Building Heat Loss Research Articles

Feasibility study of using poplar wastes as sand in cement mortars

An experimental investigation was undertaken to evaluate the potential use of poplar by-products in cement mortars. Two by-products from poplar processing were studied: sawdust (from sawing wood) and milled fibres (from wood waste obtained during cutting). Poplar fibres and sawdust were incorporated into mortars as sand volume substitution with rates ranging from 0 to 100%. Before introduction into the mortar, poplar aggregates were characterized (morphology and water absorption). It appeared that these wood aggregates absorb very quickly a large amount of water (up to 200%). The introduction of these poplar by-products has significant effects on the composite properties in both fresh and hardened states. It was noted that the workability of the mixtures with the poplar wood varies with the substitution rate. The inhibition of cement setting with poplar sawdust is characterized by maturity tests and affects the mechanical properties of mortars. In addition, increasing the poplar aggregates content causes a continuous increase of the material porosity, which leads to a decrease in density. Besides, it appears that the incorporation of poplar aggregates into mortars also decrease their thermal conductivities, which would help to reduce building heat losses. A significant decrease in the mechanical properties of poplar-based mortars was also noted, related to the rate of fibres or sawdust introduced into mixtures. The hydration disturbances, the high internal porosity of the wood particles and their low density can explain these lower mechanical strengths. However, despite these disturbances, the valorisation of poplar wood by-products remains possible in cementitious materials for the manufacture of concrete masonry blocks.

Energy conservation using new structured-core and transparent vacuum insulation panels: Numerical simulation with experimental validation

The rate of heat gain or heat loss from the windows of existing buildings represents a large portion of building energy consumption in harsh hot or cold regions, respectively. Therefore, several thermal insulation technologies have been applied in new buildings. However, these technologies are difficult to implement in existing buildings. Therefore, this study proposes a new, low-cost insulation method using slim, transparent panels with structured cores, for the windows of existing buildings. To do this, five new distinctdesigns of vacuum insulation panels (VIPs) are proposed to retrofit insulation for the windows of existing buildings. The VIPs comprise a hollow-frame structured-core material encapsulated in a transparent multi-layered polymeric envelope. The effective thermal conductivity of VIPs with different spacers, namely, peek, modified peek, mesh, silica aerogel, and frame, are evaluated at different pressure levels. The spacers are 3D-printed and experimentally-examined. A 3D thermal model is developed and validated using the experimental results of the present work and results from the literature. First, the influences of spacer structure and vacuum pressure on the centre-of-panel thermal conductivity, light transparency, and VIP production costs are evaluated. Second, three different trial manufacturing methods for these VIPs are proposed and compared. Finally, the annual building heat gain and heat loss in two different harsh hot and cold regions, respectively, in Japan are estimated while applying these new proposed VIP designs to the existing windows. The results indicate that VIPs with frame and mesh spacers accomplish better insulation performance, with a centre-of-panel thermal conductivity of 7 × 10−3 W/m K at a pressure of 1 Pa. Further, the VIP with the peek spacer accomplishes the highest light transparency (0.88). Furthermore, using a frame-type VIP with a total thickness of 3 mm attached to an existing window as a curtain decreases the space heat loss by approximately 69.5%, whereas the light transparency decreases to 75%. In that regard, using a frame-type VIP attached to 3 mm-glass windows decreases window insulation costs by 72% compared with vacuum glazing thermal insulation.

