Adaptive Comfort Degree-Days: an index to compare adaptive comfort standards and estimate changes in energy consumption for future UK climates

This paper introduces the concept of the Adaptive Comfort Degree-Day, a temperature difference/time composite metric, as a means of comparing energy savings from Adaptive Comfort Model standards by quantifying the extent to which the temperature limits of the thermal comfort zone of the Predicted Mean Vote Model can be broadened. The Adaptive Comfort Degree-Day has been applied to a series of climates projected for different locations (Edinburgh, Manchester and London) under different emissions scenarios in the United Kingdom for the 2020s, 2030s, 2050s and 2080s. The rate at which energy savings can be achieved by the European adaptive standard EN15251 (Category II) was compared with the ASHRAE 55 adaptive standard (80% acceptability) during the cooling season. Results indicate that the wider applicability of the European standard means that it can realise levels of energy savings which its counterpart ASHRAE adaptive standard would not achieve for decades

The Energy Cost of Cold Thermal Discomfort in the Global South

The Global South, much of it in warm tropical latitudes, is expected to double its total energy demand by 2050. In addition to increased mean demand, greater demand for space cooling during external temperature peaks will exacerbate the strain on already fragile energy networks. Recent anecdotal evidence that a proportion of the increase in cooling demand is driven by cold-rather than warm-indoor thermal discomfort, suggests the imposition of an unnecessary cooling energy cost. Here, we investigate the impact of this cost on the expanding Global South using field data from four cities in India, Philippines, and Thailand. We observe that mean cold discomfort across the four cities is roughly 45 percentage points higher than warm discomfort, suggesting warmer indoor temperatures would not only lower overall discomfort but also reduce cooling energy demand. Computer simulations using a calibrated building model reveal that average savings of 10%/Kelvin and peak reductions of 3%-19%, would be feasible across the expected external temperature range in these cities. This suggests that more climatically appropriate indoor thermal comfort standards in the Global South would not only significantly counteract the expected rise in energy demand, but also produce more comfortable indoor conditions and reduce peak demand.</p

Overheating Risk in Passivhaus Dwellings

Highly insulated and airtight homes designed to reduce energy consumption are perceived as having a greater summer overheating risk than less insulated homes. If true, dwellings built to the well-known low-energy Passivhaus (PH) standard could be at greatest risk due to the use of superinsulation, especially as the climate warms. Existing studies are inconclusive and even contradictory, mainly due to small sample sizes. Hence, this paper presents the first large-scale overheating risk analysis of UK Passivhaus dwellings using high-resolution internal temperature data from 82 homes across the UK. Both the Passivhaus and the recently published Chartered Institution of Building Services Engineers TM59 criteria are analysed. Results show that the whole-dwelling Passivhaus standard, which uses a fixed temperature threshold, is met more frequently (83%) than when applied on a room-by-room basis (e.g. only 60% of bedrooms in houses meet the standard). TM59-1A, which uses an adaptive temperature threshold, is easier to meet with 100% of flats and 82% of houses in compliance. However, 55% of bedrooms assessed under TM59-1B fail, with little difference between flats and houses. This is a remarkable finding given that the summers under consideration were either typically mild or cooler than average, and that sleep impairment can significantly affect both physical and mental health. These results suggest that highly insulated dwellings such as Passivhaus should consider overheating in individual rooms, rather than at whole-dwelling level. Analysis should be undertaken throughout the year with particular attention to bedrooms, using either the good-practice PH-5% exceedance threshold which maps well to TM59-1B, or TM59-1B itself. Practical application : Overheating risk in new dwellings is an industry concern. Having the correct tools to predict this risk at design stage is important to help design comfortable and healthy dwellings for both today's climate and future, hotter climates. Comparing two different tools and their methodologies using in-use data is critical to gain confidence in their application at the design stage and to further understand overheating risk, including which dwelling types and rooms are more vulnerable to overheating.</p

Providing Passivhaus: Post occupancy evaluation of certified Passivhaus homes in the UK

Highly insulated and airtight homes designed to reduce energy consumption, are perceived as having a greater summer overheating risk than less insulated homes. If true, dwellings built to the well-known low-energy Passivhaus standard could be at greatest risk due to the use of superinsulation, especially as the climate warms. Existing studies are inconclusive and even contradictory, mainly due to small sample sizes. Hence, this paper presents the first large-scale overheating risk analysis of UK Passivhaus dwellings using high-resolution internal temperature data from 82 homes across the UK. Both the Passivhaus and the recently published CIBSE TM59 criteria are analysed. Results show that the whole-dwelling Passivhaus standard, which uses a fixed temperature threshold, is met more frequently (83%) than when applied on a room-by-room basis (e.g. only 60% of bedrooms in houses meet the standard). TM59-1A, which uses an adaptive temperature threshold, is easier to meet with 100% of flats and 82% of houses in compliance. However, 55% of bedrooms assessed under TM59-1B fail, with little difference between flats and houses. This is a remarkable finding given that the summers under consideration were either typically mild or cooler than average, and that sleep impairment can significantly affect both physical and mental health. These results suggest that highly-insulated dwellings such as Passivhaus, should consider overheating in individual rooms, rather than at whole-dwelling level. Analysis should be undertaken throughout the year with particular attention to bedrooms, using either the good-practice PH-5% exceedance threshold which maps well to TM59-1B, or TM59-1B itself

