Which insulation should I use? Introduction

People often wonder what kind of insulation to use. This is a great question, which we will come to later. Two questions are more important: Should I use insulation? and Where should I put it?

Yes!

Whatever insulation you are using is almost certainly better than not using insulation. Any insulation will reduce your heating bills and cooling bills and make the building more comfortable. If you're comparing the environmental impact of different kinds of insulation, then you first need to compare that one-off impact with the on-going impact of your heating or cooling. 

Where?

Putting insulation in the right place is important, and this means insulating all around the building. Putting on an extra scarf in the winter will keep you warm, but it will only be really effective if you're wearing a warm coat and good shoes. And if you remembered to put on your trousers. In the same way, sticking some more insulation into a wall cavity will make a bigger difference if you're also insulating the rest of the walls, the roof and the floor, and making sure that your windows are insulating properly. More insulation is usually better, but going from zero to 10cm will have a much bigger effect than going from 10cm to 20cm. If there is an uninsulated part of your building, those extra 10cm would be much more effective there.

How does insulation work? 

Insulators slow down heat. Some materials, like metals, are good conductors and will quickly move heat. You can tell a good conductor because it feels cold when you touch it. Unless it has just been on the cooker, in which case it may feel very hot. Good conductors are bad insulators. 

There are many insulators around you. Wood and paper are insulators, the wool in your sweater is a good insulator and the polystyrene trays from the supermarket are very good insulators. The best insulator around you is probably air. And most insulation for building works by tapping air.

Foam of Fibre? 

Insulation can be broadly divided into two groups: foams and fibres. 

Fibres

Examples of fibres are glass wool, rock wool and cellulose fibre. Fibre insulation works by trapping air among the fibres. This is exactly the same as your woollen sweater or down jacket, and insulation made from textiles is also available for buildings, including recycled materials or new wool. Fibre insulation does not usually have any compressive strength, so while it is good to add to walls and ceilings, it is not a good idea to put under a wall or foundation. Also, while the insulation works by fibres trapping air, it will stop working if air is getting through the insulation, and bad things can happen if water gets in. Therefore, it is very important to add weather protection on the outside and an airtight barrier on the inside of fibre insulation. 

Foams

Examples of foam insulation are polystyrene, polyurethane, polyisocyanurate and  phenolic foam. Polystyrene is available both expanded, known as EPS and styrofoam, or extruded, which is known as XPS, E is for expanded, X is for extruded and C is for confused!! The foam may be made of bubbles of air, or another gas that could be a better insulator, so foam insulators can have better performance than fibre insulators. This means generally that a thinner layer of foam will keep the house as warm as a thicker layer of fibre insulation. Compared with fibre insulation, especially cellulose fibre, the manufacture of foam insulators can use a lot of energy and fossil fuels, and can release some toxic chemicals. However, a thinner layer of insulation may mean thinner walls or roof and less need for other building products, so calculating their impact may not be simple. Or given the same wall thickness the higher performance will mean less heating over the lifetime of the building, which will usually save much more energy than the manufacturing of the insulation. 

Foam insulation can be strong, since the foam structure is rigid, so it can be used under floors, under foundations, or anywhere else where there is a load. 

While foam insulation does not usually let any air or moisture through, there can be gaps between the foam and the structure, for example where expanded polystyrene has been put in the space between pillars and beams of a wooden frame. If there is an earthquake and the building moves, this can leave a permanent gap. There may also be gaps between panels from the beginning if they are not installed carefully.

Depending on air flow, a gap of one millimetre in insulation can lead to a drop of performance by 50%, as well as increasing risk of condensation.

Form

Insulation may be available in four different forms: flexible blankets, rigid panels (batts), loose fill or sprayed foam. The construction technique will usually dictate what form the insulation must be in. Most insulation materials are available in different forms. For example cellulose fibre is available as flexible blankets, rigid panels or loose particles that can be blown into a cavity.

Shape and Size

Blankets and batts often need to fit spaces and they are available in standard widths. Insulation can be cut on site but this takes time, may increase gaps and may lead to more waste. 

Safety

Most insulation is harmless. Commercially available insulation materials have been tested for toxicity and will be fireproof, as long as the manufacturers have not lied in their testing. Glass wool is not nice to install, and may be unpleasant when a building is demolished or renovated but once within a wall structure it should not harm inhabitants. 

Strength

If you need insulation under a building then it needs to be structurally strong. This usually limits your choice to foams such as XPS (Extruded polystyrene). Some cellulose-based structural insulation is available. 

Open or Closed?

