External Timber Frame Wall Insulation

SYSTEM OVERVIEW – Timber Frame External

Application Type:
External insulation to timber frame wall constructions

System Classification:
Breathable Multifoil External Timber Frame System (Ventilated Rainscreen Build-Up)

Primary Function:
Breathable insulation + Secondary rain barrier + Radiant barrier + Vapour management

Installation Orientation:
Typically horizontal (recommended) or vertical application to timber frame / OSB

Minimum Overlap:
Integrated 100 mm built-in flap (horizontal installation)
Minimum 50 mm at other joints where applicable

Staple Fixing:
Typically 50–100 mm intervals (maximum 300 mm centres)

Airspace Requirement:
Ventilated cavity created by vertical counter battens
Unventilated cavity may be created behind insulation depending on build-up

Vapour Resistance:
1200 MNs/g

Watertightness:
Certified breathable membrane (secondary rain barrier)

External Finish:
Cladding, render board, façade system fixed to counter battens

Storage & Exposure:
Store indoors prior to installation.
All SuperFOIL products must be covered within 48 hours after installation.

External insulation of timber frame walls is often preferred due to improved hygrothermal performance and enhanced protection of the structural frame.

When correctly installed, the SuperFOIL breathable multifoil system provides:

• Vapour resistance (1200 MNs/g)
• Certified watertight breathable membrane
• Reduced thermal bridging
• Improved thermal performance
• Continuous external protective layer
• Radiant barrier performance

This system functions as a secondary rain barrier and must always be protected by a permanent external finish.

Pre-Installation Assessment

Before installation begins:

• Inspect timber frame for structural integrity and dryness
• Confirm sheathing (OSB or similar) is sound
• Ensure no active moisture issues are present
• Check roof, guttering, downpipes and rainwater systems
• Verify windows and door openings are weather-tight
• Preserve all existing ventilation outlets (consider Part F where applicable)
• Plan for service penetrations
• Assess need for scaffolding and weather protection
• Review local building regulation requirements

All electrical and service works must comply with relevant regulations and be carried out by qualified personnel.

For detailed step-by-step visual guidance on working with SuperFOIL insulation, please refer to the “Enternal Wall Insulation” section in the main menu.

SYSTEM CONFIGURATIONS

External timber frame walls may be constructed:

Timber frame without OSB
Timber frame with OSB sheathing

Both configurations are covered below.

INSTALLATION – TIMBER FRAME WITHOUT OSB

Step 1 – Initial Batten Frame

Install perimeter battens:

• Top
• Bottom
• Both vertical sides

Then install horizontal battens within the frame at maximum 600 mm centres.

This creates an unventilated cavity between timber structure and insulation.

Step 2 – Preparing the First Run

Measure wall length and cut insulation to size.

Using the integrated 100 mm built-in flap:

• Fold flap over exposed insulation layers
• Peel backing from integrated double-sided tape
• Press firmly to create waterproof sealed edge

Step 3 – Installing SuperFOIL

Install horizontally (recommended):

• Breathable membrane facing outward
• Perforated foil facing inward
• Start at bottom of wall
• Each run overlaps previous run using built-in 100 mm flap

Fixing method:

• Keep product taut
• Staple into battens
• Typical staple spacing 50–100 mm
• Maximum 300 mm centres

Seal each run before installing next:

• Peel integrated tape backing
• Apply gentle downward tension
• Press firmly to seal

Vertical installation is possible where required, starting from top and working downward, ensuring sealed overlaps.

INSTALLATION – TIMBER FRAME WITH OSB

For maximum thermal performance:

• Install battens over OSB to create rear airspace
• Apply SuperFOIL horizontally across battens
• Maintain integrated 100 mm overlap system

Alternatively, SuperFOIL may be fixed directly to OSB, however:

• This reduces thermal performance due to loss of rear airspace

Rear and front airspaces significantly improve overall system performance.

Staple spacing and overlap rules remain the same as above.

EDGE & ROLL JOINT DETAILING

If insulation stops at a corner:

• Turn back breathable membrane
• Trim insulation layers carefully
• Wrap membrane around corner
• Staple securely

If roll ends mid-wall:

• Trim insulation layers to centre of last batten
• Butt new roll to cut edge
• Fold breathable membrane over joint
• Seal with SuperFOIL Breathable Tape, Double-Sided Adhesive Tape

COUNTER BATTENS & VENTILATED CAVITY

Once insulation is fully secured and sealed:

• Install vertical counter battens over SuperFOIL
• Maximum 600 mm centres
• Bottom of frame left open for drainage and ventilation

This cavity:

• Allows water runoff
• Enables ventilation
• Protects timber frame
• Maintains reflective performance

If vertical cladding is used:

• Additional horizontal battens may be required

SEALING & AIRTIGHTNESS

All cuts, joints and penetrations must be sealed using SuperFOIL Breathable Tape, Double-Sided Adhesive tape.

Special attention required at:

• Window perimeters
• Door frames
• Service penetrations
• Roll joints
• Corners

Improper sealing may compromise:

• Weather resistance
• Wind tightness
• Thermal performance

WINDOW & DOOR FRAME DETAIL

• Roll insulation across opening
• Mark frame edges
• Cut carefully to fit snugly
• Seal perimeter with Breathable Tape, Double-Sided Adhesive Tape

Ensure:

• No exposed insulation
• Airtight finish
• Continuous membrane integrity

PENETRATIONS

At pipes, vents, ducting:

• Cut minimal opening
• Avoid excessive gaps
• Seal contact area fully using Breathable Tape

CORNER DETAILS

For corners > 90°:

• Frame each wall independently

For corners ≤ 90°:

• Install battens adjacent and equal distance from corner

Insulation must be securely stapled to battens on both walls.

INSECT MESH / CLOSURES

Perforated closure or insect mesh may be installed:

• At top of cavity
• At bottom of cavity

Purpose:

• Prevent pest entry
• Maintain airflow
• Allow water runoff

AIRSPACES & PERFORMANCE

Correct batten sizing is essential.

Airspaces:

• Improve effective R-Value
• Reflect radiant heat (up to 95%)
• Reduce conductive and convective heat loss
• Prevent moisture trapping

Insufficient airspace reduces system efficiency.

WEATHER PROTECTION

SuperFOIL acts as a secondary rain barrier.

It must be covered with permanent external finish within 48 hours of installation.

If immediate covering is not possible:

• Use tarpaulins or temporary protection

No SuperFOIL should remain permanently exposed.

CUTTING METHODS

Recommended:

• Utility knife (compress before cutting)
• Electric rotary cutter
• Heavy-duty shears

When trimming insulation layers:

• Peel back membrane
• Trim internal layers
• Avoid damaging membrane

Seal all cut edges.

INSTALLATION CHECKLIST

Before completion ensure:

• Timber frame inspected
• Product cut accurately
• All overlaps sealed
• Staples ≤ 300 mm centres
• Counter battens ≤ 600 mm centres
• Ventilated cavity maintained
• External finish installed
• Installation documented