D. BE^KOVSKÝ et al.: COMPUTER TOOLS TO DETERMINE PHYSICAL PARAMETERS IN WOODEN HOUSES
607–610
COMPUTER TOOLS TO DETERMINE PHYSICAL PARAMETERS
IN WOODEN HOUSES
DOLO^ANJE FIZIKALNIH PARAMETROV Z RA^UNALNI[KIMI
ORODJI V LESENIH HI[AH
David Be~kovský, Franti{ek Vajkay, Vladimír Tichomirov
Brno University of Technology, Faculty of Civil Engineering, Institute of Building Structures, Veveøí 95, 602 00 Brno, Czech Republic
beckovsky.d@fce.vutbr.cz
Prejem rokopisa – received: 2013-10-01; sprejem za objavo – accepted for publication: 2015-06-30
doi:10.17222/mit.2013.213
Nowadays, because the number of wooden houses gradually increases and due to European regulations, a huge emphasis is put
onto the aspects like energy saving and energy efficiency in family housing, which are the topic of a related ongoing research
project. Hence, the paper is focused on comparing and streamlining the methods available to the engineering community in the
fields of energy consumption and air-tightness measurements of buildings. The newly developed design methodologies and
practical outputs of the completed research project are planned to be delivered directly to the related industry. The research
project is also focused on the humidity and temperature control in wooden houses since wooden houses consist of timber
structural elements, whose humidity and moisture may later cause some liability-related problems. To prevent these failures, it is
necessary to investigate the quality of tools and methodologies, through which one might determine the values of humidity and
temperature already within the design phase. Nevertheless, design is only one phase of the whole process; the other is the
building-realisation phase. Therefore, the questions to answer are: Who is actually responsible for the failures caused by
humidity and moisture? When does the water actually penetrate the structural elements? Is it in the factory or when the elements
are transported or when the products are stored at the construction site?
Keywords: moisture, wooden constructions, timber structures, energy consumption, Arduino, Raspberry Pi
Dandanes se zaradi nara{~anja {tevila lesenih hi{ in tudi zaradi evropske regulative posve~a veliko pozornosti prihrankom pri
energiji in energijski u~inkovitosti dru`inskih hi{, kar je tudi predmet predstavitve. ^lanek je usmerjen na primerjavo in
usmeritev metod, s katerimi razpolaga in`eniring na podro~ju porabe energije in meritev zrakotesnosti zgradb. Novo razvite
metodologije na~rtovanja in prakti~ne re{itve iz raziskovalnih projektov bodo neposredno posredovane industriji. Raziskovalni
projekt je usmerjen na kontrolo temperature in vlage v lesenih hi{ah, ker so lesene hi{e zgrajene iz lesenih strukturnih
elementov pri katerih lahko vlaga povzro~i problem z zdr`ljivostjo. Za prepre~evanje takih po{kodb je potrebno preiskovati
kvaliteto orodij in metodologij, s katerimi je mogo~e oceniti vsebnost tako vlage kot temperature, in sicer `e v sami fazi
na~rtovanja. Na~rtovanje je samo ena od faz celotnega procesa, druga pa je faza gradbene realizacije. Vpra{anje na katerega je
potrebno odgovoriti je: kdo je v resnici odgovoren za po{kodbe, ki jih povzro~i vlaga in tudi kdaj voda v resnici penetrira v
gradbene elemente? Je to `e v tovarni, med transportom ali pa med shranjevanjem elementov na gradbi{~u?
Klju~ne besede: vlaga, lesena konstrukcija, leseni gradbeni elementi, poraba energije, elektronska platforma Arduino, Raspberry
Pi
1 INTRODUCTION
In the building industry, there are several variants of
wooden houses. There are log-wood houses, wooden-
frame ones, wooden houses built from cross-laminated
timber panels, etc. Nevertheless, the design procedure
for wooden houses is the same as that for brickwork
buildings and, among other measures, it must include a
thorough thermal analysis1 since the durability and
functionality of modern wooden structures depend on the
humidity and moisture control. In the case of wooden
houses, it is crucial to avoid condensation of water va-
pour in the building envelope. This affects the thermo-
technical requirements given to designed structures,
especially those of wall and roof cladding. The design of
peripheral wall and roof cladding must also properly
solve all the details, including the quality of designed
materials.
However, even if the design incorporates all the
design principles, there is still no guarantee that the
designed structures are going to function properly when
built under real-life conditions because some failures
might appear during the building erection process. That
is why construction works have to be regularly inspected
by the construction inspector and the technical super-
visor of the investor.
