What to know: is polystyrene a good insulator?
Written by
23 April 2024
•
4 min read
Insulation makes our homes warm and healthy, but up to 10 per cent of heat is lost through a building’s concrete slab – so it’s important to get it right.
Focused on providing New Zealand with innovative products designed to meet current building standards, Expol manufactures and distributes the country’s largest range of solid insulation and lightweight polystyrene construction solutions.
Following the recent changes to the building code for underfloor insulation, we spoke with Expol’s commercial sales manager, Wayne Watson, to learn what these changes mean and how they affect builders, architects and homeowners.
How has the building code changed?
Aiming to create warmer, drier and more energy-efficient homes for New Zealanders, the latest changes to the H1 code for insulation have seen an increase in R-values and the introduction of six climate zones for the country.
A measurement of thermal resistance, R-values measure how well a material stops heat passing through it. The higher the R-value, the better the material stops the heat flow – meaning a higher R-value represents better insulation performance.
With the Building Code now dividing the country into six climate zones, the level of insulation needed for a building depends on the zone – ranging from warmer to cooler climates. The cooler the zone’s climate, the greater the R-value required for insulation.
Although there is a set of values to achieve, there is no one set method of achieving that.
What R-value do you need?
In response to these changes, Expol has developed foundation solutions for concrete slabs in both slab-on-grade and pod floors/waffle pod floors.
“We’ve done some thermal engineering based on using pods, sheets and edge insulation for concrete foundations and also just for slab-on-grade using sheets and slab insulation,” says Watson.
However, determining this ratio varies greatly.
“Every foundation is a little bit different. Although there is a set of values to achieve, there is no one set method for achieving that. So, every floor might be a bit different in the amount of insulation needed.”
Finding the right R-value for your project
Making it easy for professionals to determine the right R-values for their projects, Expol has developed a set of tables that show the different area-to-perimeter ratios, the different R-values that can be achieved with those ratios, and what the result will be when adding or taking away different products.
“It gives the architect the ability to decide how far they want to take it,” says Watson. “They might simply want to meet the code, while others want to go with the best option available to give it the most insulation.
“These tables are really helpful for architects; it’s an excellent go-to for concrete foundations.”
An online calculator has also been included to help construction professionals determine the area-to-perimeter ratio – a key value for determining the required R-value.
“For example, the first table is what we call the Slab-On-Grade (3604) Table. It has several options. The first is Expol’s SLABX200 in 50mm and 85mm under the entire slab. After this, there’s 50mm, 75mm, 100mm and 120mm of our SLABX200 product plus our edging insulation. This gives you different ratios, down to five, and different R-values achieved by using any one of those solutions on that table,” says Watson.
“The Waffle Pod Raft Slab Table is a little more extensive – mainly because most floors are a waffle pod design now.”
These tables are really helpful for architects; it’s an excellent go-to for concrete foundations.
Working with products and systems developed for these changes
Proving thermal insulation and strength, Expol’s range of concrete floor edge insulation products provides warm, dry and healthy indoor occupants – at the same time, reducing heating and cooling costs.
All covered under Expol’s tables explaining which product combinations are needed to meet the H1 requirements, the MAXEdge, ThermaSlab Edge and SLABX200 are all designed to help achieve the R-value requirement of your next project.
The MAXEdge system is designed for in-situ applications and ThermaSlab Edge is for retrofit applications.
“These new product solutions offer builders an easy way to add insulation to the framework before the concrete pour, or to attach insulation to the slab afterwards.”
SLABX200 has also been developed for under-slab insulation. This product is an evolution of XPS and is locally manufactured. A high-quality product, it delivers high R-values, impressive compressive strength and confidence in supply.