Your roof could be costing you £500-£800 every year in wasted heat. Up to 25-30% of your home’s heat escapes through a poorly insulated roof. Here’s how to fix that—and how to get the government to pay for most of it.
🔥 The Hidden Cost of Poor Roof Insulation
Heat Loss Through Your Roof
| Insulation Level | Heat Loss | Annual Cost* |
|---|---|---|
| No insulation | 25-30% of total | £600-£900 |
| Under 100mm | 15-20% | £350-£500 |
| 100-200mm | 8-12% | £200-£300 |
| 270mm+ (current standard) | 3-5% | £75-£125 |
*Based on average British home heating £2,500/year
The difference between no insulation and proper insulation: £500-£800 saved annually!
📊 Calculate Your Potential Savings
Quick Savings Estimator
Answer these questions:
-
What year was your home built?
- Before 1970: Likely no/poor insulation
- 1970-1990: Usually 50-100mm
- 1990-2010: Usually 100-150mm
- After 2010: Usually meets current standards
-
Check your attic insulation:
- Can you see joists? Insulation is too thin
- Insulation above joist level? Good
- 270mm+ (about 10 inches)? Excellent
-
Your estimated savings:
| Current Insulation | Add to 270mm | Annual Savings | Payback |
|---|---|---|---|
| None/very little | £800-£1,500* | £500-£700 | 1-2 years |
| 50-100mm | £600-£1,200* | £300-£400 | 2-3 years |
| 100-150mm | £500-£900* | £150-£250 | 3-4 years |
*After Energy Saving Trust grant of up to £1,500
Get exact savings calculation →
🏠 Types of Roof Insulation for British Homes
1. Attic Floor Insulation (Cold Roof)
Best for: Unused attic spaces
How it works: Insulation laid between and over ceiling joists
Materials:
- Mineral wool rolls (most common) - £15-25/m²
- Blown cellulose - £20-30/m²
- Sheep’s wool (eco option) - £30-40/m²
R-value target: 6.5+ m²K/W (270mm mineral wool)
Pros:
- ✅ Cheapest option
- ✅ DIY possible
- ✅ Highest Energy Saving Trust grants
Cons:
- ❌ Attic becomes cold
- ❌ Pipes/tanks need separate insulation
- ❌ Not suitable if attic is used space
2. Rafter Insulation (Warm Roof)
Best for: Converted attics, rooms in roof
How it works: Insulation fitted between/below rafters
Materials:
- PIR/PUR boards (best performance) - £35-50/m²
- Mineral wool - £20-30/m²
- Spray foam - £40-60/m²
R-value target: 4.5+ m²K/W
Pros:
- ✅ Keeps attic warm and usable
- ✅ Protects pipes/tanks
- ✅ Good for conversions
Cons:
- ❌ More expensive
- ❌ Professional installation needed
- ❌ May reduce headroom
3. Flat Roof Insulation
Best for: Extensions, garages with flat roofs
Options:
- Warm roof (insulation above deck) - Best performance
- Cold roof (insulation below deck) - Risk of condensation
- Inverted roof (insulation above waterproofing) - Premium solution
📈 Understanding R-Values and U-Values
R-Value (Thermal Resistance)
- Higher = Better insulation
- Measures resistance to heat flow
- UK target: R6.5+ for attic floors
U-Value (Thermal Transmittance)
- Lower = Better insulation
- Measures heat loss per m²
- UK target: 0.16 W/m²K or less for roofs
Material R-Values (per 100mm)
| Material | R-Value | Thickness for R6.5 |
|---|---|---|
| PIR/PUR boards | 4.5 | 145mm |
| Mineral wool | 2.4 | 270mm |
| EPS (polystyrene) | 2.6 | 250mm |
| Sheep’s wool | 2.4 | 270mm |
| Cellulose | 2.3 | 285mm |
💰 Energy Saving Trust Grants for Roof Insulation
The government will pay a significant portion of your insulation costs.
Available Grants (2025)
| Measure | Grant Amount | Typical Cost | Your Cost |
|---|---|---|---|
| Attic insulation | Up to £1,500 | £1,000-£2,500 | £0-£1,000 |
| Rafter insulation | Up to £3,000 | £3,000-£8,000 | £0-£5,000 |
| Flat roof insulation | Up to £3,000 | £2,000-£6,000 | £0-£3,000 |
One Stop Shop Bonus
If you combine insulation with other upgrades to achieve EPC B2:
- Higher grant rates
- Grants deducted upfront
- Fully managed process
Check your grant eligibility →
🌡️ Real British Homeowner Case Studies
Case 1: 1970s Semi-Detached, London 15
Before:
- No attic insulation
- EPC: E1
- Heating cost: £2,800/year
- Comfort: Cold upstairs rooms
After (270mm mineral wool):
- Cost: £1,400 (£1,500 Energy Saving Trust grant covered full cost)
- EPC: D1
- Heating cost: £2,100/year
- Savings: £700/year
Payback: Immediate (fully funded by grant)
Case 2: 1990s Detached, Malahide
Before:
- 100mm old insulation
- EPC: D2
- Heating cost: £3,200/year
After (topped up to 300mm + tank insulation):
- Cost: £900 (after £1,500 grant)
- EPC: C3
- Heating cost: £2,700/year
- Savings: £500/year
Payback: Under 2 years
✅ Installation Best Practices
Do’s:
- ✓ Ensure minimum 270mm thickness
- ✓ Cover ALL areas including edges
- ✓ Insulate around (not over) recessed lights
- ✓ Insulate attic hatch
- ✓ Insulate pipes and water tanks in cold attic
- ✓ Maintain ventilation gaps at eaves
- ✓ Use vapour barrier on warm side if needed
Don’ts:
- ❌ Block soffit ventilation
- ❌ Cover electrical cables unsafely
- ❌ Compress insulation (reduces effectiveness)
- ❌ Leave gaps or thin spots
- ❌ Forget the attic hatch (major heat loss point)
🏗️ DIY vs Professional Installation
DIY Possible For:
- Topping up existing attic insulation
- Mineral wool roll installation in accessible attics
- Attic hatch insulation
Cost saving: 30-50%
Professional Required For:
- Rafter/warm roof insulation
- Spray foam application
- Flat roof insulation
- Energy Saving Trust grant compliance
- Hard-to-access areas
📅 Best Time to Insulate
| Season | Pros | Cons |
|---|---|---|
| Spring | Before summer heat | Busy period for contractors |
| Summer | Pleasant working conditions | Attic very hot |
| Autumn | Before winter bills hit | Some grant rush |
| Winter | See immediate savings | Cold installation conditions |
Best approach: Apply for grants in spring, install in autumn before heating season.
🔗 Combine With Other Upgrades for Maximum Savings
| Additional Upgrade | Extra Savings | Energy Saving Trust Grant |
|---|---|---|
| Wall insulation | £300-£500/year | Up to £8,000 |
| Heat pump | £500-£1,000/year | Up to £6,500 |
| Solar PV | £300-£600/year | Up to £2,400 |
| Triple glazing | £100-£200/year | N/A |
Combined savings: £1,500-£2,500+/year possible!
📞 Start Saving Today
Ready to slash your heating bills?
- ✓ Free energy assessment
- ✓ Energy Saving Trust grant guidance
- ✓ Professional installation
- ✓ Guaranteed workmanship
📞 Call: +44 89 981 9675
Related Resources
- Energy Saving Trust Insulation Grants Guide - Claim up to £3,000
- Roof Replacement Costs - Full pricing guide
- Green Roof Benefits - Eco options
- Roof Inspection Checklist - DIY guide
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