At Loftfoil, we believe in more than just energy savings—we believe in helping homeowners truly understand the value and function of insulation. Whether you’re living in a Victorian terrace or a 1930s semi, understanding how loft insulation works can help you make informed, lasting decisions for your home.
Let’s explore the science behind it—and why modern multifoil insulation, such as SuperFOIL SF19+ and YBS SuperQuilt, offers a smart, space-saving solution for homes across the UK.
How Heat Escapes: The Basics of Heat Transfer
Heat loss from your loft occurs through three key mechanisms—all governed by the laws of thermodynamics:
1. Conduction
This is when heat moves through solid materials, such as your ceiling, roof timbers, or tiles. Without insulation, this process is rapid and unchecked. Materials with low thermal conductivity—like insulating fibres or reflective foils—slow this heat transfer significantly.
2. Convection
Warm air rises. In an uninsulated loft, it escapes through the roof, taking heat (and money) with it. Insulation disrupts airflow, trapping warm air and reducing these convection currents.
3. Radiation
This is the movement of heat as infrared energy. Your loft radiates heat outwards, especially in winter. Reflective foil insulation works by bouncing that radiant heat back into the home, cutting losses dramatically.
Different Types of Loft Insulation: What You Need to Know
| Type | Material Example | How It Works | Common Thickness |
|---|---|---|---|
| Mineral Wool | Fibreglass, Rockwool | Traps air in fibres to resist conduction and convection | 100–270mm |
| Loose-fill | Cellulose, recycled paper | Fills gaps, slows airflow—ideal for top-ups | Varies |
| Rigid Boards | PIR, phenolic foam | Dense, high-performance; good where space is limited | 50–150mm |
| Multifoil | SuperFOIL SF19+, YBS SuperQuilt | Reflective layers combat all three types of heat transfer | 40–65mm (typical)* |
Thickness depends on the specific product and its application.
How Multifoil Insulation Works: Small Profile, Big Results
Multifoil insulation is specially designed to handle all three forms of heat loss. Products like SuperFOIL SF19+ and YBS SuperQuilt are made from multiple layers of reflective foil and wadding, engineered to maximise performance in a slim, easy-to-fit roll.
How it Works
Reflects radiant heat back into the home, reducing losses through radiation
Traps still air between layers to resist conduction and convection
Thin yet powerful: Offers competitive thermal performance with less thickness than mineral wool or rigid boards
Making Sense of U-values and Thickness
You’ll often see insulation products rated with U-values (measured in W/m²K) alongside their listed thicknesses. The U-value tells you how well a material prevents heat from escaping—a lower U-value means better insulation performance. However, it’s important to remember that simply comparing U-values and thicknesses across different insulation types can be misleading if you don’t consider how each material works and the context in which it’s used.
Let’s break it down:
Traditional mineral wool insulation, when installed at a depth of around 270mm, typically achieves a U-value of approximately 0.15 W/m²K. This level of performance is excellent for meeting or exceeding UK building regulations and is a common benchmark for loft insulation.
Multifoil insulation, on the other hand, achieves impressive results with much less material. With a thickness of just 40–65mm, multifoil can match or closely approach the same U-values as much thicker mineral wool, especially when it’s layered or used in combination with other types of insulation. Its unique construction—multiple layers of reflective foil and wadding—means it not only slows down heat transfer by conduction but also reflects radiant heat, giving it an edge in certain applications.
The key takeaway? Multifoil insulation delivers high performance in a much slimmer profile. This makes it an ideal solution for homes where loft space is limited or where you want to maximise headroom without compromising on energy efficiency. By doing more with less, multifoil insulation offers both practical and thermal advantages, making it a smart choice for modern loft conversions and retrofits.
In Summary: Science Meets Smart Living
Loft insulation works by slowing down conduction, convection, and radiation. And thanks to modern materials like multifoil, you don’t need thick, bulky layers to achieve energy efficiency.
Whether you’re retrofitting an Edwardian attic or planning a loft conversion in a mid-century home, Loftfoil’s multifoil insulation offers a high-performance, space-saving, and breathable solution that delivers comfort and savings all year round.
