Climate change is one of the biggest threats we face today. Clearly we need to reduce CO2 emissions globally to zero, or to less than zero, to address climate change. And architecture in the anthropocene must change to address this challenge, as I have written about in my manifesto. Buildings must emit radically less CO2 during construction and occupation. This often leads to the assumption that we should be delivering ‘Zero-Carbon Buildings’. However, this is the wrong target for buildings, radical energy efficiency is the right target for buildings.

In this blog post I explore 9 reasons why ‘Zero-Carbon Buildings’ is the wrong target and what the right targets are.

012 Zero Carbon Buildings Wrong Target

By the way, this is not a tongue-in-cheek post like a previous post, ‘Zero Carbon’ is a very serious issue, particularly in the UK where it is likely to be the legislated requirement for all new buildings soon. Going down the wrong path will have very serious consequences for us all.

1. What exactly are ‘Zero-Carbon Buildings’?

There is no one clear definition for ‘Zero-Carbon Buildings’, and it is sometimes mixed up with the idea of a ‘Net Zero Energy Building’. In the UK there is an official definition given by the Zero Carbon Hub for a ‘Zero Carbon Home’ but there is no official definition for non-domestic buildings yet.

Even so, the definition for a ‘Zero Carbon Home’ excludes plug loads (that is, unregulated energy consumption such as appliances, computers, TVs and entertainment equipment etc..) and includes the concept of “allowable solutions” to offset (or pay for offsetting) a portion of the CO2 emissions of the home. This means that a ‘Zero Carbon Home’ will continue to emit CO2, in some cases notionally offset by ‘allowable solutions’ and in other cases simply not accounted for.

This clearly acknowledges that in many cases it will not be practical or economic to supply all the energy needs of a house with on site carbon neutral energy generation so some form of offsetting (or omission from the accounting!) is needed to balance the equation to zero.

Defined energy consumption targets for heating / cooling (See point 9 below) and for complete energy consumption would bring clarity and certainty to the industry and building occupants.

2. ‘Zero-Carbon Buildings’ are not an efficient use of resources

Without a doubt, we need to urgently scale-up renewable energy generation and radically reduce the CO2 emissions of energy generation. However, at the scale of a single building, especially a house, renewable energy generation is expensive and inefficient use of materials and technology. Photovoltaic systems, wind turbines, hydroelectric power stations are more efficient and cost effective at a larger scale than a single building.

And when these technologies are installed on a building there is an opportunity cost incurred. The same money would in many cases be better spent on increasing the building energy efficiency and thereby reliably reducing CO2 emissions by design. Building energy efficiency is more resource efficient, can radically reduce CO2 emissions and almost always has the best return on investment.

It is less costly and more effective to consume radically less energy and emit less CO2 by design, rather than to meet higher energy demand with building mounted ‘Zero-Carbon’ renewable generation.

3. ‘Zero-Carbon Buildings’; only in the right location?

Not all locations are suitable for generating renewable energy, that is, for a building to be a power station. And therefore not all locations will accommodate buildings that can be ‘Zero-Carbon’.

Urban locations often come with multiple constraints imposed by the surroundings. The proximity of adjacent buildings may rule out wind turbines. The same buildings may shade the site compromising opportunities for photovoltaic systems. And in urban locations, how often is hydroelectric generation a realistic option?

The other aspect most commonly associated with urban locations is density. A high-rise apartment building or office block has considerable energy demand but limited land, or roof-top area, to match demand with on-site renewable energy generation.

Rural locations may seem to offer good conditions for photovoltaic systems, wind turbines or hydroelectric generation to all be considered. However, even then site constraints will often rule out or reduce the effectiveness and efficiency of these systems.

This raises the question; if one location is particularly suitable for renewable energy generation, should a (grid-tied) building in this location be potentially counted as ‘Zero-Carbon’, effectively penalising buildings in less-suitable locations? Or would it be better if the renewable energy generation from this location counted towards reducing the over all CO2 emissions of the energy grid?

“Just because we are lucky enough to be building next to a river with a small hydro plant doesn’t make our building zero carbon.”

– Nick Grant

Renewable energy generation and hence ‘Zero-Carbon Buildings’ are very location and site dependent. Building energy efficiency works reliably in all locations, on all sites.

