PhD, Professor Building Physics and Indoor
Climate at Augsburg University of Applied Sciences in Augsburg, Germany
PhD, managing director BBA Indoor
Environmental Consultancy, The Hague, the Netherlands.
buildings that were built or retrofitted in the last 20 years use a Building
Automation System (BAS). BASs are installed to achieve efficient operated
buildings and a reduction of their energy use and operating costs. At the same
time BASs allow tight control of the indoor climate in line with requirements as
defined in guidelines, standards and building decrees. But this tight control does
not necessarily lead to higher occupant satisfaction or lower complaint rates.
In Part 1 of this article, published in REHVA Journal in June 2017, we
discussed importance of control, effects of control and mechanisms involved
(Hellwig & Boerstra, 2017). https://www.rehva.eu/publications-and-resources/rehva-journal/2017/032017/personal-control-over-indoor-climate-disentangled-part-1.html
Control, Occupant Behaviour, Indoor Environment Quality (IEQ), Integrated
Design, Energy Efficiency, Smart Buildings, Building Automation System (BAS), Building
Management System (BMS)
follow-up article Part 2 we answered 10 frequently-asked-questions about control,
as an addition to the first 10 questions answered already in Part 1. We
explained more about the factors influencing personal control of the indoor
climate and discussed the design implications. The examples presented mainly
focus on control and control effects in office buildings. We conclude Part 2
with suggestions for the future indoor climate guidelines and some general
thoughts on further control studies. The answers presented in this article are
based upon our own research (as described in e.g. Boerstra, 2016, Hellwig, 2005
and Hellwig, 2015), the work of other researchers and the feedback from
participants during workshops at the Clima 2013 conference and the Indoor Air
2016 conference (reported in: Boerstra & Simone, 2013 and Hellwig &
The 10 questions as answered in
Q1: What do we
mean with personal control?
Q2: Is control
over indoor climate really an issue for the modern office worker?
Q3: What are the
main problems with control over indoor climate in existing buildings?
Q4: How does
control over indoor climate affect comfort and satisfaction in offices?
Q5: Is there an
impact of installation type?
Q6: How about
the effect of control on Sick Building Symptoms?
Q7: How does
control over indoor climate affect productivity?
Q8: How about
sick leave effects?
Q9: What do we
know about the mechanism involved?
Q10: How about
the difference between available, exercised and perceived control?
What are the
factors influencing the perceived level of control?
level of personal control is perceived (perceived control) depends on many
factors. First: the access to wall thermostats, operable windows, fans and
other controls and effectivity of these controls. Furthermore: a person’s
actual physiological state, his/her expectations and actual preferences, a person’s
personality and experiences, his/her beliefs how successfully he/she can cause
changes, a person’s competences or skills, knowledge of the building and its
technical systems as well as success or failure in previous behavioural control
actions in the actual or other buildings. Finally, it is important that a
person can sense whether the actual control action exercised generally is successful
(Figure 1, from Hellwig, 2015).
Factors influencing the level of personal control perceived (condensed
conceptual model of perceived control from Hellwig, 2015).
Is there an impact
of building facade on the level of control?
is. The building’s facades design, insulation, thermal mass and the
interrelation with the HVAC and BAS system drive a building’s responsiveness
under changing external and internal loads. More importantly, the
responsiveness of the building towards a control action initiated by an
occupant needs to be perceptible for the occupant. Otherwise the occupant may
experience that his/her control action generally is not successful (Hellwig,
2015). On the other hand, traditionally heavy to medium thermal mass buildings
with a low to moderate window-to-wall ratio equipped with operable windows and
thermostats for heating only are often perceived as offering sufficient control
(see e.g. Boerstra, 2016). We assume that it is important to occupants that –
based on the experiences from the past - they can (unconsciously) foresee a
building’s thermal behaviour. Predictability of thermal performance would be
higher in the above described building type, compared to a highly glazed
light-weight building immediately responding to changes in solar loads.
What are other constraints
from the built environment?
One important example is space layout. An open-plan office tends to
reduce the availability of the window access for the occupants, affects whether
the windows are operable or not and determines the heating or cooling system
for such space – most often via mechanical ventilation which normally provides
less personal control but zonal control. Furthermore, the office plan layout
can also result in constraints for the social environment (see next question).
Constraints of the building could also be windows which can be opened only with
a small gap of few centimetres or fixed thermostats which cannot be adjusted.
In other word: all control opportunities which look as they could be adjusted
but in fact they cannot, are likely to be perceived as a constraint.
are constraints from the social environment?
constraint is, for instance when there is a need to negotiate with others
before taking a control action, as in group or open-plan office layouts (Leaman
& Bordass 1999). A social constraint is also when behavioural instructions
are implemented by the company or the facility management. Think e.g. of
organisation constraints in relation to the use of operable windows or
restricted clothing protocols. These kinds of instructions ‘from above’ will
reduce individual freedom to adjust one’s local indoor climate and hence limits
the perceived level of control.
