If you’re looking to make your home warmer and more energy efficient, insulation is one of the best places to start. But with more than one option on the table, homeowners are often left wondering: Should I insulate the loft or the cavity walls first?
The answer depends on your home’s layout, age, and energy usage. In this blog, we’ll explore both types of insulation, the benefits they bring, and how to decide which to prioritise.
Why Insulation Matters
Before we dive into the comparison, let’s quickly cover why insulation is so important.
Without proper insulation, a huge amount of your home’s heat escapes through the roof and walls. According to the Energy Saving Trust:
- Around 25% of heat is lost through the roof of an uninsulated home.
- Another 35% is lost through the walls.
That’s over half your heat disappearing – taking your hard-earned money with it.
Insulation helps trap warmth inside, keeping your home cosy in winter and cooler in summer. It also means your boiler doesn’t have to work as hard, which can lower your energy bills and carbon footprint.
What Is Loft Insulation?
Loft insulation is typically made from materials like mineral wool, fibreglass, or recycled products. It’s laid in thick rolls across the floor of your loft space, forming a barrier that stops warm air from rising and escaping through the roof.
Benefits of Loft Insulation:
✅ Quick and easy to install – often done in a day
✅ Lasts 40+ years
✅ Cost-effective – typically pays for itself in under 5 years
✅ Lower bills – can save up to £300 a year (depending on property size)
Best For:
Homes with accessible lofts and minimal existing insulation. Particularly older properties built before the 1980s.
What Is Cavity Wall Insulation?
If your home was built after the 1920s, it likely has a cavity wall – two walls with a gap (or cavity) between them. Cavity wall insulation fills this space, usually with foam, polystyrene beads, or mineral wool, preventing heat from leaking out.
Benefits of Cavity Wall Insulation:
✅ Reduces wall heat loss by up to 70%
✅ Invisible after installation – no need to disturb internal walls
✅ Works year-round – prevents both heat loss in winter and overheating in summer
✅ Saves up to £250 a year
Best For:
Homes with cavity walls and no prior insulation. You’ll need a professional survey to confirm suitability.
Loft vs Cavity Wall: Which Should Come First?
Here’s the truth – both types of insulation make a big difference, and ideally, you’d do both. But if you’re working with a budget or want to stagger the upgrades, here’s how to decide where to begin:
1. Check What’s Already Insulated
Start by seeing what insulation your home already has. If your loft has barely 50mm of old insulation, but your walls are insulated, then the loft is the obvious choice – and vice versa.
💡 Top Tip: The recommended loft insulation depth is now 270mm (around 11 inches). If yours is well below that, it’s time to top up!
2. Look at Heat Loss Priorities
The loft loses around 25% of your heat, but walls can lose even more (around 35%). However, heat rises – so insulating the loft can have a more immediate effect on comfort.
If your home feels cold upstairs or heats unevenly, loft insulation might give the quickest comfort boost.
3. Consider the Installation Process
Loft insulation is typically cheaper and quicker to install with minimal disruption. Cavity wall insulation, while still straightforward, usually requires drilling small holes in the external wall – something to consider if you’re planning external redecorating.
4. Think About Access and Property Type
Some homes can’t have cavity wall insulation – for example, if the walls are solid (common in homes built before 1920) or if the cavity is too narrow or has damp issues. In that case, loft insulation may be the only option.
The Ideal Scenario? Do Both
If your home is suitable and your budget allows, insulating both the loft and cavity walls will make the biggest impact on your comfort and energy bills.
Together, they can:
- Reduce your heating costs by hundreds each year
- Lower your home’s carbon emissions
- Improve your EPC rating – helpful if you plan to sell
- Make your home cosier all year round
Grants and Funding May Be Available
The good news? You may not have to pay the full cost yourself.
There are various government-backed schemes and grants available in the UK for home insulation – especially if you receive certain benefits or live in a hard-to-heat home.
At NCS, we can help you check your eligibility and guide you through the funding process.
Final Thoughts
So – loft or cavity wall insulation first? There’s no one-size-fits-all answer, but by looking at what’s already in place and understanding how your home loses heat, you can make a smart decision.
✔️ If your loft insulation is thin or missing, start there.
✔️ If your walls are uninsulated and suitable, cavity wall insulation is a game-changer.
✔️ If possible, do both for maximum comfort and savings.
Want to upgrade your insulation but not sure where to start?
Give our friendly team a call or get in touch online. At NCS, we offer free home surveys, expert advice and help accessing funding. Let’s make your home warmer, greener and more affordable to run!
