Energy Efficiency Information

POSTED: 03/18/2023

“Energy Efficiency / Thermal performance / Minimum R-Values”

What do these terms mean??

Assuming we are talking about housing, these terms have very specific meanings. Let’s see some examples of them, but first, lets understand what the law in New Zealand says…

First, the overarching legislation covering all building work, is known as “the Building Act 2004”.

The Building Act 2004 states that the Act has thew following purposes:

a) to provide for the regulation of building work, the establishment of a licensing regime for building practitioners, and the setting of performance standards for buildings to ensure that—

(i) people who use buildings can do so safely and without endangering their health; and

(ii) buildings have attributes that contribute appropriately to the health, physical independence, and well-being of the people who use them; and

(iii) people who use a building can escape from the building if it is on fire; and

(iv) buildings are designed, constructed, and able to be used in ways that promote sustainable development,

(b) to promote the accountability of owners, designers, builders, and building consent authorities who have responsibilities for ensuring that building work complies with the building code.

As can be seen, safety, health and fitness for purpose are the three key objectives of the Building Act. Achieving these is by way of compliance with the “Building Code”.

The Building Code sets out the Objective, the Functions and the ‘Performances’ required of all designs, materials and systems used in building work.

So, you might ask, ‘what does the Building Code say about Energy Efficiency / Thermal performance / Minimum R-Values?’

Such matters are covered by ‘Performance Clause H1’.

Clause H1 includes two principal performance requirements:

H1.3.1 – The building envelope enclosing spaces where the temperature or humidity (or both) are modified must be constructed to—

a) provide adequate thermal resistance; and

(b) limit uncontrollable airflow.

No specific performance is described here.

H1.3.2E – Buildings must be constructed to ensure that their building performance index does not exceed 1.55.

There is the criterion. The whole building, irrespective of size or shape. Must meet the “building performance index” – which must not be greater than 1.55.

The building index is calculated using one of several ‘approved calculation methods’.

As can be seen there is no mention of Energy Efficiency / Thermal performance / Minimum R-Values under Building Code Performance Clause H1. So, what do these terms mean?

  1. Energy Efficiency is a somewhat general term used to determine the overall efficiency of the use of energy, or heating or cooling, for a given situation – or building or house. There are many units of measurement available, and none have wide recognition at present.
  • Thermal performance is a technical term, based on a measurement, used to describe how effective a material or system, such as a wall, a roof or a window is, in preventing the loss or transfer of heat. It is particularly useful when comparing one material or one product with another.
  • Minimum R-Values is another term used when measurement figures of thermal performance are used to compare one material or one product with another. For example, the R-Value of insulation product a enable one to compare the performance of another insulation product having a similar or different R-Value.

Therefore it is important not to confuse the requirement of the Building Code with values or terms such as “Energy Efficiency / Thermal performance / Minimum R-Values”.