Let’s hear it for pebbledash as we dash to insulate our homes
Pebbledash and other forms of roughcast render are one of the mix of methods we need
Keir Starmer regularly trots out the line that he grew up in a ‘pebbledash semi’ - and then the assembled Labour members laugh as if this is the epitome of bad taste - the avocado bathroom suite of building. A composite video of shadow cabinet ministers repeating this mantra and grinning was circulating on social media last week.
Pebbledash it is actually a variant of what we call in Scotland harling and it is used on castles and stately homes as well as humbler dwellings here, because it provides effective protection against the powerful winds and salt-tanged rain of the northern coasts.
The pebbly version was introduced by the Arts and Crafts movement as part of an effort to reinvigorate traditional building methods. But in the late 20th century, builders moved to using cement instead of lime in it. That was a disaster because it makes the material hard and inflexible and it can even crack the stone or brick underneath - so that was where its bad rep began. But used with lime mortar, it is breathable and very long-lasting. It can also be used to cover exterior-wall insulation.
While Starmer’s childhood reminscence may be intended to be affectionate, I think this constant repetition risks giving roughcast covering a bad name. That matters because this is part of the mix of methods we need to insulate our homes.
Insulation is one of the last relatively low-hanging fruit available that we have on the tree of reducing carbon emissions. It is also one that everyone from across the political spectrum should surely be able to agree on. It is - with a small c - conservative, about reducing waste and saving money. It is also a necessary precondition to moving away from fossil fuel heating systems, because heat pumps don’t produce enough heat to work in anything but a very well-insulated home.
But in fact the UK Conservative government has shelved its targets on this and the Labour laughter about pebbledash could also sound a bit hollow to people angered by the party’s drastic scaling back of its plans to insulate millions of homes by 2030, if it wins power at the next general election.
Scotland (and the rest of the UK) have a mountain to climb in terms of home insulation
In Scotland, we have a separate public Energy Performance Register, and being a nebbie quine I like to take a look at what my neighbours have or haven’t achieved in terms of energy conservation. I am quite good at guessing - it is easy really because most older houses are awful, D to F. We have a massive problem.
The Heat in Buildings Bill (Scotland) which is in progress in Holyrood at the moment, is likely to impose new obligations on landlords and homeowners to improve their EPCs to C or above within a few years. The proposal is that if you sell a home with a lower EPC. the buyer will have to undertake to improve it, which could affect the price.
The ending of the Bute House Agreement could mean the timing of some of these targets shifts, but in general, householders and landlords in Scotland are aware of the need to start moving the dial on this.
Exterior or interior insulation both have pros and cons. Interior insulation can reduce the space in your rooms and involve losing traditional features like cornicing. Exterior insulation can be difficult in city dwellings that are close together - it is probably most suitable for detached houses. We are considering it for our wee cottage in the Highlands.
Exterior insulation is a traditional solution
Exterior insulation can be incredibly effective and is nothing new. I visited a dig at the weekend and chatted to an archaeologist who said that he had been inside a stone dwelling covered with turf and that it stayed at an even temperature and was incredibly thermally-efficient.
Some protest that externally-insulating buildings means damaging the appearance of the exterior. Personally, I don’t like brick buildings. I find the repetitive squares unappealing and I would much prefer them all to be covered with thermal insulation and harling, which can be coloured or plain and “produces a surface more curious or agreeable to the eye, than the rude materials concealed behind it.”(1).
When it comes to stone, I am not advocating that we exterior insulate Edinburgh’s Georgian New Town. But many rural dwellings are not built with top-quality stone anyway. They are generally painted and in the past they would often have been harled.
Exterior insulation means the stone on the interior can be exposed and stays warm
Another plus is that if you have exterior insulation, you can expose the stone on the interior without losing warmth. We removed 1970s boxing and exposed the stone in our wee kitchen-diner - making the main room a foot bigger all round. But we haven’t yet insulated the outside and soon after the woodburner dies down on a windy night, the place is freezing.
But if insulated on the outside, the wall then becomes a heat store, and stays warm, like a big stone you might heat in the embers of a campfire and then wrap in a blanket to take to your tent on a chilly evening.
Innovation in materials for exterior insulation
Clearly, it would be impractical to return to using turf for exterior insulation, however effective it is. The most common method today is to put on a layer of expanding polystyrene covered with render.
One downside of this is that these insulation boards are made from plastic - which is really the flipside of reliance on fossil fuels. Some builders near us in the Highlands failed to tie down sheets of Kingspan recently and it blew loose in spring storms - twice - and went birling along the coast for miles. Very soon much of it broke into tiny bits and, despite the dedicated efforts of local volunteers, some ended up in the sea, where plastic is due to outweigh fish by 2050.
Can we use traditional materials in new and innovative ways? Sheep’s wool is sustainable, locally produced, has great thermal properties - and is naturally fire resistant. It is good to see that some businesses are turning this into exterior and interior insulation material. (I am going to write more about wool next week.) There is a lot of innovation going on in this space generally. Thermal plaster made from natural materials that can be used on exterior walls is available and other materials include mineral wool and hemp or wood fibre.
When you are trying to foster change, start with where people are
The Scottish Government has come in for criticism for being too metro-centric - and whether fairly or unfairly, the Scottish Greens are getting the blame for this. Banning wood burners in all new homes, for example, has gone down badly with rural communities, for whom this is a way of life.
Most of rural Scotland doesn’t have access to the gas network and using electricity to heat your home is extortionate. When energy bills soared, many a Highlander - or Borderer- switched off the central heating and turned to buying bark ends from the sawmill, or collecting fallen trees and cutting them up. And that can be a sustainable heating method - particularly in a well-insulated house in a forest. The fire is a cheery sight on a chilly evening too - and a place to dry your boots when you get caught in a shower of rain.
Work with what we have
Understanding where people are and what can make the change seem attractive to them is important for achieving buy-in. That’s one reason for using traditional methods, and building on the past.
Perhaps the Labour Party could spend less time laughing at pebbledash and more looking at ways to encourage and support exterior - and interior - insulation of the UK’s millions of draughty homes.
JC Loudon, Encyclopaedia of Cottage, Farm and Villa Architecture, 1833.