BREEAM V7 AIR QUALITY CREDITS | ZERO FOSSIL FUELS FOR OUTSTANDING

BREEAM Version 7's fossil fuel ban for Outstanding rating represents the most significant policy shift in the scheme's 30-year history, fundamentally redefining what constitutes sustainable building design. From January 2025, projects pursuing Outstanding certification must eliminate all fossil fuel combustion on-site—gas boilers, oil heating, LPG, and even biomass cannot be specified regardless of their efficiency or emission performance.

This change aligns BREEAM with UK government net-zero targets and recognises that continuing to install fossil fuel heating in new buildings undermines climate commitments. Buildings constructed in 2025 will operate through 2085 and beyond—locking in gas infrastructure for 60+ years contradicts trajectories towards decarbonised heating by 2050. Version 7 makes this trade-off explicit: pursue Outstanding and commit to zero-carbon heating, or accept Excellent rating with continued fossil fuel use.

For development teams, the implications extend beyond heating system specification. Heat pumps require different design approaches: lower flow temperatures, larger heat emitters, enhanced building fabric, acoustic considerations, and typically 2-3x higher capital costs. Projects must decide during feasibility whether Outstanding remains achievable, or whether Excellent represents a more pragmatic target given site constraints, building typology, and commercial viability.

Overview of BREEAM Version V7 Air Quality Changes

BREEAM V7 air quality credits maintain the three-tier NOx emission structure from Version 6 but introduce the fossil fuel prohibition and enhanced assessment requirements across multiple aspects.

Key Changes Summary:

Zero Fossil Fuel Mandate for Outstanding: Complete ban on fossil fuel combustion for space heating, water heating, and cooking. Heat pumps, electric heating, or renewable district heating become the only viable options.

NOx Thresholds Unchanged: The three-tier structure continues (≤100mg, ≤70mg, ≤40mg per kWh at 0% excess oxygen), but fossil fuel prohibition means these thresholds become irrelevant for Outstanding—zero direct emissions required.

Excellent Rating Pathway: Excellent rating permits fossil fuel use with ultra-low NOx equipment (≤40mg/kWh), providing pragmatic pathway for buildings where heat pumps aren't viable.

Enhanced Heat Pump Requirements: Heat pumps achieving credits must meet noise standards, efficiency thresholds, and installation quality requirements—not automatic credit just for being non-combustion.

Exemptions Limited: Emergency backup generators permitted (genuine emergencies only), but backup heating counted if operational. Process heating exemptions require robust justification—most applications rejected.

Regional Variation: Scotland and Wales maintain similar fossil fuel restrictions but with regional climate considerations and alignment with devolved government policies.

Evidence Requirements Enhanced: Demonstration of zero fossil fuel use requires comprehensive M&E specifications, commissioning records, and operational monitoring—not just design intent statements.

These changes reflect broader policy direction: Future Homes Standard (England), New Build Heat Standard (Scotland), and similar regulations moving towards heat pump deployment as default for new buildings.

Credit Structure Version 7: NOx Tiers and Fossil Fuel Prohibition

Version 7 maintains the familiar three-tier credit structure but overlays this with the Outstanding rating fossil fuel prohibition.

Credit Allocation: Three Tiers Based on NOx Emissions

One Credit: NOx ≤100 mg/kWh

Heating and hot water systems emitting maximum 100 milligrams nitrogen oxides per kilowatt-hour thermal output, measured on dry basis at 0% excess oxygen.

Heating systems achieving this threshold:

• Standard condensing gas boilers (NOx Class 4) - typical 80-100mg/kWh

• Modern oil boilers with low-NOx burners - typically 80-120mg/kWh

• Some biomass systems (though particulate matter often prevents credits)

• Gas combined heat and power (CHP) with emission controls

Availability and Cost:

This represents baseline modern specification—most condensing boilers manufactured since 2015 achieve Class 4 certification. No cost premium over obsolete equipment. Widely available from all major manufacturers.

Version 7 Context:

Achieving 1 credit is straightforward for Excellent-targeted schemes using fossil fuels. However, for Outstanding-targeted schemes, this tier is irrelevant—fossil fuels prohibited regardless of NOx performance.

Two Credits: NOx ≤70 mg/kWh

More stringent threshold requiring low-NOx condensing boilers with advanced burner technology (NOx Class 5).

Heating systems achieving this threshold:

• Low-NOx condensing gas boilers (Class 5) - typical 50-70mg/kWh

• Advanced modulating premix burners

• Well-designed gas CHP with selective catalytic reduction (SCR)

• Some district heating from efficient gas plant

Availability and Cost:

Low-NOx boilers widely available from major manufacturers:

• Viessmann Vitodens range (many Class 5 models)

• Worcester Bosch Greenstar Si (Class 5)

• Vaillant ecoTEC plus (Class 5 available)

Cost premium: £100-200 per boiler unit over Class 4 (approximately 10-15% increase).

Version 7 Context:

Suitable for Excellent-targeted projects wanting to maximise air quality performance whilst retaining fossil fuel heating. Two credits insufficient for Outstanding (requires 3 credits) and fossil fuel prohibition applies anyway.

Three Credits: NOx ≤40 mg/kWh OR Zero Direct Emissions

Most stringent threshold requiring either ultra-low NOx combustion equipment (Class 6) or non-combustion heating systems.

