Flat Roof Insulation in UK Homes Explained!


Table of Contents

Living under a flat roof in the UK can be testing. No doubt, it offers unique space, but it also presents thermal challenges. So winter chills seep in and summer heat gets trapped, leaving you trembling or burning up. But don’t panic we’ve got a solution.

Flat roof insulation is perfect for homes that don’t have a loft or roof space. It boosts the energy efficiency of a household. Now any roof with a pitch of less than 10 degrees is said to have a flat roof. It is highly beneficial in reducing heat loss, minimizing condensation, and lowering heating costs.  Moreover, there are two ways to install insulation on a flat roof. These are warm roof and cold roof insulation. And the choice is yours. Without a doubt, flat roof insulation is about keeping your space soothing and inviting.

In insulated flat roofs, you place insulating materials between your ceiling and the roof membrane. Why? To stop heat from sneaking out or barging into your property. It’s for keeping warmth in and cold out. Now, what makes flat roofs stand out is their simplicity. They in fact lack the traditional loft space found in pitched roofs. A flat roof is basically horizontal and easier to spot. Its roof lacks the usual loft hatch in the ceiling.

So, when winter knocks, your home stays warm. Simple, effective, and cosy – that’s what flat roof insulation can do for you.

Evolution of Flat Roofs

History Flat roofs have been with us for ages. It has been a trend for over 150 years. From the 1950s to the 1970s, they were all the rage in the UK. So if your property’s old, you might have a split roof sloping in the front with loft access and a flat in the back. This flat part in fact could be a terrace or an inaccessible roof space.

Back in those days, flat roofs weren’t big on insulation. So, if you have one, chances are it’s poorly insulated. Moreover, during winter, warm air must be escaping out of your home. The same is the case with summer which becomes extremely hot. However, even if your roof got a new membrane or asphalt (keeps water out), insulation’s likely a no-go unless you asked for it. So don’t let your flat roof leave you chilly in winter or melting in summer. Ensure insulation.

Why You Should Insulate Your Flat Roof?

Primarily, there are two reasons why you should insulate your flat roof.

Firstly, when there is winter, you’ll want to have your home stay warm and protected. But you cannot ensure warmth merely by trapping heat through wood or waterproofing. Wood and similar substrates often let heat escape. Consequently, the key to retaining warmth and cutting heating bills is an effective insulating material.

Next, the thermal efficiency of your property is critically important. In the face of climate change, thermal efficiency shields your home from environmental factors. What’s more, it helps stop air leakages and tackle thermal bridging through advanced insulating materials.

Well, insulating your flat roof is best done during initial construction. But, if you missed that chance, don’t panic. It’s still doable later unless your flat roof is irreparably damaged. In that case, you’ll need a complete replacement.  Moreover, these days, several renowned brands offer high-performance rigid insulation boards. So you can still get the job done wonderfully.

Now whether you choose to insulate from the inside or outside, you’re in the clear.

Free Inuslation Grants

Get Loft Insulation and Cavity wall Insulation under the Great British Insulation Scheme 

Check your Eligibility Now

Cold Roof Insulation

Next, there is cold roof insulation. For this, you place insulation between the joists but cover it with waterproofing. This may not be at an ideal level of energy-efficiency, but it really is a good choice for retrofits or outbuildings. But remember, cold roofs need ventilation to move away damp. Not the top pick for flat roof insulation, but still, it is useful in specific projects. What’s more, we would recommend loft insulation rolls. These are ideal for placing between rafters in cold roof insulation.

Warm Roof Insulation

Warm roof insulation keeps your home compatible with the weather. It works simply. You just put insulation above the joists and cover it with a vapor barrier. As a result, it stops condensation. Moreover, think of PIR boards that are tough and walkable. Plus these are ideal for UK climate. You can also check your roof through these boards.

How to insulate a flat roof from the Inside

Undeniably, both a cold roof and a warm roof share six common elements. But a cold roof adds a ventilation layer.

