by Ofentse Sefolo

The application of the South African National Building Regulations SANS 10400-XA: 2011 Energy usage in buildings, is in the process of being replaced with a revised version introducing tighter requirements of the energy performance components of building standards for public, commercial and residential building sectors.

Most importantly, the climatic zone map in the revision of SANS 10400-XA, has been replaced with the Energy Zone Map developed by the CSIR. The map indicates graphically the areas and boundaries of the 7 energy zones throughout South Africa.

The energy zones were determined by the amount of heating and cooling energy required to bring the internal temperatures of buildings into thermal comfort levels. The legend on the map indicates the level of heating and cooling energy needed in accordance with the Energy Zone is as follows:

a) Zone 1 = Medium heating and medium cooling
b) Zone 2 = Medium heating and low cooling energy
c) Zone 3 = Low heating and high cooling energy
d) Zone 4 = Low heating and low cooling energy
e) Zone 5 = Low heating and medium cooling energy (Zone 5H – 85% humidity area)
f) Zone 6 = High heating and low cooling energy
g) Zone 7 = High heating and medium cooling energy

The first step in determining compliance with the energy efficiency regulations is to identify the energy zone for the building location. This is done by referring to the energy zone map or to the energy zone tables. Zone 5H high humidity to be taken into account.

Mandatory compliance applicable to buildings

All new buildings and extensions in the following building occupancy classes:

Revised levels of thermal resistance (R-Value) required for insulation in buildings

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.

All tiled roofs shall have a tile underlay or radiant barrier to minimize air infiltration.

Principles of insulation

Resistance to heat flow is achieved by the use of either bulk insulation, reflective insulation or a combination of both, which works in different ways.

How does insulation work?

An uninsulated home is subject to considerable winter heat losses and summer heat gains.

The term “insulation” refers to materials or a combination thereof that provide resistance to heat flow.

When these materials are installed in the roofs, ceilings, walls and floors of a building, heat flow into and out of the building is reduced, and the need for heating and cooling is minimised.

Although ceilings and walls may be insulated, heat loss will still occur in the winter if there are large areas of unprotected glass or through fixed wall vents, gaps at electric light entry points and cracks around external doors and windows.

Appropriate internal window coverings (e.g. lined drapes with pelmets) and draughtproofing are vital to complement insulation. Insulation should always be coupled with the appropriate shading of windows and adequate ventilation in the summer. Without shading, radiant heat entering the home through the windows will be trapped inside by the insulation and cause discomfort.

Certain types of insulation can assist with weatherproofing and control moisture problems such as condensation. Some types of insulation also have soundproofing qualities, with others offering environmentally friendly properties as they contain recycled material.

While insulation should ideally be installed during the construction phase of a building, it can be retrofitted. More recently passive design techniques are prescribed for use in conjunction with insulation.

How insulation performance is measured

The thermal performance of all components and systems, except windows and doors, is expressed in terms of the thermal resistance (R-value). For windows and doors, the performance is expressed in terms of the thermal transmittance (U-value).

Key considerations before installing insulation

There are various factors to consider before making an insulation decision:

• Fire safety: In accordance with the application of the South African National Building Regulations SANS 10400 Part T Fire Protection, the fire performance classification of insulation products is required. When any insulation is tested in accordance with SANS 10177-5 and found to be combustible, the material shall be acceptable if further tested, classified, marked and installed in accordance with the requirements of SANS 428 and the allowable building occupancy classes as specified.

• Thermal performance – Installed R-value: When insulating a home or building, it is important to ascertain the R-value specified by the application of the South African National Building Regulations, SANS 10400-XA Energy usage in buildings. There are various types of thermal insulation products available and the minimum added intervention R-value of insulation products are different. Ensure test reports are available from manufacturers to validate the thermal performance of products.

• Lifetime performance: In order to ensure the expected energy savings, it is important that the insulation does not deteriorate or settle over time. The thermal performance is dependent on the material thickness, blowing agent, density, age, operating temperature and moisture. Install in accordance with the manufacturer’s installation specifications.

• Moisture: Insulation will lose its insulating efficiency or R-value when exposed to moisture. Some insulation products are not absorbent and, if exposed to moisture, will not wick up or hold water. If allowed to dry out, insulation may retain its original R-value. In wall applications certain insulation materials may be applied as vapour retarders or moisture barriers.

• Air infiltration: This generally occurs in the areas of a home that are not correctly sealed or insulated, such as around windows, doors, fireplaces, HVAC ductwork and perimeter joints. It can, and should, be controlled with proper caulking and the sealing of band joists, sill plates and header plates, and around doors, windows, electrical outlets and other openings.

• Environmental benefits: In assessing the environmental characteristics of insulation materials, consideration must be given to a broad range of issues relating to the resources going into their production, manufacturing processes, pollutants given off during their lifecycle, durability, recyclability and impact on indoor air quality. Recycled content is the most recognised environmental feature of building products.

• Lifecycle analysis: An appraisal of the environmental impacts connected with a product through an examination of the product’s environmental traits during many stages including pre-manufacturing, manufacturing, distribution/packaging, use, reuse, maintenance and waste management. In reviewing each of these stages, a lifecycle evaluation clearly shows its environmentally beneficial attributes.

Our sincere thanks and appreciation to the Thermal Insulation Products and Systems Association of South Africa (TIPSASA) for the use of the information contained in this article. For more information, please visit www.tipsasa.co.za.

Main photo courtesy of Knauf Insulation

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