The effect of the indoor environment quality (IEQ) on cognition and health

With global warming, average outdoor temperatures experienced during spring and
summer are rising along with humidity levels. The changes in outdoor
temperatures greatly affect older buildings that do not have mechanical systems
to regulate indoor temperatures. As humans spend the majority of their time
indoors (cooking, exercising, sleeping, and working), the internal environment
affects health and performance. Human thermoregulation is influenced by the
environmental exposure, duration, and activity. The indoor environment includes
temperature, humidity, light, sound and air quality. In order to reduce energy
use and carbon emissions, older homes need to be renovated to meet new energy
labels. The indoor environment of homes would greatly change with added
insulation.

A well-insulated home loses less heat, reduces energy use and heating costs
during the winter. However, this may cause overheating due to inability to lose
heat quickly during the summer. When a home has a higher insulation value,
there is a reduced natural ventilation capacity and this may lead to an
increase in moisture in rooms due to activities like cooking, exercising and
showering. A reduced ventilation capacity leads to an increase in moisture and
pollution within the indoor environment and a perceived lower quality of the
indoor air; which can be further exasperated with an increase in the number of
occupants and occupancy duration. Moreover, the body*s ability to lose heat
through evaporation and convection is dependent on environmental airflow and
humidity levels. In hotter (>32 ºC) and more humid environments (>70%),
detrimental effects on cognitive and physical performance have been shown in
shorter exposures lasting less than 3 hours.

Main research question and primary objective:
What is the effect of exposure to high vs. neutral temperature (32* C vs. 25*
C) in combination with high vs. low humidity (30 %RH vs. 70 %RH) for 8 hours on
cognitive performance?

Secondary research question and secondary objective:
What is the effect of high vs. neutral temperature (32* C vs. 25* C) in
combination with high vs. low humidity (30 %RH vs. 70 %RH) on physiological
responses, environmental perception, decision making, and bias behaviour?

Exploratory research question and objective:
What is the interaction effect of high vs. neutral temperature (32* C vs. 25*
C) in combination with high vs. low humidity (30 %RH vs. 70 %RH) on cognitive
performance, physiological responses, environmental perception, decision
making, and bias behaviour?

To study the effect of humidity on cognitive, physiological, and subjective
measures, a randomized cross-over trial will be carried out. The temperatures
deployed in this study are either 25ºC (NEUTRAL) or 32ºC (HIGH) and the
humidity levels are relative humidity (RH) of 30% (LOW) or 70% (HIGH). The
experiment will have four conditions (also see Table 1):

Condition 1) 25* C/30 %RH = NEUTRAL-LOW
Condition 2) 32* C/30 %RH = HIGH-LOW
Condition 3) 25* C/70 %RH = NEUTRAL-HIGH
Condition 4) 32* C/70 %RH = HIGH-HIGH

High temperature (32C) and high humidity (RH70%)

The study is not expected to pose a significant risk or any major burden to the
participant. There is reasonable time investment required due to recurrent
study visits and exposure to warm and humid condition may be experienced as
inconvenient. Subjects will perform several activities within the respiratory
research units of the MRUM and are not allowed to leave the room throughout the
measurements. Furthermore, subjects are asked to maintain their eating and
exercise habits 1 day before each measurement day of the study to limit
external influence on the measurement of energy expenditure.

Global warming is creating previously unforeseen summer weather conditions
(hotter and more humid) and heat waves in originally temperament geolocations.
High humidity affects both human heat storage and skin temperature due to
changes in evaporative heat loss (Li et al., 2018) and negatively affects the
perception of thermal comfort (Lan et al., 2008; Robin et al., 2017). High
humidity's effect on cognitive performances has not been evaluated for
durations longer than 3 hours in originally temperament environments like
Western Europe. That is why research is needed even given the
burden/inconvenience to human subjects to understand the effects of global
warming on human health, given the imminent direction the world is headed with
climate change.