Now, we’ll shed light on the steps focusing on the cold roof method:

  1. Waterproofing: Firstly, start with a solid foundation. It is the waterproofing layer.
  2. Timber Deck: Next, ensure toughness with a timber deck.
  3. Timber Joists: Build the support system using timber joists.
  4. Insulation: Now, insulate for that warm feel.
  5. Vapour Control Layer (VCL): Guard against moisture by adding a vapour control layer.
  6. Plasterboard Ceiling: Finish it off with a plasterboard ceiling for a polished look.

Remember, a 50-60mm ventilation zone is key to prevent moisture issues. Without it, your roof might need a complete replacement over time.

The Process

Carefully remove the plasterboard ceiling, ensuring a proper ventilation layer. Install cold flat roof insulation boards between timber joists. Following manufacturer guidelines. Add a VCL under the insulation boards and replace the ceiling.

How to insulate a flat roof from the outside

Want to insulate your flat roof from the outside? In this method, we’ll be focusing on the preferred warm roof method.

  1. Waterproofing: Start with a solid foundation. Place 12mm plywood or OSB board on timber joists.
  2. Insulation: Next, the insulating layer that keeps the warmth in.
  3. Vapour Control Layer (VCL): Guard against condensation by adding a vapour control layer. Mark fixing points through the VCL using rafter centers.
  4. Timber Deck: This brings stability and durability.
  5. Timber Joists: These are support systems for structural integrity.
  6. Plasterboard Ceiling: Now, you can finish it off with a plasterboard ceiling to get a polished look.

Remember, use butyl tape for sealing at penetration points. And, crucially, adapt the insulation thickness based on available space for guttering. Finally, you’re done with locking the heat.

Government Grants for Flat Roof Insulation

Do you know you can get flat roof insulation done through two major schemes of the government? Firstly, there is the ECO4 scheme. It’s all about bringing affordable, energy-efficient heating to homes struggling financially. Its core purpose is to reduce carbon emissions and deal with the challenges posed by climate change. Big energy companies such as (Berks Insulation, Eco Energy Services, Free Boilers Grants) are the authorized names to deal with your case on top priorities.  ECO4 is the latest phase, with specific eligibility criteria. Now, it’s more about income than specific benefits. Insulation grants focus on homes with an Energy Performance Certificate (EPC) in bands D or below D.

Qualifying Benefits

If you or someone in your household claims any of the listed benefits, you’re likely eligible for flat roof insulation.

  •  Income-based Jobseekers Allowance (JSA)
  • Income-related Employment and Support Allowance (ESA)
  • Income Support (IS)
  • Pension Credit Guarantee Credit
  • Working Tax Credit (WTC)
  • Child Tax Credits (CTC)
  • Universal Credit (UC)
  • Housing Benefit (now eligible through ECO4)
  • Pension Credit Savings Credit

Even if you don’t fully qualify, applying is worthwhile. You might still get a subsidized grant to help cover the cost of your new insulation.

Next, there is the Great British Insulation Scheme for flat roof insulation. This scheme aims to uplift the least energy-efficient homes in Great Britain. Further, its mission is to tackle fuel poverty and cut carbon emissions. To qualify, your property must need energy-efficiency upgrades like flat roof insulation. The scheme provides one insulation measure per home, decided through a retrofit assessment. For some low-income households, secondary measures like room thermostats or boiler programmers may also be available. So if your home has an EPC (Energy Performance Certificate) rating of D, E, F, or G, you may be eligible.


Without a doubt, flat roof insulation improves the energy efficiency of your home. It reduces heat loss and cuts carbon. Moreover, the choice between warm and cold roof insulation is yours. Each type has its advantages.  Flat roof insulation stops heat from escaping. Next, you can get flat roof insulation through government schemes like ECO4 and the Great British Insulation Scheme. Both landlords and tenants can apply for these grants. Whether insulating from the outside or inside, the process involves specific steps. It turns your home into a warm and energy-efficient haven. So, embrace the simplicity and effectiveness of flat roof insulation. Finally, enjoy year-round warmth.

Get Your ECO4 Grant

Simply enter your postal code and answer a few questions, we’ll handle the rest!

Recent Blogs

Share Blog

You May Also Like