Edwardian period restoration with ASHP + MVHR, BR2

Brief

1906 Edwardian semi BR2 Shortlands Conservation Area — 168m² over three storeys (semi-detached), south-east aspect, original double sash windows largely intact (11 of 16) with leaded fanlights; original cornices, ceiling roses, dado rails, picture rails throughout. Owners (medical consultant + barrister, two teenage children) brief: full heritage restoration of period features + low-carbon services retrofit — ASHP + MVHR — while preserving the Edwardian character. EPC E (48) → target B; replace failed 1990s uPVC windows with period-correct timber sash; restore original cornices including a fully collapsed hallway run; introduce Crittall-style internal partitions for broken-plan effect rather than open-plan. Budget £285,000. Bromley borough conservation area Article 4 applies; pre-application advice secured for window replacement spec.

Challenge

Five compounding constraints. (1) Conservation area heritage: Bromley CA Article 4 — sash windows must match original profile and detail; LBC not required (not listed) but heritage spec essential for planning. Pre-application: timber sash with reproduction leaded fanlights matching adjacent surviving originals; uPVC refused as material. (2) Heat pump siting: original elevations all visible from Shortlands Avenue (CA principal elevations); ASHP location required careful screening — solution behind east-side timber screen 8m from rear corner. (3) MVHR retrofit complicating heritage: routing 90mm semi-rigid ducting through 168m² 3-storey Edwardian without compromising original cornices required dropped ceiling in hallway and master en-suite only; bedroom and reception room cornices preserved via void routing under floorboards. (4) Cornice restoration scope: hallway ceiling cornice completely collapsed (water damage from earlier leak); 28m of replication required to match adjacent 64m original cornice — specialist plasterer (Pavilion Plaster, James Davenport) for run-in-situ matching. (5) Mixed window replacement: 11 surviving original sashes restorable (lead glazing, original glass); 5 uPVC replacements needed period-correct sash (Mumford & Wood Conservation Range) — careful matching of glazing pattern and sash horns.

Solution

Pre-application + design: 9 weeks. Bromley CA pre-application advice secured for ASHP siting (east elevation behind timber screen — approved), sash replacement spec (Mumford & Wood Conservation Range with single-glazed appearance but slim 16mm DG — approved as 'in-keeping'), Crittall-style internal partitions (no planning required — internal). Heritage consultant report on cornice profile matching. MCS heat-loss survey + MVHR design. Build 22 weeks. Weeks 1–4: Strip out. Internal demolitions exposing original fabric; cornices and ceiling roses photographed and protected with foam shields. Asbestos survey clear. Original ground floor parquet exposed under 1980s laminate — confirmed Hicks pitch pine, restorable. Weeks 5–9: First-fix services. Electrical rewire throughout; new gas supply cut off and capped (full electrification); plumbing first fix; MVHR first-fix in attic plant zone (Zehnder ComfoAir Q350) + duct routes (semi-rigid 90mm radial via dropped hallway ceiling and en-suite ceiling only — bedrooms and reception fed via floor void from above). Weeks 10–13: Heritage restoration phase. 11 sash windows restored: re-glazed where lead came damaged (3 windows fully re-leaded by Holy Well Glass £8,800); 5 sash replacements installed (Mumford & Wood Conservation Range, 16mm slim-profile DG, traditional putty look + horns/glazing bars matching adjacent originals £18,500). Cornices: 64m of original cornice cleaned, stripped of paint layers, repaired where cracked (Pavilion Plaster £14,500); 28m of replication required in hallway — profile measured from adjacent original, run-in-situ on lath-and-plaster substrate (£18,500). 5 ceiling roses repaired; 3 chimney breasts retained with original cast-iron register grates restored; pitch pine parquet sanded and finished with Junckers Strong satin lacquer. Weeks 14–18: Services completion + heating. ASHP installed (Mitsubishi Ecodan 8.5kW on east-side concrete pad behind 1.8m timber screen — CA officer approved); 250L pre-plumbed cylinder in attic plant zone; flow 35°C UFH (new kitchen extension) and 45°C radiators throughout (12 period-style oversized column radiators — Bisque Classic 3-Column matt black, sized 50–70% larger than legacy); Heatmiser NeoHub multi-zone control 5 zones. Crittall-style internal partitions: 2 internal partitions creating broken-plan separation between hall/reception and reception/dining (£18,500 total). Weeks 19–22: Final fix + decorating. Kitchen install (Howdens Greenwich shaker bespoke-painted Farrow & Ball Lichen, granite, Miele); 2 bathrooms; decorating heritage palette (Edwardian Sage, Bone, Inchyra Blue); period light fittings (Original BTC, Davey Lighting); commissioning ASHP + MVHR; airtightness measured 4.8 m³/h/m² @50Pa (acceptable for heritage retrofit); ASHP SCOP 3.74 measured first 8 weeks.

Outcome

EPC E (48) → B (84) — exceeded target B; achieved through fabric (loft 400mm + cavity fill where applicable + slim-DG sashes), heating (ASHP all-electric), and MVHR contribution. All 11 original sash windows restored not replaced; 5 replacements indistinguishable from originals from street (Bromley CA officer signed off zero amendments). 64m original cornices + ceiling roses preserved; 28m replication seamless match. Pitch pine parquet restored across ground floor. Crittall broken-plan effect successful — preserves original room rhythm while creating contemporary flow. ASHP SCOP measured 3.74 (predicted 3.6 — exceeded); MVHR delivers measured CO2 average 620 ppm; heating bills £2,800/year (pre-retrofit £3,600/year gas + electric) — modest saving but full electrification + heritage retention prioritised. Property valuation: pre-renovation £1.1M; post-renovation £1.32M (£220,000 uplift on £285,000 spend — 77% gross ROI). Featured in Period Living magazine May 2026 issue. Bromley Civic Society award for sympathetic conservation area renovation. Builderr second BR2/Shortlands case study; Bromley borough portfolio 3 case studies total.