Thermal performance of slab on grade with floor heating in a passive house

Extensive experimental investigations have been carried out in the passive house in Boruszowice for several years. The building foundation interface consists of a 25 cm reinforced concrete slab situated on a 40 cm layer of Styrofoam. The analysis of experimental results as well as theoretical calculations made it possible to determine the thermal performance of the applied slab on grade with floor heating during the whole yea

Integration of Modelica models into an existing simulation software using FMI for Co-Simulation

Abstract The Functional Mock-up Interface (FMI) opens new opportunities for the development and extension of existing non-Modelica simulation programs with Modelica models. For the developer this is a productive way to design and validate new complex simulation models with multi-domain modeling languages such as Modelica. With the standardized Functional Mock-up Interface (FMI) and the Functional Mockup Unit (FMU) export it is possible to execute these models within other software tools, including information exchange during the simulation. However, there are some design requirements in Modelica, which have to be taken into account. In this paper, models for different HVAC (Heating, Ventilation and Air Conditioning) equipment configurations are integrated into existing software using the FMI. An interface extension plug-in is developed to pick a specific FMU and execute it alongside the existing simulation algorithm. Two different coupling algorithms were investigated: the iterative and the cosimulation approach. Some issues and practical hints for a successful coupling and simulation are presented

A holistic modeling framework for estimating the influence of climate change on indoor air quality

The IPCC 2021 report predicts rising global temperatures and more frequent extreme weather events in the future, which will have different effects on the regional climate and concentrations of ambient air pollutants. Consequently, changes in heat and mass transfer between the inside and outside of buildings will also have an increasing impact on indoor air quality. It is therefore surprising that indoor spaces and occupant well-being still play a subordinate role in the studies of climate change. To increase awareness for this topic, the Indoor Air Quality Climate Change (IAQCC) model system was developed, which allows short and long-term predictions of the indoor climate with respect to outdoor conditions. The IAQCC is a holistic model that combines different scenarios in the form of submodels: building physics, indoor emissions, chemical-physical reaction and transformation, mold growth, and indoor exposure. IAQCC allows simulation of indoor gas and particle concentrations with outdoor influences, indoor materials and activity emissions, particle deposition and coagulation, gas reactions, and SVOC partitioning. These key processes are fundamentally linked to temperature and relative humidity. With the aid of the building physics model, the indoor temperature and humidity, and pollutant transport in building zones can be simulated. The exposure model refers to the calculated concentrations and provides evaluations of indoor thermal comfort and exposure to gaseous, particulate, and microbial pollutants.Peer reviewe

Urban Climate Under Change [UC]2 – A National Research Programme for Developing a Building-Resolving Atmospheric Model for Entire City Regions

Large cities and urban regions are confronted with rising pressure by environmental pollution, impacts of climate change, as well as natural and health hazards. They are characterised by heterogeneous mosaics of urban structures, causing modifications of atmospheric processes on different temporal and spatial scales. Planning authorities need reliable, locally relevant information on urban atmospheric processes, providing fine spatial resolutions in city quarters or street canyons, as well as projections of future climates, specifically downscaled to individual cities. Therefore, building-resolving urban climate models for entire city regions are required as tool for urban development and planning, air quality control, as well as for design of actions for climate change mitigation and adaptation. To date, building-resolving atmospheric models covering entire large cities are mostly missing. The German research programme “Urban Climate Under Change” ([UC]2) aims at developing a new urban climate model, to acquire three-dimensional observational data for model testing and validation, and to test its practicability and usability in collaboration with relevant stakeholders to provide a scientifically sound and practicable instrument to address the above mentioned challenges. This article provides an outline of the collaborative activities of the [UC]2 research programme

