Pol02 - NOx emissions – Above Green

(2 credits available)

Aim

To contribute to a reduction in national NOx emission levels through the use of low emission heat sources in the building.

Assessment criteria

The following is required to demonstrate compliance:

Two credits (All building types other than Industrial)

Where the plant installed to meet the building's delivered heating and hot water demand has, under normal operating conditions, a NOx emission level (measured on a dry basis at 0% excess O₂) as follows:

NOx Emission levels for heating and hot water (mg/kWh)	Credits
≤ 56 mg/kWh	1 credit
≤ 40 mg/kWh	2 credits
Note for residential developments: Each self-contained dwelling must meet the requirements.

Two credits (Industrial building types only)

NOx Emission levels for heating and hot water (mg/kWh)	Credits
Office and associated areas ≤ 56 mg/kWh	1 credit
Operational areas ≤ 56 mg/kWh	1 credit

Report via the BREEAM scoring and reporting tool the direct and indirect NOx emissions in mg/kWh and energy consumption in kWh/m²/yr arising from systems installed to meet the building's space heating, cooling and hot water demands.

Checklists and tables

None.

Compliance notes

Ref	Terms	Description
Shell and core (non-residential and residential institutions only)
CN1	Applicable assessment criteria	Shell only: This issue is not applicable. Shell and core: All criteria relevant to the building type and function apply. Refer to Appendix D – Shell and core project assessments for a more detailed description of the shell and core assessment options.
Residential - Partially fitted & Fully fitted
CN2	Applicable Assessment criteria - Single and multiple dwellings	Both options: All criteria relevant to the building type and function apply. Refer to Appendix E – Applicability of BREEAM New Construction to single and multiple dwellings, partially and fully fitted for a more detailed description of residential assessment options.
General
CN3	New build extensions to existing buildings	If the heating/hot water 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.
CN3.1	NOx data provided in different units	Where NOx data are provided in different units or at a level of excess oxygen greater than zero, the manufacturer or supplier must 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 Methodology. Where combined heat and power (CHP) systems are used, these conversion factors cannot be used and the information must be obtained from the system manufacturer.
CN3.2	Grid electricity	Heating systems powered by grid electricity can be considered to have zero NOx emissions. If all heating in the building is provided by grid electricity the credits can be awarded by default. The reason for this is based on the aim of this issue, which is to improve local air quality. Where grid electricity is used to supply a heating system, the NOx emissions for grid electricity should be determined from actual data or using default NOx values. Table 58 can be used to identify appropriate default NOx figures for a range of countries or refer to the Approved Standards and Weightings List (ASWL)in the approved standards and weightings list, where more specific values are available for a number of countries. Where a default is not provided for the country of assessment, the fuel mix for the country of assessment should be provided to BRE Global to determine the appropriate default figure. However, please note that default factors are likely to represent a worst case scenario and actual emissions should be used wherever possible, determined by using robust data from a local, national authority or agency. All such data should be provided to BRE Global for verification prior to use within an assessment.
CN3.3	Low NOx grid electricity	Where heating is provided by grid electricity and the project assessed is located in a country where the emissions level of the national grid electricity is less than the levels required by BREEAM, then the credits can be awarded accordingly. Where the NOx emissions level is already less than 40mg/kWh, all three credits can be awarded by default.
CN3.4	Electricity from a renewable source	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.
CN3.5	Combined heat and power	Refer to Additional information for guidance on calculating NOx emission levels from CHP.
CN3.6	Heat recovery	Heat recovery can be considered as having zero NOx emissions for the purpose of this issue.
CN3.7	Open flues	No credits may be awarded for open flue heating or hot water systems.
CN3.8	Water heating benchmark and point of use heaters	Where the water heating can be demonstrated to be less than 10% of the building's total energy consumption, these credits can be awarded based solely on the NOx emissions from space heating.
CN3.9	More than one heating system	Where more than one heating system is specified refer to Additional information for guidance on calculating emission levels.
CN3.10	Assessment and reporting of a building's NOx emissions from cooling	At present the Pol 02 issue does not benchmark and award credits for NOx emission levels associated with a building's 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 building's 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 source of energy for the building's heating, cooling 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 or hot water demands, for example via a gas, oil-fired or biomass boiler.
Building type specific
CN4	Industrial Office or operational areas not present	First credit 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. Second credit 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 is not assessed.
CN4.1	Residential buildings: Secondary water or space heating systems	If a secondary space or water heating system supplies less than 8% of the dwelling’s combined space heating and hot water demand, it can be omitted from the assessment. However, including a low NOx heating system that supplies less than 8% of the combined demand can lower the average NOx figure. Where this is the case inclusion of the secondary system is at the discretion of the developer and assessor.
CN4.2	Residential buildings: Post-construction stage exceptions	Where communal heating systems intended to supply a dwelling under assessment are due to be commissioned within a reasonable period following completion of an individual dwelling, then they should be the heat energy source assessed under this issue for NOx, rather than the interim heat energy supply measure (which should also be noted). The communal system (e.g. CHP, district heating, etc.) must be the intended primary heating energy source for the dwelling. Evidence to confirm that future commissioning of such plant will occur within a reasonable period must be provided in the form of developer commitments and other pertinent technical documentation such as local service strategies; this reasonable period might be up to 18 months from completion of the dwelling.