Methods and software of heat balance assessment of architectural objects

The complex analysis of the software for calculating the thermal balance of buildings and rational methods of graphical modeling have been performed. On the basis of consideration of available methods and software tools for designing energy efficient buildings, calculation of their energy efficiency indicators, the functional capabilities of these tools were determined and their limitations in certain possibilities were noted. A critical review of the following techniques and software has been completed:1. "Instruction for the development and drawing up of an energy passport of houses for new construction and reconstruction". Allows to calculate the total heat losses of the house through the enclosure; calculation of heat receipts during the heating period; calculation of the value of the specific heat consumption for heating the house during the heating period; assigning an A to G. energy efficiency class building2. PHPP - calculation of energy requirements for heating and maximum heating load; calculation of energy requirement for cooling; calculation of passive cooling, frequency of overload at it; calculation of the demand for renewable primary energy and the demand for primary energy of all energy services as a whole for the building; an estimate of the annual increase in renewable energy.3. ArchiPHYSIK - calculation of energy requirements for heating and cooling; calculation of environmental index OI3; calculation of sound insulation data.4. Hottgenroth - modeling of thermal behavior of buildings, zones; determination of heat load of premises; calculation of heating elements; design of drinking water systems; planning and design of home ventilation systems; energy reconstruction of buildings; calculation of load on cooling; modeling of systems of hot water supply and solar heating; design of photovoltaic systems; planning of summer thermal insulation; design of cogeneration units, heat pump systems; the ability to view 3D images at any stage of modeling; detailed preparation of documents for approval.5. Optima - calculation of heat losses for each zone; calculation of energy requirements for heating and cooling during the year; forecasting temperature in each zone throughout the year.6. "Calculation of heat losses of premises and thermal loads on the heating system of residential and public buildings" - calculation of transmission heat losses of individual rooms and buildings as a whole; calculation of energy requirements for the heating of ambient air supplied through the ventilation system; calculation of the required thermal loads on the heating system.7. “Program for express evaluation of the efficiency of energy-saving solutions” - an assessment of the contribution of a specific energy-saving solution in reducing the heat consumption of a particular home compared to the basic one due to the use of energy-saving equipment and technologies.The methods of estimating the thermal balance of a building have analyzed the possibility of modeling the internal geometry of an object, even in the presence of graphical support, in almost all methods is absent or very limited. Only Hottgenroth applications (including ETU-Planer software) and GRAPHISOFT EcoDesigner STAR have this capability. In Hottgenroth the internal geometry is taken into account in the calculations, but the inverse design problem is not solved, the graphical possibilities are limited. In GRAPHISOFT EcoDesigner STAR, the internal geometry is taken into account in the calculations, but it is not possible to set different temperature indices for different rooms as output, nor is the inverse design problem solved and the graphical possibilities are limited.

Variations of Ground Temperature in Shallow Depths in the Silesian Region

Knowledge of temperature distribution in relation to time and depth is necessary in many applications. These include: designing GSHP (ground source heat pump) and EAHE (earth-air heat exchangers) systems, calculating heat loss in buildings, in determining foundation depth for buildings and structures with consideration of frost penetration depth, designing pavement of roads and airports or designing underground systems of energy transmission. Regular measurements and perfecting models describing temperature in the ground is therefore extremely valuable. This article presents authors’ own research on ground temperature changes in time and distribution of temperature at different depths, up to c. 2.0 m beneath ground level. The tests were performed in the Silesia region over a period of 6 months between May and October, using thermistors installed in the ground at various depths. The measurements were compared with temperature of the air, measured at test stations using a meteorological multisensor in order to find a correlation. Aside from readings of temperature over time and profiles of ground temperatures the paper contains selected elements of statistical analysis of the measurements. It was noted that the temperature distribution is closely related to depth below ground level, and the influence of outside temperatures decreases with depth.

Estimations of Radiative Heat Transfers in Enclosures

In large closed spaces of buildings, the heat radiation dominates over the other two transfer mechanisms, i.e. over conduction and convection. This fact may be easily illustrated on the basis of the Stefan-Boltzmann law, Fourier’s law and convective correlations of Nusselt’s number. For this reason, when the computations of heat losses of buildings are performed, the radiative heat transfers running between inner sources of heat and inner surfaces of walls should not be overlooked. This conference contribution is devoted to such problems. In the preceding two conference contributions called “Radiative Heat Transfer in Buildings” and “Radiosity Model and Compensation Theorem”, a general model for radiative heat transfer in inner spaces of buildings has been developed and completed by the compensation theorem. This theorem mirrors the basic property of closed building envelopes stating that the total radiative heat flow in a closed envelope is zero. The present conference contribution thematically continues the preceding two contributions and applies their theoretical results to the case of radiative heat flows established within a living room consisting of 6 different grey interior surfaces. The surfaces mutually differ in temperatures and emissivities. Such an arrangement represents a real room without too much simplification. The corresponding matrix of view factors has 36 elements determined on the basis of formulae and graphs published in the technical literature. The system of 6 equations determines the 6 values of radiosities belonging to 6 interior surfaces. The radiosities represent auxiliary values that facilitate finding the heat fluxes and heat flows associated with each inner surface of the room. The sum of all the obtained positive and negative values of the heat flows has resulted in zero value which documents validity of the compensation theorem also in this complicated enclosure consisting of 6 thermodynamically different surfaces.