Calcium isotope (δ^44/40Ca ) variations of Neogene planktonic foraminifera

Measurements of the calcium isotopic composition (δ44/40Ca) of planktonic foraminifera from the western equatorial Pacific and the Indian sector of the Southern Ocean show variations of about 0.6‰ over the past 24 Myr. The stacked δ44/40Ca record of Globigerinoides trilobus and Globigerina bulloides indicates a minimum in δ44/40Casw (seawater calcium) at 15 to 16 Ma and a subsequent general increase toward the present, interrupted by a second minimum at 3 to 5 Ma. Applying a coupled calcium/carbon cycle model, we find two scenarios that can explain a large portion of the observed δ44/40Casw variations. In both cases, variations in the Ca input flux to the ocean without proportional changes in the carbonate flux are invoked. The first scenario increases the riverine calcium input to the ocean without a proportional increase of the carbonate flux. The second scenario generates an additional calcium flux from the exchange of Ca by Mg during dolomitization. In both cases the calcium flux variations lead to drastic changes in the seawater Ca concentrations on million year timescales. Our δ44/40Casw record therefore indicates that the global calcium cycle may be much more dynamic than previously assumed

Investigating overheating by measurement and simulation in classrooms

New two-story wood-construction classrooms where added to an existing heavy-weight construction school building in the year 2006. The glass façade of some classrooms is south oriented. The building design meets the local thermal protection requirement of 2006, but the indoor temperature rises above thermal comfort conditions in the classrooms. As usual in Germany, no active cooling device is and shall be used. Measurements during holidays with close to none internal loads in addition to measurements during regular school occupancy documented the overheating. The measurement results were used to verify a baseline hygrothermal building simulation model that represents the status quo. Various passive measures with regards to construction, design and operation to improve the thermal comfort were assessed. Among them are ventilation strategies and solar protection foil on the glass façade. Furthermore, the already installed temporary sunscreen devices and mechanical night ventilation system coupled to mechanically openable skylights above the classroom doors and within the gravel covered flat roof were investigated with different operating strategies. This paper presents the required steps to improve the simulation model with the measured data in an iterative process. Measures to improve building performance, achieve thermal comfort, and protect overheating are identified

Implementation and validation of a long-wave heat exchange model

The hygrothermal whole-building simulation software WUFI® Plus was extended with a new model: the calculation of longwave radiative heat exchange between surfaces inside a zone. This allows a more detailed calculation of the interior radiative and surface temperatures, which also results in a better simulation of indoor climate conditions. The model also takes into account the optical properties of indoor surfaces, such as low-e coatings. Further benefits are a more comprehensive comfort assessment, for example, for asymmetric radiant temperature. Radiant temperatures can also be calculated for every position inside a zone. The model uses Gebhart factors for the calculations of long-wave heat exchange between surfaces inside a zone. These factors describe the fraction of emitted energy from one surface that is absorbed at another. They are determined from view factors, which only describe geometrical relationships between surfaces. WUFI® Plus uses a numerical triangulation method to calculate the view factors. As the Gebhart factors also consider optical properties of surfaces, all possible radiation paths, including multiple and own reflections, are taken into account for the calculations. Single parts of the calculation process are successfully validated with analytical solutions: the view factor calculation of a nontrivial room geometry and the long-wave heat exchange between two parallel plates show only minimal deviations from the analytical results. The German standard DIN EN 13791 provides tests for the validation of interior long-wave heat exchange. The model was successfully validated with them. In an exemplary application case, simulations with the new model are used as a preliminary study to determine the required accuracy and positioning of measurement equipment of a future test room. The simulated surface temperatures were successfully used as a plausibility control. The measurements will later be used as an experimental validation test for the new model

Anbindung von detaillierter Anlagentechnik an hygrothermische Gebäudesimulation

The multi-domain modelling language Modelica offers a magnificent method to develop, simulate and validate of different simulation models. Some graphical user interfaces support this design process even more and reduce the amount of work. Besides, the software development fort the end user is done with traditional programming languages as for the development for the hygrothermal building simulation software WUFI® Plus. Specialized and efficient solution techniques compute the coupled heat- and moisture transfer through the building components and furthermore by coupling those components the indoor climate. This paper describes the existing building simulation with ideal plant equipment and the implementation of the dynamic simulation of the plant equipment designed in Modelica. Those detailed Plant equipment models are coupled via the Functional Mock-up Interface (FMI) to the existing software. Necessary improvements are shown. A developed configuration tool enhances the coupling of many and different models without any further source code adaptations. Finally, a short example simulation is done to present some of the new features with this coupled simulation