Methodology

Calculating NOx emission levels from combined heat and 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.

The NOx emissions associated with heat generation should be calculated using the following formula:

Emissions associated with heat generation

Where:

Term	Description
X	NOx emissions per unit of heat generated (mg/kWh heat).
A	NOx emissions per unit of fuel input (mg/kWh fuel input).
B	Heat output (kW).
C	Electrical output (kW).

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 power output from each source, i.e. multiply the emissions of each system by the percentage of heat demand it supplies and total these values.

Where there are multiple sources of heat generation, an average NOx emission rate should be calculated based on the ratio of heat output (kW) from each heat source.

The following formula can be used for such cases:

Contributing NOx emissions from a heat pump formula

Where:

Term	Description
	Average NOx
N₁	NOx emissions rate for source 1
N₂	NOx emissions rate for source 2
N_n	NOx emissions rate for source n
H_T	Total rated power output from all sources
H₁	Rated power output from source 1
H₂	Rated power output from source 2
H_n	Rated power output from source n

Table 58Default factors: NOx Emissions from Grid Electricity

Country list	Default NOx Emission
Austria, Belgium, Denmark, Finland, France, Iceland, Italy, Japan, Kazakhstan, Latvia, Monaco, Netherlands, Norway, Sweden	250 mg/kWh
Canada, Croatia, Germany, Hungary, Ireland, Liechtenstein, Lithuania, Portugal, Slovakia, Slovenia, Switzerland, USA	650 mg/kWh
Czech Republic, Estonia, New Zealand, Romania, Spain,	950 mg/kWh
Australia, Belarus, Bulgaria, Greece, Poland, Russian Federation, Turkey, Ukraine	2,500 mg/kWh

Evidence

Criteria

Interim design stage

Final post construction stage

All

Relevant section or clauses of the building specification or contract. Manufacturer's product details. Calculations.

As design stage.

report and photographic evidence.

Additional information

Relevant definitions

Approved building energy calculation software: Refer to BREEAM issue
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. For the purposes of BREEAM, NOx emission levels are required in units of mg/kWh, measured on a dry basis at 0% excess oxygen levels.

Conversion factors

Manufacturers should be asked to supply NOx emissions data in mg/kWh, measured on a dry basis. Where this is not possible the assessor may use the following conversion factors to convert figures in parts per million (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. Note that these conversion factors are not applicable where combined heat and power (CHP) systems are being used. Please see the calculation procedures below for further details on assessing CHP systems for this issue.

Figures in mg/m³ should be multiplied by 0.859 in order to convert emissions into mg/kWh1. A conversion may also be necessary for data not calculated at 0% excess oxygen.
Figures in ppm should be multiplied by 1.76 in order to convert emissions into mg/kWh. A conversion may also be necessary for data not calculated at 0% excess oxygen.
Figures in mg/MJ should be multiplied by 3.6 in order to convert emissions into mg/kWh (1 kWh = 3.6 MJ). A conversion may also be necessary for data not calculated at 0% excess oxygen.

Wet NOx conversion factor

This issue's criteria are based on dry NOx values; almost all manufacturers will quote emissions measured on a dry basis. However, if wet NOx figures are supplied, these will need to be converted to dry. The following formula should be used to determine the wet NOx conversion factor2:

Conversion factor c = 100/(100-y)

Where y is the % water vapour content measured in the gas. This figure should be obtained from the manufacturer.

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 percentage 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 emissions. 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:

Table 59 Excess oxygen conversion factors

% 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.

Other information

Some systems may find it difficult to achieve credits in this issue, including:

District heating

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

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.