Below is a quick reference of the benefits of clay plasters!
Environmental benefits of clay plaster
if you make your own base plaster, material can be sourced locally, with lower or no transport costs / emissions
unlike gypsum (and lime, although lime re-absorbs CO2 on setting), no firing required, so lower energy use / emissions
clay doesn’t set chemically like gypsum does – it just dries; so at least for the base coat, if it dries, you can wet it and knock it back up again, which means less waste
no nasty chemicals
Benefits for the building
breathability: clay plasters prevent excess moisture in vulnerable buildings. Clays are hygroscopic – they absorb moisture if humidity is high, hold it without being damaged, and when humidity falls, release moisture back to the air. So they maintain a consistent humidity, and minimise damp, and moulds caused by condensation
gypsum on the other hand absorbs moisture, but it’s not breathable, as it doesn’t let moisture out again, and it gets damaged in the process – it moulds, and / or the plaster can blow, and fall off
clays can be used with / over other breathable materials without taking away their breathability
flexibility: clay is soft and pliable, and can move, like lime, without cracking; it can cope with situations where you get minor movements, and so is excellent in old houses
gypsum on the other hand is not flexible, and cracks with any minor movements
protection of timbers: lime absorbs moisture through capillary action, but with clay, there is a chemical attraction that draws moisture in – and because clay absorbs moisture at a faster rate than lime or timber, it takes moisture away from the timbers of the building, protecting them from damp, mould, rot and insects
plus as clay absorbs moisture, it seals and prevents water from passing right through into the structure of the building. Moisture is held and released when the air around it dries. This is why clay can be used to line a pond – clay allows so much moisture in and then provides a barrier
aesthetic: clay plasters are beautiful in their texture and the way they reflect light, and they have an organic, natural feel.
Health benefits from using clay plaster
clay plasters maintain a consistent relative humidity of around 50-60%, which is beneficial for people with asthma or other respiratory problems, but detrimental to dust mites, which reduces problems associated with allergies
they contain no nasty chemicals, and are able to absorb toxins and thus improve indoor air quality. Of course, you’ll try not to use toxic cleaners or buy toxic househould products, but in this day and age, it’s difficult to avoid toxins completely, and so clay plasters can help
you have to be in a room with a clay plaster to understand how beautiful, sensuous, natural, earthy (add your own epithet here) they are. They just make you feel good
Clayfest 2017, 12-17th June, Lincoln Castle, Lincoln, UK
EBUKI have just announced this years’ Clayfest and conference. This year to be held in Lincoln, home of the ‘mud and stud’ building technique.
Workshops at Clayfest
The workshops cover a broad range of topics taught by the experts in their fields, topics including:
Light-Earth Construction; Clay and Natural Fibre Composites
Earth, earth-lime and hot mixed lime mortars
The Steppe Oven: Food Without Wood
Earth and Fibre: Experiments with Forms and Finishes
Mud and Stud
Cob Workshop, Basics to Mobius Strip
Earth Plasters, Decoration, Colour and Textures..
Earth Building UK & Ireland Conference 2017
Conference this year continues with the theme of Clayfest, building bridges. How do we respect tradition, learn from tradition, teach tradition, adapt tradition to bring a new generation of builders, designers, developers and clients to a better understanding and respect for materials which have almost perfect credentials in the circular economy, cradle to cradle materials which can be used and re-used almost indefinitely. Earth as a material has powerful properties and yet what people too often think of are it’s weaknesses. Other building materials also have weaknesses but have been more successful in projecting their strengths, what can we learn from this and how do we project that knowledge and understanding? Hearing from speakers working in and out of the earth building world we will plot a course to better understanding, better networks, building bridges to better building.
It’s sure to be a great week, hopefully I’ll see you there!
When we are talking about our design and material choices in a natural home, we often discuss the embodied energy. This can be defined as:
Embodied energy is the energy consumed by all of the processes associated with the production of a building, from the mining and processing of natural resources to manufacturing, transport and product delivery. Embodied energy does not include the operation and disposal of the building material, which would be considered in a life cycle approach. Embodied energy is the ‘upstream’ or ‘front-end’ component of the life cycle impact of a home.
Why does Embodied Energy Matter?
I once wrote to a well-known insulation manufacturer asking for their calculations on the embodied energy in their product. The reply came back that insulation doesn’t have an embodied energy because it saves you energy. Alarming no?
So if I build a house with the most energy intensive insulation available, and I mean really fill the house with the stuff, way over code. The fact that the building may cost the earth practically nothing to heat and cool over its lifetime… is massively overshadowed by the enormous energy debt the house is in to start with. Even if the house exists for 200 years it might never pay off its initial construction debt.
Like this author, they conclude that the only way to seriously reduce our life cycle energy cost is to live in smaller apartments downtown, but that is another slideshow.
But when you look at the list of materials in the passive house they studied (on TreeHugger here) you see it is full of 135 cubic meters of polyurethane foam insulation, sixty cubic meters of concrete, clay brick cladding and clay tile roof. There is a seriously high amount of embodied energy and carbon in this house.
Read more in this great slideshow from Lloyd Alter @ treehugger –
A nice little article in National Geographic about green & healthy homes
That influence stems from a startling stat: Americans spend an average of nearly 90 percent of their time indoors, according to the Environmental Protection Agency. Yet what we breathe indoors is on average two to five times more toxic than what is typically outside, the agency warns, because of poor ventilation and off-gassing of toxic chemicals from a host of products, from carpeting to furniture.
Thermofloc is a natural floor insulation. Made from cellulose that has added minerals to make it fire retardant. It is simple to install and is much more affordable than any other natural insulation we found.
To break apart the insulation blocks we used a double whisk mortar mixer. By using an online calculator to work out how much we needed for our floor dimensions, we could be sure to achieve the correct density and therefore U-value.
NaturePlus – Thermofloc is the first cellulose insulation to be awarded the coveted NaturePlus mark of quality and sustainability.
Laid density of 40kg/m3
Thermal conductivity 0.039W/mK
Fire classification as per EN13501-1
Free of hazardous substances as defined by ETA-05-0186
Assessments show Thermofloc does not provide a suitable habitat for rodents and as such rodents will avoid nesting within the insulation.
In straw bale building we use a few key techniques that are unique to the trade.
Around our windows we have posts, so we need to put a notch in our bales to fit them snugly.
We do this using a Dewalt Alligator saw which is made for cutting building blocks, wood, drywall, insulation and Class 12 clay blocks. It also cuts straw bale very nicely, without throwing up a lot of dust.
I have also used a chainsaw to do this job. While the chainsaw does do an excellent job, it’s certainly more dangerous and a lot louder, plus throws dust into the air.
Here interns, Brendan and Rowena show us how it’s done using a template to ensure the right size notch. (Music by Money Mark)
Tools for straw bale building
Here we see our beautifully constructed straw bale walls. In front of them, two of the tools of the trade.
First up, we have the persuader. This larger than life hammer is used to knock the bales into alignment.
Secondly, we have the baling needle. This is threaded with twine and passed through the bales like a giant knitting needle in order to re-string the bales to custom sizes.
Dressing the Bales
The first thing we do to our bales is to dress them. This means we physically manipulate the straw in the end of the bale to make a flat and square end. This means our bales fit together better with fewer air gaps.