Combustion systems achieving this threshold:

• Ultra-low NOx gas boilers (Class 6) - typical 30-40mg/kWh

• Advanced premix modulating burners with flue gas recirculation

• Gas CHP with comprehensive emission controls (rare, expensive)

Non-combustion systems achieving this threshold:

• Air source heat pumps - zero direct emissions

• Ground source heat pumps - zero direct emissions

• Water source heat pumps - zero direct emissions

• Direct electric heating - zero direct emissions (though poor energy performance)

• District heating from renewable sources - assessed on plant emissions

Availability and Cost:

Ultra-low NOx boilers (Class 6):

• Increasingly common, particularly in London (AQMA requirements)

• Cost premium: £200-400 per boiler over Class 4 (20-30% increase)

• Available from: Viessmann Vitodens 200-W, Vaillant ecoTEC exclusive, ATAG iC

Heat pumps (air source residential):

• Capital cost: £8,000-14,000 installed (excluding distribution system)

• Running costs: Lower than gas (depending on electricity tariff)

• Coefficient of Performance (COP): 2.5-4.0 depending on conditions

• Lifespan: 15-20 years

Heat pumps (ground source residential):

• Capital cost: £20,000-35,000 installed (including ground array)

• Running costs: Lowest of all heating options typically

• COP: 3.0-4.5 year-round

• Lifespan: 20-25 years (ground array 50+ years)

Heat pumps (commercial buildings):

• Air source: £20,000-100,000+ depending on scale

• Ground/water source: £60,000-500,000+ depending on scale

• Packaged chiller/heat pump systems for larger buildings

• VRF heat pump systems for flexible zoning

Version 7 Context:

Three credits mandatory for Outstanding rating. Fossil fuel options (Class 6 boilers) prohibited under Outstanding requirements, so heat pumps or equivalent become the only viable pathway.

For Excellent rating, either Class 6 boilers or heat pumps achieve 3 credits—providing choice based on project specifics.

The Outstanding Rating Fossil Fuel Prohibition

Mandatory Requirement for Outstanding:

Buildings targeting Outstanding rating must have zero fossil fuel combustion on-site for:

• Space heating

• Water heating

• Cooking (commercial kitchens)

• Any other building services

This prohibition is absolute—no fossil fuels permitted regardless of efficiency, renewable fuel source claims, or carbon offsetting arrangements.

Prohibited Heating Systems for Outstanding:

Cannot be specified:

• Gas boilers (natural gas, regardless of NOx Class 6 or hydrogen-ready claims)

• Oil boilers (kerosene, heating oil, regardless of efficiency)

• LPG systems (liquefied petroleum gas, regardless of source)

• Biomass boilers (wood pellets, logs, despite being renewable fuel source)

• Gas CHP (combined heat and power, regardless of efficiency)

• Hybrid systems including fossil fuel elements (e.g., heat pump with gas backup)

Permitted Heating Systems for Outstanding:

Must use:

• Heat pumps: Air source, ground source, water source, or hybrid heat pumps without fossil fuel backup

• Direct electric heating: Panel heaters, storage heaters, electric underfloor (though energy performance implications apply)

• District heating: From renewable sources (heat pumps, waste heat, solar thermal, geothermal) with emissions ≤40mg/kWh at central plant

• Solar thermal: Renewable heat directly from solar collectors

• Heat recovery: Waste heat capture from processes, data centres, metro systems

The Biomass Question:

Biomass heating (wood pellets, logs) is renewable but involves combustion producing:

• NOx emissions typically 150-300mg/kWh (far exceeding thresholds)

• Particulate matter (PM10, PM2.5) - zero tolerance under BREEAM

• Direct CO₂ emissions (despite carbon neutrality argument)

Version 7 treats biomass as fossil fuel for Outstanding prohibition purposes. The combustion process, regardless of fuel renewability, contradicts zero-emission requirement.

Commercial Kitchen Implications:

Commercial kitchens traditionally prefer gas for cooking (flame control, chef preference, equipment availability). Version 7 creates dilemma:

Option A: All-electric kitchens (induction hobs, electric ovens, combi-steamers)

• Achieves Outstanding compliance

• Technology proven and increasingly common

• Initial chef resistance but operational performance acceptable

• Equipment cost premium: 20-30% over gas

Option B: Gas cooking, accept Excellent rating maximum

• Outstanding unachievable with gas cooking

• May be pragmatic for specific catering types

• Particularly high-volume cooking (hotels, hospitals, large restaurants)

Most Outstanding-targeted projects now specify all-electric commercial kitchens. Technology has advanced significantly—induction cooking provides precise temperature control matching or exceeding gas performance.

Heating and Cooking Load Split:

For buildings where cooking represents small energy proportion (<5% total), BREEAM may consider exemptions. Requires:

• Demonstrated that cooking is genuinely minor use

• No alternative available for specific cooking requirement

• All other heating uses (space, water) use zero-emission systems

• Application for BREEAM Bespoke assessment

Most standard developments cannot use this exemption—cooking typically represents >5% energy use in buildings with commercial kitchens.

Exemptions and Special Cases

Version 7 provides limited exemptions to the fossil fuel prohibition, but these are narrowly defined and strictly applied.

Exemption 1: Emergency Backup Generators

Emergency diesel or gas generators are permitted provided:

Conditions:

• Genuinely emergency use only (power failure, critical system backup)

• Not used for peak shaving, load balancing, or regular operation

• Cannot be included in building energy calculations (Ene 01)

• Annual operating hours <50 hours (testing and genuine emergencies)

• Emissions controls to appropriate standards

Evidence required:

• Generator specifications showing emergency-only control system

• Operational logs demonstrating use patterns

• Exclusion from energy modelling

Not exempt:

• Backup heating systems that could operate regularly

• CHP units providing peak load shaving

• Generators used for demand response or grid services

Exemption 2: Process Heating (Limited)

Industrial or laboratory process heating requiring specific fuel types may be exempt where:

Conditions:

• Process genuinely cannot function with electric/heat pump alternatives

• Detailed technical justification provided

• Explored all alternatives comprehensively

• Process heating represents <10% total building energy use

• Space and water heating use zero-emission systems

Examples potentially qualifying:

• Specialist high-temperature processes (>400°C) where electric alternatives don't exist

• Heritage conservation processes requiring specific fuel types

• Research equipment with unique energy requirements

Examples NOT qualifying:

• Standard laboratory equipment (electric alternatives available)

• Industrial space heating (heat pumps viable for most applications)

• "Preference" rather than genuine technical necessity

Application process:

