Complete Guide to Spray Foam Insulation Types
Understanding the differences between open cell and closed cell foam, and the specific problems each type causes for UK properties.
What is Spray Foam Insulation?
Spray Polyurethane Foam (SPF) is a chemical product created by mixing two components that react when they come into contact with each other, expanding to create an insulation barrier.
How It's Applied
Sprayed as a liquid that expands and hardens into foam, typically applied to roof spaces, walls, and floors.
Insulation Properties
Provides thermal insulation and air sealing, marketed as highly effective for energy efficiency.
Open Cell vs Closed Cell Foam
Characteristic
Open Cell Foam
Closed Cell Foam
Specific Problems by Foam Type
Open Cell Foam Problems
Moisture Issues
- Absorbs water like a sponge
- Retains moisture against timber
- Creates ideal conditions for rot
- Difficult to dry out once wet
Ventilation Blocking
- Blocks roof ventilation paths
- Prevents natural air circulation
- Increases condensation risk
- Traps humid air in roof space
Inspection Issues
- Hides structural problems
- Makes roof timber inspection impossible
- Conceals electrical and plumbing issues
- Prevents maintenance access
Removal Difficulties
- Adheres strongly to timber
- Often damages roof structure during removal
- Requires specialist equipment
- Labour-intensive removal process
Closed Cell Foam Problems
Complete Vapour Barrier
- Prevents timber from breathing
- Traps moisture on cold side
- Can cause interstitial condensation
- Changes building's moisture dynamics
Maintenance Access
- Extremely difficult to remove
- Blocks access to services
- Makes repairs nearly impossible
- Requires destructive removal methods
Fire Safety Concerns
- Changes fire spread characteristics
- May produce toxic fumes when heated
- Complicates fire safety assessments
- Affects emergency service access
Economic Impact
- Highest removal costs
- Often requires structural repairs
- Greatest impact on property value
- Most lender/insurer resistance
How to Identify Your Foam Type
Open Cell Foam
Visual Characteristics:
- Light yellow/cream colour
- Soft, spongy texture
- Lower density appearance
- More flexible when touched
Simple Tests:
- Compresses under finger pressure
- Absorbs water quickly
- Air can pass through it
Closed Cell Foam
Visual Characteristics:
- Light grey/white colour
- Hard, rigid texture
- Higher density appearance
- Feels solid and inflexible
Simple Tests:
- Does not compress under pressure
- Water beads on surface
- Completely blocks air flow
Professional Identification Recommended
While these visual guides can help, professional identification is recommended for insurance and mortgage purposes. Our experts can provide detailed assessments and documentation.