Calculations‎ > ‎

U Values

Glazing

TypeU - Value (W/m2K)
 Double Glazing, air filled, 6mm gap  3.1
 Double Glazing, air filled, 12mm gap 2.8
 Single Glazing 4.8


Double thickness brick wall without air gap

Wall Component

Conductivity (W/mK)

Thickness(m)

Conductance(W/m2K)

Resistance (m2K/W)

Outside Air Layer

0.04

External render

0.50

0.018

27.78

0.04

External brick

0.77

0.102

7.55

0.13

Internal brick

0.56

0.102

5.49

0.18

Dense Plaster

0.57

0.013

43.85

0.02

Inside Air Layer

-

-

-

0.13

Totals

0.19

0.54

Overall U-Value

1.85

Double thickness brick wall without air gap but with wooden cladding

Wall Component

Conductivity (W/mK)

Thickness(m)

Conductance

(W/m2K)

Resistance  

(m2K/W)

Resistance

(m2K/W)

Outside Air Layer

0.04

Wooden Cladding and battens

0.13

0.05

2.6

-

0.38

Sheltered surface resistance

0.13

-

External brick

0.77

0.102

7.55

0.13

0.13

Internal brick

0.56

0.102

5.49

0.18

0.18

Dense Plaster

0.57

0.013

43.85

0.02

0.02

Inside Air Layer

-

-

-

0.13

0.13

Totals

0.19

0.59

0.88

Net Resistance

0.61

Net U Value (W/m2K)

1.64



Note: BRE guidance is to disregard the rain cladding and use a sheltered surface resistance value. However, the calculation should allow for timber battens. If the battens occupy 10% of the surface area then the effective resistance is
1/((0.9/0.59)+(0.1/0.88)) = 1/(1.64 + 0.11) = 0.61 m2K/W

Double thickness brick wall without air gap but with wooden cladding and insulation between battens.

Wall Component

Conductivity (W/mK)

Thickness(m)

Conductance

(W/m2K)

Resistance

m2K/W

Resistance

m2K/W

Outside Air Layer

0.04

0.04

Wooden Cladding and Battens

0.13

0.05

2.6

-

0.38

Wooden Cladding

0.13

0.025

5.2

0.19

-

Insulation between battens

0.03

0.025

1.2

0.83

-

External brick

0.77

0.102

7.55

0.13

0.13

Internal brick

0.56

0.102

5.49

0.18

0.18

Dense Plaster

0.57

0.013

43.85

0.02

0.02

Inside Air Layer

-

-

-

0.13

0.13

Totals

0.19

1.52

0.88

Net Resistance

1.4


Net U Value (W/m2K)

0.71



Double thickness brick wall with air gap and render

Wall Component

Conductivity (W/mK)

Thickness(m)

Conductance

(W/m2K)

Resistance (m2K/W)

Outside Air Layer

-

-

-

0.04

External render

0.50

0.018

27.78

0.04

External brick

0.77

0.102

7.55

0.13

Air Cavity

-

0.1

-

0.18

Internal brick

0.56

0.102

5.49

0.18

Dense Plaster

0.57

0.013

43.85

0.02

Inside Air Layer

-

-

-

0.13

Totals

0.19

0.72

Overall U-Value

1.39



Double thickness brick wall with insulated cavity and render

Wall Component

Conductivity (W/mK)

Thickness(m)

Conductance

(W/m2K)

Resistance (m2K/W)

Outside Air Layer

-

-

-

0.04

External render

0.50

0.018

27.78

0.04

External brick

0.77

0.102

7.55

0.13

Insulated Cavity

0.039

0.089

0.44

2.27

Internal brick

0.56

0.102

5.49

0.18

Dense Plaster

0.57

0.013

43.85

0.02

Inside Air Layer

-

-

-

0.13

Totals

0.19

2.81

Overall U-Value

0.36




Double thickness brick wall with air gap

Wall Component

Conductivity (W/mK)

Thickness(m)

Conductance

(W/m2K)

Resistance (m2K/W)

Outside Air Layer

-

-

-

0.04

External brick

0.77

0.102

7.55

0.13

Air Cavity

-

0.1

-

0.18

Internal brick

0.56

0.102

5.49

0.18

Dense Plaster

0.57

0.013

43.85

0.02

Inside Air Layer

-

-

-

0.13

Totals

0.19

0.68

Overall U-Value

1.47



Double thickness brick wall with insulated cavity

Wall Component

Conductivity (W/mK)

Thickness(m)

Conductance

(W/m2K)

Resistance (m2K/W)

Outside Air Layer

- - -

0.04

External render

0.50

0.018

27.78

0.04

External brick

0.77

0.102

7.55

0.13

Insulated Cavity

0.039

0.1

0.39

2.56

Internal brick

0.56

0.102

5.49

0.18

Dense Plaster

0.57

0.013

43.85

0.02

Inside Air Layer

-

-

-

0.13

Totals

0.19

3.1

Overall U-Value

0.32