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EXPOL R1.4 White and EXPOL R1.8 Black UnderFloor Insulation meet and exceed the Residential Tenancies Act requirements.

Trusted by Kiwis for more than 25 years, EXPOL UnderFloor Insulation is easy-to-install and is available in 4 convenient joist widths 360, 410, 470, 560 (mm). It is the DIY solution that will keep your home warm, dry and healthy.

Suitable for use in both new and existing homes, EXPOL UnderFloor Insulation comes with a 50 year product warranty and requires no maintenance.

EXPOL provides EXPOL R1.4 White and EXPOL R1.8 Black UnderFloor Insulation for insulating between the joists under timber floors. EXPOL UnderFloor is specifically designed for both new and existing floors.

Underfloor Insulation
Underfloor Insulation

EXPOL UnderFloor Insulation - R1.4 White Panel installed showing L Brackets to secure panel.

EXPOL UnderFloor Insulation - R1.8 Black Panel installed showing L Brackets to secure panel.

EXPOL R1.4 - 360 White UnderFloor Insulation

EXPOL R1.4 - 410 White UnderFloor Insulation

EXPOL R1.4 - 470 White UnderFloor Insulation

EXPOL R1.4 - 560 White UnderFloor Insulation

EXPOL R1.8 - 360, 410. 470 & 560 Black UnderFloor Insulation

Underfloor Insulation

Download Technical Data Sheet

EXPOL R1.4 White UnderFloor Insulation contains recycled content and can be recycled.
EXPOL R1.8 Black can be easily recycled.

The Products

EXPOL Premium Timber UnderFloor Insulation solutions are made from a fire retardant Expanded Polystyrene. In most situations floor insulation is exposed to the elements (as opposed to wall and ceiling insulation in a cavity) and so it is vital that the materials used will stand the test of time. EXPOL’s solid insulation products are not affected by moisture and will not degrade over time.

Both products are 60mm in thickness with concertina cuts on either side for easy installation. All fixing components are supplied by EXPOL and when used according to EXPOL’s installation instructions ( see videos below) will ensure the system lasts the life time of the construction.

EXPOL R1.4 White UnderFloor Insulation is appraised by BRANZ and has a 50 year warranty.

EXPOL R1.4 White UnderFloor Insulation is a rigid white panel manufactured from Expanded Polystyrene material, 1200mm in length manufactured in four standard widths. This proven solution for timber floor insulation has been on the market for over 25 years and contains recycled content.
Visit EXPOL R1.4 White UnderFloor Insulation     


Underfloor Insulation

EXPOL R1.8 Black UnderFloor Insulation is graphite infused Expanded Polystyrene supplied in the same sizes as the standard white Underfloor insulation. EXPOL BLACK is a premium product which achieves superior R values.

Product could be damaged and warranty will be void.

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Underfloor Pack


What is the difference between EXPOL R1.4 White UnderFloor Insulation and EXPOL R1.8 Black UnderFloor Insulation?

EXPOL R1.4 White UnderFloor Insulation and EXPOL R1.8 Black UnderFloor Insulation deliver R Values that meet and exceed building regulations.

EXPOL R1.4 White UnderFloor Insulation is the ideal solution for normal New Zealand suburban environments or rural areas which do not have extreme temperatures. EXPOL R1.4 White UnderFloor Insulation is BRANZ-appraised and has a 50-year product warranty. EXPOL R1.4 White UnderFloor Insulation has 25% recycled content and can be recycled. It is manufactured with consideration for the environment

EXPOL R1.8 Black UnderFloor Insulation incorporates graphite in the manufacturing process and is 35% more efficient than EXPOL R1.4 White UnderFloor Insulation. EXPOL R1.8 Black UnderFloor Insulation is ideal for extremely cold, windy and extreme environments. EXPOL R1.8 Black UnderFloor Insulation has a 50 year product warranty and can be recycled.

What is R Value?

An R-Value is a rating which measures how well insulation can resist heat flow. ‘R’ stands for thermal resistance.

  • R-Value level depends on a number of things such as the type
    of material, its density and thickness.
  • Higher R-Value = Better insulation.

What sizes is EXPOL UnderFloor Insulation supplied in?

EXPOL UnderFloor Insulation is available in 360mm, 410mm, 470mm & 560mm panel widths and are 1200mm long and 60mm thick.

Where do you get EXPOL UnderFloor Insulation from?

EXPOL UnderFloor is available from Mitre 10, Bunnings, Carters, PlaceMakers, ITM, BuildLink, Timber World and other independent hardware and building supply stores nationwide.

How do I cut EXPOL UnderFloor Insulation?

Use a heavy duty utility knife with a slide out blade.

What if my joist widths differ from EXPOL UnderFloors insulations standard size panels?

