How retrofitting buildings improves energy efficiency across a city

Before commissioning façade insulation, find out what is driving the heating bill.

Record the structure, ventilation and occupancy of each building. Even identical blocks can differ after window replacement or alterations to services. Compare survey findings with the energy audit to identify the buildings that need attention first and the options worth pricing.

Design heating for the condition the building will reach after the works. If a breakdown forces early replacement of the heat source, allow for the lower load once insulation is installed. A joint schedule for the envelope, heating and ventilation helps match equipment to its eventual duty.

After windows are sealed, flats and classrooms still need supply and exhaust air paths. On the roof, locate drains and maintenance access early. Agree the loads and fixings for planned PV modules with the designer before laying the waterproofing.

Measure the clearance to thresholds, parapets and window sills. A PIR board with suitable thermal conductivity may provide the required thermal resistance in a thinner layer. A terrace section still needs room for drainage, waterproofing upstands and the other layers.

Specify the roof and walls separately. On the roof, check loads, compatibility between the facing and waterproofing, and the fixing method. For a rendered wall, select the complete façade system. Foil facing alone does not establish that render will adhere. PIR, EPS, XPS and mineral wool can each serve different purposes in one refurbishment programme.

Use a common schedule of work to compare bids for several buildings. Alongside envelope performance and product documentation, list scaffolding, substrate repairs, flashings and refitting equipment. Define how the work will be accepted. A lower price may simply cover fewer items.

Check a junction detail on site before repeating it in the next block. Inspect layers while they are still visible. In occupied buildings, agree access, working hours and heating outages. Give residents the schedule so they can prepare for each stage.

Match the controls to occupancy: a school and a block of flats need different heating schedules. Check system balancing as well. Controls can make an effective system work better, but an app reading cannot replace inspecting a leaking roof.

Compare generation with the hours when the building needs energy. A summer solar surplus falls outside the main heating season. Annual kilowatt-hours alone cannot establish self-sufficiency. Assess any storage proposal against the timing of both demand and generation.

Keep pre-retrofit records of energy use, temperatures and occupancy. When comparing later results, account for weather, occupancy and tariff changes. Assess comfort, consumption and emissions separately, stating the assumed energy source. This evaluates the programme without attributing its entire effect to one insulation board.

At handover, give the building manager an inspection schedule for drains, roofing and seals. Consider repairability, service life, manufacturing impacts and options after removal when selecting materials. Actual energy performance needs to be checked in each building while it is in use.