Insulation usually works by trapping air. Wool-based insulation traps air between the fibres, which are open and will usually allow some air to pass through the insulation. Foam insulation will usually stop air from getting through. Cellulose insulation is not as open as wool-based insulation, but not as airtight as foam. Since insulation is only effective and safe from condensation when it is airtight, open insulation requires an airtight barrier on one or both sides. Attention will be needed for joints and boundaries of insulation that is more airtight. Closed insulation will not let air through, but careful installation is needed to stop an gaps that air may get through.

Moisture Content

Different materials hold different amounts of moisture. Insulation with a capacity to hold moisture may be helpful in stabilising humidity levels in the situation where the absolute or relative humidity outside is not comfortable inside. Alternatively, there may be a risk where humidity builds up levels of moisture within the structure that can cause building damage or health risks.

Moisture Permeability

As well as the amount of water a material can hold, it may be better or worse at letting moisture through. 

Temperature Range

With some insulators, performance changes with temperature, so they may be good inside your walls, or above a foundation slab, but not so good on the outside where it gets colder. 

Heat Capacity

Different insulation materials also hold different amounts of heat. Increasing the thermal mass of the building will make more stable temperatures. In most cases, the insulation performance, in other words the thermal conductivity, is much more important than the heat capacity. 

Thermal Conductivity or U value

Last, but very much not least important! Thermal conductivity,  gives a value of the material. U value is for a particular thickness. For both, lower values are better insulators. If the insulation is twice the thickness, the U value will halve. U value is measured in W/m2K and thermal conductivity is in W/mK.

Ecological Decisions

There are many different insulation materials available. They come in different forms and give different performance in terms of heat, airtightness, moisture and sound, and they have different price tags. There is no single "best insulation material". Architects and builders may have favourite materials, and manufactures usually promote their own materials and point out shortcomings in competing materials (for example this online article by the founder and managing partner of Havelock Wool).

There are also different impacts on environment during manufacture and disposal, but to quote Schmidt et al. (2003):

"Many people believe that the emerging insulation products based on biological resources (cellulose), such as flax and paper wool, are much more environmentally friendly than a product based on natural mineral resources such as stone wool. This belief may, however, be unfounded."

If you are worried about fossil-fuel based insulation materials, you need to first consider how much fossil-fuel energy the insulation will save. Sure, you may not be planning on burning gas or oil, but if you're heating with electricity, that electricity has been made with fossil fuels. It may be "green" energy, but the solar panels and wind farms have been made with fossil fuels, and the hydroelectric dams poured with concrete, so you're still not at zero carbon. And even if you did find a way of producing energy without any carbon input, you'd need to calculate whether it's better to use it for your house, or supply that energy somewhere else to offset other people's carbon use.

Schmidt et al. conclude: "The energy and environmental impacts saved during the use phase [of insulation] are more than 100 times larger than the impacts in the rest of the lifecycle".
This sentiment is repeated by the US National Park service for the Pacific Northwest:

"Do not substitute a "green" insulation material for a non-green material if doing so will result in lower overall energy performance. Even though the environmental impacts of the insulation material might be lower for the green product, the overall environmental impact of the building would likely be greater by lower insulating values."

So while important, before you worry about what happened during the manufacture of the insulation, and what will happen if someone burns the insulation at the end of its life, the first thing to worry about is burning less to heat the house while the insulation is doing its job. Building constraints may limit the thickness of insulation, in which case some insulators may not have sufficient performance. Even if thickness is not limited, the extra thickness required for lower performance insulators may require extra materials to keep it in place and more external wall finish to cover it.

It may also be that natural materials attract "natural" pests, molds and fungi. You may want a material that will decompose naturally after its lifetime, but you definitely do not want the material to decompose while it is part of your building. Until the 19th century, the only insulation materials were organic, and the levels of insulation ranged from poor to non-existent. With the new scientific understanding and product availability of the industrial revolution, man-made materials became available, and these were used because they were cheaper, performed better, and would last longer than natural materials. The higher energy costs in the long depression of 1873-1896 boosted use of man-made insulation materials in industrial sites, and a hundred years later the oil shock gave another incentive to insulate homes (see Bozsaky, 2010 for more detailed history). Many "natural" insulators are recent developments that package natural materials in familiar forms of man-made insulation products. They do not necessarily have longer and more reliably determined lifetimes, or lower toxicity than man-made materials, and they may depend on chemical treatment to make them resistant against fire and pests.

In terms of carbon emissions, wood-based products are sometimes considered carbon-negative, since carbon captured by wood is being stored in the building. This may be true, but if the wood were not used in the building would it still be a living tree? Read more about that in a previous post.

