This is part 1 of a 3-part series on household emissions in NZ. This part looks at whole-of-life emissions from housing. Part 2 will do the same for household transport, and part 3 will tie them together (the implication being: it really matters where we build new homes).

Globally, we need to reduce greenhouse gas emissions by lots, and we don’t have very long to do it. New Zealand has its own targets and Heidi has written about Auckland’s C40 commitment to a 50% drop in emissions by 2030.

Here’s the Stats NZ breakdown for household consumption emissions, aka  their annual “carbon footprint”. It includes ‘indirect’ emissions from the manufacturing process, e.g. clothing or cars that were made overseas but sold to NZ households.

Source: “Greenhouse gas emissions (consumption-based): Year ended 2017”, Stats NZ. I’ve added in emissions from the construction of housing, which are actually categorised as “gross fixed capital formation” of “residential buildings” rather than household consumption. I divided the aggregate figures by 1.721 million households to get the average per household.

Transport stands out pretty starkly as the biggest contributor, but today I’ll focus on “housing and household utilities”.

Some recent research looks at the whole-of-life emissions from a typical detached house. Since it includes the construction as well as the operation of the home, it’s conceptually similar to the ‘direct plus indirect’ emissions measured by Stats NZ.

The researchers assume the house has a 90-year lifetime and is almost 200 square metres in size, which is bigger than the average existing house but pretty typical for a new one. The total emissions from the house over its lifetime are shown in the graph below:

The “upfront” emissions from building the house add up to 42 tonnes before the house is lived in (although if you allow for ‘biogenic carbon’ in the wood used to make the house, then this reduces to around 21 tonnes). The ongoing energy and water use, plus maintenance and replacement, add up to 231 tonnes over 90 years or 2.6 tonnes per year.

Unsurprisingly, building the home is a big part of the emissions: equivalent to 16 years of energy use/ water use/ maintenance. If you group construction with maintenance and replacement, then they are equivalent to 36 years of energy and water use. Even so, that’s under 30% of the lifetime emissions, so energy efficiency is very important.

The research was covered in a Newsroom article titled “new houses emitting five times too much carbon” – that’s based on the authors comparing the figures above to what they thought the target should be, using a top-down global carbon budget based on 2°C of warming (which as Heidi’s article notes, isn’t exactly comfortable).

The Newsroom article also quotes the authors:

“There are things we can do quickly to get the carbon down,” says Dowdell. “The big one is the house size. There is a close relationship between house size and carbon footprint.”

“Then, making houses more energy efficient, especially in places like Wellington and further south. Orienting our houses so they get good winter sun and making sure there is shading in summer, using good high-spec double-glazed windows that are well installed. Simple things like that don’t add much to the cost. They cut the carbon, but typically we are not doing them in a routine way.”

The authors focused on detached houses and haven’t looked at apartments yet, but they plan to. They note “some trade-offs there, in that as we start to build higher, we use material with higher embodied carbon such as concrete or steel… But getting the size down and having higher density living also provides other carbon benefits in terms of allowing people to live in proximity to jobs and transport hubs”.

Building smaller homes is a key move. Beyond that, my takeaways from the research are the importance of cutting operational emissions for all homes (partly through design, as per the quote above), and choosing low-emissions products for new builds (wood is best).

Lastly, there’s a whole bunch of research from around the world showing that it’s much more efficient to upgrade old homes than to build new ones: for example, “it would take an average of 168 years for a high-efficiency home built in Vancouver today to “earn back” its embodied emissions”. In the UK, building a cottage involves 80 tonnes of emissions but upgrading an old one involves just 8 tonnes, and “even the highest-specification newbuild could not catch up this advantage over the 100-year period”.

Auckland is growing so we will certainly need new homes, but upgrading existing homes is also very important. More on that another time!

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  1. Thanks, John. Interesting post, raising so many questions! First, (prematurely perhaps) centred on the transport side:

    Where do the transport emissions for the trips serving and visiting households sit in the Stats breakdown? A central household and a sprawl household might generate a similar number of these trips (during construction, of course, but also maintenance and social services and visits from friends, etc). But the length of these trips, and thus transport emissions, to the sprawl household could be an order of magnitude different to those for the central household.

    Presumably that gets put on the tally for the people making the trips? Is that something you could try to unpick in the second post?

    1. It’s one for the second post but will do my best. Trips during construction would be counted in the graphs above, as they’re allocated to the construction companies etc rather than the household that ends up occupying the home.

  2. “There is a close relationship between house size and carbon footprint… making houses more energy efficient… having higher density living also provides other carbon benefits in terms of allowing people to live in proximity to jobs and transport hubs”… “it’s much more efficient to upgrade old homes than to build new ones”

    I’d love to see NZ research on this. Our old houses are:

    – particularly badly built and energy inefficient
    – needing to be replaced with higher density more so than most places because our population growth is high, our housing affordability is so bad, and our transport emissions are egregious – so replacement with apartments offers the opportunity to completely change our urban form.
    – being renovated at huge cost, huge tying up of construction capacity, and huge resource use, to create very large homes – instead of being replaced with many apartments. Maintenance is one thing – hogging the land area and the construction capacity to supersize is a completely different thing.

