NCC 2022 Volume One - Building Code of Australia Class 2 to 9 buildings
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37

Specification 37 Calculation of U-Value and solar admittance

Specification 37 Calculation of U-Value and solar admittance

This specification describes the methods of calculating the U-Value and solar admittance of a wall-glazing construction.

For determining the aspect of a wall-glazing construction—

  1. the northern aspect is at or within 45° of true north; and
  2. the southern aspect is at or within 45° of true south; and
  3. the eastern aspect is within 45° of true east; and
  4. the western aspect is within 45° of true west.

(1) For the purposes of this method, a wall-glazing construction only includes the walls and glazing facing a single aspect.

(2) The Total System U-Value of the wall component of a wall-glazing construction must be calculated as the inverse of the Total R-Value, including allowance for thermal bridging, in accordance with—

  1. AS/NZS 4859.2; or
  2. Specification 38 for spandrel panels.

(3) The Total System U-Value of a wall-glazing construction must be calculated as the area-weighted average of the Total System U-Value of each of the components of the wall-glazing construction.

(4) The Total System U-Value must not exceed the applicable value in J4D6(1).

(1) For the purposes of this method, a wall-glazing construction only includes the walls and glazing facing multiple aspects.

(2) The Total System U-Value of the wall component of a wall-glazing construction must be calculated as the inverse of the Total R-Value, including allowance for thermal bridging, in accordance with—

  1. AS/NZS 4859.2; or
  2. Specification 38 for spandrel panels.

(3) The Total System U-Value of a wall-glazing construction must be calculated as the area-weighted average of the Total System U-Value of each of the components of the wall-glazing construction.

(4) The Total System U-Value must not exceed the applicable value in J4D6(1).

(1) The solar admittance of a wall-glazing construction must be calculated in accordance with the following formula:

S A = A W 1 × S W 1 × S H G C W 1 A W A L L + A W 2 × S W 2 × S H G C W 2 A W A L L + ... MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4uaiaadg eacqGH9aqpdaWcaaqaaiaadgeadaWgaaWcbaGaam4vaiaaigdaaeqa aGGaaOGae831aqRaam4uamaaBaaaleaacaWGxbGaaGymaaqabaGccq WFxdaTcaWGtbGaamisaiaadEeacaWGdbWaaSbaaSqaaiaadEfacaaI XaaabeaaaOqaaiaadgeadaWgaaWcbaGaam4vaiaadgeacaWGmbGaam itaaqabaaaaOGaey4kaSYaaSaaaeaacaWGbbWaaSbaaSqaaiaadEfa caaIYaaabeaakiab=Dna0kaadofadaWgaaWcbaGaam4vaiaaikdaae qaaOGae831aqRaam4uaiaadIeacaWGhbGaam4qamaaBaaaleaacaWG xbGaaGOmaaqabaaakeaacaWGbbWaaSbaaSqaaiaadEfacaWGbbGaam itaiaadYeaaeqaaaaakiabgUcaRiaac6cacaGGUaGaaiOlaaaa@61DB@

(2) In the formula at (1)—

  1. SAMathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4uaiaadg eaaaa@3792@  
    = the wall-glazing construction solar admittance; and
  2. AW1,AW2,...MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyqamaaBa aaleaacaWGxbGaaGymaaqabaGccaGGSaGaamyqamaaBaaaleaacaWG xbGaaGOmaaqabaGccaGGSaGaaiOlaiaac6cacaGGUaaaaa@3E91@  
    = the area of each glazing element; and
  3. SW1,SW2,...MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4uamaaBa aaleaacaWGxbGaaGymaaqabaGccaGGSaGaam4uamaaBaaaleaacaWG xbGaaGOmaiaacYcacaGGUaGaaiOlaiaac6caaeqaaaaa@3EAB@  
    = the shading multiplier for each glazing element in accordance with S37C7; and
  4. SHGCW1,W2,...MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4uaiaadI eacaWGhbGaam4qamaaBaaaleaacaWGxbGaaGymaiaacYcacaWGxbGa aGOmaiaacYcacaGGUaGaaiOlaiaac6caaeqaaaaa@3FFE@  
    = the total system SHGC of each glazing element; and
  5. AWALLMathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyqamaaBa aaleaacaWGxbGaamyqaiaadYeacaWGmbaabeaaaaa@3A2A@  
    = the total wall-glazing construction area.

(3) The solar admittance of the wall-glazing construction must not exceed the applicable value in J4D6(5).

(1) The solar admittance of wall-glazing construction must achieve a representative air-conditioning energy value less than that achieved by the reference solar admittance, when using the following formula:

E R = A N α N S A N + A E α E S A E + A S α S S A S + A W α W S A W MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyramaaBa aaleaacaWGsbaabeaakiabg2da9iaadgeadaWgaaWcbaGaamOtaaqa baGccqaHXoqydaWgaaWcbaGaamOtaaqabaGccaWGtbGaamyqamaaBa aaleaacaWGobaabeaakiabgUcaRiaadgeadaWgaaWcbaGaamyraaqa baGccqaHXoqydaWgaaWcbaGaamyraaqabaGccaWGtbGaamyqamaaBa aaleaacaWGfbaabeaakiabgUcaRiaadgeadaWgaaWcbaGaam4uaaqa baGccqaHXoqydaWgaaWcbaGaam4uaaqabaGccaWGtbGaamyqamaaBa aaleaacaWGtbaabeaakiabgUcaRiaadgeadaWgaaWcbaGaam4vaaqa baGccqaHXoqydaWgaaWcbaGaam4vaaqabaGccaWGtbGaamyqamaaBa aaleaacaWGxbaabeaaaaa@57F4@

