The Impact of Infiltration on Heating Systems Dimensioning in Estonian Climate

Abstract

In this study we analysed the climatic conditions for infiltration estimation, different calculation methods and infiltration impact on heat load for heating systems dimensioning. To determine the wind conditions at low air temperatures of the coastal- and inland climatic zones in Estonia, 42 years of climatic data for Tallinn and Tartu were investigated. Calculation models with detailed air leakages were constructed of a single and two-storey detached house using dynamic simulation software IDA ICE. Simulations were carried out with the constructed calculation models, simulating various wind and sheltering conditions to determine the heating load of the buildings under measured wind conditions at the design external air temperatures. The simulation results were compared with results calculated with European Standard EN 12831:2017, methodology given in the Estonian regulation for calculating energy performance of buildings and with simulations using the default settings in IDA ICE based on the ASHRAE design day conditions. The percentage of heat losses caused by infiltration was found as 13-16% of all heat losses for the studied buildings. Simulations with historical climate periods showed that even in windy weather conditions the heating system dimensioned by the methods analysed may not be able to provide the required indoor air temperature. Analysis using the coldest and windiest periods showed that when systems are dimensioned by the studied methods, the highest decline in indoor air temperature occurs on the windiest day and not on the coldest day. The impact of high wind speeds and low sheltering conditions resulted up to 50% of all heat losses.

Model-Scale Reproduction of Fan Pressurization Measurements in a Wind Tunnel: Design and Characterization of a New Experimental Facility

“…where q is the volumetric airflow rate (m 3 •s −1 ), C is the leakage coefficient (m 3 •h −1 Pa −n ), ∆p is the inside-outside pressure difference (Pa), and n is the airflow exponent (-).…”

“…where ∆p is the pressure difference between inside and outside at the opening (Pa), C p is the wind pressure coefficient at the opening (-), ρ is the air density (kg m −3 ), U is the wind speed at the height of the building (m•s −1 ), and p in is the indoor pressure relative to the external pressure (Pa). By replacing each variable with the respective dimensionless and reference variables, the first dimensionless numbers were obtained, as shown in bold in Equation (3).…”

“…However, as the experimental facility was meant to be used for future studies, the relations between the scale ratios as defined in the general situation were considered. Thus, the scale ratio for the area was A = (1/25) 2 , the scale ratio for the volume was V = (1/25) 3 , and the scale ratio for the volumetric airflow was q = (1/25) 2 .…”

“…More recently, Amanowicz et al [2] presented new studies that confirm the energy impact of buildings' airtightness. In particular, Simson et al evaluated the infiltration heat losses for two reference cases in Estonia [3] and estimated that they represent, in most cases, 13 to 16% of the total building heat losses but can reach 50% for the highest wind speeds configuration. In Spain, Poza-Casado et al conducted a study using more than 400 blower door tests performed on Spanish dwellings over several periods and locations [4].…”

Airtightness performance of the building envelope of dwellings in Spain. Characterisation and energy impact of air infiltration

“…Therefore, advanced insulating materials have significantly solved the energy loss issue due to conduction through the building envelope, but the energy loss due to convection caused by air leakage cannot be ignored any longer. Infiltration, essentially determined by building airtightness, represent 10%-30% of the heating demand (Domínguez-Amarillo, Fernández-Agüera, Campano, & Acosta, 2019;Huang, Hanford, & Yang, 1999;Jokisalo, Kurnitski, Korpi, Kalamees, & Vinha, 2009;Jones et al, 2015;Kalamees, 2007;Meiss & Feijó-Muñoz, 2015;Simson, Rebane, Kiil, Thalfeldt, & Kurnitski, 2020;Zheng, Cooper, Gillott, & Wood, 2020).…”