  3. There are some real flaws in this research that made operational energy use look like it had large emissions. Firstly they assumed a very dirty grid into the future , The Mixed Renewables scenario from the 2016 MBIE Electricity demand and generation scenarios. But in that report, even their lowest carbon scenario (with emissions 11% below the “mixed renewables” modelled) involved building new fossil fuel stations.
    Secondly they sheeted back carbon emissions involved in making the generation assets to new buildings. I don’t think that is appropriate in NZs situation with our ing lived hydro assets that essentially last forever. Sure the emissions from new electricity consumption should include the carbon costs of maintaining existing assets and any assets required for additional generation, but not the historical assets. And lastly it is unclear if they assumed a similar percentage of people were using fossil gas for hot water, space heating and cooking as presently happens. All this of course will be electric. When you correct for these assumptions and assume a grid that is rapidly heading to 100% renewables and soon thereafter 100% zero emissions (when CO2 from geothermal statins is reinjected), operational EMISSIONS pale into insignificance compared to embodied carbon. Furthermore Embodied Carbon emissions are paid up front right at the tim of building, operational emissions accrue over time. To avoid dangerous tipping points we need early steep reductions in emissions: Todays emissions reductions are more valuable than tomorrows.
    So actually I think under more realistic assumptions I think embodied carbon emissions are actually more important than operational emissions and we need an immediate change from using steel and concrete to using carbon negative timber, low embodied energy earth for thermal mass and carbon negative strawbale insulation. Using these and being very careful we can in fact build a carbon negative house: i.e. one that stores more carbon than has gone into making it and that is where we need to be rapidly heading. Likewise with commercial buildings – there is no excuse for not building multistory buildings from engineered timber columns and beams, they preform better in a fire than unprotected steel does (charring on the outside of thick timber members protects the core), they are a lot lighter than concrete so bracing loads are less, we can use driven timber foundations rather than concrete ones, earth floors rather than concrete ones, timber windows and doors (perhaps with a thin aluminium skin rather than solid high embodied carbon aluminium). I’ll stop now, but bring on the carbon negative buildings!

    1. A lot to unpick here, some good points! On the first two paragraphs – I agree with a lot of this but wouldn’t call it ‘flaws’ in the research, more that in endeavouring to use an approach consistent with overseas studies and a whole-of-life methodology, they’ve made some assumptions that you can argue are less relevant for NZ.
      1) MBIE scenarios – I haven’t read them but it sounds like they could be quite conservative, so yes operational emissions could become much lower.
      2) “Secondly they sheeted back carbon emissions involved in making the generation assets to new buildings”. I don’t think they did this although I’m not 100% sure.
      3) “To avoid dangerous tipping points we need early steep reductions in emissions: Todays emissions reductions are more valuable than tomorrows”. Yes that’s a hugely important point, one I should have made in the post. The paper I discussed focused on a 2050 timeframe i.e. 30 years, to align with NZ’s stated carbon targets.
      4) “It is unclear if they assumed a similar percentage of people were using fossil gas for hot water, space heating and cooking as presently happens” – they converted the energy use from all those other energy sources into the same amount of electrical energy, and then applied the electricity emissions factors.

      1. John to answer your replies:
        1) here is a dropbox link to this 2016 document they used
        – I can only find the 2019 one online – it would be fascinating to compare the two, but that would take some time.
        2) this is from one of the authors of the study: “these emission factors do include grid losses and embodied carbon of the infrastructure (as best as possible)”
        4) thank you I didn’t manage to find this out.

    2. I don’t think those things amount to flaws in the research. This project was innovative and significant. At the moment, no building project takes any notice of its emissions either in construction or use. Note that they also use a 0% discount rate for future emissions, which is appropriate for CO2. At the moment we have new gas boilers being installed in commercial buildings and new gas central heating in houses.

      On the operational energy use, the available models at the time this research was done all pointed away from 100% renewable electricity; it’s only more recently that this idea has appeared on the table.

      Hopefully, this research project will inform future strengthening of the building code.

    3. A flaw I’d point out is “Average” New Zealand household.
      A house is very different between Northland – Auckland – Wellington-Invercargill, and city vs country, e.g.
      -Requirements for heating (and need for insulation)
      -Bracing and seismic strength
      -Distance to schools and supermarkets
      -Provision of services and PT.

      The best solution will vary, and population growth should be directed to Northland if carbon is a primary concern.

  4. I just don’t buy the argument you can upgrade old houses for 8 tonnes of carbon. If all you do is wrap the water cylinder and layout a bit of insulation in the ceiling then maybe. But most old houses need more than that. Having reroofed, repiled, reclad all four walls, had new studs put in to replace the rotten ones, replaced the old bathroom and kitchen and repainted everything we have probably used up more carbon than if we had knocked the old joint over and started again.

