Discharging of a Salesman

"Would you like to buy a battery?"

If you don't have time to read this, the quick answer is "no".

A new contract with a different energy company brings an opportunity for salesmen to visit. They had sent an engineer a couple of weeks earlier who checked my solar system, took some measurements and switched the power conditioners off and on a couple of times.

The conversation with the salesman went something like this:

"We tested your solar panels, the connection box and the power conditioners," he started, then went through each of the items in the checklist he showed me, all of which were good. "...and it's time for you to replace your power conditioners."

Me thinking: "hmm... what? If there are no problems with my system, doesn't that mean I can keep using it?"

"So when you do replace it, here are some things to think about," he went on. "Here, look at this folded A3 photocopy that has been carefully designed with boxes for me to write fancy-looking numbers in."

The first part was under the heading How much are storage batteries spreading?

"We've had storage batteries for FIVE years," he said, writing "5" in the first box, "and the country is spending THIRTEEN BILLION YEN per year on subsidies." Writing "130" next to the Japanese character 億 oku, which is one with 8 zeros. There's a divide sign next.

"And there's HALF A MILLION yen available per house," writing "50" and the character 万 man meaning one with 4 zeros. "Which means there are TWENTY SIX THOUSAND houses with batteries," writing 26,000 in the last box.

Me thinking: "couldn't you just have told me how many houses there were first? And how much I can get? Are you trying to turn this into an elementary school arithmetic lesson?"

He went on: "Now, how much have they been paying you for your electricity?"

"Forty eight yen per kilowatt hour," I told him. He wrote "48" under the next section Why should you get a storage battery?

"And you're probably only going to get between ZERO and SEVEN yen for selling your electricity." The Zero was already there on the paper with a squiggle next to it. He wrote "7" in the next box on the other side of the squiggle. There was a graph with the price falling from 48 yen in 2009 to about 28 yen in 2019 then straight to zero.

"That's pathetic!" he said. Well, he didn't say that, but he obviously wanted me to think it.

In fact, I was thinking: "Wait a minute, I thought you were paying me 10 yen. I mean, yeah, that's still pretty pathetic. What's really pathetic is your bit of paper. Couldn't you have updated it before photocopying it? I mean, it's a black and white A3 sheet. I appreciate you building electrical infrastructure that's going to last several years, but I'm not convinced that's the right approach for a sales pitch crib sheet. And couldn't you have done some basic research into the deal your company made with me? Or do you know something I don't know about that 10 yen? But do go on..."

That section on the crib sheet was about the fall in price of electricity sold. The next section was about the increase in the cost of electricity bought.

"So because of the nuclear problem the public has had to cover costs since 2020," he went on. writing "2020" in the box. "And because of natural disasters the price of electricity went up 31.1% in your area between 2011 and 2015," circling relevant parts of the table with various electric companies from around the country.

As he was saying this, already I was thinking: "Isn't increased renewable energy going to push prices down? You can't tell me with one breath that my solar electricity is worth nothing and then that prices are going to go up, can you?"

"And number 3, you're going to need a new power conditioner." Number 1 was the feed-in tarrif going down to zero and number 2 was the price of electricity going up. "You may not realise this, but the power conditioner is a very important part of your solar system."

I did realise.

"It does lots of things, and it's very important. And you probably need a new one around now."

Me: "..."

"And number 4, you're probably going to need a new IH cooker and to replace your Ecocute."

The Ecocute is the domestic hot water system, heated by an atmospheric heat pump. I'm wondering what that's got to do with anything, but he tells me.

"They both last around ten years. So while you're changing those things, you might as well just put in a storage battery, because that means you can store electricity when it's cheap and then use the electricity when it's expensive to buy."

"And by the way," he went on, "we have a special deal for-this-month-only where you can buy a new IH and an Ecocute and a new power conditioner along with a battery, and we'll give you a 300,000 yen discount."

So there's another piece of paper from a large domestic manufacturer with pictures of leaking spaghetti pipes from the boiler that wants to say "watch out for leaks", and a cooker with a cracked top that could say "watch out for leeks".

Another sheet of paper explains the post-FIT strategies, which seem to be categorised as CARRY ON AS BEFORE or GET A BATTERY, YOU IDIOT.

Back to the photocopy, the storage batteries range from 3 kWh, with a price of 1 to 1.5 million yen, up to 16 kWh with a price of 3 to 3.5 million.

I'm thinking that I have a second-hand Nissan Leaf outside that I got for a million yen. It has a 24kWh battery. And it has wheels and I can drive around in it if necessary. Am I missing something? Do these storage batteries have teleport machines, or are they just over-priced? I could get a new Leaf that has a 40 kWh battery for 4 million yen.

"So," he goes on, "I can come back later and talk to you and your wife about getting a battery. When is a good time to have an appointment?" He then got out a calendar with names of people written into many of the days. I couldn't help thinking that the names and times were all made up.

Until now, this "conversation" has mostly been paraphrasing what he said, and telling you what I was thinking. Now it was my turn to talk.

"I've got an electric car. I wonder if you have some technology that could use that for storing energy from the house?"

"Oh, you could probably get one of those but it would cost, like, a million yen."

"Well," I replied, "When I looked into it, there was one for 380,000 yen."

"Oh."

"As you can see from the results on my system I have a pretty big solar array, and this house is very well insulated and airtight, so in fact I generate about twice the electricity I use. Rather than a battery, what I really want is some smart tech in the house, so for example the boiler will make more hot water while the sun shines. Do you have something like that?"

Him thinking: "I've no idea. They just pay me to wear a clean shirt and fill in boxes on bits of paper."

I went on: "And if I did get a battery, it would have to be a lot bigger than 3kWh for me to be able to go off grid and cover my electricity if there's a power outage. Which, to be honest, has maybe only happened once in the last ten years, and only for a short time." It was fun, we got to use our camping lights in the house. No time to break out the camping stove because the electricity for the cooker was back on in time for tea. 

"So I'm not really worried about protection against disaster. And I don't really want to go off grid, because as I said I'm generating more electricity than I use, so I'd like to send it back into the grid so somebody else can use it."

I didn't have time to do a financial check on the price of the battery, but looking now, I've spent around a million yen buying electricity in the ten years since I moved into the house. During this time I've been trying to use as little of my solar power as possible since I was getting a good rate selling it. Going forward I should be using more of my own power, so my electricity bill should be less. Spending a million yen on a 3kWh battery may reduce my electricity a little, but it would not go to zero since there are days with no sunshine when we will use more than 3kWh. I don't even need an envelope to write on the back of to work out that the payback is over 10 years, and probably well over 10 years, if you ignore any kickbacks. They would have to be serious kickbacks to make me think about it on purely financial terms. More precise calculations on the financial value of storage batteries will need to wait for another post.

Also, it's important to say that storing electricity does seem like a good idea in general, but I'm not convinced I should be doing it now, in my house.

"Thank you for coming."

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