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Energy and Buildings 70 (2014) 422–426
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Energy and Buildings
journal homepage: www.elsevier.com/locate/enbuild
Short Communication
Comparison of thermal transfer characteristics of wood ﬂooring
according to the installation method
Jungki Seo a , Yoon Park a,b , Junhyun Kim a , Sughwan Kim a , Sumin Kim a,∗ , Jeong Tai Kim c
a
b
c
Building Environment & Materials Lab, School of Architecture, Soongsil University, Seoul 156-743, Republic of Korea
Dongwha Nature Flooring Co. Ltd. , Incheon 404-810, Republic of Korea
Department of Architectural Engineering, Kyung Hee University, Yongin 446-701, Republic of Korea
a r t i c l e
i n f o
Article history:
Received 13 September 2013
Received in revised form
23 November 2013
Accepted 28 November 2013
Keywords:
Wood ﬂooring
Thermal transfer characteristics
Laminate ﬂooring
Engineered ﬂooring
Installation method
Ondol
a b s t r a c t
There are two types of installation methods for wood ﬂooring; a ﬂoating installation method for laminate
ﬂooring, and an adhesive installation method for engineered ﬂooring. Thermal transfer characteristics
from the ﬂoorings show a signiﬁcant difference depending on the installation method, so this study
focused on the comparative thermal transfer characteristics by preparing mock-up scale. The laminate
ﬂooring and the modiﬁed engineered ﬂooring of the Korean Standard were used to conduct the tests.
The tests were set up in two rooms in an apartment in Seoul, and a water heat source was prepared at
45 ◦ C and 75 ◦ C. As a result, the velocity of thermal transfer of the modiﬁed engineered ﬂooring using
adhesive was faster than that of the laminate ﬂooring. There was no difference of temperature between
both samples at 45 ◦ C of water supply, but a great difference was shown at 75 ◦ C. Moreover, installing
the modiﬁed PE foam helped the ﬂoating installation method to develop a thermal transfer performance
comparable to that of the preceding research.
© 2013 Published by Elsevier B.V.
1. Introduction
Recent reports by the Inter-governmental Panel on Climate
Change (IPCC) have raised public awareness of energy use and its
environmental implications, and have generated a great deal of
interest in gaining a better understanding of the characteristics
of energy use in buildings, especially their correlations with the
prevailing weather conditions. The supreme importance of awareness requires for undivided responses at national, regional and
global levels [1–5]. In 2002, buildings worldwide were estimated
to account for about 3% of global greenhouse gas emissions [6]. In
their work on climate change and comfort standards, Kwok and
Rajkovich reported that the building sector accounted for 38.9%
of the total primary energy requirements in the United States, of
which 34.8% was used for heating, ventilation and air-conditioning
[7].
In Korea, 97% of energy resources are imported. The Korean
growth rate of greenhouse gas emission per capita was the highest in the world during 1990–2004. Moreover, 83% of the domestic
greenhouse gas emissions stemmed from energy use in the year
2004. Korea belongs to the second group of nations that require
mandatory reduction of greenhouse gas emissions, starting in
2013. Therefore, Korea is working particularly hard to prepare
∗ Corresponding author. Tel.: +82 2 820 0665; fax: +82 2 816 3354.
E-mail address: skim@ssu.ac.kr (S. Kim).
0378-7788/$ – see front matter © 2013 Published by Elsevier B.V.
http://dx.doi.org/10.1016/j.enbuild.2013.11.085
for national measures to reduce energy consumption, and limit
carbon dioxide emissions in the construction industry, which is
responsible for over 40% of all carbon dioxide production. In order
to pursue sustainability in the construction industry, the existing
development-focused construction activities must be transformed
via a new paradigm that focuses on sustainable development,
through the adoption of sustainable policies by the government,
and the development and dissemination of sustainable construction technologies [8–10].
The radiant ﬂoor heating system (Ondol) has conventionally
been used in Korea. For ﬂoor heating, heat is usually supplied from
boilers installed inside each apartment [11]. Hot water from a boiler
is piped to a ﬂoor coil, which is an X-L pipe underneath the ﬂoor surface. The thermal storage mass consists of cement mortar, which
replaces the traditional stone slab [12–14]. Residents spend a lot
of their time sitting on ﬂoors; therefore, the ﬂooring materials
used should be thermo-physically comfortable [15,16]. The control
of water-based ﬂoor heating systems is usually divided into two
parts: a central control, which considers the external conditions,
and individual room control [17].
