Conference PaperPDF Available

Interdisciplinary Parametric Modelling and Modularisation to Improve Air Quality, Acoustics, and Lighting in School Buildings

Authors:

Abstract

Poor indoor air quality, acoustics and lighting can affect well-being and productivity in classrooms. In naturally ventilated buildings, weather conditions and outside noise may prevent necessary window openings, making technological solutions appealing. The implementation of solutions to mechanically ventilate spaces and take the necessary measures to improve acoustics and lighting may however be met with resistance, either due to the perceived effort and cost of renovation measures or presumed disruptions to school activities. This work presents the development and implementation of a tool aimed at facilitating the planning and execution of interventions. A striking feature is its use of parametric rules, which are established to a.) modularise differentiated building components related to ventilation, acoustics, and lighting to a new product unit, thus reducing planning efforts through interface reduction, and b.) automate design generation for typical classroom configurations based on the availability of space, structural constraints, and good lighting practice.
Interdisciplinary Parametric Modelling and Modularisation to Improve Air Quality, 1
2
3
4
5
6
Acoustics, and Lighting in School Buildings
Clara-Larissa Lorenz1, Tobias Burgholz2, Maximilian Schildt1, Jérôme Frisch1, Christoph van
Treeck1
1RTWH Aachen University, E3D Institute of Energy Efficiency and Sustainable Building
2Heinz Trox Wissenschafts gGmbH, Aachen
7
8 Abstract
Poor indoor air quality, acoustics and lighting can affect
well-being and productivity in classrooms. In naturally
ventilated buildings, weather conditions and outside noise
may prevent necessary window openings, making
technological solutions appealing. The implementation of
solutions to mechanically ventilate spaces and take the
necessary measures to improve acoustics and lighting
may however be met with resistance, either due to the
perceived effort and cost of renovation measures or
presumed disruptions to school activities. This work
presents the development and implementation of a tool
aimed at facilitating the planning and execution of
interventions. A striking feature is its use of parametric
rules, which are established to a.) modularise
differentiated building components related to ventilation,
acoustics, and lighting to a new product unit, thus
reducing planning efforts through interface reduction, and
b.) automate design generation for typical classroom
configurations based on the availability of space,
structural constraints, and good lighting practice.
Introduction and Background
In classrooms, environmental qualities including air-
quality, acoustics, and visual aspects are known to
improve occupants’ attention and performance (Corgnati,
Filippi and Viazzo, 2007; Toftum et al., 2015).
Mechanical ventilation can help ensure appropriate levels
of CO2, which are frequently exceeded in manually aired
classrooms (Stabile et al., 2016). Acoustic measures can
reduce classroom noise and improve speech intelligibility.
Good lighting conditions can improve attention (Astolfi
and Pellerey, 2008). The installation of mechanical
ventilation units, sound absorbing surfaces, and lighting
necessitates the consideration of suitable positioning,
dimensioning (i.e. of acoustic panels) and distribution of
equipment (i.e. of outdoor and exhaust air vents, acoustic
panels, and luminaires). To facilitate planning and
procurement, an integrated consideration of building
components across different trades needs to be ensured.
This work proposes modularisation to reduce the
complexity in the design and procurement process. In
general, modularisation is used as a solution to manage
product variety, considering the technical requirements of
differentiated products and the interfaces between the
components involved (Ulrich, 1995). MEP-related trades
(mechanical, electric, plumbing) account for a vast
majority of building components (van Treeck et al.,
2019). These components typically have interfaces
between each other (e.g. pipe joints) and to further trades
(e.g. bracketry in fastening technology). The complexity
of products implies a high amount of geometry and
product data in planning and procurement, which is
further aggravated by the number of manufacturing
competitors in the respective fields. Recent developments
in the field have produced standardised data descriptions
of products to enable the use of machine-readable product
data catalogues from different manufacturers. Among
them is the product data exchange in building services
approach according to VDI 3805-100 (Verein Deutscher
Ingenieure, 2018), which is used in this paper for the
extraction of relevant product parameters into a product
package data record. Such data records constitute the
alphanumerical definition of product characteristics, and
have been implemented as interface plugins (e.g.
RubiCon) for common planning software such as
Autodesk Revit, and product data platforms, such as
BIM4HVAC (BDH Federation of German Heating
Industry), to enable the export of product data alongside
geometry. As part of the ongoing efforts to define the
product data exchange necessary for planning, ISO 16757
(Data structures for electronic product catalogues for
building services, based on VDI 3805) is currently under
development. This work gives an example of applying the
standard to create a new product unit constituent of an Air
Handling Unit (AHU), acoustic and lighting system and
related components, for which product information is
extracted to speed up the planning and procurement
process.