EXTREME COLD DISCOMFORT IN EXTREME HOT CLIMATES, A STUDY OF BUILDING OVERCOOLING IN OFFICE BUILDINGS IN QATAR

Indoor cold discomfort in Qatar due to “building overcooling” is increasing, as air-conditioning prevails, and global temperatures rise. Overcooling is not dependent only on the inappropriate design of cooling systems, but on “international” thermal comfort standards that are not customized for warm climates. International standards are unintentionally biased towards cooler climates and cultures, the application of which in warm climates result in colder indoor temperatures observed by building occupants and increased cooling energy demand. Overcooling is an over-expenditure of energy, resulting in uncomfortably cold indoor thermal conditions, and unnecessary carbon emissions. In this study, the analysis of field data from 6 office buildings in Doha in a range of indoor thermal conditions and investigation of overcooling on occupant comfort and building performance is conducted. The analysis uncovers over 35% of occupants state being uncomfortably cold and a consensus across the surveys highlight comfortable temperatures higher by 2°C from current setpoint temperatures. Greater occupant comfort and energy efficiency are found by increasing the indoor temperature setpoints investigated through thermal comfort analysis and energy simulation models. Around 50% decrease in occupant discomfort and a 15% decrease in cooling energy demand is found. Such an adjustment in Qatar would improve occupant comfort levels and reduce cooling energy demand throughout the existing office building stock

The Future of Thermal Comfort in a Warming World

Building cooling energy demand in the warmer climates of the world is increasing due to population growth and built environment expansion. Currently, cooling energy demand is increasing at a rate of 8% per annum, and this is projected to increase more rapidly with global warming. However, much of this demand is driven by unsustainably low indoor building temperature set points, that are also fundamentally seen as undesirable by most building occupants. In this study, we examine the effect of this “overcooling” in a changing climate using data from Qatar as a case study of a location with high average and peak external temperatures. Field data from 4 buildings in public and private settings demonstrate that cold discomfort is about 20 percentage points higher than warm discomfort due to excessive air-conditioning. Computer energy simulations using morphed future weather data and the extrapolated effect of observed low internal building temperatures, demonstrate that overcooling exacerbates the effect of a warming world by 16 percentage points. In other words, the use of more climatically appropriate thermal comfort standards that avoid unnecessary overcooling could reduce 28% of global carbon emissions in a future warmed world. As anecdotal evidence of excessive cooling in other warm climates demonstrates that the effects of overcooling are true, the reduction of building overcooling results in a greater achievement of thermal comfort, a decrease in cooling energy consumption, and a decline in carbon emissions across the warm climates of the world

'The older I get, the colder I get' - older people's perspectives on coping in cold homes.

An average of 26,560 UK excess winter deaths occur in people 65+ years old each winter, of which 30% are attributed to cold homes. Cold homes are known to exacerbate health problems prevalent in the 65+ demographic. Through conducting interviews in homes occupied by 65+-year-olds known to be achieving less than the World Health Organization (WHO) minimum recommended temperature (18ºC), this article highlights their struggles in maintaining health and managing their homes, with instances of extreme and potentially dangerous methods to achieve thermal comfort identified. Fairer energy provision, better targeted financial aid, and improved support networks are necessary to alleviate current problems.</p

Normalising domestic space heating demand using post hoc models

Current evidence suggests that the energy performance gap between predicted and actual use of energy in buildings is significantly weighted towards under prediction and can be as high as 200%. High-quality modelled and actual data are needed to ensure like for like comparisons when investigating the energy performance gap. Internal temperature (t i) normalisation is a key process to ensure like for like comparisons but is often hampered by the lack of the original model due to the time lag between design, construction and occupancy. Here, we demonstrate the use of models created after data collection – i.e. post hoc – as a substitute for original models in evaluating the energy performance gap. The robustness of the internal temperature normalisation factor (f ti) is tested using measured data from 20 Passivhaus homes. The data from each home are inputted into 10 Passive House Planning Package and 10 Standard Assessment Procedure models with highly different domestic and non-domestic building configurations, creating 400 model variants. Each variant is further split into four cases of varying internal gains and solar radiation creating a total of 1600 variants. Results demonstrate that f ti is resilient to differences in building configuration, solar radiation levels and varying internal gains (SEM &lt; 0.02). Even though SEM increases when measured internal temperatures are below base assumptions, the impact of this error on the computed space heating demand is at most 4%. This suggests that post hoc models can be a substitute for actual models in evaluating the energy performance gap and that limited site data can still yield robust results. Practical application : Identifying the causes of the energy performance gap (the difference between modelled and measure energy demand) is complex. Normalising space heating demand for internal temperatures means that some differences between modelled and actual space heating demand can be accounted for. Building models such as Passive House Planning Package (PHPP) and Standard Assessment Procedure (SAP) are readily available and allow variations in climate and temperature data to be inputted. This research demonstrates that in practice any PHPP and SAP model can be used for normalisation, not just one that is building specific and that some parameters (internal temperature) are more important than others. This provides a simple and easily accessible approach to temperature normalisation that can be applied by industry to domestic dwellings. </p