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The Architecture, Engineering, and Construction (AEC) industry is transitioning toward using cloud-based Common Data Environments (CDEs) with interlinked BIM models. A CDE that engages all stakeholders of the building's design, construction, and operation phases represents the outset of BIM maturity level 3. This article introduces a CDE called Virtual Commissioning (VC), capable of commissioning an HVAC system before the physical commissioning of the HVAC system. The FSC diagram is introduced, to represent an HVAC BIM model within the VC CDE, and the Revit to FSC exporter, to serialize an HVAC object model from Revit to the FSC diagram. Three microservices were developed to exemplify the ease of developing independently scalable solutions for the VC CDE. Furthermore, the article proves that Modelica simulations can be run, using the microservice architecture of the CDE. To test the robustness of the system architecture for the CDE, two example models were introduced, one simple and one with a high level of complexity. Transferring the example models from Revit to the VC CDE was successful. Finally, in the roadmap for future development, it is proposed that future work should focus on using the CDE for advanced hydraulic simulations, using Modelica and Spawn-of-EnergyPlus.

This paper investigates experimentally the cooling performance of a concept, where the radiant ceiling is suspended from the hollow-core concrete slab and by ventilation supply in the plenum and the perforations of the ceiling tiles, ventilation air is distributed without ducts and air terminals to the occupied zone. Literature has proven that this concept allows for more streamlined installation procedures and excellent performance in terms of thermal comfort and draught. The paper reports experimental results from a climate chamber, where the concept was tested under both steady-state and quasi-steady conditions. The steady-state conditions were chosen to map the cooling performance with different air change rates, and different ventilation and water supply temperatures. The results showed that for air change rates of 3 h−1 in the occupied zone and water supply temperature of 17 °C, the cooling output from the ceiling increased by 10 %. The concept was also tested under quasi-steady conditions in a 48 h cycle to quantify the thermal buffering effect of the exposed upper concrete slab when subjected to ventilation supply air. The effect amounted to 11–12 % increased cooling capacity at the end of the working day when the driving temperatures between air, water and thermal zones were at their maximum.

Storage tanks are commonly used for domestic hot water (DHW) preparation in large buildings supplied by district heating (DH), especially to cope with peak demand. The charging control of DHW tank systems is often suboptimal, increasing return temperatures and harming the overall DH operation efficiency. This paper presents two novel control concepts to optimise DHW tank charging, satisfying comfort and hygienic requirements without leading to excessive DH flows. The first, more complex control concept employs the smart energy meter sometimes used for DHW billing. It inspired the development of a second, broadly implementable control concept employing a staged proportional gain with an added temperature sensor. The authors tested and refined this staged-gain concept using a validated Modelica model of a real DHW system in a Danish multistory residential building. The authors subsequently implemented the staged-gain control concept in the field, successfully reducing the energy-weighted DH return temperature by 7 °C and the total DH flow by 23.6% compared to the conventional thermostatic control. This analysis accounted for the variation in DHW tapping, DHW temperature, DH supply temperature, and cold water temperature. Furthermore, the performance was robust to relaxed settings of the valve constraints, demonstrating minimal configuration requirements for new implementations.

The focus on energy conservation in buildings is increasing. Despite that, the yearly building renovation rate is only at around 1 %. To increase the renovation rate, new and time-efficient methods used for screening of large building portfolios’ energy saving potential are needed. In this paper, a re-engineered take on the classical energy signature method is applied to two renovated apartments in Denmark. The energy signature model relies on time-series measurements of space heat consumption, outdoor temperature, solar irradiation, and wind speed. The estimates obtained from it consist of—among other things—heat loss coefficient and wind-induced heat loss. This paper focuses on the latter. To validate the model estimate, the airtightness has been quantified by blower door-tests in both apartments: the results showed that one apartment is reasonable airtight, while the other suffers from significant air leakages. The energy signature and two other infiltration models, based on blower door test results, were compared. Good agreement between the results obtained from the data-driven energy signature and the blower door test were found. With use of a simple linear relation between the average infiltration and the blower door test result (q50), from the Danish national building code, the energy signature was found to overestimate the blower door test result (q50) by 33 % for the leaky apartment and underestimate the same air flow by 18 % for the other apartment. Both estimates are within the standard error of the infiltration model in the Danish national building code.

