Floor Insulation & Draught Proofing: Low-Cost EPC Improvements
Floor insulation costs £1,000–£3,000 (1–3 SAP points) and draught proofing costs £200–£500 (1–2 SAP points). Useful additions to a broader improvement plan.
Floor Insulation
What Is It?
Floor insulation reduces heat loss through the ground floor. The method depends on your floor type:
Suspended timber floors (common in pre-1950s properties): Insulation is fitted between the joists from below (if there is a crawl space) or by lifting floorboards and fitting rigid board or mineral wool between the joists.
Solid concrete floors (common in post-1950s properties): Insulation is fitted on top of the existing floor using rigid foam boards with a new floor surface on top. This raises the floor level by 50–100mm, which may affect doors and skirting boards.
How Much Does It Cost?
| Floor Type | Typical Cost |
|---|---|
| Suspended timber (from below, with access) | £800 – £1,500 |
| Suspended timber (lifting boards) | £1,200 – £2,500 |
| Solid concrete (overlay) | £1,500 – £3,000 |
EPC Impact
Floor insulation typically adds 1–3 SAP points. This is relatively modest compared to wall and loft insulation. The impact is greater for ground-floor flats and bungalows, where the floor represents a larger proportion of the total heat loss surface.
Is It Worth It?
Floor insulation sits in the "useful but not priority" category for most properties. Do it when:
- You have already done loft insulation, cavity walls, and heating improvements
- You still need 1–3 extra SAP points to reach Band C
- The property has a suspended timber floor with easy access from below
- Floors are being replaced anyway (combine improvement with maintenance)
The cost per SAP point is relatively high compared to loft insulation or LED lighting. However, it provides genuine comfort improvements — cold floors are a common tenant complaint.
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Draught Proofing
What Is It?
Draught proofing involves sealing gaps around windows, doors, loft hatches, letterboxes, floorboards, and other openings where cold air enters the property. Common measures include:
- Foam, brush, or rubber strips around door and window frames
- Draught excluders for letterboxes and keyholes
- Chimney draught excluders or balloon
- Sealing gaps around floorboards and skirting boards
- Loft hatch seal and insulation
How Much Does It Cost?
| Measure | Typical Cost |
|---|---|
| DIY draught strips (full property) | £50 – £150 |
| Professional draught proofing | £200 – £400 |
| Chimney balloon or cap | £20 – £50 |
| Letterbox draught excluder | £10 – £30 |
| Total (professional, typical property) | £200 – £500 |
EPC Impact
Draught proofing adds 1–2 SAP points. Like LED lighting, the individual impact is small but it contributes to a cumulative improvement when combined with other measures. The SAP calculation factors in air permeability, and sealed properties score better.
DIY Friendly
Draught proofing is one of the most accessible DIY improvements. A landlord or tenant can do most of the work with materials from any hardware shop. The only measure that may require a professional is sealing around the loft hatch (if combined with loft insulation work).
Ventilation Warning
Do not seal up the entire property. Adequate ventilation is essential for preventing condensation and mould — a serious issue in rental properties. Key rules:
- Never block trickle vents in windows
- Never seal extractor fan outlets in bathrooms and kitchens
- Never block air bricks providing underfloor ventilation
- Do not draught-proof rooms with gas appliances unless they have adequate fixed ventilation
Over-sealing can create worse problems than draughts. If in doubt, consult a ventilation specialist.
Combining These Measures
Floor insulation and draught proofing work well as additions to a broader improvement package:
| Package | Cost | SAP Gain |
|---|---|---|
| Floor insulation + draught proofing | £1,200 – £3,500 | +2–5 points |
| Above + loft insulation + LEDs | £1,600 – £4,500 | +6–12 points |
| Above + cavity walls + heating controls | £3,000 – £7,500 | +12–22 points |
The key is prioritisation. Check your property on EPCFix to see which improvements give you the most SAP points per pound for your specific property.
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