4. ‘Zero-Carbon Buildings’ may increase national CO2 emissions

‘Zero-Carbon Buildings’ require buildings to run predominantly on electricity since this is what all building-mounted or on-site renewable energy generation provides. There are some exceptions to this (solar hot water for example) but even then electrical systems still need to make up the majority of the building services. While there is a good match between the energy generated on-site and the energy demand this doesn’t necessarily present a problem. However, this is only likely to be part of any one day, and certainly only part of the year, and in many cases not consistent or reliable. There are several reasons for a mismatch and here are three:

  • Many buildings have significant performance gap, that is, how much actual energy is used in the building can be considerably more than what was predicted in the design. In this case the on-site renewable generation sized to suit the design may never keep up with the actual demand and the building will be constantly drawing electricity from the grid.
  • The time of the day when energy is being generated will not necessarily match when energy is required in the building. A house, for example, is likely to use more energy in the early morning and in the evening during the week, while photovoltaic system is more likely to generate electricity during the middle of the day.
  • Energy demand is at it’s greatest in winter when buildings need more light and heat. Unfortunately many renewable energy systems generate the least during winter. This has a significant impact in the UK particularly where the majority of heating to buildings is currently provided by gas.

The problem with this mismatch is that it leads to more demand on the national electricity grid. And in UK, as in many other countries, the electrical grid is actually quite carbon intensive. That is to say, using electricity from the grid emits more CO2 than using on-site renewable generation. It also emits more CO2 than using (conventional) natural gas. This is due to the amount of coal burning power stations that provide electricity for the grid in the UK. Coal has roughly twice the CO2 emissions than (conventional) natural gas.

So electrically heating a ‘Zero-Carbon Building’ in winter may in fact emit more CO2 than heating an energy-efficient building using (conventional) natural gas! Multiply that across several ‘Zero-Carbon Buildings’ and national CO2 emissions rise.

Genuine building energy efficiency reduces energy demand and consumption, and thereby CO2 emissions, regardless of the energy source.

5. ‘Zero-Carbon Buildings’ don’t reduce peak demand on the national grid

Continuing on from the previous point, ‘Zero-Carbon Buildings’ actually put more pressure on the national electricity grid a certain times. And it happens right when the grid is under the most pressure already, at peak demand.

In the dark freezing depths of winter, with a gale howling outside, everyone has their heating turned up high and all the lights switched on … and since the sun isn’t shining the photovoltaic systems on the ‘Zero-Carbon Buildings’ aren’t generating electricity. And since the wind is gale force and highly changeable the wind turbines have switched to safety-mode and aren’t generating electricity! So all the ‘Zero-Carbon Buildings’ are back to drawing electricity from the national grid, like every other building. And if the ‘Zero-Carbon Buildings’ are only mildly above-average energy efficient, they present quite a demand for electricity!

We could hope that this type of scenario would never happen in a country where peak demand is in the height of summer. However, on a very hot, still evening, just after the sun has gone down, everyone wants the lights and entertainment on, along with some comfort cooling… the renewable generation isn’t there to match demand.

There are two key issues with this. Firstly, CO2 emissions go up as covered in the previous point. Secondly, the national grid might not be able to cope as peak demand exceeds generating capacity! The amount that generating capacity exceeds peak demand, known as the “capacity margin”, is already shrinking in the UK, as older power stations are decommissioned without new generation being created at the same rate. The possibility of electrical blackouts in the near future is already being raised, even without more ‘Zero-Carbon Buildings’ compounding peak demand further!

See for example the report: “GB Electricity capacity margin” published by the Royal Academy of Engineering (RAE) in October 2014 for the prime minister’s Council for Science and Technology and reported in the press for example here and here.

‘Zero-Carbon Buildings’ do not reduce peak demand on the national electricity grid, building energy efficiency does.

6. ‘Zero-Carbon Buildings’ need to generate more than just their own demand

To actually balance CO2 emissions ‘Zero-Carbon Buildings’ need to generate much more than just what they use. As discussed in point 4 above, the national electricity grid is carbon intensive; in addition there are also losses in generating and distributing the electricity. For for every unit of electricity consumed in a building in the UK, 2.56 units (based on Provisional SAP2012 values, PDF) of energy needs to be consumed at the power station just so that a single unit gets to the building. When this is put into CO2 emissions terms it gets even more complicated. However, the basis remains the same: using electricity from the grid emits more CO2 than using on-site renewable generation. It also emits more CO2 than using (conventional) natural gas.

