Long term solution to carbon storage with oak heat battery houses.
The start of 2020 seems to be a good time to envisage the
future. What will housing look like in 2100? How will we build low impact, warm
houses that also act as a carbon store? We have understood super insulation
combined with thermal mass and passive design is key to achieving warmth
through the winter and “coolth” in the summer but how can you do this and deliver
low impact and a carbon store? Here is a vision of how we might achieve these
things….
I hope we will tackle
the climate crisis swiftly and decisively this year and over the coming years.
Part of this will include a massive tree
planting campaign which will absorb carbon, create wildlife habitats and oddly
a dilemma. For the carbon absorbed by these trees to be truly removed from the
atmosphere the wood will need to be kept rather than let rot back into the
ground at the end of the tree’s life. I have been considering how in the future
we might achieve this and solve some of the housing need questions raised
above. In the following discussion I’m going to assume the benefit of high
internal thermal
mass is taken for read as we have covered this in depth in other articles.
I was quite surprised recently to discover that the specific heat of wood can be more than that of concrete. This could mean we can substitute high density wood for example oak for concrete in our high thermal mass housing design. (Light bulb moment!) The wood would need to be grown and in doing so would absorb carbon from the atmosphere. (And create wonderful wildlife habitats.) By using this wood in the construction of houses we would be locking up the carbon for many extra years as houses should last a very long time.
What would a high thermal wood mass, super insulated house
look like? The penalty of using wood instead of concrete is that the density of
oak is about a third of that of concrete. This means more of it would have to
be used inside the insulated envelope to store the same amount of energy. However,
because it has a higher specific heat than that of concrete the net result would
be that about double the volume would be required. The sacrifice here would
possibly be lower internal floor space however this effect could be mitigated
by using more wood in the floors and ceilings. In effect the house could be
very similar to the Hockerton Houses but with a slightly smaller floor – area
may be 6% less.Of course, the practicalities of building in oak rather
than concrete would be quite different and the material supply chain would take
a long time to become sustainable. The benefits of substituting oak for
concrete would be enormous though.
To finish let me emphasise that I am not suggesting building
timber frame houses out of oak with insulation within the walls as this would
not be able to store heat. A heat
battery for a house needs to have internal mass surrounded by insulation on
the outside of the building envelope. The configuration I am proposing is a
thick oak structure with insulation outside this with no cold bridges of oak or
any other material across the insulation layer.
Some of the background detail: Specific heat is basically a measure of how much heat energy a material can contain. The density is how much of a material you can fit into a certain space. The heat figure ranges I saw for concrete were 840 J/kg·K to 1800 J/kg·K (Kodur, Properties of Concrete at Elevated Temperatures, 2014) and for wood the range was 1300 J/kg·K to 2500 J/kg·K with oak being 2400 J/kg·K (EngineeringToolbox, n.d.). This makes oak a third better than the best capacity concrete. Obviously the density of these materials plays a role as well so for completeness a high density concrete might be 2300 kg/m3 (Guo, n.d.) The density density of oak varies but typically English Brown Oak is 740 kg/m3 (EngineeringToolbox, n.d.). So, comparing concrete and oak by volume, one cubic meter of concrete could store for each degree of temperature rise 4.1MJ and wood 1.8MJ. (The arithmetic 2300 x 1800 = 4.1x 106 and 740 x 2400 = 1.8 x 106). Our explanation of how heat battery works can be found three videos down. A pine building product of cross laminated timber (CLT) is available and is well understood. CLT has the ability to store heat if configured correctly but is less dense than oak.
Incidentally I would encourage you to become a member of the Woodland Trust to help support tree planting initiatives. HHP is a member of the charter branch network. Hands up here my daughter now works there! Hockerton Housing Project has become a tree charter group and is focusing on planting trees where it can. Come and see what we have done on one of our Sustainable Living Tours of the project.
Guo, Z. (n.d.). https://www.sciencedirect.com/topics/engineering/concrete-density.
Kodur, V. (n.d.).
Kodur, V. (2014). Properties of Concrete at Elevated
Temperatures. International Scholarly Research Notices, 2014, 468510.
Retrieved 1 2, 2020, from https://hindawi.com/journals/isrn/2014/468510
Thought for the week: Simon Tilley on
the climate nightmare
I
don’t know about you, but most of my bad dreams seem to involve helplessness.
Here’s one: I’m a tall chap on a coach going down a motorway. I’ve got the seat
just behind the driver, with plenty of legroom, and I’m comfortable, even
serene. Then I become aware that in the distance just over the hill there’s a
pile-up. The driver hasn’t noticed – indeed he’s actually accelerating a bit.
I
do nothing; I’m sure he knows what he’s doing. But as we get closer, I see it
is quite a big pile-up, and he still doesn’t seem to have noticed. I wonder
whether I should speak up. In the end I say, in a conversational tone: ‘Looks
like there’s a bit of a prang up ahead.’ He makes no reply. I repeat myself a
bit louder, and two things happen. He says ‘It’s just a bit of congestion’ and
one of my fellow passengers nudges me and points to a sign saying: ‘Do not
speak to the driver while the vehicle is in motion.’ ‘Please be quiet,’ she
says, ‘it’s not safe to speak to the driver and you’re upsetting my friend.
