New regulations in Scotland

The sixth amendment to the Building Standards (Scotland) Regulations came into effect on 4 March 2002. The new Part J, Conservation of Fuel and Power, significantly raises standards of energy efficiency required for new and refurbished buildings.

The Scottish regulations vary significantly from those south of the border and all architects, engineers, contractors and suppliers working in Scotland must familiarise themselves with these to ensure a smooth transition.

The change from the previous regulations that will have the biggest impact on the design of new buildings is the change to thermal performance of the building fabric, referred to in section J8.

Compliance with the new standards can be achieved by three alternative methods: elemental method; heat loss method; and carbon emissions calculation method. Each has its own merits, allowing selection on what best suits the particular needs of any given project.

The elemental method
This is the most restrictive method of compliance, with prescribed U-values given for each building element. Maximum areas of windows, doors and roof lights must also be complied with. The new U-value required for external walls is 0·30 W/m²K which is a significant reduction from the current 0·45 W/m²K and lower than the new Part L (England and Wales) figure of 0·35 W/m²K.

The heat loss method
This method offers compliance if the total heat loss of the proposed building is less than or equal to that from a notional building of the same size and shape with U-values equivalent to the elemental method.

This approach is more flexible than the elemental method as it allows trade-off between elements, eg lower performance glazing systems can be offset by improved wall insulation. However, this method is subject to maximum permissible U-values when trading-off between elements and only offers very limited benefits if areas of glazing, doors or rooflights are traded-off.

Carbon emissions calculation method
This has the greatest flexibility in design as it takes into account all energy conservation design features including building fabric and solar control, as well as the operational efficiency of mechanical, electrical, lighting and controls installations. Compliance is achieved where the total calculated carbon emissions for the proposed building are lower than that of a notional building with U-values equivalent to the elemental method.

In effect, relaxations in terms of a greater percentage of glazed areas or increased U-values of particular elements can be off-set by incorporating other low energy design features such as greater use of thermal mass, solar shading, more energy efficient air conditioning systems and low energy lighting installations.

The calculation of total carbon emission for the proposed building and the notional building requires detailed thermal modelling using building energy and environmental modelling software. The modelling of the various options for improving overall energy performance requires the specific allocation of time and resources in order to achieve the output, which is to satisfy building control officers.

However, committing to this method of compliance gives the architect and the building services engineer more flexibility in design, ensuring that unusual, or innovative buildings can still be built within the constraints of the new regulations.

As with the heat loss method, the carbon emission calculation method is also subject to the maximum permissible U-values.

Cold bridging and infiltration
To address the issues of cold bridging and the limiting of infiltration, the new Part J refers designers to BRE reports. It does, however, stop short of requiring new buildings to be pressure tested.

For some, this may seem like a lost opportunity as specifying an air leakage criteria followed-up with verification through testing, can lead to significant improvements in the airtightness of a building, something not guaranteed by token reference to BRE reports.

Lighting
There have been changes to the sections affecting lighting installations including the requirement for 95% of the installed lighting in new and refurbished buildings to be to a standard of energy efficiency of greater than 65 lumens per circuit-watt.

Low voltage tungsten halogen fittings fall below this threshold, therefore only 5% of the installed lighting as measured in circuit-watts can be low voltage tungsten halogen or equivalent. The only exception to this is display windows in the retail environment.

Carbon performance index
Demonstration of achieving other recognised levels of energy performance is limited to the calculation of carbon performance index (CPI) for offices being equal to or greater than the equivalent Energy Consumption Guide 19 figure of 100 and the calculation of specific fan power in all non-office buildings, with a maximum figure of 1·5 W/litre/s. The calculation of both these will also require the input of the building services engineer.

The new regulations recognise the link between the ongoing energy efficiency of a building and its maintenance management regime. Section J14 sets-out the requirement for building log books which are to be provided to the building occupier on completion which include operation and maintenance instructions as well as forecasted annual energy consumption. Again this will require further input form the engineer.

Conclusion
Those who have read articles on the revisions to the English and Welsh Part L will see that there are significant differences between these and the Scottish Part J. Some of these differences include:

• Lower U-value of 0·3 W/m²K for walls (by elemental method)
  
• No specific reference to limiting solar gains
  
• No reference to DfES or NHS energy efficiency standards for schools or hospitals respectively
  
• No requirement for air leakage testing
  
• Heat loss method rather than whole building method offered as route to compliance
  
• No reference to 'competent persons' to verify submitted calculations
  
• Insulation standard for ductwork, pipes and vessels is the 1990 version of BS 5422 rather than the 2001 version.

In conclusion, the new regulations in Scotland should lead to a decrease in the energy consumption within new and refurbished buildings with the consequential reduction in carbon emissions.

They offer an opportunity for building services engineers to contribute more fully in the development of solutions for building form and fabric to ensure that the new regulations do not overly restrict the architect's options for creating exciting and interesting buildings.