The waterproofing membrane is placed directly on top of the insulation.

Insulation is generally applied directly on top of the steel, concrete or wooden deck, with a vapour check layer often installed below the insulation – towards the deck – to make sure that no moisture can penetrate the construction.

This helps keep out cold air and create a comfortable temperature indoors1.

ROCKWOOL warm roof insulation is made from stone wool and designed to achieve maximum thermal performance. It’s also non-combustible, with exceptional acoustic properties.

Why do we need warm roof insulation?

Warm roof insulation is important because it keeps out the cold air and conserves the heat inside a building. When installed between and above the rafters, it helps to create a warm layer that prevents any air from outside getting in.

As one of the most effective ways to prevent heat loss, it is the most favourable way to insulate flat- and pitched roofs and make the most of the space, both simplifying the design and helping to lower costs2.


Warm roofs are the umbrella generating spaces to live and work.

Kim Brandt

Global Product Manager, ROCKWOOL Group

Calculator and savings

Buildings with warm flat roofs typically use less energy to heat or cool the indoor space, making it a great investment for industrial, domestic and commercial properties. Bills should generally be lower, and the building’s carbon footprint reduced.

When planning your project, the insulation thickness can be set to almost any specification. Warm flat roof insulation is highly effective – and often a key part of the energy saving potential for the entire building envelope. 

Globally, the average installed density of stone wool insulation for warm flat roofing is approximately 100 – 170 Kg/m3 depending on the type of system.

You can use your market’s local U-value calculator to work out the potential energy improvements and savings you could make with your project.


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Case studies

The new Apollo Tyres factory in Hungary was constructed to produce millions of truck and car tyres each year – with high amounts of combustible material on-site.

The challenge

The company wanted to boost fire safety for its employees. Reducing energy costs and the building’s carbon footprint was also a major concern.

The solution

Architects suggested installing 190,000m² of fire class A1 ROCKWOOL insulation into the factory roof to increase its overall fire performance. The insulation also helped to reduce the carbon footprint and improve interior climate conditions inside the factory for the workers7.


Apollo Tyres Factory, Fire-resilience

Sustainability and energy efficiency

All our products are designed to be robust and energy efficient.

Creating functional and sustainable insulation is part of our core values to help improve modern living for the future – and to care for the environment.

ROCKWOOL warm flat roof insulation is part of our aim to help buildings reach global building standards in their local markets, by making them affordable, energy efficient and environmentally friendly.

Our products are created to ensure the towns and cities we build today are sustainable for the future9.

Reference case, Kay Fiskers Plads, REDAir, building site, GBI, facade, office building, construction, reclaim waste, recycling, sustainability

Financial support

Local government grants and subsidies may be available for insulation if your building or household is eligible. Sustainability schemes and refunds may be available through tax reductions or incentive schemes. Contact our local offices for more information.

Energy Efficiency, Key, Keyboard, Button


Do you need to ventilate a warm flat roof?
How do you insulate a warm flat roof?
What is a cold flat roof?