Builders first. That is the point.

From building houses to rebuilding how they perform

Delpol has spent years on Oxfordshire’s building sites — extensions, conversions, renovations, the full trade span of a working construction firm. Somewhere along the way, the interesting problems stopped being about adding rooms and started being about the buildings themselves: why a solid-wall terrace is cold with the heating on full, why a sealed-up house grows mould, why a new boiler in an old house changes so little.

Answering those questions properly meant learning a second discipline on top of the first — heat loss, moisture movement, airtightness, ventilation design — and then proving it on real houses. Sixteen-plus whole-house retrofit projects later, across Victorian terraces, North Oxford villas, conservation-area houses and rubble-stone village homes, that is what this company is: building science in the hands of people who actually build.

We spec it, we design it, we build it

Most retrofit fails in the handovers — designer to contractor, trade to trade, intention to execution. We removed the handovers. The person who surveys your house works for the same company that draws the build-ups, sequences the trades and puts the insulation on the wall. Our own crew delivers the fabric works — insulation, roofing, windows, floors, airtightness, ventilation, electrics — and heat pumps and solar are designed and coordinated by us, installed with our managed certified partners. When something is concealed, we photograph it first. When something is finished, one company is answerable for it.

Materials we would put in our own homes

Old walls breathe, so we insulate them with materials that breathe: wood fibre, lime, cork, calcium silicate, finished in vapour-open plasters and paints. Not because natural materials are fashionable, but because on pre-cavity buildings they are the technically correct answer — they buffer moisture instead of trapping it, and they fail safe. Where modern materials are the right tool — mineral wool in a loft, EPS on a rendered detached wall — we use them without ceremony. The rule is always the same: the material must suit the wall, and the build-up must stay moisture-safe for decades, not just past handover.

What we ask you to judge us on

Not our words — the register. Our Howard Street project took a c. 1900 East Oxford terrace from EPC E (49) to B (89), with an 87% carbon cut, on the government’s public energy-certificate register. Orchard House, a 1970 stone house near Banbury, was certified EPC B a year after leaving oil. The case studies on this site set out, project by project, exactly what was designed, what was delivered and what the evidence is — and where we cannot evidence a number, we do not claim it.

Delpol is a member of the Federation of Master Builders — listed on the FMB register for general building, roofing, windows, internal and external wall insulation, and lime plastering. Our trades are City & Guilds qualified, and our larger retrofits are delivered under FMB building contracts.