You are here: 12.0 Pollution > Pol 02 NOx emissions

Pol 02 NOx emissions

Number of credits available Minimum standards

Building type dependent

No

Aim

To encourage the supply of heat from a system that minimises NOx emissions, and therefore reduces pollution of the local environment.

Assessment Criteria

The following is required to demonstrate compliance:

  1. Where the plant installed to meet the building’s delivered heating demand has, under normal operating conditions, a dry NOx emission level (measured at 0% excessO2) as follows:

Building types and emission levels

Credits
Court, office, retail and other building types

100 mg/kWh (space heating )

1 credit

70 mg/kWh (space heating)

2 credits

40 mg/kWh (space heating)

3 credits
Education, healthcare, multi-residential, prison building types
100 mg/kWh (space heating ) 1 credit
70 mg/kWh (space heating ) 2 credits

40 mg/kWh (space heating )
100 mg/kWh (water heating)

3 credits
Industrial buildings
Office and associated areas 70 mg/kWh (space heating ) 1 credit
Operational areas 70 mg/kWh (space heating ) 1 credit
  1. Report via the BREEAM scoring and reporting tool the direct and indirect NOx emissions in mg/kWh and energy consumption in kWh/m2/yr from meeting the building's heating, cooling and hot water demands.

Compliance Notes

Ref

Terms

Description

CN1 

New build extensions to existing buildings If the heating demand for the new extension is being met by an existing system, then the NOx emission level for the existing system must be assessed against the criteria of this issue.

CN2 

Shell only

Where the specification and installation of heating systems within tenanted units/areas will be the responsibility of the future tenant, compliance with this BREEAM issue can be demonstrated via one of the following means in shell only buildings/areas:

  1. Option 1 – Use of a tenancy lease agreement between the developer and tenant/s (full value of available credits)
  2. Option 2 – A Green Building Guide for tenant fit outs (half the value of the available credits)
  3. Option 3 – Developer/Tenant collaboration (full value of available credits)

Refer to Appendix D – BREEAM New Construction and shell and core/speculative assessments of this Scheme Document for further description of the above options.

CN3 

Multi-residential developments with CSH assessed dwellings

For buildings with self-contained dwellings also being assessed under the Code for Sustainable Homes (CSH), the following applies:

If the heating/cooling/hot water system, and therefore NOx emissions, used to demonstrate compliance in the CSH assessment for the self contained dwellings, is of the same specification as that used to provide heating for the other residential/communal areas of the building, the credits achieved, and information demonstrating compliance for CSH issue Pol 2 can be used for the purpose of the assessment and compliance of BREEAM issue Pol 02.

If separate systems are used, then data/information from the CSH assessment can be used in part to demonstrate compliance. To demonstrate full compliance the NOx emissions from the heating system used to serve the parts of the building not falling within the scope of the CSH assessment will need to be factored in to the assessment.

CN4 

Industrial buildings, no office area Where the assessed building is designed without an office area, the first credit does not apply. One credit is therefore available where compliance with the operational area benchmark is met. Where there is no office area and no heating in the operational area, this issue does not require assessment.

CN5 

Untreated operational area in industrial buildings Where the operational area of the assessed building is designed to be untreated, the second credit does not apply. One credit is therefore available where compliance with the office area benchmark is met. Where there is no office area and no heating in the operational area, this issue does not require assessment.

CN6 

Highly insulated building Where the heating load for a highly insulated building is less than or equal to 7% of the heat load for a Building Regulations compliant building of the same size and type, one credit can be awarded regardless of the NOx emission level. Figures used for calculations of the percentage of total heat demand must be based on the output from approved energy modelling software.

CN7 

NOx data provided in different units Where NOx data is provided in different units or at a level of excess oxygen greater than zero, the manufacturer/supplier will need to be asked to convert this to comply with the BREEAM criteria. Alternatively, the assessor may adjust the figure using the relevant correction factors provided in the Additional Information section.

CN8 

Grid electricity Where electricity used by the heating system is sourced from a zero emission renewable source such as PVs, wind etc, there are no resulting emissions. This source of heating can therefore be counted as having zero NOx emissions.

CN9 

Heat pumps Heat pumps powered by grid electricity are likely to indirectly produce emission rates higher than those required by BREEAM and are therefore typically unable to achieve any credits under this issue. However, there is a formula for determining NOx emissions from heat pumps in the Additional Information section below. Please note, the energy saved by using certain types of heat pumps is recognised in BREEAM issue Ene 01 and Ene 04.

