Insulation for a better tomorrow
Masonry Cavity Walls

Masonry Cavity Walls

External walls

URSA Cavity Batts are suitable for both full and partial fill masonry cavity walls and have BBA approval. Fully filled cavity wall systems offer the most cost effective solution for a given U-value and can easily achieve current and proposed Building Regulation requirements.

Two grades of URSA Cavity Batt are available;

URSA Cavity Batt 32 - thermal conductivity 0.032 W/mK.

URSA Cavity Batt 35 - thermal conductivity 0.035 W/mK.

BBA Certificate 09/4624.

Design

URSA Cavity Batts are suitable for both full and partial fill systems. The batts may be used in any exposure zone in walls up to 25m high.

Rainwater penetration may be avoided by ensuring the correct use of lintels and cavity trays with appropriate stop ends.

Work undertaken by the BRE has identified the importance of good workmanship and the following points must be carefully considered;

  • Ensure the residual cavity is kept clean and free from mortar dropping and other debris.
  • Clean the top edges of the URSA Cavity Batts and the wall ties before installing the next row of slabs. The use of a timber cavity board is recommended to help keep this area clean.
  • Do not push slabs down into a partially built section of cavity wall as this may dislodge mortar and bridge the cavity.
  • Small, cut sections of slab should be installed with the face against the masonry i.e. with the fibres running vertically.
  • Carefully cut, rather than tear, the slabs to fit around wall ties and other penetrations that cross the cavity.

Installation

The wall may be constructed leading with either leaf. It is good practice however to lead with the outer leaf as this allows the mortar joints on the cavity face to be cleaned and to check that the joints are all fully filled. The usual procedure for construction is;

  1. The leading leaf of masonry, ideally the outer leaf, is built with the first row of wall ties at 600mm centres where the insulation is to begin.
  2. The first row of URSA Cavity Batts, cut to size if necessary, may begin below the DPC in order to offer edge insulation to the floor.
  3. The inner leaf is then built, normally level with the top of the URSA Cavity Batts. It is permissible to build the outer leaf one brick higher to secure the next row of slabs – ensure mortar is cleaned from the cavity face.
  4. Raise the leading leaf to the level of the next row of wall ties, normally at 450mm vertical centres and 900mm centres horizontally. Ensure that the drip is positioned at the centre of the cavity and that the ties slope down towards the outer leaf. Excess mortar should be cleaned from this leaf before fitting the URSA Cavity Batts onto the lower ties.
  5. The outer leaf is then built to the level of the top of the slabs and the process repeated.
  6. The subsequent rows of slabs should be fitted with vertical joints staggered i.e. brick bond with all joints tightly butted. Batts with damaged edges or corners should not be used.
  7. As work proceeds ensure that the top edge of the URSA Cavity Batts is clean and free from mortar droppings. The use of a cavity batten will help to protect the slab edges as the next section is built.
  8. Cut sections of slab may be required around openings or at corners. It is essential that these be cut accurately to fill the space they are intended for and are adequately secured.
  9. Ensure that partially completed walls are protected from inclement weather (wind, rain and snow) and at the end of the day’s work.

URSA Cavity Batt 32 U-values

103mm brick, URSA Cavity Batt 32, 100mm block & plasterboard on dab.

 

U-Value

(W/m²K)

 

Block Type 75mm 85mm 100mm 125mm 150mm
Aircrete Block (0.15 W/mK) 0.29 0.27 0.24 0.20 0.17
Light Agg Block (0.34 W/mK) 0.32 0.29 0.26 0.21 0.18
Medium Block (0.57 W/mK) 0.33 0.30 0.26 0.22 0.18
Dense Block (1.13 W/mK) 0.34 0.31 0.27 0.22 0.19

For further information and more U-values see our technical brochure in the Documents section. Alternatively please contact URSA Technical Department.

