Home Heat Pump Guide

Improving Your EPC Before Installing a Heat Pump

If you are planning to install a heat pump, improving your home's energy performance beforehand is one of the smartest moves you can make. A better-insulated home means a smaller heat pump, lower running costs, and a more comfortable living environment. You do not need to spend a fortune — many of the most effective improvements are surprisingly affordable.

While there is no minimum EPC requirement for the Boiler Upgrade Scheme grant, targeting EPC band C or above before your heat pump goes in will deliver the best results. This guide walks through the most impactful improvements, ranked by cost-effectiveness, so you can decide where to invest your money and time.

Quick Win 1: Loft Insulation Top-Up

Loft insulation is the single most cost-effective energy improvement for most UK homes. Heat rises, and without adequate insulation, up to 25 per cent of your home's heat escapes through the roof. Current building regulations recommend 270mm of mineral wool or equivalent.

What to check

Climb into your loft and measure the depth of existing insulation. Many homes have insulation, but only 100mm or so — the standard when it was installed in the 1980s or 1990s. Topping up from 100mm to 270mm can reduce loft heat loss by 40 to 50 per cent.

Cost and impact

  • DIY cost: £300 to £500 for mineral wool rolls from a builders' merchant. A straightforward weekend job for most homeowners.
  • Professional installation: £400 to £800 for a typical three-bedroom semi.
  • EPC impact: Can improve your score by 5 to 15 points, potentially moving you up one band.
  • Energy saving: £100 to £200 per year on heating costs.
  • Heat pump benefit: Reduces heat demand by 1 to 2 kW, potentially allowing a smaller unit.

Important considerations

Ensure your loft has adequate ventilation — insulation should not block eaves ventilation. If you use your loft for storage, you will need to raise the boarding above the insulation level using loft legs or a raised platform. Never compress insulation by placing boards directly on top of it, as this severely reduces its effectiveness.

If your loft is converted or has a room in the roof, insulating between and under the rafters is more complex and expensive but still worthwhile. Rigid insulation boards or spray foam are common solutions.

Quick Win 2: Cavity Wall Insulation

If your home was built between the 1920s and the 1990s, it probably has cavity walls — two layers of brick or block with a gap between them. If that cavity is empty, filling it with insulation is one of the most effective improvements available.

How to tell if you have cavity walls

Look at the external brickwork. If the bricks are all laid lengthways (stretcher bond), you almost certainly have cavity walls. If you see a mix of lengthways and sideways bricks (Flemish or English bond), you likely have solid walls. Your existing EPC should also state the wall type.

Cost and impact

  • Cost: £400 to £800 for a typical semi-detached house. Installed by drilling small holes in the external mortar joints and injecting insulation.
  • Time: Half a day to a full day for most properties.
  • EPC impact: Can improve your score by 10 to 20 points — one of the biggest single improvements available.
  • Energy saving: £150 to £300 per year on heating costs.
  • Heat pump benefit: Reduces heat demand by 2 to 4 kW. This can make a dramatic difference to heat pump sizing.

When cavity wall insulation is not suitable

Cavity wall insulation is not appropriate for all homes. It should not be installed if your walls are exposed to severe driving rain (common in western Scotland and Wales), if the cavity is narrower than 50mm, or if there are existing damp problems. A reputable installer will survey the property and advise whether it is suitable.

For homes with solid walls — typically pre-1920s properties — internal or external wall insulation is an option but considerably more expensive (£5,000 to £15,000). See our guide to heat pumps in Victorian houses for more on solid wall properties.

Quick Win 3: Draught-Proofing

Draught-proofing is arguably the best value energy improvement you can make. It costs very little, can be done as a DIY project, and the results are immediate — both in terms of comfort and energy savings.

