On my Just Two Things newsletter last week I discussed a post by Jeremy Williams, at the Earthbound Report that critiqued the failure of the Insulate Britain campaign of direction that was intended as a demand for an home insulation programme in Britain.

The campaign had announced its failure and its closure.

Williams is an environmental activist and commentator, and he’s certainly not opposed in principle to non-violent direct action in support of environmental ends. But he was critical of Insulate Britain.

Disconnected targets

In short: the campaign’s actions—mostly disrupting roads—were completely disconnected from its targets. Indeed, he suggested the sorts of things they ought to have been doing instead:

We know that Taylor Wimpey, for example, successfully lobbied against plans for zero carbon homes. Imagine that their building sites came grinding to a halt, costing them thousands in lost work days. They would call for arrests, but behind the scences they might also think again about insulation. The general public would understand the connection – if they heard about it. But even if they didn’t, the signal would get through to the decision makers.


My reflection on this was that home insulation was the sort of campaign that might not need direct action to achieve its goals:

[I]t has a lot of winners, especially as fuel bills go through the roof. Insulation—as we’ve known ever since the Green New Deal did the sums way back when—spreads employment around the UK, puts people into work in localities all over the UK, and even supports the so-called ‘levelling up’ agenda, or would if it was a programme instead of a slogan… The House of Commons Business Energy and Industry Strategy Committee recommended it to the government in 2019.

Well, maybe not so fast. Robyn Pender, who is a buildings scientist, sent me an email to say that the worst thing about the Insulate Britain campaign was that they had fallen for the insulation industry’s propaganda. And to be honest, given my discussion of the issue, it sounds as if I had as well.

Retrofit isn’t working

She also attached an article she’d had published last year in The Journal of Architectural Conservation—behind an academic publisher’s paywall unless you have academic access—which explained why this is the case. In short: the retrofit model isn’t working, and the whole problems needs re-framing. We need to be thinking about ‘thermal comfort’ instead of insulation.

We have now had rather more than two decades of retrofit programmes aiming to reduce energy and carbon in the built environment worldwide, and the kindest thing that can be said is that the results have been disappointing. At best many retrofits have failed to achieve meaningful reductions, and at worst they have led to serious problems for the building and its occupants.


This is down to the way we changed building design when fossil fuels suddenly became available to us—broadly from what she calls a ‘traditional’ solid wall design to a ‘modern’ hollow wall.

Currently, buildings are mostly constructed with carbon-intensive (and often short-lifespan) materials that are expensive to produce and transport, using systems that make maintenance difficult, if not impossible. Many of the resulting buildings are not usable without mechanical services… Designs are usually highly specific to particular tasks, and can therefore be very difficult to adapt to changes of use.

The article also includes a pair of system diagrams that try to show the lifetime flow of materials and maintenance in a building. This is the carbon-intensive version. There’s a lot of complexity here—and a lot of transport:

Diagram and photo: Robyn Pender.

Ends and means

The outcome of this is a very short building lifespan. I’ll come back to what ‘thermal comfort’ is, but in her article, Pender argues that we’re approaching this whole problem in a way that means that we won’t be able to solve it.

Current approaches to retrofitting represent a classic case where the means chosen to meet an end conflict with the desired outcome; as described by Brian Christian in his book The Alignment Problem: Machine Learning and Human Values. (A)lignment problems are common in modelling of the built environment. This is especially true of the models that are being employed to predict energy use or the impact of retrofits. The factors involved in energy consumption are poorly understood, leading to poor predictions, especially in buildings of traditional construction… Therefore the actions suggested by retrofit modelling rarely deliver the promised energy savings.

There is a whole set of issues with the current approach to retrofit. These include:

  • Difficulties in assessing carbon and energy
  • Poor understanding of how building systems and materials behave in situ
  • Poor integration of modern mechanical systems into buildings
  • Poor understanding of retrofit materials
  • Reliance on market-led retrofit solutions.

These are effectively all issues to do with an approach that’s designed to adapt a building designed for a fossil fuel powered world to work in a low carbon world.

Low carbon building

But the deeper problem is about the twin issues of ‘thermal comfort’ and also understanding what people did when they were building for a pre-industrial revolution low carbon environment. The current ‘insulation’ model starts from the wrong place:

(It presumes) that for a building to be comfortable and usable, it requires some form of space heating or cooling. If this were indeed the case, saving energy and carbon would require action to prevent conditioned air being lost. Essentially, the building envelope would need to be sealed. In reality, thermal comfort is dominated by other factors, including occupant control. The critical importance of radiant body heat loss was well understood in the past, and dealt with using radiant breaks (simple passive interventions such as cloths hung on the wall and made into partitions and canopies, or wooden panelling, which stop body heat being absorbed by the building fabric).

Lost knowledge

At the same time as we’ve lost this knowledge about thermal comfort, we have also lost an understanding of many of the features that used to be incorporated into older buildings to keep them warm, which is one of the reasons we think of old buildings as cold and damp:

(M)any vernacular buildings are poorly understood, poorly maintained, and poorly operated. With the purpose of weathering details such as lime renders, hood mouldings and cills no longer understood, when these eroded, they were removed rather than being repaired or replaced. Most older buildings are now missing at least some of the features that once kept them in good condition, and ensured dry and comfortable interiors… When the lost features are reinstated, occupants are commonly struck by how much warmer, as well as drier, the building now feels to them.

Care and repairability

Because materials were both difficult and expensive to transport, older buildings were constructed with an emphasis on care and repairability. In contrast, in the fossil age, there is “an emphasis on construction rather than care: indeed, the resulting buildings are often very hard to maintain, which is one of the factors encouraging short lifespans.” In turn, this increases their emissions impact, since demolition is energy intensive and few materials are reused.

This is summarised visually in the other diagram in the article. In the pre-fossil fuel version, there is less of everything:

(Diagram and photo: Robyn Pender).

As she explains in the article, one of the benefits from this was that

there was extensive local knowledge around the best way of designing and maintaining the building. Complete demolition was rare, but all materials were reused (often as part of the replacement building).’

In 2050

So what does the post-carbon world of 2050 look like? In some ways, it looks back as much as it looks forwards:

(B)uildings (are) intrinsically part of their local environment, and operated by knowledgeable occupants. It would however incorporate piped water and some form of electricity supply, albeit much more effectively than at present, and it would put no emphasis on cars, electric or otherwise. It would not have air conditioning, and perhaps not space heating either, but the buil’dings would be more healthy and comfortable than at present – noting that ideas of comfort evolve, and in the fallout from the pandemic are likely to once again include significant ventilation, as was always sought after in the past.

In futures terms, this is an example of something from the past that has been submerged in the present, and is now re-emerging to shape the future. I think I’d like to understand more about what the ‘thermal comfort’ approach looks like at scale. as a strategy for the 26 million or so UK homes that need to be brought up to standard for a net-zero world. But that can be a conversation for another time.


A version of this article is also published on my Just Two Things Newsletter.