Renewables for Listed & Heritage Buildings in Cornwall

Listed Building Consent is a separate consent regime from planning permission, governed by the Planning (Listed Buildings and Conservation Areas) Act 1990. LBC is required for any works that affect the 'character of the building as a building of special architectural or historic interest' — which includes internal works, even if invisible from outside. For renewable retrofits this typically means: (1) heat pump outdoor unit siting and mounting, (2) any external pipework or condensate drainage, (3) cylinder placement where it requires alteration to historic joinery or fabric, (4) solar PV on any roof slope, (5) battery siting where it requires alteration to outbuildings or cellars, (6) any boiler flue removal or chimney works.

Cornwall Council's Historic Environment Service handles LBC applications, typically taking 8-12 weeks. Application fee is currently £0 for LBC (unlike planning at £258), but a Heritage Statement is required — a document setting out the property's significance, the proposed works, the impact on heritage values, and the justification. We produce Heritage Statements as part of our standard listed-building service, costing £350-£650 depending on property grade and complexity. For Grade I and Grade II* properties, Historic England must be consulted, adding 2-3 weeks. Our approval rate on LBC applications stands at 96% first-time, with the remainder approved after minor modifications.

See our full LBC guide for application timeline and document checklist.

The single most contentious element of a listed-building heat pump install is outdoor unit siting. Conservation officers will reject visually prominent installations, particularly on principal elevations, in walled gardens of significance, or where the unit interrupts a designed view. Acceptable locations, in order of typical approval likelihood, are:

• Behind existing outbuildings, garden walls or hedges — entirely screened from any public view. Always our first choice. Pipework runs underground in shallow trench.
• Within existing outbuildings (former coal stores, dairies, wash-houses, stables) — split-system heat pumps where the outdoor unit becomes effectively indoor, with louvred openings for airflow. We have done this at three Grade II* estate cottages on Lanhydrock-adjacent land.
• Rear yards and service areas not visible from any public realm or principal facade. Usually acceptable on Grade II buildings.
• Flat-roof additions (1960s-2000s extensions to listed cores) — units can sit on the extension roof with acoustic mounts.
• Below ground in light wells or 'pits' — purpose-built sunken enclosures with acoustic louvres. More expensive (£3,500-£5,500 additional) but secures consent in highly sensitive locations.

Mitsubishi Ecodan units (33 dB at 1m for the smaller models) are our most-approved spec for listed properties due to the lowest acoustic signature. Vaillant aroTHERM Plus R290 in larger sizes is approved where capacity demands. We avoid Daikin Altherma 3 H HT for listed work due to higher acoustic output.

A 300L unvented cylinder is 1.95m tall and 600mm diameter. Hiding it inside a listed building requires creative spatial thinking. Successful placements on our recent projects:

• Cellar installation — common in Georgian and Victorian listed houses across Truro, Falmouth and Penzance. Cellar location keeps cylinder out of sight, allows long-run gravity-vented installation if no roof access, and provides natural temperature stability.
• Estate room/service wing — at larger country houses (3,000ft²+) we install in the original service wing, often the former kitchen scullery or boot room. Cylinder sits behind period joinery.
• Loft (cold-roof) installation — possible where loft access permits 1.95m clearance and structural assessment confirms joist loading capacity. Insulated all-round with breathable insulation to avoid condensation.
• Bespoke joinery enclosure — we have built reproduction Georgian panel cupboards and stripped-pine kitchen larder boxes around cylinders, with concealed access doors. £1,200-£2,800 per enclosure depending on joinery complexity.

Pipework routes use existing service voids wherever possible: behind dado rails, under floorboards (lifted and refitted using original screws), through redundant chimney flues, or in dedicated boxed runs along skirting that match existing profiles. We do not chase masonry on Grade I or Grade II* properties without explicit LBC approval.

Conventional bolt-on solar PV is rarely approved on listed properties. Three approaches typically achieve consent:

• In-slate / in-pantile fully integrated — Viridian Clearline Fusion, GSE in-roof, or Solarcentury Sunstation. Panels sit within the roof plane, flashed like a rooflight, reading visually as a roof element. Approved on 90%+ of LBC applications for non-principal roof slopes.
• Slate-coloured all-black panels with black frames — REC Alpha Pure-R, LG Neon H Black, SunPower Maxeon 6. Mounted with slate hooks (no slate removal), low-profile rails, minimal protrusion. Approved on rear and side slopes of Grade II properties typically.
• Solar slate tiles — actual slate-sized PV elements that replace individual slates. Brands include the new Tesla Solar Roof v3.5 (now available in UK) and several specialist UK manufacturers. Highest visual integration, highest cost (£2,200-£2,800 per kWp installed vs £1,650/kWp for conventional).

