In a 1990s house, it is not always worth stripping the entire façade straight away. First you need to establish how the walls were built and where heat is escaping. Internal insulation can be feasible, but it requires careful selection of layers. The most problems usually arise at junctions and services, which are easily overlooked in an initial quote. The year of construction does not tell you what the wall is made of. In similar houses you can find various hollow blocks, cavity walls and later alterations. Locate the documentation, compare it with the actual condition of the building and carry out the necessary inspections. Check extensions and sections rebuilt when the windows were replaced separately.

Close to the plot boundary it is sometimes difficult to add insulation from the outside. Internal insulation can then be one of the options under consideration. It does, however, require checking the wall and the entire layer build-up. Saving space should result from the properties of the material and good detailing, not from omitting the necessary build-up. Check the geometry of the building, the condition of the façade and the possible scope of works. Proximity to the boundary alone does not determine the permissible solution. Arrangements concerning the property and the required documentation should precede purchase. It should not be assumed that a change solely from the inside always exempts you from other approvals.

Keeping the façade does not rule out improving comfort in a tenement building. Internal insulation, however, requires a thorough assessment of the wall and its junctions. Old masonry can conceal various materials, moisture and later repairs. The scope of work should therefore be established before buying boards and before refurbishing the whole flat. Check the wall thickness, the condition of the plaster and the type of material. Documentation may not reflect all changes. Inspections and properly executed exploratory openings are useful. Also establish whether the wall was previously insulated or covered with a layer of high diffusion resistance. Such information affects the possibility of drying out.