Energy Saving Potential and Interior Temperatures of Glazed Spaces: Evaluation through Measurements and Simulations

Abstract

According to Finnish glazing manufacturers, balcony glazing has been installed in approximately 75 % of Finnish apartment balconies, i.e. more than 600 000 balconies over the whole country. Nearly all of the balcony glazing systems are constructed of 5 to 6 frameless single glass panes, whose 2-3 mm air gaps between panes are arranged to allow ventilation of the enclosed space. The main motivation for installing the glazing has been to increase the usability of the space by protecting it from the natural elements, and also from pollution and noise. As a rule, the glazing has not been constructed or installed to optimize the space’s indoor temperature conditions, nor to maximize the heating energy-saving effects.<br/><br/>The purpose of this study was to evaluate the heating-energy saving potential of the glazing, and its effects on the indoor spaces, with field measurements and computer simulations. The research consisted of detailed surface and air temperature monitoring in two balconies and their adjoining flats, and monitoring of the air temperature on 22 balconies (17 glazed) and their adjacent flats in Tampere from 16th July 2009 to 24th May 2010. The research also included a detailed case-study of a glazed-in brick building in Malmö, which involved monitoring the temperature, relative humidity and air flow in the building from the 28th of October, 2013 to the 10th of February, 2015. Along with those studies, the suitability of the IDA Indoor Climate and Energy (IDA-ICE) software for glazed space energy simulations was analyzed through a literature review and the constructed model’s 'goodness of fit', which was verified by model calibration. After that, the effects of the various characteristics of different flats, balconies and balcony glazing solutions on the heating energy consumption of both the flats and the balconies’ indoor climates were studied with 156 different calculation cases. Furthermore, there were 63 model calculations on the impact of the added glazing on the brick building’s heating energy use and indoor climate.<br/><br/>The temperature monitoring showed that the air temperature on both the glazed and unglazed balconies, and in the cavity spaces between the glazing and the brick walls of the Malmö building, remained almost without exception above the outdoor air temperature. The analyses also showed that the indoor climate of the glazed space and the achievable energy-saving potential is case-specific and is influenced by a variety of factors such as the building’s location, the type and orientation of the balcony itself, the tightness of the glazing, the inlet air pre-heating (air entering the building from the glazed balcony), and the thermal resistance of the structures. The study also revealed that IDA-ICE is well suited for its intended purpose in simulations, which can usefully be conducted within the generally used 'goodness of fit' criteria set by ASHRAE. The final outcome of the study was a simplified preliminary calculation procedure for evaluation of the heating energy-savings of the glazed spaces as well as the mean, maximum and minimum temperatures levels during the year. The results strongly indicate that this method is reliable for its intended purpose in Nordic countries.