Park et al. researched the click proﬁle of laminate ﬂooring, by
comparison of click and bonding laminate ﬂoorings, especially the
base of the click proﬁle shape, bonding strength and international
patents. A non-glue locking system has been used since laminate
ﬂooring was developed. For environmental reasons, and to save
installation time, manufacturers in Europe and the USA have developed a click proﬁle for laminate ﬂooring. In the past, PVC ﬂooring
J. Seo et al. / Energy and Buildings 70 (2014) 422–426
423
Fig. 1. Installation method of laminate ﬂooring and engineered ﬂooring.
was the main product, but the number of wood ﬂoorings in use is
increasing as national income rises, and environmental products
have attracted attention. However, these current trends have led
to an increase in the thickness of ﬂooring materials, PVC to wood
ﬂooring, so that heat losses have also increased, because of the low
thermal conductivity of wood. With problems, many researches
focus on the thermal transfer characteristics of wood ﬂooring, especially on laminate ﬂooring and engineered ﬂooring, which are the
most widely used products in the ﬂooring market in Korea. Laminate ﬂooring is installed by a ﬂoating installation method, with
polyethylene (PE) vinyl and polyethylene (PE) foam to make the
ﬂoor even. Due to the installation method, a click proﬁle type, there
is no possibility of emitting pollutant caused by resin, so that this
ﬂooring can offer a comfortable indoor air quality. However, heat
losses can occur between the connection gaps; besides, PE foams
have many pores to block the upward heat ﬂow, and that is also one
of the reasons to cause heat loss. In the case of engineered ﬂooring, resins are used to ﬁx the ﬂooring on the ﬁnishing mortar, so
this ﬂoor system can have high thermal conductivity, because of its
adhesive type. However, the thermal conductivity of this ﬂooring is
lower than that of laminate ﬂooring [18]. Thermal conductivity and
thermal transfer characteristics of a variety of wood ﬂoorings were
considered above. In this study, the thermal transfer characteristics
of laminate ﬂooring and modiﬁed engineered ﬂooring in the actual
living space was compared. The thermal transfer characteristics of
the modiﬁed underlay foam with the laminate ﬂooring were also
determined.
2. Experimental
2.1. Materials
In this research, adhesive installation method and ﬂoating
installation method were installed to determine thermal transfer characteristics of those. First type, the ﬂoating method, was
constructed with this layer; PE vinyl, modiﬁed underlay-foam,
and laminate ﬂooring. The modiﬁed underlay-foam has a punched
hole, which results in improvement of heat transfer rate from
a heat source. Second type, adhesive installation method, used
a water-borne epoxy adhesive to install modiﬁed engineered
ﬂooring. The modiﬁed engineered ﬂooring is a ﬂooring to have
melamine ﬁlm on the surface to increase the surface strength of
it. Fig. 1 presents the two installation methods. Each of ﬂooring
has a dimension with 7.5 mm × 75 mm × 900 mm of the laminate
ﬂooring and 7.5 mm × 190 mm × 1200 mm of modiﬁed engineered
ﬂooring, which meet Korean standard.
2.2. Methods
2.2.1. Test in actual living place
This test was performed in two rooms of the same size, located
in Seoul, Republic of Korea. Room 2 and Room 3 were the test
objects in Fig. 2. To minimize outside inﬂuences, every side of the
rooms was constructed to be airtight. The laminate ﬂooring was
constructed by a ﬂoating installation method on the PE vinyl and the
Fig. 2. Test plan.
modiﬁed underlay foam, and the engineered ﬂooring was installed
by an adhesive installation method, after spreading adhesive on
the mortar ﬂoor, and then allowing time to cure the adhesive. The
supplying heat temperature of water was 45 ◦ C, and the temperature variation was measured two times with a time schedule, of
heating for 4 h and turning off the heating for 4 h. Fig. 3 shows the
measuring temperature points. The temperature on the ﬂooring
was monitored at ﬁve points, and one point for the indoor temperature 1 m above the ﬂooring. Test was carried out with a six
times cycling. Three times tests of the six cycling were measured
in the condition that the modiﬁed engineered ﬂooring, as an adhesive type, was installed in Room 2, and the laminate ﬂooring, as
an assembly type, was done in Room 3, and the other three times
tests were vice versa to minimized the test error. Table 1 presents
a summary of the experiment.
2.2.2. Mock-up test
Equal tests were carried out by thermal environment performance evaluation module in Korea Conformity Laboratories (KCL),
to take accurate measurements, and to conﬁrm any errors caused
by ambient conditions and the location of rooms in the preceding tests in an actual living place. The same speciﬁcation samples
were used, and two modules made with standard ﬂooring structure were installed. The thermal sensors were set at three points
on the surface of the ﬁnishing mortar, three points on the surface
of the ﬂooring, and one point in the air. The condition of the test
room was constantly kept at 20 ◦ C temperature and 50% relative
humidity. The module size was 2 m × 2 m × 1.2 m. In addition, the
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J. Seo et al. / Energy and Buildings 70 (2014) 422–426
Fig. 3. Measuring temperature in actual living space (a) laminate ﬂooring and (b) engineered ﬂooring.
Table 1
Summary of the experiment.
