askvity

How Do You Fit Internal Wall Insulation?

Published in Home Insulation 4 mins read

Fitting internal wall insulation involves adding an insulating layer to the inside of your exterior walls to improve energy efficiency and reduce heating costs. There are primarily two methods: fitting rigid insulation boards directly to the wall or constructing a stud wall filled with insulation.

Methods of Internal Wall Insulation

Here's a breakdown of the common techniques:

  • Rigid Insulation Boards:

    This method involves adhering rigid insulation boards directly to the existing wall. Common materials include:

    • Expanded Polystyrene (EPS): A cost-effective option.
    • Extruded Polystyrene (XPS): More moisture resistant than EPS.
    • Polyurethane (PUR) / Polyisocyanurate (PIR): Offers excellent thermal performance in a thinner profile.
    • Phenolic Foam: Provides high thermal performance and fire resistance.

    Steps:

    1. Preparation: Ensure the existing wall is clean, dry, and free from loose material. Repair any cracks or damage. Remove skirting boards and any fixtures.
    2. Cutting: Measure and cut the insulation boards to fit the wall sections. Use appropriate cutting tools depending on the material (e.g., a fine-toothed saw for PIR).
    3. Adhesion: Apply adhesive (specified for the insulation material and the wall type) to the back of the boards. Follow the manufacturer's instructions for application quantity and pattern.
    4. Installation: Press the boards firmly against the wall, ensuring a tight fit. Use mechanical fixings (screws or plugs) for added security, especially on uneven walls.
    5. Sealing: Seal all joints between boards with foil tape or appropriate sealant to prevent air leakage.
    6. Finishing: Apply plasterboard over the insulation boards to create a smooth, paintable surface. Skim coat the plasterboard, sand, and paint. Reattach skirting boards.

  • Stud Wall Insulation:

    This involves building a new stud wall frame slightly in front of the existing wall and filling the cavity with insulation.

    Steps:

    1. Frame Construction: Build a timber or metal stud wall frame, typically 50-100mm away from the existing wall. Ensure the frame is securely fixed to the floor, ceiling, and adjacent walls.
    2. Insulation Installation: Fill the cavity between the studs with insulation material. Common options include:
      • Mineral Wool (Fiberglass or Rockwool): A cost-effective and readily available option.
      • Cellulose: Made from recycled paper, offering good thermal and acoustic performance.
      • Sheep's Wool: A natural and sustainable option with good moisture-wicking properties.
      • Spray Foam: Expands to fill gaps and create an airtight seal. Can be open-cell or closed-cell.
    3. Vapor Barrier: Install a vapor barrier (e.g., polyethylene sheet) on the warm side of the insulation (facing the room) to prevent moisture from condensing within the insulation. Overlap seams and seal with tape.
    4. Plasterboard: Fix plasterboard to the stud wall frame to create a smooth surface.
    5. Finishing: Skim coat the plasterboard, sand, and paint. Reattach skirting boards.

Considerations

  • Thickness: Choose an insulation thickness that balances thermal performance with the space lost inside the room.
  • Vapor Control: Proper vapor control is crucial to prevent moisture damage.
  • Building Regulations: Ensure the insulation meets local building regulations for thermal performance.
  • Electrical Wiring: If electrical wiring is present in the wall, have a qualified electrician reroute it safely.
  • Professional Installation: Consider hiring a professional installer for best results and to ensure compliance with building codes.

By following these steps, you can effectively fit internal wall insulation to improve the energy efficiency of your home.

Related Articles