Conference Agenda

Overview and details of the sessions of this conference. Please select a date or location to show only sessions at that day or location. Please select a single session for detailed view (with abstracts and downloads if available).

Session Overview
Session 21: Glazing & shading technologies
Thursday, 26/Aug/2021:
2:00pm - 3:30pm

Session Chair: Ulrike Passe, Iowa State University
Location: Room 4 - Room 015, Building: 116

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2:00pm - 2:15pm

Electrochromic Glass system in Norwegian Climate: Control strategies and Impact on the indoor thermal conditions

Alessandro Nocente, Steinar Grynning, Lars Gullbrekken

Sintef AS, Norway

Several studies have demonstrated that the use of electrochromic windows can both improve the visual and the thermal conditions of the indoor environment and have a positive impact on the energy consumption for heating and cooling.

The present work investigates by simulations the influence that such devices have when used in a modern wooden cabin with large window area in a colder climate.

The building is situated on an open terrain without any shading from the surroundings, as common in wooden cabins.

The climatic areas considered are 4 different locations in Norway. The windows on the Southern and Western façade are equipped with an EC glass and each of them is activated by an independent automatic control. Three different control systems were used and compared.

All the calculations were repeated with the solar shading system deactivated through all the simulation time, and again with the EC glass replaced by a traditional integrated external textile screen.

Results suggest that the EC glass have a quantifiable impact on the internal temperature, reducing the temperature peak by up to 2°C and the number of hours of high temperature by circa 33% with respect to the configuration without solar shading.

The quantifiable effect is also noticeable in the amount of energy spent for heating and cooling.

The traditional integrated textile system has a slightly higher impact on the temperature and the overheating, but with a consistent decrease in the visual comfort towards the outdoors that will have to be evaluated in future works.

2:15pm - 2:30pm

In-situ performance evaluation of historic box-type windows with vacuum glazing

Matthias Schuss1, Ulrich Pont1, Magdalena Wölzl1, Peter Schober2, Ardeshir Mahdavi1

1Department of Building Physics and Building Ecology, TU Wien, Vienna, Austria; 2Austrian Forest Products Research Society (Holzforschung Österreich), Vienna, Austria

Climate protection objectives and energy efficiency targets imply stricter performance expectations from both new and retrofit building projects. Given the related important role of the building envelope, there is a need for a holistic approach to the design, construction, as well as laboratory and field testing of buildings' window and wall systems. In this context, the present contribution reports on recent efforts regarding the thermal retrofit of box-type windows. In the course of an actual research project, vacuum glazing (VIG) elements were integrated with ten existing box-type windows at six locations in Austria. To facilitate empirical testing and evaluation of these windows, a detailed concept for a continuous in-situ performance monitoring concept was designed and implemented together with the required monitoring infrastructure. This infrastructure involves the deployment of regular state-of-the-art IoT (Internet of Things) technology and enables the continuous monitoring of the salient performance indicators (including temperature, relative humidity, and heat flow). The derived values of performance indicators (such as the fRsi-value) can facilitate, among other things, the assessment of water vapor surface condensation risk. Collected data since mid-2020 cover both hot and cold weather periods have been analysed to capture performance differences between alternative vacuum glass settings at the testing locations. The alternative implementations pertain to different positions of the glazing layer (inside versus outside), different opening directions of the casements, and different positions of box-type within the opaque wall. Moreover, for comparison purposes, monitoring equipment was integrated into a comparable regular box-type window (with float glass or insulation glass) at each of the demonstration sites. Occurrences of potential visible or functional defects (including surface condensation) have been documented as well. The paper presents, analyses, and discusses the preliminary findings of this effort in detail.

2:30pm - 2:45pm

Advancements in glazing coating technologies

Khaled khaled, Umberto Berardi

Ryerson University, Canada

This paper presents a comprehensive review of the current state-of-the-art coating technologies for glazing applications with the objective of identifying the most promising technologies. Several static coatings with fixed optical properties are compared, including electrothermal and photothermal coatings. Electrothermal coatings that convert electricity to heat by the Joule effect are discussed, along with their limitations of needed power supply. In order to overcome these limitations, photothermal coatings have been proposed to improve thermal performance by absorbing ultra-violet and near-infrared radiation. On the other hand, dynamic coatings can modulate solar gains by switching between clear and tinted states in response to external stimuli. Electrochromic and gaschromic coatings are still limited by their high fabrication costs. In comparison, photochromic and thermochromic coatings are more accessible technologies, although photochromic coatings are still hindered by low switching rates and poor cyclic stabilities. Finally, this paper shows that both static and dynamic technologies thrive to enhance optical and thermal performances, whereas the development of passive dynamic hybrid photo-thermochromic coatings seems the most promising trajectory.