    1. I doubt rebuilding would use anywhere near as much carbon as starting over. However much of the original building remains is carbon not required. Parts are not required at the same time. A steel roof could last 50 years and a brick veneer much longer (I would take the inside out approach to insulating the walls). Not everything has to be modernized. Repiling is not always required, the frame doesn’t always have rot in it. New homes still have to be painted everywhere.

      1. It depends how old the building is. We took the cladding off a villa and found the studs in the kitchen had all rotted at the bottom and it hadn’t fallen down because the load was being transferred through some really well built kitchen cabinets. In our case the wall linings were fine but the cladding was rotten so we insulated the walls from the outside. But most neighbouring houses probably only have ceiling and floor insulation. My guess is the 8 tonnes of carbon in the example above doesn’t allow for insulating walls in any form. Yet that is essential for reducing operating costs and making a family warm. Also essential is a mechanical ventilation system otherwise your tenants home will be moldy. They are probably all working during the day so they cant leave windows open the way old houses were designed to be ventilated.
        Piles are only designed for 50 years. Although they last longer you will find the safety standards have changed so much that you will need new ones, especially some braced piles or anchor piles which nobody used to bother with. I am sure most rebuilds use less carbon than a new house, but 8 tonnes probably covers paint and a few rolls of ceiling insulation.

        1. Good to question these issues, but your guess is just that. I’m just finishing insulating walls for 3 bedrooms in a 50s house, so ran the numbers out of interest. I stripped off the plasterboard, reused coving, skirting.
          Scaled up to the whole house (100m2, not unusual for 50s), the CO2 for plasterboard, insulation, paint (whole room), building paper would be around 1.5t.

          Source for embodied energy data:

        2. Thank you for the link TimR, that is really useful. Sounds like you still have a carbon budget to remove some of your windows and frames and install some double glazing. Unless you need to call in the asbestos people in which case they will use the carbon budget on plastic wrap, transport and digging a deep hole to drop it all in.

  5. I don’t think studies of housing replacement vs renovation from Canada and the UK translate well to the NZ context. Their climate, legacy housing stock, new building codes, mix of building materials and construction sectors are quite different to ours.

    The cold, damp, drafty houses NZ has are mostly of timber construction. The older ones were never designed to have modern insulation or building wraps installed. Retrofitting these risks trapping moisture in and around the timber causing mold growth and rot. It is possible but has to be done properly, so not by the sort of tradespeople that gave us the leaky building disaster.

    Renovating a Grey Lynn villa up to a high standard of insulation is all very well and good but it’s not a solution that can scale up to the whole of NZ. At the moment it only makes sense in high amenity (high land value) areas where zoning/heritage restrictions prevent the construction of denser housing. If we’re looking for outcomes that minimise the carbon footprint of housing, then the first thing we should do is remove the regulations preventing denser housing development in high amenity areas, since the reduction in transport emissions would dwarf the increase in construction emissions.

  6. I don’t see this post as being relevant to reducing emissions. The problem is burning fossil fuels with a big full stop. If the grid is 100 percent renewable then that’s it no fossil fuels need to be burnt. In the future steel will be able to be manufactured using green hydrogen. Scrap steel has always being reprocessed in electric arc furnaces. Aluminium can be made with 100 percent renewable power. Cement can be manufacture using wood waste as a heat source. The Romans didn’t need coal to make glass or concrete for that matter. Dairy and meat can be processed using electricity and wood waste as heat sources. Paint and Adhesives can be made from plant materials. All this can be done, start at the source of the problem instead of trying to micro manage how the world lives all that has done is set up a toxic left right wing dynamic.

    1. We have about 7.5 years left before we use up the carbon budget that would give us a 67% chance of keeping our temperature rise to 1.5 degrees. After that everything will need to be carbon neutral in sum. If we don’t manage that, costs will rise exponentially.

      What sort of timeframe are you thinking of for these industry conversions, Royce?

      1. Well it won’t be that quick but can you change peoples behavior that quick. I would doubt it so it looks like we are screwed either way. I have being watching a few building sites of late old houses on big sections being torn down and replaced with town houses so you are getting your density even if its not in the form that you advocate. Anyway they love their concrete out here. Even old houses are getting expanded concrete parking for their cars. And all these new builds are getting LPG bottles. Asian people love gas for cooking and concrete for cars. I don’t what the council should do about it ban LPG installations organise how to cook using electricity classes for new immigrants.

    2. Fossil fuels are burnt for many reasons apart from those you listed. How do you propose to get those burning them to “start at the source”? This post is about one large and important source, housing.

      1. A house is just a collection of materials with just about all of them going back to the few commodities or precursors I have listed above. There are a few more if you would like to list them I will give you a rough guide as to how they can be produced without using fossil fuels. Your second question is more tricky I think the answer would be along these lines. Tax free manufacture of material like steel and cement but this could include products such as raw logs or pre cursor chemicals used in the manufacture of synthetics or things like melamine, formica, adhesives and paints. Companies would have to partition themselves with the tax free renewable precursor/commodity manufacturing part of the business having separate accounting to the rest of the business. So we could end up with giant plants in the desert hooked up to a solar farm producing raw steel. Obviously Tiwai would qualify but Glenbrook wouldn’t. A lot of these commodities have a world price which you can read in the news paper so it would be pretty hard to game it. So now its just a matter of getting worldwide buy in from govts to forgo the tax. So if you use renewables then no tax if you use fossil fuels then you are taxed.

