Every centimetre counts when insulating from the inside, particularly in a hallway or under a sloping roof. PIR boards can reduce the insulation thickness needed, and boards bonded to plasterboard make finishing easier. The space you save depends on the dimensions of the room and the complete lining. There is no single percentage that applies to every interior. Check the thermal and moisture requirements first, then calculate the difference. For a homogeneous layer, thermal resistance is its thickness divided by its thermal conductivity. The lower the conductivity, the thinner the layer can be for the same resistance. This is the main advantage of many PIR boards where space is tight.

Insulating a loft from the inside can make it more comfortable without taking the roof covering off. PIR bonded to plasterboard provides insulation and a surface ready for finishing in one board. This is useful where headroom under a pitched roof is tight. First, though, check the roof itself. Air leakage, moisture, the condition of the timber and the way the boards are fixed matter just as much as insulation thickness. Before work starts, find out what lies between the room and the roof covering: identify the insulation, membrane and sheathing, and trace the ventilation paths. Check for leaks and damp timber. A new lining can hide the signs without fixing the cause.

PIR insulated plasterboard combines thermal insulation with a surface ready for interior finishing. It can simplify refurbishment where space is tight and installation time matters. Before fitting it, assess the wall's condition, specify suitable fixings and design airtight junctions. An external wall insulated from the inside needs particular attention. The PIR core provides insulation and the factory-bonded plasterboard faces the room. Facings and an adhesive layer may lie between the two. A damp or cold wall needs a diagnosis before it is lined. This product also differs from the sandwich panels with two steel faces used to enclose industrial buildings.

Before choosing insulation or finishes for a historic building, establish which features give it its character, what condition it is in and what protection applies. Internal insulation may be an option where the façade must be preserved. It requires a careful assessment of moisture and junction details. A PIR board alone will not remedy cold or damp masonry. In Poland, check whether the property is entered in the monument register, included in a heritage inventory or covered by another form of protection. These designations can have different implications. Its location in a protected area and local planning provisions may also matter. Protection can extend well beyond the street façade.

A roof over a heated pool has to withstand warm, humid air and the chemicals used to treat the water. Specify the facings, fixings and seals for those conditions. PIR insulation can reduce heat loss, but the roof also needs corrosion protection and the building needs ventilation. Assess the whole assembly, from the internal lining to the drainage, before deciding on a core thickness. A seasonal cover for an outdoor pool and a heated indoor pool are different design tasks. For an indoor pool, establish the air temperature, humidity and pattern of use. The exposed water surface, number of swimmers and periods when the pool is closed all affect the load on the building services and conditions at the roof.