Raimondas Bliūdžius

The effect of vertical air gaps to thermal transmittance of horizontal thermal insulating layer

Abstract In order to reduce the amounts of work at the construction site, single‐ply dual density thermal insulating roofing boards are used with increasing frequency for thermal insulation of flat roofs. In this case, the joints between boards are not overlapped by the other ply over it; therefore gaps of varying width form between the sides of the boards through the entire thickness of the insulating layer, whose effect on the effective thermal conductivity of the thermal insulating layer must be evaluated. The aim of this project was to assess the reliability of standard method, used to determine the impact of such air gaps on the effective thermal conductivity of the thermal insulating layer by comparing the results of calculations and the results of measurements of thermal conductivity, also to determine the correction factors for thermal transmittance of horizontal thermal insulation layers due to the forming vertical air gaps between the single‐ply mineral wool boards. After measurements of thermal...

Pollutants emission from building materials and their influence on indoor air quality and people performance in offices

Abstract New technologies and materials have introduced a large quantity of new pollutants emitted to the indoor air. Energy conservation for economical reasons, resulting in low outdoor air supply rates, can become the reason of a poor indoor air quality. The cost of the deteriorated indoor climate, resulting in reduced comfort and losses in productivity, for the society is higher than the costs for the heating energy or ventilation systems in the same building. An experiment was conducted to determine how poor indoor air quality could cause involuntary changes in performance and occurring sick building syndrome symptoms. Twenty‐four female subjects were exposed to three environmental conditions, while performing normal office tasks in a low‐polluting room. Sick building syndrome symptoms, the perceived air quality and performance data were obtained. The acceptability of air quality was significantly better and the odour intensity was much lower under the conditions of high ventilation. The performance o...

The heating load determination of low energy buildings in northern climate

Abstract Low energy buildings require an efficient thermal insulation of the envelopes ensuring minor heat losses; such buildings must be tight in order to avoid heat losses due to over-infiltration. Installation of a heating recovery system compensates for some heat used for heating the ventilation air. The design solution of transparent envelopes of low energy buildings determines significant solar heat gains that compensate for a part of heat losses through the envelopes and ventilation systems. Taking into account these properties of low energy buildings, the modeling of indoor temperatures of such building was carried out at varying outdoor temperatures and power of the heating system. On the grounds of the obtained results, it was determined that a lower heat source power than the one determined according to the outdoor temperature of the coldest five-day period can be used to meet the indoor microclimate requirements in a low energy building. In this way, the expenses of heating system installation...

Impact of heat reflective coatings on heat flows through the ventilated roof with steel coatings

Abstract In many EU countries, the normative requirements for thermal characteristics of roofs are associated only with rating the heat losses through the roofs during the heating period. The problem of overheated premises under the light-weight ventilated roofs, covered with steel sheets, arises in the summer time. During this period of the year, because of the intensive solar radiation and high air temperature, the steel roof coatings heat up during the day and cause additional heat inflows to the premises. One of the most effective means to reduce the additional radiative heat flow from the interior surfaces of the roof coating into the attic is to install radiant barriers with low emissivity coefficient into the roof construction. The experimental research has shown that having heat reflective coatings with low emissivity coefficient (e = 0.09) installed on the exterior surface of the thermal insulation layer of the ventilated roofs with steel coatings, the heat flow from the roof coating through the ...

CONVECTION IN MINERAL WOOL USED AS INSULATION FOR BUILDINGS

Abstract The paper considers the velocities of air movement in the ventilated air gaps of walls and focuses on pressure fields in both wall models arranged in a climatic chamber and exploited houses. The article investigates the influence of air movement on heat transfer through walls applying numerical modelling methods and conducting experiments in the climatic chamber. The thermal effects of air flows have been described with reference to the Nusselt number defined as the ratio of average convective and conductive heat fluxes and heat flux through still air

On the solution of energy balance equation system to predict temperature distribution in the building elements with ventilated air gap

AbstractThe article presents the solution of heat balance equation system, describing heat exchange processes in ventilated envelopes, which was applied to derive formulas for the calculation of temperatures in the ventilated layers of the envelopes. The accurateness of the formulas was assessed by experimental research and analysis of the calculation results. During the process of heat exchange balance equation solution, the equations were simplified by introducing the following restriction into the derived formulas: they may only be applied for the ventilated envelopes with steel or similar coatings as their external layers, i.e. coatings having small heat capacity and minor difference between the external and internal surface temperatures. The derived formulas enable the calculation of the temperatures of the ventilated envelopes in the distance which does not exceed a half of the ventilated air gap length measuring from the air entrance into the gap. However, this restriction does not impede the estim...