Ulrich Pont

A comparison of projected and actual energy performance of buildings after thermal retrofit measures

This article addresses the discrepancies between projected and actual energy performance of thermally retrofitted buildings. Toward this end, we use detailed data and observations pertaining to seven residential buildings in Austria that were thermally retrofitted recently. These include five multifamily residences in Vorarlberg, the upper level of a duplex house in Lower-Austria, and a residential complex for the elderly in Styria. During the heating season 2009–2010 (1st October–30th April), indoor temperature and relative humidity levels were measured and logged in these buildings. For each building, the actual energy use during this period was derived based on bills for gas and electrical power. Additionally, we obtained and examined existing energy calculations (energy certificates) for these buildings. In six cases out of seven, we found a large discrepancy between projected and actual space heating demand. To explore possible reasons for this discrepancy, we generated for each of the buildings an energy certificate and performed detailed thermal simulations. Thereby, we took the main input parameters for energy calculations into consideration (air change rate, indoor air temperature, outside air temperature, and internal gains). If we use standard (default) values as suggested by Austrian standards for these parameters, the above-mentioned discrepancy cannot be explained. Measurements in the buildings, as well as interviews with the building’s inhabitants implied that standard-based input data assumptions were not reliable. A subsequent multi-factor study suggested that specifically the assumptions regarding air change rates might be responsible for the large deviations of the calculated values from the actual heating demand.

SEMERGY: Performance-Guided Building Design and Refurbishment within a Semantically Augmented Optimization Environment

This contribution illustrates recent efforts in the research project SEMERGY, a computational environment, which incorporates semantic web technologies to support building design and refurbishment optimization. A major part of the necessary information for energy efficient building planning is implicitly available in the World Wide Web. However, this theoretically valuable repository of information cannot be practically used, given its ill-structured nature. SEMERGY addresses this very problem through a number of developments. Specifically, SEMERGY: 1) embeds a comprehensive building data model, 2) incorporates an Ontology for building product data, 3) deploys a rule-based logic for identification of valid building construction alternatives, 4) provides an easy-to-use optimization procedure evaluating energy demand, environmental impact, and investment costs of alternatives, and 5) offers a web-based Graphical User Interface. The present contribution provides a general overview of the whole project and documents the state of its development.

SEMERGY.net: automatically identifying and optimizing energy-efficient building designs

A central goal of European and national climate and energy programs is to reduce the greenhouse gas emission of buildings. SEMERGY is a web-based optimization environment, which supports users in decision-making regarding energy-efficient building designs. Taking the user-specified criteria investment costs, final energy demand of the building, and environmental impact of used building products into account, the system identifies efficient building designs and retrofit options. The following steps were taken: (i) development of a comprehensive building data model, (ii) creation of an ontology of linked building product data, (iii) development of a rule-based system to automatically identify valid construction alternatives for building components, (iv) development of a multi-objective optimization procedure, and (v) creation of a web-based Graphical User Interface to enable data entry and user interaction. The present contribution provides an overview of the progress made in the above mentioned domains.

Double Skin Facades with Natural Ventilation Capability: A Case Study of Acoustical Enhancement via Passive and Active (Noise Cancelling) Methods

Within an ongoing project, we explore the potential of double skin facades to provide both noise control and natural ventilation capability. Three strategies are investigated: i) Manipulation of sound paths via offset of the openings in the two shells of the façade; ii) Application of absorbing materials in the interstitial space of the façade; iii) Active noise cancelling methods utilizing wave-destructive interference. This contribution describes the overall project but focuses primarily on the active noise cancellation approach. Aside from a comprehensive background research on existing technology, we undertook the design of an actual setting for noise cancellation testing with suitable low-cost components as a proof-of-concept. Results of the experiments are expected to inform subsequent efforts to include noise-cancelling technology in double skin facades.

Comparison of Simulated and Actual Energy Use of a Hospital Building in Austria

This paper compares calculated and measured energy use data (for space heating and cooling) pertaining to a hospital building in Austria. The buildings existing energy certificate as well as monitored heating and cooling demand information were acquired from the hospitals administration. Moreover, the energy performance of the building was modeled using a numeric simulation application. Thereby, an extensive effort was made to define model input assumptions (building construction, weather data, internal gains) based on actual circumstances in reality. The results of the study suggest that calculated (energy certificate) and simulated heating loads were reasonably close to actual values, whereas in case of cooling loads considerable discrepancies were observed.

Evaluation of Thermal Environment and Indoor Air Quality in University Libraries in Vienna

This contribution presents the results of an indoor environmental study of university libraries in Vienna. Indoor climatic parameters (air temperature, relative humidity, and CO2 levels) in the main spaces of four different library buildings (two historic buildings from the 19th century, two buildings from the late 20th century) were monitored over a period of ten months. Furthermore, to obtain a general impression of the quality of the visual environment in these buildings, illuminance levels at selected locations were measured. The measured data was analyzed and enriched with additional calculated indicators (e.g., PMV/PPD). To put the monitored data in the proper context, recorded outdoor climate data was also taken into consideration. The findings point to a certain overheating risk during the summer period as well as increased CO2 levels during the winter period.

