Pol 02 Local Air Quality | BREEAM UK New Construction 2018

Pol 02 offers up to 3 credits for developments that minimise nitrogen oxide emissions through low-emission heating systems. Whilst this might seem straightforward—simply specify better boilers—these credits make a significant difference to overall BREEAM ratings and often represent the most cost-effective credits available in the Pollution category.

Air quality affects public health more severely than many environmental impacts. Poor air quality contributes to respiratory disease, cardiovascular problems, and premature death, particularly in urban areas where developments concentrate. BREEAM Pol 02 recognises developments that reduce their contribution to this problem through sensible heating system specification.

This credit appears in BREEAM UK New Construction 2018 across all building types, with slight variations for industrial buildings where only office and welfare areas require assessment. With straightforward specification changes costing as little as £100-200 per boiler whilst securing 3 credits, Pol 02 represents excellent value for BREEAM projects.

What is BREEAM Pol 02?

Pol 02 focuses specifically on nitrogen oxide (NOx) emissions from heating and hot water systems. NOx gases react with sunlight to produce ground-level ozone, causing respiratory problems. They also react with water to form acid rain, damaging ecosystems. Combustion of fossil fuels—gas, oil, biomass—produces NOx emissions in varying quantities depending on burner technology and combustion efficiency.

The credit structure rewards progressively lower emission levels through three tiers, recognising that heating technology has advanced significantly. Modern condensing boilers with sophisticated burner controls can achieve dramatically lower emissions than older systems, often with minimal cost premium.

Three-tier structure:

• 1 credit: NOx ≤100 mg/kWh (NOx Class 4 certification)

• 2 credits: NOx ≤70 mg/kWh (NOx Class 5 certification)

• 3 credits: NOx ≤40 mg/kWh (NOx Class 6 certification)

All measurements are taken on a dry basis at 0% excess oxygen, following Ecodesign Directive 2009/125/EC labelling requirements. This standardisation ensures fair comparison between different manufacturers' products.

Non-combustion heating systems—heat pumps, electric heating, district heating from low-emission plant—achieve maximum credits by default as they produce zero direct emissions at the building. This doesn't mean they have zero environmental impact (electricity generation produces emissions), but BREEAM assesses direct building emissions under Pol 02.

Pol 02 Requirements for UK New Construction 2018

Credit Thresholds and Heating System Performance

One Credit - NOx Class 4 (≤100 mg/kWh)

Standard modern condensing gas boilers typically meet this threshold without special specification. Most boilers manufactured in the last 10 years achieve NOx Class 4 certification, as this aligns with Building Regulations requirements for efficiency.

Heating systems meeting this threshold include:

• Standard condensing gas boilers from major manufacturers

• Modern oil boilers with appropriate emission controls

• Some combined heat and power systems with emission management

Cost implications are minimal—this represents baseline modern specification. You're not paying a premium for Class 4; you're simply avoiding obsolete high-emission equipment.

Two Credits - NOx Class 5 (≤70 mg/kWh)

Low-NOx condensing boilers achieve this through improved burner technology—typically premix modulating burners that mix gas and air more precisely, ensuring complete combustion with lower excess air. This reduces flame temperature, which reduces NOx formation.

Systems meeting this threshold include:

• Low-NOx condensing gas boilers with Class 5 certification

• Advanced modulating burner technology

• Well-designed district heating from efficient plant

Cost premium over Class 4 is modest: £100-200 per boiler unit typically. For a typical commercial development with 5-10 boilers, you're looking at £500-2,000 additional cost to gain 1 extra BREEAM credit. For residential developments with individual boilers per dwelling, the differential might be £100 per home.

Availability is excellent—all major manufacturers (Viessmann, Worcester Bosch, Vaillant, Baxi) offer Class 5 boilers as standard product lines. Installation requirements are identical to Class 4 equipment.

Three Credits - NOx Class 6 (≤40 mg/kWh)

Ultra-low NOx boilers achieve this through advanced premix burners, sophisticated controls, and sometimes flue gas recirculation or secondary combustion chambers. The technology is proven and reliable, though slightly more complex than Class 4/5 equipment.