Monitoring performance of heating, ventilation and air-conditioning (HVAC) during building operation enables to evaluate the appropriateness of the system’s design. Such insights can help to reduce energy consumption while ensuring satisfying indoor conditions in the monitored building. Additionally, such insight can help to improve future HVAC design. The aim of this paper is to present a case study demonstrating how HVAC engineers can evaluate whether the monitored air-handling units (AHUs) were appropriately sized and performed as intended based on design requirements regarding energy-efficiency, thermal conditions and indoor air quality (IAQ). Three months of measurements of airflow, electrical power, indoor temperature and CO2-concentrations were collected from an office building with six AHUs. The results showed that three of the AHUs were appropriately sized and satisfied the thermal condition, IAQ and energy-efficiency requirements. The remaining three AHUs were apparently appropriately sized and satisfied IAQ requirements, but they did not satisfy the required energy-efficiency and thermal conditions. The applied approach seemed to be suitable for supporting building operating managers for on-going performance monitoring as it was able to identify discrepancies from intended performance. But it remains the task for the operating personnel to identify the cause of the identified discrepancies.

A field lab study was conducted to determine how much the indoor climate parameters, ventilation and lighting, influence children’s academic abilities. The study involved 92 children, aged 10-12 years, who over four weeks answered a questionnaire and three different performance tests, which measured their processing speed, concentration, logical reasoning and math solving abilities. An experimental design was constructed to test the effect of changing the lighting from constant warm light with 2900 K and 450 lux to a dynamic cool light with a maintained correlated colour temperature average of 4900 K and 750 lux. The change was tested at both low (3.9 l/s per person) and high ventilation rate (10.6 l/s per person). The results showed that processing speed (6.6%, P

This paper reports on a demonstration project where a section of a school building with eight classrooms and three other rooms was retrofitted with a mechanical balanced ventilation system with an integrated evaporative cooling unit. The floor area was 537 m2. Especially in temperate climates, evaporative cooling has unreleased potential as an alternative solution to conventional cooling technologies, and by combining it with harvesting of rainwater, the solution aligns well with a future with higher cooling needs, need for climate adaptation, and the overall sustainability agenda. The cooling unit works by storing, filtering and spraying rainwater into the return air. The water evaporates, cools the return air, and through an innovative corrosion-resilient plastic heat exchanger, the return air then absorbs heat from the supply air. In this way indoor climate problems caused by humidification of the indoor air are avoided. The demonstration was running in the May and June 2019. The results show that the specific fan power increased approx. 500 J/m3 when the evaporative cooling pumps were activated and that the available cooling power – depending on the moisture content of the return air – was fluctuating in the range 20-30 W/m2. The peak rainwater consumption was approx. 1 m3/day. The results show that implementation of evaporative cooling with harvested rainwater is an attractive and sustainable alternative to mechanical compressor cooling.

Comprehensive retrofit of dwellings frequently relies on the installation of partially automated heating and mechanical ventilation systems. While energy consumption is often successfully reduced, this intrusion of complex building services into the domestic sphere may create new challenges for the occupants. Through a questionnaire distributed to 2007 households in a social housing complex undergoing energy retrofit, this work seeks to identify the link between indoor environmental satisfaction and occupants' perceived ability to use and control residential heating and ventilation technology. The response rate was 17.1% (344 houses, of which 241 were retrofitted). Occupants expressed a general satisfaction with the indoor environment in retrofitted houses. However, they also expressed difficulties to understand and operate their heating and ventilation systems. The study revealed significant correlations between the users’ indoor environmental satisfaction and their perception of the usability of the building services. Nevertheless, an important share of the respondents achieved satisfactory indoor environmental quality despite living with systems with poor perceived usability. These findings point towards the hypothesis that poor usability is not an issue in normal operating conditions, but the lack of personal control becomes problematic in case of dysfunctional building services or failing building envelope.

The interoperability of information from design to operations is an acknowledged challenge in the fields of architecture, engineering and construction (AEC). As a potential solution to the interoperability issues, there has been increasing interest in how linked data and semantic web technologies can be used to establish an extendable data model. Semantic web ontologies have been developed for the AEC domain, but an ontology for describing the energy and mass flow between systems and components is missing. This study proposes the Flow Systems Ontology (FSO) for describing the composition of flow systems, and their mass and energy flows. Two example models are expressed using FSO vocabulary. SPARQL Protocol and RDF Query Language (SPARQL) queries are performed to further demonstrate and validate the ontology. The main contribution consists of developing FSO as an ontology complementary to the existing ontologies. Finally, the paper introduces a roadmap for future developments building on FSO.

In recent years semantic web ontologies have improved data interoperability within architecture, engineering, construction, and operation of buildings. One of the persisting issues inhibiting quality assurance is a lack of robust model validation of BIM models used for HVAC flow system simulation and analysis. This article provides a novel approach for automating the BIM validation process using SHACL shapes and FSO/FPO ontologies. Using this approach will ensure that the BIM model contains the required HVAC information for simulating hydraulic systems. The paper presents multiple shapes developed to identify and validate typical HVAC design details in buildings.

