Blown Masonry Cavity Walls- Technical Detail

External Masonry Cavity Walls

Masonry Cavity Walls

Masonry Cavity Wall Design

Full fill with injected glass mineral wool

  • Installed by trained and approved Mc03 technicians, monitored by the BBA

  • In-situ installation ensures intimate contact with both leaves of cavity wall preventing air movement and infiltration

  • Cavity is fully filled and delivers optimum thermal performance at low cost

Our Supafil® products are:

  • BBA Certified for all exposure zones

  • Non-combustible Euroclass A1 reaction to fire rating

  • A+ Generic BRE Green Guide rating

Knauf Insulation External Masonry Cavity Walls Blown In-Solution-UK

 

Products

Supafil® 34 and 40 are loose glass mineral wool insulation materials which are injected into existing or newly built masonry cavity walls. They require no mixing on site and are dry when installed, adding no water to the building.

Supafil® 34 and 40 cavity wall insulation is available only through approved installers fully trained by Knauf Insulation and approved by the British Board of Agrément (BBA). A list of approved installers is available on request.

Typical construction

Brick or block outer leaf (which may be rendered), cavity fully filled with Supafil® 34 and 40 cavity wall insulation, brick or block inner leaf. Internal finish of 12.50mm standard plasterboard on dabs.

Tests by the BBA confirm that Supafil® 34 and 40 cavity wall insulation will not transmit water to the inner leaf. Nor will they transmit moisture by capillary action across the cavity or from below damp-proof course level.

Supafil® 34 and 40 cavity wall insulation has negligible water vapour resistance, allowing water vapour to pass freely through them.

Guarantee

For installation in existing domestic properties, the Cavity Insulation Guarantee Agency (CIGA)offers a guarantee covering both materials and workmanship.

Installation

A survey is carried out prior to installation to ascertain the suitability of the building for insulation and to determine the position of flues and air vents, etc. Essential ventilation openings such as those providing combustion air or under floor ventilation, and all flues in the cavity wall, are checked and sleeved, or otherwise modified to prevent blockage by the insulation.

An approved cavity barrier is inserted as appropriate to isolate terraced or semi-detached properties and to close any open cavities.

A series of holes are drilled in accordance with the patterns detailed by the BBA Certificates. For new build schemes, the holes are usually drilled through the inner leaf and the insulation installed prior to plastering. For existing buildings, holes are usually drilled through the mortar joints in the outer leaf and are made good by re-pointing with mortar to match the wall finish as closely as possible.

Supafil® 34 and 40 cavity wall insulation is fed into an approved blowing machine and injected into the cavity under air pressure through a flexible hose fitted with a tapered nozzle.

The machine is fitted with a pressure sensor which automatically cuts off to stop the flow of material when the area of wall being insulated is filled to the correct density.

Specialised buildings

Knauf Insulation together with their approved installers have considerable knowledge and practical experience of installing Supafil®cavity wall insulation in various constructions such as: Cornish, BISF and other system-built houses.

Knauf Insulation will be pleased to advise on the compatibility of any building and its suitability for insulating with Supafil products.

Performance

Supafil® 34 and 40 cavity wall insulation will not deteriorate with age or settle and will therefore remain effective for the life of the building.

The operations of all approved installers are rigidly monitored by Knauf Insulation and the BBA in accordance with the terms of the BBA Certificates.

Thermal performance

Supafil® 34 cavity wall insulation has a thermal conductivity of 0.034 W/mK.

Supafil® 40 cavity wall insulation has a thermal conductivity of 0.040 W/mK.

Fire performance

Supafil® 34 and 40 cavity wall insulation is classified as Euroclass A1 to BS EN 13501-1, Which means that it is non-combustible and will not contribute to the development of a fire or flame spread.

The installation of Supafil®cavity wall insulation will not adversely affect the fire rating of the wall and will not constitute a toxic hazard in fire conditions.