Systems meeting this threshold include:

• Ultra-low NOx gas boilers with Class 6 certification

• Heat pumps (air source, ground source, water source) - zero direct emissions

• Electric heating systems - zero direct emissions at building

• District heating where central plant meets ≤40 mg/kWh

Cost premium over Class 4 typically ranges £200-400 per boiler unit. For heat pumps, capital cost is significantly higher (£8,000-35,000 for residential installations), but they also contribute substantially to energy performance credits, making the total value proposition attractive.

Ultra-low NOx boilers are increasingly common, particularly in London where they're often required by planning policy in Air Quality Management Areas. Specifying Class 6 early in design causes no complications—it's a product specification decision, not a system redesign.

Non-Combustion Systems and Zero Emission Heating

Heat Pumps:

All heat pump technologies achieve 3 credits automatically:

• Air source heat pumps extracting heat from outside air

• Ground source heat pumps using stable ground temperatures

• Water source heat pumps from boreholes or water bodies

These produce zero direct NOx emissions as there's no combustion. They use electricity to move heat rather than burning fuel to create it. Whilst electricity generation produces upstream emissions at power stations, BREEAM Pol 02 assesses only direct building emissions.

The dual benefit of heat pumps—achieving 3 air quality credits whilst substantially improving energy performance—makes them increasingly attractive despite higher capital costs. They're particularly effective in well-insulated buildings with underfloor heating or other low-temperature distribution systems.

Electric Heating:

Direct electric heating (panel heaters, storage heaters, electric underfloor heating) achieves 3 credits through zero direct emissions. However, electric heating typically performs poorly in the energy section due to high carbon emissions from grid electricity and low conversion efficiency.

This creates a trade-off: gain 3 Pol 02 credits but lose multiple energy credits. Heat pumps avoid this trade-off by achieving both air quality and energy credits simultaneously.

District Heating:

Buildings connected to district heating networks are treated based on the central plant emissions:

• If plant emissions ≤40 mg/kWh: building achieves 3 credits

• If plant emissions ≤70 mg/kWh: building achieves 2 credits

• If plant emissions ≤100 mg/kWh: building achieves 1 credit

• If plant emissions >100 mg/kWh: building achieves 0 credits

Connection to district heating is treated as zero direct building emissions, with credits based on the heat source. Obtain emission data from the network operator—this should be available through their environmental certifications or plant specifications.

Waste-to-energy district heating typically has NOx emissions exceeding 100 mg/kWh, preventing achievement of air quality credits. However, connection to district heating may still be favourable overall due to planning requirements and energy section credits.

Systems That Typically Cannot Achieve Credits

Biomass Boilers:

Despite being renewable and scoring well in energy sections, biomass combustion produces substantial NOx emissions—typically 150-300 mg/kWh depending on fuel type and technology. Wood pellet boilers perform better than log boilers, but still exceed 100 mg/kWh threshold.

Biomass also produces significant particulate matter (PM10 and PM2.5), which BREEAM treats with zero tolerance. Any PM emissions prevent achieving credits regardless of NOx performance.

Biomass can still be appropriate for overall BREEAM strategy—it contributes to renewable energy credits and reduces carbon emissions—but it won't achieve Pol 02 credits.

Solid Fuel Systems:

Coal, anthracite, or wood burning systems have very high NOx and particulate emissions, making them incompatible with any Pol 02 credits. Additionally, solid fuel combustion for primary heating prevents achieving BREEAM Outstanding rating in Version 7.

Oil Heating:

Standard oil boilers typically emit 120-180 mg/kWh NOx, preventing achievement of any credits. Modern condensing oil boilers with low-NOx burners can achieve 80-100 mg/kWh, potentially securing 1 credit, but specification is limited and cost premium significant.

Measurement Standards and Conversion Factors

All NOx emissions must be measured on a dry basis at 0% excess oxygen, as per Ecodesign Directive 2009/125/EC. However, manufacturers often quote emissions at 3% or 6% excess oxygen as these reflect typical operating conditions.

