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EXPOL R1.4 White Underfloor Insulation is rigid Expanded Polystyrene panel designed to fit between the joists under a timber floor. It is used in normal urban home environments.

It is ideal to use in personal houses or properties which are tenanted. Changes to New Zealand’s Residential Tenancies Act mean landlords need to ensure all tenanted properties have proper floor and ceiling insulation. EXPOL UnderFloor insulation meets and exceeds the requirements of the Act. For an insulation product to provide adequate insulation to a rental property it needs to have a minimum insulation value of R1.3. EXPOL R1.4 White Underfloor Insulation exceeds this with a value of R1.4 and EXPOL Black Insulation, used in extreme environments, has an insulation value of R1.8.

EXPOL UnderFloor insulation products are independently certified by BRANZ – the organisation which is responsible for testing and approving performance of building products in New Zealand.

EXPOL R1.4 - 410 White UnderFloor Insulation

EXPOL R1.4 - 360 White UnderFloor Insulation

EXPOL R1.4 - 470 White UnderFloor Insulation

EXPOL R1.4 - 560 White UnderFloor Insulation

Underfloor Insulation

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

EXPOL UnderFloor R1.4 White Insulation is available in 4 convenient joist widths 360, 410, 470, 560 (mm). Quick and easy to install it is long-lasting insulation that creates a warm, dry home which is healthier to live in and costs less to heat. It can be used on new and existing timber floors and fits snugly between timber floor joists to stop drafts and damp from entering.

EXPOL UnderFloor R1.4 White Insulation is made of rigid polystyrene, so it won’t sag over time. It is also manufactured with flame retardant, is vermin resistant and helps reduce noise from timber floors.

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



The benefits:

  • Easy to install
  • Concertina edges which allow for compression of up to 20 mm to create a tight fit
  • Contains recycled content and can be easily recycled
  • Flame retardant
  • Rigid
  • Resistant to moisture
  • No nutritional value to vermin, birds or animals
  • Ideal for both retro-fit applications and new floors
  • BRANZ Appraised and comes with a 50 year product warranty


EXPOL UnderFloor R1.4  White Insulation 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.

It is used as an insulation solution for:

Underfloor Insulation

   Timber UnderFloor










Underfloor Pack

Panel Sizes

EXPOL White R1.4 Underfloor Insulation

Product Properties

EXPOL Underfloor Insulation


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.

EXPOL Installation Components

EXPOL Wireguard

EXPOL WireGuard

Where EXPOL R1.4 or R1.8  is exposed to electrical cables us EXPOL WireGuard  a waxed paper strip  to separate exposed electrical cables from the EXPOL R1.4 or R1.8 insulation. Expanded Polystyrene in some cases reacts with the plasticiser and degrades the elastic properties of some electrical cables over a prolonged period.


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.

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.



EXPOL Technical Product Guide


EXPOL Underfloor Brochure

Where To Buy EXPOL


EXPOL products are available at a number of leading building products stores. Find your nearest stockist here.

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