Supervision and monitoring throughout the construc-
tion process ensure the highest quality of the provided
services and reduce the formation of defects, primarily
when structural materials and elements are built in, since
the initial water content can cause some problems as
well. The initial water content should be checked and
compared to the numbers contained in the "Technical
Data Sheets" published by the manufacturers.
Materiali in tehnologije / Materials and technology 50 (2016) 4, 607–610 607
UDK 676.064:67.017:004.42 ISSN 1580-2949
Professional article/Strokovni ~lanek MTAEC9, 50(4)607(2016)
2 CONTAMINATION DURING THE EXECUTION
The issue of the initial mass moisture is demonstrated
by T. Kalábová et al.2 on mineral-fibre thermal-insulation
panes, which were built into the timber joist ceilings of
the EXDR1 experimental wooden house.
Within the discussed timber joist ceilings, the space
between the joists is completely filled with mineral-fibre
thermal-insulation boards. The built-in boards were
delivered under rainy-weather conditions in summertime
and were left outside to ventilate for a period of 14 days
before they were unpacked and used.
Although the building material was delivered in its
original packaging in shrink-wrap foils, some of the mi-
neral-fibre boards had a significant amount of moisture
content.
The moisture inside was verified with an infrared
imaging camera after positioning the first layers of the
thermally insulating mineral-fibre boards. Hot spots of
moisture content above 70 % were localized at several
locations (Figure 1).
With an infrared imaging camera, it is possible to:
• Determine the distribution of the surface temperature
over the envelope or the distribution of the apparent
radiant temperature;
• Determine the distribution of the atypical surface
temperature, i.e., the temperature changes caused by
some disorders such as the moisture content,
insulation, or penetration of air;
• Assess the type and extent of the problem.
To determine whether the observed changes were
atypical or not, the obtained thermographs were com-
pared to the expected distributions of surface tempera-
tures determined experimentally under the same boun-
dary conditions in the form of building-shell variables.
The estimated temperature distributions can be deter-
mined either from reference thermographs, with
calculations or surveys as another possibility.
2.1 Sensing devices – a thermal imager
To take infrared images, it is necessary to fulfil one
condition, which is a large temperature difference bet-
ween the inside and the outside of an envelope. The
temperature difference must be big enough to allow the
detection of thermal irregularities. The test cannot be
conducted if the external or internal temperature varies
considerably or if the structure is exposed to direct sun-
light.
3 MOISTURE PREVENTION
One way to prevent the incorporation of moisture in
wood-based materials susceptible to higher levels of
humidity is a control mechanism and a procedure, such
as the usage of stick hygrometers or infrared imaging
cameras.
An application of wet materials in the course of the
construction process can lead to a rapid appearance and
development of wood-decaying organisms, which are
very difficult and expensive to dispose of. One way for
the disposal of wood-decaying organisms is to use mi-
crowave radiation,3 where electromagnetic waves
oscillate at frequencies of 300 MHz to 300 GHz. These
frequencies correspond to wavelengths of 1 m to 1 mm.
The microwave generator is completely safe to use if
treated with care. Health issues can arise only due to a
long-term direct exposure from a close distance.
4 MONITORING DURING THE LIFE CYCLE
The monitoring of the physical parameters of the
structures and internal environment of buildings brings
significant investment costs as a large number of various
sensors and data loggers are required to make such a
monitoring possible. Due to individual requirements of
research teams and the restlessness of developers of
computing hardware and information technologies, the
authors of the article (themselves researchers in the field
of building physics) came up with an idea and decided to
build a custom data logger with a high variability of
connectable parts and sensors. The whole process is
based on do-it-yourself prototyping. The data logger is
made of two prototyping boards, which are cheap and
relatively easy to use. Using ArduPi, it consists of a
D. BE^KOVSKÝ et al.: COMPUTER TOOLS TO DETERMINE PHYSICAL PARAMETERS IN WOODEN HOUSES
608 Materiali in tehnologije / Materials and technology 50 (2016) 4, 607–610
Figure 2: Thermal conductivities of different thermally insulating
materials under varying moisture content
Slika 2: Toplotna prevodnost razli~nih materialov za toplotno
izolacijo, pri razli~nih vsebnostih vlage
Figure 1: Moisture in the ceiling structure
Slika 1: Vlaga v konstrukciji stropa
credit-card-sized ARM-processor-based Raspberry Pi
model B and an open-source microcontroller board
Arduino (the correct description of the board is Arduino
Mega 2560).
The boards can communicate via USB (universal
serial bus), I2C (inter-integrated circuit communications)
or SPI (serial peripheral interface) interfaces.4 A real-
time clock module can be coupled to them as well as any
of the available sensors. Thus, even after a power outage,
the system is able to resume the task given to it.