References

Bozsaky, David (2010). The historical development of thermal insulation materials. Periodica Polytechnica Architecture, 41. 49-56. doi:10.3311/pp.ar.2010-2.02.

https://www.researchgate.net/publication/274110149_The_historical_development_of_thermal_insulation_materials

Danielle Densley Tingley, Abigail Hathway, Buick Davison, & Dan Allwood (2017). The environmental impact of phenolic foam insulation boards. Proceedings of the Institution of Civil Engineers - Construction Materials, 170(2). https://doi.org/10.1680/coma.14.00022

https://www.icevirtuallibrary.com/doi/pdf/10.1680/coma.14.00022

Danielle Densley Tingley, Abigail Hathway, Buick Davison (2013) BIG Energy Upgrade: Environmental burden of insulation materials for whole building performance evaluation. University of Sheffield.

https://www.sheffield.ac.uk/polopoly_fs/1.363473!/file/beu_wp1_civil_final_report.pdf

Department of Interior. (nd) Environmental Considerations of Building Insulation

National Park Service – Pacific West Region 

https://www.doi.gov/sites/doi.gov/files/migrated/greening/buildings/upload/iEnvironmental-Considerations-of-Building-Insulation-National-Park-Service-insulation.pdf

Passivhaus Plus (2016). Cellulose insulation improves airtightness by 30% — PYC Systems

https://passivehouseplus.ie/news/product-news/cellulose-insulation-improves-airtightness-by-30-pyc-systems

Seyedeh Shiva Saadatian (2014). Integrated life-cycle analysis of six insulation materials applied to a reference building in Portugal.

https://estudogeral.sib.uc.pt/bitstream/10316/39028/1/Integrated%20life%20cycle%20analysis%20of%20six%20insulation%20materials%20applied%20to%20a%20reference%20building%20in%20Portugal.pdf

Schmidt, A., Clausen, A. U., Kamstrup, O., & Jensen, A. A. (2003). Comparative Life Cycle

Assessment of three insulation materials—stone wool, flax and paper wool. 

https://www.researchgate.net/profile/Allan_Jensen6/publication/247152335_Comparative_life_cycle_assessment_of_three_insulation_materials_stone_wool_flax_and_paper_wool/links/56efcece08aed6b28a9e41ff/Comparative-life-cycle-assessment-of-three-insulation-materials-stone-wool-flax-and-paper-wool.pdf

Anders Schmidt, Allan Astrup Jensen, Anders U. Clausen & Ole Kamstrup (2004). A Comparative Life Cycle Assessment of Building Insulation Products made of Stone Wool, Paper Wool and Flax: Part 1: Background, Goal and Scope, Life Cycle Inventory, Impact Assessment and Interpretation. The International Journal of Life Cycle Assessment 9(1): 53-66 https://www.researchgate.net/publication/282754710_A_Comparative_Life_Cycle_Assessment_of_Building_Insulation_Products_made_of_Stone_Wool_Paper_Wool_and_Flax_Part_1_Background_Goal_and_Scope_Life_Cycle_Inventory_Impact_Assessment_and_Interpretation

Choosing Best Airtight Options in Japan

What kind of materials are available in Japan, where are they found, are they safe, how are they installed….?

 

If you are looking to design, build or own a comfortable healthy house that consumes minimal amounts of energy then you may have searched and come across the following basic formula (no rocket science involved):

1. Airtight
2. Super insulated
3. Thermal bridge free (minimal moisture risk and heat or cooling energy loss at vulnerable spots in the assembly)
4. Optimal solar orientation (sun in winter and shade in summer)
5. Air ventilated (i.e., mechanically controlled fresh air!)

1    Passivhaus Consultants can help with this but of course, correct and healthy doses of the above cannot be achieved without the expertise of engineers, architects and builders or without the proper materials. 

Onto the topic of choosing the best airtight products (1 above) in Japan. First, let me start by showing an image of the effect on moisture infiltration of even a small (25mm or 1") hole in the airtight layer:

Thirty litres a year is a lot of moisture from one little hole, for example untaped seams or punctures from staples not covered up! It doesn't take much to imagine how this adds up and what the average home lets in these days, despite being more airtight than before. What does this cause? Mold, structural deterioration, and drafts which are not comfortable, conducive to build longevity, healthy, or energy efficient. Adequate and proper installation is paramount.

Next let's outline how these products should look in relation to a global society conscious of energy use and carbon footprint along with changing building codes around the world, such as the BC Step Code Canada.

 

Products should be VOC free, have a low carbon footprint, superior sticking properties where applicable in weather extremes, be robust during rigors of construction, smarter with regards to permeability in different directions, and have reputable certification that shows they meet the above conditions. Simply put, ones that are healthy and do a great job at keeping the energy and moisture where you want them. 

 

In my experience these sorts of products are difficult to find in Japan. For example, I recently did a search in Japan for foundation sealing tapes.