Conversion factors to 0% excess oxygen:

If quoted at 3% excess oxygen: multiply by 1.17If quoted at 6% excess oxygen: multiply by 1.40If quoted at 15% excess oxygen: multiply by 3.54

General formula: multiply by [20.9 / (20.9 - x)] where x is the % excess oxygen

Example: A boiler emitting 60 mg/kWh at 3% excess oxygen actually emits 70.2 mg/kWh at 0% excess oxygen (60 × 1.17 = 70.2), achieving 2 credits not 3.

Always check manufacturer datasheets carefully. If the oxygen level isn't stated, assume 0% or contact the manufacturer for clarification. Getting this wrong means specifying equipment that doesn't achieve expected credits.

Assessment Rules and Special Cases

Multiple Heating Systems:

Where a building has multiple heating systems (e.g., gas boilers for space heating plus electric water heaters), credits are awarded based on the worst-performing system. You cannot mix-and-match to achieve higher credits.

Example: If you specify NOx Class 6 boilers (40 mg/kWh) for most of the building but include one standard boiler (100 mg/kWh) serving a small area, the entire building achieves only 1 credit. The worst performer determines the overall rating.

Backup Systems:

Emergency backup heating can be excluded from assessment only if it's excluded from SBEM or SAP calculations in BREEAM Ene 01 (Energy Performance). This assumes backup systems run only during genuine emergencies, so their environmental impact is negligible.

If backup systems are included in energy calculations—meaning they contribute to normal operation—they must meet air quality thresholds to achieve credits.

Industrial Buildings:

Industrial buildings split into two assessment areas:

• Office and welfare areas: must achieve ≤70 mg/kWh for 1 credit

• Operational/process areas: must achieve ≤70 mg/kWh for 1 credit

Maximum 2 credits available (rather than 3) for industrial buildings, reflecting that process heating may have different constraints than comfort heating.

Highly Insulated Buildings:

Where heating load is ≤7% of the heat load for a Building Regulations-compliant building of the same size and type, one credit can be awarded regardless of NOx emissions. This recognises that extremely well-insulated buildings use so little heating that their air quality impact is minimal.

Figures must be based on approved building energy calculation software (SBEM, SAP, or equivalent). This exception rarely applies—achieving 93% reduction in heat demand requires exceptional fabric performance beyond Passivhaus standards.

How to Achieve BREEAM Pol 02

Design Stage Specification

Work with your mechanical and electrical engineer during RIBA Stage 2/3 to specify appropriate heating systems. This is a product selection decision, not a system redesign, so it doesn't require extensive rework if caught early.

For Gas Heating Projects:

Request NOx Class 6 certification (≤40 mg/kWh at 0% excess oxygen) in your heating system performance specification. Major manufacturers offer these as standard products:

• Viessmann Vitodens range (many models Class 6)

• Worcester Bosch Greenstar range (several Class 6 options)

• Vaillant ecoTEC range (Class 6 available)

• Baxi EcoBlue range (Class 6 models)

Specify condensing operation, modulating burners, and weather compensation controls for best performance and reliability.

For Heat Pump Projects:

Any heat pump technology achieves 3 credits automatically. Specify appropriate type for building characteristics:

• Air source heat pumps: £8,000-14,000 residential, £20,000-60,000 commercial

• Ground source heat pumps: £20,000-35,000 residential, £60,000-200,000 commercial

• Water source heat pumps: typically commercial scale, site-specific pricing

Heat pumps work best with low-temperature heating distribution (underfloor heating, oversized radiators) and require good building fabric performance. Design the heating system around heat pump characteristics from the start—retrofitting heat pumps into systems designed for boilers rarely works well.

For District Heating Connections:

Obtain emissions data from the network operator. If the plant meets thresholds, your building achieves credits through connection. If plant emissions are too high, consider whether connection is mandatory through planning policy or whether individual building systems might perform better for BREEAM.

Evidence Requirements for BREEAM Assessor

Your BREEAM assessor needs specific documentation:

Manufacturer's Data Sheets:

Must show NOx emissions in mg/kWh at a stated excess oxygen level. Standard product catalogues often omit this—you need technical data sheets or emission certificates following Ecodesign Directive requirements.