  7. In NZ, smaller homes just mean more expensive homes per sqm. We currently have the madness of a new build 60sqm house being priced at $600K in a development at West Hills. I think there has to be a bit more to it than just ‘smaller homes = better’.

    1. Yes agree- here in Te Atatu Peninsula we are having 2 bedroom townhouses/apartments being priced at 800k!. Also lots of the planned apartments are being advertised as for the rental market at $750 pw – clearly aiming for investors not home owners.

  8. Actually I am glad to see that there is a focus on using what you have better. It would be good to shift the assumption a home should last 90 years. In the UK if you lived in anything less than 90 years old it was modern. I like new developments though very few are good for kids, even in Hobsonville you have to cross the road to get to the green space. There are some exceptions of course in Freeman’s Bay. So, until space is carved out in the unitary plan for family suitable housing then I can see why people may cling to their villas. They can be densified. Hoist them up on stilts and you create a flat below. Convert the attic and more people can move in. What they have too are gardens, and character. If you paint them, ventilate them, put in curtains, insulate under and over, put in DVS and a heatpump they are cosy enough in winter and cool without needing aircon in summer. They are made of wood which means they can keep being reinvented and most are over 90 years and much loved. As I say, not against new housing developments but would be against the rip up the old just for the sake of it when we do need a mix of options. (plus would hate families to feel they had to go to the edge of the city to get somewhere that suited their needs and then drove everywhere).

  9. Whatever solutions you come up with.

    You need to consider that 80% of the houses we will have in 2050 when we are supposed to be “all gases carbon neutral”, are already built/in existence today.

    So either you need to plan for a major tear down and rebuild project to slash those operational energy use of all the houses we have now and in 2050, or you need a lot of work on solutions that are cost effective as retrofits to existing housing stock.
    Or you will never build your way to energy efficient houses in any timeframe that matters for humanity.

    For the 20% of new houses we are going to be building in the next 30 years, is to stop building these as energy dungers from day 1 – it is possible to have a large house that is energy efficient. But its not easy within the current systems we have here. Europeans have been doing it for a very long time. We don’t seem to see their experience has any relevance here.

    For instance, Why do we not mandate thermally broken aluminium joinery for all new builds, instead of leaving it to the market as we do. Which because these are about 5% more expensive to build than the existing designs, never get a look in when the competition for that money is a flasher kitchen.

    A double glazed non thermally broken window [which is pretty much what is used everywhere these days in NZ] is actually about the same thermal efficiency as an old single glazed wooden framed window (with proper seals around the window openings).

    The reason the new double glazed windows efficiency is that poor is that the aluminium frame leaks the energy like a sieve – Aluminium is a good heat transfer mechanism after all.

    BRANZ did a comparison a few years ago now of return on investment ($ cost versus energy savings) on retrofit double glazing and in almost every area of NZ it never pays for itself. Agree, some specific use cases do make it worthwhile (like just doing a south facing side of a house in Southland). But if you included the lifetime energy costs of the retrofit, it may be even less worthwhile overall on a lifetime emissions basis, even in such cases.

    Reducing house sizes is an easy suggestion to make, but it currently won’t fly with many as “too impractical” for their life styles.

    And is treated just like telling folks to stop buying and driving SUVs and double cab utes.

    When pushed everyone thinks these are good ideas, but also that someone else should make these changes, rather than them personally.

    So how do you even get progress on reducing emissions in any meaningful timescale in this area?

    Truth is, the problems often lie within the whole building system not just the inefficient houses that get built by the system, almost as a by product.

    Houses are supposed to last a long time. Decisions made or not made today, will have an impact still 50+ years from now.

    Its not an easy one to change direction on – even within 30 years.

    1. I agree. The same goes for wall insulation. People don’t know they need it so they don’t value it when purchasing a house. The Government could announce a rule that all houses must have thermally broken window frames and insulated walls by 1 April 2040. Then as people redecorate each room they could rip off the gib and insulate and do the windows as a marginal cost. A firm date would mean people would check out a house to see what has been done and what hasn’t and place a value on work completed.

      1. Miffy, it isn’t just a case of ripping off plasterboard and putting batts in. A lot of older homes (especially the 1940-1960 era state houses) are watherboard clad with no moisture barrier. You can’t put batts in the wall without installing a moisture barrier such as building paper and BRANZ have not developed an approved work method to retrofit building paper from the inside. To insulate walls you effectively have to reclad the house. Weatherboards are so brittle that they cannot be removed and reinstalled and a lot of those houses are clad in asbestos boards.

