Maisonettes and Energy

A maisonette is a flat spread over two storeys, usually with its own internal staircase and sometimes its own front door, and that hybrid form gives it a hybrid energy pattern: part house, part flat. Like a house it has two levels to heat, a staircase that moves warm air between them, and often a roof or a ground floor of its own. Like a flat it shares walls, sometimes a roof or floor, with neighbours, and its external and communal works may need freeholder or manager consent. This guide explains the maisonette pattern, the position effects that shape it, and the measures that suit it. It is general guidance, and maisonettes vary greatly by position and lease, so a specific home needs its own assessment.

In practice a maisonette's energy story is written across its two levels and its neighbours. An upper maisonette under a roof carries roof losses and summer overheating risk, while a lower maisonette over an unheated space or a garage carries floor losses. The internal staircase creates a stack effect, with warm air rising to the upper level and cooler air settling below, so heating balance between levels matters more than in a single-level flat. Shared walls reduce exposed area, but junctions with neighbouring flats, stairwells and common parts can carry bypasses. Heating may be individual or communal, and controls should serve two levels rather than a single thermostat position. Windows on two levels, sometimes including a stairwell window, add glazing and draught questions that a single-level flat does not face.

Check position first: upper, lower or mid-building, with its exposed roof, floor and side surfaces listed. Check heating type, controls and distribution between levels, walking both levels on a cold day and noting which level lags or overheats. Inspect the staircase area for draughts and heat movement, check loft or roof access where the maisonette includes it, and check floor construction where it sits over unheated space. Read the lease or building rules for windows, external work and heating changes, and ask the manager about building-level plans. Record both levels separately, since a maisonette's upper and lower levels often behave like two different homes joined by a staircase.

Maisonettes are a recognised form in the UK stock, assessed within the EPC system, with leasehold and building rules shaping what an owner or tenant may do, and distinct arrangements across the nations. In EU member states, two-level apartments appear under different names and tenure models, with national certificate methods and homeowners' association rules under the EPBD framework. The physics travels: two levels, a staircase stack effect, shared walls, and position-dependent roof or floor losses. The lease, consent and building-plan steps do not travel, and a reader should check them for the country where the home stands before pricing any external or communal measure.

The classic maisonette mistake is heating both levels from a single thermostat on one level, so the other level is chronically too warm or too cold. Another is treating the maisonette as a house for external measures, and discovering that freeholder consent or a block programme governs the work. A third is ignoring the staircase stack effect, and insulating or draught-proofing in a way that worsens temperature imbalance between levels. A fourth is overlooking roof or floor position effects, and improving walls while the roof or floor remains the dominant loss. A fifth is planning measures level by level without considering the staircase junction, where air leakage and cold bridging concentrate. A maisonette rewards two-level thinking, and punishes single-level assumptions.

Keep the maisonette's file as a two-level record: certificate, position notes, level-by-level heating observations, lease or building-rule notes, and measure evidence. When a measure is proposed, ask how it serves both levels, how the staircase will be treated, and whether consent or a block plan affects it. A home-specific assessment that records both levels is the usual next step, followed by a plan that balances heating, treats the dominant exposed surface, and respects the building's shared elements. A maisonette understood as two levels in one building, rather than as a flat or a house alone, is a maisonette whose improvements tend to reach every room.