 

Industry information

Sources of useful additional information

Accredited Construction Details
Linear thermal bridging details
More info
Accredited Construction Details (Scotland)
Linear thermal bridging details
More info
Concrete Block Association
Linear thermal bridging details
More info
Constructive Details
Linear thermal bridging details for aircrete blocks
More info

URSA Masonry Cavity Wall Psi-values

Corner (Normal) – SAP Ref: E16 (Default 0.18 W/mK)
Description U-value (W/m²K) Psi-value (W/mK) Temp. factor Download
100mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.23-0.24 0.06 0.90
CB0007
100mm URSA Cavity Batt 32 Light Block (0.45) 0.26 0.06 0.90
CB0010
100mm URSA Cavity Batt 32 Medium Block (0.75) 0.27 0.06 0.91
CB0013
100mm URSA Cavity Batt 32 Dense Block (1.30) 0.27 0.07 0.91
CB0016
125mm URSA Cavity Batt 32 AAC Block 0.11-0.19 0.19-0.21 0.05 0.92
CB0008
125mm URSA Cavity Batt 32 Light Block 0.45 0.22 0.05 0.92
CB0011
125mm URSA Cavity Batt 32 Medium Block 0.75 0.22 0.06 0.92
CB0014
125mm URSA Cavity Batt 32 Dense Block 1.30 0.22 0.06 0.92
CB0017
150mm URSA Cavity Batt 32 AAC Block 0.11-0.19 0.17-0.18 0.05 0.93
CB0009
150mm URSA Cavity Batt 32 Light Block 0.45 0.19 0.05 0.93
CB0012
150mm URSA Cavity Batt 32 Medium Block 0.75 0.19 0.06 0.93
CB0015
150mm URSA Cavity Batt 32 Dense Block 1.30 0.19 0.06 0.93
CB0018
Corner (Inverted) – SAP Ref: E17 (Default 0.00 W/mK)
Description U-value (W/m²K) Psi-value (W/mK) Temp. factor Download
100mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.23-0.24 -0.09 0.97
CB0025
100mm URSA Cavity Batt 32 Light Block (0.45) 0.26 -0.11 0.97
CB0028
100mm URSA Cavity Batt 32 Medium Block (0.75) 0.27 -0.11 0.97
CB0031
100mm URSA Cavity Batt 32 Dense Block (1.30) 0.27 -0.12 0.97
CB0034
125mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.19-0.21 -0.08 0.97
CB0026
125mm URSA Cavity Batt 32 Light Block (0.45) 0.22 -0.10 0.97
CB0029
125mm URSA Cavity Batt 32 Medium Block (0.75) 0.22 -0.10 0.97
CB0032
125mm URSA Cavity Batt 32 Dense Block (1.30) 0.22 -0.10 0.97
CB0035
150mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.17-0.18 -0.08 0.98
CB0027
150mm URSA Cavity Batt 32 Light Block (0.45) 0.19 -0.09 0.98
CB0030
150mm URSA Cavity Batt 32 Medium Block (0.75) 0.19 -0.09 0.98
CB0033
150mm URSA Cavity Batt 32 Dense Block (1.30) 0.19 -0.09 0.98
CB0036
Loft (Gable) (U=0.16 W/m²K) – SAP Ref: E12 (Default 0.48 W/mK)
Description U-value (W/m²K) Psi-value (W/mK) Temp. factor Download
100mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.23-0.24 0.07 0.90
CB0039
100mm URSA Cavity Batt 32 Light Block (0.45) 0.26 0.12 0.87
CB0040
100mm URSA Cavity Batt 32 Medium Block (0.75) 0.27 0.15 0.85
CB0041
100mm URSA Cavity Batt 32 Dense Block (1.30) 0.27 0.21 0.81
CB0042
125mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.19-0.21 0.07 0.90
CB0045
125mm URSA Cavity Batt 32 Light Block (0.45) 0.22 0.11 0.88
CB0046
125mm URSA Cavity Batt 32 Medium Block (0.75) 0.22 0.15 0.86
CB0047
125mm URSA Cavity Batt 32 Dense Block (1.30) 0.22 0.22 0.83
CB0048
150mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.17-0.18 0.07 0.91
CB0051
150mm URSA Cavity Batt 32 Light Block (0.45) 0.19 0.11 0.88
CB0052
150mm URSA Cavity Batt 32 Medium Block (0.75) 0.19 0.15 0.86
CB0053
150mm URSA Cavity Batt 32 Dense Block (1.30) 0.19 0.22 0.83
CB0054
Loft (Gable) (U=0.10 W/m²K) – SAP Ref: E12 (Default 0.48 W/mK)
Description U-value (W/m²K) Psi-value (W/mK) Temp. factor Download
100mm URSA CAVITY BATT 32 AAC Block (0.11-0.19) 0.23-0.24 0.07 0.91
CB0057
100mm URSA CAVITY BATT 32 Light Block (0.45) 0.26 0.10 0.89
CB0058
100mm URSA CAVITY BATT 32 Medium Block (0.75) 0.27 0.12 0.87
CB0059
100mm URSA CAVITY BATT 32 Dense Block (1.30) 0.27 0.18 0.85
CB0060
125mm URSA CAVITY BATT 32 AAC Block (0.11-0.19) 0.19-0.21 0.06 0.92
CB0063
125mm URSA CAVITY BATT 32 Light Block (0.45) 0.22 0.09 0.90
CB0064
125mm URSA CAVITY BATT 32 Medium Block (0.75) 0.22 0.13 0.88
CB0065
125mm URSA CAVITY BATT 32 Dense Block (1.30) 0.22 0.18 0.86
CB0066
150mm URSA CAVITY BATT 32 AAC Block (0.11-0.19) 0.17-0.18 0.06 0.92
CB0069
150mm URSA CAVITY BATT 32 Light Block (0.45) 0.19 0.09 0.90
CB0070
150mm URSA CAVITY BATT 32 Medium Block (0.75) 0.19 0.12 0.90
CB0071
150mm URSA CAVITY BATT 32 Dense Block (1.30) 0.19 0.18 0.86
CB0072
Loft (Eaves) (U=0.16 W/m²K) – SAP Ref: E10 (Default 0.12 W/mK)
Description U-value (W/m²K) Psi-value (W/mK) Temp. factor Download
100mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.23-0.24 0.07 0.91
CB0075
100mm URSA Cavity Batt 32 Light Block (0.45) 0.26 0.07 0.91
CB0076
100mm URSA Cavity Batt 32 Medium Block (0.75) 0.27 0.08 0.91
CB0077
100mm URSA Cavity Batt 32 Dense Block (1.30) 0.27 0.08 0.92
CB0078
125mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.19-0.21 0.07 0.91
CB0081
125mm URSA Cavity Batt 32 Light Block (0.45) 0.22 0.07 0.91
CB0082
125mm URSA Cavity Batt 32 Medium Block (0.75) 0.22 0.08 0.92
CB0083
125mm URSA Cavity Batt 32 Dense Block (1.30) 0.22 0.08 0.92
CB0084
150mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.17-0.18 0.07 0.91
CB0087
150mm URSA Cavity Batt 32 Light Block (0.45) 0.19 0.08 0.92
CB0088
150mm URSA Cavity Batt 32 Medium Block (0.75) 0.19 0.08 0.92
CB0089
150mm URSA Cavity Batt 32 Dense Block (1.30) 0.19 0.08 0.92
CB0090
Loft (Eaves) (U=0.10 W/m²K) – SAP Ref: E10 (Default 0.12 W/mK)
Description U-value (W/m²K) Psi-value (W/mK) Temp. factor Download
100mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.23-0.24 0.09 0.91
CB0093
100mm URSA Cavity Batt 32 Light Block (0.45) 0.26 0.09 0.91
CB0094
100mm URSA Cavity Batt 32 Medium Block (0.75) 0.27 0.09 0.91
CB0095
100mm URSA Cavity Batt 32 Dense Block (1.30) 0.27 0.09 0.91
CB0096
125mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.19-0.21 0.09 0.91
CB0099
125mm URSA Cavity Batt 32 Light Block (0.45) 0.22 0.09 0.91
CB0100
125mm URSA Cavity Batt 32 Medium Block (0.75) 0.22 0.10 0.91
CB0101
125mm URSA Cavity Batt 32 Dense Block (1.30) 0.22 0.10 0.92
CB0102
150mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.17-0.18 0.09 0.91
CB0105
150mm URSA Cavity Batt 32 Light Block (0.45) 0.19 0.09 0.92