 

The first step was checking Japanese distributor sites based on known products readily available in Canadian, US, UK, and European markets—where Passivhaus is well established. What I found was 3M 8067 which hits a couple of the targets but not all. Beyond that not much else besides standard ¥599 rolls on the big sites and the same at local distributor’s shop. Translating and reading up on one "Eco" labelled product's JIS safety data sheet I was not convinced of its safety. So, what about tapes that ensure health, comfort, product longevity and energy reduction, aka lower energy bill? 

 

For products that deliver on the above I have turned my attention to one producer, Siga Swiss, for an upcoming Passive House project in Hokkaido. Why? Because they hit all of the above targets and more. The additional parts: Siga Swiss offers customizable solutions, transparent product info, computer simulated evaluations of your project followed by recommendations, and provide training on best methods of application. They are committed to doing their part globally and making sure it is done right.

 

These are the kinds of products we need to be using on our projects in Japan to get ahead and help push the world out of the dinosaur climate age. To do this, when speaking with suppliers, architects, and engineers ask whether a specific high performance product is available in Japan. like Siga Swiss for airtightness. This will get conversations started and ideas flowing as well as help toward a better educated industry along with comfier, cheaper, and better-built homes. Demand for better products can positively affect availability here in Japan. 

Of course, regarding any products that are pushing for similar goals already here in Japan please share and let’s discuss those too! Positive change works a lot better helping each other out. 

 

One final note. Alluding to traditional builds in a previous article on this site: “Yes we can!” If we keep these themes while blending traditional styles with new building techniques, technologies and products that make homes hit higher targets, specifically high-performance airtight tapes and membranes. These targets will be on the way to “2050 goals” rather than just words.

Are you positive wool is carbon negative?

I'm trying to understand the carbon footprint of buildings, and I always hit a mental roadblock when I see negative numbers. This just struck me on a list of insulation materials where wool was sticking out of the wrong side of the graph. There are also negative carbon footprints for cellulose fibre and cork. This negative accounting applies not only to insulation products but also structural materials such as wood.

Wood is certainly a great material to build with, and is definitely going to emit less carbon into the atmosphere than concrete, steel or glass. It also contains more carbon, and any atom of carbon in the building is one less molecule of carbon dioxide or methane in the atmosphere. But does that make its impact negative?

I have a couple of thought experiments that make me skeptical. First, what if you used twice as much wood on a building project?

If wood is carbon negative, then more wood would reduce the carbon footprint of the building. So just sticking a load of extra planks around the building would make it more "green", even if you use the same amount of concrete, steel and glass. Or you could just deliver the wood to the site and leave it in a pile on the ground. But you've cut down twice as many trees, so how can that be better?

Next thought experiment: what if every man-made structure used wood?

This would be impossible because human structures outweigh biomass. You would run out of trees, and all other living things. The planet is not a factory and you can't just increase production because there is more demand. Tree growth is limited by the amount of sunlight that falls on the trees, the area their roots have to grow into, and their access to water. Trees can take decades to grow and absorb the carbon stored in them. We have to be careful with our applications of economic calculations on natural systems.

So I'm starting off sceptical of a negative carbon impact for wood, which is made from plants that spend their life absorbing carbon from the atmosphere. What about wool? That comes from animals which spend their life emitting carbon dioxide and methane. But wool is also listed on the negative side of the carbon impacts.

Of course wool contains carbon and that carbon comes from grass, and the grass has captured the carbon from the atmosphere. So I guess you could argue that the carbon is being sequestered and stored in the building rather than being left in the atmosphere. That's lovely, but at what cost?

Sheep are warm-blooded animals, which means that most of the calories they consume go into maintaining their body heat. Even though they are wearing highly insulating fleeces over 80% of their calorie intake goes into keeping warm. Given that they are walking around and growing fat and muscle, it's hard to imagine more than a couple of percent of those green carbs they are eating going into wool.

I could do some calculations on the back of an envelope, but instead I looked at published research papers. Brock et al. (2013) looked at a farm in New South Wales and estimated 25 kg of CO2e (carbon dioxide equivalent) per kg of wool at the farm gate. A study on farms in Patagonia by Peri et al. (2020) estimated around 8-19 kg CO2e per kg of wool. 

CO2 is made up of one carbon atom and two oxygen atoms, so burning a kilogram of carbon will give us about 3.7 kg of carbon dioxide, or living things will turn 3.7kg of atmospheric carbon dioxide into one kilogram of biological carbon. So even on a good day, assuming that sheep's wool is 100% carbon, taking the lowest figure in those studies, and ignoring manufacture and transport, for each kg of wool in the building there would be well over two kg going into the atmosphere. Am I missing something? 

