Climate action: Comfort is a crucial missing piece of the puzzle

The cloths hanging on the wall behind the Virgin in Fra Angelico’s Annunciation were not merely decorative, nor were they there to indicate her importance: to the medieval eye they showed she was quiet and studious. (La Anunciación by Fra Angelico from Prado in Google Earth).

1 Introduction
2 The background
3 Learning from the past
4 References
5 Related articles on Designing Buildings Conservation.

Introduction

As we struggle to reduce our use of energy and carbon, discussions have become fixated on technical solutions. But what faces us is not precisely a technical problem; rather it is the outcome of a loss of knowledge in the global north as we began the industrial exploitation of fossil fuels. It is in the history of constructing and operating buildings that we can find the reasons for the current crisis and the answers for how to respond to the crisis rapidly and effectively.

The background

The changes in the built environment enabled by the sudden availability of an apparently limitless supply of cheap energy were accelerated by the rise of manufacturing marketing and urbanisation. Building became an increasingly business-driven field with professions that were increasingly siloed. When failures arose in design or operation, the response was not to learn from those mistakes, but instead to throw more fossil fuels at the problem. After 250 years of profligacy, surrounded by over-glazed buildings with deep floor plates that require energy-hungry services, we are now reaping the results of what we sowed.

Graphs of energy consumption show a massive increase since the 1960s, accelerating sharply over the past few decades: an increase that has not yet levelled off, let alone reversed, despite all our efforts towards ‘energy efficiency’.

Faced with these shocking facts, the response has all too often been to blame ‘traditional’ solid-wall construction, even though the older buildings were functioning well before the sharp increase in energy use began. Part of this is certainly due to corporate greenwashing: ‘insulate Britain’ is a fine mantra for global manufacturers wishing to open markets currently closed to them. Much has been written about the problems of ‘fabric-first’ interventions on traditional buildings, but I think it is more than time we take a good hard look at the fundamental reason we think of insulating in the first place.

It is the use of air temperature as a proxy for occupant comfort and health, and therefore the usability of buildings.

The greatest proportion of energy used within buildings of the global north, and the increase in that use, is attributable to heating and cooling the air (that is, space-conditioning – cf GlobalABC.org). As thermal physiologist Hannah Pallubinsky [1] and her colleagues note, since the 1970s professional associations dealing with the servicing of the built environment (not least the influential American Society for Heating, Refrigerating and Air Conditioning Engineers, ASHRAE) have developed ever more demanding ‘comfort’ standards, all based on controlling air temperature. These are widely recognised to be based on deeply flawed research; nonetheless, they have made their way into many building recommendations and regulations.

Thermometers are a product of the Industrial Revolution and the Enlightenment. Although they made assessment of air temperature easy, the inappropriateness of this as a measure of health and comfort was being called out by physiologists from the earliest days. Leonard Hill, head of the Medical Research Committee, wrote in 1915: ‘For the purposes of controlling the heating and ventilation of rooms the thermometer has… acquired an authority which it does not deserve… It affords no measure of the rate of cooling of the human body, and is, therefore, a very indifferent instrument for indicating atmospheric conditions which are comfortable and healthy to man.’

Regardless, outside medicine, air temperature as a proxy measurement for thermal comfort took hold and was soon accepted as a paradigm. This may be because of the fashion for enumeration: ‘comfort’ is impossible to describe with a number.

To properly understand comfort, we first need to discard the common belief that humans are passive objects whose health depends on heat absorbed from the environment. We take in energy in the form of food and oxygen and our body transforms that into heat, to support our metabolic processes and keep the vital organs functioning optimally. If these organs are not to die, the temperature of our ‘core’ must stay within a very tight range (36.5 to 37.5°C). This means that even in the coldest conditions we always need to lose some of the heat we are generating into our surroundings, especially when we are active. Typical recommendations for indoor air condition assume that occupants require a ‘neutral thermal environment’ (where body heat is not lost into the surroundings), but this is simply not true. To stay happy and healthy occupants will need to lose different amounts of heat according to how active they are, what they are wearing and their own personal preferences. There is no such thing as ‘ideal’ interior conditions.