        I am firmly of the belief that we should just be demolishing most of this older housing stock, but the planning rules need to be liberalised enough that the carbon cost to build new homes is outweighed by the lower transport carbon of dense urban living and the building code needs to be tightened to gain the advantages of better build quality.

        1. I’ve pulled the weatherboards off two sides of a 1930s cottage and resused them with very little breakage.

    2. I think from memory the thermal resistance of even the best windows, thermally broken, triple glazed, argon filled, with low E glass, was still only about R1.7, so even high performance window still aren’t flash.
      A lot of houses are built by developers as spec homes, so someone else is going to bear the cost of heating them. They aren’t going to dip into their pockets for more than the minimum for stuff that will be buried in the walls and under the floor, so things get built to the minimum. Upping the minimum standard becomes the only way to improve building performance though that is a bit of a blunt instrument. There have been attempts to improve the visibility of these buried factors. There are thresholds where costs escalate significantly, like for a 90mm thick exterior wall I think maximum insulation value is about R2.2. Most insulation the actual insulator is air with the glass wool or polyester just there to shut down convection currents and immobilize the air, so the thickness of the insulation determines the R value. I bought some R6.0, it had a loft of 260mm I believe. Going above R2.2 would require thicker walls, adding significantly to costs.
      Some passive solar principles would cost very little to implement in new buildings (not all locations have the aspect to allow it). No thought at all is generally paid to such things. I know some people who bought a house (in winter). It had big wrap around windows so a lot of glazing facing East and West. They had a lot of unwanted solar gain in summer and the place was uncomfortably hot half the year. They didn’t own it long.

      1. And thicker walls are pretty useless if the timber studs provide a heat pathway. If I was building from scratch I would provide thicker walls, but I’d use two lines of studs, staggered.

        On the windows, our retrofitted aluminium double glazing has been very impressive – for both reducing heat loss and condensation. Where the aluminium joinery wasn’t of good quality and we replaced it with new double glazing – but wooden (with the intention of doing this to to the other ones in 20 years or so) – I haven’t been so impressed. We introduced draughts – apparently I should’ve done more homework on that.

        One thing I notice few people get right is screened airflow for summer time heat. We do need to maximise the solar gain when the sun is relatively high, on all those grey, chilly days in spring and autumn (and even summer). Not just when the sun is low in winter. Our climate isn’t so clear cut as the passive heating designs assume.

        Rather than cutting out the possible solar gain, planning for air flow on the hottest days with insect screens throughout the house has worked well for us.

        1. From what I can find the R value of softwood timber is slightly under half that of fiberglass batts. About R0.9 for a 90mm wall. That isn’t so great. Timber probably makes up about 10% of the area.

          We went for thermally broken aluminum double glazing. It made the biggest difference. When I bought the place it didn’t have any insulation anywhere and an open fireplace. When I would light up the fire in winter it would heat up the air in front of it and then suck it out of the room and send it up the chimney. This would draw in cold air from all the leaks everywhere. Now with double glazing and insulation everywhere the house is much easier to heat. I removed the windows from the East and West of the living space and we have a bit of North facing glass. The soffits completely shade the North glass mid Summer. The house started with a fairly nice solar aspect. It works well on those cold clear winter days after sun rise. What I don’t have is thermal mass. Even with double glazing we still get a bit of condensation on the glass in the sleeping spaces when it gets really cold out. Some sort of forced ventilation might be next on the list.

        2. Have you considered using a water for thermal mass? (I’ve seen people use a bank of barrels next to a sunny window to good effect.) Water is roughly twice as good as concrete.

          Timber is a well known path for heat loss. I’ve seen ceilings where the insulation above is only between the joists, and the heat pathway through the joists means the ceiling underneath them is cold, and goes mouldy in a grid pattern. This was resolved by putting in a second layer of insulation over the first.

        3. Heidi a better and more cost effective approach is to have one line of studs with no nogs on the outside, Ply sheathing on the outside of that doing the bracing loads and instead of nogs (dwangs) between the studs you have battens on the inside where all the services run. Then the only thermal bridge from framing is where the lining battens and studs cross. So you have one layer of insulation – a roll between the studs running vertically and an second roll running horizontally inside them running horizontally between the lining battens. And the pipes and wires then don’t interfere with the main insulation runs, between the studs, just the supplementary insulation inside that. And as for stud thicknesses – we pretty much have to go for 140mm now for wind loadings in most places so you end up with 190mm of insulation around your walls. More than this is getting silly in NZ unless you are at altitude in the North island or in the Southern half of the South Island or at altitude. – the reason for not insulating more than this is that heat losses through windows will predominate, so total heat loss in the house will be little different with 200 or 300mm wall insulation if the walls have windows and doors in them.
          Regarding solar gain – its better to have variable screening perhaps with vegetation to cope with the solar skew (the hottest part of summer is well after the summer solstice when the sun is highest in the sky). You have to be careful with vegetation on the north though as most deciduous plants have 20% shading from branches – primo is kiwifruit or grape vines cut right back in winter but giving you shade in late summer with their big leaves when North overhangs aren’t giving you so much shade – How come we are talking about this in a transport blog??