Radiant systems are established today and have a high ecological potential in buildings while ensuring thermal comfort. Free-hanging sound absorbers are commonly used for room acoustic control, but can reduce the heat exchange when suspended under an active slab. The aim of this study is to evaluate the impact on thermal comfort of horizontal and vertical free-hanging porous sound absorbers placed in rooms of a building cooled by Thermo-Active Building System (TABS), under real operation conditions. A design comparing five different ceiling coverage ratios and two room types has been implemented during three measurement periods. A clear correlation between increase of ceiling coverage ratio and reduction of thermal comfort could not be derived systematically for each measurement period and room type, contrarily to what was expected from literature. In the first two monitoring periods in the larger office rooms, rooms with higher coverage ratios reported higher operative temperatures. This correlation was however not clear from the monitoring in the smaller offices and other measurement periods. In all monitored rooms, a strong influence of the user behaviour on thermal comfort has been observed. A higher temporal offset between ceiling and operative temperature was also observed in rooms equipped with absorbers.

Thermal ceiling systems for heating and cooling has several solutions and methods. In this study, an integrated solution that combines a radiant ceiling panel with diffuse ventilation was investigated in a reduced-scale experiment. The purpose of the experiment was to map the heat transfer from the perforated radiant ceiling panel at different ventilation rates. The experiment was scaled for similitude in the plenum. The heat transfer coefficients were compared to the literature and a previous numerical study using Computational Fluid Dynamics. The heat transfer coefficients in the plenum were on par with both the compared literature and the CFD study. It was found that the internal heat gain in the room created a high radiative-to-convective ratio, and the results were most valid for the small values (14 W/m2), where the heat transfer coefficient for cooling scenarios had an increase of 20% from no ventilation to high ventilation rate. The heating scenarios did not show a conclusive change. Although the experiments showed potential, the integrated solution should be investigated further in a full-scale experiment, as some of the uncertainties and differences could be caused by the reduced scale test setup.

Roof windows are efficient and flexible daylight sources that are essential in certain types of houses if they are to achieve sufficient daylighting throughout. Previous studies have indicated that, for such buildings to meet nearly zero-energy targets in an easy and robust way without compromising on daylighting and thermal comfort, the thermal properties of roof window glazing, frames and junctions need to be considerably improved. However, the barriers to improving roof windows to levels above the current best standard practice remain great so long as we do not know the economic benefits of such improvements. The aim of this study was to quantify the scope for investing in improved roof window solutions in buildings insulated to consume nearly zero-energy. Based on two single-family houses in Copenhagen with typical roof windows and adequate daylighting, the study identified the prices at which various types of roof window improvements would have to be made available to achieve the same cost efficiency as improved insulation. If the improvements can be made available for less than these prices, the installation of improved roof windows would make it cheaper to construct well-lit and comfortable nearly zero-energy homes.

Dynamic solar shading is commonly suggested as a means of reducing the problem of overheating in well-insulated residential buildings, while at the same time letting daylight and solar irradiation in when needed. To critically investigate what dynamic shading can and cannot do compared to permanent alternatives in buildings with very low space-heating demand, this study mapped and compared energy, daylighting and thermal comfort for various combinations of window size and glazing properties, with and without dynamic shading. The study considered a loft room with sloped roof windows and moderate venting options in nearly zero-energy homes in Rome and Copenhagen. The more flexible solution space with dynamic shading made it possible to either reduce the time with operative temperatures exceeding the comfort limit by 40–50 h or increase daylighting by 750–1000 h more than could be achieved without shading. However, dynamic shading could not improve the optimum space-heating demand of the loft room in any predictable way, and without using dynamic shading, illuminances of 300 lx in 75% of the space could be achieved in 50–63% of the daylight hours with no more than 40–100 h exceeding the comfort ranges as defined by the Adaptive Thermal Comfort (ATC) model.

International audience; In the architecture, engineering and construction (AEC) industry stakeholders from different companies and backgrounds collaborate in realising a common goal being some physical structure. The exact goal is typically not known from the beginning, and throughout all design stages, new decisions are made - similarly to other design industries [1]. As a result, the design must adapt and subsequent consequences follow. With working methods being predominantly document-centric, highly interrelated and rapidly changing design data in a complex network of decisions, requirements and product specifications is primarily captured in static documents. In this paper, we consider a purely data-driven approach based on semantic web technologies and an earlier proposed Ontology for Property Management (OPM). The main contribution of this work consists of extensions for OPM to account for new competency questions including the description of property reliability and the reasoning logic behind derived properties. The secondary contribution is the specification of a homogeneous way to generate parametric queries for managing an OPM-compliant AEC Knowledge Graph (AEC-KG). A software library for operating an OPM-compliant AEC-KG is further presented in the form of an OPM Query Generator (OPM-QG). The library generates SPARQL 1.1 queries to query and manipulate construction project Knowledge Graphs represented using OPM. The OPM ontology aligns with latest developments in the W3C Community Group on Linked Building Data and suggests an approach to working with design data in a distributed environment using separate graphs for explicit facts and for materialised, deduced data. Finally, we evaluate the suggested approach using an open-source software artefact developed using OPM and OPM-QG, demonstrated online with an actual building Knowledge Graph. The particular design task evaluated is performing heat loss calculations for spaces of a future building using an AEC-KG described using domain- and project specific extensions of the Building Topology Ontology (BOT) in combination with OPM. With this work, we demonstrate how a typical engineering task can be accomplished and managed in an evolving design environment, thereby providing the engineers with insights to support decision making as changes occur. The application uses a strict division between the client viewer and the actual data model holding design logic, and can easily be extended to support other design tasks.

