Section 2 - Gas-fired space heating and hot water systems

This section provides guidance on the specification of gas-fired space heating and hot water systems in dwellings.

All gas appliances should be installed by a competent person and in accordance with CER Criteria document "THE REGULATION OF GAS INSTALLERS WITH RESPECT TO SAFETY". When the Gas Installers Register is put in place , all installers of gas appliances must be a registered gas installer. The installation should be carried out to the manufacturer’s instructions and should comply with all other relevant parts of the Building Regulations and, for wet systems, local authority guidelines.

2.1 - Scope of guidance

The guidance in this section applies to systems fuelled by natural gas and liquid petroleum gas (LPG); any requirements specific to either fuel type are identified.

The following types of gas-fired heating systems are addressed:

Wet central heating systems.
Range cookers with integral central heating boilers.
Warm air heating systems.
Fixed independent space heating devices.

Where appropriate, it may be necessary to refer to other sections in this guide covering community heating, underfloor heating, heat pumps, solar water heating and micro-CHP.

2.2 - Gas-fired wet central heating systems

This section provides guidance on the specification of gas-fired wet central heating systems for dwellings that, if followed, will satisfy the energy efficiency requirements of the Building Regulations 2008.

Terminology and applicability of guidance to different scenarios in new and existing dwellings

The guidance in this section applies to the following situations:

The specification of central heating systems in new dwellings – this situation is referred to in this section as a new system.
The specification of central heating systems in existing dwellings where previously space heating was not provided by central heating – this situation is also referred to in this section as a new system
The specification of a replacement central heating system and/or component in existing dwellings where central heating is already installed – this situation is referred to in this section as a replacement system.

In situations (a) and (b) above, the guidance for compliance of new systems (in new and existing dwellings) with Part L 2008 is the same.

In situation (c) above, that is for replacement systems in existing dwellings, the guidance for compliance with Part L 2008 is as for new systems, unless otherwise stated in the relevant section.

Gas-fired central heating systems which are provided as new systems or replacement systems in dwellings should meet the following conditions:

The boiler should have a minimum efficiency (as defined by its HARP value) as given in Table 1 (row a).

AND

The minimum provisions for system circulation as given in Table 1 (row b) need to be met.

AND

The minimum provisions for hot water storage and labelling of storage vessels as given in Table 1 (row c) need to be met.

AND

The minimum provisions for system preparation and water treatment as given in Table 1 (row d) should be met.

AND

The system should be commissioned in accordance with the minimum provisions given in Table 1 (row e).
AND
The minimum provisions for boiler interlock, zoning and time control and temperature control of the heating and hot water service circuits as described in Table 2 should be met. An acceptable alternative to these is any boiler management system that delivers the specified zoning, timing and temperature and boiler interlock control provisions. When gas boilers are installed as part of a replacement system, the minimum level of system controls should be provided, as described in Table 2, unless they are already installed and fully operational. If an individual component of the control system is being replaced in an existing system, for example a room thermostat, it is not necessary to upgrade the system to meet the minimum requirements.

AND

Pipework should be insulated as described in Table 3.

Table 1

Table 1

Table 2

Table 2

Table 3

Table 3A

2.3 - Gas-fired range cookers with integral central heating boiler

This section provides guidance on the specification of gas-fired range cookers with integral central heating boilers for space heating and hot water in dwellings.

Gas-fired range cookers with an integral central heating boiler which are provided in new or existing dwellings should meet the following conditions:

The appliance should have two independently controlled burners (one for the cooking function and one for the boiler) and the boiler should have a Seasonal Efficiency (HARP^2^ ) value in excess of 75%.

AND

Information about appliance performance should be included in the commissioning information given at completion. The manufacturer’s declaration of appliance performance and HARP value should include the following words:

Seasonal efficiency (HARP) = xx%
Case heat emission value = yy kW
Heat transfer to water at full load = zz kW

The values are used in the Dwelling Energy Assessment Procedure (DEAP) for the energy rating of dwellings. The test data from which they have been calculated has been certified by {insert name and/or identification of Notified body}.

AND

The minimum provisions for gas-fired central heating systems with respect to the integral central heating boilers as given in Table 1 (rows B–E);

AND

The minimum provisions for boiler interlock, zoning and time control and temperature control of the heating and hot water circuits with respect to the integral central heating boilers as given in Table 2 for gas-fired central heating systems. An acceptable alternative to these is any boiler management system that delivers the specified zoning, timing and temperature provisions. When gas boilers are installed as a replacement for existing boilers, the minimum level of system controls should be provided, as described in Table 2, unless they are already installed and fully operational. If an individual component of the control system is being replaced in an existing system, for example a room thermostat, it is no necessary to upgrade the system to meet the minimum requirements;

AND

Pipework should be insulated as described in Table 3.

2 Seasonal Efficiencies for appliances can be found in HARP database and in the national methodology for Building Energy Rating (DEAP) at http://www.sei.ie/HARP and http://www.sei.ie/DEAP

2.4 - Gas-fired warm air heating

This section provides guidance on the specification of gas-fired warm air heating systems for dwellings.