CB0106
150mm URSA Cavity Batt 32 Medium Block (0.75) 0.19 0.10 0.92
CB0107
150mm URSA Cavity Batt 32 Dense Block (1.30) 0.19 0.10 0.92
CB0108
Intermediate Timber Floor Within Dwelling – SAP Ref: E6 (Default 0.14 W/mK)
Description U-value (W/m²K) Psi-value (W/mK) Temp. factor Download
100mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.23-0.24 0.00 0.92
CB0109
100mm URSA Cavity Batt 32 Light Block (0.45) 0.26 0.00 0.96
CB0110
100mm URSA Cavity Batt 32 Medium Block (0.75) 0.27 0.00 0.96
CB0111
100mm URSA Cavity Batt 32 Dense Block (1.30) 0.27 0.00 0.96
CB0112
125mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.19-0.21 0.00 0.96
CB0113
125mm URSA Cavity Batt 32 Light Block (0.45) 0.22 0.00 0.97
CB0114
125mm URSA Cavity Batt 32 Medium Block (0.75) 0.22 0.00 0.97
CB0115
125mm URSA Cavity Batt 32 Dense Block (1.30) 0.22 0.00 0.96
CB0116
150mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.17-0.18 0.00 0.97
CB0117
150mm URSA Cavity Batt 32 Light Block (0.45) 0.19 0.00 0.97
CB0118
150mm URSA Cavity Batt 32 Medium Block (0.75) 0.19 0.00 0.97
CB0119
150mm URSA Cavity Batt 32 Dense Block (1.30) 0.19 0.00 0.97
CB0120
Intermediate Concrete Floor Within Dwelling – SAP Ref: E6 (Default 0.14 W/mK)
Description U-value (W/m²K) Psi-value (W/mK) Temp. factor Download
100mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.23-0.24 0.01 0.96
CB0121
100mm URSA Cavity Batt 32 Light Block (0.45) 0.26 0.01 0.96
CB0122
100mm URSA Cavity Batt 32 Medium Block (0.75) 0.27 0.01 0.95
CB0123
100mm URSA Cavity Batt 32 Dense Block (1.30) 0.27 0.01 0.95
CB0124
125mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.19-0.21 0.01 0.97
CB0125
125mm URSA Cavity Batt 32 Light Block (0.45) 0.22 0.01 0.96
CB0126
125mm URSA Cavity Batt 32 Medium Block (0.75) 0.22 0.01 0.96
CB0127
125mm URSA Cavity Batt 32 Dense Block (1.30) 0.22 0.01 0.96
CB0128
150mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.17-0.18 0.01 0.97
CB0129
150mm URSA Cavity Batt 32 Light Block (0.45) 0.19 0.00 0.97
CB0130
150mm URSA Cavity Batt 32 Medium Block (0.75) 0.19 0.00 0.97
CB0131
150mm URSA Cavity Batt 32 Dense Block (1.30) 0.19 0.00 0.97
CB0132
Jamb – SAP Ref: E4 (Default 0.10 W/mK)
Description U-value (W/m²K) Psi-value (W/mK) Temp. factor Download
100mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.23-0.24 0.03 0.91
CB0133
100mm URSA Cavity Batt 32 Light Block (0.45) 0.26 0.02 0.92
CB0134
100mm URSA Cavity Batt 32 Medium Block (0.75) 0.27 0.02 0.92
CB0135
100mm URSA Cavity Batt 32 Dense Block (1.30) 0.27 0.02 0.92
CB0136
125mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.19-0.21 0.03 0.91
CB0137
125mm URSA Cavity Batt 32 Light Block (0.45) 0.22 0.02 0.91
CB0138
125mm URSA Cavity Batt 32 Medium Block (0.75) 0.22 0.02 0.91
CB0139
125mm URSA Cavity Batt 32 Dense Block (1.30) 0.22 0.02 0.91
CB0140
150mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.17-0.18 0.03 0.91
CB0141
150mm URSA Cavity Batt 32 Light Block (0.45) 0.19 0.03 0.91
CB0142
150mm URSA Cavity Batt 32 Medium Block (0.75) 0.19 0.03 0.91
CB0143
150mm URSA Cavity Batt 32 Dense Block (1.30) 0.19 0.03 0.91