The data sheet must state:

• NOx emission rate (mg/kWh)

• Measurement basis (% excess oxygen)

• Test standard used (typically BS EN 15502 for boilers)

• Product model and serial range

For Multiple Systems:

If different boilers serve different areas, provide data for all units. Remember the worst performer determines credit level, so ensure all equipment meets your target threshold.

For Heat Pumps:

Manufacturer confirmation that the unit is a non-combustion heat pump producing zero direct emissions. This is usually straightforward from standard specifications.

For District Heating:

Letter from network operator confirming central plant NOx emissions at 0% excess oxygen. This may require coordination with the energy centre developer or operator.

Cost-Benefit Analysis

Pol 02 represents excellent value in BREEAM assessments:

Class 4 to Class 5 upgrade:Cost: £100-200 per boilerBenefit: 1 additional BREEAM creditTypical project cost: £500-2,000 totalRating impact: ~0.1% of overall score

Class 4 to Class 6 upgrade:Cost: £200-400 per boilerBenefit: 2 additional BREEAM creditsTypical project cost: £1,000-4,000 totalRating impact: ~0.2% of overall score

Compare this to other credit costs:

• Enhanced fabric performance: £5,000-20,000 per energy credit

• Renewable energy systems: £10,000-50,000 per energy credit

• Ecological enhancements: £3,000-10,000 per ecology credit

Pol 02 credits cost £500-2,000 each, making them among the cheapest credits available. For projects targeting Very Good or Excellent ratings, these are essential low-cost gains.

Common Challenges with Pol 02

Late Specification Changes

The most common problem is leaving heating system specification until tender stage, when Class 4 boilers are already included in tender documents. Changing to Class 6 post-tender creates variations and cost negotiations.

Avoid this by specifying NOx performance requirements in early stage documentation. Include "NOx emissions ≤40 mg/kWh at 0% excess oxygen" in your performance specification at RIBA Stage 3, ensuring all tender returns price appropriate equipment.

Manufacturer Data Confusion

Manufacturer literature sometimes quotes emissions at different oxygen levels or uses different units. Common confusions:

• ppm vs mg/kWh: These are different units requiring conversion. BREEAM requires mg/kWh. If data only shows ppm, contact manufacturer for mg/kWh figures or conversion factors.

• Different oxygen levels: Always check the stated oxygen level. A boiler showing 50 mg/kWh at 6% oxygen actually emits 70 mg/kWh at 0% oxygen, achieving only 2 credits not 3.

• Different test standards: Ensure testing follows relevant standards (BS EN 15502 for boilers, BS EN 14792 for emissions testing). If manufacturer uses non-standard testing, the assessor may question validity.

Backup System Assessment

Projects sometimes include backup boilers "for emergencies only" but include them in SBEM/SAP calculations to meet building regulations compliance margins. This means they're not truly emergency systems—they contribute to normal operation.

If backup systems appear in your energy calculations, they must meet Pol 02 thresholds. Either specify them to the same standard as primary heating, or genuinely exclude them from energy calculations and demonstrate primary heating has adequate capacity without backup.

District Heating Emissions Uncertainty

For buildings connecting to district heating networks, obtaining accurate emissions data can be difficult, particularly if the energy centre isn't yet operational. Network operators should provide design emissions, but these may be unavailable during early design stages.

If emissions data cannot be obtained, you must assume zero credits from Pol 02 in your BREEAM strategy. Don't rely on assumptions that district heating will meet thresholds—waste-to-energy and biomass plants typically cannot, whilst gas CHP plants usually can.