• Submit BREEAM Bespoke application with technical justification

• BRE technical team review on case-by-case basis

• Most applications rejected—bar is very high

Exemption 3: Listed Buildings and Heritage Constraints

Listed buildings where heat pump installation would damage heritage value may receive exemptions:

Conditions:

• Building listed Grade I, II*, or II

• Conservation officer written confirmation that heat pumps would harm heritage value

• Explored all possible heat pump configurations (internal units, concealed external units)

• Demonstrated preservation conflict genuinely insurmountable

Evidence required:

• Listed building consent application documents

• Conservation officer correspondence

• Heat pump feasibility study showing configurations considered

• Historic building consultant report

Reality:

Most listed buildings can accommodate heat pumps with sensitive design:

• Concealed external units in courtyards or roof spaces

• Internal air handling units in non-heritage spaces

• Ground source with boreholes avoiding below-ground heritage

• Integration with existing radiator systems (low-temperature emitters may be needed)

Exemptions granted only where comprehensive exploration proves heat pumps genuinely impossible without heritage harm.

Exemption 4: Temporary Buildings

Buildings with design life <10 years may use fossil fuel heating:

Rationale:

• Short operational life reduces carbon impact

• Economics of heat pump installation don't justify temporary structures

• Planning permission typically temporary for these buildings

Examples:

• Construction site offices and facilities

• Temporary event spaces (exhibitions, festivals)

• Interim accommodation pending permanent development

Standard buildings don't qualify:

• "Temporary" commercial leases in permanent buildings

• Modular construction intended for 20+ year use

• Buildings designed for relocation rather than demolition

Non-Exemptions (Commonly Misunderstood):

Not exempt - Backup Heating:

Gas or oil boilers providing backup to heat pumps are NOT exempt. If sized to provide heating, they're operational systems counted under air quality assessment.

Only genuine emergency-only systems (not heating) are exempt.

Not exempt - "Hydrogen Ready" Boilers:

Boilers marketed as "hydrogen ready" burning natural gas currently are NOT exempt. They're fossil fuel systems today, regardless of potential future hydrogen use.

If/when hydrogen infrastructure exists and hydrogen is renewable, BREEAM policy may change. Currently, hydrogen-ready boilers burn fossil gas and are prohibited.

Not exempt - "Renewable Gas" or Biomethane:

Biomethane from anaerobic digestion, despite being renewable, involves combustion. Currently treated as fossil fuel for Outstanding purposes.

Version 7 focuses on combustion elimination, not fuel carbon intensity. Renewable combustion still produces NOx and local air quality impacts.

Not exempt - Carbon Offsetting:

Cannot install gas boilers and "offset" emissions through renewable electricity purchase or carbon credits. The zero fossil fuel requirement is absolute—not negotiable through offsetting.

Heat Pump Requirements for Outstanding

Heat pumps achieving air quality credits must meet performance and installation quality requirements—not automatic credits simply for being non-combustion.

Minimum Performance Standards:

Coefficient of Performance (COP):

Heat pumps must demonstrate minimum seasonal performance:

• Air source heat pumps: SCOP ≥2.8 (seasonal coefficient of performance)

• Ground source heat pumps: SPF ≥3.2 (seasonal performance factor)

• Water source heat pumps: SPF ≥3.5

Testing standard:

• EN 14511 for rated performance

• MCS (Microgeneration Certification Scheme) calculation methodology for seasonal performance

• Performance at design conditions (typically -3°C for ASHP, 0°C ground for GSHP)

Why this matters:

Low-efficiency heat pumps undermine the carbon benefit of fossil fuel elimination. A poorly designed heat pump system with SCOP 2.0 may have higher carbon emissions than a condensing gas boiler (depending on grid electricity carbon intensity).

Version 7 ensures heat pumps specified achieve genuine carbon savings through minimum efficiency requirements.

Sizing and Design Requirements:

Heat Load Calculations:

Heat pump sizing must be based on proper heat loss calculations:

• Room-by-room heat loss assessment to EN 12831

• Design external temperature appropriate for location (-3°C to -5°C UK)

• Internal design temperatures appropriate for use (21°C living spaces, 18°C bedrooms residential)

• Allowance for domestic hot water demand

Cannot use:

• Rules of thumb (e.g., "100W/m²")

• Previous building's boiler size

• Oversizing "to be safe"

Distribution System Design:

Heat pumps operate at lower flow temperatures than boilers:

• Gas boilers: 70-80°C flow temperature typical

• Heat pumps: 35-55°C flow temperature typical (depending on emitter type)

Distribution requirements:

• Underfloor heating: Ideal for heat pumps (35°C flow typically)

• Radiators: Must be sized for low temperature (2-3x larger than boiler-sized radiators)

• Fan coils: Effective for commercial buildings

• Air handling units: Require specific selection for low temperature heating coils

Cannot simply:

• Replace boiler with heat pump using existing radiators (undersized for low temperature)

• Use high-temperature heat pumps (>60°C flow) as default (lower efficiency)

Noise Requirements:

Heat pumps produce noise from:

• Compressor operation (most significant)

• Fan operation (air source units)

• Defrost cycles (periodic, more intrusive)

Version 7 noise standards:

Air source heat pump external units must achieve:

• Maximum 42 dB(A) at 1 metre from unit during normal operation

• Maximum 45 dB(A) at 1 metre during defrost cycle

• Noise rating at site boundary must comply with BS 4142 assessment (rating level not exceeding background by >+5dB day, +0dB night)

For residential developments:

Multiple heat pumps (one per dwelling) create cumulative noise:

• Careful positioning: Away from bedrooms, boundaries, quiet amenity spaces

• Acoustic screening: Barriers, enclosures where necessary

• Low-noise models: Premium units with sound-dampened compressors

• Night setback: Scheduling reducing operation during sensitive hours

Evidence required:

• Manufacturer's noise data for specified heat pump models

• Acoustic assessment if sensitive receptors within 15m

• Positioning strategy minimising noise impact

• Compliance with Building Regulations Approved Document E (noise)

Installation Quality Requirements:

