Planning an energy retrofit, from identifying heat loss to final inspection

Use the thermal survey alongside a building inspection and the construction records.

Record what you want from the retrofit. A warmer house, lower heating costs or a usable loft may require different work. If a room will change use, check the loads, ventilation and finish requirements too. Insulation is just one part of a conversion.

The insulation is most easily interrupted where roofs, walls and floors meet. Detail the eaves, ring beam, plinth and reveals. Even a thick layer in the middle of a wall cannot compensate for every fault at its edges. Resolve the junctions before ordering, as a later repair can require dismantling finished work.

Work can be phased if each stage allows for the intended final construction. When repairing the roof, allow for future wall insulation. When replacing the windows, plan their connection to the new insulation. Otherwise, individual trades may complete their own areas correctly while weak points remain at the boundaries.

PIR’s low thermal conductivity is useful when roof or floor height is limited. EPS, XPS or mineral wool may better suit other requirements. Compare moisture exposure, loads, fire performance and acoustics. Choose the insulation for each part of the building according to its conditions of use.

Check the declared thermal conductivity and the performance data relevant to the application on the product data sheet. For a floor, check loads. For a façade, confirm compatibility with the finishing system. Aluminium-faced boards are suitable beneath render only where the system specifies them. Determine insulation thickness for the complete assembly, including its junctions and the way the building will be used.

Resolve roof leaks, rising damp and loose render before adding insulation. New insulation can hide the cause and make drying more difficult. If necessary, open up the construction and measure moisture levels so that defects can be repaired before the final finish goes on.

Assess heat and moisture behaviour particularly carefully with internal insulation or combinations of unlike materials. Membranes and joint seals must match the design. A gas-tight board facing alone cannot make a whole loft airtight. Detail and seal the junctions at walls, windows and every service penetration.

Reducing heat loss changes the heating output the building needs. Review system settings and controls. If replacing the heat source, size it for the building after the retrofit so the equipment matches its actual demand.

A more airtight building also needs effective ventilation. Occupants continue to generate moisture and need fresh air. Provide the air exchange required by the design. Closing air inlets to save energy can worsen indoor conditions even in a well-insulated building.

Inspect substrate preparation, board layout, fixings and continuity of seals. Keep documents identifying the exact materials delivered. Photographs of layers before covering help with later servicing. A person familiar with the system should also inspect the work at that stage.

At completion, compare the work with the design, rectify defects and hand over maintenance and operating instructions. Review energy performance after a full season, taking weather and indoor conditions into account. Design, installation and operation together determine how much benefit the new insulation delivers.