Terminology and applicability of guidance to different scenarios in new and existing dwellings

The guidance in this section applies to the following situations:

a. The specification of gas-fired warm air heating systems in new dwellings – this situation is referred to in this section as a new system.

b. The specification of gas-fired warm air heating systems in existing dwellings where previously space heating was not provided by a warm air system – this situation is also referred to in this section as a
new system;

c. The specification of a replacement warm air heating system and/or component in existing dwellings where warm air heating is already installed – this situation is referred to in this section as a replacement system.

Gas-fired warm air heating which is provided as a new system or replacement system in new or existing dwellings should meet the following conditions:

The minimum provisions for efficiency and installation set out in Table 4;

AND

The minimum provisions for system control set out in Table

Table 4

Table 4A

Table 5

Table 5A

2.5 - Gas-fired fixed independent space heating appliances

This section provides guidance on the specification of gas-fired fixed independent space heating appliances for dwellings. Fixed independent space heating appliances may be installed as a means of primary or secondary space heating.

Gas-fired fixed independent appliances for primary-space heating

Gas-fired fixed independent space heating appliances in new and existing dwellings which are provided as the primary heat source should meet the following conditions:

The appliance should be one of the types described in Table 6

AND

The efficiency of the appliance (gross calorific value) should be no less than 58%. The appliance manufacturer’s declaration of appliance performance shall include the following words:

“The efficiency of this appliance has been measured as specified in {insert appropriate entry from Table 6} and the result is [x]%. The gross calorific value of the fuel has been used for this efficiency calculation. The test data from which it has been calculated has been certified by {insert name and/or identification of Notified Body}. The efficiency value may be used in the Dwelling Energy Assessment Procedure (DEAP) for energy rating of dwellings.”

AND

In new dwellings each appliance should be capable, either independently or in conjunction with room thermostats or other suitable temperature sensing devices, of controlling the temperatures independently in areas that have different heating needs (e.g. separate sleeping and living areas). In existing dwellings, wherever practical, temperature controls should be upgraded to the standards required for new dwellings.

Gas-fired fixed independent appliances for secondary-space heating

Gas-fired fixed independent space heating appliances which are provided as the secondary heat source in new or existing dwellings should meet both of the following conditions:

The appliance should be one of the types described in Table 7.

AND

The efficiency (gross calorific value) of the appliance should be no less than the value in Table 7 for that type of appliance. The appliance manufacturer’s declaration of appliance performance shall include the following words:

“The efficiency of this appliance has been measured as specified in {insert appropriate entry from Table 7} and the result is [x]%. The gross calorific value of the fuel has been used for this efficiency calculation. The test data from which it has been calculated has been certified by {insert name and/or identification of Notified Body}. The efficiency value may be used in the Dwelling Energy Assessment Procedure (DEAP) for energy rating of dwellings.

Table 6

Table 6A

Table 7

Table 7A

2.6 - Gas-fired fixed decorative fuel-effect fires

This type of appliance is intended for decorative purposes and therefore a minimum thermal efficiency is not specified. Note that, for the purposes of DEAP, the efficiency of decorative fuel-effect fires is classed as 20% for use in the space heating requirement calculation; see Table 4a of DEAP 2008.

In order to comply with the requirements of Part L 2008, gas-fired decorative fires in new and existing dwellings should meet the following conditions:

The appliance should meet the product standards specified in IS EN 509:2000 Decorative fuel-effect gas appliances.

AND

No more than one appliance should be installed per 100m^2^ of dwelling floor area.

2.7 - Gas-fire for secondary-space heating provided as part of a combined fire and back boiler unit

A combined fire and back boiler unit can only be installed as a replacement for an existing combined fire and back boiler unit, and then only when the criteria of the Condensing Boiler Installation Assessment procedure are satisfied as outlined in Appendix A of this document. In order to comply with the requirements of the Building Regulations 2008, the gas fire provided as a secondary heat source as part of a combined fire and back boiler unit, when provided as a replacement system in existing dwellings, should meet the following conditions:

The appliance should be one of the types described in Table 8. The manufacturer’s declaration of appliance performance shall include the following words:

“The efficiency of this appliance has been measured as specified in {insert appropriate entry from Table 8} and the result is [x]%. The gross calorific value of the fuel has been used for this efficiency calculation. The test data from which it has been calculated has been certified by {insert name and/or identification of Notified Body}. The efficiency value may be used in the Dwelling Energy Assessment Procedure (DEAP) for energy rating of dwellings.”

AND

The efficiency of the appliance (gross calorific value) should be no less than the value in Table 8 for that type of appliance.

Table 8

Table 8A

Supplementary information – further guidance on gas-fired heating

Further guidance on gas-fired heating systems is available in the following publications:

Energy Efficiency Best Practice in Housing publications:

CE30 Domestic heating by gas: boiler systems;
CE51 Central heating system specifications (CHeSS);
CE54 Whole house boiler sizing method for houses and flats.

CORGI publications:

Essential Gas Safety (GID1);
Gas Cookers and Ranges (GID2);
Gas Fires and Space Heaters (GID3);
Water Heaters (GID5); • Central Heating – wet and dry (GID7);
Wet Central Heating System Design Guide (WCH1);
Warm Air Heating System Design Guide (WAH1).

Requirements relating to various aspects of the installation of condensing boilers are given in IS EN 813 , British Standards, BS 5440 Parts 1 and 2, BS 5449 and BS 6798.

2. Gas-fired space heating and hot water systems