Spray foam has gained much attention in recent years. It can be a highly effective insulation type, but many homeowners are now facing costly challenges with it, from mortgage complications to expensive removal.
Fibreglass, on the other hand, has stood the test of time and remains the more reliable choice for most homes.
In our spray foam insulation vs fibreglass insulation comparison guide, we’ll break down the pros and cons of spray foam and fibreglass insulation, explain how they differ, and show you which one is the smarter option.
What Is Spray Foam Insulation?
Spray foam insulation is a polyurethane mixture sprayed into lofts, cavities, or under roofs. It expands into a dense foam that seals every gap. Compare this to say, roll insulation alternatives, and you start to understand how spray foam is fundamentally different to other forms of insulation.
Pros of spray foam
- Excellent airtight seal
- High insulating value per inch
- Will cut heating bills if installed properly
Cons of spray foam
- Expensive to install
- Traps moisture, causing damp and timber damage
- Makes roofs unbreathable
- Mortgage lenders often reject properties with spray foam
- Removal is disruptive and costly
Best Uses for spray foam insulation
Spray foam is sometimes used in industrial or agricultural buildings where airtightness is more important than breathability. For UK homes, however, the risks usually outweigh the benefits.
What Is Fibreglass Insulation?
Fibreglass is made of fine glass fibres and is sold in rolls (batts) or as loose-fill. It has been the go-to insulation material for British homes for decades.
Pros of fibreglass insulation
- Affordable and widely available
- Breathable, allowing air circulation and reducing dampness
- Long-lasting with minimal upkeep
- Easy to top up or replace
- Always accepted by lenders and surveyors
Cons of fibreglass insulation
- Needs thicker layers to achieve the same thermal rating as foam
- It can irritate the skin during installation
- Slightly less effective in tight, awkward spaces
Best Uses for fibreglass
Lofts, roofs, and cavity walls in residential properties. Fibreglass is the safer, more reliable choice for homes looking for cost-effective insulation without future complications.
Spray Foam vs Fibreglass: A Direct Comparison
When choosing insulation, it’s easy to get lost in sales pitches and technical jargon. To make things clearer, let’s compare spray foam and fibreglass side by side across the factors that matter most.
This way, you’ll see not only how they perform in theory, but also what that means in practice for your home and its future value.
Installation
Spray foam requires specialist equipment and a trained team. If it’s not applied evenly, gaps can form, or worse, it can block ventilation channels. Once in place, it bonds tightly to rafters and tiles, making its removal destructive unless you find the right spray foam removal companies and vet them accordingly (which is exactly our role at National Spray Foam Removal).
Fibreglass, on the other hand, is simple. Rolls can be laid across a loft floor in an afternoon, while loose-fill can be poured into awkward spaces. It’s quite simple to replace or upgrade as needed.
Cost
Spray foam is one of the most expensive insulation methods available. The high upfront cost can reach several times that of fibreglass. But the hidden cost comes later. If you decide to sell your home, you may need to pay thousands for removal. We cover spray foam removal costs in our handy foam removal cost guide.
Fibreglass is inexpensive, widely sold in DIY stores, and requires minimal maintenance, making it a cost-effective long-term choice.
Energy Efficiency
Spray foam is praised for its thermal performance per inch, but this comes with a catch. If moisture builds up behind the foam, its effectiveness drops, and the underlying structure can be damaged.
Fibreglass, while needing thicker layers, remains consistently effective and safe. Current UK building regulations recommend around 270mm of fibreglass in lofts.
Mortgage and Property Value
This is where spray foam falters most. Many UK lenders won’t approve mortgages with spray foam present, seeing it as a red flag. Surveyors often recommend removal before a sale can proceed.
Fibreglass carries none of these issues. It’s universally accepted and protects your property’s resale value.
Longevity and Maintenance
Over time, spray foam can shrink, crack, or pull away from surfaces, compromising performance. Once problems occur, repairs are extremely difficult.
Fibreglass is far more forgiving. If it compresses or becomes damaged, it can easily be topped up or replaced without major disruption.
Summary Table: Spray Foam vs Fibreglass
| Feature | Spray Foam | Fibreglass |
| Installation | Specialist, complex | Simple DIY or professional |
| Cost | High upfront, high removal | Low upfront, low maintenance |
| Energy Efficiency | High R-value per inch, risky if damp develops | Reliable performance at recommended depth |
| Mortgage Approval | Often refused by lenders | Universally accepted |
| Longevity & Maintenance | Can shrink, difficult to repair | Long-lasting, easy to replace |
| Breathability | Airtight, traps moisture | Breathable, reduces damp risk |
| Moisture Resistance | Can worsen condensation and rot | Allows airflow, resists damp |
| DIY Suitability | No – requires professionals | Yes – suitable for homeowners |
| Health/Safety | Chemicals, fumes during installation | Safe when handled with gloves/mask |
Looking for additional guidance for other insulation types? You can also compare spray foam and rockwool with another of our comparison guides.
Why Spray Foam Removal Is Often Needed
Many homeowners, who once thought spray foam was a modern solution, now face the reality of its downsides. The most common reasons for spray foam removal include:
- Mortgage refusals: Lenders frequently reject homes with spray foam, leaving sales to collapse unless it’s removed.
- Damp and ventilation issues: Airtight foam traps moisture, causing mould, rot, or roof damage.
- Property devaluation: Homes with spray foam often drop in market value until it’s professionally removed.
- Future-proofing: Even if issues haven’t yet appeared, many homeowners choose removal to avoid problems when selling later.
Because spray foam bonds so tightly to roof timbers and tiles, removal requires specialist equipment and trained professionals. Attempting DIY removal usually causes more damage.
Thinking About Spray Foam Removal?
If your property has spray foam insulation, it may already be affecting its value, your ability to sell, or even your peace of mind. The good news is that safe, professional removal is possible.
At National Spray Foam Removal, we work with trusted partners across the UK who can provide competitive, no-obligation quotes.
Fill out our quick form today, and we’ll connect you with experts who can restore your property and protect its future.
And once the spray foam is removed you’ll need to think about what insulation type is best to remove it. Have a read of our guide today for in-depth expert guidance.