MCS Certification (UK):

Installations must meet Microgeneration Certification Scheme standards:

• MCS 001: Accredited installer requirements

• MCS 020: Heat pump installation standard

• Design and performance estimation: Using MCS Heat Pump Calculator or equivalent

Commissioning:

Comprehensive commissioning required:

• Flow rates measured and confirmed adequate

• Flow temperatures achieved under design conditions

• Defrost cycle operation verified

• Controls programming confirmed

• Building user training provided

Evidence for BREEAM:

• MCS certificate for installation

• Commissioning records

• Performance testing results

• Building user guide including heat pump operation

Poor quality installations undermine performance:

Common issues preventing credit achievement:

• Undersized distribution (radiators too small for low temperature)

• Incorrect refrigerant charge (reduces efficiency 20-30%)

• Poor positioning (short-cycling, recirculation of discharged air)

• Controls not optimised (weather compensation, setback)

Version 7 requires evidence of quality installation, not just heat pump specification.

Excellent Rating Pathway: Ultra-Low NOx Fossil Fuels Permitted

Version 7 maintains a pragmatic pathway for developments unable to achieve Outstanding's heat pump requirement: Excellent rating permits fossil fuel use with ultra-low NOx equipment.

Excellent Rating Air Quality Requirements:

Option A: Ultra-Low NOx Boilers (≤40mg/kWh)

Gas boilers achieving NOx Class 6 certification:

• 3 air quality credits achieved

• Contributes to Excellent rating (requires multiple category achievements)

• Significantly cheaper than heat pumps (capital cost)

• Familiar technology for contractors and maintenance

Suitable for:

• Buildings where heat pumps genuinely difficult (existing buildings retrofit, constrained sites)

• Developments targeting Excellent rather than Outstanding

• Interim solution recognising heat pump transition takes time

Option B: Heat Pumps

Zero-emission heating achieving 3 credits:

• Same credit achievement as Class 6 boilers

• Additionally contributes to energy performance credits

• Higher capital cost but lower operational carbon

Strategic Decision:

Choose Class 6 boilers when:

• Excellent is target rating (Outstanding not required by planning or commercial reasons)

• Budget constraints make heat pumps unviable

• Building type difficult for heat pumps (high temperature processes, limited plant space)

• Existing infrastructure favours gas connection

Choose heat pumps when:

• Outstanding potentially achievable (heat pumps enable, gas prevents)

• Energy performance critical (heat pumps score better in Ene 01)

• Future-proofing important (gas infrastructure may face restrictions)

• Operating costs prioritised over capital costs

Cost Comparison Excellent Rating:

50-dwelling residential development:

Option A - Class 6 Boilers:

• Boiler costs: £1,000-1,400 per dwelling × 50 = £50,000-70,000

• Distribution: £2,500 per dwelling × 50 = £125,000

• Gas infrastructure: £50,000-80,000

• Total capital: £225,000-£300,000

• Operating costs (gas): £800-1,200 per dwelling per year

Option B - Air Source Heat Pumps:

• Heat pump costs: £8,000-12,000 per dwelling × 50 = £400,000-600,000

• Enhanced distribution: £4,000 per dwelling × 50 = £200,000 (larger radiators/UFH)

• Electrical infrastructure upgrade: £80,000-150,000

• Total capital: £680,000-£950,000

• Operating costs (electricity): £600-900 per dwelling per year (depending on tariff)

Capital cost difference: £450,000-£650,000 (heat pumps more expensive)

Operating cost savings: £200-300 per dwelling per year (heat pumps cheaper to run)

Payback period: 8-12 years (based on operating cost differential)

For Excellent-targeted schemes, Class 6 boilers offer lower capital cost pathway achieving same air quality credits as heat pumps. Outstanding is unachievable either way, so heat pump capital cost premium may not be justified.

Environmental Performance Comparison:

Carbon Emissions:

Current UK grid electricity carbon intensity makes gas and heat pumps roughly comparable:

• Gas boiler (90% efficient): ~215 gCO₂/kWh heat delivered

• Heat pump (SCOP 3.0): ~190 gCO₂/kWh heat delivered (using grid electricity ~570 gCO₂/kWh)

As grid decarbonises (2030-2050):

• Gas emissions remain constant

• Heat pump emissions decrease with grid decarbonisation

• By 2035: heat pumps ~50% lower carbon than gas

• By 2050: heat pumps ~90% lower carbon (near-zero carbon grid)

Strategic Implication:

Heat pumps provide better long-term carbon performance as grid decarbonises. Gas boilers lock in carbon emissions through 60-year building life.

For Excellent rating: Either technology achieves air quality credits. Choice depends on capital cost priorities, building design, and long-term carbon strategy rather than BREEAM requirements.

For Outstanding rating: No choice—must be heat pumps or equivalent zero-emission systems.

Regional Variations: Scotland and Wales

Version 7 maintains regional variations reflecting devolved government policies and local climate considerations.

Scotland Version 7:

New Build Heat Standard Alignment:

Scotland's New Build Heat Standard (NBHS, 2024) prohibits fossil fuel heating in new buildings from 2024. Version 7 Scotland aligns:

For Outstanding:

• Zero direct emissions heating mandatory (consistent with England)

• Heat pumps or equivalent required

• District heating from renewable sources permitted

For Excellent:

• Zero direct emissions recommended but not mandatory (differs from England)

• Ultra-low NOx gas allowed (≤40mg/kWh) where heat pumps genuinely not viable

• Justification required for fossil fuel use even at Excellent level

Climate Considerations:

Scotland's colder climate affects heat pump performance:

• Design temperatures: -5°C to -8°C (Highland zones)

• Higher heating demand than southern England

• Air source heat pumps less efficient at low ambient temperatures

• Ground source heat pumps preferred for consistent performance

Regional Factors:

• Off-gas-grid areas (Highland, Islands): Heat pumps or electric already common

• Urban central belt: Gas infrastructure available but heat pump transition required