EXPOL UnderFloor insulation panels have flexi-cut edges which allow the panels to compress 1mm to 2mm to fit varying floor joist spacings. If the panel it to wide for your joist width simply trim it to size. If the panel is not wide enough then simply cut a section out of another panel and insert it to make the combined panels fit the joist cavity.

What fixings do I use under an existing floor?

You use EXPOL L Brackets –  simply put up against the bottom of the panel and nail to the side of the joist. you should use 2 brackets per panel positioned diagonally at the end of the panels.

What fixings do I use when laying down a new floor?

You use EXPOL Joist Saddle Brackets which are designed to fit over the joist before you put the floor down. Use two brackets per panel positioned diagonally 100mm in from the end of the panel. The top of the brakets will fit flush with the top of the joist. Then simply place the panel in the floor cavity and lay the flooring.

Do I need to remove the foil between the joist before installing the underfloor panel?

Yes you do need to remove the existing foil between the joists before installing underfloor panels.

Do I need to leave an air gap between the panel and the floor?

No the panel gets installed hard up against the floor as per Insulation Installation 4246 standards.

Is EXPOL UnderFloor Insulation affected by moisture?

No, even in a extremely damp environment Expol performs well and will not let moisture through to the floor.

Does EXPOL UnderFloor Insulation have a product warranty?

Yes when installed to specifications it has a 50 year product warranty.

What are the benefits of EXPOL UnderFloor Insulation compared to soft installation?

EXPOL UnderFloor Insulation is rigid and will not sag, it does not absorb water and easy to install.

Does EXPOL polystyrene panel effect the plastic casing around electrical wiring?

Yes the plasticiser in the electrical wiring reacts with the polystyrene, use EXPOL WireGuard to create a barrier between the polystyrene and the wire casing. One metre of WireGuard is included in each pack of panels.

Should wiring touch the EXPOL polystyrene panel?

No, there should always be a barrier between the wiring and the insulation.

Do I have to use WireGuard?

No, you can use anything that will create a barrier between the two such as duct tape, insulation tape etc. However we do recommend using EXPOL WireGuard.

Why does there need to be a barrier?

Because in the wiring there is a chemical called plasticiser which reacts with the polystyrene.

If wiring touches polystyrene is there a fire issue?

NO !!!! Absolutely not there has never ever been an issue with this causing a fire.

What happens to wiring if it touches polystyrene?

Nothing much at all other than where the two have touch the wiring may feel a bit sticky.

What shall I do when fitting EXPOL UnderFloor Insulation around plumbing?

Leave 100mm serviceable gap around all plumbing.

What happens to EXPOL UnderFloor Insulation in a fire?

EXPOL UnderFloor insulation is is manufactured with flame retardant and will not support a fire.

Does EXPOL UnderFloor Insulation give off any toxic fumes?

EXPOL UnderFloor insulation is flame retardant and will not support a fire.

Is EXPOL UnderFloor Insulation Rodent proof?

Expol UnderFloor Insulation does not offer any nutritive value to rodents but is not rodent proof.

System Components

EXPOL Wireguard

EXPOL WireGuard

EXPOL WireGuard is a waxed paper strip used to separate exposed electrical cables from EXPOL insulation. Expanded Polystyrene in some cases reacts with the plasticiser and degrades the elastic properties of some electrical cables over a prolonged period.

(See video above)


There are two types of fixings specific to existing floors and new floors. They are made from non-corrosive nylon and are used to fix the EXPOL panels in place.

  • Existing Floors: EXPOL L Brackets are designed to fit under the panel (supplied with stainless steel nails).
  • New Floors: EXPOL Joist Saddles are designed to slip over the joist to support and secure the panel.

(See video above)

Sabre Fix Construction Adhesive

Sabre Fix is an advanced single component polyurethane-based construction adhesive. This powerful adhesive is developed especially for the construction industry and will bond most types of construction materials including timber (damp and dry), concrete, plasterboard, polystyrene and many other porous and non-porous substrates.

For further installation guidelines: Refer to NZS 4246:2016 Energy efficiency – Installing insulation in residential buildings

EXPOL R1.4 White UnderFloor Insulation is BRANZ Appraised.



For all specifying information, relevant product testing and other detailed information please refer to MasterSpec documents on or contact EXPOL for an electronic copy.


EXPOL R1.4 UnderFloor has a BRANZ appraisal.
See BRANZ certificate number 256.


All EXPOL timber floor insulation solutions comply with the Australian and New Zealand Standard AS/NZS 4859.1:2002.


All panels have a yellow stripe down one edge to confirm compliance with manufacturing standard AS 1366 Part 3 1992 for SL grade.

For further, detailed information on all products contact EXPOL 0800 86 33 73


Underfloor Pack


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