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A suspended ground floor is one of the leading causes of heat loss within older homes. But there is a way to prevent energy loss and keep out the cold. 

Suspended floor insulation can help to ensure a room retains heat and is energy efficient. Read on to find out all about our applications - and everything else you need to know.

Why do we need suspended floor insulation?

A typical raised floor in most older buildings is made of timber, where more modern buildings would have a concrete floor design. With the floor raised above the ground surface, the crawl space left below often causes more energy loss than a modern building. 

Suspended floor insulation is the answer. Installed in between the wooden beams or against the underside of a concrete floor over a crawlspace, it can reduce heat loss to almost zero and increase energy efficiency through innovative use of sustainable materials.


  • Keeps out cold air and prevents warm air escaping
  • Increases the energy efficiency of older buildings
  • Reduces your carbon footprint

Calculator and savings

Costs and savings will vary depending on desired performance level. High thermal performance will cost more but the financial benefits over time will always outweigh the initial extra costs.

The main driver for installing suspended timber floor insulation will be to improve thermal performance. 

To plan what thickness of insulation you’ll need for a suspended timber floor you must calculate its U-Value. In England and Wales building regulations suggest the floor should achieve a U-Value of 0.25 W/m2K or less, if possible. To define this, you’ll also need to work out the perimeter / area ratio. Better known as the P/A ratio, it’s the amount of the exposed perimeter divided by the floor area.

The higher the P/A ratio, the more insulation you’ll need. Our U-Value calculator will recommend the most suitable thickness of insulation for your project. Plus, it can be integrated into BIM, so you can centralise all material and design updates.




Ground Floor - Suspended Beam & Block - THERMAL ROCKFLOOR
Adding stone wool insulation in a timber ground floor increases the comfort level immediately. No more cold feet during the wintertime.

Roger Peeters

ROCKWOOL Group Product Manager
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17.2 MB


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FLEXI Datasheet

To be updated
1.2 MB

Thermal ROCKFLOOR Datasheet

Financial support

Check the Energy Savings Trust website to see whether there are any financial support schemes available for suspended floor insulation.

Energy Efficiency, Key, Keyboard, Button



How do you insulate under a suspended timber floor?

Using insulation boards and a specialist cutting tool, you should be able to fit insulation between timber joists. You can consult a professional or do the job yourself.

How much heat is lost through the floor?

An uninsulated ground floor can easily add up to 30 percent of the heat loss of a building – especially when the crawlspace is heavily ventilated.

Why do you call a ground floor suspended?

When the ground floor has a crawl space underneath the floor, beams or concrete slabs are suspended from wall to wall.