Recomendaciones

The second major further development in thermal comfort research has been de-veloped in the seventies and eighties of the former century. This development con-centrates on an exag-gerated derivation of the heat exchange method. Similar to the heat balance model does this approach focus on heat balances of humans in relation to their environment, but is exaggerated by cognition of humans tolerating a more widen indoor temperature range in especially naturally ventilated spaces. Thus, this approach bases essentially on the opportunity to self-control openings for natural ventilation.

Humphrey and Nicol 1998 explained “This approach is based on the biological insight that the human being is a comfort-seeking animal who will, given the opportunity, interact with the environment in ways that secure comfort.”

In this discussion it is inevitable to remark that the PMV model is perfect for mecha-nically ventilated buildings like office buildings. On the contrary, PMV calculations are solely partly correct for naturally ventilated buildings. According the approach, occupants of naturally ventilated zones tolerate a spread range of operative tempera-ture, that is closer to the external environmental thermal situation and its dynamic changes (Fig. 2.14). Along this, also climate change is a long lasting slightly perceptible adaptation to the current situation and midterm future. Figure 2.14 schematically illustrates the different scientific approaches and related standards.

FIGURE 2.14 Distinction between the major different approaches to determine indoor thermal comfort

Since space occupants of naturally ventilated spaces are principally willing to largely adapt to climate circumstances, the approach is called the ´adaptive comfort model´.

Research focuses on human´s reaction to adapt to extreme climatic differences. Indivi-duals are seen as independent participants of an dynamic environment who not at all simply react on stimuli but try to change the environment or their range of parameters (activity, clothing, controls, etc.) in order to proactively to improve thermal situation.

Substantially, this attitude towards the environment implies a human intelligence (Humphreys, 1978) like decision making skills and an experience feeding cognition of climate and weather conditions of the past and the near future as well. Both have influence on our physical and psychological perception of thermal situations and con-trol adaption to it according our preferred thermal status as Bluyssen explains (2009).

The ASHRAE standard firstly bases on the heat exchange model and was later on reworked to include the adaptive comfort algorithm.

In this context, Humphrey initiated two central but slightly different key parameter : the comfort temperature T_com, also known as neutral operative temperature and plotting a bandwith by upper and lower limits, and the optimum operational temperature T_o,op.

49 Literature survey and empirical evaluation of thermal comfort in sun spaces

Humphreys initiated :

Tcom = a*T_out + b [°C] (08) where :

T_com = comfort temperature (neutral operative) [°C];

T_o,op = optimum operational temperature [°C];

T_out = outside temperature index [°C];

a, b = constants

The optimum operational temperature for naturally ventilated zones in relation to the external dry bulb temperature is defined :

T_o,op = 0.31 Ta,out + 17.8 [°C] (09) Application of the ±0.5 and ±0.85 PMV criteria to a specific buildings thermal sensa-tion a 90%- and 80%- range of acceptable operative temperature reveals for each of an investigated building and its unique location.

Necessary premises for a ´adaptive comfort model´ application are :

• a naturally ventilated building / space

• occupants essentially regulate comfort via openable windows

• spaces may have a heating system (if applied, model is not useful)

• spaces can have a mechanical cooling system, but it needs to be out of run

• spaces can have a mechanical ventilation system, but it needs to be out of run, ventilation primarily by windows

• activity of occupants need to be closely to sedentary action with a metabolic rate of 1 to 1.3 met.

• occupants need to be free to adopt autonomously clothing towards activity, in – and outdoor temperatures.

• outdoor temperatures shall be in a range between +10 and +33°C. If outdoor tempera-tures exceed +33°C, predictions according to PMV limit bands are no longer reasonable

FIGURE 2.15 Adaptive control algorithms for diverse European countries according McCartney & Nicol (2002)

FIGURE 2.16 Differentiated and detailed calculation methods of lower and upper comfort temperature bandwidths accd. Borgeson & Brager (2011)

51 Literature survey and empirical evaluation of thermal comfort in sun spaces

Beside the optimal comfort temperature To,op as part of the ASHRAE 55 developed by deDear and Brager at the end of the nineteen nineties and with revision in 2002 [26], McCartney and Nicol [27] conducted 2002 thermal comfort algorithms for diff-erent inspected European countries in order to determine climate related comfort bandwidths.

Figure 2.15 shows a tabular survey. In relation to the operation mode, different standards provide calculation methods for upper and lower 90 to 80% acceptability comfort bandwidths. For standards focusing on adaptive comfort, the mean daily temperature, mean daily temperature of the previous week or the mean of daily minima and maxima of external temperature are basis for actual day calculation.

Borgeson and Brager [28] surveyed the methods in 2011 (Fig. 2.16).

Upon this fundamental descriptive knowledge in science a proper choice of applicable methods for sun space is essential. The next section rates by table the eligibility of applicable standards.

§ 2.4.3 Methodology : applicable procedures for sun spaces depending on season

Especially for sun spaces as extremely glazed and local climate impacted spaces in-door thermal comfort is a complex issue. Since, sun spaces tend to react amplitude-modulated [29] on external local climate impact despite optimum thermal insulation and sun protection and since maximum transparency may suggest a reduced percep-tion of shelter thermal comfort calculapercep-tion on heat balance model basis could become unilateral. However, sun spaces seldom are mechanically ventilated or actively cooled.

For that reasons PMV and PPD calculation can turn into nonsense.

FIGURE 2.17 Survey of calculations procedure for thermal comfort in sun spaces

Moreover, since sun spaces per definitionem incorporate considerable area of openings for natural ventilation, a thermal comfort calculation according the adaptive approach may be sufficient in summer under certain conditions (maximum and minimum external temperatures within the limitations), but strongly restricted in winter by reason of extreme low external temperature which drastically limits window opening.

Thus thermal comfort calculations for sun spaces firstly are limited to evaluations of cumulative frequencies of hours with sufficient operative temperature and secondly to evaluations of the operational temperature related to the running mean of external temperature and generated upper and lower comfort band limits, and thirdly to com-fort charts relating relative humidity and detailed analysis of local discomcom-fort.

Figure 2.17 gives a tabular survey of procedures available and procedures actually applicable for sun spaces.

53 Literature survey and empirical evaluation of thermal comfort in sun spaces