Programma van Symposium Hybrid Ventilation

Acceptable temperatures for people in naturally ventilated buildings 
Susan Roaf (Heriot-Watt Universiteit) and co-author Fergus Nicol     

Setting aside the engineers definition of what comfort is in mechanically conditioned buildings, this talk looks at what comfort actually in in relation to the human experience in real buildings around the world. Comfort is actually a cultural construct experienced as temperature and personal feelings around them, not a product sold from a duct and measured only in energy and money units. The talk opens by looking at recent work by Fergus Nicol on what temperatures actually occupy in homes and offices around the world and establishing robust limits of what constitutes acceptable temperatures indoors. Then the actual key features of what makes people uncomfortable in buildings is discussed in terms of the rates and ranges of temperatures swings, leading onto the physical characteristics of buildings that will ensure they are acceptable comfortable for occupants over time. The talk concludes with the increasingly urgent need to temper the multiple functions of windows during heatwaves and exceptionally hot events.  Why does this matter, because in the words of Bjarne Olesen, ‘the future of buildings is that they will be run for as much of the day and year as possible with free natural energy, and only when necessary will they be heated and cooled’. To design such climate-ready and future facing buildings one has to understand what real comfort actually is.

Occupant behaviour, comfort and energy
Laure Itard (TU Delft)

Smart environments using a large amount of sensors can be used to understand better the relationships between occupant behaviour, thermal comfort and heating energy use. In the context of residential buildings occupant behaviour relates to how the occupants use the technical system, e.g. how often they open the window or change the settings of the mechanical ventilation, which thermostat settings they use, but also what type of clothes they wear and what type of activities they carry out in their homes. By relating these actions to the experienced thermal comfort, we can learn about the parameters influencing this thermal comfort in real life and how that does relate to heating energy usage. Several measurement campaigns have been carried out in Dutch houses, measuring temperatures, CO2-concentrations, humidity, gas and electricity use in different rooms of a few tens of house over long periods with time intervals of 10 minutes. The thermal comfort and its determinants were measured using an app registering also the time of answer. The results were coupled to surveys and house inspections and used to start answering a few questions like: Is the reported thermal comfort in agreement with PMV or adaptive comfort theory? What type of behaviours do we observe in practice and how do they relate to assumptions made in norms and designs? How do these behaviours affect the energy usage and can they explain the often disappointing energy performances of houses?

Aldo Vos (BroekBakema)

The Recovery of Natural Environments in Architecture
Alan Short (Universiteit Cambridge)

" We fundamentally question the capability of  the contemporary architectural idiom and its antecedents to cope with a changing climate. The recurrent forms for the principle contemporary building types were devised in the very different conditions of the mid-twentieth century and now need to be fundamentally re-invented. Prototypes for this reinvention were developing in very interesting and increasingly sophisticated ways until the introduction of ‘artificial weather’ in the late 1920s. Artificial weather released the design of buildings from the need to be responsive in any way to their external environments, impoverishing their meaning and their occupants' experience. We exhume these lost ideas and reinforce them with contemporary scientific insight and propose a recovery of the lost art and science of making more naturally conditioned buildings. Within the Urban Heat Islands of Temperate cities and in the more extreme Continental climates natural means need to be coupled with mechanical cooling optimised by intelligent controls. The situations of London, Chicago and Beijing will be considered."

The possibilities of hybrid ventilation (project TVVL Expert group Climate Technology, KT-26)
Michiel van Bruggen (De Energiemanager, member TVVL Expertgroup Climate Technology)
With hybrid ventilation fresh air supply can be ensured, free cooling optimized and fan energy reduced by making use of natural ventilation. There are many options to apply hybrid ventilation in buildings, from standard buildings with balanced ventilation and operable windows to buildings with a ventilation design of which the use of natural ventilation with buoyancy and wind is a starting point. In the presentation design-issues and approaches are discussed. The presentation is based on the publication Hybrid ventilation of the TVVL.

Architecture, hybrid ventilation and daylight
Peter van den Engel (TU Delft)
In the past buildings were naturally ventilated and daylight was the main source of illumination. Indoor climate was mainly dependant on the type of façade, roof, thermal mass and local heating systems. Everywhere in the world examples of traditional buildings with an acceptable or good indoor climate can be found. In some way it could be prototypes for modern buildings. Of course, occupants also adapted themselves, which generally had a positive effect on their health. On the other hand, requirements for architectural expression, usage, comfort and energy are different now, which requires a new approach. The insulation of buildings, of the opaque and transparent parts, has improved in such a way that almost no spatial heating is required. Prevention of unnecessary cooling is now the main issue. Finding the right proportion of daylight and solar radiation, in every season and at different weather, has become an important design goal. Natural and low pressure ventilation offers many opportunities to improve local comfort and reduce fan and cooling energy. There is a strong relation with the design of the façade and architectural expression. Several examples from all over the world will be discussed.