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ScienceDirect Procedia Engineering 117 (2015) 191 – 196

International Scientific Conference Urban Civil Engineering and Municipal Facilities, SPbUCEMF-2015

Evaluation of Thermal Performance of Residential Building Envelope Sergey Korniyenko* Volgograd State University of Architecture and Civil Engineering, Akademicheskaya st. 1, 400074, Volgograd, Russia

Abstract The paper describes an evaluation of thermal performance of residential building envelope. Basing on the visual-andinstrumental inspection the conclusion on the non-compliance of the stated object with the requirements of the design and normative documentation was drawn. The thermovision control allowed revealing latent defects of the buildings envelopes and outlining the ways of their elimination. The numerical modeling of heat transfer made it possible to reasonably develop suggestions aimed at enhancing the thermal performance of buildings envelope elements. The integrated application of these methods gave an opportunity to determine the thermotechnical state of the object in whole. The results of the study serve as a basis for the development of methodological foundations for design, construction, operation and reconstruction of energyefficient buildings © 2015The TheAuthors. Authors. Published by Elsevier Ltd. © 2015 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of SPbUCEMF-2015. Peer-review under responsibility of the organizing committee of SPbUCEMF-2015

Keywords: Buildings thermal performance, visual-and-instrumental inspection, thermovision control, numerical modeling, thermotechnical defect.

1. Introduction Building thermal performance enhancement is a topical issue of construction and architecture. The evaluation of building thermal performance can be carried out in various ways [1—20]. Visual-and-instrumental inspection is widely used to determine general thermotechnical state of buildings [2, 7, 8, 15]. It allows determining the

* Corresponding author. Tel.: +7 (8 442) 97-48-72; fax: +7 (8 442) 97-49-33 E-mail address: [email protected]

1877-7058 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of SPbUCEMF-2015

doi:10.1016/j.proeng.2015.08.140

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Sergey Korniyenko / Procedia Engineering 117 (2015) 191 – 196

parameters deviation in the object under inspection against the requirements of the design and normative documentation and revealing evident defects. Latent defects of building envelope can be revealed through modern non-destructive methods of thermovision control [8, 10, 14, 16, 17, 20]. The calculated evaluation of thermotechnical indices of building envelope basing on numerical modeling makes it possible to outline the ways of building thermal performance enhancement [5, 9, 10—13, 18, 19]. An integrated application of these methods is necessary in order to determine the thermal performance characteristics of an object in whole. Hence, the topicality of the given issue is evident. 2. Object and methods Three multi-family residential buildings of the same type located in the Volgograd region are the object of the investigation [8]. Each building under investigation has 3 floors, 2 sections, 36 flats, crawl space and framed roof. The structural system of the buildings is a framed one of pre-fabricated reinforced concrete columns and floors. The external walls are non-bearing made of aerocrete blockwork with internal plastering and external brick facing. The windows and balcony doors are made of PVC profiles with glazed units. The floor over the crawl space as well as the attic floor is thermally insulated. All the buildings have centralized heating supply and natural ventilation. The buildings were constructed within the framework of the regional targeted program for people resettlement from unserviceable and dilapidated housing. Including several buildings into the object of investigation increases its credibility and allows expanding the obtained results to a larger group of buildings of analogous architectural-andstructural solution. The heating degree-day HDD = 3925 C day/year. The in-service period of the building at the moment of the inspection is about 5 years. Visual-and-instrumental inspection was carried out for the purpose of general evaluation of the object’s thermal performance. The inspection was conducted in situ through visual observation and instrumental measuring with the follow-on desk study of the obtained results. The visual observation and measuring were carried out on 22.08.2014 in the day-time under natural lighting. In the process of the inspection general observation of the buildings and of some flats was conducted. The geometrical parameters of rooms, building envelops and engineering systems were measured on a selective basis. Removing the overburden was used in the process of external walls inspection. While examining, overview and detailed photography was applied. The thermovision control of the thermal insulation quality of the object building envelopes was carried out to reveal latent defects in the thermal performance of buildings in situ. The thermovision control of the object carried out by OOO «Engineering Group «Expert Analytical Centre» was followed by quantitative evaluation of the results fulfilled by the author. The thermovision control was carried out on 14.03.2014 in the day-time at the difference of internal and external air temperature of 19 24 °C and heat transfer conditions close to the steady-state one. At the moment of the inspection all the buildings were heated. The inspection was carried out at the absence of wind, atmospheric precipitation, fog or smoke. Throughout the measuring process the external surfaces of the buildings envelopes were not exposed to direct or reflected solar radiation. The thermovision measuring was carried out applying a thermographic camera Guide IR 928+ (serial # 500597). In the process of thermovision control 139 calibrated thermograms were obtained including 19 ones taken at the external surface. The total number of the examined segments of buildings envelopes equals to 130, which is sufficient for getting statistically credible results. The calculated evaluation of the thermotechnical indices of buildings envelopes was carried out on the basis of numerical modeling of thermal conditions. The calculation carried out applying computer program [8] was conducted for the most dangerous element of the envelope — the junction node of an external wall and a column. The analysis of the thermal conditions of the structure was carried out at the steady-state conditions of heat transfer. The geometric characteristics of the structure were assumed as those obtained through field observations and design data. The design thermotechnical characteristics of the building envelope materials and the boundary conditions were assumed according to the Regulatory Document SP 50.13330.2012. 3. Results and discussion In case of the field study the numerous thermotechnical defects were revealed (Fig. 1 and 2).