Some of our heat is lost through touch depending on what we touch, how we touch it and the surface area of contact. Between two and 22 per cent is via transfer into the air, mostly by perspiration and evaporation. The rest is due to our bodies radiating heat out into our surroundings. This accounts for at least 60–65 per cent but can be as much as 85 per cent if we are lightly dressed and if our surroundings strongly absorb radiant energy. This is far more than could ever be lost into the air directly, whatever its temperature (air movement and humidity are more important).

To maintain our core at the right temperature, we have evolved a highly complex thermoregulatory system which includes some familiar reactions.

When we need to lose more heat, the blood is sent into the skin to increase radiation, our sweat glands are activated to increase evaporation and we may start to pant (losing heat by evaporation from the lungs). Metabolism slows, so we feel less need to eat and other behavioural changes are triggered (such as adopting a spread body position to maximise both radiative and evaporative loss).

When we need to slow heat loss, the blood is drawn back from the skin and limbs; eventually, we start shivering and get goosebumps. Our body position draws in and our metabolism is sped up to match heat being lost, increasing our appetite, especially for food such as carbohydrates that can rapidly be transformed into energy.

In all this, air temperature is conspicuous by its absence as a critical factor. Thermal physiology therefore explains the experiences of many during lockdown, when we were all forced to look into the complicated ways our own homes worked.

The thermostat rarely turned out to be a useful guide. Cold surfaces such as bare floors or walls, or large areas of glass, persistently absorb our radiating heat, making us feel cold even when the air temperature is high. In winter, the heating might be set to 22°C, but if there is an unpleasant draught (perhaps because the wind is in a particular direction, or because a door has been left slightly ajar), you would still feel very uncomfortable. As the low winter sun enters the room through the windows and hits us directly or heats the surfaces around us, we instantly feel hot even in the coldest air temperatures. It also depends on how we are using the space: one person sitting quietly reading the newspaper may feel too cold, but another busy with the housework may feel much too hot. In summer, heat-absorbing surfaces help occupants cool down, and nasty draughts become pleasant breezes.

Learning from the past

As we realise the importance of radiant loss of body heat, it makes sense of what we see in illustrations of interiors predating the Industrial Revolution. In winter a ubiquitous feature was walls covered with drapery, cloths used to partition spaces, rugs on the floor, and canopies of cloth and wood, as well as barrel-vaulted ceilings and wooden panelling. Unlike stone, brick or mortar, cloth and wood warm almost instantly as we radiate into them, after which they stop absorbing our heat. A cloth between an occupant and a stone wall acts as a radiant break, slashing the huge amount of body heat we would otherwise be losing into the massive wall. The effect this has on comfort is easy to feel – simply drawing a light net curtain across a glazed window in winter produces an instant improvement – but it is extremely difficult to measure. Certainly radiant breaks will have little effect on the temperature of the air.

Medieval images show how cloth and timber created ‘cosy corners’ for scholars and others sitting quietly. Paintings of festivities show canopies and tents over the musicians and cloths draped behind honoured guests, while dancers benefit from the cool bare floors and walls. We know from housekeeping records that cloths were often taken down in summer when radiant heat into solid walls was beneficial, and so it is not surprising that so many wall paintings are fictive draperies.

Fireplaces in use are invariably shown associated with cooking, although there can be little doubt that the warm glow and crackle of a fire was at least as comforting then is it is to us now. When not being used for cooking, fireplaces are often shown sealed with wooden panels. But although they used screens and drapes to control ventilation, they did not try to eliminate it. Indeed, it is clear from books that air movement and air exchange was desirable, for health reasons as well as comfort:

‘But Lark Rise must not be thought of as a slum set down in the country. The inhabitants lived an open-air life; the cottages were kept clean by much scrubbing with soap and water, and doors and windows stood wide open when the weather permitted. When the wind cut across the flat land to the east, or came roaring down from the north, doors and windows had to be closed; but then, as the hamlet people said, they got more than enough fresh air through the keyhole.’