An Inquiry into the Current Practice of Building Product Data Handling by Different Stakeholders in Austria

The timely availability and quality of building product information is critical prerequisite for a successful building delivery process. However, little is known about the processes by which stakeholders acquire and use such data. This contribution documents the results of recent relevant surveys, addressing the building product data processing by planers, clients, and the industry. Web questionnaires and interviews with opinion leaders were conducted. Altogether, over 100 participants provided pertinent insights regarding strengths and weaknesses of the current data representation practices. A comparison of the obtained data with that of an earlier study allows for the documentation of the evolutionary trends in web-based data provision. Most importantly, the results facilitate the formulation of strategies for a more effective presentation and distribution of building product data.

High-Tech Solutions for Building Retrofit: Investigation of Window Systems with Vacuum Glazing

The retrofit of the historical building stock has gained significance due to energy efficiency requirements in the building sector. Major attention is drawn to windows as they are typically the building components with the highest heat transfer coefficient of the building envelope. Therefore, vacuum glazing is a potential option for improving the thermal performance of casement windows. In this context, specific considerations regarding building physics and heritage protection regulations are required.The present contribution describes the current progress of the research project VIG-SYS-RENO. New double glazing products with durable vacuum layer are emerging on the market. Such developments can be regarded as a major step toward energy-efficient windows with U-values close to conventional opaque building elements. Small thickness and excellent thermal resistance of vacuum insulation glazing renders it an attractive option in thermal retrofit of historical buildings. Vacuum glazing systems could potentially offer a feasible balance between conservation and thermal performance of windows. However, prior to any application, a set of aspects and potential issues have to be assessed and explored. These include: (i) thermal bridging effects in different joint positions, for instance the glass edge seal and the frame & wall joint; (ii) the positioning of tight layers in composite or casement windows; (iii) aspects of structural integrity of windows equipped with vacuum glazing. The present contribution structures the different aspects that need to be considered in utilization of vacuum glazing in thermal retrofit, describes applied evaluation methods, first results of the ongoing research project, and illustrates the influence of various rebate depth and length of the edge seal on thermal transmission of the window.

Monitoring of a Prototypical Free-Running Building: A Case Study in a Hot-and-Humid Climate

The provision of comfortable indoor conditions is widely considered as one of the key tasks of architecture. Hereby, different climatic regions require different concepts for the operation of buildings. Achieving thermal comfort in buildings in hot and humid regions without Air-Conditioning can be considered as a challenging task. In this context we present a monitoring study of the indoor conditions in a new prototype building, called the Zero Carbon Resort Demonstration Cottage. This building was designed according to passive cooling principles with the intent to reach a high degree of sustainability and to have little environmental impact. To explore the viability of this concept, we deployed a comprehensive monitoring of the outdoor conditions via a weather station and of the indoor conditions via air temperature and relative humidity sensors. Moreover, short-term monitoring of thermal comfort was conducted. In a first analysis step we compared the results of the indoor monitoring with the corresponding outdoor measurements. In a second step we conducted a standardized thermal comfort study. Thereby we considered the special circumstances of the thermal comfort in naturally ventilated buildings. Results suggest that acceptable indoor conditions can be maintained, if passive cooling methods are applied properly.

Rule Based Building Construction Generation: An Approach Based on Formal Language Methods

The composition of efficient and appropriate building constructions is a key agenda in the building delivery process. While this process is regularly considered to be of highest importance for the final quality of a building, many involved stakeholders regard it as a cumbersome and repetitive routine. Therefore, approaches to facilitate this process should be investigated. Toward this end, we address the layer-wise building component composition via formal language methods. These are regularly used in computer science to formalize real-world processes into a language that can be processed by a computer. Regarding building component generation, relationships and interdependencies between different layers need to be considered. While these are easy to understand for a skilled human planner with pertinent domain knowledge, the exact formulation of building composition rules is far from trivial. Thus, automated building part generation requires collection and formalization of the required knowledge regarding building component composition, so that it can be readily transformed into a processual form. After collection, definition and structuring of such rules, the overall process of component generation can be expressed in Pseudo-Code. This offers three major advantages: i. Pseudo-code is vendor and platform neutral and is a widely used concept in computer science; ii. Potential mistakes and issues can be easily identified, iii. Flexibility, extensibility and editing ease is ensured. In this contribution we illustrate a general approach, define certain rules and thresholds, and introduce a formalized method for building part generation. Furthermore, we demonstrate the concept via a limited number of constructions and discuss potential application scenarios.