Insulating roof boarding from the inside can significantly improve the energy efficiency of your home, keeping it warmer in the winter and cooler in the summer. In this guide, we’ll explain the key steps and considerations for insulating roof boarding effectively to ensure optimal thermal performance and long-term protection.

Why insulate roof boarding?

Proper roof insulation is essential for reducing energy consumption, improving comfort, and protecting the building from moisture damage. Without adequate insulation, heat can escape through the roof, causing higher energy bills and placing extra strain on your heating system. Internal insulation of roof boarding is a great solution for existing buildings where external insulation might not be feasible or desirable.

Step-by-step guide to insulating roof boarding from the inside

1. Choose the right insulation material

When insulating roof boarding, it’s important to select a material that offers both thermal resistance and moisture control. Common materials include mineral wool, PIR (polyisocyanurate) boards, and natural insulation products such as wood fibre. Each material has its advantages, but for internal roof insulation, it’s crucial to choose one that provides good thermal efficiency and is suitable for your building’s specific requirements.

2. Install a vapour control layer

To prevent moisture from accumulating within the insulation, it’s essential to install a vapour control membrane. This membrane is positioned on the warm side of the insulation to prevent warm, humid air from penetrating the insulation layer and causing condensation. If condensation occurs, it can lead to mould growth, timber rot, and a reduction in the insulation’s effectiveness. Ensure the vapour barrier is installed with an airtight seal by using the appropriate sealing tape, such as VAST-R® or TAFTEX® tape.

3. Apply the insulation

Once the vapour barrier is securely in place, the insulation material can be applied. Measure and cut the insulation to fit snugly between the rafters or joists. Avoid leaving any gaps, as these can cause thermal bridging, where heat escapes through the uninsulated parts of the roof. Ensure the insulation is pressed firmly into place but not compressed, as this can reduce its thermal efficiency.

4. Create an airtight seal

For maximum effectiveness, an airtight seal is crucial. Any gaps between the insulation and roof structure should be sealed using an appropriate tape or sealant. Overlaps in the insulation or vapour barrier should also be sealed to prevent any airflow. Pay special attention to areas around roof penetrations, such as skylights or chimneys, as these are common points where heat can escape. Use products such as Tyvek® Flexwrap tape to create a flexible, airtight seal around these penetrations.

5. Consider adding a service void

If you plan on installing services such as wiring or plumbing in the roof space, consider creating a service void by installing battens over the vapour barrier. This way, the insulation and vapour barrier will not be damaged when services are installed, and the airtightness of the structure is maintained. The void will allow for easy installation and maintenance of any wiring or pipes without compromising the insulation’s performance.

6. Finishing the installation

Once the insulation is in place, you can finish the roof with plasterboard, timber cladding, or other preferred materials. Ensure that these finishing materials are securely attached without damaging the vapour barrier or insulation layer. If installing plasterboard, it’s advisable to use screws rather than nails to reduce the risk of penetrating the vapour barrier.

Insulating roof boarding from the inside is an effective way to improve the energy efficiency of your home, reduce energy costs, and create a more comfortable living environment. By choosing the right insulation materials, properly installing a vapour barrier, and ensuring an airtight seal, you can achieve long-term thermal performance and protect your home from moisture damage.

For high-quality vapour control membranes and insulation solutions, MG Bouw offers a wide range of products designed to enhance the performance and durability of your building’s insulation system.