SAP calculations in Tower Hamlets

Energy rules for a Tower Hamlets extension or roof

Before any calculation, we ask what the building already has: the age of the walls, whether the windows are single or double glazed, how the flat is heated and how it is ventilated. Those answers decide the starting point, and they often decide whether a modest improvement to one element is enough. Every drawing set is checked by a second person before you see it.

For new parts of an existing home, the limits are: New elements in existing dwellings, limiting U-values W/(m²·K): roof 0.15, wall 0.18, floor 0.18, windows 1.4 (or WER Band B), doors 1.4. A roof alteration or a rear infill can meet them with ordinary build-ups.

Glazing is capped: Windows, roof windows, rooflights and doors in an extension should not exceed 25% of the extension floor area plus the area of openings removed or covered. A glazed infill facing a tiny courtyard reaches the cap quickly.

Where a design cannot hit every limit, the alternatives are: Alternative routes: area-weighted U-value (para 10.9) or a SAP calculation against a notional extension (para 10.10). In a crowded terrace the comparison route usually gives the designer room to keep a wide window without a penalty elsewhere.

Heritage in Tower Hamlets and what it means for energy upgrades

The borough has 59 conservation areas, 64 Article 4 directions and 2 World Heritage Sites intersecting its boundary. Historic England lists 916 entries, with 21 at Grade I and 39 at Grade II*, and 39 entries sit on the Heritage at Risk Register.

That density of designation constrains every energy decision. Adding insulation to a listed Georgian house, replacing glazing in a conservation area or altering a roof near a protected view is not a free choice. We assume only what the conservation officer is likely to allow, and we show the calculation both ways when the answer is unclear.

Householder work is a small share of the council's caseload: 191 householder decisions against 427 minor ones in the latest year. The council granted 92.7 per cent of householder applications and 84.3 per cent of minor ones. See our planning drawings in Tower Hamlets for the application set.

New dwellings, conversions and the rule dates

A new dwelling is assessed differently: For new dwellings AD L 2026 names two methods: the Home Energy Model (HEM) and SAP; validity dates are in the Notice of Approval. The next edition starts as follows: AD L 2026 takes effect 24 Mar 2027 (24 Sep 2027 for higher-risk building work).

The transition rule: AD L/F 2021 continue where plans/notices are deposited before 24 Mar 2027 and work starts before 24 Mar 2028. When an upper-floor flat is carved out of a larger building, the deposit date is the first thing to fix. Overheating needs attention in tight, south-facing flats: Approved Document O (overheating) applies to new residential buildings.

At the end of the build, An energy performance certificate is required on construction of a new dwelling. Prices vary sharply: a flat averages £430,120 and a terraced house £690,210, with the average price having changed by -14.4 per cent in a year.

Cost, levies and linked drawings

You receive a fixed quote after a free constraints check, VAT included, before committing. The assessor works from our model, and the result supports your submission with building regulations drawings in Tower Hamlets.

New floor area attracts charges. The Mayoral band is band 2, at an indexed £72.73 per square metre, and the borough applies the Tower Hamlets CIL2 Charging Schedule 2020 with residential rates of £335.33/m² (Zone 1); £179.64/m² (Zone 2); £59.88/m² (Zone 3).

For the structure behind a new opening, see structural calculations in Tower Hamlets, and for another east London borough, compare SAP calculations in Waltham Forest.