• Renewable electricity high proportion: Heat pumps benefit from low-carbon Scottish grid

Evidence Requirements:

• Alignment with NBHS demonstrated

• Heat pump specifications appropriate for Scottish climate

• Design temperatures and performance calculations for local conditions

Wales Version 7:

Future Wales Plan Alignment:

Wales' Future Wales spatial plan emphasises decarbonisation. Version 7 Wales reflects this:

For Outstanding:

• Zero fossil fuel heating mandatory (consistent with England and Scotland)

• Heat pumps or renewable district heating required

For Excellent:

• Ultra-low NOx fossil fuels permitted (≤40mg/kWh)

• Welsh language requirements for building user guides

• Coordination with local authority decarbonisation strategies

Regional Considerations:

• Rural off-gas areas (West, North Wales): Heat pumps and biomass common

• Valley communities: Potential for district heating from waste heat

• Urban South Wales: Gas infrastructure available, transition required

Air Quality Management:

Wales maintains separate air quality regulations (Environment Act Wales):

• Coordination with local authority AQMAs

• Welsh language documentation for public-facing information

• Alignment with Welsh Government decarbonisation targets

Implementation Strategies for Heat Pump Projects

Achieving Outstanding rating through heat pump specification requires integrated design approach from feasibility stage.

Feasibility Stage Decisions

Building Fabric First:

Heat pumps operate most efficiently in well-insulated buildings:

Fabric performance targets:

• U-values: 0.10-0.15 W/m²K walls, 0.10 W/m²K roof, 0.12 W/m²K floor

• Airtightness: 3-5 m³/h/m² at 50Pa (Passivhaus 0.6)

• Thermal bridging: Ψ-values <0.05 W/mK at junctions

• Glazing: Triple glazing 0.8 W/m²K, high solar gain south-facing

Why this matters:

Enhanced fabric reduces heat demand, allowing:

• Smaller heat pumps (lower capital cost)

• Lower flow temperatures (higher efficiency)

• Reduced electricity consumption (lower running costs)

• Better performance during coldest weather

Cost-effective approach:

Invest in fabric performance reducing heat demand by 30-40% versus building regulations baseline. Heat pump sized for reduced demand costs less than saving achieved through smaller unit.

Example:

Standard fabric house (Building Regs baseline):

• Heat demand: 12 kW

• Heat pump cost: £14,000

Enhanced fabric house (Passivhaus-lite):

• Heat demand: 6 kW

• Heat pump cost: £10,000

• Plus: Fabric enhancement cost £8,000

• Net additional cost: £4,000

• Benefit: Lower running costs (smaller heat pump, better efficiency), easier DHW integration, more consistent comfort

Electrical Infrastructure Assessment:

Heat pumps require three-phase power supply for:

• Residential developments: Individual heat pumps >10kW (larger houses)

• Commercial developments: Heat pumps >20kW (most commercial applications)

• District heating: Heat pump plant always requires three-phase

Feasibility checks:

• Local distribution network capacity assessment (contact DNO)

• Substation capacity for multiple heat pumps (residential estates)

• On-site infrastructure costs (cables, distribution boards)

Typical costs:

• Three-phase supply to residential plot: £2,000-5,000 per plot

• Estate substation upgrade: £50,000-200,000 (50-100 dwelling schemes)

• Commercial building supply upgrade: £20,000-100,000

Factor these into feasibility—electrical infrastructure can exceed heat pump hardware costs on large schemes.

Plant Space Allocation:

Heat pumps require different space than boilers:

Residential individual systems:

• External space: 1-2m² per air source unit (clearances for airflow)

• Internal space: Minimal (hot water cylinder, controls)

• Acoustic considerations: Position away from bedrooms, boundaries

Commercial buildings:

• Plant room: 25-40% larger than equivalent boiler plant (heat pumps, buffer vessels, pumps)

• Outdoor space: For air source condensers (roof or ground level)

• Riser space: Similar to boiler systems for distribution

Allocate adequate space during architectural design—retrofitting heat pumps into boiler-sized plant rooms frequently fails.

Concept Design (RIBA Stage 2)

Heating Strategy Selection:

For Residential:

Option A: Individual Heat Pumps per Dwelling

Each dwelling has own air source heat pump (ASHP):

Advantages:

• Individual metering (no heat network billing complexity)

• Homeowner control of heating and costs

• Straightforward planning and building control

• Familiar to mortgage lenders and surveyors

Disadvantages:

• Multiple external units (noise, visual impact)

• Electrical infrastructure for every dwelling

• Maintenance responsibility on homeowners

• Heat pump quality varies by homeowner choices

Typical cost: £8,000-12,000 per dwelling (including cylinder, controls)

Option B: Communal Heat Pump with Heat Network

Central heat pump plant serving multiple dwellings via heat network:

Advantages:

• Larger heat pumps more efficient (economies of scale)

• Single point maintenance (management company responsibility)

• Fewer external units (one plant room location)

• Can integrate thermal storage for demand management

Disadvantages:

• Heat network losses (10-15% typically)

• Billing complexity (heat meters per dwelling)

• Regulatory requirements (Heat Networks Regulations)

• Management company ongoing costs

Typical cost: £3,000-5,000 per dwelling (plant + network + heat interface units)

Option C: Hybrid District Heating

Shared ground source array with individual heat pumps:

Advantages:

• Ground source efficiency (better than air source)

• Shared ground loop cost (reduces per-dwelling cost)

• Individual dwelling control

• Compact external infrastructure

Disadvantages:

• Complex coordination (shared ground infrastructure + individual units)

• Ground investigation critical (failure affects all dwellings)

• Maintenance split between communal (ground loop) and individual (heat pumps)

Typical cost: £6,000-10,000 per dwelling (shared ground loop, individual heat pumps)

For Commercial/Mixed-Use:

Option A: Central Air Source Heat Pumps

Rooftop or ground-level air source units with distribution:

Advantages:

• Proven technology, widely available

• No ground works required

• Modular (multiple smaller units for resilience)