Parameterisation is used as a key tool within this work to
effectively modularise ventilation, acoustics, and lighting
for any given classroom configuration. Parametric
modelling has become a well-established design method
in the field of computational design. It is established by
defining design parameters as variables that can be
adjusted to create new design variants (Kanaani and
Kopec, 2015). One can differentiate between three
approaches to parametric modelling: a numeric,
constructive, and knowledge-based approach (Roller,
1991). This work is most closely based on the constructive
approach, which assesses geometric facts and performs
geometric construction based on rules and operations in a
predetermined sequence (Basak and Güselin, 2004).
The workflow and methods section describes the
functionality of the developed tool, followed by a case
study in which the tool was implemented. The next
sections present 1.) the process of developing a highly
customisable parametric model to replicate any given
classroom configuration, 2.) the dependencies and
constraints implemented to generate an integrated design
solution for ventilation, acoustics, and lighting, 3.) the
modularisation of product components to an assembly
unit to speed up preassembly and montage, and 4.) model
performance and limitations when applied to two case
studies.
Workflow and Methods
To facilitate interventions, a tool was developed in
Grasshopper (GH) for Rhino. It was designed to fulfil the
following tasks: 1.) enable easy modelling of typical
classroom configurations for which no experience with
the modelling software is required, 2.) automate the
generation of solutions for the placement and
dimensioning of AHU, acoustics, and lighting, 3.) output
required plans, the module dimension and the number of
modules for acoustic panels and ceiling luminaires, and a
machine-readable CSV (Comma Separated Value) format
recording all product data. The following sections detail
the processes implemented in Grasshopper to achieve said
tasks.
Parameterisation of design variables to model typical
classroom-configurations
To enable the modelling of typical classroom
configurations, design variables related to room
dimensions, windows, and structural elements were
parameterised. A complete list of the parameterised
variables is given in Table 1 and Table 2. The required
input for all design variables can be provided via slider
adjustment or specified in the slider editor (Figure 1,
Figure 2).
Figure 1: Slider functionality in GH
While some variables require an input (Table 1), the input
for others is optional (Table 2). The room dimensions,
window dimensions, and window positions on the façade
must be specified. The orientation of beams (transverse or
longitudinal) and specifications for the subdivisions of the
windows and frame width are provided as optional
variables. Additionally, two window designs can be
specified. This was deemed necessary given previous
evaluations of classrooms, as some classrooms were
found to have more than one window type. For example,
the second window type can be used to model skylights,
or an additional door. The minimum and maximum
bounds for each variable can be easily redefined within
the slider editor (Figure 1). All measurements in the slider
values can be provided with an accuracy of 1 cm.
Figure 2: Excerpt of the GH script, highlighting the
complexity of the variables’ connections
Table 1: Required Design Variables
Design Category -
Required input
Design Variable
Minimum and
Maximum Bounds
Classroom
Classroom length
6 to 10 m
Classroom width
6 to 10 m
Classroom height
2.5 to 3.5 m
Window type
Window width
0.6 to 3.0m
Window height
0.6 to 2.5m
Windowsill
height
0.6 to 3.0m
Number of
windows
2 to 10
Distance wall to
first window
0.01 to 4.0 m
Distance between
windows
0.01 to 1.0 m
Ceiling grid
Panel geometry
Square (0.6m) or
rectangular (1.2 m)
Rear wall type
Exterior or
interior wall
0, 1 Boolean, 0 =
exterior, 1 = interior
Table 2: Optional Design Variables
Design Category -
Optional input
Design Variable
Minimum and
Maximum Bounds
Window
Number of
subdivisions
1 to 3
Width of first
subdivision
2 to 8
Width of second
subdivision
0.6 to 2.5m
Frame width
0.6 to 2.5m
Beam
Direction
0, 1 Boolean,
0 = transverse,
1 = longitudinal
Beam width
0.3 to 0.4 m
Beam thickness
0.3 to 0.4 m
Distance to wall
0 to 5 m
Mid-distance
between beams
5 to 10 m
Base-case design solution for AHU, acoustics, and
lighting
Before the generation of design plans for AHU, acoustics,
and lighting could be automated, a base-case solution had
to be designed. This base-case was then parameterised to
adapt to given classroom settings, and its components
were modularised accordingly.
A base-case solution was selected from plausible
scenarios for the refurbishment. For the base-case
solution, a ceiling-mounted decentralised AHU-unit was
positioned at the back of the classroom (Figure 3). A
ceiling-mounted solution was chosen, so that the AHU
would not take up wall space and floor area already in use
or needed for other purposes (e.g. for furniture, or pin-up
space). Additionally, this would reduce labour time that
would otherwise be needed to free up space for the
installation of the unit.