Fig. 1. Thermotechnical defects

Fig. 2. Temperature anomalies and defects

Basing on the results of the visual-and-instrumental inspection the following thermotechnical defects were revealed (Fig. 1): (a) absence of tambour at each of the entrances to the buildings; (b) there are traces of mould at the internal surface of the junction nodes of external wall with a column and a floor and of a window unit with wall aperture; (c) the actually realized structural solution of external walls does not comply with the design documentation; (d) the mounting of window units was carried out with multiple violations; (e) the actual filling of wall apertures in all the buildings does not comply with the design one; (f) the continuity of thermal insulation of the attic floor was not provided; (g) heating devices and pipes in the flats do not comply with design documentation; hand regulating cocks at the heating devices were realized instead of the designed automatical thermoregulators; (h) there is no thermal insulation on the heating supply pipes in the crawl space. Basing on the visual-and-instrumental inspection the conclusion on the non-compliance of the stated object with the requirements of the design and normative documentation was drawn. The thermograms obtained through thermovision control (Fig. 2) allowed revealing temperature anomalies and defects of the object: (a) local defects of building envelope; (b) defects of translucent building envelope elements; (c) temperature anomalies in the junction nodes of external wall with a column and a floor; (d) defects of erection joints in the connection nodes of window units and wall apertures; (e) temperature anomalies in the zones of floors and in external wall corners; (f) defects of the heat-exchange surface of heating devices. Further generalization of the thermovision control results is realized in the classification of defects of building envelope (Table 1), depending on the temperature coefficient which is determined through the formula:

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194


-

t int t si t int t ext ,

(1) In (Eq. 1) tint is internal air temperature; tsi is minimum temperature at the internal surface of building envelope and text is external air temperature. Table 1. Building envelope defects classification [8] Class of defect

Range of values -

Defect

A

from 0 to 0.255

Absence of defect depending on thermal coefficient

B

over 0.255 to 0.476

Moister condensation at internal surface of building envelope

C

over 0.476 to 1

Frost penetration through building envelope

The analysis of the results of the statistical processing of thermovision control data (Table 2) shows that more than a half of the structures examined (62 %) have defects, which indicates their massive occurrence. All the defects are of hard-to-eliminate character and demand structural dismantling. The overwhelming majority of defects (90 %) are traced at the connection nodes of window units and wall apertures, which is explained through inadequate quality mounting of translucent building envelope elements. The defects in the junction nodes of an external wall and a column (10 %) are stipulated by the presence of heat-conducting insertions due to deviations against the design project. Practically half of the structures examined (51 %) are susceptible to moister condensation and mould formation at the design conditions, 11 % of the structures examined demonstrate frost penetration through building envelope at the nodes. Thus, the thermovision control of the object’s thermal performance quality made it possible to reasonably reveal defects of building envelope and to outline the ways of their elimination. Table 2. Statistical processing results of the thermovision control data on building thermal performance quality Index