I was only thinking about sheep working to produce wool, but of course they produce meat as well. Both papers note that meat production changes the estimate, which accounts for some of the range in the second study.

Sheep not only produce wool and meat, they also have other effects for land management. They are excellent at deforestation. Even if they cannot cut down trees, they will eat any saplings before they can grow and make sure that the trees never grow back.

Sheep farming:
Causing deforestation for at least six millennia 

You can see in the background of this picture from the Campaign for Wool "Why to use wool insulation." It should be titled, "Sheep farming: Causing deforestation for at least six millennia!" People talk about wolves in sheep's clothing, but in terms of ecological impact: compared to sheep the wolf is a lamb. Historically speaking this has been very helpful as sheep have cleared the way for other kinds of agriculture and for urban development. We are now in different times. As an Englishman these rolling hills with drystone walls and woolly sheep seem like a perfect rural scene, but it is as man-made as a concrete jungle.

Of course using wool insulation in a building is going to lead to less energy use in your house, like any other insulation. Using insulation is almost certainly a better choice than not using insulation, which would force the inhabitants of the building to use more energy to stay warm or cool. But that is a choice between two different energy uses. You can use all the insulation in the world, and your heating bills are never going to be negative.

And wool may be a lower-carbon option than other insulation materials such as polyurethane or extruded polystyrene. But you may not want to use wool underneath your foundation, and you may find that higher performing insulators can be thinner, which may reduce the need for other building materials.

I don't want to suggest that wool is a bad insulator. Just let's be honest about its carbon impact, think a bit more about the ecological impact of sheep farming and give up with the brownie points.

Sequestering carbon is a good idea, and if we can find places to store carbon, that will help keep it out of the atmosphere. But negative numbers don't exist in the real world. I don't think we can ever make a truly carbon-negative building, any more than we can generate energy by taking carbon out of the atmosphere.

We can just try to reduce the impact as much as possible.

References

Photo from: 

Campaign for Wool (2020). Why use wool insulation in your home? http://www.campaignforwool.org/why-use-wool-insulation-in-your-home/

Jan Zalasiewicz, Mark Williams, Colin N Waters, Anthony D Barnosky, John Palmesino, Ann-Sofi Rönnskog, Matt Edgeworth, Cath Neal, Alejandro Cearreta, Erle C Ellis, Jacques Grinevald, Peter Haff, Juliana A Ivar do Sul, Catherine Jeandel, Reinhold Leinfelder, John R McNeill, Eric Odada, Naomi Oreskes, Simon James Price, Andrew Revkin, Will Steffen, Colin Summerhayes, Davor Vidas, Scott Wing, & Alexander P Wolfe (2016) Scale and diversity of the physical technosphere: A geological perspective. The Anthropocene Review, vol. 4(1), 9-22. https://journals.sagepub.com/doi/full/10.1177/2053019616677743

Yinon M. Bar-On, Rob Phillips, & Ron Milo (2018) The biomass distribution on Earth. PNAS, 115 (25) 6506-6511; first published May 21, 2018; https://doi.org/10.1073/pnas.1711842115 https://www.pnas.org/content/115/25/6506 

Brock, Philippa M., Graham, Phillip, Madden, Patrick, & Alcock, Douglas J. (2014). Greenhouse gas emissions profile for 1 kg of wool produced in the Yass Region, New South Wales: A Life Cycle Assessment approach. Animal production science, 53(6). https://www.researchgate.net/publication/268631844_Greenhouse_gas_emissions_profile_for_1_kg_of_wool_produced_in_the_Yass_Region_New_South_Wales_A_Life_Cycle_Assessment_approach 

Pablo L. Peri, Yamina M. Rosas, Brenton Ladd, Ricardo Díaz-Delgado, & Guillermo Martínez Pastur (2020). Carbon Footprint of Lamb and Wool Production at Farm Gate and the Regional Scale in Southern Patagonia. Sustainability,12(8), 3077. https://www.mdpi.com/2071-1050/12/8/3077 

Hydrogen. Really?

Green hydrogen may be the solution to a cleaner carbon-free future, or it may just be another bit of greenwashing from the fossil fuel industry that will make no real difference but let them carry on as normal. My initial hunch is that it's not a solution. Rough calculations and careful research also suggest that it's only a good idea if you want to keep selling gas and pumping oil out of the ground. Who on earth would want to do that? 

In theory it sounds great. Hydrogen is literally floating around in the ocean and all we need to do is snip off those oxygen atoms. Then we can burn the hydrogen and it will just give off clean water.

