Thermal ‘out’sulation: what it is, and how it boosts a building’s efficiency

29 May 2023

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ArchiPro spoke to Resene Construction Systems General Manager, Mike Olds, who details how this 'out'sulation works and why it’s beneficial for any home that prioritises thermal efficiency.

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AP: What’s the difference between traditional insulation and ‘out’sulation?

Mike Olds: The most common solution to thermal performance is in-wall insulation – but the problem with this traditional method of insulation is that there will always be a significant element of thermal breaks between the insulation material and the structural framing system. Every stick of timber framing is a break in the thermal performance of the wall.

XTHERM has been developed as an external insulation — what we colloquially refer to as ‘out’sulation — effectively wrapping the building in a monolithic thermal envelope.

The XTHERM Gold insulation panels are fitted continuously across the exterior structure over cavity battens. The only breaks in the ‘out’sulation are the obvious ones: windows and doors.

AP: Can you give me an overview of the XTHERM GOLD insulated plaster facade system?

MO: Not many conventional exterior cladding systems offer thermal benefits by themselves. Our XTHERM systems were introduced as a means to improve the thermal performance of exterior claddings.

The world is changing, and the focus is very much on reducing our carbon footprint. If we can aid the built environment with systems that reduce energy consumption and improve the comfort levels for the occupants, we are heading very much in the right direction.

We had for a long time been applying coatings over insulated EPS panels which is fine; however advances in technology with new materials led us towards extruded polystyrene (XPS) and now polyisocyanurate (PIR) insulation panels as they were far harder than traditional expanded polystyrene (EPS) and provided a significant improvement to thermal resistance.

New technology is easy to find – the difficulty starts when you are trying to fit a square post into a round hole. For us this was who makes XPS and PIR locally. XPS had to be imported, so we have done this for a while now. Then Covid-19 hit which added a layer of complexity in terms of getting goods into New Zealand accurately and on time.

The shipping and global lockdown challenges continued and we discovered a local New Zealand PIR manufacturer. This business connection eliminated the long lead time ordering and storage, shipping challenges and best of all it is made right here.

Can you explain the difference between the XTHERM GOLD ultra high-density PIR panels and traditional EPS panels in terms of thermal insulation and hardness?

The XTHERM Gold system incorporates our exclusive 50, 75 or 100mm thick ultra-high density PIR insulation panels, which provide far greater thermal insulation and nearly double the hardness of standard-grade EPS. This results not only in improved thermal qualities but also contributes to increased impact resistance.

As an example of thermal performance, if you applied 50mm XTHERM Gold over a 20mm cavity on timber framing and assumed the inwall insulation was R2.8, this is what it would look like: inwall insulation R2.8 + XTHERM Gold (@50mm thick) R1.265 = R4.06 please note that we have de-rated the thermal performance x .45 to allow for the cavity.

If you increase the thickness of the XTHERM Gold insulation panel the thermal performance improves as well. Ie @75mm R1.925, and 100mm R2.585.

What materials can the XTHERM GOLD system be fixed over?

Timber or steel framing, also direct fix over masonry walls.

What are the advantages of using the XTHERM GOLD system over other thermal insulation systems?

It has fantastic thermal performance, a very high-density board which increases the hardness, and importantly they are made here in New Zealand.

Can you walk me through the benefits of incorporating your full flashing suite, lamina of modified plaster coatings, and fibreglass reinforcement into the system?

We have a complete approach to our systems to provide accuracy and surety of performance for the life of the cladding. We test the entire system and installation – this includes the performance of the flashings, plaster coatings, weathertightness, and thermal performance.

Our systems are BRANZ-appraised and can only be installed by LBP-registered plastering cladding professionals to provide an accurate system installation.

How does the XTHERM GOLD system contribute to the overall sustainability and energy efficiency of a building project?

Choosing the right thermal insulation is one of the most important decisions made towards achieving an energy-efficient and sustainable project. The XTHERM Gold system provides complete thermal ‘out’sulation whilst protecting the structure of your home – and its residents – from the often unpredictable and extreme New Zealand climate.

Once thermal performance is increased, the energy required to heat or cool is significantly less, in turn reducing the reliance on energy generation all year round.

Learn more about Resene Construction Systems and its insulation systems.