Index value

Total number of structures examined

130

Total number of defects

81

Average number of defects per structure

0.623

Distribution of defects according to the type of structure [%]: junction node of external wall and column

10

connection node of window unit and wall aperture

90

Distribution of defects according to the type of defect [%]: free of defects

38

moister condensation and mould formation

51

frost penetration through building envelope nodes

11

The calculated thermal conditions evaluation at the junction node of an external wall and a column was conducted in two variants (Fig. 3, Table 3): 1 — with non-ventilated air layer (according to the actual condition); 2 — with air layer filled with efficient thermal insulator

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Fig. 3. Calculation scheme of the junction node of an external wall and a column upon the calculated variants (left — upon variant 1, right — upon variant 2): 1 — reinforced concrete column; 2 — plaster; 3 — aerocrete blockwork; 4 — air layer; 5 — mineral wool boards; 6 — brickwork Table 3. Design thermotechnical characteristics of the building component materials Density [kg/m3]

Specific heat [kJ/(kgK)]

Heat conductivity [W/(mK)]

Layer

Material

1

Reinforced concrete

2500

0.84

1.92

2

Plaster

1700

0.84

0.7

3

Aerocrete blockwork

450

0.84

0.2

4

Air layer (at 0 qC)

1.29

1.005

0.294 (equivalent)

5

Mineral wool boards

80

0.84

0.047

6

Brickwork

1400

0.88

0.52

Calculation is executed at the following parameters: internal air temperature is 20 °C; internal surface thermal coefficient is 8.7 W/(m2×K); external air temperature is –22 °C; external surface thermal coefficient is 23 W/(m2×K). The calculation results show (Fig. 4) that a thermal conditions anomaly is noticed in the zone of the column. On variant 1 the minimum temperature at the internal surface of the node (12.06 C) is higher than the internal air dew point (td = 9.28 C at tint = 20 C and int = 50 %). The increase in the internal air relative humidity to 60 % can lead to moister condensation in the zone of the wall-column joint and to mould formation (variant 1). It is fully confirmed by the results of the visual-and-instrumental inspection (Fig. 1) as well of thermovision control of the object (Fig. 2). The building envelope according to variant 1 does not comply with the sanitary and hygienic requirement of SP 50.13330.2012 and is defective. The application of mineral wool insulation on variant 2 improves the temperature-and-humidity conditions of the building envelope (minimum temperature is 15.53 C) and provides the sanitary and hygienic requirements compliance.

Figure 4. Temperature fields (left) and diagrams of temperature distribution at the internal surface (right) for the junction node of an external wall and a column upon the calculated variants

The results of the temperature fields calculation were used for the determination of extra heat loss through the studied node according to the method DIN 4108 Bbl 2:2004–01 in order to assess its energy efficiency. The analysis of the calculation results shows [8] that a non-insulated node (variant 1) has sufficient extra heat loss ( 1 = 0.222 W/(m K)) which indicates its low energy efficiency. Insulating the node with mineral wool boards (variant 2) enhances its thermal performance and energy efficiency ( 2 = 0.098 W/(m K)). Thus, the calculated evaluation of building envelope thermotechnical indices basing on the numerical modeling of heat transfer made it possible to reasonably develop suggestions aimed at enhancing the building envelope elements.