For acoustics, a suspended ceiling with modularised
panels was placed in a wide central strip, extending from
the AHU to the other end of the room. A central, as
opposed to a circumferential placement (Figure 4) of
acoustic panels was selected for several practical reasons.
For one, this would allow for easy integration of new
lighting systems with recessed luminaires, and invisible
cable routing. Importantly, it would also improve airflow
from the suspended AHU due to the Coandă effect
(Igarashi et al., 2019) and could therefore ensure a better
distribution of supply air throughout the room. Another
reason for the central positioning of the acoustic panels on
the ceiling was that it would provide a larger acoustically
effective area than the otherwise limited narrow strip on
the circumference. Lastly, in cases where side lights
would terminate closely below the ceiling, the window
would not be blocked by the suspended ceiling.
The installation of additional absorbers on a second
surface besides the ceiling is a recommended practice
(DIN18041:2016-03). However, the availability of wall
space will vary between classrooms and can therefore not
be accounted for. As such, it is suggested to install
additional freely positionable absorbers on rear or side
walls, as needed.
For lighting, a daylight harvesting system was selected to
reduce electric energy consumption. This was combined
with an occupancy sensor, to automate the turning off of
lights in unoccupied rooms, e.g. during break times.
Additionally, window-near, and -far sides were made
separately dimmable. The product list for procurement
therefore accommodates one daylight sensor, one
occupancy sensor, and a multifunctional control system
with up to four channels.
Figure 3: Central, suspended acoustic ceiling
Figure 4: Circumferential placement of acoustic panels
Automated design generation via rule-based
parameterisation and modularisation
In a next step, a parametric modelling system was
designed, and dependencies and constraints were
implemented to generate an integrated design solution for
ventilation, acoustics, and lighting. The modularisation
follows the hierarchy depicted in Figure 5, whereby the
placement of the ventilation unit is determined by the
room geometry, an acoustic ceiling grid is adjusted to the
room geometry and placement of the ventilation unit, and
luminaires are placed based on the acoustics ceiling grid.
This section outlines the implemented rules for the
parameterisation and modularisation of each product unit.
For the installation of the ceiling mounted AHU, if the
rear wall was specified as an exterior wall, a core drill hole
was specified behind the unit for outdoor and exhaust air.
If the rear was specified as an inner wall, the AHU unit
was placed at a 50 cm distance to the wall, which would
allow for the spacing required by ducts and insulation. In
this scenario, further rules were implemented to specify
the location of outdoor and exhaust air vents:
If a wall surface of 25cm width is available after the last
window, place the outdoor and exhaust air vents at the
lower and upper third of the side wall, respectively. Else,
if the distance between window edge and ceiling exceeds
25 cm and no beam has been specified, place the outdoor
and exhaust air vents above the upper edge of the window.
Place the vents at least 230 cm apart from each other.
Else, place the outdoor and exhaust air vents below the
windowsill at least 230 cm apart from each other.
As for the acoustics grid, suspended sound reflective
panels were placed with the following rules:
Extend a grid from the AHU unit to the front wall. Retract
the grid from the side walls by X 0.6x0.6 m modules,
where X describes the number of 0.6 module rows to be
deleted and is a variable defined by the following rules:
n = floor (((room width/0.6)-1) mod 3)
m = floor (((room width/0.6)-1) mod 4)
If m 0, X = 3 + n,
Else X = 4
New grid width Y = ((floor (room width/0.6))- X) * 0.6
For lighting, luminaires were placed in every third or
fourth panel, according to m and n. The rules are:
Where (Y-0.6) mod 3 = 0, place luminaires in every third
panel. In this case, the luminous flux is specified to 2800
lumen (lm). Else, place luminaires in every fourth panel.
In this case, the luminous flux is specified to 3800 lm.
For the luminaire distribution along the length of the
room, additional rules were established. These are:
Place the last column of luminaires no closer than one
panel distance from the front wall. If the distance between
the last column of luminaires exceeds 1.8 m, place the
ceiling-mounted linear wall washer within 0.7 distance
from the front wall.
These rules modularise the acoustic grid so that the
minimum number of complete panels are used across the
width of the room, therefore reducing the labour time
otherwise required for resizing the panels.
Model output
The developed GH script currently generates the design
plan, the count and dimensions of the required acoustic
panels, and the number of luminaires required to achieve
500 lux at work plane height and a uniformity of 0.6
within the room. Additionally, a machine-readable format
containing the product data is generated (based on
VDI3805-100), as shown in Figure 6.