CB0144
Sill – SAP Ref: E3 (Default 0.08 W/mK)
Description U-value (W/m²K) Psi-value (W/mK) Temp. factor Download
100mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.23-0.24 0.02 0.90
CB0145
100mm URSA Cavity Batt 32 Light Block (0.45) 0.26 0.02 0.90
CB0146
100mm URSA Cavity Batt 32 Medium Block (0.75) 0.27 0.02 0.90
CB0147
100mm URSA Cavity Batt 32 Dense Block (1.30) 0.27 0.02 0.90
CB0148
125mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.19-0.21 0.03 0.90
CB0149
125mm URSA Cavity Batt 32 Light Block (0.45) 0.22 0.02 0.90
CB0150
125mm URSA Cavity Batt 32 Medium Block (0.75) 0.22 0.02 0.90
CB0151
125mm URSA Cavity Batt 32 Dense Block (1.30) 0.22 0.02 0.90
CB0152
150mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.17-0.18 0.03 0.90
CB0153
150mm URSA Cavity Batt 32 Light Block (0.45) 0.19 0.02 0.90
CB0154
150mm URSA Cavity Batt 32 Medium Block (0.75) 0.19 0.02 0.90
CB0155
150mm URSA Cavity Batt 32 Dense Block (1.30) 0.19 0.02 0.90
CB0156
Ground Floor – SAP Ref: E5 (Default 0.32 W/mK) Solid Floor. 125mm PUR insulation
Description U-value (W/m²K) Psi-value (W/mK) Temp. factor Download
100mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.23-0.24 0.08 0.94
CB0157
100mm URSA Cavity Batt 32 Light Block (0.45) 0.26 0.10 0.92
CB0158
100mm URSA Cavity Batt 32 Medium Block (0.75) 0.27 0.12 0.91
CB0159
100mm URSA Cavity Batt 32 Dense Block (1.30) 0.27 0.17 0.90
CB0160
125mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.19-0.21 0.07 0.94
CB0161
125mm URSA Cavity Batt 32 Light Block (0.45) 0.22 0.10 0.93
CB0162
125mm URSA Cavity Batt 32 Medium Block (0.75) 0.22 0.13 0.92
CB0163
125mm URSA Cavity Batt 32 Dense Block (1.30) 0.22 0.17 0.90
CB0164
150mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.17-0.18 0.07 0.94
CB0165
150mm URSA Cavity Batt 32 Light Block (0.45) 0.19 0.10 0.93
CB0166
150mm URSA Cavity Batt 32 Medium Block (0.75) 0.19 0.12 0.92
CB0167
150mm URSA Cavity Batt 32 Dense Block (1.30) 0.19 0.17 0.90
CB0168
Ground Floor – SAP Ref: E5 (Default 0.32 W/mK) Suspended/Beam & Block. 125mm PUR insulation
Description U-value (W/m²K) Psi-value (W/mK) Temp. factor Download
100mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.23-0.24 0.06 0.94
CB0169
100mm URSA Cavity Batt 32 Light Block (0.45) 0.26 0.09 0.92
CB0170
100mm URSA Cavity Batt 32 Medium Block (0.75) 0.27 0.12 0.91
CB0171
100mm URSA Cavity Batt 32 Dense Block (1.30) 0.27 0.17 0.89
CB0172
125mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.19-0.21 0.06 0.94
CB0173
125mm URSA Cavity Batt 32 Light Block (0.45) 0.22 0.10 0.92
CB0174
125mm URSA Cavity Batt 32 Medium Block (0.75) 0.22 0.13 0.91
CB0175
125mm URSA Cavity Batt 32 Dense Block (1.30) 0.22 0.18 0.90
CB0176
150mm URSA Cavity Batt 32 AAC Block (0.11-0.19) 0.17-0.18 0.06 0.94
CB0177
150mm URSA Cavity Batt 32 Light Block (0.45) 0.19 0.10 0.93
CB0178
150mm URSA Cavity Batt 32 Medium Block (0.75) 0.19 0.13 0.92
CB0179
150mm URSA Cavity Batt 32 Dense Block (1.30) 0.19 0.18 0.90
CB0180

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