Internal wall insulation (IWI)

• is generally cheaper to install than external wall insulation
• will slightly reduce the floor area of any rooms in which it is applied (the thickness of the insulation is around 100mm)
• is disruptive, but can be done room by room
• requires skirting boards, door frames and external fittings to be removed and reattached
• can make it hard to fix heavy items to inside walls – although special fixings are available
• needs any problems with penetrating or rising damp to be fixed first.