Building Night-Time Surveys

There have been a number of climate chamber studies that examined how people respond to highly controlled climates, with a view to determining optimal conditions for building occupancy. The nature of climate chambers means that they do not represent the conditions within a building, and consider building occupants inert subjects of their environment and unable to alter their surroundings (de Dear and Brager, 2002, Humphreys, 1995b). Occupants and buildings alter and impact upon each other to the point where a relationship is formed and this must be considered when examining thermal comfort.

Surveys were conducted to gain information across different seasons, and to allow a comparison of how the building performed in different climatic conditions. The studies occurred over the period of a year at three month seasonal intervals. Study nights were organised around the routine of the householders, to ensure that their regular activities were not overly disrupted and that all participants could be present. Each study involved a start time of as close to 6pm as possible and ended when the householders indicated that they wished to retire to bed. While there was some variation between cases, each case was subject two four night time studies. Each night time study involved the gathering of physical information (including air and surface temperature data), the observation of occupant interations with the thermal environment, and the surveying of the occupants on their

A LogTag TRIX-8 Temperature Recorder was placed in an undercover and sheltered position outside the building to record temperatures at 15 minute intervals throughout the evening. This outside logger was placed to allow a comparison of indoor and outdoor temperatures.

5.7.1. Adaptive thermal comfort surveying

Chapter 4 examined the range of previous studies of thermal comfort that have been undertaken, and the techniques available for thermal comfort surveying. These studies were instrumental in the development of a thermal comfort surveying system suitable for this study. A thermal comfort analysis method and accompanying form was developed to assess occupants at regular intervals. This form drew from information in Appendix E of the ASHRAE Standard 55-2004: Thermal Comfort Standards for Human Occupancy (ASHRAE, 2004), as well as a previous studies into adaptive analysis of thermal comfort, such as Baker and Standeven (1996), Boestra (2005), de Dear and Brager (2002), de Dear et al. (1998), Humphreys (1995b), Nicol and Pagliano (2007), Olesen and Brager (2004), Rowe (1995) and Van Der Linden (2006).

Baker and Standeven (1996) developed adaptive comfort criteria that were suitable for free running buildings and those not controlled by automated HVAC systems, where conditions such as temperature are subject to greater variance. Nicol and Pagliano (2007) and Baker and Standeven (1996) examined how conventional thermal comfort modelling is inappropriate for buildings with the environmental change of a free running building, and developed criteria that should be considered when using an adaptive approach to thermal comfort analysis. In doing so, comfort monitoring surveys were undertaken that provided thermal information room by room, and made subjective surveys of occupants.

Boestra et al. (2005) and Van Der Linden et al. (2006) assessed and simplified methods of thermal comfort analysis for design, and developed a new thermal comfort guideline suitable for the Netherlands. This included the formulation of new methods to predict and analyse building thermal comfort within an adaptive framework, examining degrees of occupant control and levels of adaptation by occupants.

In examining thermal comfort in naturally ventilated buildings, de Dear and Brager (2002) compiled a wide range of raw data from existing field studies in 160 buildings in a range of climatic zones. Their work examined the potential energy savings of incorporating the

Research by Olesen and Brager (2004) details the new ASHRAE Standard 55 for predicting thermal comfort, including specification of conditions acceptable to a majority of a group of occupants in the same space. Olesen and Brager (2004) focused on moderate indoor temperatures, similar to those of this study, and determined that the personal factors of clothing, insulation, metabolism, and physical activity levels, greatly influenced the body‟s heat exchange and subsequent thermal comfort analysis.

The form developed to gather data for this survey contained questions aimed at the occupants, as well as a list of observations for the surveyor to make regarding each occupant. Work by Humphreys (1995b) and Rowe (1995) into the adaptive analysis and prediction of thermal comfort greatly informed both the development and delivery of this form, including the appropriate choice of questions and observations required. This form is contained in Appendix 3.

Occupants were surveyed at 30 minute intervals regarding their level of thermal comfort. They were asked to rate their thermal comfort on a scale of -3 to +3, as defined in the ASHRAE (2004) and ISO (2005) standards, and details were entered onto the thermal comfort analysis form. The rating system was explained to occupants prior to beginning each survey, to ensure accurate response and minimise the need to interfere or interact with participants throughout the course of each survey period.

-3 -2 -1 0 +1 +2 +3

very

cold cold slightly cool neutral slightly warm hot very hot

Kearns (2005) considers visual observations to be a key tool in many types of research and that observations should not be regarded as a haphazard or random research tool. Rodway (1994) notes that observation “involves touching, smelling and hearing the environment and making implicit or explicit comparisons with previous experience”. In observing a phenomena or situation, one must have a vantage from which the observations are made, which in these case studies are that of an outsider (Kearns, 2005).