CN10 

District heating District heating systems that incinerate waste usually have NOx emission rates higher than the levels set to achieve any BREEAM credits.

CN11 

Heat recovery Heat recovery can be considered as having zero NOx emissions for the purpose of this issue.

CN12 

Open flues No credits may be awarded for open flue heating or hot water systems.

CN13 

Combined Heat & Power Refer to the additional guidance section for guidance on calculating NOx emission levels from CHP.

CN14 

Biomass Biomass systems are recognised as reducing the impact of fossil fuel depletion, by employing a renewable fuel source (provided it is sustainably sourced). However, biomass can produce a significant amount of NOx and so may not achieve this credit. They may, however, gain recognition in the energy section of BREEAM.

CN15 

Water heating benchmark and point of use heaters

The benchmark requirement for water heating is intended to apply only to buildings with a large demand for hot water (and therefore a substantial proportion of NOx emissions resulting from hot water heating).

Where building types required to assess NOx emissions from water heating do not have a large demand for hot water and as a result they are installing point-of-use electric hot water heaters only (grid sourced electricity), such installations may be exempt from the water heating NOx emissions requirement. This is on the provision that the design team (M&E engineer) confirm that energy demand for electric hot water heating is less than 10% of total energy demand for space and hot water heating.

CN16 

More than one heating system Where more than one heating system is specified refer to the Additional Information section for guidance on calculating NOx emission levels.

CN17 

Green Tariff Commitments to use a Green tariff to supply electricity to heat the building or power heat pumps are not recognised in this issue due to the uncertainty that this electricity will be zero emission.

CN18 

Assessment and reporting of a buildings NOx emissions from cooling

At present the Pol02 issue does not benchmark and award credits for NOx emission levels associated with a buildings cooling demands. To facilitate possible future benchmarking of this kind and alignment with European Standards on the Sustainability of Construction Works, BREEAM does require, as a condition of achieving any credits for this issue, the reporting of both direct and indirect NOx emissions resulting from meeting the buildings heating, cooling and hot water demands.

In the case of indirect emissions, this refers primarily to emissions associated with grid electricity, where grid electricity is a/the source of energy for the building's heating, cooling and/or hot water demands. Direct NOx emissions are those resulting from the burning of fuel on site or in the assessed building to meet heating, cooling and/or hot water demands, for example via a gas/oil fired/biomass boiler.

CN19 

Other building type: Residential institutions When assessing a building defined by the scope of BREEAM as an 'Other - Residential Institution', apply the NOx emission benchmarks for a multi-residential building type (and not the 'other building type' benchmarks). This guidance applies in particular to hotels, hostels, boarding and guest houses, secure training center, residential training center.

Schedule of Evidence

Ref Design stage
Post-construction stage
All

Relevant section/clauses of the building specification or contract.

Manufacturer's product details.

Calculations from the project team.

Where relevant for multi residential buildings:

Evidence in line with the Design Stage evidence requirements of the CSH Issue Pol 2

OR

A copy of the Design Stage CSH certificate and report from the CSH online reporting system confirming the number of credits achieved for CSH Issue Pol 2.

Confirmation from the project team that there have been no changes to the specification and updated calculations where necessary.

BREEAM Assessor’s site inspection report and photographic evidence

 

Where relevant for multi-residential buildings:

Evidence in line with the Post Construction Stage evidence requirements of the CSH Issue Pol 2.

OR

A copy of the Post Construction Stage CSH certificate and report from the CSH online reporting system confirming the number of credits achieved for CSH Issue Pol 2.

