Install Internal Walls

How to install insulation ?

Why use foil insulation on internal walls?

Internal wall insulation with reflective foil adds a thin thermal layer to the inside face of a wall, helping rooms stay more comfortable without a bulky build-up. It suits rooms where you want better thermal comfort and cannot add thick insulation or work on the outside of the building. The photos above show Alumix foil being fitted to internal walls.

How internal wall foil insulation works

Reflective foil reflects radiant heat and, with its core layers, adds a thermal break and moisture-resistant layer. Fixed to the wall framing with the right air gap and sealed seams, it helps limit heat transfer through the wall and can reduce condensation on cold wall surfaces.

Step-by-step: installing foil insulation on internal walls

1. Measure the wall and work out the number of rolls, allowing for overlaps at the seams.
2. Make sure the wall or framing is clean, dry and free of sharp fixings.
3. Cut the insulation to height, leaving a small allowance at top and bottom.
4. Fix the sheet to the framing with the reflective face toward the heat source, keeping it flat and taut.
5. Overlap adjacent sheets and seal all joints with foil tape.
6. Seal around sockets, pipes and openings so the layer stays continuous.
7. Add battens or a lining board over the foil to finish the wall.

Recommended Alumix product

For internal walls we recommend Multi+ 10mm Fire Rated Multi-Layer IXPE Reflective Insulation. Visit the product page for details, or contact the Alumix team for advice on your project.

Tips for best results

• Tape all seams. A continuous layer works better than one with gaps.
• Keep electrics clear. Leave the required clearance around cables and fittings.
• Allow an air gap. Foil faces perform best next to an air space.
• Check local building rules. Follow the requirements that apply to your building.

Frequently asked questions

Can I insulate internal walls with reflective foil?

Yes. Reflective foil can be fixed to wall framing and covered with a lining, which makes it a slim option for internal walls.

Which side of the foil faces the room?

Face the reflective side toward the heat source and follow the instructions supplied with your roll.

Do I need to seal the joints?

Yes. Sealing every joint with foil tape keeps the layer continuous and helps manage moisture.

Related installation guides

See how to insulate external walls, treat floors, or explore the full application gallery.