Is having more
control options always better?
necessarily. There is a finding called the jam paradox or paradox of choice
(Iyengar & Lepper, 2000). Jam paradox refers to an experiment about jam buying
decisions (choose from a collection of jars with different marmalades, with
varying choice options) could also be applied to control in buildings (Hellwig,
2015). The experiment showed that generally speaking people enjoy extensive
choice options. But when people have too many choice options this leads to information
overload, i.e. too many distinctive features between the options, resulting in a
stressful and demotivating situation because it’s so hard to evaluate variables
when these become too abundant. Subsequently people take fewer choices and if
they choose they will be more dissatisfied with the choices taken. Therefore, it is better to offer an appropriate amount of
control options. In order words: too little choice options is a problem, but
too many choice options is so too.
Q16: How about just putting a dummy thermostat on the wall?
Dummy thermostats are non-connected, fake
temperature knobs that promise some level of control over the thermal
environment but in fact are non-functional. Although often proposed when HVAC
technicians are confronted with indoor climate problems, on the long term the
introduction of dummy stats is one of the worst things to realise! Sooner or
later, users will find out that their usage of the dummy control device does
not have any effect. This can result firstly in a loss of confidence in their own
capabilities or in a loss of trust in building systems or the facility manager.
Users then may conclude that the building operates by chance or that the facility
manager did not treat their complaints seriously. This will make them more
critical of the functioning of the building (Hellwig, 2015). In Dutch offices
it was found that effective personal control options in offices can decrease
the amount of complaints when compared to none or ineffective personal control.
If controls are ineffective, like dummy controls, the potential for complaints
can be even higher compared to the case with no control at all (Boerstra & Beuker,
designing a new building or retrofitting an existing building, what measures
should one take in order to boost personal control?
cases it pays off not to just provide in an HVAC system that has the right
amount of heating, cooling and ventilation capacity but also to (re)design for
adequate indoor climate adjustability. Depending upon the situation one can use
low tech or high-tech controls. In case of a retrofitting project, it is
advisable to find out what are the most liked (control) features in the old
building and keep them in the new building. Think e.g. of existing operable
windows. Also, finding out what controls the occupants miss in the old building
and add them in the new building can help for higher satisfaction in the new
building. In newly designed buildings one can decide to introduce more
innovative control solutions like micro-climatisation systems (HVAC integrated
in work tables and/or chairs). General strategies for high perceived control
over indoor climate are: to reduce the number of persons sharing one office, to
ensure the accessibility of control devices for the occupants, and to rely on
user-friendly interfaces, and to aim for control over temperature, fresh air
supply and lighting (Figure 2).
User-friendliness considers common routines of occupants or mounting
requirements for new control devices; left: using a light switch when entering
a room, right: a traditional mounting height as shown is inappropriate for new
control devices (photos/montage: R.T.Hellwig).
Are there guidelines
explaining how a good control device should be designed?
There is an
excellent guide by Bordass, Leaman & Bunn (2007) on good design for
controls for end-users and their implementation. There is also an international
standard ISO 9241 on human-computer-interaction which describes principles of
usability: effectiveness in solving a task or problem (successful task
completion by users), efficiency in handling the system (task in time), and
satisfaction of the user. Very useful additional information about controls and
usability can also be found in Karjalainen, 2007.
Q19: What about expectation management
in relation to controls and control effectiveness?
control-technologies are suggested for implementation, a building system
designer has to explain why the new technology provides benefits. The person
suggesting the new technology tends to be very enthusiastic about it (otherwise
he/she wouldn’t propose it). This enthusiastic attitude will raise the user
expectation sometimes to the skies! But raised expectations could lead to
disappointment later, even if the overall indoor climate has improved
objectively. Therefore, it is important that the owner or user has realistic
expectations which are consistent with the performance of the system after the
building is commissioned. Furthermore, it is important for a building system
designer not to discourage the prospective user from taking control actions.
For overall satisfaction it is supportive if an occupant feels responsible for
the indoor climate at his workplaces to a certain degree. Otherwise, the
occupant has to rely too much on a building’s autonomic behaviour or changes to
be implemented by the facility manager.
suggestions for future work and needs?
the indoor climate exactly according to the standards is probably not enough.
As one and the same person might have different needs at different times due to
day to day or hour to hour differences in tasks, metabolism, season, actual or
previous activity, mood, health status, personal control opportunities are a
key element for the future buildings. We see the need for design guides on
personal control in indoor environments for planners and we see a need to expand
the scope of the standards which so far aim at thermal comfort by incorporating
the objective of providing appropriate effective controls. We also see that advanced
knowledge on constraints and on effectiveness of control actions is required.
Furthermore, we still lack sufficient knowledge on what would be an appropriate
and sufficient amount of personal control in different contexts.
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