the problem with zero carbon building as a goal
TRANSCRIPT
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Is Zero the right target for buildings?
Nick Grant Independent Passivhaus Consultant. @ecominimalnick
Are Buildings the right target for Zero?
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Flawed logic
• We have to achieve >80% CO2 reductions ✓
• We need new buildings ?
• Therefore all new buildings must be zero carbon (some say negative) ✗
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Fundamentally Flawed
• The building is the wrong boundary
• Forces biomass and/or inefficient building mounted generation
• Typically compromises building efficiency
• Definition is proving elusive!
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Boundaries • Why choose the building?
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The most correct boundary but impractical for daily calculations
All boundaries are wrong, some are useful (after George Box)
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or
or
Imagine idealised renewable but finite fuel
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Zero C limited options: • Bio-oil/gas - finite resource, if we use it then
not available for others"
• Wood fuel - loss of carbon sink/renewable resource, pollution, deforestation, food, peak wood revisited"
• PV - why on the building?"
• Micro wind - finally discredited."
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Some of the Issues: • Accounting paradox - how to calculate saving from efficiency if the
energy source is considered to be zero Carbon?
• Economy of scale - energy generation more efficient at bigger scale & right location.
• Opportunity cost - finite budget and time means efficiency suffers if time and money put into ZC tech'.
• Doesn't solve peak load - mismatch with demand, diurnal & seasonal.
• Arbitrary - how much ZC kit do we install to achieve zero given large variation in behaviour?
• Longevity - lifespan, maintenance?
• Confusion and distraction - Red herring, smoke and mirrors!
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Why stop at energy?
• Waste neutral.
• Water neutral.
• Food neutral.
• Etc.
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Conclusions:
• The building is the wrong boundary for global or National carbon accounting.
• If the energy can be exported it's nothing to do with the building (Bill Bordass).
• Zero carbon buildings - just because they are possible doesn't mean they are sensible.
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Recommendations • Set building energy consumption targets.
• Set PE values of exportable energy at the pool/grid value. PV, biomass, bio-gas.
• Evaluate and reward energy generation independently of the building. Don't assume buildings are the best place for a power station or that householders are the best people to manage them.
• If you are going to tax new buildings be honest about that and make it an efficient tax!