Context 164 - May 2020

C O N T E X T 1 6 4 : M A Y 2 0 2 0 17 The war on damp A medieval merchant’s house in Southampton, from when ideas about space heating were very different (Image: Geni, Wikimedia) could be found in all types of building, from the smallest London tavern to Hatfield House. In other countries they used leather panels or carpets, and timber panelling was popular everywhere. Radiant breaks were supplemented by well-designed clothing and furniture, coupled with local elements such as hand warmers and hot bricks, or fans in hot weather. Drapery seems to have begun to be unpopular in the 18th century, perhaps because of the plague – ‘hangings’ were identified as a possible source of infection – but their absence must have made Georgian buildings very cold, particularly after the introduction of Rumford grates made them very draughty. It is perhaps not surprising that Victorian interiors are famed for drapes and curtains. Their primary purpose forgotten, these once again disappeared with the rise of modernism, and today fashionable interiors are still characterised by large areas of hard surfaces. If air heating is to deal with this source of discomfort, the air must be kept warm enough for long enough that it can warm the wall surfaces by conduction, until they are as warm as the occupants. It is easy to see why this is so costly. Services engineers often express surprise that underfloor heating is popular for tall spaces with large areas of floor, because it can not raise the air temperature to ‘desirable’ levels; it works by preventing body heat being lost into the floor. Topping up with perimeter radiators may not be necessary: indeed, if that increases draughtiness, it may be counterproductive. With this knowledge, we can look with new eyes at the rebound effect. If the occupants believe that the heating or cooling system they have bought will deliver them perfect comfort, but it does not, they will attempt to run it ‘harder’. If that makes things more damp or draughty, the result will be a vicious cycle. Reinstating radiant breaks is clearly desirable, and this need not look old-fashioned: it may be a simple matter of using cloth rather than wallpaper. Today we also have the advantage of a wide range of tools for heating and cooling people that can be run on decarbonised electric- ity: radiant heaters, heated carpets and electric fans. Moreover, if comfort can be dealt with using little or no space heating or cooling, there is no need for expensive and risky attempts to seal buildings. Reaching for net zero becomes infinitely easier at a stroke. Many other elements of traditional technology are just as useful as they ever were. To give the obvious example: the vertically sliding sash window has never been bettered as a means of ventilation, with openings at top and bottom for precise control over air exchange. Tools such as these have another advantage: people have been shown to be much more comfortable if they have control over their environment, even if they then choose not to exercise it. How do we convince regulators, advisors and the general public to question current assumptions around retrofit? We will surely need to find some way of assessing what in the past was ‘common sense’. Regulators will wish to quantify change, and air temperature is easy to measure; but comfort has so many nuances that its measurement is very complicated. Methods for robust assessment of benefit is a research vital area, and Historic England has a number of investigations under way. We will be reporting on these as results become available. We will also be interested in your thoughts about how to reach building owners and users. If you would like to read more about the his- tory of comfort, Historic England has published Learning from History , Sarah Khan’s exciting report on research for her masters in conserva- tion at the Architecture Association.1 1 Khan, S (2020) Learning from History: traditional low-energy approaches to comfort , research report for Historic England (forthcoming) Robyn Pender is senior architectural conservator at Historic England. With Brian Ridout and Tobit Curteis she edited the Building Environment volume of Historic England’s Practical Building Conservation series.