This work suggests a method to evaluate residential building occupants’ neutral temperature in winter based on their interaction with their heating system. This study applies the developed method on eight new, low-energy apartments in Copenhagen, Denmark. A set of indoor temperature, heating setpoint, window opening and floor heating valve opening data was collected from mid-January to the end of April, spanning through a large part of the Danish heating season. Semi-structured interviews were performed with occupants of three of the eight apartments in order to understand their use of their heating system. This preliminary study permits to highlight the potential and the current limitations of the proposed method, both for neutral temperature estimation as such and for applications in optimizing the energy flexibility provided by the building. This article suggests directions for further elaboration of the model. The main two influential factors highlighted here affecting setpoint adjustment are the occupants’ acceptability of temperature variation and their ability to control the heating system.

The development of low energy buildings present new opportunities to develop HVAC products that works well with renewable energy sources. In this paper, we present a novel comfort system that combines a full radiant ceiling with diffuse ventilation into one flexible ceiling solution, HVACeiling. The purpose of the paper is to investigate how the combination changes heating and cooling performance and how the thermal storage cycle of the exposed slab in the closed plenum affects energy consumption and thermal comfort. The heating and cooling performance was investigated numerically in IDA ICE with daily based occurrence temperatures and compared to a reference with a radiant ceiling and mixing ventilation. The HVACeiling was a perforated gypsum board with pipes embedded that is used for diffuse ventilation and acoustical absorption as well as a radiant ceiling. Water was circulated day and night at fixed supply temperatures of 20–22 °C without any other controls. The convective surface heat transfer coefficients of the plenum was modelled in a preliminary CFD study and compared to literature and experiments. It was found that for daily based occurrence scenarios, with outdoor temperature in the range 23–28 °C, the heat exchange from the ceiling was increased 5–16% compared to the reference. The studies also disclosed improved thermal comfort, up to 1.5 °C lower peak operative temperature in the occupied zone down from 27.2 °C. This implies that thermal comfort is easier achievable with the HVACeiling, even with a small temperature offset that is well suited for renewable sources.

In the context of increasing renewable energy penetration in energy systems, demand response is acknowledged as a solution to guarantee grid stability and security of supply. Direct control of appliances by utilities, however, may lead to user dissatisfaction and disengagement via overrides. The present study, based on data from 6,389 connected thermostats in North America in the summer of 2019, investigates users' thermostat overriding behavior during demand response events targeting their air conditioners. An average event in this dataset was triggered around 3 p.m. and lasted three hours. The overall override rate was 12.9%. Overrides critically affected power usage during an event, with the share of the expected power demand reduction missed due to overrides being of the same order of magnitude as the override rate. In a decision tree analysis, the override rate showed to be particularly affected by occupants' habitual setpoint change frequency, outdoor temperature, event duration, and occupants’ previous experience with demand response. Even though the dataset is not representative of all types of demand response events, this study highlights the potential lying in connected thermostat data for utilities to design tailored demand response events with an increased success rate and a smaller impact on occupant comfort.

Occupancy is a key input variable for sizing heating, ventilation and air-conditioning (HVAC) in buildings. However, HVAC designers typically estimate occupancy data based on assumptions which rarely reflect the actual situation. Consequently, these assumptions might lead to under- or oversized HVAC systems that either provide too low or too high peak loads or ventilation airflows than actually required to satisfy indoor environmental quality (IEQ) requirements during building operation. To address these issues, existing studies suggest various methods for collecting and analysing occupancy, however mostly in single office spaces or at an overall building level. The objective of the present study was to evaluate the suitability of using passive-infrared (PIR) sensors mounted below occupants’ desks for collecting long-term occupancy data in open-plan and single office spaces. The method was tested in two office buildings for seven months. It determined occupant presence and count with an accuracy of 87.5% compared to manual observations. Furthermore, the study demonstrated that occupancy data could be used to (1) generate occupancy schedules for input in building simulation models, (2) potentially reduce design ventilation airflows for HVAC sizing and (3) evaluate decisions to change the office space layout (e.g. number of desks) for more efficient space-use.

