• Energy Research

AbstractThe aim of this study is detailed analysis of long-term monitoring data of thermal comfort conditions and energy efficiency in small test buildings equipped with different heating systems. Calculations of PPD index and local thermal discomfort factors are provided for the test buildings during three weeks of heating season. It is shown that the type of heating system has influence not only on heating energy need, but also on thermal comfort conditions in the room.

EU legislation provides the implementation of most building energy performance measures at a subnational level. This obligation is causing a lot of completely new dilemmas that are challenging for local governments (LGs), requiring a radical re-evaluation of the prioritization of LGs’ traditional tasks and the ranking of new responsibilities. The attitude of local population and businesses towards the solutions to dilemmas, which are set by LGs decisions, vary widely. Separate groups actively lobby for their mutually contradictory interests, questioning decisions and fighting against them during the decision-drafting and -making process, significantly hindering the work of LGs and prolonging decision-making. The authors’ suggested solution to the problem is to make municipal decisions based on verifiable data and facts, thus preventing the manifestations of populism and demagogy, and reducing the possibilities for interest group advocacy. To obtain objective information for balanced decision-making about the benefits and costs of heating system retrofitting projects without carrying out the labor-intensive, time-consuming, and costly design of various options, an express methodology and an easy-to-use tool for project feasibility studies have been developed. The methodology utilizes a limited number of open indicators to streamline the evaluation process, and does not require specific knowledge in thermal physics, economics, or construction.

Abstract Reduction of the CO2 emissions in the atmosphere is one of the goals set forth by the European Union, hence various directives have been adopted, such as the European directive 2012/27/EU on energy efficiency, i.e. ensuring from 2019 the construction of the near-zero energy buildings (nZEB). The construction segment plays a very important part in solving the current global problem of the greenhouse gas emissions and related processes of global warming, because in certain countries (i.e. in Latvia) it represents more than a half of the total energy consumption. Hence the necessity to elaborate means on how to boost the energy efficiency of the buildings meanwhile not rising pressure on the CO2 emissions released by the industry of construction materials and their transportation. Hemp-lime concrete is one of the materials that can be used to increase the energy efficiency, it is a new thermal insulation material produced from the local raw materials, and in its production cycle more CO2 is absorbed than produced. This research aims at determining the thermal insulation properties of this material in field conditions and comparing them with results from the laboratory measurements to analyse performance of such materials in the temperate continental climate zone of Europe. Measurements have been recorded on a specifically designed portable measurement equipment with sensors for the temperature, humidity and heat flux. The obtained results present a positive correspondence with the laboratory measurements, thus proving high potential for use of these materials to increase the energy efficiency of buildings.

Thermal insulation bio-composites made of plant origin by-products as bio-aggregates are one of the ways to decrease the impact of the building and construction sector on CO2 emissions. In this study, three bio-aggregates were analysed for their potential use in the production of bio-composites with potato starch binder. Technologically important properties, such as particle size, shape and compacted bulk density, as well as properties of the resulting bio-composites were identified. The main characteristics of the aggregates are relatively similar: density of 80–100 kg/m3, thermal conductivity of 0.042–0.045 W/m∙K, specific heat capacity of 1240–1330 J/g∙K, kinetic water absorption from 456–584%. This leads to similar basic properties of the produced bio-composites: density around 200 kg/m3, thermal conductivity 0.053–0.062 W/m∙K, specific heat capacity 1250–1450 J/kg∙K, with a difference in compressive strength ranging from 0.2 to 0.8 MPa. Created starch binder and agricultural by-product filler materials could be used in the production of boards where strength is required, for example, envelope and wind barrier boards, and thermal insulation boards under floors.

Abstract Five test stands have been built in Riga, Latvia equipped with sensors (temperature, solar radiation, humidity, etc.) to measure energy efficiency and thermal comfort conditions. Roof and floor constructions are made the same. For the walls building envelopes differ and typical materials used in Latvia (aerated concrete, ceramic building blocks, wooden log and plywood frame with rock wool insulation) are compared. Only rock wool is used for insulation to provide moisture transport through the construction. For study to be comparative thermal transmittance of all five test stands have been calculated equal (U=0.15…0.16 W/(m 2 ∙K)). The aim of research is to compare the integral calculation results with measured ones. Another aim is to compare the energy consumption and humidity results of last heating season to previous years and see if the initial conditions still influence the energy consumption. The heating during the period is done using electric heaters instead of heat pumps as in previous years, so that the coefficient of performance is unity. The results show that even during the fourth full heating season initial humidity in aerated concrete construction still haven’t completely evaporated and the thermal transmittance is decreasing towards the theoretically calculated data provided by manufacturer. Linear heat loss coefficients are calculated for corners and results show that for such small buildings the corners’ impact can be considerable.

AbstractTo increase the energy efficiency of buildings in Latvia's climate a comparative study with five experimental test buildings have been set up in Riga, Latvia. Different thermo physical quantities such as temperature, humidity, air velocity, etc. were monitored to better understand different behaviour of the building envelope. This gives an excellent validation possibility for the CFD model that in future could predict conditions in buildings with different envelopes. Previously a stationary model and transient model were considered without taking into consideration the thermal radiation. This study continues the previous work that was done and proposes a transient model which takes into account the thermal radiation. The results are compared for two cases with different set of experimental data that were used in the initial study.

Abstract In practice, during the design stage of a building, only the initial costs are taken into account. These costs are also discussed with the customer and optimised with the aim of reducing them. It is the global costs over a longer period that show the real difference in the total expenses of living in a particular house, however. In this study, one newly built, nearly zero energy single-family building was studied in detail using a comparative global cost calculation methodology. The most popular insulation materials, construction types, types of windows, and types of floor construction in Latvia are included in the calculation of the costs. The results demonstrate that initially cheaper building means lower global costs during the analysed 30-year operating period due to initial costs are significantly higher than all other costs including energy costs, meaning that changes in construction type and building materials affect the initial cost more than the long-term energy costs. In parallel, different modern heating systems (including heat pumps) were included in the analysis to calculate and compare heating expenses. The results show that almost all the heating systems have the same energy costs regardless of fuel type for the 30-year period, however, the initial costs of these systems vary due to the different used technologies. Therefore, only the sum of the initial and long-term energy costs provides objective information about heating systems that are optimal in the long-term.

Five experimental test buildings have been built in Riga, Latvia. They are identical except external walls for which different mainly regional building materials are used. Calculated U-values of the other walls, floor and ceiling are the same for each test building. Initial moisture influences the relative humidity of indoor air, which can be higher in the initial time period; as a result, heat transmittances are also very different and cause different heating/cooling energy consumption. Overheating risk in summer exists for test buildings with the smallest thermal inertia. Both summer and heating seasons have been analysed and differences between five test houses have been discussed in details.