RSP Consulting Engineers

Non-Domestic Guidance

The Building Standards Division of the Scottish Government has released the details of the forthcoming changes to Section 6 of the Scottish Building Regulations.  The changes will come into force on the 1^st of October 2010.  The main changes are summarised in this article.

All new buildings will be required to show (through SBEM calculation methodology) a 30% reduction in CO2 emissions from the 2007 standards.  The SBEM methodology will be revised to include this improvement factor so designers will still simply be demonstrating compliance with the Target Emissions Ration (TER).

The maximum acceptable U-values have been revised for new buildings, extensions and conversions of existing buildings.  The area weighted maximum acceptable values are shown in table 1.

Shell buildings should be designed to achieve a maximum air permeability of 7m³/m².h @ 50Pa.  Testing will be required on completion of the shell and again on completion of the fit out works.  All other buildings should be designed to achieve an air permeability of 10m³/m².h @ 50Pa or less although this is a recommendation only.  Air tightness testing will be required from 1^st May 2011.

Seasonal efficiency requirements for heating systems have been changed and a minimum efficiency has been added for biomass boilers.  Table 2 shows the proposed efficiencies required.

The only revision to the minimum allowable efficiencies of heat pumps is the distinction of those providing heat for domestic hot water and those providing heat for space heating only.  The minimum heating COP for heat pumps for space heating only has increased from 2.0 to 2.2.  The minimum COP required for heat pumps providing domestic hot water remains at 2.0.

There are changes to the minimum thermal efficiencies allowed for gas and oil firing warm air systems and radiant heaters as shown in tables 3 and 4.

There are no changes to the minimum allowable thermal efficiencies for domestic hot water systems. 

CHP QA Quality Index guidance has been clarified to cover systems less than 500kWe but greater than 5kWe.  Micro CHP systems less than 5kWe are dealt with in the Domestic Technical Guidance.  The minimum combined heat and power quality index for all types of CHP should be 105 with a power efficiency greater than 20%.  The CHP unit should operate as the lead heat generator and be sized to supply no less than 45% of the annual heating demand.  CHP may be used as the main or supplementary heat source in community heating or district heating schemes.

Further information has been included in the regulations in respect of circulators and water pumps when used in closed systems.  Circulators up to 2.5kW should have a minimum rating of Band C in respect of energy efficiency, in accordance with the Europump Labelling Scheme.  Variable speed glandless circulators should be used on variable volume systems.  Any water pump rated at more than 750W should be fitted with, or controlled by, an appropriate variable volume system.  On water pump booster sets with an open loop circuit the static head should be checked before an appropriate variable speed controller is used.

The controls package for air to water heat pumps must include defrost control of the external airside heat exchanger. 

Minimum controls packages have been introduced for gas and oil firing warm air systems and radiant heaters.  When radiant heaters are installed in new or existing buildings the controls package should include as a minimum; time control and space temperature control with black bulb sensors. 

When installing gas and oil firing warm air systems in new and existing buildings the controls package must feature, as a minimum; time control, space temperature control and, for buildings with a floor area greater than 150sqm, zone control. 

All other system control package minimum guidelines remain the same as in 2007 standards.

Minimum lighting efficiencies have been included for artificial lighting with the exception of emergency lighting or specialist process lighting such as theatre spotlights and lighting in hospital operating theatres.  The minimum standards for efficacy are shown in table 5.

(1)   Efficacy of not less than 55 luminaire lumens per circuit-watt for installations in existing buildings.  When calculating the average luminaire lumens per circuit-watt, the circuit watts for each luminaire may first be multiplied by the control factors in table 6.

More detailed control requirements have been introduced for general and display lighting.  These are shown in table 7.

The minimum required Energy Efficiency Ratios (EER) of comfort cooling equipment have been updated as detailed in table 8.

There are significant changes to the maximum specific fan powers allowed for air distribution systems and the introduction of limits on the maximum external system pressure drop (Pa).  These are shown in table 9.  The standards proposed for existing buildings are shown in brackets.