Additional Information

Relevant definitions

Approved energy modelling software
Refer to BREEAM issue Ene 01 Reduction of emissions.
Appropriate statutory body
Refer to the definition in credit LE 02 Ecological value of site and protection of ecological features.
NOx emissions
NOx emissions are pollutant gases produced by the combustion of fossil fuels. NOx reacts with heat and sunlight to produce ozone that can cause serious respiratory problems. It also reacts with water to produce acid rain which has a detrimental effect on ecosystems.
Dry NOxLevels
The NOx emissions (mg/kWh) resulting from the combustion of a fuel at 0% excess oxygen levels.
Conversion factors
Manufacturers should be asked to supply dry NOx emissions data in mg/kWh. Where this is not possible the assessor may use the following conversion factors to convert figures in ppm, mg/MJ, mg/m3 or wet NOx.
It should be noted that these conversion factors assume worst case efficiencies and are likely to give conservative answers. This could have the effect of lowering the number of credits achieved.
    1. Figures in mg/m3 should be multiplied by 0.857 in order to gain emissions in mg/kWh. A conversion may also be necessary for data not calculated at 0% excess oxygen (see below).
      Figures in parts per million (ppm) should be multiplied by 1.76 in order to obtain mg/kWh. A conversion may also be necessary for data not calculated at 0% excess oxygen. (see below)
      Figures in mg/MJ should be multiplied by 3.6 in order to show emissions in mg/kWh (1 kWh = 3.6 MJ). A conversion may also be necessary for data not calculated at 0% excess oxygen (below).
      This Issue’s criteria are based on dry NOx values – almost all manufacturers will quote emissions in dry NOx. However if wet NOx figures are supplied, these should be converted to dry NOx. This can be done by multiplying the wet NOx figure by 1.75.
  • Excess Oxygen Correction
    If a NOx emission rate is quoted by the manufacturer in mg/m3 or ppm, then it should be established at what % excess oxygen this emission was measured. The greater the amount of excess oxygen in the flue gases at the time of measurement, the more “diluted” the NOx. It is therefore important to convert any emission rate back to 0% excess oxygen. For the purpose of BREEAM, the following conversion factors can be used for the most frequently used rates supplied by manufacturers:
    % Excess O2 Conversion (c)
    3% x 1.17
    6% x 1.40
    15% x 3.54

    Conversion factor c = 20.9/(20.9 – x)

    Where x = % excess O2 (NOT excess air) and 20.9 is the percentage of O2 in the air.

    Checklists and Tables

    None

    Calculation procedures

    Calculating NOx emission levels from Combined Heat & Power (CHP) systems

    Where CHP systems are specified, it is only necessary to consider the heat related NOx emissions for the assessment of this issue.

    NOx emissions are allocated to heat and electricity in line with the respective power outputs. A NOx emission rate equivalent to the current rate for grid electricity should be assumed for the electrical output (i.e.750 mg/kWh supplied), and the remaining NOx should be allocated to the heat output. Only the heat-related component is then compared with the benchmark scale. The following formula should be used to determine this:

    X = (A - B)/C

    Where:

    Term Description
    X NOx emissions per unit of heat supplied (mg/kWh heat)
    A NOx emissions per unit of electricity generated (mg/kWhelec) i.e. the NOx emitted by the CHP system per unit of electricity generated. This figure should be obtained from the installer/supplier of the system
    B NOx emissions per unit of electricity supplied from the grid (mg/kWhelec) this should be assumed to be 750mg/kWh
    C Heat to Electricity Ratio of the CHP scheme

    The above methodology determines the net NOx emissions from CHP-generated electricity compared with central generation of electricity and allocates this amount to the heat production. Where x is calculated to be negative, it should be assumed to be zero.

    Calculating the average NOx emission levels from multiple systems

    Where the CHP or other heating system type operates in conjunction with another system, an average NOx emission rate should be used based on the ratio of power outputs from each source, i.e. multiply the emissions of each system by the percentage of heat demand it supplies and total these values.

    This is likely to be the case where a CHP system has been sized on the base power demand rather than the heat demand and therefore a secondary heating system is required.

    The following formula can be used for such cases:

    Contributing NOx emmisions from a heat pump formula

    Where:

    Term Description

    N1

     

    NOx emissions rate for source 1
    N2

     

    NOx emissions rate for source 2

    Nn

     

    NOx emissions rate for source n
    HT

    Total heat output from all sources

     

    H1

    Heat output from source 1

     

    H2

    Heat output from source 2

     

    Hn

    Heat output from source n

     

    Calculating NOx emission levels from heat pumps

    For the purpose of assessing this BREEAM issue, either of the formulas below can be used to determine the contributing NOx emissions from a heat pump:

    Formula to determine the contributing NOx emissions from a heat pump

    Where:

    Term Description
    MHeat NOxemission per unit of heat generated in mg/kWhHeat

     

    MElec NOx emissions from UK grid electricity mg/kWh, this should be assumed to be 750mg/kWhElec
    WElect Total quantity of electricity consumed by heat pump kWhElec

     

    WHeat

    Total quantity of heat or coolth produced by heat pump kWhHeat
    EER Energy Efficiency Ratio (also referred to as Co-efficient of Performance)

    Other information

    None

     

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