Glossary Of Terms


Building Envelope

The elements of a building that separate a habitable room from the exterior of a building or a garage or storage area;


Certified thermal calculation software

Software certified by the Board of Agrément South Africa in terms of Agrément South Africa's Energy Software Protocols as being fit for thermal modelling or calculation purposes in terms of these regulations;

Competent Person

A person who is qualified, by virtue of his education, training, experience and contextual knowledge, to make a determination regarding the performance of a building or part thereof in relation to a functional regulation



Non-mandatory requirement, the compliance with which ensures compliance with a functional regulation

See also: Rational Design



Any glazed opening in a building envelope including windows, doors and sky lights

Functional Regulation

Regulation that sets out in qualitative terms what is required of a building or building element or building component in respect of a particular characteristic, without specifying the method of construction, dimensions or materials to be used


Net floor area

This excludes all vertical elements (i.e. walls) and is used to define energy usage and demand per square meter.



The direction a building envelope element faces, i.e. The direction of a vector perpendicular to and pointing away from the surface outside of the element. Additional Key Definitions as per SANS10400XA



The Thermal Resistance of a building element is abbreviated as the R-Value. The R-Value is a physical property of the material or element. The total R-Value is the sum of all component R-Values of the materials, air spaces and surfaces, which go to make up a building element.

Rational Design


Clients are required by law to make their new buildings compliant in terms of Energy Usage and in terms of Regulation XA of the National Building Regulations. Some clients will want to make their buildings energy efficient in order to save energy and money.

Generally if the compliancy exercise is handled by the Architect they will follow a route known as he Prescriptive or Deemed-to-satisfy route. This route is more expensive to implement than the alternative route which is the Rational Design route. This is because the Prescriptive rules are generally more stringent than a route which carefully balances costs against energy savings, and clients will spend extra money on fenestration or insulation, but they will pay the Architect no extra fee for the compliance services.

Clients who want to save money:

For clients wanting the lowest cost of build, a simple compliance report can be prepared for the Local Authority which will change the need for expensive glass windows and doors using an Energy Model and Rational Design.

The building will not have the fenestration and insulation specifications, but it may have a more efficient hot water system or some other measure in place which makes the building nominally more efficient.

Clients who want to save energy:

For clients who wish to save energy and reduce the running costs of their buildings there is an option to require of an Energy Consultant or a suitably experienced Engineer that the specification developed is optimised so that the client is getting value or energy savings out of compliance with the National Building Regulations.

The service which STRUCTATHERM Projects offer, is to optimize the extra expenditure on energy efficiency and guide the clients towards adopting those measures which are cost effective.

Design by a Competent Person involving a process of reasoning and calculation and which may include a design based on the use of a Standard or other suitable document.

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See also: Competent Person

Reference Bulding

A hypothetical building that is used to determine the maximum allowable heating load for the proposed building


Solar Heat Gain Co-efficient

A measure of the heat entering a structure by way of solar radiation. The SHGC is the Shading Co-efficient of the glazing multiplied by 0.87


Total R-Value

The sum of the R-values of the individual component layers in a composite element including the air space and associated surface resistances measured in m2.K/W

See also: R-Value

Total U-Value

The thermal transmittance (W/m2/K) of the composite element including the air space and associated surface emittance

See also: U-Value



This is a measure of the heat energy which will pass through the material or building element when a temperature of one degree K is applied across the element. The total R-Valueis mathematically, the inverse of the Total U-Value which is the Total Thermal Transmittance RT = 1 UT