# Scottish Passive House: Insights into Environmental Conditions in Monitored Passive Houses
## 1 Introduction
### Thermal Comfort  
Thermal comfort is an important factor for occupants' health and wellbeing; this is influenced by their thermal balance, which can vary according to personal needs and cultural expectations [28]. The six basic factors of thermal comfort are Environmental parameters: air temperature, mean radiant temperature, air velocity, air humidity; and Personal parameters: clothing and physical activity [29].  
A current limitation for thermal comfort research in dwellings is that there are no defined standards for thermal comfort in domestic buildings with the existing parameters having been extrapolated from research assessing comfort conditions in offices. According to [PERSON] _et al._[30] (p. 3286) this is a problem in terms of our psychological responses to thermal conditions in that: \"Our mental state at home and the range of adaptive behaviours possible is distinct to that in the office and, therefore, perceptions of comfort are likely to be quite different\". In Passive House design, the optimum operating temperature is 20 \({}^{\circ}\)C, and the building is considered to have overheated if the indoor temperature exceeds 25 \({}^{\circ}\)C for more than 10% of the year, although a 4% limit is preferable [18] (p. 79).  
Comfort temperature, type of building, solar gains, incidental gains, ventilation levels and occupants can contribute to overheating [31]. There has been increasing interest in overheating in airtight dwellings in the UK [32; 33; 34; 35], focusing on two main considerations current summer overheating and future overheating in a warming climate. The future impacts of anthropogenic climate change and urban heat islands on overheating in energy efficient and airtight buildings has been identified as a potential problem [30; 32; 33; 34; 35] particularly in airtight, lightweight buildings with diurnal temperature fluctuations, requiring adaptation from occupants [30; 32; 36]. [PERSON] _et al._[27] used dynamic thermal modelling to identify that Passive Houses are also at risk of future overheating and these risks could be mitigated through the inclusion of solar shading and adjusting glazing ratios at the design stage. There also needs to be consideration of different climatic conditions and regional weather conditions in modelling to assess overheating risk [37].  
[PERSON] _et al._[24] studied Passive House flats occupied by social housing tenants and found that 72% of these properties failed to meet the Passive House thermal comfort criteria, the occupants contributed to the overheating which was a concern due to occupant vulnerability. A study of German, Austrian and Swiss Passive Houses by [PERSON] _et al._[38] stated that 88% of occupants were satisfied with their summer indoor climate suggested that mean indoor summer temperature range (from about 21 \({}^{\circ}\)C to about 27 \({}^{\circ}\)C) and reflected occupant conduct and individual preferences, with higher indoor temperatures being repeated in summer and winter months in the same homes. [PERSON] and [PERSON]'s [39] study of perceived comfort in Passive Houses indicated that the adaptive processes to thermal comfort in Passive Houses were impacted by the social aspects of occupants and their evaluation of their homes. In over half of the respondents, it was believed that their comfort level was contributed to by an increased level of \"perceived knowledge\".  
Where overheating has been identified as a current risk in UK homes, the focus has been on the summer months and predominantly in dwellings located in the midlands or south of England [24; 40]. However, research by the Mackintosh Environmental Architecture Research Unit (MEARU) has shown that overheating in Scottish homes is occurring throughout the year [41].