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

When we think of insulation, the first thing that usually comes to mind is the fluffy fibreglass batts that are stuffed into the internal cavities of our homes. Other insulation products – like concrete, foam and reflective insulation – are also commonly utilised in modern buildings.

But as technology evolves and more resources are devoted to improving thermal efficiency and subsequently reducing carbon emissions, mindsets are shifting beyond just interior insulation, and are moving outwards. Exterior insulation – or ‘out’sulation – is fast becoming an established trend in the construction industry, integrating insulation into cladding systems to make buildings even more efficient.

Resene Construction Systems’ XTHERM GOLD insulated plaster façade system is one such solution disrupting the market. ArchiPro spoke to the company’s General Manager, Mike Olds, who details how the system works and why it’s beneficial for any home that prioritises thermal efficiency.

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.

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.

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.

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

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

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.

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.