Windows are central for the development of liveable nearly zero-energy homes and require careful consideration. Various studies have indicated that the effect of windows on energy consumption may change significantly with improved building insulation levels. Current guidelines on windows may therefore not apply in very well-insulated buildings, and more up-to-date information is needed about window solutions that are appropriate for the new conditions. This study maps the effect of multiple combinations of window size and basic glazing—and frame properties on energy, daylighting and thermal comfort in nearly zero-energy houses located in the European cities Rome and Copenhagen. The aim was to identify options that can support the easy and robust design of future homes with typical use of roof and facade windows. Hourly daylight levels were calculated in DAYSIM, while space heating demand and operative temperatures were calculated in EnergyPlus. The results support previous findings on the limited ability of nearly zero-energy buildings to utilise solar gains. It was found that U-values are becoming increasingly important for the energy performance of windows. The paper sketches the increased flexibility and related possibilities that may appear with improved roof window frame constructions and glazing U-values far lower than currently standard levels.

This paper reports on a comparative study of the indoor environment in two adjacent classrooms, one renovated, and the other non-renovated. The aim of the study was to investigate the positive consequences of renovating classrooms, but also to disclose unanticipated side-effects. The non-renovated classroom was without mechanical ventilation, fitted with woodwool ceiling plates for acoustics and lighting fixtures with horizontal illuminances of 200-300 lux on the tables. The renovated classroom was retrofitted with a new acoustic ceiling made from perforated gypsum tiles and suspended lighting fixtures and mechanical ventilation via decentral room unit mounted below the ceiling. The ventilation air was supplied in the void above the acoustic ceiling, which distributes air through perforations and joints in the ceiling to the occupied zone – a concept often referred to as diffuse ventilation. In this setup, the acoustic ceiling also acted as silencer for the ventilation inlet. Different indoor environmental parameters were comparatively measured in each classroom, including longterm CO2-concentration, temperature and noise levels as well as reverberation time and technical noise from the ventilation quipment. In all respects, the objective measurements improved in the renovated lassroom.Interviews with pupils and questionnaire surveys were conducted, and – while showing less evidence of the improvements than expected – did indicate increased user satisfaction with the retrofit. This paper reports on a comparative study of the indoor environment in two adjacent classrooms, one renovated, and the other non-renovated. The aim of the study was to investigate the positive consequences of renovating lassrooms, but also to disclose unanticipated side-effects. The non-renovated classroom was without mechanical ventilation, fitted with woodwool ceiling plates for acoustics and lighting fixtures with horizontal illuminances of 200-300 lux on the tables. The renovated classroom was retrofitted with a new acoustic ceiling made from perforated gypsum tiles and suspended lighting fixtures and mechanical ventilation via decentral room unit mounted below the ceiling. The ventilation air was supplied in the void above the acoustic ceiling, which distributes air through perforations and joints in the ceiling to the occupied zone – a concept often referred to as diffuse ventilation. In this setup, the acoustic ceiling also acted as silencer for the ventilation inlet. Different indoor environmental parameters were comparatively measured in each classroom,including longterm CO2-concentration, temperature and noise levels as well as reverberation time and technical noise from the ventilation equipment. In all respects, the objective measurements improved in the renovated classroom.Interviews with pupils and questionnaire surveys were conducted, and – while showing less evidence of the improvements than expected – did indicate increased user satisfaction with the retrofit.

Daylight is a restricted resource in urban contexts. Rooms situated in an urban context often have a significant proportion of the sky and the sun blocked out by the urban building mass. The reduced direct daylight potential makes daylight reflected from outdoor surfaces an important daylight source to the room. It is therefore important to be able to take into account the daylight reflections from the urban environment in early design stage. This paper describes a simplified method that uses a combination of ray-tracing, the luminous exitance method and the concept of the urban canyon to represent daylight levels in rooms situated in an urban setting. The method is implemented in the daylight algorithm of an existing building simulation tool capable of making rapid integrated daylight and thermal simulation. Comparisons with the more sophisticated lighting tool Radiance show a maximum relative error of 17% but it is often much lower. The accuracy of this approach is therefore considered to be adequate for the early stages of the building design process. The results from integrated daylight and thermal simulations are presented to illustrate how the tool can be used to investigate the impact of urban canyon parameters on indoor environment and energy performance.

