If your EPC mentions “Loft insulation (less than 100mm)” or “No loft insulation (assumed)”, you’re almost certainly losing more heat than you need to through the roof – and leaving EPC points on the table.
Loft insulation is one of the cheapest, most effective ways to improve your EPC rating, and it’s often the first upgrade energy assessors recommend.
This guide explains:
- How loft insulation affects your EPC score
- Typical costs and bill savings
- Whether it’s enough to move you up a band on its own
For a wider list of upgrade options, see 27 Ways to Improve Your EPC Rating. Here, we’ll focus purely on the roof.
How EPCs treat loft insulation
The EPC assessor records:
- Whether your property has a pitched roof and an accessible loft
- How much insulation is present (e.g. 50mm, 100mm, 270mm)
- Any known limitations (e.g. no access, sloping ceilings, flat roofs)
The calculation then estimates how much heat is lost through the roof. A well-insulated loft significantly reduces this, improving both:
- Your energy efficiency rating (the main A–G score)
- Your environmental impact rating (CO₂ emissions)
Properties with very little or no loft insulation are penalised heavily in the EPC model – which is why topping it up is such a common recommendation.
How much can loft insulation improve your EPC rating?
Exact EPC gains depend on:
- Your starting insulation level (e.g. 0mm → 270mm vs 100mm → 270mm)
- Property type and size (flat vs house, detached vs mid-terrace)
- Other factors like wall insulation and heating system
As a rough rule of thumb:
- Going from no insulation to 270mm can add 5–10 SAP points, sometimes more.
- Going from thin insulation (e.g. 50–100mm) to 270mm may add 3–6 SAP points.
For some properties, that can be enough to:
- Move from E to D or D to C when combined with other basic measures.
- Close a gap where you’re just 1–3 points short of the next band.
This is why loft insulation appears prominently in both How to Improve EPC from E to D and How to Improve EPC from D to C.
Typical costs and savings
Costs vary with insulation type, loft size and whether you DIY or hire a professional.
DIY loft insulation
- Materials (rolls of mineral wool or similar): often £200–£400 for an average 3-bed house.
- You’ll need safe access, suitable boards to walk on and care around wiring and fixtures.
DIY can be great for topping up existing insulation where the loft is easy to move around in and you’re confident with basic practical tasks.
Professional loft insulation
If access is tricky or you prefer not to DIY:
- Typical installation cost: £300–£700+ depending on loft complexity and location.
- Many installers also address ventilation, loft hatches and pipe/tank protection.
Annual savings
According to various UK energy-efficiency sources, typical savings for a gas-heated, semi-detached house can be around:
- £150–£250 per year when upgrading from no insulation to 270mm.
Exact figures will vary with energy prices and usage, but payback times are often quite short – especially if grants reduce your upfront cost.
Is loft insulation always the first upgrade?
In many homes, yes – but not always.
Loft insulation is often the first priority when:
- Your EPC explicitly warns of insufficient loft insulation.
- The loft is easily accessible and safe to work in.
- You haven’t done any other major fabric improvements yet.
Other measures may take priority when:
- You live in a top-floor flat with no individual loft space.
- The roof structure is unusual or already insulated in another way.
- You have very specific damp or condensation issues that need addressing first.
Use your property report from our EPC checker to see where loft insulation sits in your personalised list of recommendations.
Landlords: loft insulation and minimum standards
For landlords, loft insulation can be an essential part of meeting minimum EPC requirements:
- Poor roof insulation can drag a rental property into band F or G, risking non-compliance.
- Adding or improving loft insulation is usually low-disruption compared to other upgrades.
Improving roof insulation can make it easier to reach or maintain the required band, particularly if future changes raise the bar towards band C. For more on the rules, see:
How loft insulation works with other EPC improvements
Loft insulation is most effective when combined with:
- Wall insulation (cavity, internal or external, depending on property type)
- Floor insulation and targeted draught proofing
- Efficient heating systems and good controls
It makes sense to view it as part of a broader improvement plan:
- For budget-first ideas, see Cheapest Ways to Improve Your EPC Rating.
- For band-specific guidance, read How to Improve EPC from E to D and How to Improve EPC from D to C.
- For Victorian and solid-walled homes, see How to Improve EPC on Victorian House.
Grants and funding for loft insulation
Depending on your circumstances, you may not have to pay the full cost:
- National schemes such as ECO4 often fund or subsidise loft insulation for eligible households.
- Some local authorities run area-based schemes that include loft and cavity wall insulation.
We summarise the main options in Home Energy Grants UK 2025: Complete Guide to Funding (/insights/home-energy-grants-uk). Check this alongside your EPC recommendations to see whether you qualify.
FAQs
Is loft insulation enough to move me up an EPC band?
Sometimes. If you’re only a few SAP points short of the next band – and your loft is currently uninsulated or poorly insulated – topping up the loft can be enough. In many cases, though, you’ll need loft insulation plus one or two additional measures (like wall insulation or heating upgrades).
Do I need a new EPC after adding loft insulation?
Yes. The EPC is a snapshot at the time of assessment; it doesn’t auto-update. After completing loft insulation and any other significant improvements, you’ll need a new EPC assessment to capture your improved rating. See Is My EPC Still Valid? for validity rules.
Can loft insulation cause damp or condensation?
When done correctly with adequate ventilation, loft insulation should not cause damp problems – and may even help by keeping the house warmer. However, blocking essential airflow or insulating around existing moisture issues can create problems, so it’s important to:
- Maintain or improve roof ventilation.
- Avoid blocking air bricks or vents.
- Address known damp issues before adding large amounts of insulation.
What should I do next?
- Use the EPC checker to confirm what your current EPC says about your loft.
- Decide whether a DIY top-up or professional installation is right for you.
- Plan how loft insulation will fit into your wider upgrade strategy using 27 Ways to Improve Your EPC Rating.
As a relatively low-cost, high-impact measure, loft insulation is one of the best starting points for improving your EPC rating and cutting energy bills.