Expol premium UNDERFLOOR R1.8 Black for Timber Floor insulation



Changes to New Zealand's Residential Tenancies Act mean landlords need to ensure all tenanted properties have proper floor and ceiling insulation by mid 2019. Review the changes here.

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 insulation exceeds this with a value of R1.4 and EXPOL Black, used in extreme environments, even 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.

For the warmest home possible, choose EXPOL UnderFloor R1.8 Black for superior underfloor insulation.

Easy to fit under new or existing timber floors it is available in 4 convenient joist widths 560, 470, 410, 360 (mm).  EXPOL UnderFloor R1.8 Black is 30% more efficient than other polystyrene insulation boards.  With added graphite, the black board is your best choice when it comes to an insulation board that will not sag or slump for the life of the building.

Enjoy the health benefits and cost savings that come with a warm, energy-efficient home.

Click to enlarge


Existing Timber Floors

No more drafty floors. Improve the insulation of your home by installing EXPOL UnderFloor R1.8 Black in existing homes.

Ideally suited to polished floors in bungalows, villas and pole houses, with flexi-cut edges that make getting the perfect fit between floor joists easy.

New Timber Floors

Easy to install, polystyrene insulation goes down before the floor is laid and creates a warm, dry home with significantly reduced costs for heating and energy. EXPOL UnderFloor R1.8 Black fits snugly between floor joists and can be used under timber floors in bungalows, villas or pole houses.


EXPOL Underfloor R1.8 Black comes with a 50-year product warranty.  

For an under floor insulation solution that won’t degrade over time, EXPOL UnderFloor R1.8 Black provides water resistance and thermal protection for the life of the building.  The rigid foam construction of expanded polystyrene (EPS) ensures boards do not sag or slump or allow thermal gaps over time.  The product is not affected by moisture and is suitable for use in areas prone to high wind.

The R-value rating of a building relates to how well an insulation material can resist heat flow.  The higher the R-value, the better the performance.   With an R-value of 1.8, EXPOL UnderFloor R1.8 Black is the superior product for underfloor insulation.

EXPOL UnderFloor R1.8 Black is the charcoal EPS board.  With added graphite, EXPOL UnderFloor R1.8 Black delivers superior insulation and absorption properties.

This is the easiest way to ensure an energy efficient home that reflects heat away in summer and retains warmth in winter.


EXPOL makes insulating your floors easy.

To ensure you get the best result, follow these simple steps or watch our 'How to Install EXPOL UnderFloor R1.4' video.

EXPOL UnderFloor R1.8 Black is installed in the exact same manner as EXPOL UnderFloor R1.4 demonstrated in this video.

To assist you we've developed the easy step guide, follow it and you can't go wrong.

Don't forget to pick up your Expol Underfloor Easy Measure Ruler. Use it to measure the underfloor joist sizes, so you can purchase the correct panels for your DIY Insulation project.

Step 1


Place your Easy Measure Ruler or a tape measure against one side of the joist. The opposite joist will fall within one of our four panel sizes. Joist sizes can vary, so be sure to measure more than one. You may need a few different panel sizes to complete the job.

Step 2


If the panel is too wide, simply slice down the appropriate concertina edge, leaving the panel approximately 5mm over sized to ensure a firm fit.


Step 3


Slide the panel between the joists, the concertina designed cuts will ensure a tight fit.The panel should be pushed up hard against the bottom of your floor leaving no air gap.

Step 4


Fixings: Once panel is installed tack two Expol Fixings in opposite corners to ensure Expol Underfloor will stay in place for the lifetime of your home.


Step 5


Electrical: For cables that come into DIRECT contact with Expol Underfloor, place Expol Wireguard around the wires before installation.

Step 6


Pipes & Plumbing: For obstacles such as pipes and plumbing use your sharp knife to cut the panel and notch around the difficult areas.For future maintenance, leave 100mm clearance around pipes and plumbing.