Annex 55: Reliability of energy efficient building retrofitting-probability assessment of performance and cost (RAP-RETRO): Practice and guidelines

This report could be used as a guideline for building owners on the possible risks and benefits of various energy retrofit options available to them. There are also best-practice examples provided which show projects of retrofitting and what should be considered and how the improvements can be implemented. Potential risks for retrofitting will be addressed in detail; most of them are related to: - Thermal bridges; - Moisture damages; - Uncertain cost calculation; - Improvement on ventilation (airflow, efficiency, thermal comfort). The advantages can be summarized as: - Increased living thermal comfort (indoor climate); - Use of existing building structure; - Cost savings for heating energy. These aspects are illustrated from different views of the Annex 55 participating countries. Most of the contributing countries are located in Europe: Austria, Belgium, Denmark, Estonia, Finland, Germany, Great Britain, The Netherlands, Portugal, Slovakia and Sweden; while three countries are from North-/ South- America: Brazil, Canada and the USA The energy consumption for the space conditioning of buildings can be reduced by the appropriate combination of several measures: - insulation of components: roof, wall and floor, - application of insulating glazing - airtightness of buildings, - orientation of buildings and rooms for the use of passive solar energy, (not a retrofit option) - use of an efficient and environment-friendly heating system, - installation of comfortable and efficient ventilation, - use of renewable energy as heating support, -use of heat pumps as heating support, - solar shading to avoid overheating in dwellings. Several studies have shown that the most efficient way to curb the energy consumption in the residential building sector (new & existing) remain the reduction of the heat loss by improving the insulation of the building envelope (roof, floor, wall & windows). Thermal insulation (combined with the application of high performance windows) holds a key position among these measures, which lay the foundation of low-energy building. The basic rules for low-energy building are - the reduction of energy demand and - production of the remaining demand more effectively and preferably - from renewable sources. The chapters of this report are organized by country to quickly guide the reader to find information which is relevant for to the reader or to inform about the statistics of other countries. In the end of each chapter, there is a compilation and overview of all countries, which summarizes the overall similarities and trends and points out major differences. Chapter 2 provides an overview of the energy consumption in residential buildings. This chapter should help to estimate the total effort and potential for each country in general. Chapter 3 covers the national regulation standards in order to provide the designer a scheme where to look for relevant standards and general references. The national regulations are birefly summarized and the most important information is highlighted. Chapter 4 highlights the most important data which should be considered when building new residential buildings or retrofit existing ones. Mainly thermal transmittances of the envelope, thermal bridges and ventilation regulations are addressed. Chapter 5 lists questions regarding testing of retrofitting. This might be relevant for building owners and architects or manufactures. Chapter 6 is divided into retrofitting certain building envelope parts. Contributing countries present typical examples of retrofitting including their risks and benefits from a national perspective. In addition, further local examples and references can be found in chapter 7. Finally, the last chapter summarizes this document, points out the most relevant information and provides a guideline on how to write guidelines for building owners, constructors and decision makers

Monthly balance based method versus transient whole building energy simulation for passive house design

For the design of the so called passive houses a monthly balance based method, is used. This paper compares the balance based method of the Passive House Planning Package (PHPP) with the results of an easy to use whole building energy simulation software based on a simplified black-box model. The different calculation methods for all heat flows influencing the energy performance are compared. Shortcomings and advantages of the different methods are discussed. It is shown that both methods can produce similar results when transient effects are neglected. It can be concluded, that the time demand to set-up a complete calculation in each of the tools is approximately the same. The amount of information and possible improvement strategies regarding energy demand and comfort that can be achieved are higher with the transient simulation