• Straightforward maintenance

Disadvantages:

• Noise from multiple large units

• Visual impact (rooftop units visible)

• Performance reduces in cold weather

• Space required for multiple outdoor units

Typical cost: £100-200 per kW heating capacity

Option B: Ground Source Heat Pump System

Boreholes or ground arrays serving building distribution:

Advantages:

• Best efficiency (COP 3.5-4.5 year-round)

• No external units (visually discreet)

• Silent operation (no external noise)

• Long lifespan (25+ years heat pump, 50+ years ground)

Disadvantages:

• High capital cost (drilling expensive)

• Ground investigation critical (geological risk)

• Large land area required for horizontal arrays (if not boreholes)

• Cannot retrofit boreholes easily (do it right first time)

Typical cost: £180-350 per kW heating capacity (including ground works)

Option C: Water Source Heat Pumps

River, lake, or borehole water as heat source:

Advantages:

• Excellent efficiency (stable water temperature)

• Potentially lower cost than GSHP (no borehole drilling if surface water available)

• Suitable for large buildings near water bodies

Disadvantages:

• Environmental permits required (EA, NRW, SEPA)

• Water quality affects system (filtration essential)

• Temperature fluctuations affect performance (seasonal)

• Limited applicability (requires suitable water source)

Typical cost: £150-280 per kW (excluding permits, water intake infrastructure)

Distribution System Design:

Low Temperature Radiator Systems:

Where radiators preferred (existing building retrofit, user preference):

Requirements:

• Radiators sized for 45-50°C flow temperature (2.5-3x standard sizing)

• Low-temperature radiators with enhanced surface area

• Room-by-room heat loss calculations (no oversizing allowance)

Typical specifications:

• Type 22 radiators insufficient (Type 33 or larger)

• OR fan-assisted radiators (smaller, more expensive)

• OR low-surface-temperature radiators (larger panels, safe touch temperature)

Cost premium: 30-50% over boiler-sized radiators

Underfloor Heating (UFH):

Ideal for heat pumps (35-40°C flow temperature):

Advantages:

• Lowest flow temperature (highest heat pump efficiency)

• Even heat distribution (comfort benefits)

• No radiators (architectural freedom, space saving)

• Lower running costs (improved COP)

Disadvantages:

• Ground floor only (difficult upper floors existing buildings)

• Slow response time (thermal mass stores heat)

• Installation cost premium over radiators

• Not suitable all floor finishes (carpet insulates, reduces output)

Typical cost:

• Ground floor: £40-60 per m² (screed UFH)

• Timber suspended floor: £50-70 per m² (between joists)

• Retrofit: £60-80 per m² (overlay systems)

Fan Coil Units (Commercial):

For commercial buildings, fan coil units work well with heat pumps:

Advantages:

• Effective at low temperatures (fan assistance)

• Heating and cooling from same unit (summer cooling capability)

• Smaller than equivalent radiators

• Quick response time (fan-assisted)

Disadvantages:

• Noise from fans (commercial environments tolerate)

• Maintenance (filters, fans)

• Electrical connection to each unit required

Typical cost: £500-1,500 per unit installed

Domestic Hot Water (DHW) Strategy:

Heat pumps for space heating must integrate DHW provision:

Instantaneous DHW (not viable):

Heat pumps cannot provide instantaneous hot water like combi boilers:

• Insufficient output for rapid water heating (5-15kW heat pump vs 24-35kW combi)

• Flow temperatures insufficient for legionella control

Cylinder Storage (required):

DHW cylinders mandatory with heat pump systems:

For individual dwellings:

• 180-300 litre cylinder typical (family house)

• Heat pump heats cylinder to 50-55°C

• Supplementary electric immersion to 60°C weekly (legionella prevention)

For commercial/communal:

• Large central cylinders or calorifiers

• Legionella control through temperature or alternative means (UV, filtration)

• Buffer vessels for heating system

Space requirements:

• Cylinder space: 0.6m diameter, 1.5m height typical domestic

• Accessibility for maintenance and replacement

Developed Design (RIBA Stage 3)

Heat Pump Sizing Calculations:

Heat Loss Assessment:

Detailed room-by-room heat loss to EN 12831:

For each room:

• Fabric losses (walls, roof, floor, windows)

• Ventilation losses (infiltration, mechanical ventilation)

• Thermal bridging (junctions, penetrations)

• Design temperatures (internal vs external for location)

Total building heat loss:

• Sum of all room losses

• Diversity factor (not all rooms peak simultaneously, residential only)

• DHW demand (cylinder reheat, simultaneous draw-off)

Heat pump sizing:

• Meet 100% of heat demand at design temperature (-3°C typically)

• OR meet 90% of demand with supplementary heating for coldest periods (bivalent design)

Avoid oversizing:

• Oversized heat pumps cycle frequently (reduced efficiency, increased wear)

• Better to size accurately using proper calculations

• Supplementary immersion heaters cover extreme cold periods economically

Performance Modelling:

Model seasonal performance considering:

Ambient conditions:

• Monthly temperature profiles for location

• Heating degree days

• Design day occurrence frequency

System performance:

• Heat pump COP at various ambient temperatures (manufacturer data)

• Distribution losses (pipework, heat network if applicable)

• DHW heating efficiency (cylinder losses, reheat cycles)

Annual energy consumption:

• SPF (Seasonal Performance Factor) calculation

• Electricity consumption estimate

• Carbon emissions (current and projected grid carbon intensity)

MCS Heat Pump Calculator:

UK installations should use MCS calculator:

• Input building heat loss, occupancy, location

• Output seasonal performance prediction

• Compare different heat pump models and configurations

• Demonstrate MCS compliance for certification

Acoustic Design:

Noise Prediction:

Model heat pump noise impact:

Source data:

• Manufacturer's sound power level (LwA) for specified units

• Octave band data for detailed assessment

• Consideration of operating modes (normal, defrost)

Propagation modelling:

• Distance attenuation (6dB per doubling of distance)