Where to focus

  • External doors: Fit draught strips around the frame and a brush strip or letter box cover. Cost: £10 to £30 per door.
  • Windows: Self-adhesive foam or rubber strips around opening casements. Cost: £3 to £10 per window.
  • Loft hatch: Fit a seal around the hatch frame and insulate the hatch itself. Cost: £10 to £20.
  • Floorboards: Fill gaps between boards with flexible filler. Cost: £20 to £50 for a room.
  • Skirting boards: Seal the gap between skirting and floor/wall with decorator's caulk. Cost: £10 to £20 per room.
  • Pipework holes: Seal gaps where pipes enter from outside using expanding foam or sealant. Cost: under £10.
  • Chimneys: If not in use, fit a chimney balloon or cap. Cost: £20 to £40.

Cost and impact

  • Total DIY cost: £100 to £300 for a whole house.
  • Professional draught-proofing: £200 to £500.
  • EPC impact: Modest — 1 to 5 points — but the real benefit is in comfort and actual energy savings.
  • Energy saving: £50 to £100 per year.
  • Heat pump benefit: Reduces uncontrolled ventilation heat loss. Particularly important for homes with significant draught problems.

Quick Win 4: Glazing Improvements

If you still have single glazing, upgrading to double glazing is a significant improvement. If your budget does not stretch to full replacement, secondary glazing offers a more affordable alternative. See our detailed guide on double glazing and heat pump efficiency.

Cost and impact

  • Double glazing: £400 to £800 per window. EPC improvement of 5 to 15 points for a full house. Energy saving of £100 to £250 per year.
  • Secondary glazing: £100 to £350 per window. Approximately 60 to 70 per cent of the benefit of full double glazing.
  • Window film: £10 to £30 per window. Modest improvement but cheap and easy to apply.

If you already have double glazing, this is not a priority. Even 20-year-old double glazing provides adequate insulation for a heat pump installation.

Quick Win 5: LED Lighting

This might seem unrelated to heat pumps, but replacing old halogen or incandescent bulbs with LEDs improves your EPC score and reduces electricity consumption — which matters more when your heating also runs on electricity.

Cost and impact

  • Cost: £2 to £8 per bulb. Most homes need 15 to 30 bulbs replaced.
  • Total cost: £30 to £200 for a full house.
  • EPC impact: 1 to 5 points — small but meaningful when combined with other improvements.
  • Energy saving: £30 to £80 per year on lighting costs.

LED lighting is such an easy win that there is no reason not to do it. Most homeowners can replace all the bulbs in an afternoon.

Quick Win 6: Hot Water Cylinder Insulation

If you have an existing hot water cylinder (common with traditional boiler systems), ensure it has a factory-fitted foam jacket or a separate insulation jacket at least 80mm thick. An uninsulated cylinder loses heat constantly — wasting energy and money.

Cost and impact

  • Cost: £15 to £30 for a cylinder jacket from any DIY store.
  • EPC impact: 1 to 3 points.
  • Energy saving: £20 to £50 per year.

When your heat pump is installed, you will likely get a new, well-insulated hot water cylinder as part of the package. But insulating your existing one now will save money in the meantime.

Bigger Investments: When They Make Sense

Solid wall insulation

For homes with solid walls — typically pre-1920s — internal or external wall insulation makes a huge difference to heat loss but comes at significant cost. External wall insulation (£8,000 to £15,000) wraps the outside of your home in insulation and a new render finish. Internal wall insulation (£5,000 to £10,000) adds insulation boards to the inside of external walls, reducing room sizes slightly.

Either option can improve an EPC by 15 to 30 points and reduce heat demand by 3 to 6 kW — enough to significantly change the heat pump size required. If you are planning a major renovation of a solid-walled property, this should be high on the list.

Floor insulation

Insulating a suspended timber floor costs £800 to £2,500 depending on access and method. It is most cost-effective when access from below is available (via a cellar or crawl space). EPC impact is typically 3 to 8 points.

Solar panels

While solar panels do not directly affect heat pump performance, they do improve your EPC score (often by 10 to 15 points) and can significantly offset your heat pump electricity costs. A typical 4 kW system costs £5,000 to £7,000 and can provide 30 to 50 per cent of a heat pump's annual electricity needs.

