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Total R-Values
Added R-Values

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We are accredited with Design Matters National (formerly the BDAV) and hold a Certificate 4 in NatHERS Assessments - CPP41212.

We are also a small Australian family business. All our reporting and assessments are done right here in Australia, not off shore.




The R-Value is a measure of thermal resistance of a material's ability to resist heat flow:
R-Value = Thickness (m) / Thermal conductivity (W/mK)
Heat Flow

Total R-Value, Added R-Value and
R-Values are terms that are used within the Building Industry.

These terms are on or in; Working Drawings, House Energy Rating documentation, insulation products and insulation supplier's brochures. It is important to understand which term relates to what process.

Applying the wrong R-Value could mean that the project won't meet the current NCC's, Building Codes of Australia requirements.

Total R-Values

A Total R-Value is the sum of the R-values of the individual component's within a structure, for example a brick veneer wall. The Total R-Value includes any building materials, insulation materials, airspaces and internal/external air film surfaces.

Total R-Value R2.68: The Brick Veneer Wall below with all of its components as listed below has a Total R-Value of R2.68, notice how the Reflective Paper has no R-Value.
It is a misconception that Reflective Paper has an independent
R-Value of R1.3, the R1.3 is the result of a Total R-Value as
explained below.

Component R-Value
1. Outdoor Air Film R0.04
2. 110mm Brickwork R0.14
3. 50mm Air Cavity R0.28
4. Reflective Paper R0.00
5. Wall Batt R2.00
6. Plasterboard R0.10
7. Indoor Air Film R0.12
Total R-Value R2.68
Brick Wall

Total R-Value R1.28: The Brick Veneer Wall above with no Wall Batt now has an extra 90mm stud void and the reflective paper now comes into play with only an added R0.60 to the Total R-Value.
Total R-Value 2.68 - R2.00 + R0.60 = Total R-Value 1.28

Total R-Value R0.56: The Brick Veneer Wall above with no Wall Batt and no Reflective Paper, now combines the 90mm stud void with the 50mm Air Cavity into one void area with only an added R0.16 to the Total R-Value.
Total R-Value 1.28 - R0.60 - R0.28 + R0.16 = Total R-Value 0.56

Added R-Values

The term Added R-Values is generally related to wall, ceiling/roof and sub/floor insulation products.

The software programs that perform House Energy Ratings (Thermal Performance Assessments) automatically calculate the wall, ceiling/roof and sub/floor Total R-Values so only the Added R-Value of the insulation product is required to be entered.

If the Total R-Values are entered into these software programs instead of the Added R-Values then the Assessment will most likely fail compliance when corrected.