To Insulate or to not insulate your foundation

Why Insulated Slabs Are Worth Considering for Your Next Build

If you’re planning a new residential or commercial build, one of the most important and often overlooked decisions happens below your feet. We’re talking about insulated concrete slabs. Products like QuickEdge and Expol underslab insulation are gaining traction in the industry for good reason – they make your slab work harder and smarter.

What is slab insulation?

Slab insulation involves placing insulating materials either under the concrete slab or around its perimeter (or both), to reduce heat loss. QuickEdge, for example, is a high-performance edge insulation system that wraps around the perimeter of your foundation. Expol, on the other hand, is rigid polystyrene sheet insulation laid under the slab to create a thermal break between your heated floor and the ground.

Why it matters

Concrete is a fantastic building material – strong, durable, and great at holding thermal mass. But it’s also a pretty efficient heat conductor, which means if you’re heating your home or building, a lot of that warmth can simply disappear into the ground. That’s where slab insulation comes in. It keeps heat where you want it – inside.

If you’re planning underfloor heating, insulation isn’t just a nice-to-have – it’s essential. Without it, you’re basically heating the earth beneath your building. Underslab insulation acts as a thermal barrier, helping your heating system run more efficiently and reducing energy costs over time.

The pros and cons

Like any building choice, insulated slabs come with their own set of pros and cons.

Pros:

• Improved energy efficiency – better thermal performance means lower heating bills
• More comfortable living and working environments
• Ideal for use with heated slabs
• Helps meet or exceed NZ Building Code insulation requirements
• Can be retrofitted in some cases for commercial refurbishments

Cons:

• Slightly higher upfront cost – insulation adds to material and labour costs
• Installation must be precise – especially around the slab edge, to ensure proper performance

But as we always tell our clients: the additional upfront cost is an investment in long-term comfort and efficiency. And when you’re building with heating in mind, slab insulation is not something you want to cut corners on.

How we can help

At Rapid Slabs & Precast, we’ve laid down thousands of square metres of concrete and we’ve seen firsthand the difference insulated slabs can make, especially in colder regions and heated flooring builds. We work with systems like QuickEdge and Expol and can offer practical advice on the best approach for your project.

Whether you’re building a residential home, a commercial space, or a mixed-use development, we’ll help you design and deliver a foundation that suits your build – and your future energy bills.

Need a quote or want to know more about insulated slabs? Let’s chat. Our team is here to make the concrete part of your project the easiest decision you’ll make.