Heating, Ventilation and Air-Conditioning engineers face high demands from their clients to deliver reliable, optimized solutions that perform acceptably in terms of energy use and provided comfort. However, time and resources are scarce to deliver an optimized solution. To ensure that the solution works under most operation scenarios, the design is typically based on a combination of conservative rules-of-thumb, general guidelines and a large safety factor. The consequences are building service systems designed for operating conditions that never or very rarely occur leading to oversized systems. The objective of this paper was to propose a method for identifying oversized air-handling units with variable speed drives. It was demonstrated on a case study including six air-handling units in an office building. The method was able to determine that the air-handling units were not grossly oversized or undersized by comparing the measured airflow and SFP from the part- and full-load operation to the design airflow and SFP. However, the method should be extended to include additional performance criterion such as indoor climate and thermal efficiency to be able to conclusively confirm the size of the units.

This paper aims to document and analyse performance of a new design of diffuse ceiling ventilation system in a typical office room. A full scale measurement is carried out in a climate chamber with an office setup at the Technical University of Denmark. Indoor air temperatures, air speeds, wall surface temperatures, pressure loss of the ceiling and ventilation effectiveness are measured for an air change rate of 3.5 h−1 and 5.1 h−1 respectively. A computational fluid dynamics model of the office with the diffuse ceiling ventilation system is built and validated by the full scale measurement. The measurements of pressure loss across the ceiling show a low pressure drop between the plenum and the occupied zone. Ventilation effectiveness is measured to be close to 1 on average under the tested conditions. It is shown that the diffuse ceiling ventilation system is able to remove indoor pollutant in an efficient way. The draught risk is found to be insignificant by both experimental and theoretical investigations. A design chart based on “flow element” method is created for the diffuse ceiling ventilation system by calculations with the validated CFD model. The design chart serves as a guideline for design and dimension of the investigated diffuse ceiling terminals as an air distribution system.

An experimental study is reported in this paper for a diffuse ceiling ventilation concept. The analyses were carried out with two different porous surfaces mounted in a suspended ceiling: perforated tiles of aluminium and of gypsum. Ventilation air was supplied above the suspended ceiling effectively creating a plenum for air distribution. The experiments were carried out in a climatic chamber and documented an air change efficiency equal to fully mixed conditions with a pressure drop of 0.5–1.5 Pa and with no evidence of thermal discomfort. The magnitude of the pressure drop was enough to sustain the pressure of the plenum and ensure uni-directional airflow through the ceiling. Consequently only reverse flow of insignificant magnitude was observed which has a positive impact on the hygiene of the plenum. Furthermore, the measurements documented that the ceiling acts as a radiant cooling surface which increases the potential and applicability of the concept. Risk of thermal discomfort was not disclosed but the study did show evidence of large fluctuating air movements which could stem from transient behaviour creating sensations of draught to the occupants.

suspended ceiling to uniformly distribute the supply air to the occupied zone. This, in effect, increases the thermal mass of the room because the upper slab of the room no longer is isolated from the occupied zone.In this study, the cooling potential of a diffuse ceiling ventilation system isinvestigated by experiments focused toward characterizing the convective heattransfer of the plenum. The heat transfers are quantified from four different air flow rates, the temperature of the air supplied to the plenum and the mean surface temperature, i.e. the total heat transfer coefficient of the plenum.The established heat transfer coefficient is used for analysis of the cooling performance of the system in dynamic building simulation program which showed that during peak summer days, the scenario with ventilated plenum would exhibit temperatures in the occupied zone approx. 1-1.5 °C lower than the baseline with unventilated plenum.In conclusion this study disclosed the mean heat transfer of the plenum with an inlet jet of approx. 1.2-0.4 m/s and temperature differences of 0.5-4.5 °C and showed that ventilation supply through the plenum can be used to augment the night cooling potential.

A core element in sustainable ventilation systems is the heat recovery system. Conventional heat recovery systems have a high pressure drop that acts as blockage to naturally driven airflow. The heat recovery system we propose here consists of two separated air-to-liquid heat exchangers interconnected by a liquid loop powered by a pump ideal as a component in a heat recovery system for passive ventilation systems. This paper describes the analytical framework and the experimental development of one exchanger in the liquid-loop. The exchanger was constructed from the 8 mm plastic tubing that is commonly used in water-based floor-heating systems. The pressure loss and temperature exchange efficiency was measured. For a design airflow rate of 560 L/s, the pressure loss was 0.37 Pa and the efficiency was 75.6%. The experimental results agree well with the literature or numerical fluid calculations. Within the analytical framework, the total heat recovery of two liquid-coupled exchangers was calculated to be in the range 64.5–75.4%, depending on the parasitic heat loss in the experimental setup. The total pressure drop of the heat recovery system is 0.74 Pa. Moreover, preliminary improvement calculations promise a future total efficiency of 80% with a pressure drop of 1.2 Pa.