Cornwall Council heritage officers have expressed in-principle support for in-slate PV across both listed and conservation-area properties, particularly on rear and concealed slopes. Grade I properties remain more challenging — typically restricted to outbuildings, modern extensions, or detached ancillary structures rather than the principal heritage asset itself.

Battery placement in listed properties benefits from one chemistry choice: lithium iron phosphate (LFP, LiFePO4) rather than NMC. LFP batteries are non-flammable, do not undergo thermal runaway, operate safely across a wider temperature range (-20°C to +60°C), and have far longer cycle life (6,000+ cycles vs 3,500 for NMC). This makes them suitable for installation in cellars, basements, larder rooms and historic outbuildings where temperature is variable.

Our recommended LFP battery products for listed properties:

• Givenergy Giv-Bat 9.5 / 13.5 — wall-mounted, IP65, suitable for outbuildings and cellars. 6,000 cycle warranty.
• Pylontech US5000 / Force-L2 — stackable, low profile, popular for cellar installations.
• Fox ESS HV2600 — vertical stacked, fits in 600mm corridor footprint.
• Tesla Powerwall 3 (LFP from 2024) — single 13.5kWh unit, wall-mounted, requires garage or outbuilding (not internal living space due to size).

We have installed LFP batteries in cellars at four Grade II Georgian houses in central Truro, two Grade II* coach houses on Trelissick-adjacent estates, and the basement of a Grade II rectory near Lanhydrock. All passed LBC on first application.

Cornwall Council offers pre-application (pre-app) advice for listed building works, currently £210 + VAT for a written response from a conservation officer. We strongly recommend this on all Grade I, Grade II* and complex Grade II projects. The pre-app process: we submit drawings, product datasheets, the proposed Heritage Statement, photos, and a covering letter. The conservation officer (typically allocated by parish) reviews and responds within 4 weeks with written advice on whether the proposals are likely to be approved, modifications required, and whether Historic England consultation will be triggered.

We have working relationships with the lead conservation officers covering Carrick (Truro/Falmouth/Roseland), Penwith (Penzance/St Ives/Lands End), Kerrier (Helston/Lizard/Camborne), North Cornwall (Bodmin/Padstow/Wadebridge), Restormel (St Austell/Newquay) and Caradon (Liskeard/Looe/Saltash). This allows us to gauge in advance which approaches are likely to succeed on which property types in which areas, reducing application risk significantly.

Conservation officers approve interventions that can be removed without trace if the building's future owner wishes to reverse them. Every design decision on our listed projects is assessed for reversibility:

• Heat pump pipework uses existing flue/service routes or surface-mounted boxed runs (removable) rather than chased channels (permanent).
• Radiator brackets are bolted into mortar joints, not stone faces, so removal leaves no permanent damage.
• Cylinder enclosures are freestanding joinery or removable cupboards, not built-in alterations.
• Solar fixings use slate hooks rather than slate removal/replacement where possible.
• Battery wall-mounts use rawl-plug fixings into modern blockwork additions, not historic stone.
• Cable routing follows existing electrical runs and is surface-clipped, not chased.

This principle, combined with our Heritage Statement documenting the rationale, has produced our 96% first-time approval rate on Cornwall Council LBC applications.

Grade II estate cottage, St Aubyn estate near Marazion: 1840s 3-bed granite cottage on the St Aubyn estate. Installed 12kW Mitsubishi Ecodan Zubadan in former coal store (now louvred), 250L cylinder in cellar, full radiator replacement, 3.2kWp Viridian Clearline Fusion on rear slope (not visible from any public footpath). Total cost £29,800 gross, £22,300 after BUS. LBC approved first application, 9 week timeline.

Grade II* coach house, Trelissick-adjacent: Former carriage building converted to dwelling 1990s. Installed 14kW Vaillant aroTHERM Plus R290 behind original yard wall, 300L cylinder in original tack room, 4kWp solar with Givenergy 13.5kWh battery in basement. Total £37,500, £30,000 after BUS. NT consultation required (informal — coach house outside NT ownership but within setting), approved 11 weeks.

Grade II Georgian townhouse, Lemon Street Truro: 1820s 4-storey terrace, 175m². Installed 16kW aroTHERM Plus in rear lightwell (sunken enclosure, custom acoustic louvres), 300L cylinder in basement, 4kWp solar on rear roof slope (in-slate Viridian), 9.5kWh Pylontech battery in basement. Total £42,800 gross, £35,300 after BUS. Pre-app advice obtained at £210, LBC approved 10 weeks.