• Barrier effects (fences, walls, acoustic screens)

• Ground absorption

• Reflections from buildings

Receptor locations:

• Nearest residential bedroom windows

• Gardens and outdoor amenity spaces

• Boundary with neighbouring properties

• Quiet areas (nature areas, reading gardens)

Assessment against BS 4142:

Rating level vs background noise:

• +10dB or more: Significant adverse impact likely

• +5dB: Adverse impact possible

• Around 0dB: Low impact

• Below 0dB: Positive (quieter than background)

Target: Rating level not exceeding background by more than +5dB during day, +0dB at night

Mitigation measures if required:

Unit selection:

• Specify low-noise models (premium cost 10-15%)

• Multiple smaller units rather than single large unit (lower individual noise)

Positioning:

• Maximum distance from sensitive receptors

• Shield by intervening buildings/structures

• Avoid corners and enclosed spaces (reflection amplifies noise)

Acoustic barriers:

• Fences, walls, or purpose-designed acoustic screens

• Height sufficient to break line-of-sight to receptors

• Absorbent materials on facing surfaces

Enclosures:

• Partial or complete enclosures around units

• Ventilated to ensure adequate airflow

• Lined with acoustic absorption

• Increases cost 20-30%, reduces efficiency 5-10% (restricted airflow)

Time controls:

• Night setback reducing compressor activity during sensitive hours (11pm-7am)

• Buffer thermal storage providing heating during quiet periods

Cost implications:

Basic installation (no acoustic treatment): Included in heat pump costAcoustic assessment: £1,500-3,000Acoustic barriers: £50-150 per linear metreAcoustic enclosures: £2,000-5,000 per unitLow-noise specification: +10-15% heat pump cost

Technical Design (RIBA Stage 4)

Detailed Specifications:

Heat Pump Equipment:

Specify comprehensively:

Manufacturer and model:

• Exact model numbers (outdoor unit, indoor unit if split)

• Refrigerant type (R32, R290, other)

• Electrical supply requirements (single/three-phase, current)

Performance data:

• Rated output at design conditions (-3°C ambient, 35°C flow)

• COP at design conditions

• Seasonal performance (SCOP/SPF)

• Sound power and pressure levels

Controls:

• Weather compensation (outdoor temperature sensor adjusting flow temperature)

• Smart controls (smartphone apps, remote monitoring)

• Legionella cycle programming

• Defrost cycle management

Accessories:

• Buffer vessels (if required for system stability)

• Filtration (if water source)

• Glycol antifreeze (if risk of freezing)

Distribution Equipment:

Full specifications for low-temperature distribution:

Radiators/emitters:

• Type, size, output at low temperature (45°C Δt50/30)

• Positions in each room

• Thermostatic radiator valves (TRV) or other controls

Underfloor heating:

• Pipe spacing (100-200mm typical)

• Screed depth and specification

• Insulation beneath (minimum 100mm)

• Manifolds and actuators

Pipework:

• Pre-insulated pipework for external runs

• Sizing for low temperature/high flow rates

• Expansion provisions

Commissioning Specifications:

Testing requirements:

• Pressure testing (hydraulic, refrigerant circuits)

• Flow rate measurements (match design calculations)

• Temperature differentials (confirm heat delivery)

• Control operation (weather compensation, zone controls)

Performance verification:

• COP measurement at commissioning (compare to design)

• Indoor temperatures achieved during cold weather

• DHW reheat times

• Defrost cycle observation

Building User Guide:

Comprehensive guidance for occupants:

Heat pump operation:

• How system differs from gas boiler (lower temperatures, slower response)

• Controls explanation (avoiding frequent adjustments)

• Seasonal settings (heating/cooling changeover if reversible)

Maintenance requirements:

• Annual service necessity (qualified engineer)

• Filter cleaning (if air handling units)

• Outdoor unit clearances (prevent obstruction)

Troubleshooting:

• Common issues and resolutions

• When to call engineer

• Warranty and support contacts

Energy efficiency advice:

• Optimum thermostat settings (consistent temperature better than frequent changes)

• Night setback appropriate levels (1-2°C, not full off)

• Summer shutdown if cooling not required

Cost information:

• Expected electricity consumption

• Monitoring via smart meter or heat pump display

• Comparison with previous heating costs

Post-Construction Verification

Commissioning and Testing:

MCS Commissioning:

If MCS-certified installation (required for UK grants/incentives):

Checklist includes:

• Design heat loss calculations confirmed

• Specified equipment installed

• Flow rates measured and correct

• Controls programmed correctly

• Performance test at design conditions

• Building user training completed

Record:

• MCS certificate issued

• Performance data recorded

• As-installed drawings

• Commissioning sheets signed off

BREEAM Evidence:

For final BREEAM assessment:

Design stage evidence:

• Heat pump specifications with performance data

• Zero fossil fuel confirmation (M&E drawings showing no gas/oil)

• Acoustic assessment (if sensitive receptors)

• MCS Heat Pump Calculator outputs

Post-construction evidence:

• MCS certificate (if applicable)

• Commissioning records

• Performance test results

• As-built M&E drawings confirming design implemented

• Building User Guide including heat pump operation

Operational Monitoring:

Version 7 increasingly requires operational performance demonstration:

First heating season monitoring:

• Monthly electricity consumption

• Indoor temperatures achieved

• Occupant feedback (comfort, noise, satisfaction)

Performance metrics:

• Actual SPF compared to design prediction

• Electricity costs vs projections

• Maintenance issues encountered

Reporting:

• Annual report to BREEAM assessor (Outstanding projects)

• Corrective actions if performance below design

This monitoring requirement ensures heat pumps perform as designed, not just specified on paper.

Version 7 Air Quality FAQ

Can we achieve Outstanding with "hydrogen-ready" boilers instead of heat pumps?

No. "Hydrogen-ready" boilers currently burn natural gas (fossil fuel), contradicting the zero fossil fuel requirement. Version 7 assesses heating systems based on what they use today, not potential future fuels.