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4. Conclusion An evaluation of thermal performance of residential buildings envelope was carried out. Basing on the visualand-instrumental inspection the conclusion on the non-compliance of the stated object with the requirements of the design and normative documentation was drawn. The thermovision control allowed revealing latent defects of the buildings envelopes and outlining the ways of their elimination. The numerical modeling of heat transfer made it possible to reasonably develop suggestions aimed at enhancing the building envelope elements. The integrated application of these methods gave an opportunity to determine the thermotechnical state of the object in whole. The obtained results indicate the necessity for thermal modernization of the buildings. The results of the study serve as a basis for the development of methodological foundations for design, construction, operation and renovation of energy-efficient buildings. References [1] Vatin, N.I., Gorshkov, A.S., Nemova, D.V., Staritcyna, A.A., Tarasova, D.S. The Energy-Efficient Heat Insulation Thickness for Systems of Hinged Ventilated Facades (2014) Advanced Material Research, 941–944, pp. 905–920. [2] Vatin, N.I., Nemova, D.V., Tarasova, D.S., Staritcyna, A.A. Increase of Energy Efficiency for Educational Institution Building (2014) Advanced Material Research, 953–954, pp. 854–870. [3] Alihodzic, R., Murgul, V., Vatin, N., Aronova, E., Nikoliü, V., Taniü, M., Stankoviü, D. Renewable Energy Sources Used to Supply PreSchool Facilities with Energy in Different Weather Conditions (2014) Applied Mechanics and Materials, 624, pp. 604–612. [4] Zadvinskaya, T.O., Gorshkov, A.S. Comprehensive method of energy efficiency of residential house (2014) Advanced Materials Research, 953–954, pp. 1570–1577. [5] Petrichenko, M., Vatin, N., Nemova, D., Kharkov, N., Korsun, A. Numerical modeling of thermogravitational convection in air gap of system of rear ventilated facades (2014) Applied Mechanics and Materials, 672–674, pp. 1903–1908. [6] Polovnikov, V.Y., Gubina, E.V. Heat and Mass Transfer in a Wetted Thermal Insulation of hot Water Pipes Operating Under Flooding Conditions (2014) Journal of Engineering Physics and Thermophysics, 87 (5), pp. 1151–1158. [7] Korniyenko, S.V. The Experimental Analysis and Calculative Assessment of Building Energy Efficiency (2014) Applied Mechanics and Materials, 618, pp. 509–513. [8] Korniyenko, S.V. Complex assessment of energy efficiency and thermal performance for buildings (2014) Construction of Unique Buildings and Structures, 11 (26), pp. 33–48. [9] Korniyenko, S.V. Multifactorial forecast of thermal behavior in building envelope elements (2014) Magazine of Civil Engineering, 8 (52), pp. 25–37. [10] Taylor, T., Counsell, J., Gill, S. Combining thermography and computer simulation to identify and assess insulation defects in the construction of building façades (2014) Energy and Buildings, 76, pp. 130–142. [11] Polovnikov, V.Yu., Piskunov, M.V. Numerical probability analysis of low-temperature insulation destruction under the condition of periodic duty (2014) EPJ Web of Conferences 76, 01030. doi: 10.1051/epjconf/20147601030. [12] Gorshkov, A.S., Rymkevich, P.P., Vatin, N.I. Simulation of non-stationary heat transfer processes in autoclaved aerated concrete-walls (2014) Magazine of Civil Engineering, 8 (52), pp. 38–48. [13] Korniyenko, S.V. The increase of power efficiency of building at the expense of reduction of heat losses through edge zones of enclosure (2010) Academia. Architecture and Construction, 3, pp. 348–351. [14] Nemova, D.V., Tarasova, D.S., Staritsyna, A.A., Nefedova, A.V. Results of educational building’s inspection (2013) Construction of Unique Buildings and Structures, 8 (13), pp. 1–11. [15] Ulybin, A.V., Vatin, N.I. The quality of the visual inspection of buildings and structures, and the method of its execution (2014) Construction of Unique Buildings and Structures, 10 (25), pp. 134–146. [16] Vatin, N., Nemova, D., Ibraeva, Y., Tarasevskii, P. Development of Energy-Saving Measures for the Multy-Story Apartment Buildings (2015) Applied Mechanics and Materials, 725–726, pp. 1408–1416. [17] Vidas, S., Moghadam, P. HeatWave: A handheld 3D thermography system for energy auditing (2013) Energy and Buildings, 66, pp. 445– 460. [18] Korniyenko, S. Thermal Comfort and Energy Performance Assessment for Residential Building in Temperate Continental Climate (2015) Applied Mechanics and Materials, 725–726, pp. 1375–1380. [19] Korniyenko, S.V. Temperature-and-moisture conditions of ventilated facades walls (2009) Academia. Architecture and Construction, 5, pp. 389–394. [20] González-Aguilera, D., Rodriguez-Gonzalvez, P., Armesto, J., Lagüela, S. Novel approach to 3D thermography and energy efficiency evaluation (2012) Energy and Buildings, 54, pp. 436–443.