Conclusion: A complex and evolving system

2.3.1. A complex system

This chapter presented an overview of the historical coevolution of housing, ventilation technologies and social actors. The aim was not to present a comprehensive history of the subject, but to demonstrate how the social and technical aspects of ventilation cannot be separated from one another, and to analyse the context for the current challenges facing ventilation in LEH. During each historical period, multiple technological and social transitions occurred simultaneously, such as changes in heating fuel, ventilation systems, housing construction and layout, as well as evolving environmental and energy concerns. The formation of new professions meant that one person was no longer able to oversee every part of the building process. This introduced the potential for miscommunication and conflicting priorities to affect the design of ventilation systems and to hinder their ultimate performance. Regulation has also been introduced to protect people’s health and to save energy, while comfort has always played an important role in the design of new housing. Some of the social and technical aspects of domestic ventilation are illustrated in Figure 12.⁵⁶

56 This diagram is based on Geels’ idea of a socio-technical system, a cluster of interrelated social and technical elements, which will be discussed further in the next chapter (Geels, 2005, p.2). It is not intended to provide a definitive list of all aspects of a socio-technical ventilation system, but to demonstrate the potential extent of such a system’s reach.

Figure 12: Socio-technical system arrangement for UK domestic ventilation

The current socio-technical system arrangement for UK domestic ventilation is very complex.

While ventilation was historically introduced to remove pollutants generated through heating systems (e.g. coal fire smoke), it now has to balance IAQ with tightening energy efficiency requirements. Furthermore, as there are four approved systems for delivering ventilation in new homes people potentially have to understand several different ways of ventilating their home, not just one. Designers and constructors are also faced with at least four different sets of technologies choose from when specifying a system. If they do not understand the implications of their choice it is hard to make the most appropriate decision and to deliver it well. The creation of a successful new home now relies on input from a range of consultants and stakeholders and is not straightforward. It increasingly relies on technologies which were developed for non-domestic applications (e.g. heat exchangers) and were then transferred to housing.

As demonstrated in section 2.2, this complexity is a recent development, as for much of the past homes were naturally ventilated using windows, air bricks or air infiltration. Looking at historical evolution also demonstrates how individual technological innovation itself does not guarantee successful commercialisation, nor lead to changes in the way homes are ventilated; only when the infrastructure exists for it to be adopted by a wider group of users can a technological transition occur. For example, electrical appliances could not be used in homes until there was

Socio-technical

a system in place to deliver power to housing, and MVHR wasn’t an effective ventilation solution until dwellings became more airtight.

The current regulations are based on various theoretical assumptions about how different types of ventilation may work; however, there is limited evidence of actual ventilation rates in occupied homes, as this is challenging and expensive to measure.⁵⁷ Furthermore, there is uncertainty about how people interact with ventilation technologies such as windows and trickle vents (see section 3.2.3). As the social and technical are so evidently interconnected, this thesis adopts the position that to fully understand the role of ventilation in maintaining a healthy, comfortable and energy efficient environment, a socio-technical approach must be taken.⁵⁸

2.3.2. Industry is moving towards MVHR

MVHR is a complex technology which is still quite rare in today’s housing stock. It is relatively expensive to install and requires technical expertise. For example, in some instances residents have complained of excessive noise from systems which were poorly installed (Macintosh and Steemers, 2005). Nonetheless, as airtightness increases in response to the demands of ADL and SAP, it is predicted by some that MVHR will eventually become the norm in new UK housing (NHBC and ZCH, 2012). These recent development fulfil the prediction voiced in the 2005 book “Handbook of Domestic ventilation”, where the author reasons that ‘it is hard to escape the conclusion that the imposition of a prescriptive airtightness standard for dwellings would push the construction industry towards the use of the centralised mechanical ventilation systems, providing both supply and extract air and almost certainly employing heat recovery from the exhaust’ (Edwards, 2005, p.245).

However it is important to note that this move towards MVHR is based on a theoretical calculation of the energy saving potential of the system, which does not take into account the reality of systems in use. Despite the increased complexity of methods used to inform housing design and assess compliance, the assumptions remain a simplification of what is a very complex system made up of many physical components, policies, regulations and stakeholders.

To demonstrate some of this complexity, Figure 13 illustrates the wide range of social groups involved in domestic ventilation installation and use.

57 Large scale studies have focused on pressure testing unoccupied homes; for example, a study of 471 homes by the Building Research Establishment (BRE) found the average infiltration rate during pressure testing to be 13.1 ach@50pa (Stephen, 1998).

58 The term ‘socio-technical’ will be explained in more detail in the Chapter 3 and Chapter 4.

Figure 13: Social groups involved in domestic ventilation installation and use

Given the limited empirical evidence of the impact ventilation systems have on energy use there is a heavy reliance on theoretical modelling, which may oversimplify this complex problem and which depends on many invalidated assumptions. For example, based on the figures in Table 7 (p.27), ACH, and therefore heat energy consumption, would be notably greater at times when windows are open; however, as SAP assumes that windows are closed during winter in MV installations, it is unsurprising that a performance gap is often reported between predicted and actual energy consumption of homes (Janda and Topouzi, 2015).

Another reason for a potential increase in the use of MVHR is that household composition is changing as we see a rise in single person households (Palmer and Cooper, 2013), and continued urbanisation; therefore, the housing industry may evolve in response to this by providing more inner-city apartment buildings and single parent family homes. It is difficult to design a high performance, low energy, and naturally ventilated small apartment that relies

solely on NV. It seems that long term, the construction industry may be being pushed towards MVHR.⁵⁹ The next chapter reviews research to date on how people interact with the different components of domestic ventilation systems to try to understand whether ventilation practices are changing in relation to new technologies.

59 Although beyond the scope of this thesis, now may be a good time to reflect on whether this is really desirable or even appropriate.

Chapter 3: Researching ventilation practices