What is THERMAL COMFORT?
The most commonly used definition for THERMAL COMFORT according to the American Society of Heating, Refrigerating and Air-Conditioning Engineers (Ashrae) is “That condition of mind which expresses satisfaction with the thermal environment and is assessed by subjective evaluation”. Although thermal sensitivity varies from one person to another, according to age (the very young and very old being particularly sensitive), gender, dress, activity, cultural habits, etc., the basic principles
behind thermal comfort are largely universal.
The THERMAL COMFORT is experienced via a number of conscious interactions between three personal
and environment factors:
- Physiological : the way our bodies work and interact with our environment;
- Physical : the main parameters of the environment around us (air temperature, air humidity, air movement, room surface temperature);
- Socio Psychological: the way we feel as a whole (for example, if we are tired, stressed, happy…) and the kind of social environment we live in.
The physiological aspect
Regulation systems within our bodies continuously strive to balance our heat exchanges with the environment, by speeding up or slowing down our heartbeat to modify our blood flow and regulate heat distribution; by shivering when too cold in order to increase heat production; by sweating more when too hot to reduce skin temperature thanks to evaporation.
A comfortable indoor environment limits the efforts our bodies need to make to regulate body temperature, establishing a good energy balance.
The physical aspect
In the physical environment, thermal energy (heat or cold) is transferred through conduction, radiation and convection.
Conduction is energy transfer via a solid, such as the floor or wall. Convection is energy transfer from a solid to an adjacent gas or fluid (air or water). And radiation is the energy emitted from a surface, such as a radiator.
The socio psychological aspect
An individual’s current emotional state, mood, level of fatigue, etc. will affect their experience of an environment. Expectations play an important role in how an individual experiences the physical world: one would expect a beach to be hot and a mountain lodge to be cool, but more generally, perceptions are likely to based on one’s own thermal history. Other environmental factors, noise or glare for example, may influence thermal perception, leading to an increased sensation of overheating.
DID YOU KNOW?
Around 90% of UK hospital wards are of a type that’s prone to overheating, and the ability to control
temperatures is often limited.
DID YOU KNOW?
A cold home is bad for your health and increases the risks of cardiovascular, respiratory and rheumatoid diseases as well as worsening mental health. Cold homes are a significant contributor to the level of excess winter deaths in the UK every year. In 2009, there were an estimated 25,400 excess winter deaths, over 21% are attributable to the coldest quarter of homes.
WHICH FACTORS INFLUENCE OUR THERMAL COMFORT?
A balanced thermal environment is essential to feeling comfortable.
Concentration, manual dexterity and the occurrence of accidents are all influenced by excessively high or low temperatures. Operative Temperature and Relative Humidity in a space determine Global Comfort conditions, depending on what we are wearing and what we are doing. Our bodies are also sensitive to small variations in factors such as Air Velocity and Temperature Gradient. The impact of local discomfort elements must be minimized so we can fully enjoy the space and function comfortably, whatever we’re doing.
The THERMAL COMFORT is determined by:
- Air temperature
- Surface temperatures
- Absence of draughts
The MULTI COMFORT Buildings must keep the ideal indoor temperature all year round using very little energy, have walls that are nice to touch or lean regardless of the weather outside and have no draughts even on the floor.
HOW DO WE DESIGN THERMAL COMFORT?
Key considerations for THERMAL COMFORT include:
Air tightness and ventilation
An airtight envelope, together with natural or mechanical ventilation, can control the indoor thermal environment by managing the air exchanges with the outside.
The materials used to construct the building (the choice of brick, stone or wood, for example) have an impact on how quickly changes in weather conditions are felt.
Through its overall shape, orientation, number and size of windows and the ability of surfaces to reflect heat, the building envelope can control how much heat from the sun (solar gain) is allowed to enter into the building.
Insulating the building envelope and using thermally efficient windows reduces heat loss in winter and conduction heat gains in summer.
THERMAL COMFORT is the outcome of a well-balanced combination of building systems adapted to both the location of the building as well as the type of activity performed within the building or the room of the building.
One of the first steps to consider is the design of an efficient building envelope. This acts as a filter between the exterior and the indoor climates. The building envelope can greatly affect the indoor thermal environment of the building through its management of the factors we mentioned.
MULTI COMFORT buildings keep your ideal indoor temperature all year round using very little energy, have walls that are nice to touch or lean on regardless of the weather outside and have no draughts, even on the floor.
Products and solutions for THERMAL COMFORT
Saint-Gobain offers several product categories that have a direct impact on thermal comfort.
- Glazing to let the sun in or block it out depending on the climate
- Insulation to reduce heat loss or summer heat gains
- Plasters and plasterboards to improve THERMAL COMFORT
- Smart membranes to improve airtightness and manage moisture
- Renders that insulate and provide weather defense
Examine the evidence of THERMAL COMFORT
"In a survey of more than 4,000 sixth grade students, those who reported that they had never experienced high indoor temperatures achieved 4 percent more correct answers on a national mathematics test compared to students who experienced high temperatures daily."Source: Haverinen-Shaughnessy, Ulla, Mari Turunen, Jari Metsämuuronen, Jari Palonen, Tuula Putus, Jarek Kurnitski, and Richard Shaughnessy. Sixth Grade Pupils’ Health and Performance and Indoor Environmental Quality in Finnish School Buildings.
“Exposure to extreme heat is already a health issue. Currently, one-fifth of homes in England could experience overheating, even in a cool summer. Flats, which are generally more at risk of overheating than houses, now make up 40% of new dwellings, compared to 15% in 1996. Urban greenspace, which helps to mitigate the urban heat island effect, has declined by 7% since 2001. In the UK, excess deaths from high temperatures are projected to triple to 7,000 per year on average by the 2050’s as a result of climate change and a growing and ageing population.”Source: Managing climate risks to well-being and the economy, Adaptation Sub-Committee, Progress Report 2014 (The Committee on Climate Change (the CCC) is an independent, statutory body established under the Climate Change Act 2008.)
“An analysis of 24 studies on the relationship between temperature and performance indicated a 10% reduction in performance at both 30°C and 15°C, compared with a baseline between 21°C and 23°C – demonstrating the impact thermal comfort can have on office occupants. A more recent study, in a controlled setting, indicated a reduction in performance of 4% at cooler temperatures, and a reduction of 6% at warmer ones.”Sources: Wargorcki P (ed), Seppänen O (ed), Andersson J, Boerstra A, Clements-Croome D, Fitzner K, Hanssen SO (2006) REHVA Guidebook: Indoor Climate and Productivity In Offices. Lan L. Wargocki P. Wyon DP. Lian Z. (2011) Effects of thermal discomfort in an office on perceived air quality, SBS symptoms, physiological responses, and human performance.