Typical U-values for fully filled masonry cavity walls - new build

Product

Medium block (l- 0.45)

High strength aircrete (l- 0.19) Standard aircrete (l- 0.15) Lightweight aircrete (l- 0.11)
Supafil® 34
250 0.13 0.13 0.12 0.12
225 0.14 0.14 0.14 0.13
200 0.16 0.15 0.15 0.15
175 0.18 0.17 0.17 0.16
160 0.19 0.19 0.18 0.18
150 0.20 0.20 0.19 0.19
140 0.21 0.20 0.19 0.19
125 0.23 0.22 0.21 0.20
120 0.24 0.22 0.22 0.21
100 0.27 0.26 0.25 0.24
90 0.30 0.28 0.27 0.26
Supafil® 40
250 0.15 0.14 0.14 0.14
225 0.17 0.16 0.16 0.15
200 0.18 0.18 0.17 0.17
175 0.21 0.20 0.19 0.19
160 0.22 0.21 0.21 0.20
150 0.22 0.21 0.21 0.20
140 0.24 0.22 0.22 0.21
125 0.26 0.25 0.24 0.23
120 0.27 0.25 0.25 0.24
100 0.31 0.29 0.28 0.27
90 0.34 0.31 0.30 0.29

Note: The U-values have been calculated assuming that all walls are lined with 12.50mm standard plasterboard (0.190 W/mK) on dabs on standard blocks with 10mm mortar joints. Wall ties assumed to be stainless steel at 2.5 per m2 with a cross-sectional area of no more than 12.5mm2 for structural cavities up to 100mm wide. For cavities up to 150mm wide, the cross-sectional area of wall ties is assumed to be 24mm2. For cavities greater than 150mm, the cross-sectional area of wall ties is assumed to be 60mm2. Air gap correction level is zero. Multiple layers are required for several of the solutions detailed above.

 

Typical U-values for fully filled masonry cavity walls - existing

Product

Brick(l- 0.56)

Block (l- 1.13)

Block (l- 0.51) Block (l- 0.34)
Supafil® 34
100 0.28 0.28 0.28 0.27
85 0.32 0.33 0.31 0.31
75 0.35 0.36 0.35 0.34
65 0.39 0.40 0.39 0.37
50 0.47 0.49 0.46 0.45
Supafil® 40
100 0.32 0.33 0.31 0.31
85 0.36 0.37 0.36 0.35
75 0.39 0.41 0.39 0.38
65 0.44 0.45 0.43 0.42
50 0.52 0.55 0.52 0.50

Note: The U-values have been calculated assuming that all walls are lined with 12.50mm standard plasterboard (0.190 W/mK) on dabs on standard blocks with 10mm mortar joints. Wall ties assumed to be stainless steel at 2.5 per m2 with a cross-sectional area of no more than 12.5mm2 for structural cavities up to 100mm wide. For cavities up to 150mm wide, the cross-sectional area of wall ties is assumed to be 24mm. For cavities greater than 150mm, the cross-sectional area of wall ties is assumed to be 60mm2. Air gap correction level is zero. Multiple layers are required for several of the solutions detailed above.

Typical specification

Typical specification Supafil® 34*/40*/ glass mineral wool cavity wall insulation to be injected into the cavity by an Knauf Insulation/BBA Approved Installer. (*Delete as appropriate)

New cavity walls to receive Supafil® 34*/40* cavity wall insulation by injecting insulation into the cavity should be constructed so that insulation cannot penetrate ventilation ducts or pass through to cavities in adjoining buildings or compartments which are not to be insulated. Close fitting ducts or sleeves should be installed across the cavity to serve air bricks and other ventilation openings.

Cavity barriers should be installed at junctions with other properties and compartments, and as required by the Building Regulations.

Existing cavity walls to be inspected by the approved installer and all necessary builder’s work carried out prior to Supafil® 40* cavity wall insulation being injected.

All work to be in strict accordance with the procedures laid out in the relevant BBA Certificate and the Knauf Insulation “Operators” and “Survey and Assessment” manuals.

Alternatively, consult the National Building Specifications, Standard version clause/clauses…P11/40 and 220……………

Knauf Insulation specification clauses can be downloaded from knaufinsulation.co.uk/nbs

Contact our Technical Support Team