Escape the Comfort Zone

Published on 30.07.2023
This knowledge was donated by:
Transsolar KlimaEngineering
TU München
Curated by Dr. Anna Braune

How do you achieve the highest possible indoor comfort with the least possible impact on the environment? And: How can thermal comfort in buildings be provided sustainably? We have compiled a catalogue of measures for you.

Measures to improve thermal comfort

  • The less active building technology and more passive measures, the higher the user acceptance
  • User interaction through individual influence on room conditioning (e.g. window ventilation, sun protection, simple and understandable user interface, etc.)
  • User sensitisation through intelligent monitoring and feedback interface
  • Consider user behaviour during operation (e.g. window ventilation or overriding of the sunshade)
  • A constant setpoint temperature all year round is not suitable for individual thermal comfort in the room
  • The more variability is tolerated in terms of clothing and activity levels at the workplace, the less energy is required and individual comfort is maximised at the same time
  • A low room temperature in summer (< 25 °C) tends to lead to an increase in the rate of discomfort (draughts, etc.)
  • A higher room temperature in winter (> 20°C) tends to lead to low relative humidity; the dry air dries out the mucous membranes and increases susceptibility to infectious diseases
  • Enhance thermal, olfactory and hygric comfort with materials (wood, brick, clay) or plants
  • Flexibly adapt workstations and their layout to individual user requirements

In addition to this topic, we recommend the lecture "High Comfort - Low Impact" by Prof Thomas Auer. The Managing Director of Transsolar specialises in sustainable climate and energy concepts for buildings and their rooms and conducts research at the Chair of Building Technology and Climate-Friendly Construction at the Faculty of Architecture at the Technical University of Munich.

Click on the image to access Thomas Auer's presentation "High Comfort - Low Impact" on YouTube

Background knowledge

Humans feel heat and cold through receptors in the skin. These thermoreceptors inform the brain that it is "too warm" or "too cold", although many more receptors are programmed for cold. The sense of temperature is the only human sensory system that exclusively reports information to the brain when discomfort occurs.
The body generates heat through metabolic processes, but at the same time it has to keep its core temperature constant. The body is therefore in constant heat exchange with its environment. This happens through

  • Evaporation of fluids via respiration and skin
  • Convection from the surface of the skin and via respiration to the air in the room
  • Heat conduction from the body to objects
  • Heat radiation to room-enclosing surfaces and surrounding objects

Six primary factors determine thermal comfort

In principle, thermal comfort is achieved when the body's overall heat balance is in equilibrium. Six factors are regarded as the primary and dominant factors for thermal comfort:

  • Heat production by the metabolism (metabolic heat production) depends on the activity of the person. It is abbreviated as met (metabolic rate).
  • Heat exchange with the environment depends on physical factors such as
  • air temperature,
  • average radiation temperature,
  • humidity and air velocity.
  • Added to this is the degree of clothing, which also influences heat exchange. It is abbreviated as clo (clothing factor).
    Physiological (e.g. age and gender) and intermediate conditions (e.g. time of day/season and acclimatisation) also play a role.

The static comfort model

In the 1970s, the Danish scientist Ole Fanger researched people's perception of warmth in a series of tests with numerous test subjects and developed a static comfort model depending on the six primary factors (see above) based on empirical investigations of individual perception.
This resulted in the so-called Predicted Mean Vote (PMV) - a scale of +3 (too warm) and -3 (too cold) with 0 as neutral. The PPD (Predicted Percentage of Dissatisfied) can in turn be determined from the PMV. In line with the human sensory system, we are also talking here about the number of dissatisfied rather than satisfied people. The lower the PPD value, i.e. the lower the percentage of dissatisfied people or the closer the PMV value is to 0, the better the comfort in a room is by definition.

The adaptive comfort model

On the other hand, there are adaptive comfort models. In addition to the user's thermal perception, they also take into account measures for adapting to the environment and different expectations regarding the indoor and outdoor climate. Here, temperature limit values for the indoor temperature are defined as a function of the outdoor temperature, the type of room air conditioning and an average of the outdoor temperature over the last seven days of the building. These upper and lower limits for the air temperature thus define a comfort range. As the criteria and requirements increase, the limit values change and the comfort range becomes narrower. However, narrow comfort limits throughout the year are neither legally prescribed nor healthy.

Tip

Leaving the comfort zone means, among other things, allowing more room for manoeuvre for individual user comfort!

Nevertheless, both methods in combination with indoor air movement form the basis for many German and international standards and certification systems for evaluating thermal comfort in buildings. In this respect, the question arises as to whether this method is the right approach for providing thermal comfort in buildings in a sustainable manner.

Conclusion

Particularly in view of increasing requirements due to greater flexibility and individualised working conditions and assuming variable levels of clothing and activity as well as more air movement, a wider comfort band means more scope for individual user comfort. A wider comfort band therefore saves considerable energy on the building technology side and reduces the level of technical installation in the building.

This knowledge was donated by:

Transsolar KlimaEngineering
The aim of climate engineering for buildings is to achieve the highest level of comfort for users with the least possible impact on the environment. Transsolar strives to achieve this by developing and validating innovative climate and energy concepts. Transsolar Energietechnik GmbH was founded in 1992 and now works worldwide with 50 engineers in offices in Stuttgart, Munich, New York and Paris. our consultancy aims to achieve maximum user comfort with minimum energy consumption. We take into account the fact that environmental conditions and planning influence each other. Right from the start of the planning process, we work closely with clients, architects, building services engineers and other consultants and assess every step according to the laws of thermodynamics and physics. This results in a climate concept in which the local boundary conditions, the form, the material and the mechanical systems are synergetic components of a harmonised climate control system. Our aim is to create ecological, economical and high-quality buildings for living and working with a high level of user comfort, or in short: we see climate engineering as an expression of the highest respect for people and nature.
Please send contact enquiries to:
Mail: frenzel@transsolar.com
TU Munich
The Chair of Building Technology and Climate-Friendly Construction at the Department of Architecture at the Technical University of Munich (TUM) focuses its research and teaching on the holistic optimisation of buildings, taking into account future developments with regard to the sustainability goals of the European Union (EU): The EU's Carbon Roadmap envisages a 90% reduction in CO2 emissions from the building sector by 2050 compared to 1990 levels. Through user-orientated and practice-oriented teaching and research, the Chair gains and imparts knowledge about the holistic view in the building-city context. On the one hand, the building structure, façade and building technology are harmonised with each other, and on the other hand, the approach is expanded at city level to include the parameters of energy supply and the use of synergy effects. A particular focus of the chair's work is on the interdisciplinary and cross-disciplinary Bachelor's and Master's training of future architects and engineers. As part of research projects and expert reports, the focus is on the use of simulation programmes as a planning tool for the mathematical mapping of thermal, light and flow-specific processes. This provides practice-relevant findings on the topics of user comfort, energy consumption and daylight supply. The projects completed in recent years and those currently underway include research commissions from federal and state ministries as well as co-operations with large industrial companies, SMEs and planning offices.
Please send contact enquiries to:
Mail: christian.hepf@tum.de
Web: https://www.ar.tum.de/klima/startseite/