Improving Thermal Performance of Dwelling Single Glass Windows Using Secondary Glazing in the UK

In the globe, 40% of heat losses in domestic buildings were caused by single glazing windows usage and around 20% were due to air infiltration. Therefore, an improvement for the single glaze windows and reducing the air infiltration must be considered to lower the energy consumption. This study aims to investigate the thermal performance of secondary glazing sheet on the ordinary windows in the low-income dwellers. The PVC sheets were used as the secondary glazing which easy to tailor and fit into the windows frame in the living room. Besides, a commercial foam insulation tape was used to seal the air leakage of the windows. The indoor and outdoor temperatures of a living room, pre- and post-retrofitting, were measured and the U-values were compared based on ISO 9869:2014 standard. It is found that the respective temperature differences between indoor and outdoor at pre- and post-retrofitting were 5.6 °C and 8.6 °C. The post-retrofitting indoor temperature was more stable with fewer fluctuations compared to the pre-treatment. Furthermore, the U-values were improved by 57% where the number before and after retrofitting found to be 5.71±0.01 W/m2K and 3.23±0.01 W/m2K, respectively. Obviously, the utilisation of the proposed glazing and diminishing the air infiltration on a single glazing windows play the key role on improving the thermal comfort, cheaper than commercial double glazing, eco-friendly, and easy to install.

A framework to estimate heat energy loss in building operation

Abstract Heat energy loss in buildings occurs by two means, namely Fabric Heat Loss and Ventilation Heat Loss. Loss occurs when energy flows out through building envelope from inner warmer air to cooler air located external to the building. The purpose of this study is to identify and estimate the proportion of Heat Energy Loss that is directly caused by construction components from the building envelope. The novelty of this research is to propose a methodological framework that characterizes the Heat Energy Loss in buildings during the operation phase, taking into consideration the local climate data in which buildings are located. Reliance is on the use of a systematic approach that makes the work readily available to practitioners and experts in the area of energy efficiency. A case example of a single-family house is examined in three different climate classifications for validating the proposed method of this work. Results reveal that Fabric Heat Loss is the main factor of the Heat Energy Loss in buildings; responsible for more than 81% of the total Heat Energy Loss in buildings. Openings and exterior walls play a significant role in curbing such energy loss; accounting for around 70% of the total Fabric Heat Loss in buildings. This work points out that the percentage of energy efficiency improvement of Fabric Heat Loss is similar and directly proportional to the percentage of reduction in U-values of building components; as U-value reduces by 6.66%, the energy efficiency of Fabric Heat Loss improves by 6.66%. Besides, the analysis conducted indicates that lower air change rate would lessen the Ventilation Heat Loss in buildings. Finally, this work illustrates that Heat Energy Loss in tropical climates and dry climates could reach a value of 16% and 8%, respectively, compared to Heat Energy Loss in moist subtropical mid-latitude climates.

GENERAL MODEL OF RADIATIVE AND CONVECTIVE HEAT TRANSFER IN BUILDINGS: PART I: ALGEBRAIC MODEL OF RADIATIVE HEAT TRANSFER

Radiative heat transfer is the most effective mechanism of energy transport inside buildings. One of the methods capable of computing the radiative heat transport is based on the system of algebraic equations. The algebraic method has been initially developed by mechanical engineers for wide range of thermal engineering problems. The first part of the present serial paper describes the basic features of the algebraic model and illustrates its applicability in the field of building physics. The computations of radiative heat transfer both in building enclosures and also in open building envelopes are discussed and their differences explained. The present paper serves as a preparation stage for the development of a more general model evaluating heat losses of buildings. The general model comprises both the radiative and convective heat transfers and is presented in the second part of this serial contribution.