2:45pm - 3:00pm

Parametric Energy Simulation of Solar-NIR selective Glazing Systems

Qiuhua Duan1, Enhe Zhang1, Laura Hinkle1, Julian Wang1,2

1Department of Architectural Engineering, The Pennsylvania State University, United States of America; 2Materials Research Institute, The Pennsylvania State University, United States of America

A few types of metallic nanoparticles have been found to have strong photothermal effects (PTE) on near-infrared light irradiation, paving the way for new designs of spectrally selective building glazing systems for solar near-infrared (NIR) modulation that operate without the need to compensate for visible transmittance. Incorporating such nanoscale effects into the design of complex building fenestrations, this research conducted a comprehensive investigation to better understand the thermal and optical behaviors of windows with photothermal coatings in terms of the solar NIR-induced heating effect and conductive, convective, and radiative heat exchanges between the windows and surrounding indoor and winter outdoor environments. We first developed and then validated a coupled optical and thermal analysis method that incorporates spectral features, solar spectral irradiance, and nanoscale PTE. Utilizing the steady-state thermodynamics theory in building physics, this study is the first to analytically exact the solar NIR-dependent thermal models of such glazing systems, in terms of photothermal heating effects, temperature profiles, etc. Subsequently, a parametric energy simulation method in EnergyPlus was developed and incorporated the solar NIR-induced thermal models developed in the previous step. The annual heating energy savings due to the modulation of solar infrared by building windows were reported, analyzed, and compared to the low-e coated double pane windows. The results showed that compared to low-e coated windows, more than a 20% heating load reduction could be obtained by photothermal windows in winter on vertical building façades under typical solar irradiance. Notably, these energy savings were not achieved by increasing the thermal insulation via additional layers or insulating materials, but rather by the spectrally selective design of glazing materials and utilization of solar near-infrared energy.

3:00pm - 3:15pm

Energy-saving and comfort improvements to the control of residential Venetian blinds

Joseph Roberts1,2, Giuseppe De Michele1, Giovanni Pernigotto2, Andrea Gasparella2, Stefano Avesani1

1Eurac Research, Italy; 2Free University of Bozen-Bolzano, Italy

The Solar Window Block is a multifunctional stand-alone window block for the refurbishment of residential buildings, which includes a dynamic shading system, a ventilation machine and a PV system for energy production. The design of the shading control strategy is crucial for the correct performance of the whole window system. Therefore, this study focuses on the control of the shading system, which consists of movable Venetian blinds. In this work, multiple improvements to an existing on/off open-loop control strategy in a simulated case-study apartment have been studied and simulated in TRNSYS18, thanks to the detailed optical and thermal modelling allowed by the BSDF used as input to the Type_56_CFS. The control strategy improvements include the combination of rule-based, closed-loop and discrete state control, in addition to four control strategy activation methods (three use a schedule, and one measures the external temperature). Simulated control inputs include internal temperature, external temperature and vertical irradiance. The results show that reductions in overheating are achieved without completely blocking natural illumination or compromising heating demand. While on/off control in winter often led to increased heating energy consumption, the space saw regular overheating when on/off control was not active over winter. On the other hand, discrete state control was shown to be able to more precisely control solar gains in winter such that an adequate temperature was maintained without utilising the heating system, all the while allowing some level of natural illumination. Overall, it is concluded that the choice of the control strategy ultimately depends on which objective (minimisation of heating energy consumption, maximisation of daylight harvesting, reduction of overheating risk, etc.) is prioritised.

3:15pm - 3:30pm

Electrochromic window integration in adaptive building envelopes in different climates: a genetic optimization of switchable glazing parameters to reduce energy consumptions in office buildings.

Francesco Carlucci1, Alessandro Cannavale2,3, Francesco Fiorito1

1Department of Civil, Environmental, Land, Building Engineering and Chemistry, Polytechnic University of Bari, 70125 Bari, Italy; 2Department of Sciences in Civil Engineering and Architecture, Polytechnic University of Bari, 70125 Bari, Italy.; 3Istituto di Nanotecnologia, CNR Nanotec, Via Arnesano 16, 73100 Lecce, Italy.

The huge global energy consumption and the resulting high amount of CO2 released in the atmosphere are leading to a climate crisis more quickly than expected. In facing this global threat, the building field plays a key role as responsible of nearly 32% of the global energy consumption and of nearly 40% of consumption in highly developed countries. To reduce this impact, many studies have been conducted and a particularly interesting and effective field of development is represented by adaptive technologies applied to transparent building envelopes. Among these technologies, the electrochromic (EC) glazing is one of the most developed solutions thanks to its capability to dynamically modulate daylight and solar energy, simply applying a controlled external voltage. The aim of this study is to optimize the properties of an ideal switchable glazing to find the best configuration for each climatic zone. To this end, a Python algorithm has been developed to control the simulation engine (EnergyPlus) and run a genetic optimization. We consider a 5-elements genome, constituted of the following genes: i) solar heat gain coefficient in bleached (SHGCb) and ii) coloured state (SHGCc), iii) visible light transmittance in bleached (VLTb) and iv) coloured state (VLTc) and v) thermal transmittance (U). The analyses have been run on a U.S. Department Of Energy (DOE) medium office reference model implemented with EC windows on East, South, and West façade controlled by a daylighting sensor for each thermal zone with a 500 lux setpoint. Moreover, 25 European cities have been selected as representative of European climatic zones and the models have been properly modified and calibrated to substitute the real HVAC system with an ideal loads system. The results obtained give a European “map” of the ideal EC glazing configurations in the case of EC window controlled by daylighting sensors.

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