a different arrangement of voids and a different purpose.

A quick calculator helps compare insulation thicknesses. However, it will not identify damp masonry or a poorly detailed reveal. For the result to be useful, the actual wall and its operating conditions must be described. Heat loss, surface temperature and the risk of moisture within the construction are checked separately. Record the layer build-up from inside to outside. For each layer, give the thickness and thermal properties. In an existing building, do not automatically assume that the wall matches a typical solution from the year of construction. An air cavity, a different type of block or later cladding can change the result.

Inexpensive insulation starts with determining how the building will be used. A cold storage room has different needs from a workshop heated on Saturdays, and both differ from a small house used throughout the winter. Savings are worth seeking in good cutting plans and simple details. Insulation that is too thin or ventilation that is omitted can quickly undo the effect. Note the planned temperature and heating hours. In a garage without a heat source, insulation alone will not maintain a constant residential temperature. It can slow the rate of cooling and heating, but the result also depends on the door, roof, floor and air exchange. Do not buy thickness based on the name “garage” alone.