How to plan internal insulation for a 1990s house without replacing the façade?

Pay attention to moisture at the plinth, roof and balconies. Insulation will not replace repairing a leak. The condition of the old plaster determines whether new layers can be bonded. It is also worth assessing how the ventilation and heating of the rooms perform. A cold room can have several causes of heat loss.

If you plan to modernise in stages, make a shared map of problems for the whole house. Repairing one room without resolving the leak above may bring only a short-lived improvement. Establishing the dependencies allows funds to be spent in the right order.

It is considered when external works are difficult or the façade is to remain. However, the effect of the new layers on the temperature and moisture of the masonry must be checked. After reducing the heat supply from the room side, its conditions change. Therefore a thermal and moisture assessment specific to the system under study is needed.

PIR with an aluminium facing has different diffusion properties from insulation open to vapour flow. It is not chosen solely by its small thickness. The solution must include tight joints and the ability of the assembly to dry out under the assumed conditions. A damp wall first requires identification of the cause.

Not every element of the house can be insulated in the same way. Separate details are needed at the ceiling, transverse walls and balcony. If constraints prevent correct execution, it is worth changing the scope or system before the boards are purchased.

Start by calculating the existing assembly and the assumed renovation target. For example, 80 mm of PIR with a lambda of 0.022 W/(m·K) gives R of approximately 3.64 m²·K/W. This is the contribution of the insulation alone to the thermal resistance. The U-value is also determined by the masonry, plasters and joints.

To the installation dimension add the fixing, the finish and any installation space. A composite board with a gypsum facing can reduce some of the work, but does not remove the need to resolve the details. Check doors, recesses and radiators. A few additional centimetres can force a change of fittings.

For an example wall 4.80 m long, build-up with a total thickness of 100 mm will take up approximately 0.48 m² of floor space. It is worth comparing this space cost with the thermal effect. Counting only centimetres of foam will understate the actual change to the room.

First plan the services and equipment fixing points. Removing radiators and relocating sockets should precede closing the insulation. Allow access to key connections. Some work can be done room by room, but stage completions must be designed.

An example renovation in Żnin can begin with one room with a well-assessed wall. The trial will show the condition of the substrate and actual conflicts. However, it is not a substitute for calculations. If the revealed layers differ from the assumptions, the choice of solution must be revisited.

Before every break, protect the material and exposed edges. Do not leave an open air-flow path behind completed build-up. The junction between stages must remain accessible so that it can be correctly closed.

Accept the insulation and seals before final finishing. Check the perimeter at the floor, ceiling and reveals. Verify that service penetrations were executed as planned. Photo documentation of concealed areas is more useful than photos of the painted room alone.

After renovation, restore heating and proper ventilation. Observe the corners in the first season. Do not immediately block the problematic wall with sealed fitted furniture without taking usage conditions into account. If moisture appears, check the cause before further covering.

Keep the data of the boards used and a description of the layers installed. For subsequent rooms it is then easier to maintain consistency. A change to a product of the same thickness but a different facing should be reassessed.