If hydrogen infrastructure becomes available and the hydrogen is genuinely renewable (green hydrogen from electrolysis), BREEAM policy may change to permit hydrogen heating. Currently (2025), hydrogen-ready boilers are fossil fuel systems and prohibited for Outstanding.

What if gas boilers are significantly cheaper and we can't afford heat pumps?

Outstanding rating is not mandatory—it represents top 1% of buildings (innovator status). If heat pump capital costs prevent Outstanding, target Excellent rating instead:

Excellent permits ultra-low NOx gas boilers (≤40mg/kWh) achieving same air quality credits (3 credits) as heat pumps. Capital cost saving of £400,000-600,000 (residential) or £50,000-200,000 (commercial) typically.

Outstanding requires commitment to highest environmental standards including higher costs. Projects prioritising capital cost minimisation should target Excellent or Very Good realistically.

Do heat pumps always perform better in energy performance (Ene 01) than gas boilers?

Usually but not always:

Well-designed heat pump systems:

• SCOP 3.0+ with enhanced building fabric

• Lower carbon emissions than gas boilers (current UK grid)

• Score significantly better in Ene 01

Poorly-designed heat pump systems:

• SCOP <2.5 with standard building fabric

• May score worse than efficient gas boilers

• Particularly if electric backup or direct electric heating relied upon

Version 7 heat pump minimum performance standards (SCOP ≥2.8) prevent worst-performing systems, but proper design remains essential. Heat pumps don't automatically achieve better energy scores—must be properly specified and integrated with building design.

Can we use biomethane or "renewable gas" to achieve Outstanding?

No. Biomethane from anaerobic digestion, whilst renewable, involves combustion producing direct emissions. Version 7 treats all combustion as fossil fuel for Outstanding purposes, regardless of fuel source carbon intensity.

The focus is eliminating combustion air quality impacts (NOx, PM), not just carbon emissions. Renewable combustion still produces local air pollutants contradicting Outstanding's zero direct emission requirement.

If biomethane becomes genuinely zero-emission through technological advances (unlikely for combustion), BREEAM may reconsider. Current policy treats all combustion equally.

What about district heating from waste-to-energy (incineration)—does that qualify for Outstanding?

Depends on central plant emissions:

Plant emissions ≤40mg/kWh: Building achieves 3 credits, permitted for OutstandingPlant emissions >40mg/kWh: Building achieves fewer credits, Outstanding not achievable

Waste-to-energy plants typically emit 100-300mg/kWh NOx, preventing Outstanding for connected buildings. However, connection may still be mandatory under planning policy for other reasons (waste hierarchy, renewable energy).

If Outstanding is essential, district heating from waste incineration prevents achievement—require alternative heat sources or different plant technology.

Our building has small gas cooking load (<3% total energy). Can we get exemption for Outstanding?

Potentially, through BREEAM Bespoke assessment:

Requirements:

• Cooking demonstrably <5% total building energy use

• All other heating (space, water) uses zero-emission systems

• Genuine technical necessity for gas cooking (not just preference)

• Application to BRE technical team with justification

Likelihood:

• Exemptions rarely granted (bar is high)

• All-electric commercial kitchens proven viable in most applications

• "Chef preference" insufficient justification

Most projects should plan all-electric kitchens for Outstanding rather than rely on exemption approval. Only pursue exemption if genuine technical necessity demonstrated.

Does the fossil fuel ban apply to existing buildings doing BREEAM Refurbishment?

Version 7 Refurbishment & Fit-out (releasing 2026) will apply similar principles with flexibility for existing building constraints:

Outstanding Refurbishment:

• Zero fossil fuel target but exemptions where heat pumps genuinely not viable

• Must demonstrate comprehensive feasibility assessment

• Partial solutions acceptable (heat pumps for most spaces, limited gas where unavoidable)

Excellent Refurbishment:

• Ultra-low NOx gas permitted (≤40mg/kWh)

• Recognises existing buildings have constraints not present in new build

Full Version 7 Refurbishment guidance releases 2026—current indication is pragmatic approach recognising retrofit challenges whilst maintaining decarbonisation direction.

Get Expert Version 7 Air Quality Support

Version 7's fossil fuel prohibition and heat pump requirements create substantial complexity for projects targeting Outstanding. Heat pumps require integrated design approach fundamentally different from gas boiler systems, with implications for building fabric, distribution systems, electrical infrastructure, and acoustic design.

Our team provides air quality assessment and heating strategy support for Version 7 compliance:

Strategic Services:

• Outstanding rating achievability assessment (can heat pumps work for this building?)

• Capital cost comparison (heat pumps vs ultra-low NOx gas for Excellent)

• Rating target recommendation based on site constraints

• Version 7 vs Version 6 decision support

Technical Services:

• Heat pump feasibility assessment (building fabric, plant space, electrical capacity)

• Heating strategy selection (individual vs communal, air vs ground source)

• Integration with building design (working with architects and M&E engineers)

• Acoustic assessment for heat pump noise compliance

Air Quality Assessment:

• Construction dust risk assessment (IAQM guidance)

• Air Quality Neutral assessment (London Plan Policy SI1)

• Coordination of heating specifications with planning air quality requirements

BREEAM Evidence Preparation:

• Air quality credit evidence package

• Heating system specifications and performance data

• Acoustic assessment reports

• Commissioning and monitoring requirements

Post-Construction Support:

• Heat pump commissioning verification

• Performance monitoring and reporting

• Building user guidance preparation

Based in London and operating throughout Kent, Essex and Scotland, we provide rapid response for Version 7 air quality compliance. Our team understands both BREEAM technical requirements and practical heat pump implementation, ensuring specifications are buildable and achieve designed performance.

We work closely with mechanical engineers, providing environmental assessment input whilst respecting M&E design leadership. Our role supports rather than duplicates M&E work, adding BREEAM-specific expertise and air quality assessment capability.

Contact us to discuss Version 7 air quality requirements and heat pump strategies