Floor insulation is insulation materials that are installed beneath the floorboards that improve the thermal conductivity of the residential or commercial building. The materials are frequently made up of high-performance, rigid polyisocyanurate (PIR) featuring foil facings on both sides or mineral wool slabs and other forms of insulation depending on the method of installation is applied.

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Kingspan OPTIM-R Flooring System

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100mm Recticel GP Insulation Boards (1200x2400mm)

£36.20 ex VAT

Celotex 100mm PIR Insulation Board – GA4100 (2.4m x 1.2m)

£36.20 ex VAT

Celotex 37.5mm Insulated Plasterboard (1200x2400mm) – PL4025

£34.95 ex VAT

ROCKWOOL Flexi – 1200 x 400 x 100mm – (2.88m2)

£719.77 ex VAT

ROCKWOOL Flexi Slab – 1200 x 600 x 100mm – (4.32m2)

£1,000.00 ex VAT

Rockwool RWA45 100mm Acoustic Insulation Slab

£19.61 ex VAT

120mm Celotex Insulation Board – XR4120 (2.4m x 1.2m)

£46.50 ex VAT

25mm Recticel GP Insulation Boards (1200x2400mm)

£14.50 ex VAT

50mm Celotex Insulation Board – GA4050 (2.4m x 1.2m)

£20.69 ex VAT

50mm Recticel GP Insulation Boards (1200x2400mm)

£20.69 ex VAT

70mm Recticel GP Insulation Boards (1200x2400mm)

£29.50 ex VAT

75mm Celotex Insulation Board – GA4075 (2.4m x 1.2m)

£30.96 ex VAT

Celotex 52.5mm Insulated Plasterboard (1200x2400mm) – PL4040

£39.75 ex VAT

Kingspan Kooltherm K103 100mm Insulation Floorboard (2400mm x 1200mm)

£290.40 ex VAT

Kingspan Thermafloor Insulation Board TF70 – 100mm – 2400x1200mm

£49.35 ex VAT

How is floor insulation installed?

There are multiple application methods that can be applied when insulating your floor depending on the type of insulation you need, size, and where in the floor structure it will be fitted. Floor insulation can be applied in suspended floors, solid floors, and concrete floors.

Floor insulation for suspended floors

To find our whether you have a suspended floor you need to evaluate whether there is a space beneath your floorboards and that the floorboards themselves are laying over joists.
Suspended floor insulation is easily installed when there is a basement beneath the property. This gives easy access to the space beneath the joists. The insulation can be placed using insulation netting. Insulation boards and slabs can also be fitted into the joists. Insulation netting can be rolled out and fixed to each joist for extra support. Ensuring the netting is tight and the insulation if butted together and packed tightly the building will achieve better thermal quality.
If your building does not have a basement the floorboard will need to be pulled up. Ensure the room is empty before the work begins as it will be a big job to do. When the boards have been lifted the insulation boards can then be fitted into the joists. The boards need to be measured to the size of each joist space for a tight fit.
You can also use insulation rolls by fitting netting into the joist spaces and then roll the insulation into the spaces and then securing the net to the joist.
Please be aware airbricks can be in outside walls. If airbricks are covered there will be no ventilation and will cause the floorboards to rot. These should be at least two inches below the bottom of the insulation before the hardcore.

Floor insulation for solid floors

Solid floors can be insulated by laying the insulation on top. A damp-proof membrane is recommended to be placed in between the solid floor and insulation board to prevent moisture. Other materials can then be layered on top of the insulation to help with noise such as an acoustic barrier matt followed by underlay.
One thing that’s very important to consider is the floor level. With a minimum of three layers going on top of the existing solid floor, that can impact the height of the internal floor and affect other fixtures and fittings. It may be appropriate to trim doors to size and to employ an electrician to raise electric sockets.


Insulating a concrete floor

Insulation above a concrete floor –
Insulating above a concrete floor can be more practical when working on a renovation project as it can be layered onto the concrete without creating further work and excavating the solid floor.
The layer method is recommended and laying a damp proof membrane inbetween the concrete and the insulation board to prevent moistures. Then layer with moisture-resistant chipboard and then underlay and flooring.
Insulation below a concrete floor –
Infill sands over the surface and then lay damp proof membrane on top of the sand, then lay the insulation boards and then the concrete. Then apply the underlay and chosen flooring.
Why do I need floor insulation? / Further information:
Insulating a floor will prevent heat escaping through the floor where 15% of heat can be lost from a property, this will save money on monthly energy bills. Installing insulation correctly will improve the comfort levels in your residential or commercial property by proving better balance in temperatures and preventing draughts throughout the property.
When installing floor insulation always take the building's fixture and fitting into account as it can increase or decrease the floor depth. This can affect factors such as opening doors, steps throughout the property and can create slopping.
Always consult a building professional when insulating your floors to prevent the wrong insulation from being installed and the possibility of damaging your property.
Building Regulations:
Relevant building regulations will need to be met when applying extra floor insulation. Installers will usually arrange this however it is your responsibility to assure you are complying with regulations.
In England or Wales, the floor should achieve a U-value of 0.25 W/m2K or less, if possible. The U-value is calculated by measuring how quickly heat will travel through the floor. To achieve this standard, at least 70mm of high-performance foam insulation should be applied or 150mm of mineral wool roll however this can differ depending on the size and type of floor in the property.

PIR boards –
Insulation boards are manufactured from rigid polyisocyanurate (PIR), a lightweight foam board fixed in between two foil facings manufactured in a sheet. It is a lightweight product to ensure easy cutting, handling, and application. It provides a multi-purpose use including, walls, roofs, and floors. It is a much-liked product when insulating floors.
Insulation slabs –

Slabs are a flexible material the provides multi-purpose use. They are easy to cut, install and handle making them easily fit within joists and timber frames. This is a popular choice when insulating concrete floors. Insulation slabs are available from brands Kingspan, Knauf, and Rockwool.
Expanded Polystyrene (EPS) is manufactured using beads of foam. The beads are exposed to heat, which causes them to swell and bond together creating a closed-cell structure, which creates a steady layer resulting in a continuous level of insulation throughout the whole floor.
Extruded Polystyrene insulation is manufactured using an extrusion process. This produces a closed-cell structure with a flat surface on the top and bottom and prevents water from piercing through the insulation board. The vapor resistance makes it a great product when insulating a concrete floor.