Expert Support for Pol 02

Pol 02 primarily requires proper M&E engineering specification rather than specialist consultancy. However, several scenarios benefit from specialist air quality input:

When Specialist Support Helps:

Your mechanical engineer handles standard heating system specification, but specialist support helps with:

• Air quality impact assessments for planning in Air Quality Management Areas

• District heating network emissions verification

• Coordinating BREEAM air quality credits with planning policy air quality requirements

• Buildings with complex mixed heating systems

• Industrial buildings with process heating assessment

Our Air Quality Assessment Services:

We provide air quality impact assessment for planning applications, which often runs parallel to BREEAM assessment. Our assessments address:

• Compliance with London Plan Policy SI1 Air Quality Neutral

• AQMA assessment for planning applications

• Construction dust risk assessment following IAQM guidance

• Air quality positive design strategies

When projects require both BREEAM certification and planning air quality assessment, we coordinate both, ensuring consistent emissions data and avoiding duplication of technical work.

Related BREEAM Credits

Ene 01 Reduction of Energy Use and Carbon Emissions: Heating system efficiency and fuel choice affect energy performance credits. Heat pumps achieving Pol 02 credits often also contribute substantially to energy credits.

Pol 01 Impact of Refrigerants: Heat pumps contain refrigerants with global warming potential, requiring assessment under Pol 01 alongside their air quality benefits under Pol 02.

Hea 02 Indoor Air Quality: External air quality from heating emissions can affect fresh air intake positions and indoor air quality strategies, linking outdoor emissions to internal environment quality.

Pol 02 Frequently Asked Questions

Do heat pumps always achieve 3 credits even though electricity generation produces emissions?

Yes. BREEAM Pol 02 assesses direct building emissions only. Heat pumps produce zero direct NOx emissions as they don't burn fuel—they use electricity to move heat. Upstream emissions from electricity generation aren't counted under Pol 02 (they're addressed through Ene 01 carbon factors). This is why heat pumps are attractive for BREEAM—they achieve maximum air quality credits whilst also improving energy performance.

Can we achieve credits if we have to use biomass for planning policy reasons?

Unfortunately no. Biomass combustion produces NOx emissions typically 150-300 mg/kWh, well above the 100 mg/kWh threshold for any credits. Additionally, biomass produces particulate matter, which BREEAM treats as zero-tolerance. If planning policy mandates biomass use, you'll need finding your BREEAM credits elsewhere. Biomass contributes to renewable energy credits, but cannot achieve air quality credits.

What if our building has both gas boilers and electric water heating?

Credits are awarded based on the worst-performing system. If your gas boilers emit 40 mg/kWh (Class 6) but you also have direct electric water heating (0 mg/kWh), the gas boilers are the worst performer, so you achieve 3 credits. If you had Class 4 boilers (100 mg/kWh) with electric water heating, the boilers are worst performer, so only 1 credit. The principle is that the highest-emitting equipment determines the building's overall performance.

How do we handle backup generators for emergency power?

Emergency generators are not heating systems, so they're not assessed under Pol 02 Local Air Quality. They may be assessed under Pol 05 Reduction of Noise Pollution if they create noise impacts. Backup heating systems (not backup power) fall under Pol 02, but only if included in SBEM/SAP energy calculations for Ene 01.

Does specifying ultra-low NOx boilers create maintenance issues?

No more than standard condensing boilers. NOx Class 6 boilers use proven technology—premix burners, modulating controls—that's been in use for over a decade. Maintenance requirements are similar to Class 4/5 equipment. Annual servicing by qualified engineers is essential for all condensing boilers regardless of NOx class. The additional complexity is minimal and reliability is excellent. Most manufacturers offer identical warranties across their boiler ranges.

Get Expert Help with Pol 02

Achieving BREEAM Pol 02 and Pol 03 credits primarily requires proper M&E specification, but our team can provide supporting air quality assessment when projects require planning compliance alongside BREEAM certification.

We offer:

• Air quality impact assessment for planning applications

• Air Quality Neutral calculations for London developments

• Construction dust risk assessment following IAQM guidance

• Coordination between BREEAM air quality credits and planning requirements

• Technical review of heating system emissions for BREEAM evidence

For projects in Air Quality Management Areas or requiring air quality positive design, we ensure your heating specification satisfies both planning policy and BREEAM requirements through coordinated assessment.

Based in London and operating throughout Kent, Essex and Scotland, we provide rapid turnaround for developments requiring both BREEAM and planning air quality support.

Contact us to discuss how air quality assessment can support your BREEAM certification: