SAP calculations in Hackney

Conservation areas and listed buildings across Hackney

With 37 conservation areas and 555 listed entries, a large number of Hackney streets carry some form of heritage control. 30 entries are Grade II*, and 40 appear on the Heritage at Risk Register.

On protected terraces the council is usually most concerned with the front elevation. That is workable for energy, since the rear and the roof are where new elements go and where the U-value limits apply. We keep the original front wall out of the calculation, because it is existing fabric, and model only what is new.

Flats, terraces and an unusual housing mix

Only 18.8 per cent of Hackney households live in a house, and 24.6 per cent own their home, so most Hackney homes are flats, and many projects involve a converted terrace or a single house on a street of flats.

A terraced house averaged £960,633 in the latest Land Registry data and a detached one £1,330,617. At terraced values, even a modest side-return extension justifies careful energy design, and a heat pump or underfloor heating can be specified from the first drawing.

Meeting the limits on a Hackney terrace

For new elements the document sets: 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 slim side-return roof needs enough insulation depth to meet the roof figure, and the depth shows up in the section, so we draw it early.

Glazing is the other limit: 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 side return is exactly the kind of design that breaks it, and the guidance anticipates that: Alternative routes: area-weighted U-value (para 10.9) or a SAP calculation against a notional extension (para 10.10).

Our side return extension drawings include that glazing check, so the first plan is already one that can pass.

Conversions into flats and new dwellings

Where a Hackney house is split into flats, each new dwelling is assessed. 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 deposit date decides the edition, and the start is set out as: AD L 2026 takes effect 24 Mar 2027 (24 Sep 2027 for higher-risk building work).

Summer comfort matters in the top-floor flats of dense terraces. Approved Document O (overheating) applies to new residential buildings. The assessor needs window areas, orientation and any shading, all of which we take from the drawings.

Keeping a Hackney terrace project on programme

Time is often tight on a Hackney project, for example when the owner is living elsewhere during the work. The calculation should never be the item that holds up the building notice, so we order the work to avoid that.

We start the energy model once the layout is fixed and before the construction details are finished. The assessor works from the plans while the technical drawings are completed, and the two are reconciled at the end. If a detail changes, the model is updated rather than restarted.

For a leasehold conversion, check the lease before you start. Some leases restrict external changes and roof works, and a change to the roof insulation can need the freeholder agreement. We flag that at the first call and leave the legal side to your solicitor.

One more Hackney habit is worth keeping. Hold the final specification in a single schedule and update it whenever the builder proposes a substitute, so the calculation never drifts away from what is in the walls.

How this fits your Hackney package

The calculation sits alongside building regulations drawings in Hackney and the beam design in structural calculations in Hackney. The wider picture is at architectural drawings in Hackney.

Price is a fixed quote after a free constraints check, VAT included. Send the address and tell us whether it is a house or a flat conversion.