‘Zero-Carbon Buildings’ must generate enough ‘Zero-Carbon’ electricity to export to the grid to cover the actual consumption at the building, and to cover the additional CO2 emissions from when the building uses electricity from the grid. Complex unreliable offset accounting is required to actually get to ‘zero’. In contrast to this, using less energy in the first place is simple and reliable and doesn’t require any offset accounting.

‘Zero Carbon’ energy generation that feeds into the national electricity grid actually helps reduce the carbon intensity of the grid and hence CO2 emissions. However, buildings should be measured by energy consumption, and not by energy generation.

Radical building energy efficiency ensures less energy needs to be generated and therefore less CO2 is emitted.

7. ‘Zero-Carbon Buildings’ are the wrong scale for repairs and maintenance

‘Zero-Carbon Buildings’ sounds perfect doesn’t it? A lovely round ‘Zero’ for each building. Until you have to maintain or repair the renewable energy generation system yourself. Or pay someone to do it for you.

When each individual building is treated as a power station, this is what we face: a hugely inefficient and unreliable repair and maintenance requirement. Economies of scale that community level or national level power stations benefit from are lost. So is the specialist workforce that looks after larger scale power stations. Or at least a major shift has to take place, but even then individual building owners will need to pay for repairs and maintenance. Or the ‘Zero’ will soon change to another number as systems lose efficiency, break down and fail, matched by CO2 emissions rising once again.

Should we really rely on individual homeowners to ensure that energy generation is ‘Zero-Carbon’? How about relying on school or local authority caretakers and maintenance teams? Corporate landlords? Not that these individuals and organisations aren’t necessarily capable and willing, probably many are. But should they be held responsible for a building’s CO2 emissions? Is this a sensible and reliable way to radically reduce CO2 emissions for the country? For the world?

And while a distributed energy generation system may hold many advantages, there is a sensible scale for it. Arguably this is not at an individual building scale.

Renewable ‘Zero-Carbon’ energy generation should be at a scale where repairs and maintenance can be reliably and efficiently managed.

8. ‘Zero-Carbon Buildings’ is an abstract and unreliable idea

People don’t emit CO2 when they occupy and use buildings; they consume energy. Which is why we pay for energy. And although there are people doing great work to help us visualise and understand our CO2 emissions, it remains abstract. In contrast we understand energy use as we can see the direct results of it; the light comes on or off, the laptop boots up, the toast pops up, etc.. And we know how to reduce our use of energy through a variety of means. Consuming less energy is a concrete and understandable.

Balancing out how much renewable ‘Zero-Carbon’ energy is consumed, how much is offset against carbon-intensive grid consumption and what this means in terms of CO2 emissions is complex and abstract. It’s also unreliable as there are many different and changing factors involved. When energy is used, the source of the energy and what it is used for, can all impact on the actual CO2 emissions. Add offsetting between these into the mix and the complexity increases even further!

People, understandably, often don’t realise or appreciate these complexities. This can lead to an assumption that renewable energy is free, unlimited and ‘Zero-Carbon’ and therefore there is no problem with consuming far more of it! Clearly from the points above, this is highly problematic and can quickly lead to increasing CO2 emissions. Unfortunately the atmosphere and climate doesn’t appreciate the irony of this!

Energy consumption targets are simple, understandable and reliable, whether for buildings or other areas of energy consumption.

9. Are ‘Zero-Carbon Buildings’ always comfortable?

Balancing energy demand and generation doesn’t inherently provide any comfort for the people who occupy the building. A leaky old shed or a tent could notionally be ‘Zero Carbon Buildings’ provided energy demand is balanced by building-mounted or on-site ‘Zero-Carbon’ energy generation.

To their credit the Zero Carbon Hub in the UK includes a ‘Fabric Energy Efficiency Standard’ within the definition of ‘Zero carbon Homes’. This means that the building fabric must achieve required levels of thermal insulation and airtightness, among other factors, to ensure a maximum space heating and cooling energy demand isn’t exceeded. This does ensure a certain level of comfort should be provided, however, in the absence of specific comfort requirements it is hard to be certain what level of comfort.

Why does comfort matter for climate change? Well, buildings are intended for people, and therefore need to be comfortable to be functional. If people are not comfortable, they adjust the heating, cooling, ventilation or other building services and systems to attempt to be comfortable. This increases energy consumption and in most cases CO2 emissions. This is part of the issue with the performance gap (between design predictions and reality) of buildings mentioned earlier.