(2) In the formula at (1)—

  1. ERMathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyramaaBa aaleaacaWGsbaabeaaaaa@37C1@  
    = the representative air-conditioning energy value; and
  2. AN,E,S,WMathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyqamaaBa aaleaacaWGobGaaiilaiaadweacaGGSaGaam4uaiaacYcacaWGxbaa beaaaaa@3C47@  
    = the area of the wall-glazing construction facing each aspect; and
  3. αN,E,S,WMathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqySde2aaS baaSqaaiaad6eacaGGSaGaamyraiaacYcacaWGtbGaaiilaiaadEfa aeqaaaaa@3D20@  
    = the solar admittance weighting coefficient of each aspect equal to—
    1. where the glazing area on an aspect is less than 20% of the wall-glazing construction area, 0; and
    2. the values in Table S37C6a and Table S37C6b; and
  4. SAN,E,S,WMathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4uaiaadg eadaWgaaWcbaGaamOtaiaacYcacaWGfbGaaiilaiaadofacaGGSaGa am4vaaqabaaaaa@3D1F@  
    = the wall-glazing construction solar admittance of each aspect—
    1. equal to the applicable value in J4D6(5) in the reference case; and
    2. calculated in accordance with S37C5(1) in the proposed case.
Table S37C6a Solar admittance weighting coefficient — Class 2 common area, Class 5, 6, 7, 8 or 9b building or Class 9a building other than a ward area
Aspect Climate zone 1 Climate zone 2 Climate zone 3 Climate zone 4 Climate zone 5 Climate zone 6 Climate zone 7 Climate zone 8
Northern 1.47 1.95 1.95 2.05 2.28 2.12 2.40 1.88
Southern 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
Eastern 1.39 1.58 1.63 1.72 1.72 1.62 1.84 1.92
Western 1.41 1.68 1.65 1.69 1.75 1.67 1.92 1.25
Table S37C6b Solar admittance weighting coefficient — Class 3 or 9c building or Class 9a ward area
Aspect Climate zone 1 Climate zone 2 Climate zone 3 Climate zone 4 Climate zone 5 Climate zone 6 Climate zone 7 Climate zone 8
Northern 1.42 1.77 1.72 1.55 1.88 1.52 1.60 1.24
Southern 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
Eastern 1.30 1.49 1.48 1.37 1.48 1.28 1.35 1.26
Western 1.37 1.54 1.50 1.36 1.52 1.33 1.40 1.05

For the purpose of calculating solar admittance, the shading multiplier is—

  1. for shading provided by an external permanent projection that extends horizontally on both sides of the glazing for the same projection distance P, as shown in Figure S37C7—
    1. the value in Table S37C7a for shading on the northern, eastern or western aspects; or
    2. the value in Table S37C7b for shading on the southern aspect; or
  2. 0.35 for shading that is provided by an external shading device such as a shutter, blind, vertical or horizontal building screen with blades, battens or slats, which—
    1. is capable of restricting at least 80% of summer solar radiation; and
    2. if adjustable, will operate automatically in response to the level of solar radiation.
Table S37C7a Shading multipliers — Northern, eastern and western aspects
G/H P/H = 0 P/H = 0.1 P/H = 0.2 P/H = 0.3 P/H = 0.4 P/H = 0.5 P/H = 0.6 P/H = 0.7 P/H = 0.8 P/H = 0.9 P/H = 1
0 1.00 0.90 0.80 0.72 0.64 0.57 0.51 0.46 0.41 0.38 0.35
0.1 1.00 0.95 0.89 0.81 0.74 0.66 0.59 0.52 0.47 0.42 0.40
0.2 1.00 0.98 0.94 0.89 0.82 0.75 0.68 0.62 0.56 0.51 0.47
0.3 1.00 1.00 0.97 0.94 0.89 0.84 0.78 0.72 0.66 0.61 0.57
0.4 1.00 1.00 0.99 0.97 0.94 0.90 0.86 0.82 0.77 0.73 0.68
0.5 1.00 1.00 1.00 0.99 0.97 0.95 0.92 0.90 0.86 0.83 0.79
Table S37C7b Shading multipliers — Southern aspect
G/H P/H = 0 P/H = 0.1 P/H = 0.2 P/H = 0.3 P/H = 0.4 P/H = 0.5 P/H = 0.6 P/H = 0.7 P/H = 0.8 P/H = 0.9 P/H = 1
0 1.00 0.93 0.87 0.82 0.77 0.73 0.69 0.65 0.62 0.60 0.58
0.1 1.00 0.97 0.93 0.88 0.84 0.79 0.75 0.71 0.67 0.64 0.62
0.2 1.00 0.98 0.96 0.93 0.89 0.85 0.81 0.77 0.73 0.70 0.68
0.3 1.00 0.99 0.98 0.96 0.93 0.90 0.87 0.83 0.80 0.77 0.74
0.4 1.00 1.00 0.99 0.98 0.96 0.94 0.91 0.89 0.86 0.84 0.81
0.5 1.00 1.00 0.99 0.99 0.98 0.96 0.95 0.93 0.91 0.90 0.88
Figure S37C7 Permanent external shading – measurement of P, G and H
image-S37C7-permanent-external-shading-measurement-p-g-h.svg