Thermal insulation:

The overall rate of heat transmission through and external wall ('U1 valve) results from the combined values of internal surface resistance, type and thickness of the walling materials.

The contribution of brickwork to insulation depends upon the density of the bricks and upon thier moisture content.

It is now generally accepted that for heat loss calculation purpose standard moisture contents should be assumed. Table gives the values


Standard moisture content for producted and exposed brickwork

Situation                                                            Moisture content % by volume

Internal walls Inner leaf of cavity walls having
continuous air space Wall protected by tile                                   
hanging or equivalent cladding

Walls exposed to rain, unrendered                                                    5.0
or rendered with untreated mortar

To obtain the conductivity value ('K') for brickwork at varying moisture contents laboratory test result may be converted, using the values in Table (2) See Example

Sound absorbtion

The absorption value of brickwork will not very significantly for most normal types of brick. Painting the surface reduces the absorption value. Plastering may increase or decrease the absorption depending upon the type used. Most common plasters with fairly hard and smooth finish will have a lower value than exposed brick. Table shows typical absorption values at three frequencies.

Absorption can be increased to some extent by filling some joints with a highly absorbent material or by having gaps in facing brickwork with an absorbent material behind.



Conversion factors for 'k' values of brickwork with variations in moisture content
Moisture content
(% by volume)            1         2       3        5      10      
Moisture factor      1.30    1.48   1.60   1.75   2.10


 Outer leaf

 Cavity  Insulation

 Inner leaf

 Inner surĀ­face finish

 U-value W/m2C

 Facing  brick


 Common  brick

 13mm  lightweight plaster


 Clinker block 1500 kg/  m3

 9.5mm insulating plaster board fixed to battens



 50mm mineral  fibre

 Common  brick


 50mm urea formal dehyde foam


Sound absorption of brickwork

                                       Absorption coefficient
Material                               125Hz         500Hz         4000Hz

Exposed brickwork          0.024          0.030          0.050
Gloss painted brickwork    0.012         0.017          0.025
Smooth finished Plaster    n.013         0.025           0.013

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