4.1 Reasoning behind the choice of the boards
Both boards, the Raspberry Pi and the Arduino, were
chosen because they can be programmed for different
purposes. Both of them have a huge number of GPIO
(general-purpose input/output) headers starting with
USB ports and ending with analogue voltage input pins.
The boards can communicate throughout the by-direc-
tional I2C communication protocol.5 To avoid data and
speed losses, it is recommended to use a shielded cable
between the two boards. Nonetheless, a by-directional
voltage divider is a requirement for the I2C communi-
cation. The Raspberry Pi I2C interface works at 3.3 V,
while the Arduino interface works at 5 V.
The Raspberry Pi is cheap and the first of its kind.
The ARM processor with a clock speed of 700 MHz can
run different processes. Thus, the Raspberry Pi can be
used as a PC with Raspbian OS (a modification of De-
bian Linux OS) running on it. It can be hooked up with a
keyboard, a mouse and a display and can run a web and
SQL server as well as displaying data. With Python6,7
scripting possibilities, it is suited to be used as the brain
of the ArduPi.
Even though it would be possible to operate most of
the sensors (1-Wire, I2C, SPI) with the Raspberry Pi, the
Arduino board can do it better. Arduino boards have a
10-bit internal ADC (analogue-to-digital converter).
Analogue sensors for the measurement of relative humi-
dity, like the Honeywell HIH-4031, output electricity in
place of digital data. Such readings need to be converted.
One could use ADC integrated circuits instead of an
Arduino board. Nonetheless, Arduino is preferred
because it can be easily programmed in the bundled IDE
(Integrated Development Environment).8
4.2 Used sensors
When researching an indoor environment, we need to
have a relatively large number of sensors: some thermal
couples, relative-humidity sensors and others. The sen-
sors that can be obtained for a reasonable price are pro-
duced by companies like Honeywell, Dallas Instruments,
Panasonic and may be digital or analogue. Just to men-
tion, the prototype of ArduPi utilizes the already men-
tioned analogue humidity sensors HIH-4031 (Figure 4)
by Honeywell.
D. BE^KOVSKÝ et al.: COMPUTER TOOLS TO DETERMINE PHYSICAL PARAMETERS IN WOODEN HOUSES
Materiali in tehnologije / Materials and technology 50 (2016) 4, 607–610 609
Figure 4: Close-up view of the HIH-4031 sensor
Slika 4: Podrobnej{i pogled na HIH-4031 senzor
Figure 3: I2C data line between Raspberry Pi, RTC module and
Arduino board
Slika 3: I2C podatkovna linija med Raspberry Pi, RTC modulom in
Arduino platformo
Figure 5: Close-up view of HIH-613X products
Slika 5: Podrobnej{i pogled na HIH-613X proizvode
To free up the analogue input pins on the Arduino
board for different sensors, the usage of combined digital
sensors HIH 6131-021 is planned (Figure 5). These sen-
sors are also made by Honeywell.
These sensors communicate via the already men-
tioned I2C communication protocol.
Energy-consumption sensors are important for moni-
toring an internal environment as, in the case of a power
failure, they immediately record the time without elec-
tricity. Information about such conditions can be in-
stantly delivered by GPRS or EDGE.
Analogue pins for mFi-CS sensors are available from
Ubiquiti Networks and used for monitoring the energy
consumption of home appliances and many others.
5 CONCLUSIONS
With the modern technologies and materials avail-
able, it is possible to put together small and cheap data
loggers for experimental purposes to be used in building
physics instead of the ones produced by one of the major
companies. Data loggers may be customized to the needs
of the user, including the software base for the operation.
The choice of sensors and measuring equipment depends
solely on the user. Whether the sensors hooked up are
going to have an accuracy of 0.5 % or 5 % depends only
on the available funds. The only requirement is their
compatibility to any of the supported communication
protocols. It can be said that the creation of BRESET on
an ArduPi base is a major step as it brings the possibi-
lities of research activities closer to the scientific
community.
Acknowledgement
This paper was completed under project
no. LO1408 "AdMaS UP – Advanced Materials, Struc-
tures and Technologies", supported by the Ministry of
Education, Youth and Sports under the National Sustain-
ability Programme I and under the Project
FAST-S-15-2757 supported by Ministry of Education,
Youth and Sports under "Specific University Research".
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D. BE^KOVSKÝ et al.: COMPUTER TOOLS TO DETERMINE PHYSICAL PARAMETERS IN WOODEN HOUSES
610 Materiali in tehnologije / Materials and technology 50 (2016) 4, 607–610