ТЕПЛОВИЗИОННЫЙ МЕТОД ОПРЕДЕЛЕНИЯ ВЛАЖНОСТНЫХ ПОЛЕЙ ПОВЕРХНОСТЕЙ СТРОИТЕЛЬНЫХ КОНСТРУКЦИЙ ЗДАНИЙ И СООРУЖЕНИЙ

The current issues of excess heat losses by construction projects are identified and analyzed. It is established that the heat loss of buildings depend on the thermal qualities of external building structures of different materials, the main of which are density, humidity, thermal conductivity. In this regard, practical methods for identifying temperature and humidity fields of the surfaces of building structures in the mode of their operation are of particular importance. The technical capabilities of modern thermal imaging equipment for obtaining and processing thermograms of thermal imaging of the controlled object are presented. A practical example of thermal definition and analysis of temperature and humidity fields of translucent enclosing building structures in the form of a window in a window opening is given. It is confirmed that thermal imaging diagnostics is able to state the distribution of heat losses in the control zone. On the basis of this knowledge, measures are developed to reduce them (alignment) and subsequently assess the effectiveness of their implementation

Effective reduction of building heat loss without insulation materials via the photothermal effect of a chlorophyll thin film coated “Green Window”

Abstract

Thermal performance of thermal paint and surface coatings in buildings in heating dominated climates

A purported approach to reducing heating energy in solid wall “hard to heat” housing is the simple application of a thin layer (<1 mm) of thermal paint containing insulating additives. The objective of this study was to test the energy saving claims by a systematic study of the material characteristics and thermal performance of internal coatings using accepted international standard test methods. The coatings have been compared with conventional internal coverings such as emulsion paint, wallpapers and expanded polystyrene liner. A dynamic model of the Energy House research facility has been used to evaluate energy savings, costs, and payback times.The thermal resistance of the thermal paint coatings was generally found to be not much better than that of conventional vinyl textured wallpapers with a lining paper. When all building heat losses are considered, modelling predictions for thermal paint coatings indicate an unfavourable payback period of several hundred years, and energy savings of between 0.4% and 2.9% depending on coating thickness and type. The evidence from the results and models, as well as scanning electron microscopy, do not support the claims that the additive powder particles are effectively nano-porous, evacuated, or that the coatings have low emissivity surfaces.

Influence of Window Details on the Energy Performance of an nZEB

One of the largest sources of heat loss in buildings are the windows. However, windows are alsoimportant to increase solar heat gain and provide daylight. It is necessary to understand how windowdetails influence the energy performance of very energy efficient houses. This is valuable informationfor the design decision making process and may lead to further research or product development. Thispaper examines the influence of window frame thermal transmittance, window frame width and windowinstallation depth on the energy demand of the building. A single-family prefabricated timber nZEBlocated in Estonia was used as a reference building for this study. The results show that decreasing thethermal transmittance and width of the window frame have a remarkable effect on the energy demandof the nZEB (a variation of 42% and 25% respectively). The effect of optimising window installation depthis insignificant (ca 3% variation of heat demand on most of the window placement range and up to 10%of increase in heat demand when comparing the optimal placement to the least effective one). However,it can further improve the energy performance.

Moisture potental theory application for modelling of enclosing structure unsteady-state moisture regime

