If you’re thinking about investing in underfloor heating, it’s important to think about insulating it too. Insulation boards ensure heat stays exactly where it should be: warming your home and not disappearing into the ground beneath you.
Here’s everything you need to know about how they work and why they're essential for an efficient heating system.
What Are Underfloor Heating Insulation Boards?
Underfloor heating insulation boards are rigid panels installed beneath underfloor heating systems. They’re typically made from extruded polystyrene foam (XPS) or expanded polystyrene (EPS) and sit beneath the heating elements to act as a thermal barrier, preventing heat loss and forcing warmth upwards into the room.
How Underfloor Heating Insulation Boards Work
These insulation boards work by reducing heat loss through two main mechanisms: limiting conduction and reflecting heat upwards.
Reducing Conductive Heat Loss
Conduction is what happens when heat flows through solid materials. In a typical underfloor heating system without insulation boards, you lose heat through the concrete beneath the floor. Insulation boards with low thermal conductivity reduce this significantly.
Improving Heat Distribution
Underfloor heating systems work by emitting infrared radiation that warms objects and surfaces in direct contact with the floor. Insulation boards prevent what’s called radiant heat from escaping downwards, instead directing it upwards where it heats your flooring surface and the room above. This means the room can heat up quicker and you’ll get a more consistent temperature throughout the space.
Types of Underfloor Heating Insulation Boards
Several types of insulation boards are available for underfloor heating installations depending on your application and floor type.
XPS Insulation Boards
Extruded polystyrene (XPS) boards offer excellent compressive strength and moisture resistance, making them ideal for areas where the floor supports heavy loads or where dampness could be an issue. XPS boards are particularly popular for solid concrete floors and are available in various thicknesses, typically ranging from 10mm to 100mm.
EPS Insulation Boards
Expanded polystyrene (EPS) boards provide good thermal performance at a more economical price point. Whilst slightly less robust than XPS, EPS boards can be a good choice for residential homes, particularly suspended timber floors and lighter-duty installations.
Routed Insulation Panels
Some insulation boards come pre-routed with channels or grooves designed for underfloor heating pipes. These panels make installation quicker and easier as the pipes fit into the pre-formed channels. Routed panels are available in both XPS and EPS formats and are particularly useful for water underfloor heating systems.
Key Benefits of Using Insulation Boards for Underfloor Heating
Installing insulation boards beneath your underfloor heating system delivers multiple advantages including:
Enhanced Energy Efficiency
The primary benefit is improved energy efficiency. By preventing heat from escaping through the floor, insulation boards ensure your heating system uses less energy to maintain its temperatures. This means lower energy bills and reduced running costs over the system's lifetime.
Faster Warm-Up Times
Insulated systems heat up significantly faster than uninsulated ones. Rather than wasting energy warming the subfloor and ground below, the heat goes straight into warming your room. This means shorter waiting times for comfort and more responsive temperature control.
More Even Heat Distribution
Unlike traditional radiators that create hot spots around tehm, underfloor heating insulation provides consistent warmth across the entire floor surface. This eliminates cold spots and draughts, creating a more comfortable living environment throughout the room.
Reduced Noise Transmission
Many insulation boards also provide acoustic benefits, helping to reduce noise between floors. This can be useful if you live in a flat or multi-storey home.
Moisture Protection
XPS boards in particular offer excellent moisture resistance, providing an additional protective layer against damp rising from below. This helps protect both your heating system and your flooring in the long run.
Long-Term Cost Savings
While insulation boards are an upfront investment, the energy savings they provide typically pay back this cost within a few years. Over the expected lifespan of an underfloor heating system, insulation boards can save thousands of pounds in heating costs.
Installing Underfloor Heating Insulation Boards
Correct installation is essential to achieve the full benefits of insulation boards.
Preparation
Start with a clean, level subfloor free from dirt and dust. Any bumps or hollows should be sorted before laying the boards, as an uneven surface can compromise both insulation performance and heating element installation.
Board Layout
Lay the insulation boards across the entire floor area, working outwards from one corner and ensuring tight joints between boards. Many boards feature tongue-and-groove edges that lock together, creating a continuous insulation layer without gaps.
Sealing Joints
For maximum thermal performance, seal all joints between boards using aluminium tape or a specialist jointing compound. This prevents heat from escaping through gaps and creates an effective vapour barrier where required.
Securing the Boards
Use insulated fixing nails or screws specifically designed for underfloor heating applications. Standard fixings can create thermal bridges that allow heat to bypass the insulation, reducing overall system efficiency.
Installing the Heating System
Once the insulation boards are secured, install your underfloor heating pipes or electric mats according to the manufacturer's specifications. Take care not to damage the insulation layer during this process.
Testing Before Covering
Before laying the final floor finish, conduct thorough testing of the heating system. Check for any leaks in water systems and verify that electric systems are functioning correctly throughout the floor area.
Choosing the Right Thickness
Insulation board thickness depends on several factors including floor construction, room use, and Building Regulations requirements.
For ground floors and rooms above unheated spaces, thicker insulation (typically 50mm to 100mm) provides better thermal performance and helps meet Building Regulations. Upper floors between heated rooms can often use thinner boards (10mm to 25mm), as the primary concern is sound reduction rather than heat loss.
Always check current Building Regulations Part L requirements for your specific application, as minimum insulation standards apply to many installations.
Compatibility with Floor Finishes
Underfloor heating insulation boards work with virtually all floor finishes, including tiles, natural stone, engineered wood, laminate and vinyl. The key is ensuring the complete floor build-up (including insulation, heating elements and floor finish) doesn't exceed your available floor height.
Tile and stone work particularly well with underfloor heating as they conduct heat efficiently. Carpet can also be used, though you'll need to check the tog rating to ensure it doesn't over-insulate and reduce system efficiency.
Do You Need Insulation Boards for Underfloor Heating?
Insulating your underfloor heating system is always advisable because of the energy waste in uninsulated systems and overall higher running costs to reach effective temperatures.
For new installations or major renovations, building regulations will specify what floor insulation is required. Beyond regulatory compliance, the energy savings delivered by proper insulation boards usually justify their cost within a few years.
Conclusion
Underfloor heating insulation boards play a vital role in creating efficient, comfortable heating systems. By preventing heat loss, improving response times and reducing energy consumption, these boards transform underfloor heating from a luxury into a practical, cost-effective solution for UK homes.
For expert guidance on selecting the right insulation boards for your underfloor heating project, our technical team can help you choose products that meet your specific requirements and budget.