So ‘Zero-Carbon Buildings’ that are, for example, draughty, rely on opening windows for winter ventilation, or over heat, will see energy consumption rise as people make adjustments to be comfortable.

Stringent space heating and cooling energy targets along with comfort targets ensure that the building fabric has to do the majority of the work. The building fabric, which will last the lifetime of the building, will be highly energy efficient and ensure a comfortable building by design, regardless of how and where the required energy is generated.

Radical building energy efficiency can ensure a comfortable building and reliably low CO2 emissions for the lifetime of the building.

Not ‘Zero-Carbon Buildings’, Radically Energy Efficient Buildings

I certainly feel very strongly that we need to radically reduce CO2 emissions globally. And I feel it is very true that global or national targets are just too big to grasp without feeling overwhelmed. This is particularly so when it comes to something as abstract as CO2 emissions, regardless of how concrete the consequences are. So it is important to focus on doing what we can at a scale that we can understand and approach without getting overwhelmed.

For architects and their clients, and others in the construction industry, the right scale is almost certainly at a single building, site or project scale. However, we should be focussed on radical energy efficiency, not on balancing complex CO2 accounts.

Passivhaus Standard buildings are radically energy efficient and ensure very low CO2 emissions over the lifetime of the building. And importantly, passivhaus buildings match this with simplicity, comfort and reliability.

I will be returning to the subject of ‘Zero-Carbon Buildings’ again in the near future so please subscribe by email (just below my photo and profile) to get future blog posts direct into your inbox. Well, a teaser anyway, it’s never a full length blog that gets emailed out!

Acknowledgment: The Hanover 2012 paper “Is net Zero the right target for buildings?” by Nick Grant was my reference for several aspects of this post, for which I am very grateful. You can download the paper (and others) from here. I highly recommend it.

30 thoughts on “Zero-Carbon Buildings? It’s the Wrong Target

  1. Excellent blog summarising the argument very well, better not to use energy rather than pay to generate it. Your point about maintenance is also very well made. i live in a new purpose built apartment block with a large solar thermal array on the roof. It doesn’t work, it can’t because it is incorrectly designed and has clearly never been commissioned. Despite being a requirement of building regulations and a planning requirement no one cares if it works. Planners have taken the carbon “saving” and have no interest performance. We are deluding ourselves about these carbon targets.
    In every building we design as far as planning then “value engineer” the project, purchasing products bought at the cheapest price to build something that looks like the design but is not. Each small change contributing incrementally to the performance gap. If it were a car sell a VW Golf and deliver a Skoda – might be a good car but not what you bought.
    Until we start to build to design the performance gap will never be closed.

    • Thanks David, I really appreciate you sharing your personal experience and thoughts.

  2. Elrond
    Agree with everything you say and efficiency should unquestionably be the starting point. A few thoughts:
    – Its good to see directly where your energy comes from then you value it. If its remote and down a wire you don’t.This is the problem our children have if they had to cycle a few hours to put the lights on they’d use it wisely. Community scale is about as large as i’d go.
    – You generally clad a building at cost so why not in part with naturally abundant silicon (PV)
    Trees grow everywhere and can sustain themselves individually why can’t we? It fascinates me my 30 year old solar powered calculator still works after no maintenance – just a matter of up-scaling and mature battery technology coming soon?
    Good stuff!

    • Hi Neil, thanks for your comments.

      – I agree it is good to see a closer relationship and proximity between production and consumption, and not just for energy. I went and visited many hydroelectric power stations and geothermal power stations myself growing up in NZ! 🙂 It does only apply to something that is genuinely good and useful though, which in some cases, where the site, location, orientation and economics all agree, might be building-mounted renewable energy technology or on-site renewables, but not as a blanket requirement and not as a priority over reducing consumption first. The same applies with food; it’s good to grow your own and to compost but more important to waste less first, regardless of the source. And like energy, is it realistic or even useful to expect everyone to be self-sufficient on their own plot of land?

      – Silicon as a raw material might be abundant, but not all elements used in PVs are (the required heavy metals / rare earth elements are getting increasingly scarce in fact and raise all sorts of ethical and environmental issues!) and PVs are energy intensive to manufacture and get to site. So again, where the site, location, orientation and economics all agree, yes on occasion PV might be a suitable as a form of roof or potentially wall cladding.