Introduction. Known calculation methods for enclosing structure unsteady-state moisture regime proposed by K.F. Fokin, are examined. The first one describes moisture transfer in a sorption zone, and another allows calculation in oversorption zone also. “Thermodynamic moisture potential” of enclosing structure materials introduced by V.N. Bogoslovsky is described. Moisture potential F developed by V.G. Gagarin and V.V. Kozlov is shown. The moisture potential F allows describing water vapor and liquid moisture movement in material in a consistent way. The scientific novelty of the study is the development of calculation method based on moisture potential F. Practical relevance of the study is the possibility to obtain performance humidity values of enclosing structure materials by means of calculations for engineering practice. Materials and methods. A moisture transfer equation is derived on the basis of process physical interpretation, A mathematical model, consisting of heat conductivity equation, derived moisture transfer equation, spatial-time domain, boundary and initial conditions, is formulated. Moisture potential in single-layer and multilayer enclosing structures is determined using finite difference method. Results. Calculations for four types of enclosing structures are made on the basis of the proposed mathematical model: single-layer aerated concrete wall; a wall made of aerated concrete masonry base and clay brick cladding; a wall made of aerated concrete masonry base and mineral wool insulation with thin plaster layer; a wall made of aerated concrete masonry base and expanded polystyrene insulation with thin plaster layer. Conclusions. Calculated performance humidity values of enclosing structure materials were lower than values stated in regulatory documents. The presented results allow to define building heat loss definition and heating system design more accurately. Specification data on maximum wetting plane position obtained earlier were proved within the framework of the developed theory: in enclosing structures with aerated concrete base and mineral wool insulation maximum moisture content is located at the joint of plaster and insulation layers; in enclosing structures with aerated concrete base and expanded polystyrene insulation maximum moisture content is located in the insulation layer. Acknowledgements. Authors are deeply indebted to V.V. Kozlov, PhD in Technical Sciences, and V.K. Akhmetov, Doctor of Engineering Science, Professor, for discussion and useful comment in the course of study.

The The Occurrence of Thermal Bridges in Hemp-Lime Construction Junctions

Thermal bridges increase heat losses in buildings and reduce the temperature of the internal envelope surface, causing moisture condensation and mould growth. This is an important issue for building materials based on organic components such as a hemp-lime composite, as they are particularly susceptible to biological degradation.The hemp-lime composite is used as a filling in timber frame construction. The increased cross-section of wooden elements together with the geometry change in the construction joints can form thermal bridges. The paper presents numerical analyses of temperature distribution in the area of construction elements connections, taking into account several variants of junctions: external walls, corners, and window placement in a wall. The thermal parameters of hemp-lime composites used in the analyses were obtained from the authors’ own research.Despite relatively good insulating properties, timber elements have a noticeable influence on the local increase of the heat transfer in hemp-lime composite structures, forming thermal bridges in the partitions themselves and in the construction nodes. However, the linear thermal transmittance coefficients in the presented joints were not very significant (in the range of 0.026 ÷ 0.092 W/(m·K) depending on the type of connection), proving the usefulness of this type of construction in energy-efficient buildings.

Effect of radiative cooling on heat transfer through building partitions

The article analyses the impact of radiative cooling on heat loss in buildings. Radiative cooling means a temperature decrease of external surfaces of building partitions below the ambient temperature. The phenomenon occurs in certain conditions – cloudless sky at night, on horizontal and inclined building surfaces. Based on the dependencies recommended in literature and standards, a mathematical model describing heat transfer in the conditions of radiative cooling has been adopted. The analysis was based on two models of building partitions, i.e. roof-ceiling and insulating glass unit (IGU). For a roof-ceiling, the study analyses the impact on heat loss in the conditions of radiative cooling of such factors as thermal insulation thickness, wind speed, surface emissivity, etc. Heat losses occurring in the conditions of a cloudless and overcast sky have been compared. For IGUs, the study analyses the impact of radiative cooling on heat transfer by convection and radiation in the sealed gas-filled gap. The results of own experimental testing of temperature drop on the surface of IGUs in operating conditions are also presented. It was found that radiative cooling of building partitions in certain weather conditions has a significant effect on heat losses, which should be included in calculations, particularly in the case of horizontal and inclined partitions.

Comparative performance analysis of Vacuum Insulation Panels in thermal window shutters

Windows are a major area of heat loss in buildings and can lose up to 10 times more energy than other building elements. In a typical house, around 10% of heat is lost through the windows. Thermal shutters could considerably reduce heat losses through windows and improve the energy performance of buildings. Insulation plays a major role in overall performance of thermal shutters. Advance insulation material such as Vacuum Insulation Panel (VIP) can help in improving the performance of thermal window shutters. VIP with a thermal conductivity of 0.005-0.008 W/mK is a high thermal resistance and energy efficient alternative to conventional thermal insulation materials. In this paper, effect of VIP and conventional insulation has been investigated and compared for enhancing the thermal performance of window shutters using computer simulations. Results indicate significant reduction in heat loss through windows when VIP insulation was employed in internal thermal window shutters. Thermal bridging was found to be the significant factor that deteriorated the performance of the shutter. Reducing heat loss through the frame and surrounding walls could improve the VIP insulated shutter thermal performance by approximately nine times.

