5. Roof Insulation

A roof assembly shall achieve the minimum total thermal resistance (R-value) of the specified requirement in the Table below  for the direction of heat flow.

The direction of heat flow in in the table is considered to be the predominant direction of heat flow for the hours of occupation of the building. It takes into account the higher rate of occupancy of houses at night time rather than day time. Where “downwards” is specified in the table, this indicates summer heat (a downwards heat flow into the building) as the major concern.

A combined downward and upwards requirement means that summer and winter (heating and cooling) have a roughly similar level of energy use on an annual basis, while an upward flow indicates that heat loss from the building during winter as the major concern.

Minimum Total R-values of Roofs and Ceilings
Energy zone Energy zone

1

 2 3 4 5 6

7
5 5H
Heating (H) & Cooling (C)

H

 C H C H C H C H C H C H C H C

Low (L), Medium (M), High (H)

 M M M L L H L L L M L M H L H

M
Minimum required Total
R-value(m².K/W)

3.7

 3.7 2.7

3.7
Direction of heat flow

Up

 Up  Up & Down Up Down

Up
Minimum Total R-value (m².K.W) of roof and ceiling materials

0.30 – 0.35

 0.36 – 0.48

0.30 – 0.35
Estimated minimum added R-value of Insulation(m².K.W)

3.35

 3.22 2.35

3.35
NOTE: Zone 5H high humidity to be taken into account. Adequate insulation and roof ventilation must be provided