Kearns (2005) divide observations into three distinct types based on purpose:

 counting – where observation has an enumerative purpose;

 complementing – where additional descriptive evidence is gathered to support existing data gathered by formal methods; and

 contextualising – where in-depth interpretation of a phenomenon is achieved.

The observations made predominantly involved the first two of these study types. Observational data were gathered to complement data made from surveys and obtained by the data loggers and building measurements. Likewise, each series of observations was taken to help understand the thermal processes at a specific time and place for each case study. Observations were made regarding actions or conditions that would impact on thermal comfort levels. Previous work by Humphreys (1995b), Rowe (1995) and Humphreys and Nicol (1998) has indicated that predictions and analyses of thermal comfort can be made by observing clothing choices, activity levels, and other adaptive mechanisms employed by subjects.

Occupant clothing levels were recorded to allow a clo rating to be assigned to each, and changes in clothing levels were recorded. Clo values are a measure of the intrinsic thermal insulation of a subject, and factor in both clothing and furniture. De Dear et al. (1998) and Yigit (1999) examined the insulating value of clothing, identify adjustments in clothing as an indicator of behavioural adaptation and determined that clo values are a good indicator of occupant behavioural adaptation to thermal environment. De Dear et al. (1998) recorded a decrease of 0.1 clo units is expected for every temperature increase of 2°C in indoor mean temperature, while studies by Fanger (Fanger, 1972) indicated a change of over 0.2 clo units per increase of 2°C in indoor mean temperature.

The effects of metabolism and physical activity on thermal comfort have been documented. Rowe (1995) identified that as physical activity increases, occupants will favour a lower temperature. Occupant activity level was also recorded, on a scale ranging from reclining

through to high activity, and notes were made regarding any activities that may have influenced thermal comfort levels, such as eating, drinking, opening or closing windows, movements into cooler or warmer areas, and adjusting thermostats. This information facilitated a quantification of data by allowing an estimation of metabolic rate (met). De Dear et al. (1998) identify metabolic rate as a behavioral parameter that should be investigated because of its relationship with indoor temperature in both air conditioned and naturally ventilated buildings.

comfort. Chamra et al. (2002) examined thermal comfort at sedentary and moderate activity levels, and determined that temperature is seven times more important than relative humidity in thermal comfort sensation in males, and nine times more important in females.

Air temperature and humidity readings were taken in the centre of each room, with multiple recording locations in larger rooms or open plan areas. These recordings were taken at 15 minute intervals, to allow profiles to be developed for each room, and comparison with thermal comfort surveys.

Chamra et al. (2002), Parsons (1995) and Rowe (1995) determine that air velocity and resultant drafts have a profound impact on thermal comfort levels in offsetting increases in temperature and in reducing comfort in colder temperatures. The ASHRAE (2004) and ISO (2005) standards both include draft in identifying and predicting thermally comfortable environments. Where air movements or drafts were noticeable or identified by the subjects as a cause of thermal discomfort, mean indoor air speed analysis was undertaken to determine the magnitude of those movements. De Dear et al. (1998) has previously used the measurement of mean indoor air speeds simultaneous to thermal comfort questionnaires as an indication of occupant‟s behavioural adjustment to indoor temperatures. De Dear (1998) indicated that building occupants are likely to create higher air speeds as a means to adapt to increases in temperatures, and that this is more likely to occur in naturally ventilated buildings and is much less common an adjustment technique in air conditioned buildings. All spot measurements of temperature, humidity and wind speed were taken with a Kestrel 3000 Pocket Weather Meter. This device measures air movements of 0.4-40.0ms-1_{, temperatures of}

-45°C to 125°C, and relative humidity of 0% to 100% with negligible calibration drift.

5.7.3. Surface Temperatures

Olesen and Brager (2004) determined that radiant temperature is an important factor in assessing thermal comfort. Radiant temperatures of the internal surfaces of the building were taken, including the walls, ceiling and floors of all rooms. These measurements were taken to allow an analysis of the thermal storage properties of the building and to assess the impact of surrounding surfaces on the thermal comfort of building occupants. Proximity to surfaces with temperatures that are particularly different to body temperature or room temperature can impact on thermal comfort levels. An example of this is the stuffiness experienced by individuals in a warm room, but who are in close proximity to a cold surface.

Surface temperatures were taken using a Raytek infrared thermometer. It featured an infra- red pointer to allow accurate readings of the same specific point on each wall, ceiling or floor space.