Getting hydrogen out of water is simple: you just need to pass electricity through it. The molecules will break up, oxygen will bubble up from the anode and hydrogen will bubble up from the cathode. I tried that when I was a school kid, after hearing the squeaky pop in a science classroom. In practice it's not as easy as just taking the Os off the H2 atoms. Not everything that is simple is easy. To get electricity to pass through the water you have to add a bit of salt, otherwise it doesn't really conduct. This means you have sodium and chlorine in the mix and start getting some build up of chemicals and noxious gases coming off the electrodes. This was Ok for a little after-school science experiment but to do this on a larger scale there are more complications. 

Picture from Walt Disney,
I mean Penn State University

Actually it probably wasn't that good an idea for a child to do since you're also going to get some chlorine gas coming off the anode, which is deadly poisonous. The sodium ends up as sodium hydroxide which is highly corrosive, or can act as an insulating coating on the electrode. In fact electrolysis does not split the H2O into H2 and O; it actually splits it into H and OH, but I don't want to get into too much chemistry. My own experiment stopped working after a while, and I had to replace the electrodes. A large-scale application needs an electrolyte that will let the electrodes keep working without regular replacement or cleaning. 

The most critical difference with the real world is that I wasn't worried about how much electricity I was using in my experiments. This was only a small fraction of our household use and my parents were paying the bill anyway—it would be at least ten years before I took an electricity bill seriously. And only a small fraction of that electrical energy was going into the splitting of those chemical bonds with most of it probably just warming up the water. I was really only interested in the squeaky pop when I burnt a small collection of hydrogen and not the amount of energy it would release when burning.

Energy is the biggest consideration if we're talking about Hydrogen for energy use in a real-world application. Chemical energy is all in the electrons and the energy required or released when a chemical reaction happens. So energy is required to split two hydrogen atoms from the oxygen atom. You get energy back when the two hydrogen atoms combine with an oxygen atom, but you will never get back all the energy you put in. Are you keeping track of all these inefficiencies?

Also, you need to collect and store the hydrogen, then transport it. It would be lovely to put the hydrogen into bags and send them floating to where they are needed. There was some experience with floating bags of hydrogen up to the 1930s which I will come back to later. More likely you'll need a compressor, which will use more energy but will make it easier to store in terms of space and perhaps easier to transport in gas bottles.

Quick reality check: the energy in the hydrogen is just in the electrons, and if you're thinking of transporting that hydrogen it may be a lot less efficient than just using electricity, which sends the electrons only. It's the difference between sending an email and printing out the email and sending it as a letter. When people say that hydrogen is the future of energy, you have to wonder whether letters are the future of communication.

Until now commercial hydrogen has not been made from electrolysis, it is produced by steam cracking fossil fuel gas, which is some combination of carbon and hydrogen atoms, and then throwing the carbon away, usually in the form of CO2. This is called "Grey Hydrogen" and produces more global warming gases than just burning the fossil fuel gas.

"Blue Hydrogen" is split from fossil fuels, but the carbon is captured, which in theory means there is no carbon. However, some of the carbon escapes rather than being captured, and since carbon-capture also uses energy, this still ends up being worse than just burning the fossil fuels in the first place. It's not as bad as grey carbon, but it's still worse than burning coal.

Some companies are also making electrolysers so renewable energy can be turned into "Green Hydrogen". This is probably going to produce less carbon than Blue Hydrogen, but it depends on the electricity being low carbon to start with, and I'm really not sure if it's better than sending the electricity over the existing grid, or putting it into batteries.

We haven't even talked about using the hydrogen yet. To be honest I can already see enough problems above to write off hydrogen as an energy source because it's going to use so much energy to make.

Hydrogen is a gas. Natural gas is a gas. So we can just use it the same way. Right?

Again there are a few problems to work out. Hydrogen has much smaller molecules than natural gas, so it has more chance of leaking. Also it's much more reactive, and will react with most kinds of steel so you need to make sure the pipes and cookers or boilers are free of steel.

Of course hydrogen does not produce Carbon oxides when burnt, which is great, but it can produce six times more nitrous oxides as it burns more of the nitrogen in the air. At a local level NOx are already much more dangerous pollutants than Carbon dioxide.

What about vehicles?

Using hydrogen in an internal combustion engine is also not impossible, as long as you first get over those issues of leakage, reaction and pollution. Since internal combustion engines are not very efficient it turns out to be much better to use a fuel cell to turn hydrogen and oxygen back into water and release electricity, then use an electric motor. If you have an electric motor, please remind me why we're not just using a battery? We have battery technology, and there is already a grid to get it around wherever people go, and connect it to sources of renewable energy. And you would probably want a small battery at least in your vehicle to handle some energy recovery braking with the electric motors.