        4. Only 2 times better? I think the specific heat of liquid water is about 4.18 kJ/(kg.K) and one I found for concrete has it at 0.65 kJ/(kg.K). That would make it about 6.5 times better than concrete by mass. Concrete has maybe 2 to 2.5 times the density of water, so water would still be about 3 times better by volume. The best thing about water is its liquid so convection currents can move heat though out the mass. This would give it a high thermal flux unlike concrete.

          Say a 3m wall lined with 150mm pipes, 2.5m tall, would give 20 pipes containing about 40kg of water each for a total of 800kg. A temperature range of 6 degrees (18-24 degrees C) would give 20mJ of storage. J=w.s so that would be about 5.5kWh I think, so still quite small. I don’t think that would be near enough even for daily fluctuation smoothing mid winter. Using 200mm pipes would up that about 50%.

        5. Timber takes up way more of a wall area than it should. Including the completely pointless nogs (horizontal elements)

          Windows are a wound in the thermal envelope. The current standard R value of 0.27 is an overestimate based on simplified modelling. It is actually much worse than that. As you would expect when using the 7th best conductor of heat known to science. These windows are where the majority of heat is escaping in a modern house. If you used a half decent windows, detailed properly you’re well on the well to having a decent thermal envelope

  10. The fact that the vast majority of NZ’s housing stock is utterly deficient in insulation, due to following a design pattern for places with much warmer climates in Australia and Southern Africa, no doubt contributes to that “operational energy use”.

    Housing in much of NZ should be designed around central heating, not swimming pools.

    1. Daniel this same study found that heating energy was insignificant for these new reference houses. It was on a par with the energy going into lighting. Here is a quote from the studies authors in their presentation to the Eco Designer conference in Auckland earlier this year: “…in the case of the NOW home and other BRANZ residential reference buildings, energy use is dominated by plug loads (that is things that aren’t permanently wired) and hot water. This suggests that our current focus on heating energy, especially in Auckland will not lead to a low carbon home”

    2. Insulation is definitely needed, but if you dont provide any heat, its all for naught. You can have the most insulated box in the world, but that wont make it warmer inside the box.

      1. Jack you can make a house have such low heat losses that the heat from cooking, refrigerators, lighting, electronics, body heat etc combined with some solar energy are enough to provide all the heat required. This is what the Passiv Haus people do – not just with substantially better insulation, but obsessive attention to eliminating thermal bridging and air leakage so their air to air heat exchangers work properly to provide fresh warm air that is heated by the outgoing stale warm air. And there is the other other way of doing it with a Passive Solar house – that is thoroughly designed for the sun, has enough thermal mass and a well enough insulated external envelope that there is enough heat from the low winter sun on sunny days to carry you through days of cloudy weather. No other heating or absolutely minimal required. At base both these systems rely on heat gains from inside or the sun being greater than heat losses through the Buildng envelope. So the issue actually is not being able to heat buildings, its about making them carbon negative through the stored sequestered carbon in the building fabric, that at the same time makes them self heating.

  11. There’s a lot of work internationally that has been done on upfront versus operational emissions in buildings.

    Chris Magwood is particularly good on how we can construct carbon positive buildings (i.e. buildings which remove carbon from the environment – carbon sinks) in the future.

    However the problem with using international studies for precedents is the way we build in New Zealand. The way we build in New Zealand is and has been appallingly bad in the past.

    The focus is to construct the cheapest buildings it is legal to build. Which is made worse by having some truly awful building standards. It would not be legal to build this way in any internationally comparable country and it was worse than this in the past. For example, There is still no requirement in the building code to provide heating.

    This results in some very poor energy efficiency for new and old buildings. So much so that it is not affordable to keep the internal conditions in our buildings at healthy levels.

    The research referenced here assumed that very energy efficient buildings were constructed to get to the ‘5 times too much carbon”. If the actual energy demand to live in a healthy and comfortable environment (you know like in other countries) this figure would be way worse.

    All this being said I don’t see lifecycle emissions coming down that much if we build better. We don’t typically use that much energy in our homes because its unaffordable. That means we live in unhealthy conditions. The energy efficiency measures are required to stop us getting sick (and in some cases dying) from the homes we live in. The housing-related health statistics are eye wateringly bad in New Zealand. I wont repeat them here as there’s an election on they seem to be repeated on a daily basis. What’s missing is evidence-based policy to combat it.

    Despite its best intentions, there is no evidence to support the Healthy Housing measures. Putting ceiling and floor insulation does not adequately improve energy efficiency. You can’t dam part of a river – you have to have a comprehensive solution. We already know the internal conditions that result from such an approach and the health impacts (none)

    The issue is not technical it is funding. This funding issue is one that has already been solved overseas. Perhaps it is time we stop burying our heads in the sand and roll out similar programs here. Rather than rolling out half-arsed measures with no evidence to support them.

    The other point to raise is where we build if we spread out further and further this impacts on our transport emissions.

