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Your A-Z Insulation Product Guide

Updated: Sep 6, 2023


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Rolls of insulation

It’s during this time of year that many of us become a lot more aware of just how sub-standard New Zealand housing is when it comes to insulation.

Do you find yourself coming home and taking off all your wintry layers, only to realise that the temperature inside really isn’t that much different? Or, how about when you’re lying in bed at night, and all you can hear is the sound of the wind whistling through the windows and doors?

If this sounds all too familiar and you’ve been considering replacing the insulation in your home, then this blog is for you! We wrote this to give you some guidance on the products that are available and to help you decide which may be best suited for your needs.


But, before we give you the options, we would be amiss if we didn’t provide a brief overview of R-values. “What are R-values”, you ask. Glad to be of assistance. R-values are the measure of a material’s ability to resist the transfer of heat. Basically, the higher the R-value, the better the insulation (and usually the more expensive!). This also means it will be easier to heat (and maintain that heat) in the colder months. Insulation works both ways – to keep heat in during winter and by keeping the hot air out during summer.

R-value requirements change depending on where you live. In the far North, the minimal R-value is lower than in the Central Plateau or the South Island. Our advice is this: as much as your budget will allow, try to invest in insulation that exceeds the minimum requirement for your area. You will never be sorry for going over rather than under R-value requirements.

Okay, so here in alphabetical order, are the insulation products. (Spot the environmentally friendly products by this sign:

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Blown-in Fibreglass

Unlike fibreglass batts, blown-in insulation is a loose product without any seams. This means it can be a lot more efficient than standard fibreglass batts. Some studies have shown that this type of insulation performs 22% better than batts that have the same R-value. Blown-in insulation is also very easy to install. You may want to bear in mind though, that the Energy Efficiency and Conservation Authority (EECA) do not include any blown products on its “approved products” list.

Brands: JJet Stream Max, Supafil Frame, Snug & Sound, CosyWall

Use: Internal and external walls, ceilings, mid floor and roof

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Expanded Polystyrene (EPS)

Made from fire-retardant expanded polystyrene, EPS is a great insulator due to the fact that it is made up of lots of polystyrene beads with tiny air pockets. EPS is exceptionally strong, despite how lightweight this product is.

Expanded polystyrene is decay, moisture and pest resistant and does not sag or slump over time. It also provides extremely good fire protection as there is no room for oxygen in the walls. It has very high R Values.

This product is listed as being environmentally friendly because Expol has recycling centres nationwide for its product. You can find a list of facilities that recycle EPS here:

Brands: Expol

Uses: Underfloor, walls

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Extruded Polystyrene

This product is a lightweight, colourless and transparent thermoplastic (a synthetic polymer made from benzene and ethylene). The difference between this and EPS is that extruded polystyrene has a closed-cell structure. This means it is usually stronger and more expensive than EPS. It also means that it is completely unaffected by moisture. This rigid foam board is very versatile in its uses and is easy to install.

Brands: ClimaFoam (Knauf), Expol-X, Composite

Uses: Cavity walls, external walls, roofing, underfloor

Fibreglass Batts

Fibreglass batts have been on the market for over 50 years and are one of the most widely used types of insulation in New Zealand for good reason. Made from recycled glass and sand, it is highly effective and sustainable. It is also non-toxic, non-combustible and resistant to vermin. When installing Pink Batts, you need to wear protective clothing (but it's not so necessary when installing Knauf as it's a safer product to handle).

Brands: Knauf Earthwool, Pink Batts and Bradford (among others)

Use: Wall and ceiling (some products can be used underfloor)

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Although still pretty new to the New Zealand market, hemp is gaining popularity as another insulation option with its' excellent thermal and sound insulating qualities. The fact that it is also fully sustainable, naturally non-toxic, carbon negative, rot, pest and fire resistant in addition to being strong, breathable and lightweight - contributes very much to the reason that this natural product is becoming highly sought after.

Because of its relatively short history in New Zealand, it can be somewhat difficult to source and is a little more expensive than fibreglass insulation.

Use: Walls, ceiling (can be used underground also, for brand new builds)

Mineral Wool

Mineral wool insulation is also known as rock wool. This product is made from stone and industrial waste. In terms of sustainability, it’s a good option because most products are made up of 75% post-industrial recycled content. However, some of these products contain formaldehyde hence the reason we haven’t included the green “environmentally friendly” logo here. Mineral wool is moisture and rot-resistant and is also non-combustible.

Brands: Rockwool and James Hardie (Mineral Insulation)

Use: Wall, ceiling, roof, floors


This is another lightweight board that is easy to cut and install. It is a closed cellular thermoset plastic made up of two chemicals – isocyanurate and polyol. Compared to other insulation products, the energy-conserving qualities of this product are far superior. This means that it has excellent thermal performance. It is also extremely fire-resistant.

Brands: Ardex, Eurothane GP board, X-tratherm, Composite

Uses: Roofing, walls, floors

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One of the most sustainable and environmentally friendly products out there, wool “breathes” by actively absorbing and then releasing moisture as a vapour. It is 100% natural, biodegradable, recyclable and non-toxic. Wool does not produce toxic fumes like some other insulation products and is naturally resistant to mould, making it the best option for allergy sufferers. Not only does wool act as a thermal barrier but also provides excellent sound absorption qualities due to its' natural fibre structure. Wool is manufactured using either low-grade virgin wool or recycled wool from NZ carpet and textile manufacturers.

Wool has the ability to moderate the humidity inside your home. This means that when temperatures drop outside and the amount of moisture in the air rises, wool absorbs this increase. It also acts as a natural filter, absorbing indoor air pollutants and thereby providing clean air for the inhabitants. Last but not least, wool is fire-retardant.

Brands: Terra Lana, EcoFleece, GreenSheep, Havelock Wool, EnviroWool

Use: Ceiling, underfloor, walls

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Spray Polyurethane Foam

22% of this product consists of recycled plastic bottles and renewable content. Because of this and its' low energy production and zero lifecycle, spray polyurethane foam has a very low carbon footprint. Also due to its ability to improve energy efficiency, this product is widely promoted as a green building material.

Spray polyurethane foam virtually eliminates any air leakage, ensuring complete airtightness in a space.

Due to its performance being so optimal, it’s not a wonder that this product can be a little pricier than others.

Brands: NZ Foam, Endurathane, HighGrade Coatings, NZAS

Uses: Roofing, walls, floors, attics

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Straw Bales

Straw bales are certainly not new when it comes to insulation and are becoming more popular in New Zealand. There is currently no NZ standard for straw bale constructions, so if you're looking to build with straw bales, you would need to enlist the guidance of professionals who have used this product in construction and can demonstrate your home’s compliance with the necessary Building Code clauses.

It is, however, one of the most environmentally friendly and sustainable products around, so we thought we would include it in this list.

Straw bales are used for new builds only. Dry bales are stacked tightly like Lego blocks on a concrete foundation and are then wired to keep them together. These blocks are then plastered with breathable plaster to prevent moisture build-up and rot. They have excellent thermal and acoustic properties. Bear in mind though, that if left exposed to the weather before being plastered over, the straw will rot very quickly.

The upfront costs of using straw bales are a lot higher than standard insulation, but they end up saving a lot in terms of energy in the long run.

Use: Walls (new builds only)

Well, there you are! Insulation products in a nutshell. If this insulation guide has prompted questions or you would like to discuss your renovation project with Wellington builders, please don’t hesitate to Contact Us.

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