The Best Way To Fit Insulation & Close The Performance Gap

Insulation is one of the most effective ways to improve energy efficiency, boost comfort, and reduce monthly energy bills in both domestic and commercial properties. But even the highest-performing insulation boards can underperform when not installed correctly. In this post, we explore how to professionally fit Kingspan Therma insulation products and close the ‘performance gap’ — a common issue that arises when the in-use performance of a building doesn’t match its intended energy design.

What Is the Performance Gap – And Why Does it Matter?

The performance gap refers to the difference between the designed energy efficiency of a building and what it achieves in real-world conditions. Even in well-designed buildings, improper installation of insulation can lead to thermal bridging, air leaks, and wasted heat energy. For homeowners and professionals alike, this gap results in higher energy bills, increased carbon emissions, and decreased comfort.

Many factors contribute to the performance gap, including poor workmanship, incorrect detailing, wrong thicknesses of insulation, and gaps between boards. Particularly in the UK, where older homes are being retrofitted to meet modern efficiency standards, closing this gap is more important than ever.

Using premium insulation like Kingspan Therma products is a great first step, but real performance comes with attention to detail during fitting. When installed correctly, Kingspan Therma offers excellent thermal performance (low lambda values), slim profiles, and long-term durability.

Whether you're a DIY enthusiast looking to boost your home’s energy rating or a trade professional juggling multiple renovations, understanding these fitting best practices will help you eliminate cold spots and maximise energy savings.

Why Choose Kingspan Therma?

Kingspan Therma is a high-performance polyisocyanurate (PIR) insulation board designed for floors, walls, roofs, and more. It’s known for its low thermal conductivity, easy handling, and moisture resistance. These qualities make it ideal for both new build and retrofit applications across the UK housing stock.

The wide product range — including Kingspan Thermafloor, Thermawall, and Thermaroof — allows for consistent insulation types across different building elements, simplifying specification and procurement for architects and building professionals.

In addition, Kingspan Therma products are lightweight, easy to cut and shape onsite, and come with robust documentation for proper installation — making the product not only high-performing, but highly practical for real-world use too.

Step-by-Step Guide to Fitting Kingspan Therma Insulation

Follow these guidelines carefully to ensure you fit Kingspan Therma insulation boards correctly and close the performance gap effectively.

1. Preparing the Surface

Ensure the surface is clean, dry, and free from loose materials. This will ensure boards adhere properly and sit flush against structural elements.

For walls and floors, you may need to brush or vacuum the surface, and in older properties, you may need to remove deteriorated plaster or render. Pay special attention to uneven surfaces — these can affect board contact and create performance-reducing air gaps.

2. Accurate Measuring & Cutting

Measure each space precisely to ensure tight-fitting boards. Kingspan Therma can be easily cut using a fine-toothed saw or utility knife. For curved or awkward edges, scribe templates to avoid over-trimming and unnecessary waste.

A good rule of thumb is to cut slightly oversized so that the boards are friction-fit into cavities. A tight fit prevents heat loss through convection or air leakage and ensures continuity of insulation.

3. Fixing the Boards in Position

For wall applications, boards can be mechanically fixed or bonded using suitable adhesive. Floor insulation is typically loose-laid, with tongue-and-groove joints sealed using foil tape. Roof insulation may be mechanically fixed or adhered, depending on the structure and weight loading.

Ensure boards are pressed firmly against the substrate, with no gaps or movement. Tape all edges, particularly around penetrations, and seal with recommended jointing materials to create a continuous insulation envelope.

4. Avoiding Thermal Bridging

Thermal bridging occurs when uninsulated or poorly insulated areas transmit heat more rapidly than surrounding insulated areas, creating cold spots. To prevent this, always stagger board joints in a brick-bond pattern. Where services penetrate insulation, use gap fillers and sealant to maintain continuity.

Use thinner Kingspan Therma boards or flexible insulation to wrap around joists, window reveals, and other tricky junctions. This will maintain an uninterrupted layer of thermal protection.

5. Seal and Inspect

After boards are installed, always seal around the perimeter using tape, expanding foam, or compatible sealants to prevent heat loss through leakage points. Pay attention to pipes, ducts, and window frames — even small gaps can compromise the system.

Finally, conduct a detailed visual inspection and check for any visible gaps, loose boards, or bridging. If you’re working on a larger project or need peace of mind, consider a blower door test to identify air leakage points before finishing build-up layers.

Best Practices by Application

Let’s take a brief look at how to use Kingspan Therma insulation in different areas of your property:

Building Element	Recommended Product	Installation Tips
Walls (internal or cavity)	Kingspan Thermawall TW55	Ensure cavity is clean; friction-fit boards and tape joints
Roofs (pitched and flat)	Kingspan Thermaroof TR27 or TR26	Install above deck for warm roof; use correct adhesive or mechanical fixings
Floors (solid or suspended)	Kingspan Thermafloor TF70	Lose-lay tightly; tape tongue-and-groove joints for complete seal

Benefits of Getting it Right

When you install Kingspan Therma products correctly, you unlock a wide range of benefits for yourself or your client:

• Lower energy bills
• Improved indoor comfort
• Reduced carbon emissions
• Better soundproofing
• Increased property value
• Long-lasting performance with minimal maintenance

Plus, installations that are carried out to a high standard help ensure compliance with UK Building Regulations Part L, which governs insulation and energy performance in buildings.

Final Thoughts

Closing the performance gap isn’t just about choosing the best materials — it’s about installing them with care and precision. Kingspan Therma products offer some of the best thermal performance in their class, but it’s the installation process that truly protects your investment and brings the design to life.

Whether you’re a homeowner improving your energy rating, a designer seeking trusted spec products, or a pro builder looking for precision installation advice, Kingspan Therma is your go-to solution. Take the time to install it right and enjoy the full performance you paid for.