To summarise, conventional "grey" hydrogen is a carbon disaster. "Blue Hydrogen" produces more carbon than just burning the fossil fuels. "Green" hydrogen may be possible from renewable energy but is not likely to be very efficient. Different infrastructure and units will be needed to use hydrogen domestically or commercially instead of natural gas. For transport it will make most sense with fuel cells and electric motors. So why not just use batteries?

As for transporting hydrogen around the world, bags of hydrogen were floating around in the 1920s and 1930s. Airships may seem like a ridiculous way to travel, but the first round-the-world flight was in an airship, as was the first aircraft to clock up a million miles and the first scheduled transatlantic air crossings, which knocked days off the alternative ocean liners. Until the 1940s travelling a long distance by fixed wing plane would have seemed as realistic as travelling by space shuttle did in the 1990s.

A few high-profile airship accidents helped bring down the airship as the future of long-distance transport, but in the end it was probably the second world war that brought their era to an end. Switching from hydrogen to helium would have made the airships much safer, but the airship technology was mostly in Germany and trade became difficult with the United States which had all the helium. More critically, the war came and a fight between a fixed-wing plane and an airship is something like a fight between Mike Tyson and a piece of damp tissue paper, so technical development went into aircraft of increasing speed and size. The passenger jets that arrived after the war resulted from developments that were driven by the need to fight and flee more quickly and to carry more and larger bombs.

Back in the 1920s when the R100 was being designed, they considered using an engine that could switch between diesel and hydrogen. Airships usually got their lift from hydrogen and their thrust from diesel engines. As a journey went on the diesel would burn away and the airship would get lighter. In order to descend they would need to release some hydrogen. Rather than throwing it away, it would make more sense to burn the hydrogen in one of the engines.

They did not develop hydrogen engines even when they were literally carrying around bags of hydrogen that they were going to throw away. There is some evidence that we are much cleverer now and could easily come up with hydrogen engines, but I don't think the evidence is very strong.

References

Hydrogen: Get-out-of-Jail-free card for the building industry?
https://energymonitor.ai/tech/built-environment/building-insulation-is-hydrogen-our-get-out-of-jail-free-card?s=03

"the greenhouse gas footprint of blue hydrogen is more than 20 percent greater than burning natural gas or coal for heat and some 60 percent greater than burning diesel oil for heat,"
https://onlinelibrary.wiley.com/doi/full/10.1002/ese3.956

"Two European studies have found that burning hydrogen-enriched natural gas in an industrial setting can lead to NOx emissions up to six times that of methane"
https://www.cleanegroup.org/hydrogen-hype-in-the-air

ITM power is set to leave blue hydrogen in the dust by producing electrolyers as cheap as £500,000 per Mega Watt. (This compares to the cost of solar panels at around £700,000-£1.3 million per Mega Watt
https://www.rechargenews.com/energy-transition/green-hydrogen-itm-power-s-new-gigafactory-will-cut-costs-of-electrolysers-by-almost-40-/2-1-948190

Thinking of Getting a Wood Burning Stove?

There is something magical about wood fires, and people are often tempted to put them into their houses. In writing on low energy building, I haven't really talked about wood burning stoves. People sometimes ask how you can fit a wood burning stove in a low energy building, but the question you first need to answer is: why do you want a wood burning stove?

Before you get one for your house, and especially before you plan to build a new house around a wood burner, you should check that you meet at least four or five of these seven criteria. You don't have to meet all the criteria, and in fact some of them may contradict each other. But you should meet most of them.

1. You have a sustainable source of wood.

Perhaps you live in a forest, or a relative has an orchard, or you live next to a timber yard, or you just inherited a derelict warehouse with a large collection of broken pallets. If you don't know where your wood is going to come from, then you will need to buy it. You may have thought that wood grows on trees. In fact wood does grow on trees, but those trees grow on land, and that land usually belongs to someone. The trees also play a major role in creating habitat for wildlife, and are acting as a sink of atmospheric carbon and a source of oxygen. 

Well-managed forest can provide better habitat for wildlife and can provide more effective carbon sinks, but burning wood will send some of the carbon that has been stored over the last decades or centuries straight back into the atmosphere. Even if the forests are well managed, burning the wood that grows there may not be the best use of it. If left on the forest floor, wood can provide excellent nutrition for the forest and habitat for some of the diverse life there. 

Not really firewood!

So wood may not be the best fuel for your house in terms of economics or ecology.

 

Or it may be the best thing in terms of economics and ecology. 

I don't know the answer, but if you're thinking of using wood, please find out!

2. You like chopping and storing wood, making fires and cleaning stoves and chimneys.

Having a wood burning stove is a lifestyle choice. That's another way of saying that it will take more time, cost more money and may be worse than the alternatives in various other ways. Wood needs to be chopped and stored where it will stay long enough to dry out, but not too long in the same place where it will attract insects and other undesirables. If you only occasionally want to burn stuff, it may be better to go camping. There are some great campsites that allow you to have a fire!

