If the walls are coming off and the floors are coming up, the cost of upgrading insulation, draught-proofing and ventilation falls dramatically. The labour to do it is already on site, the access is already there, and the finishes are already off. Skipping these upgrades during a renovation and trying to retrofit them later usually costs three to five times more for the same result. So if you are doing structural or significant interior work this summer, the energy decisions need to be locked in now.
This guide is the practical version of what we recommend at TD Property Renovations when homeowners are planning a renovation in 2026. It covers the upgrades that genuinely move the needle on comfort and running costs, the ones that have a quick payback, and the regulatory minimums under the current Building Regulations.
The upgrades worth building in while the house is open
Wall insulation. If internal walls are stripped to brick, internal wall insulation can be added for a fraction of the cost of doing it as a separate retrofit. Solid-wall Victorian and pre-1930s terraces benefit most, because they have no cavity to insulate externally without changing the look of the property. We typically use a calcium silicate or breathable wood-fibre system depending on damp risk, with a vapour-controlled finish.
Floor insulation. Suspended timber floors lose a surprising amount of heat. If the floorboards are coming up anyway during a full house renovation, insulation between the joists with mineral wool or rigid board is straightforward and inexpensive. Solid concrete floors are harder to upgrade unless they are being replaced, in which case insulation underneath the new slab is mandatory.
Roof and loft insulation. The cheapest energy upgrade in the country, and the one that pays back fastest. Where loft access is available, topping up insulation to 300mm should be a default. Where the roof is being relined or replaced, sarking-level insulation is the proper time to spec it. Our full house renovation guide covers how this fits into a bigger programme.
Windows and doors. Where windows are being replaced, the cost difference between standard double-glazed units and high-performance triple-glazed or A+ rated units is smaller than people expect, particularly on the bigger openings. Door upgrades pay back in comfort: a proper insulated composite door at the main entrance is one of the most noticeable changes in the house.
Ventilation: the upgrade that protects everything else
A well-insulated house with poor ventilation is a damp house. Modern Building Regulations require background ventilation in every habitable room, mechanical extract in kitchens and bathrooms, and proper purge ventilation. If you are upgrading the thermal envelope, the ventilation strategy needs to be upgraded at the same time. The relevant standards are set out in Approved Document F (Ventilation) alongside the energy rules in Approved Document L.
Mechanical extract ventilation with humidity sensors in kitchens and bathrooms is the standard upgrade for most renovations. Full mechanical ventilation with heat recovery (MVHR) is a bigger system, more expensive and more disruptive to install, and worth considering on whole-house renovations with high airtightness. We recommend MVHR where the rest of the fabric is tight enough to justify it, not on every job.
The mistake we see most often is upgrading insulation without upgrading ventilation. The result is condensation on cold spots, black spots in corners, and damp behind wardrobes. None of this is the insulation’s fault — it is a ventilation failure — but the homeowner ends up blaming the renovation.
Heating: what changes when the fabric improves
A house with upgraded insulation and ventilation needs less heating than the old one. That means the existing boiler may be oversized, and the radiator sizing needs to be reviewed. Underfloor heating becomes more practical because the heat load is lower. Heat pumps become viable in properties where they would not have worked before. The whole heating strategy should be re-thought once the fabric upgrade is decided, not bolted on after.
Government guidance on energy upgrades and available grant schemes is collected on the official gov.uk energy efficiency pages. We are not financial advisers, but we are happy to flag the schemes a project might qualify for so a homeowner can take the relevant decisions with their accountant or energy assessor.
If you are also re-laying a hallway or a kitchen floor as part of the renovation, electric underfloor heating mats are a low-cost addition that lifts comfort substantially. Wet underfloor heating is a bigger commitment and works best as a primary heat source in well-insulated rooms.
Order of operations and what to ask for at quote stage
The right order on a renovation is: fabric first (insulation, draught-proofing, windows), then ventilation, then heating. Doing it the other way round wastes money. A heating system specified before the fabric is decided is almost always oversized. A ventilation strategy specified before the air-tightness is known is almost always wrong.
At quote stage, ask three things. What insulation is being added, where, and to what U-value or specification? What ventilation strategy is being installed? How is the heating being adjusted to match the new fabric? If those three answers are vague, the quote is not detailed enough. Our quotes always set the energy specification out clearly, because the homeowner is entitled to know what they are paying for. We discuss this on every job we project manage start-to-finish across the North West.
Frequently Asked Questions
Do I need to upgrade insulation during a renovation by law?
When you carry out building work that affects the thermal envelope, the upgraded element must meet the standards set out in Approved Document L of the Building Regulations. So in practice, yes — renovation work routinely triggers a regulatory requirement to bring the affected fabric up to current standards.
How much do energy upgrades add to a renovation budget?
On a typical North West renovation, properly specified energy upgrades add 5 to 10 per cent to the build cost. The payback in reduced running costs and improved comfort is significant, and trying to retrofit the same upgrades later typically costs three to five times more.
Should I install a heat pump during my renovation?
It depends on the fabric. A heat pump works best in a well-insulated, well-ventilated house with appropriately sized emitters (large radiators or underfloor heating). If you are doing a full fabric upgrade, a heat pump becomes a sensible option. If you are not, a modern condensing gas boiler is usually still the right answer.
What about solar PV?
Solar PV makes sense if the roof has decent south-east to south-west orientation, no significant shading and the household uses electricity during daylight hours. It is independent of the rest of the renovation, but installing the cabling and inverter during a renovation is much easier than after.
Will I need an EPC after the work?
You will not be legally required to get a new EPC after a renovation unless you are selling or letting the property. That said, a post-works EPC is a useful record of the upgrades, and it is worth having on file for any future grant or planning application.
Can you arrange the energy assessor?
Yes. We work with independent energy assessors and structural engineers across the North West and can arrange the relevant assessments as part of the project. The homeowner sees the cost itemised separately so it stays transparent.
Renovating is the cheapest time you will ever have to upgrade the energy performance of a house. If you are planning structural or interior work this summer in Widnes, Liverpool, Runcorn or anywhere in the wider North West, book a site visit and we will tell you straight which upgrades pay back and which are not worth the line item.
