Spring is just around the corner and if you are thinking
about pruning your apple and pear trees before the sap rises, we are running a
training course for you. The tutor is Marc Richmond who prunes many of the
orchards around her . Last year his training day was extremely good and is
highly recommended. You can book onto our pruning course
here on the 8th February.
My son Luke is organising a workshop on soil health in
conjunction with the Land Workers Alliance in Leeds so if you are north of here
this might be one for you. The event will look at how we can improve soils and take
a problem-solving approach. Visits to two local farms in the area will take
place the Sunday in conjunction with the LWA. Book here on soil
health 1st February.
We are running a course on Sustainable Living at Hockerton Housing
Project 7th March and places have nearly all gone so do consider
booking soon if you’re planning to come. Book now on
Later in the year there is a farm hack events
in Meanwood urban farm, Leeds. Here you will need an idea to make some
equipment for a farm/small holding/allotment or share a skill with others. A
skilled tutor with a load of equipment will facilitate making your idea if
appropriate. This will happen over the weekend of 6th March.
Every 2nd Tuesday of the month people are
gathering in Southwell to discuss positive “green” actions. Meeting in the
Admiral Rodney around 8pm please join Green Drinks then. The next
meeting is 11th February 2020.
If you have a group that wants to visit Hockerton Housing Project
you can design
your own tour and set the date. We also run remote
tours especially suitable for schools who have limited budget and a lot of
children. These include a live “skype” tour around a house with one of the
project members and a package of specific films on various topics with activity
We are running a repeat of the very successful peg loom
workshop we ran last year. Here you will make a natural wool rug and take home
the loom to make as many more as you wish, please contact us for
more information. 22nd February 2020.
And finally if you want to know more about us our shop has a
sale on with all our book
chapters reduced to 50p each, loads of good detailed analyse for you.
We have a climate emergency to tackle and tactics start now!
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
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
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.
I will be discussing how sustainable houses are delivered in
Westminster on the 29th January. Please come and join the event. Other speakers
· Lord Best, Social Housing Leader, House
· James Harris MA MSC, Policy and
Networks Manager, Royal Town Planning Institute
· Barry Goodchild, Professor of Housing
and Urban Planning, Sheffield Hallam University
· Anthony Probert, Programme Manager, Bioregional
· Stewart Clements, Director, Heating
and Hotwater Industry Council (HHIC)
· Dr Steffie Broer, Director, Bright
· Rene Sommer Lindsay, Urban Designer
and Strategic Advisor, R|S|L|ENT
· Simon Tilley, Director, Hockerton
· Emma Fletcher, Chair, Swaffham
Prior Community Land Trust
· Mikhail Riches Architects
Thanks for listening your comments
would be welcome!
Mr S Tilley, CEng MEng MIMechE
Director, Hockerton Housing Project Trading Ltd
NOTES on the Climate Crisis:
National Geographic: Sea level rise, explained:
BBC: Australia bushfires north of Sydney ‘too big to put out’:
BBC: Hundreds of temperature records broken over summer:
38 Degrees: DEFRA consultation on Environmental Principles and Governance after
the United Kingdom leaves the European Union: Summary report of responses from
80,826 members of the public collected by 38 Degrees:
EngineeringToolbox. (n.d.). https://www.engineeringtoolbox.com/specific-heat-capacity-d_391.html.
EngineeringToolbox. (n.d.). https://www.engineeringtoolbox.com/wood-density-d_40.html.
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