Appropriate window solutions are decisive for the design of ‘nearly zero-energy’ buildings with healthy and comfortable indoor environment. This paper focuses on the relationship between size, orientation and glazing properties of facade windows for different side-lit room geometries in Danish ‘nearly zero-energy’ houses. The effect of these parameters on space heating demand, daylighting and thermal environment is evaluated by means of EnergyPlus and DAYSIM and presented in charts illustrating how combinations of design parameters with minimum space heating demand can be selected within a solution space defined by targets for daylighting and thermal comfort. In contrast with existing guidelines, the results show an upper limit for energy savings and utilisation of solar gains in south-oriented rooms. Instead, low U-values are needed in both north- and south oriented rooms before large window areas lead to reductions in space heating demand. Furthermore, windows in south-oriented rooms have to be carefully designed to prevent overheating. Design options for prevention of overheating, however, correspond well with options for low space heating demand. Glazings with solar control coating are therefore obvious alternatives to dynamic solar shadings. Regarding room geometry, deep or narrow south-oriented rooms show difficulties in reaching sufficient daylight levels without overheating.

Variable air volume (VAV) ventilation systems reduce fan power consumption compared to constant air volume (CAV) systems because they supply air according to the airflow demand. However VAV ventilation systems do not take fully into account the potential energy savings as the control strategy operates the terminal boxes and the air handling unit (AHU) independently without pressure integration. The pressure in the main duct is maintained at a constant static pressure (CSP) which corresponds to the pressure required under the design full load condition. Under part load conditions, the fan provides excessive static pressure which is dissipated via throttling at the terminal boxes. As a result significant fan power is wasted in mechanical energy losses. The development of sophisticated direct digital controls (DDC) creates possibilities to integrate feedback from the dampers into the building management system. In this way the operation of central plant equipment is adjusted in real time according to the actual pressure demand; this control scheme can be implemented by the static pressure reset (SPR) method. The SPR control method ensures that at least one damper remains fully opened; thus the fan generates only enough pressure to satisfy the airflow demand in the most critical zone. Consequently the airflow resistance of the ductwork is maintained at a minimum and the fan operation is optimized. There are various approaches to implement the control scheme of the SPR method; the state of the art is represented by the method of trim and respond based on pressure alarms. This study investigates the operation of the SPR control method of trim and respond based on pressure alarms in a CO2 demand application where large air volumes are provided to three classrooms. The investigation was based on simulations performed with a fully dynamic model of a VAV ventilation system that was developed in the Simulink programming tool which is add-on software to MATLAB mathematical programming language. The Simulink model was developed in previous research work and was built based on the International Building Physics Toolbox (IBPT), which is a library of blocks constructed for the thermal analysis in building physics. For the purpose of the current investigation the IBPT toolbox was remodelled to integrate the calculation of the airflow demand based on the CO2 concentration occurring in the zone. The performance of the Simulink model was in previous work evaluated based on the experimental setup of a ventilation system. The investigation of the SPR control algorithm of trim and respond based on pressure alarms disclosed some issues that need to be addressed and optimized before the algorithm can effectively establish the pressure conditions that satisfy the pressure demand under high airflows. In short the algorithm must be tuned to the application beforehand or, preferably, actively learn to perform from continuous feedback before it presents a real plug-and-play solution.

Conventional control strategies in variable air volume (VAV) ventilation systems do not take fully into advantage the potential energy savings since the system operation is based on maintaining a constant static pressure (CSP) set point in the main duct irrespective of the actual pressure demand. The static pressure reset (SPR) control strategy can optimize the operation of the supply air fans by adjusting the pressure set point to be just enough to deliver the required airflow to the most critical zone.This study investigated the operation and energy savings potential of an SPR control algorithm by using the Simulink programming tool which is addonsoftware to MATLAB mathematical programming language. A model of a VAV ventilation system was created in Simulink based on the International Building Physics Toolbox (IBPT); the IBPT thermal zone was remodelled in order tocalculate dynamically the airflow demand according to the zone air temperature. The performance of the Simulink model was evaluated based on the experimental setup of the ventilation system. The SPR control method established stable system operation and was proven efficient to maintain comfortable space conditions while reducing by 14 % the fan energy used in a typical working day.

Diffuse ceiling ventilation is a novel air distribution device that combines the suspended acoustic ceiling with ventilation supply. A diffuse ceiling distributes the supply air above the acoustic tiles and has proven performance in laboratory experiments. To study the performance in real conditions a classroom was retrofitted with mechanical ventilation and a diffuse ceiling. The employed ceiling comprises active panels penetrable to air and impenetrable passive panels. The performance was studied with regard to air movements, temperatures and air change efficiency at two different air changes. The experiments were carried out during class to obtain realistic conditions. At both airflows did the ceiling perform satisfactorily with air movements and temperatures within the requirements of indoor climate standards. The air change efficiency is comparable to conventional mixing ventilation.

