A Summary of the revised SANS 10400-XA Standard (2021 Edition)

NEWS | Aug 16th, 2022

Part X of the National Building Regulations (NBR) deals with Environmental Sustainability. Part XA specifically deals with Energy Usage in Buildings.

The national standard called SANS 10400 Part XA provides the Deemed to Satisfy (DTS) requirements for compliance with part XA of the NBR. The SANS 10400-XA standard was first issued in 2011. The main energy efficiency items addressed in Part XA are:

  • Insulation of walls and roofs (minimum R-values specified)
  • Solar heat gain and conductance of glazing (fenestration calculations)
  • Energy used for hot water (minimum 50% of hot water to be from non-resistance heating)
  • Energy used for lighting (maximum use and demand specified)

There are three routes to compliance with the XA Regulation:

1. Prescriptive Route:

Compliance with the rules for orientation, shading, services and building envelope as set out in SANS 10400-XA.

2. Performance Route (Rational Design):

Prove that the design’s energy consumption and demand is equivalent or better than the values listed in the tables in SANS 10400-XA.

3. Reference Building Route (Rational Design):

Prove that the theoretical energy consumption and demand of the design is equal to or less than a reference building that complies with the rules given in SANS 10400-XA (i.e. the prescriptive route).

The revised SANS 10400-XA was published in November 2021. Some important changes made to the standard in the 2021 version are listed below. It would be valuable for professionals and contractors in the building industry to take note of this.

Energy Zone Map

The number of zones on the map has been increased from 6 to 8. The areas are now called “Energy Zones” instead of the previous “Climatic Zones.” The new zones are listed as 1 to 7, but zone 5 has a sub-section for high humidity areas on the east coast. Multiple zones can still occur over a single municipality or even suburb. For example, the new map splits the City of Tshwane almost in half. A detailed and very useful map can be viewed on the CSIR website at: https://csir.maps.arcgis.com/apps/webappviewer/index.html?id=79602766e2b54ede82625c939ac1814b.

Energy Zone Map

SANS 204 omitted

The new standard no longer refers to the standard SANS 204: Energy Efficiency in buildings. All required information and minimum functional specifications are included in the XA Standard itself.

Glazing Calculations

The 2011 edition requires fenestration calculations to be done where the glazing to floor area ratio is above 15%. The 2021 edition has increased this threshold to 20%.

The 2021 edition allows for simpler calculations to measure compliance, but it does seem that the general requirements are stricter. Different from the previous version, there now is no distinction drawn between the Solar Heat Gain Coefficient (SHGC) requirements of glazing facing west, north or east.

There is a new restriction on the use of single pane low-E glazing in some areas of the Southern Cape coastal region due to condensation problems.

External walls

The 2011 edition accepted a minimum of 140 thick masonry walls, and 230 collar jointed walls without cavity, as sufficient in all zones. Now 230 brick collar jointed walls (with a minimum R value of 0.4 m²K/W) are accepted as minimum only in zones 3, 5 & 5H. All other zones require 50mm cavity walls with a minimum R value of 0.6 m²K/W.

Roof Insulation Requirements

For some areas the minimum insulation values (R-values) of roof assemblies have increased. All the zones now require an R-value of 3,7 m²K/W, except the High Humidity portion of Zone 5 (e.g. Durban) that requires 2.7 m²K/W. Flexible bulk insulation now requires spacers to eliminate the effects of material compression. 

Building sealing

New requirements are listed for the sealing of the building. This includes a requirement for compressible strips at the edges of external doors. Chimney flues are to have dampers or flaps that can be closed.

Hot water supply

The 2021 version provides more detailed requirements for hot water than the last. A list of accepted alternative energy solutions (e.g. gas, solar, heat pump & biogas) is given as well as their minimum storage vessel requirements per person. For an H4 residence the minimum 24 hour storage per person is 50 liters. For solar geysers in all occupancies, the storage volumes shall be 50% higher.

Lighting

The requirement for residential occupancies H3 (Domestic Residence) and H4 (Dwelling House) has been simplified in that no calculation is necessary if LED lamps are used throughout. It is also a new rule that occupancy and daylight sensors must be installed for all occupancies other than H3 & H4. 

Except for the provision made for LED lamps in H3 and H4, the lighting power density values shall comply with a table showing the different occupancies with corresponding W/m² values. There is however no longer a table for maximum annual consumption to comply with.

Air-conditioning

As with the previous version, there are minimum requirements specified for the efficiency of air-conditioning systems. Different equipment types and their required efficiencies are listed.

A last word…

What are your impressions of the new 10400-XA standard? Please feel free to share your thoughts with me at jb@roosarchitects.co.za

Roos Architects also provides a SANS10400-XA Rational Design service to assist in reaching compliance if the Prescribed Route proves to be unpractical or too costly. Feel free to contact us for a quote or more information.