      – Trees are a great analogy! Some do grow in many places (not quite everywhere but I’m sure you didn’t mean it literally) however, different trees are adapted to different locations and conditions. And in every location they are part of a wider ecological network, and take in the energy they need from different sources. And while trees are perhaps ‘Zero Carbon’ over their entire lifespan, over the course of a single year they are not likely to be. They are more likely to be net absorber of CO2 annually while they are young (so maybe young trees will be defined as an “Allowable Solution”!) and possibly even when they are older, then becoming net emitters of CO2 (or methane) when they die and rot. Incidentally this is a good reason to use timber in buildings and lock the CO2 the trees have absorbed into the structure before the trees die and rot.

      Good point about the calculator, maybe so, if indeed the technology does scale. Maybe it means we need buildings to operate of DC power rather than AC though to eliminate the need for inverters, which are one of the main items that need maintenance and/or replacement at regular intervals!

      Cheers, Elrond

  3. Elrond,
    You have written a great, enlightening article here. I think we have mis-marketed the “zero” anything. We have an obligation as professionals to educated the clients and communities to a notion of “neutral” as we develop the trek back to an environmentally productive structure. Net neutral carbon also relieves this fatigue of a diet that we all know we need while easing us into the marathon that our species must begin to train for. I taught a class where we compared indigenous structures to those of the last 50 years (including the LEED platinum types here) and were often surprised that their technology was more sustainable yet would not meet the standards of inclusion to the USGBC. This gave me concern that our notion of sustainability was a bit off but could eventually make it to a new “restorative” design (living building challenge is getting close). I really like the transparency you are presenting here and hope to see a constructive discussion on the future of the marathon we are starting.

    • Hi Sean,

      Thanks for your comments – a marathon indeed!

      ‘Sustainability’ is really the mid-point on a sliding scale between destructive and restorative, or contributory, ways of building and living. As you say, the Living Building Challenge is getting close. Unfortunately it suffers from the same problem of ‘Zero-Carbon Buildings’ in drawing an arbitrary system boundary at the edge of the building or site, which may sometimes make sense but often doesn’t. It’s not where we locate the boundary for most other systems we operate within (economic, social, etc) and most other system boundaries have degrees of porosity and flexibility.

      Cheers, Elrond

  4. “People don’t emit CO2”

    I’m sorry, you can’t expect building science geeks to let that pass. 😉

    My pedantry aside, great article. Your points apply to the various definitions of “Net Zero Energy” in the US as well.

    There are of course benefits to distributed power generation: resiliency, less transmission loss, etc. These need to be quantified and subject to cost benefit analysis and not hidden under the magic number ZERO, though.

    • Haha, great spot there Greg, clearly I was holding my breath when I wrote that line! (Corrected now thanks!) And yes, you’re right almost all the same points apply to ‘Net Zero Energy Buildings’.
      Thanks, Elrond

  5. Hi Elrond – another good blog!
    10th reason: I think stressing that currently a building only has to be ‘zero carbon’ for 30 years makes the case also for building fabric efficiency – which last beyond the 30 years. Also, the greater the energy need, the greater the embodied energy of the PV array or renewable plant – which will need to be replaced usually within the lifespan of the building, even on just a 30 year lifespan. One good thing about the Uk’s zero carbon definition is that it will have to be ‘as designed’ – so that David Frise’s story above where renewables are put just to meet planning requirements, but in effect do not generate any energy, are – hopefully – less common. In just 18 months we are supposed to design and build dwellings to this ‘zero carbon standard’, we do not yet know what this entails. Why not a more ambitious fabric target? Though you can do this voluntarily ofcourse – but it will be cheaper at present for a developer to pay into a ‘community fund’ to offset predicted remaining CO2 emissions than it is to by extra insulation say and not create the extra energy use ( and hence emissions) to begin with – a topsy-turvy world!

  6. This is a great blog post Elrond but I think a little clarification might help for section 6.

    You write: “For for every unit of electricity consumed in a building in the UK, 2.56 units (based on Provisional SAP2012 values, PDF) need to be generated at the power station just so that a single unit gets to the building.”

    This confuses two important concepts: the primary energy factor, and transmission and distribution losses. It might help to separate them out.

    Primary energy factor – the units of primary energy used to generate a unit of electricity. In the case of fossil fuelled power stations this is the units of thermal energy provided by burning coal, oil or gas in order to generate 1 kWh of electricity. This is your figure of 2.56 taken from SAP, which will be an average across the whole grid, taking into account the mix of primary fuels used.