In building design the requirements for energy consumption for ventilation, heating and cooling and the requirements for increasingly better indoor climate are two opposing factors. This paper presents the schematic layout and simulation results of an innovative multifunctional ventilation concept with little energy consumption and with satisfying indoor climate. The concept is based on using passive measures like stack and wind driven ventilation, effective night cooling and low pressure loss heat recovery using two fluid coupled water-to-air heat exchangers developed at the Technical University of Denmark. Through building integration in high performance offices the system is optimized to incorporate multiple functions like heating, cooling and ventilation, thus saving the expenses of separate cooling and heating systems. The simulation results are derived using the state-of-the-art building simulation program ESP-r to model the heat and air flows and the results show the feasibility of the proposed ventilation concept in terms of low energy consumption and good indoor climate.

Building Information Modeling (BIM) is in the industry often confused with 3D-modeling regardless that the potential of modeling information goes way beyond performing clash detections on geometrical objects occupying the same physical space. Lately, several research projects have tried to change that by extending BIM with information using linked data technologies. However, when showing information alone the strong communication benefits of 3D are neglected, and a practical way of connecting the two worlds is currently missing.In this paper, we present a prototype of a visual query interface running in a web browser, that enables the user to gain a deeper understanding of what can be extracted from a Building Topology Ontology (BOT) knowledge base. The implementation enables the user to query the graph, and provides visual 3D-feedback along with simple table results.The main purpose of the paper is to establish a baseline for discussion of the general design choices that have been considered, and the developed application further serves as a proof of concept for combining BIM model data with a knowledge graph and potentially other sources of Linked Open Data, in a simple web interface.

A common technique to investigate draught problems in a room is to make spot measurements of air velocity. This might identify where the draught problem is located but it does not necessarily identify the distribution and source of the problem. Usually visual inspections of the location of ventilation inlet and smoke experiments are next step to track the draught source. However, these methods do not provide an understanding of the air flow pattern in the room with sufficient resolution to necessarily identify the source of the draught problem. However, laser light sheets together with smoke seeding for on-site visualization of airflow in rooms might be useful for tracking down draught sources in rooms as part of a commissioning process. This paper reports on the first attempts to use this simple method to visualize and characterize air flow patterns in two different classrooms. The visualizations disclosed the air movements, and it was possible to record the movements using a standard smartphone camera. From the movements it was possible to qualitatively assess the overall airflow patterns of the room. The resolution of the video recording was also sufficient to be processed in particle image velocimetry software to gain overall flow pattern visualization, if not accurate readings. The latter result indicates that there could be a potential for real-time velocimetry processing by smartphones but the method in general needs further investigation and documentation.

The W3C Linked Building Data on the Web community group is studying modeling approaches for the built environment using semantic web technologies. One outcome of this effort is a set of proposed ontologies together providing necessary terminology for the Architecture, Engineering, Construction and Operation (AECO) domains. In this paper, we demonstrate an integration between different datasets described using these ontologies in combination with the standard ontology for representing Sensors, Observations, Sampling, Actuation, and Sensor Networks (SSN/SOSA). In combination, the datasets cover the building's overall topology, 2D plan geometry, sensor and actuator locations and a log of their observations. We further suggest an integrated design approach that enables the designers to explicitly express the semantics of the sensors and actuators from the early stages of the project such that they can be carried on to construction and operation.

As part of European energy politics and strategies for reduction of fossil fuels all new buildings should have a “nearly zero” energy consumption in 2020. This creates a strong need for research in cost-effective technologies and solutions that will contribute to the fulfilment of the ambitious energy reductions without compromising desirable daylight conditions and indoor climate. This development requires knowledge about the demands and possibilities of the low energy building mass of the future. An important basis for the research within this field will therefore be the establishment of a set of reference parameters that can be expected to be representative for the behaviour of the “nearly zero” energy building of 2020 in different European climatic zones. This paper provides an overview of how single family houses with a very low energy demand for space heating and cooling can be approached by rational and conventional means in three different European climates: Rome, Bratislava and Copenhagen. Special attention is paid to the role of windows and their contribution to solar gains in these well-insulated buildings of the future. By a neutral treatment of the window configurations towards different orientations, where the windows in all rooms are dimensioned based on the diffuse daylight access at the specific location, it is shown that an equal window distribution will allow fulfilment of an ambitious energy target, while simultaneously enabling a balanced daylight access across the building and a comfortable indoor climate. Furthermore, the analyses indicate that the ability of these well-insulated buildings to utilise solar gains is highly restricted, even at the location of Copenhagen. Window panes with a solar control coating seem to be an appropriate protection against overheating for all three locations.