’You
know how these things go; no one else appears to have clocked what is becoming
a really obvious disaster up ahead or, if they have, seem oblivious to the
danger. They go on chatting and reading and sleeping, and when I try to get
their attention, they just look at me as if I were a television. And the coach
continues to accelerate…
Amazingly
no one seems to hear. One or two of the other passengers are looking at me with
mild, bovine interest, but most are remonstrating with me for disrupting their
journey. We reach the prow of the hill and I notice break fluid escaping onto
the road…the hill starts to send quickly…..And then, with about a hundred yards
to go before we pile into the destruction ahead, the driver applies the brake
but they are soft and spongey, we start to slow but far too little and too late………….
This
is where I wake up, to that overwhelming feeling of relief that it was just a
dream.
I
usually ask myself what led up to that dream. Often there’s a logical
explanation, based somewhere in reality. When you’re asleep, your brain sorts
stuff you’ve been dealing with, re-runs it by and sorts out my emotional
response while you’re offline. I went on a coach to London recently for the
last People’s Vote march, and I’ve been reading a book about climate breakdown,
(There is No Planet-B by Mike Berners-Lee) so that explains that.
Except,
of course, that isn’t really a dream. When I wake I don’t get a surge of
relief, just a feeling of despair at the reality: the clear and unanswerable
fact that we are on the brink of irreversible climate breakdown; the knowledge
that, in their anxiety not to be alarmist the media often sits quiet, our
scientists understated the danger and the ongoing complacency of some of our
politicians is obvious, even when faced by the reality of fires in California
and Australia, famine in South Sudan and floods in Fishlake. And I wish I’d
pushed the driver out of the way and taken over the steering wheel myself
earlier. The prow of the hill and the leaking brake fluid must have represented
a tipping point beyond which we can not retreat. These are approaching but we don’t
know when.
Everything
I have done over the last two decades in Hockerton Housing Projector
have been Reasonable and Proper. I’ve written articles, spoken to the media,
talked with friends and family, had polite meetings with my MP, written letters
and signed petitions. All to no avail. So, I fear, perhaps it’s not time to
stay polite, but get arrested, to make the point. And dare to dream of a
hopeful future. Nonviolent direct action is starting to turn the tide, but we don’t
have long.
Every
action we take counts, where we bank, where we shop and for what, how we vote
and what we choose to eat, how high we have the heating and how far we travel.
A better future can be envisaged but we need to act and act to make it happen
now.
If
you want to find out about some practical steps you can take especially if your
interested in low energy housing, environmental education and or renewable
energy please contact me. Or if you’d like to look at our new videos on
sustainability please click here.
Truth, Action and Assembly: Quick update – if you are local and want to hear about the climate emergency and what to do about it please come along to one of the local XR event https://twitter.com/xrnewark The last one at Southwell Library – XR Talk – Heading for Extinction and what to do about it ! Thursday 21st November at 7PM was well attended with over 40 people turning up.
It would be great if all political candidates in the area could attend! Simon Tilley the speaker would love to see James Baggaley, Jay Henderson, Robert Jenrick and David Watts there to face the facts and start to act upon them!!
Forward from Luke: Hey! I’m excited to host Ed Revil (traveling up from his small holding in Swansea) at the Meanwood Community Farm in Leeds this Thursday 21st Nov 18-20.00 it will be an inspiring and challenging presentation from his 20 years experience of building soils, capturing carbon and producing food using DIY appropriate technology to make bio char. Hope to see you there! Luke
In this folder there are a 14 climate change related lesson plans that will encourage students to think more sustainably. I have summarised these lesson plans so that they can be easily used for teaching purposes when school groups make site-visits to Hockerton Housing Project. For example:
Lesson 2 – Donald Trump Climate Quotes and Climate Denial
Summary:
Fake News or ‘What Donald Trump Said’ activity – great activity about 15-20 mins long
BBC News article on psychology of climate change denial. Students need to read this and complete an activity sheet asking them to summarise the article.
Google Docs Outline:
Starter: Trump
or Fake News – Show students the quotes from Donald Trump relating to climate
change. Ask the students to decide whether the quote is ‘Trump’ or ‘Fake News’.
Use the information sheet to elaborate on the meaning of his words. Ask
students their opinion of Trump’s attitude? Should he be allowed to have these
views?
Scientific Consensus –
Why does Climate Denial still exist? Explain the animated graph showing
temperature models for a variety of organisations around the world all showing
a similar trend. 98% of scientific evidence suggests recent climate change is
manmade. Is there still a debate?
News Article –
Brain Biases. Direct students to read the BBC news article. Using the worksheet
students should read and then reread, pulling out different pieces of
information as they go.
What’s the main reason for our
inaction? – Students should rank the suggested factors
and in pairs, develop reasons for why they think this might be the most
powerful factor.
Open the document below too see my summary of all 14 lesson plans.