    Transmission and distribution losses are the losses that occur in delivering the electricity through the grid from the generator to the end-user. If the losses in the grid are 8%, then 92kWh is delivered to end-users for each 100kWh generated.

    Hope this is useful.

    best regards, Tom

    • Thanks Tom that is a useful clarification, and I might edit that sentence to make it clearer that it is consuming 2.56 units at the power station to create 1 unit at the building, rather than generating 2.56 units. However, the Primary Energy Factor does include transmission and distribution losses, to quote from the referenced document; “the system average value for grid supply energy takes into account transmission and distribution losses…”
      best wishes, Elrond

  7. I appreciate the very thoughtful article, Elrond.

    My comment would be about definitions. Specifically, one tool you use implicitly is the engineers’ control volume approach. Namely, your focus tends towards a control volume around a national or at least regional grid area. If one tracks all energy or materials entering and leaving a control volume, one can well determine the net balance or flux of energy and materials. Advocates of net-zero buildings want to draw their control volume around the building or the building and grounds. Of course in the case of GHG pollution, the ultimate relevant scale is global. One obvious application is that energy enters and leaves all terrestrial control volumes in the form of sunlight, reflection, and black body radiation. At most meaningful scales short of global, wind is a relevant form of energy to consider in the balance and geothermal and water motion provide harvestable power. Chemical power use should be as near zero as possible because these forms generate very slowly in nature, until you consider plants.

    Second, I would invoke the related concept in ecology of carrying capacity of an ecosystem. The relevance is that all ecosystems have some finite carrying capacity for most stresses. This can be very tricky to determine as there are years of abundance mixed with years of stress or drought. An ecosystem may appear to continue in healthy fashion for years before a stress tips the system into imbalance. Die-offs and even extinction may result.

    Third, the special case of a hydrologic watershed is particularly relevant to the water cycle and its availability for power and consumptive uses. All of these tools reveal disruptions and change due to observed climate changes. Because of these disruptions and changes, statistical modeling using all of these tools will be less accurate going forward, leading to increased societal risks.

    I realize that my mention of these definitional tools is basic and may be tedious, but the great utility of these tools in engineering planning in the past 150 years is threatened. This leads to an engineering crisis because these effects are unprecedented. The disruptions to my field of engineering hydrology are just one manifestation. How does one protect life from a 100-year or 500-year flood or drought when the data are not statistically stationary? Similarly, how does an electric grid planner design for peak use when unprecedented extremes come with greater frequency? How do we predict any consumption pattern accurately under these conditions? This unpredictability will lead to waste, thereby exacerbating the problem. The biggest waste will be ecosystem disruptions leading to extinctions. We are fools if we think that humans will escape these conditions unscathed. Indeed, many humans will die, with the poor always most vulnerable. However, extreme weather events are notoriously powerful and universally destructive. How much insurance can you afford? Which insurance pool will cover the new actuarial realities? Will reinsurance need to become a matter of national or global policy?

    As we consider buildings as the largest source of GHG emissions in developed societies, we must consider the largest liquid chemical consumer of fossil fuels: transportation. Namely, buildings must increasingly be outfitted for electric mobility.This will increase overall electricity consumption, with the benefit that electric vehicles (EVs) are 3 to 4 times more efficient than ones equipped with internal combustion engines. Another change this will bring is to change the timing of electricity consumption. An opportunity arises in that batteries for EVs are then available to smooth grid demand. This can help to address the dreaded evening peak demand. The addition of connected storage can increase the utility of renewable sources of electricity, too. Mobile batteries can be useful in addressing outages, too.

    So, you have identified the issue in terms of the difficulty of finding a useful and affordable approach to zero-carbon buildings, citing the need for scale in generation options and conservation and efficiency in the building envelope. I agree, but in addition there is a great need for aggressive global action at all scales before the basic tools of engineering in our society become ever more difficult and inaccurate to use. To design robustness in will lead to increasing waste, exacerbating the problem. However, new opportunities to smooth the grid come from EVs connected to buildings. The train is leaving the station; who will get on board?

    • Dear Terry,

      Thank you for your thoughtful in-depth comment. You are right about the “control volume” aspects, I have referred to this as “system boundaries” in a previous comment.

      The role of EVs in the future picture is a complex one and another reason that having control volume or system boundary at the building or even site boundary is highly questionable.