Pilot Study
In spring and summer of 2019, the Heinz Trox
Wissenschafts gGmbH conducted one-day comfort
measurements in 48 classrooms of 23 schools in Aachen
Figure 5: Parametric hierarchy and component dependency
Figure 6: GH export of product data to VDI3805-excel template, then to machine readable CSV format
and Neukirchen-Vluyn (North-Rhine Westphalia,
Germany) to examine the status quo regarding air quality,
thermal comfort, room acoustics and illumination under
real-life conditions. Results indicated significant
shortcomings in all aspects: While all-year provision of
hygienically acceptable air quality seemed only possible
with mechanical ventilation units as opposed to mere
manual ventilation, room acoustic measurements revealed
long reverberation times, which impaired speech
intelligibility. Illumination measurements, too, showed
insufficient lighting (Burgholz and Müller, 2019, 2020).
Based on these results, a school building from the field
study was selected, and two classrooms, similar in their
layout, were refurbished. The rooms have a footprint of
62 m², a room volume of 204 m³, an east/north-east
orientation, and are located on the first floor. Both rooms
showed poor illumination and acoustic conditions and
therefore had great potential for improvement. Figure 7
shows the results of the horizontal illuminances measured
at work plane height over the study desks in one of the
two classrooms prior to the intervention. Lux levels were
far below the recommended minimum threshold of 300
lux, measured with electric lighting turned on. A mean
reverberation time of around 0.9 s was measured for
frequencies between 250 and 2000 Hz in the unoccupied
room. This exceeds the recommended reverberation time
of around 0.5 s for classrooms (DIN18041:2016-03). The
developed and presented tool was applied to remedy these
problems in the two rooms.
Figure 7: Lux measurements taken above student desks
(with electric lighting turned on)
Planning, procurement, and work schedule
The ceiling plan of the implemented design for the AHU,
acoustic ceiling, and lighting are shown in Figure 8.
Images of the completed projects are shown in Figure 9.
Ventilation units were installed on the ceilings, centred on
the rear wall. In both rooms, the rear wall was also the
exterior wall, and therefore enabled a direct duct routing
to the outside.
Figure 8: Ceiling plan with AHU (1), recessed luminaires
(2), acoustic panels (3), and optional ceiling mounted
LED wall washers (4)
The developed tool allows for the extraction of the
previously described product data into a machine-
readable and manufacturer independent record. This
record constitutes the collection of the alphanumerical
description of building components required for the same
or similar refurbishment projects. The tool currently
serves as a proof of concept for the potential automation
of interdisciplinary product planning and procurement.
However, for actual automation of the procurement
process, an appropriate system needs to be developed on
the side of manufacturers, in order to translate the
specified data records into a product package order.
The refurbishments of the two rooms in the pilot study
were carried out during school holidays in autumn 2020
and took roughly 4.5 days per room. Core drillings,
installation of the ventilation units, and installation of the
acoustic ceiling including lighting were carried out
successively by three different firms. It is worth
mentioning that the installation of recessed luminaires
was completed in approximately one hour. In comparison,
the mounted ceiling luminaires took nearly an entire day
due to the necessary reinforcement of the acoustic panels
and respective fastening.
Based on the experience from the pilot study, an
optimised work schedule could be reduced to about 3 days
per room, provided that the air ducts can be routed directly
through the rear wall. The first day would be reserved for
the core drillings and installation of the ventilation unit.
On the second day, the acoustic ceiling, including side
cladding could be installed, while in parallel, the
ventilation unit would be integrated into the heating
circuit. On the third day, commissioning, electrical
connection of remaining luminaires, potential painting
work, and cleaning would take place. If the measures are
to be carried out on a larger scale, a further reduction in
working time is conceivable due to greater flexibility and
parallelism of necessary work steps.
Figure 9: Photographs of the completed project
Conclusions and Future Work
The present work was aimed at facilitating interventions
improving indoor air quality, acoustics, and lighting
through processes of parametric modelling and
modularisation. First, a parametric model was developed
to design any typical classroom configuration via simple
slider adjustments. Second, parametric rules were
implemented to automate the generation of solutions for
the layout and distribution of a ventilation unit, acoustic
panels, and lighting. Building components related to these
three trades were then formulated as a new product unit
and modularised to facilitate assembly and installation.
Lastly, the developed script was implemented to assist
with the refurbishment of two classrooms.
