Passive houses: why the roof is part of a whole-building strategy

The form and envelope are planned to reduce losses early and use available heat gains without sacrificing comfort. A material supplier’s claim does not establish the whole-house standard. If formal confirmation is required, identify the applicable criteria and project documentation.

A well-insulated wall does not rule out leaky junctions or thermal bridges, while large glazed areas can increase summer overheating. The design should account for climate, use, shading and ventilation. Assessment extends beyond winter heat loss.

Dormers, chimneys and changes in roof geometry add layer junctions, cuts and flashings. Simpler geometry often makes insulation and airtightness continuity easier. A more complex roof remains possible, but requires careful design of more details.

Metal roof tiles and trapezoidal sheets primarily provide external weather protection. They do not independently establish an energy standard. Their pitch, support and details must fit the structure and the moisture and thermal design of the complete roof assembly.

PIR with a suitable declared thermal conductivity can provide high thermal resistance at limited thickness. This may help at edges or in a layer above the structure. The benefit depends on accurate board fitting; gaps compromise the intended insulation continuity.

Mineral wool may suit particular acoustic or fire requirements, XPS different moisture and loading conditions, and EPS selected economical arrangements. Do not extend one product’s advantages to every building element. Assess the material in its intended application and complete assembly.

Uncontrolled airflow carries heat away and can transport moisture into cold roof areas. Plan a continuous layer at the heated-space boundary. Pay particular attention to wall and window junctions and service penetrations.

An airtight home still needs controlled air exchange, typically with heat recovery. Airtightness and ventilation fulfil different functions. Carry out a pressure test while any detected leakage can still be repaired without dismantling the finished interior.

Examine wall plates, window edges, chimney penetrations and fixings, not just the middle of the roof slope. Thermal bridges can result from junction geometry or materials. Adding insulation across the main area does not automatically repair every local detail.

Summer comfort depends on window orientation, shading and ventilation; metal colour alone does not describe indoor temperatures. Photovoltaics do not remove envelope leaks. Reduce the building’s demand first, then size the energy systems accordingly.

Coordinate energy calculations with architecture and building services. Ask where the heated envelope runs, which performance values are assumed and how workmanship will be checked. If certification is intended, establish its conditions and documentation at the start rather than after construction.

At inspection, compare declared material properties with the documentation and actual installation. Retain product data and photographs of the layers. Performance depends on coordinated design and workmanship, especially where insulation, airtightness and weather protection meet.

When comparing indicators, check the energy category and reference floor area. Heating demand is not the total electricity used by appliances. A calculated result does not guarantee a particular bill, because occupant behaviour and operating conditions also affect consumption.