The measures that move a solid wall house from D to C.
A Liverpool investor, a Manchester agent and a homeowner in Wavertree asked us the same thing in one week. What does it actually take to get a terraced house to EPC C. Here is the honest version.
Start from where the house is
The EPC is a model, not a measurement. It scores the house on its construction, insulation, heating, hot water, lighting and glazing against standard assumptions about how a household lives. A pre 1919 solid brick terrace with a combi boiler, double glazing and 100mm in the loft usually lands at low D. The same house with no loft insulation and an old boiler sits at E. The gap to C is typically 10 to 20 points, and each measure is worth a fairly predictable number of them.
The measures that move it
Loft insulation topped up to 270mm is the cheapest points on the sheet, usually four to eight. Low energy lighting throughout is one or two points for almost nothing. A condensing boiler with a room thermostat and thermostatic radiator valves is worth a lot if the current one is old, very little if it is already an A rated combi. Cavity wall insulation is a big win where there is a cavity, which in most Liverpool terraces there is not. Solid wall insulation, inside or out, is the measure that gets a solid wall house over the line, typically 10 to 15 points, and it is also the expensive one. Floor insulation and secondary glazing help at the margins. Solar panels score well but only on a suitable roof.
What does not help as much as people think
New windows, if the old ones were already double glazed. A smart thermostat on its own. Replacing a working boiler like for like. Draught proofing, which matters enormously for comfort and bills but scores modestly.
A realistic package
For a typical D rated terrace, loft top up, lighting, controls and internal wall insulation to the two external walls gets to C in most cases, at a cost in the region of £6,000 to £10,000 depending on the house. The government’s own estimate for the average private rented property sits at the lower end of that. If the house is at E, budget more and expect the boiler to be part of it.
Get the sequence right
Insulating a solid wall house without dealing with ventilation causes the damp and mould problems that badly done retrofit is known for. The order is fix defects, sort ventilation, then insulate, then heating. That is the whole point of a Retrofit Assessment. If you just want to know your own house’s route to C, the EPC to C plan is £45 with any EPC.
Point values above are typical ranges from current RdSAP and will change when the new EPC metrics arrive. Treat them as a guide, not a promise. Checked 20/09/2026.
Act Now Energy Ltd is ECMK accredited (Reg. ECMK307661) and TrustMark registered for retrofit assessment (TMLN 4110101), led by a Chartered Construction Manager (MCIOB), covering Liverpool, Merseyside and the North West. Call 0777 888 80 80 or email info@actnowenergy.co.uk.
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Act Now Energy Ltd is a company registered in England and Wales, company number 16818951. ECMK Reg. ECMK307661 | TrustMark Licence TMLN 4110101
Registered office: 50 Picton Road, Wavertree, Liverpool, L15 4LH
info@actnowenergy.co.uk | 0777 888 80 80
© 2026 Act Now Energy Ltd. Company No. 16818951.Photos: Mornington Terrace and Rodney Street, Liverpool by Rodhullandemu (CC BY-SA 4.0), Hope Street by Peter Holmes and Wavertree by Bill Boaden via geograph.org.uk (CC BY-SA 2.0), all via Wikimedia Commons, cropped