      Best wishes, Elrond

  8. Many of those points are excellently put and deserve wider readership.

    I just would add one thought.
    We have two energy distribution systems ; Gas and Electricity. A shipload of gas going into electricity generation at a power station generates roughly 0.4 shiploads worth by the time it is used as electricity in the home. I do not know the equivalent for the gas distribution network but I am guesing that a shipload of gas pumped into the gas national grid delivers at least 0.8 shiploads of energy at the domestic home.

    ADD to that the Combined Heat and Power units (burn gas, generate heat plus surplus electricity) wich actually pump out electricity at times of peak demand (the converse of solar) and you have a double bubble, surely?

    There can be no argument against producing well insulated and comfortable homes but chasing the rainbow by beleiving that we can have zero energy input is just plain counter-productive. We should ally good design with efficient energy inputs.

    • Dear John,
      Thanks for your comment. Referring to the same document that gives the primary energy factor for mains electricity in the UK as 2.56, mains gas for domestic consumption has a primary energy factor of 1.126. The electricity factor includes all sources, so burning coal, burning natural gas etc. So your “shipload of gas” figures translate to 0.39 and 0.88, pretty much as you suggested!
      Best wishes, Elrond

  9. This post makes fantastic points, but also harbors an overarching, implicit fallacy. In support of the great points made:

    Point 1: The definitions employed by “Net Zero Energy Buildings” and “Zero Carbon Homes” also ignore the carbon emitted (and carbon sequestration stopped) in the process of constructing the facility in question. Shipping materials and the use of energy for on-site construction and off-site fabrication are two examples of carbon emitted by construction. Wood harvesting without adequate replanting is an example of carbon sequestration stopped by construction.

    Point 9: Even when facility occupants refrain from (or are prevented from) adjusting interior climate and lighting controls, an uncomfortable facility leads to less use (fewer lessees, more working from home) and to earlier renovation or replacement, consuming additional energy in the process. Uncomfortable facilities are also less efficient for business use, consuming more space and resources (including energy) to accomplish the same amount of work that can be accomplished in a more comfortable facility.

    Now the fallacy: In order to consider the article potentially influential, we must assume that patterns in current sustainability beliefs and practices are subject to the influence of logic and scientific evidence. In fact, sustainability is predominantly a religious movement that is primarily concerned with defending the orthodoxy of its slowly-evolving existing teachings (particularly when those teachings are opposed by logic and scientific evidence), with establishing hierarchies within the community of believers, and with persecuting non-believers and non-adherents within the believer community. A more practical way to promote change within the sustainability movement would be to a) create narratives that portray and encourage the desired ideas and actions as historical and current reality or as historical precedent in support of a nuanced evolution within the current orthodoxy, rather than to portray them as a significant change in belief or practice; b) to portray the desired ideas and actions as long-held beliefs and practices of the most widely-admired leaders of the orthodoxy and as actions and ideas typical of orthodox believers; or c) to shame believers into seeing the desired beliefs and actions as acceptable means of atonement for past sustainability sin or as new “stones” that can be thrown at non-believers.

    • Dear Sean,
      Thanks, great comments!
      The fascinating aspect of it here in the UK, and also in the EU, is that ‘Zero-Carbon’ or ‘Net-Zero’ are likely to be legislated requirements for all new buildings in the near future. So while these terms might have been exclusively used by ‘sustainability believers’ until recently, very soon they will be mainstream requirements that everyone must come to terms with, regardless of both beliefs and of logic / scientific evidence!
      Best wishes, Elrond

  10. Excellent post Elrond Burrell! The key points which you have elegantly assembled in this blog are exactly what I and many others have been trying to hammer home to clients for years.
    There is no point whatsoever in being led down the garden path by ex double glazing sales people who profess that by installing a renewable energy source, you will be saving the planet. The initial investment should be made on the fabric/construction of the building and energy usage of the utilities within the building. Then we can assess the best energy source for the property. No real difference can be made by installing renewable energy sources into an inefficient property. The national grid is renowned for its inefficient production of energy so the focus should be on building properties that have lower consumption in the first instance. Thanks again for the post.