3. You have no neighbours.

You may be planning to go off-grid, which is a great idea if you live away from civilisation, and this may go hand-in-hand with the first criteria. If you are in a residential area, your neighbours may not appreciate smoke getting into their washing. This article in the Huffington Post suggested that the most efficient wood-burning stove will put out the same levels of pollution as 18 diesel cars. Would you like a fleet of cars driving around your neighbourhood?

4. You are going to get the most efficient model available, with a properly installed chimney.

Benjamin Franklin did make significant improvements to stove design back in the 1700s, but even in the 1800s wood burning stoves were only 30% efficient. They sent out particles at levels that would be illegal today, and allowed creosote to build up in chimneys, creating a fire hazard.

Things have got better since the 1800s but even the most efficient wood burning stove will only burn wood at around 80% efficiency. 

5. Your wood burning stove can run on pellets.

Part of the problem is the wood itself. It seems that wood was not designed with burning efficiency as the first priority. Wood pellets provide a more even fuel and allow higher efficiency. Many wood pellets are currently made from sawdust or waste wood products. There are also pellets made from grass cuttings. If demand increases, wood will be cut directly to make pellets, which may remove some of the supply-end energy efficiency, but they will still burn cleaner. 

More efficiency means more of the wood is turned into water and carbon dioxide, rather than other more polluting substances or unburnt particles or residues. So more efficiency means less pollution and less cleaning. Air quality is an issue in many places, and burning wood certainly does not improve it.

You may consider a dedicated pellet burner, which will be easier to clean, and easier to use since it feeds the pellets via a hopper and may be controlled by a thermostat and a timer. It will probably be cheaper to install since the unit usually has a heat exchanger so a simpler chimney can be used. If you're still wondering about the answer to question 1, wood pellets could be your answer. 

6. You are only going to light your stove a few times a year, and are mostly getting the stove because it will look nice in your living room.

If you're thinking of adding a wood-burning stove to a ready-built house, you may not need to worry about this question. But if you're building new, I recommend your first priority to be insulation rather than burning wood.

Depending on your climate, if you have a well-insulated house, most wood burning stoves will make your house overheat, except on the coldest few days of the year. Your well-insulated house should also be airtight, and this may not be sensible if you are burning wood.

7. You know that if burning wood was the best way to stay warm, everyone would still be using it.

Most of us no longer send telegrams, spin yarn on spinning wheels, or nip down to the local smithy to get a horse shoe fixed. We stopped doing these things because of new technology that is cheaper and more time-effective. Burning wood will likely be more expensive and more time consuming than the options. Wood was our first fuel source; if wood produced more energy than fossil fuel reserves, we would never have deforested vast areas of the planet to mine coal or pipe oil and gas. 

There is an old saying: if God had not intended us to burn wood, he would never have invented matches. Actually that's not an old saying at all, I just made it up. But there is something natural and wholesome about a wood fire. 

Burning wood is better for the carbon cycle than burning fossil fuels. However, it may be better to burn nothing. If you want to avoid or reduce fossil fuel use, the first thing you need to do is improve your insulation. Then it may be better to electrify your heating, which allows you to use renewable energy. 

If you see yourself as an eco-warrior and see fire as one of your weapons against the machine, then be aware of the possibility that with fire you are fighting against ecology rather than fighting for it! I know in the situation we are in, the choice between wood burning or electrified heating may be something like choosing between a bicycle and a skateboard as you prepare to go over a waterfall. 

I don't have all the answers, but I do have the questions! 

So how did you score? If you answered yes to most of them, you're good to go. If not, I recommend looking into heat pumps, either in self-contained air conditioning units, or producing hot water for radiators or underfloor piping.

Remember, taken in moderation, wood burning stoves can form part of a calorie-controlled energy diet for your planet!

References:

If you want to get a stove, go to Michael's Stove Shop.

For recent developments, analysis of factors that effect efficiency and a call to get below 1g of particulate per kg of wood, see "Performance history and further improvement potential for wood stove" by Øyvind Skreiberg & Morten Seljeskog (2019) in Chemical Engineering Transactions, 65. pp. 199-204.)

More details from the US Office of Energy Efficiency and Renewable Energy: Choosing and Installing Wood- and Pellet-Burning Appliances

Chapter on Energy Return on Investment (EROI) of Different Wood Products by Zdravko Pandur, Marijan Šušnjar, Marko Zorić, Hrvoje Nevečerel and Dubravko Horvat (2015)

Guardian 16th February, 2021: Wood burning at home now biggest cause of UK particle pollution