Flora Thompson, Lark Rise

Now, in contrast, we attempt to achieve comfort by heating and cooling the air, sealing and super-insulating our building envelopes to prevent this air from being lost, resulting in serious problems of mould and bad indoor air quality.

Comments such as Flora Thompson’s and medieval images are often interpreted as showing our ancestors were much hardier than us. But there is more going on, if we go back to thermal physiology.

For a start, appropriate clothing, draperies and rugs and so on were able to relieve so much of the thermal discomfort that the temperature of the incoming air was largely irrelevant.

Secondly (as highlighted in the paper by Pallubinsky and others, and confirmed by many other studies) our thermoregulatory systems become moribund if not exercised. This not only makes us prey to health problems such as heart disease, obesity and diabetes, but also increasingly unable to respond quickly and effectively to changes in the environment. In other words, the more we live and work in tightly controlled thermal conditions, the more apt we are to feel uncomfortable; or worse, to suffer serious health problems from exposure to very hot or very cold conditions. With climate change already leading to extreme weather events, the global north penchant for constructing buildings that require heating and air conditioning begins to look even more unwise.

As fuel prices increased, the sales of personal comfort items such as heated blankets exploded, but they have not slowed despite the cost of central heating dropping again; indeed, their popularity has increased as people have discovered just how good they are for dealing with discomfort quickly and effectively. In hot climates, the ceiling fan is similarly enjoying an overdue renaissance.

This is the realm of ‘thermal delight’ first described by Lisa Heschong (in Thermal Delight in Architecture, MIT Press, 1979). Humans are much more sensitive to change than to absolute conditions, so, for example, leaving hallways cold enhances the pleasure felt when entering a cosy lounge. The psychological aspects of comfort may make us uneasy in our very deterministic global north world, where we trust more to instrumentation than to our own senses. But this is a blind spot. If we can overcome our need to enumerate, we will have many more tools at our disposal for slashing the energy and carbon we are using to try to make our buildings comfortable.

One final concern about our current focus on air temperature and space conditioning is based on the impact this has on the building and its occupants. It is well known that heated air rising is apt to create uncomfortable draughts; but more subtly, since the primary way we feel cold is via radiation loss into the surrounding surfaces, the warm heating is being used to try to raise the temperatures of those surfaces. Setting aside the discredited notion that a ‘neutral thermal environment’ is actually desirable, heating surfaces with moving air is extremely inefficient, especially if there are any sources of damp (the resulting evaporation will cool the wall). It is therefore little wonder that we in the global north currently use so much energy to provide building comfort but still meet with very debatable success.

The complex background to comfort fits well with the evidence of field researchers such as Freya Wise [2] who have had little trouble demonstrating that when older buildings are maintained and operated by people who understand them, they use very little heating or cooling energy. And this is despite many alterations: post-industrial fashions led not only to the loss of the draperies, but also to the removal of ceilings to reveal roof timbers, of partitions and even of the renders that kept the buildings dry. All of these features have the potential to make the buildings more comfortable while using even less energy and carbon. Conservation experts may be the only professionals who speak with building owners and occupants on the subject of climate change without having a product to sell. We have many important messages with which to support them, not least how reinstating lost furnishings could quickly and cheaply make their buildings comfortable using little or no energy and carbon, and at the same time greatly benefit their health and wellbeing.

Given the seriousness of the climate emergency, many conservation officers in local government and the statutory heritage authorities are thinking of allowing more changes to historic buildings, but I do not believe we should be focusing on risky fabric-first interventions of dubious longevity and utility such as solid wall insulation. Is it time, though, to encourage reinstating the passive features that were lost when we began to throw fossil fuels at every problem? Replacement of lost renders, ceilings, sash windows and awnings would all be high on my list. Even when there is no record of the building having had these features originally, if some or all of them will make the building more comfortable and therefore more useable now and into the much hotter future, should we not be encouraging owners and occupiers to consider them?