Prioritising Your Improvements

Not everyone has the budget to do everything at once. Here is a recommended priority order based on cost-effectiveness for heat pump preparation:

  1. Draught-proofing — Cheapest, biggest comfort impact per pound spent
  2. Loft insulation top-up — Low cost, high impact on heat loss
  3. LED lighting — Trivial cost, easy to do
  4. Hot water cylinder jacket — Very cheap, immediate benefit
  5. Cavity wall insulation — Moderate cost, massive impact (if applicable)
  6. Glazing upgrades — Significant cost but worthwhile if you have single glazing
  7. Floor insulation — Good value for suspended floors with access
  8. Solid wall insulation — Expensive but transformative for solid-walled homes

Items 1 to 4 can typically be completed for under £500 total. Items 5 and 6 push the total to £1,500 to £5,000. Items 7 and 8 are for homeowners planning more significant investment.

Timing: Before or After the Heat Pump?

The ideal sequence is to complete insulation improvements before the heat pump is installed. This allows your installer to size the heat pump for your improved home, rather than your current one. A heat pump sized for a poorly insulated home will be oversized once you add insulation, which can cause efficiency problems.

However, perfection should not be the enemy of progress. If you can only afford the heat pump now and insulation later, go ahead with the installation. A good installer can discuss future insulation plans and factor them into the design to some extent. Some installers can adjust the heat pump settings after insulation work is completed.

The most important thing is to make the switch from fossil fuels. You can always improve insulation incrementally — each improvement will reduce your running costs further. Use our heat pump calculator to see how different insulation levels affect costs, and get quotes from MCS-certified installers who can advise on the best approach for your home.

Funding and Grants for EPC Improvements

Several schemes can help with the cost of insulation improvements:

  • Great British Insulation Scheme: Provides insulation measures to homes in council tax bands A to D in England and Wales. Covers loft, cavity wall, and solid wall insulation.
  • ECO4: Available to households on qualifying benefits. Covers a wide range of energy efficiency measures.
  • Local authority grants: Many councils offer additional funding for energy efficiency improvements. Check with your local authority.
  • Scottish Home Energy Efficiency Programmes (HEEPS): Area-based schemes in Scotland providing insulation and other measures.
  • Nest scheme (Wales): Free home energy improvements for eligible households.

Your heat pump installer or local energy advice centre can help you navigate the available funding options.

Frequently Asked Questions

What is the cheapest way to improve my EPC rating?

Draught-proofing (£100-£300), loft insulation top-up (£300-£500 DIY), LED lighting (£30-£200), and a hot water cylinder jacket (£15-£30) are the cheapest improvements. Together, they can improve your EPC by 5 to 20 points for under £1,000.

How much can I improve my EPC by?

It depends on your starting point. A D-rated home with unfilled cavity walls, inadequate loft insulation, and old lighting could realistically reach high C or low B with the improvements listed in this guide. A poorly insulated Victorian home might move from F to D or E with affordable measures, or to C with significant investment in wall insulation.

Do I need to get a new EPC after making improvements?

Not necessarily. Your heat pump installer will conduct a detailed heat loss survey that accounts for your actual insulation levels, regardless of what the EPC says. However, a new EPC may be required if your existing one has expired (they last 10 years) or if you plan to sell or let the property.

Can my heat pump installer advise on insulation?

Good installers will advise on the most impactful improvements during the survey. They can show you how different insulation levels affect heat pump size and running costs. Some installers can coordinate insulation work before the heat pump installation.

Is it worth improving insulation if I am renting?

If you are a tenant, speak to your landlord. Rental properties must meet a minimum EPC of E in England and Wales (likely increasing to C in the future). Landlords may be eligible for grants to fund improvements. As a tenant, you benefit directly from lower energy bills and better comfort.

Will improving my EPC make my home warmer right away?

Yes. Insulation and draught-proofing improvements reduce heat loss immediately, making your home more comfortable with your existing heating system. You will notice the difference before the heat pump arrives.