Monitoring system of an energy efficient school building

The paper presents details regarding the implemented monitoring system of heat loss, interior comfort and energy consumption particularities of an energy efficient school building in Romania. Despite the fact that there is an emphasis on energy saving and sustainability in the building industry legislation and policies, there are still too few examples of good practice at local level. Recent trends have brought changes in how designers solve specific details like thermal insulation thicknesses and use of renewable energy but further improvement is required for a more detailed understanding of the entire building's energy balance behaviour both on overall and specific details level. Therefore, a complex monitoring system was built in a carefully designed and constructed school building in order to collect relevant real-time data of every specific part of the thermal envelope, the HVAC systems and interior comfort parameters. The main purpose of the system is to highlight the order of magnitude of the differences between the design and the real-time values of the most significant parameters, the importance of each detail and also the need of further research development in this field.

ВЛИЯНИЕ ПРИЧИН ФОРМИРОВАНИЯ ДИНАМИКИ РАСПРОСТРАНЕНИЯ ВЫСОЛОВ ПРИ ВЗАИМОДЕЙСТВИИ ИНФИЛЬТРАЦИОННЫХ И ЭКСФИЛЬТРАЦИОННЫХ ПОТОКОВ НА ТЕПЛОЭФФЕКТИВНОСТЬ ЗДАНИЙ

The article discusses options for technical solutions to increase the level of thermal protection of buildings and reduce the cost of their operation when interacting infiltration and exfiltration flows of moisture in enclosing structures. An analysis of the dynamics of efflorescences in the winter period indicates an increase in chemical processes at the contact of the facing verst and the insulation layer, in which slag accounts for 60-65%. These water soluble salts migrate to the freezing front. However, the reason for the accelerated migration in the winter is the exfiltration of warm moist air through the unsealed joints of the stoned panels during the installation of the stairwell. Also in the parapet, the largest efflorescence is due to the penetration of vaporous moisture through a monolithic reinforced concrete ceiling into the insulation layer, and from there into the brickwork of the parapet. Studies of heat and mass transfer, moisture transfer in various designs have shown that the combination of the interaction of infiltration and exfiltration leads to large heat losses and a deterioration in the thermal regime and indoor microclimate. Thus, the survey results showed that efflorescence is an important indicator of additional heat loss of buildings and structures, and the use of effective heat-insulating materials is not always enough. Errors and defects in the design and construction of structures and natural ventilation systems have a direct effect on reducing the thermal efficiency of exterior fencing.

Forecasting the need for inclusion of the heating system with application of fuzzy logic methods

Currently, when predicting the operating modes of heating systems, only temperature is taken into account. But other factors also influence human perceptions: wind speed, humidity, cloudiness, light. When calculating the heat loss of buildings, these factors are also taken into account, but not when determining the operating modes of heating systems. The article proposes to assess the need to turn on the heating system based on the value of a fuzzy function that simulates the concept of «perceived temperature».

A METHOD TO EVALUATE THE IMPACT OF URBANIZATION ON GROUND TEMPERATURE EVOLUTION AT REGIONAL SCALE

The replacement of natural soil and vegetation by artificial surfaces increases temperatures of the surrounding air and subsurface throughout the year, because of indirect solar heating of urban structures, building heat losses and land use change. This phenomenon is called Urban Heat Island and it can be better perceived during night-time, when the city releases the heat accumulated during the day. During day-time, due to relatively small amounts of solar radiation received by urban surface, especially in high-density cities in arid and semi-arid climates, Urban Cool Island can be identified as well. The present work illustrates a mixed probabilistic-deterministic method to estimate ground temperature at shallow depth, starting from information on geology, hydrogeology, climate, but also urban presence, through correlations with global land cover and population density. A dedicated mapping on regular grid has been produced. Results have been compared with ground and aquifer temperature available in the literature, for some representative cities of Italian Peninsula and Alpine Zone. Preliminary validations are encouraging and can be taken as a starting point for more comprehensive mapping of ground temperature evolution at regional scale.