The parametric model was developed in Grasshopper with
16 required and 9 optional input variables to reconstruct
typical classroom configurations through simple slider
adjustments, therefore providing ease-of-use for planners
as long as they have access to licenses for the required
base software. The rules imposed to generate solutions are
based on availability of spaces, structural constraints, cost
efficiency (e.g. via modularisation), and lighting
requirements. The modularisation of all components,
including AHU, acoustic panels, and lighting, ensured
that clashes between components and with building
structure could be avoided, thereby reducing interface
problems.
The practical application of the script on two
refurbishment projects allowed for the automated
generation of ceiling plans and extraction of product data.
Additionally, through modularisation, refurbishment
projects of similar size are expected to take three days,
thus hardly interfering with school operation.
Modularisation of the acoustic ceiling and the use of
recessed luminaires enabled an especially time-efficient
installation compared to the installation of mounted
ceiling luminaires. Nevertheless, it must be emphasised
that in both refurbished classrooms, the rear wall was an
exterior wall, and therefore an easy scenario for the
installation of an AHU, as air ducts could be directly
routed to the outside. As this will however only apply to
corner rooms, a more elaborate and extensive routing of
ducts may become necessary in other projects.
The rule-based implementation of the developed tool
relies on the simplification of options for the positioning
of the decentralised AHU with integrated supply and
extract air terminal. In that regard, future work could
extend the capabilities of the tool by including rules for
centralised HVAC units, and incorporating a feed-back
loop from simulations to optimise the positioning of
supply and extract air terminals considering draught risk
and thermal comfort.
In terms of facilitating procurement, a modularisation
approach was used to create a product package CSV in
accordance with VDI 3805-100. This product package
integrates certain parameters from the Rhino GH model to
describe all MEP trades involved, potentially enabling the
planning and purchase of the presented module via the use
of a common MEP platform.
The VDI 3805 guidelines are currently used as a basis for
the development of the international ISO 16757:2017-04
standard, which will employ ISO 16739 -Industry
Foundation Classes (IFC) for data sharing in the
construction and facility management industries as a
framework for the allocation of product parameters to the
respective components of a product package (Hauer et al.,
2020). MEP product catalogues and import/export
interfaces are likely to be standardised accordingly in
future. Thus, the currently presented CSV dataset is a
proof of concept. Its practical usage is subject to the
ongoing development of norms, data standards, and the
acceptance thereof in the international planning and
manufacturing community.
The Rhino GH script that was developed for the project is
available as an open-source model under the MIT license
on Github (https://github.com/RWTH-E3D/AHU_
acoustic _lighting-Planner).
Acknowledgements
We gratefully acknowledge Heinz Trox Wissenschafts
gGmbH and thank them for their financial support.
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Product architecture is the scheme by which the function of a product is allocated to physical components. This paper further defines product architecture, provides a typology of product architectures, and articulates the potential linkages between the architecture of the product and five areas of managerial importance: (1) product change; (2) product variety; (3) component standardization; (4) product performance; and (5) product development management. The paper is conceptual and foundational, synthesizing fragments from several different disciplines, including software engineering, design theory, operations management and product development management. The paper is intended to raise awareness of the far-reaching implications of the architecture of the product, to create a vocabulary for discussing and addressing the decisions and issues that are linked to product architecture, and to identify and discuss specific trade-offs associated with the choice of a product architecture.
A feature based parametric design program and expert system for design
  • H Basak
  • M Güselin
Basak, H. and Güselin, M. (2004) 'A feature based parametric design program and expert system for design', Mathematical and Computational Applications, 9(3), pp. 359-370.
Wärme, Luft und Akustik in Unterrichtsräumen -Ergebnisse einer Feldstudie in Nordrhein-Westfalen, 6. Zukunftsraum Schule'. Edited by Fraunhofer-Institut für Bauphysik IBP
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Burgholz, T. M. and Müller, D. (2019) 'Wärme, Luft und Akustik in Unterrichtsräumen -Ergebnisse einer Feldstudie in Nordrhein-Westfalen, 6. Zukunftsraum Schule'. Edited by Fraunhofer-Institut für Bauphysik IBP. Available at: https://www.zukunftsraumschule.de/pdf/kongress-2019/VRfL/112_VRfL_BURGHOLZ_PW.pdf (Accessed: 31 January 2021).
CO2 levels in differently ventilated classrooms with regard to occupational ventilation behavior under spring and summer conditions
  • T M Burgholz
  • D Müller
Burgholz, T. M. and Müller, D. (2020) 'CO2 levels in differently ventilated classrooms with regard to occupational ventilation behavior under spring and summer conditions', in ISIAQ, 16th Conference of the International Society of Indoor Air Quality & Climate, Indoor Air 2020, pp. 1176-1181. Available at: http://www.indoorair2020.org/data/IA2020_papers.p df (Accessed: 31 January 2021).