Installation method
Floating installation
Adhesive installation
Flooring type
Subsidiary materials
Installation size
Sampling point
Sampling intervals
Laminate ﬂooring
Modiﬁed PE-foam, PE-vinyl
3000 mm × 2700 mm
Surface 5 point, indoor 5 point
10 min
Modiﬁed engineered ﬂooring
Water-borne epoxy adhesive
3000 mm × 2700 mm
Surface 5 point, indoor 5 point
10 min
3. Results and discussion
3.1. Test in actual living place
Test results are presented in Fig. 6. The variations of the surface temperature of the ﬂooring and the indoor temperature during
heating time were similar, but this result indicated that the thermal transfer performance of the laminate ﬂooring with modiﬁed
underlay foam was signiﬁcantly improved, comparing to the existing PE-foam [18]. Similar test results were measured by the six
times cycling. The room where the modiﬁed engineered ﬂooring
was constructed had a 0.2 ◦ C higher room-temperature, and the
surface of the ﬂooring kept a slightly higher temperature. Therefore,
there was no remarkable difference in thermal transfer performance between the laminate ﬂooring and engineered ﬂooring.
Fig. 4. Thermal transfer characteristics test in mock-up lab.
supplying heating source temperatures of water were 45 ◦ C, which
is the temperature of a district heating type, and 75 ◦ C, which is that
of an individual heating type. The time schedule was planned with
heating for 4 h, and turning off the heating for 4 h, giving 8 h of test
time. Figs. 4 and 5 show the test room, and a structure diagram of
the module system.
Fig. 5. Structure diagram of module system.
3.2. Mock-up test
3.2.1. Thermal transfer performance at 45 ◦ C of heating supply
source
Figs. 7 and 8 show the test conducted in the mock-up lab in
KCL. At 45 ◦ C, which is the supply temperature of a district heating type, the surface temperature of the ﬁnishing mortar increased
quickly, which led the surface temperature of the engineered ﬂooring to quickly increase. This is because the thermal conductivity
of the resin used to install engineered ﬂooring is far higher than
that of the components of the laminate ﬂooring, and the resins
were thinly and thoroughly spread on the ﬁnishing mortar. The
engineered ﬂooring exhibited better thermal transfer performance
than that of the laminate ﬂooring, technically showing about 2 ◦ C
difference of temperature, particularly at the beginning time. Furthermore, the air temperature of the engineered ﬂooring is higher
than that of the laminate ﬂooring, but not as much as the surface
temperature, because the thermal sensor for air temperature was
not inﬂuenced by radiant heating energy, but only air temperature.
It takes a long time for air to heat up, because of the high speciﬁc
heat of air, which means that there is no signiﬁcant temperature
variation at the low temperature of the heat source. However, after
heating off, the temperature of the engineered ﬂooring dropped
sharply; on the other hand, that of the laminate ﬂooring decreased
gradually, due to the heat storage capacity of the underlay foam
under the ﬂooring.
J. Seo et al. / Energy and Buildings 70 (2014) 422–426
Fig. 6. Thermal transfer performances in actual living place.
Fig. 7. Thermal transfer performance at 45 ◦ C of heating supply source by water.
Fig. 8. Thermal transfer performance at 75 ◦ C of heating supply source by water.
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J. Seo et al. / Energy and Buildings 70 (2014) 422–426
3.2.2. Thermal transfer performance at 75 ◦ C of heating supply
source
At 75 ◦ C, which is the temperature of an individual heating
type, similar temperature variations and heat storage capacity were
presented. However, as the heating supply source temperature
increased, temperature changes were distinguishably observed,
and the surface temperature of ﬁnishing mortar of the engineered
ﬂooring remained 0.5–2 ◦ C higher than that of the laminate ﬂooring
for a heating period, but the laminate ﬂooring could not reach the
peak temperature for 4 h. The results indicate that differences in the
thermal conductivity of the resin for the engineered ﬂooring, and
the PE-foam for the laminate ﬂooring, brought out the difference
of thermal transfer performance.
4. Conclusions
This research determined the thermal transfer characteristic
according to the ﬂooring installation methods and materials, by
tests in the actual living place, and in a mock-up module lab. The test
results show that the thermal transfer performance of the modiﬁed
underlay foam for the laminate ﬂoor showed better thermal transfer characteristics than the existing PE-foam. Moreover, when both
of the ﬂoorings were installed in an actual living place, no considerable difference of thermal transfer performance was found between
the laminate ﬂooring and modiﬁed engineered ﬂooring. However,
thermal transfer characteristic of the modiﬁed engineered ﬂoor was
slightly higher than the laminate ﬂoor as the preceding research
[18]. Lastly, when the temperature of the heating supply source
increased, temperature variations were clearly observed, which
made the air temperature remain high.
Acknowledgements
This work was supported by the National Research Foundation
of Korea (NRF) grant funded by the Korea Government (MSIP) (No.
2008-0061908).
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