    1. I worry that mandated heating requirements would also be arbitrarily applied and so require passive solar dwellings to be fitted with completely redundant heating systems. Maintaining comfortable internal temperature could be seen as a load leveling problem with both a daily and yearly cycle. The yearly cycle has the added complication of the seasonal lag (about 6 weeks). Smoothing out an oscillating system is done with capacitance and resistance, in this case capacitance is making the internal space thermally massive and resistance is by the insulation. The yearly oscillation is minimized by controlling solar gain via overhangs over North windows, exploiting the solar elevation change summer to winter to shade the windows in summer and expose them in winter. Making a house thermally massive and doing it cheaply and simply would be the trick. For it to work it would also require a high thermal flux between the thermal mass and the air inside the house. The other (often neglected) thing required for a healthy and comfortable internal environment is reduced humidity. This is not a load leveling problem. Virtually all human activity in a house adds moisture. Cooking, bathing, breathing etc.. Controlled ventilation via an efficient heat recovery system is probably the most efficient way to remove moisture (not those systems that just pump in cold air from the ceiling space). Timing most ventilation for when total moisture of air is at its lowest outside the house. Doing these things effectively would decouple the size of the house from the operational energy use. Thermally massive doesn’t necessarily mean physically massive. There are phase change materials and thermal batteries besides physical mass, though the simplest is physical mass. Phase change could be used to make the desired temperature sticky. Finding a way to exploit the thermal mass under a house is an interesting problem. Heat pipes can have a very large thermal flux but are not very good at pushing heat down any distance. Might still work for a split level dwelling. Another thermal superconductor is graphene. Bidirectional graphene rods might as well be unobtanium at the moment. Things like passive solar and solar water heaters are difficult to justify on economics alone.

      1. Passive Solar is design philosophy thoroughly debunked and overtaken by other more provable design philosophies such as Passive House.

        Either way, if you’re going to design something lets base it on evidence and verify it in use. Something that Passive Solar fails on. It should work given the right conditions but the trouble is the weather fails to play ball so you’re left with too cold or too hot but never just right.

        Also lots of glazing and concrete doesn’t strike me as a particularly sustainable way of building

        1. You say passive solar has been thoroughly debunked and then in the same sentence mention passive house which has many principles in common and even derives its name from it. It merely removes the solar aspect and substitutes “active” heating and cooling in its place all be it small in size. You should also know that properly designed passive solar should never be too hot at least not in temperate zones. Right sizing of glazing is part of it. I’m aware of NZ’s big overcast that negates solar anything for about 3 months a year. This does not exactly correspond to NZ’s coldest period. I also know that the thermal mass is the achilles heel of the idea and how concrete is responsible for so much CO2. You will notice that I am musing about novel approaches to thermal mass that wouldn’t require concrete beyond what would normally be used in an ordinary house. Passive solar principles also eliminate East and West glazing and minimize glazing to the South, while right sizing glazing to the North, and so doesn’t necessarily result in any more glazing overall than normal.

        2. James you can get lots of thermal mass for very low embodied energy using earth. In the very back of the recently releases Earth Building Standards (NZS4299) are details for cement free driven timber pile foundation for under Strawbale and light earth walls along with earth floors on a deep layer of mussel shell insulation. This is a good start to a carbon negative building which is where we need to be headed. Oh and the wall insulation values are 3 times current code minimum with the SB walls. The earth is hygroscopic so smoothes out humidity fluctuations – you just don’t get condensation in earth plasters and earth houses.
          And as for Passive Solar being thoroughly debunked what tosh. The whole Passiv Haus thing although teaching us really good things about the importance of avoiding thermal bridging and the usefulness of heat exchanger ventilation in winter has significant flaws in being unable to open windows and doors and reliant on there not being a power cut to stop you suffocating. And in overheating in summer risks and in all that stuff that goes into building them that tends to veer away from being carbon negative which is where we actually need to be heading.

        3. Wherever did you get this from?

          ‘usefulness of heat exchanger ventilation in winter has significant flaws in being unable to open windows and doors and reliant on there not being a power cut to stop you suffocating. And in overheating in summer risks and in all that stuff that goes into building them that tends to veer away from being carbon negative which is where we actually need to be heading”

          PH is designed not to overheat (unlike Passive Solar)
          You can open the windows in a passive house
          There is nothing stopping a Passive House being carbon neutral or carbon positive in construction.

          We have to move to an evidenced-based design approach, based on what works well overseas.

        4. James what is more important than chasing the rabbit down the rabbit hole of reducing heating demands is ensuring you are doing that in a carbon negative way. If you look at your carbon emissions savings over the buildings lifetime of a code minimum +1/2 as much again insulation and a Passiv Haus building when the heating they will be using is either completely carbon neutral wood heating (like 50% of NZ houses) or from the grid that is already 84% renewable and heading towards 100% very soon (I know that isn’t the same as 100% zero emissions but CO2 from geothermal stations will I’m sure be reinjected very soon) then the differences are negligible. But with embodied carbon emissions – that all happens up front. So THE most important thing is to build embodied carbon negative houses, these emissions are paid up front right at the time of building rather than operational emissions that accrue over time. We need to stop kidding ourselves that heating energy reductions in NZs conditions with a very green grid and access to Ultra low emission woodburners and lots of wood rotting around skid sites in forests do anything for climate change compared to building carbon negative houses (Look in the back of the Earthbuilding Standards NZS4299 to see how do do that with Strawbale walls on driven timber piles and earth floors on mussel shell insulation – a Passive solar carbon negative house is a snip)

        5. I don’t think James is talking about reducing heating energy. It would be good to use it more efficiently, although as you say, with a greening grid the heating energy isn’t a big factor anyway.

