Insulation can be added to existing buildings with varying effectiveness and cost depending on the construction type and where the insulation is being placed.
Ceilings and suspended floors with easy access are relatively simple to insulate post-construction. Insulation board can be laid beneath floor finishes if there is no under-floor access.
Walls and skillion roofs are the hardest to insulate after construction, as the internal or external lining must be removed. A good time to insulate walls is during recladding or replastering. Specialised products are available to insulate existing walls: check with your local building information centre. External insulation or (if local building regulations permit) cavity fill are often appropriate solutions for cavity brick walls.
Adding insulation to existing buildings can greatly increase comfort and reduce energy costs and greenhouse gas emissions. An ideal time for doing this is during renovations. Insulation can be retrofitted to various construction types.