If you'd prefer to have a registered installer fit EXPOL Black insulation, call us on 0800 UNDERFLOOR (86 33 73).




EXPOL Wireguard is a waxed paper strip that separates exposed electrical cables from EXPOL insulation.  An important part of the system, EXPOL Wireguard prevents the degrading effect that EPS can sometimes have on electrical cables over a prolonged period. 



Non-corrosive nylon fixings with a stainless steel nail are used to fix EXPOL insulation panels in place.  Designed to suit both new and existing floor insulation applications.



EXPOL supplies a water-based glue to adhere polystyrene to most surfaces. Under floor insulation panels are glued in place using adhesive or can be used in combination with other fixing methods. 



EXPOL UnderFloor R1.8 Black comes in four widths, designed to suit most standard floor joist spacings. To find out which width is right for your floors, you can use our handy ruler.


Download our handy panel size ruler here

TIP: Joist sizes can vary so be sure to measure more than one. You may need a few different panel sizes to complete the job.


Use the table below or the Pack Calculator to the right to determine how many EXPOL packs you require. You will need to measure the total floor area you wish to insulate.





Technical information




Why is EXPOL UNDERFLOOR R1.8 Black a different colour?

Graphite is added to EXPOL UnderFloor R1.8 Black at the production stage.  This gives it superior insulation and absorption properties.

What happens to EXPOL UNDERFLOOR R1.8 Black in a fire?

EXPOL UnderFloor R1.8 Black is made from fire retardant EPS, so the material will not support a fire.

What if joist sizes differ from EXPOL UNDERFLOOR R1.8 Black insulation standard sizes?

The flexi-cut edges of EXPOL UnderFloor R1.8 Black allow the panels to be adjusted to varying floor joist spacings.

Do I need fixings for a new floor?

Yes.  When fixing from the top of the joist the nylon fixing is placed flush with the top of the joist.  This ensures the panel sits flush with the underside of the floor.  Usually a maximum of two fixings are used per panel.

Does EXPOL UNDERFLOOR R1.8 Black absorb water?

The cellular structure of expanded polystyrene does not allow for water absorption.  Even if the panels become partially wet, they will maintain their insulation properties.

How durable is EXPOL UNDERFLOOR R1.8 Black?

The unique matrix structure of expanded polystyrene (EPS) creates a rigid foam that holds its shape and does not deteriorate with age.  EPS is often used for commercial applications as structural base infill or in floats and marinas.  EPS is unaffected by rodents or termites as it offers no nutritional value to pests.


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

View Expol Distributors in a larger map

Other Expol underfloor insulation products which may be of interest

EXPOL Underfloor R 1.4

Fast Facts
  • EXPOL Black is the easiest and most efficient way to insulate new or existing timber floors.
  • By using less energy to heat your home, you are not only helping yourself, you are also helping the planet.
  • EXPOL Black is unaffected by moisture and does not require maintenance.
  • EPS is product that is 98% trapped air and is a recyclable product.
  • EXPOL Black is easy to install as a DIY product or by a professional.
  • EXPOL’s premium underfloor insulation product, EXPOL Black has an R-value of 1.8.

Underfloor Pack Calculator

Area to be insulated

Number of Packs Required - choose width

R-Value Calculator

  • Branz
  • Testing
  • Masterspec
  • Other
Click here

Enquiry Form

General Enquiry

Tel: +64 (9) 634 3449

Free Phone: 0800 86 33 73


105 Captain Springs Rd., Onehunga, Auckland

Tel: +64 (9) 634 3449

Free Phone: 0800 86 33 73


105 Captain Springs Rd., Onehunga, Auckland

Thank you for visiting Expol. To view the site please upgrade to the latest version of Internet Explorer, Chrome or Firefox.

Links to update your browser:

Internet Explorer - http://windows.microsoft.com/en-NZ/internet-explorer/download-ie

Chrome - https://www.google.com/chrome/browser/features.html

Firefox - https://support.mozilla.org/en-US/kb/update-firefox-latest-version