          But the NZ-specific research suggests that NZers underheat our homes, and from a health perspective we should be using more heating. Two separate challenges:

          For existing homes – the vast majority of future homes already exist, of course – the challenge is to upgrade their insulation and/ or thermal mass and keep them warmer. This is for better health outcomes, it might have minor negative climate change outcomes but we can mitigate that with progress on the grid.

          For new homes, reduce embodied emissions, along with better design to avoid the problems of the existing homes. And, critically, build them in the right places. Homes of straw and earth are fine but they’d better be in Kingsland not Kaukapakapa.

  12. Home size is determined by the people building them. If you want a small house, you build a small house. If you want a big house, you build a big house.

    So what exactly do you mean by “we need to build smaller homes”? If you need six bedrooms, then that’s what you build.

    I also question the figures, as it isn’t explained how they’re arrived at. A house on a section with food production has a lower carbon footprint than an apartment where all the occupants needs are externalised.

    But most importantly, the figures don’t discriminate between lifestyles. You could have two IDENTICAL homes but have one with twice the carbon footprint of the other because of how its occupants use it. One household may travel a lot more and live a high consumer lifestyle, whilst the others may have occupants who stay home a lot and/or don’t feel the need to buy things all the time.

    1. By “we need to build smaller homes”, I mean the average size of new homes built in NZ needs to drop. Pretty self-evident isn’t it? It’s not like I’m the only person saying it.

      Very few households need six bedrooms, and the long-term global trend (and in NZ until the last 8 years or so in which the housing shortage got much worse) has been for the number of people per household to decline. Not that that’s a good thing – household ‘economies of scale’ mean less energy use per person in larger households – but it’s the consequence of people living longer and having fewer kids.

      “A house on a section with food production has a lower carbon footprint than an apartment where all the occupants needs are externalised” – you might be confusing the two different data sources for this post. The first source is Stats NZ and the data is an average for all NZ households, not taking into account where or how they live or how many people in the household. Those are key factors of course. The second source is some research that looked at detached houses only. The issue of houses vs apartments is one I’ll hopefully get to sometime, but not in the current three-part series.

      Your assertion is almost certainly incorrect though. Most of the food carbon footprint is from meat and dairy, it’s hardly affected by whether you grow some vegetables (although of course it’s great if you do). Transport is highly affected by location as I’ll discuss in the next post.

    2. About 1% of homes are lived in by the people who built them.

      We need to change planning laws to make smaller homes more economical. If I have to buy 400m2 of land, I’m not gonna build a small home, even though the prices suggest that people really want them.

    3. Geoff we have smaller household sizes now, but much bigger houses – its part of the obesity epidemic. The average house size used to be 100m2 with an average of 3 people in it, now its more like 200m2 with an average of 1.8 or something. We used to have a girls bedroom and a boys bedroom and an adults bedroom, one bathroom perhaps a separate toilet, regardless of the number of children you had. And in the end what matters most to the climate, with a grid rapidly becoming close to 100% renewable (and almost 100% zero carbon) is not electrical energy use. Its embodied carbon. These emissions are paid up front and todays emissions reductions are more important than tomorrows to avoid dangerous tipping points. So while designing and modifying buildings to use little energy for heating and none for following is important, what is more important is just how we do this. Basically we have to use cellulose everywhere we can (even a highly processed wood product like plywood is nett negative in embodied CO2) and high embodied carbon materials like concrete and steel almost never. NZ already does quite well with our timber framed buildings, but these need to be on driven timber piles rather tan concrete strip footings or even concreted in timber piles. We need to move to timber or earth floors, timber rather than aluminium windows and doors, timber rain screen claddings ideally left to weather so now high carbon paint finishes, timber roof framing of course but also possibly timber shingles. And insulate with wool rather than fibreglass or polystyrene insulation – or better still Strawbale insulation. All to approach buildings that are nett negative embodied carbon.

  13. Thanks John for the interesting article.

    As you indicated, it is critical for us to focus on the pre-existing buildings. In another study, we estimated that the pre-existing houses would contribute up to 67% of total GHG emissions of the residential buildings in 2018-2050. These include detached houses, medium density houses and apartments. It is also equally important to focus on the new builds, particularly the size, construction materials, orientation, and energy efficiency and harvesting.

    And more importantly, further research is required to investigate how to influence households to choose smaller but sustainable and healthier homes, while ensuring building standards and builders will deliver such buildings in a timely manner.

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