  11. Hi Elrond, interesting article. I look forward to the zero carbon legislation coming into force and seeing how developers prioritise fabric efficiency over renewables. If fabric efficiency is the most cost effective way to meet the target, any economically minded developer should soon learn this. One question. You say in point 6 that “the national electricity grid is carbon intensive; in addition there are also losses in generating and distributing the electricity.” You go on to mention the high capital and burdensome maintenance of small-scale onsite renewables. What is the cost difference over the life of say a large scale PV system using up land area and looses 7% ( of its generation to distribution losses versus multiple roof-top systems that have minimal distribution losses because they are sharing their generation locally? I would have thought that the land cost alone would make a roof-top system more cost favourable. What are the maintenance costs of PV, is it simply a matter of ensuring the warrenties are sufficient?

    • Thanks Rob and some good questions.

      You still have distribution loses from on-site renewables as energy is generated when you don’t need it and therefore fed back into the national grid. The primary energy factor of the grid takes account of this and will need updating as more and more distributed renewable generation feeds into it.

      You are right about land cost at certain scales. It need not be PVs though, it could be wind generation. Also large agricultural building rooftops etc can host PVs where the scale, location, orientation etc makes more sense. And the key thing is that once a building is highly energy efficient, the energy needs are very small so can more easily be met by renewable generation, which where appropriate could be on the building or on the site.

      PV maintenance is a big topic! At the most basic level there is regular cleaning needed and replacement of inverters at 5 or 10 year intervals.

      Best wishes, Elrond

  12. Hello Elrond,
    Great article and I appreciate your strong passion for Passivhaus. The best thing about Passivhaus is that it gives us clearly defined standards to create a high quality building that has been designed to minimise energy demand and running costs, while providing the occupants with a high level of comfort. I don’t think I’ve ever seen anything that clearly describes how a home or building could be classed as ‘zero-carbon’. My interpretation of ‘zero-carbon’ is a sort of life cycle analysis that considers the birth (materials and manufacturing) and death (disposal) of the building as well as its normal use.

    With Passivhaus, the greatest emphasis is on fabric efficiency, which is achieved by just simply superinsulating and making the home airtight. You could build a Passivhaus using large amounts of concrete and expanded polystyrene that is cheap to run and emits low levels of CO2. On the other hand you could build a ‘zero-carbon’ home (leaky shed!) that is energy hungry and have large PV panels on the roof and a massive wind turbine in the garden. Personally, I wouldn’t like to go for any of these two, but if I had to pick one, I would choose the Passivhaus for better comfort and lower energy consumption.

    I respect your opinion and love reading your articles. I believe that it would have been far better for our Government to fully adopt Passivhaus years ago, than come up with sets of standards that are not clearly defined but creates low-quality housing and short-term monetary profit. This would have forced housing developers to make a bigger positive impact on the environment and our lives! We could have then gradually phased in more stringent controls that deal with the sustainability of materials used.

    I see the good intentions of the ‘zero carbon’ route but hope that when new legislation comes there will be a greater emphasis on fabric efficiency and the environmental impact of materials/products as well as energy consumption, water consumption, renewable energy etc.

    My ideal home would be a Passivhaus that is built with locally sourced sustainable materials. I’m not sitting on the fence of the Passivhaus v zero-carbon debate. I just think that Passivhaus is the ideal starting point if we are to seriously consider the environmental impact of housing and tackle climate change. But we can easily go one better by also using ‘greener’ materials, using locally sourced products, incorporating green roofs, etc.

    What is the specification of your ideal home?

  13. Elrond
    A great article. I have just sent an email to my local MP Stephen Williams who is the Parliamentary Under Secretary of State for Communities and Local Government. Amongst other things he is responsible for Building Regulations. This is what I said:

    I am a local constituent who met you a few months ago to discuss Building regulations (Part L) and Bristol green capital. I couldn’t help feeling after talking to you that you and your predecessors in your job were listening to the wrong people about building energy.

    You should be reading and taking note of things like this. For me the three key messages are:

    1. Distributed energy generation on buildings is inefficient in terms of capital cost, operational efficiency and maintenance regimes
    2. Electricity generation on buildings encourages use of carbon intensive electrical heating and hot water generation – ie can increase emissions
    3. Focusing on design of very low energy building fabric and then generating low carbon electricity in suitable locations at a reasonable scale is a much more cost effective and reliable approach.

    I’d be very pleased to hear your thoughts once you have read the blog post. Elrond Burrell is very well regarded in the low energy building sector and I believe he has got it right, where the Zero carbon Hub have got it wrong.


    We need people like Stephen Williams to listen to this message!


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