Abstract
In highly-insulated buildings such as passive houses, the space-heating distribution subsystem can be simplified by reducing the number of heat emitters. In this context, the bi-directional flow through open doorways is known to be an efficient process to support the heat distribution between rooms. This process is therefore investigated using field measurements within a Norwegian passive house. The so-called large opening approximation proves to model fairly the mass flow rate, but also the convective heat transfer if the thermal stratification is accounted for. Furthermore, the discharge coefficient appears to be independent of the heater type and location in the room.
ABSTRACT
Space-heating using wood stove is a popular solution in many European countries. Nevertheless, nominal powers of state-of-the-art stoves are oversized compared to the needs of highly-insulated building envelopes, such as passive houses. In this respect, a simplified wood stove model has been developed in order to investigate the thermal comfort using detailed dynamic simulations (e.g. TRNSYS) at an acceptable computational cost. A specific experimental setup has been developed to validate this modelling procedure, especially as regards the interaction between the stove and the building. The largest source of error appears to be the thermal stratification in the room where the stove is placed. This can simultaneously affect the conductive heat transfer between rooms, the thermal comfort sensation in the room as well as the convective heat exchange by flows through doorways. Nonetheless, the present work proposes a correction to circumvent this last effect. Finally, thermal comfort measurements during the experimental campaign confirm the conclusions of previous simulation results (Georges, Skreiberg, & Novakovic, 2014), supporting their proposed guidelines for the integration of wood stoves in passive houses.
Abstract
Modeling simplification related to occupant’s behavior is a major cause of gap between actual and model’s predicted energy use of buildings. This paper aims to identify those parameters of realistic occupants-related heat gains that actually cause this gap. The investigation therefore, systematically distinguishes the occupant behavior using three behavior parameters, namely: the occupancy behavior, the appliance use behavior and the family size. The effect of these parameters is investigated on a building for two different insulation standards using heat pump as energy supply system. The results identifies the occupancy patterns and the household size as two major parameters that explains a large portion of the gap between actual and model’s predicted energy use of the building. Results further show that variation in household sizes is an important parameter to understand the variation in the actual energy use for similar buildings. The study also shows a clear influence of occupant’s behavior on the performance of heat pumps and pinpoints the variations in share of space heating needs compared to domestic hot water needs as a major cause for this influence. Sensitivity of findings is tested against building thermal mass and condensing gas boiler. Analysis shows no significant variations in the conclusions. The study therefore concludes that using identified parameters in modeling practices can contribute to improve the prediction of actual energy use of buildings.
Abstract
The net-zero emissions building (nZEB) performance is investigated for building operation (EO) and embodied emissions in materials (EE) for Norway's cold climate. nZEB concepts for new residential and office buildings are conceived in order to understand the balance and implications between operational and embodied emissions over the building's life. The main drivers for the CO2 equivalent (CO2e) emissions are revealed for both building concepts through a detailed emissions calculation. The influence of the CO2e factor for electricity is emphasized and it is shown to have significant impact on the temporal evolution of the overall CO2e emissions balance. The results show that the criterion for zero emissions in operation is easily reached for both nZEB concepts (independent of the CO2e factor considered). Embodied emissions are significant compared to operational emissions. It was found that an overall emissions balance including both operational and embodied energy is difficult to reach and would be unobtainable in a scenario of low carbon electricity from the grid. In this particular scenario, the net balance of emissions alone is nonetheless not a sufficient performance indicator for nZEB.
This report deals with how to define what a Zero Emission Building (ZEB) is with explanation and analysis of different parameters related to embodied emissions of CO2 equivalents. The report can be used as a guidance tool on how to assess embodied emissions, and also on what parameters should be evaluated in such an assessment.
Different ambition levels for ZEBs may include life stages, operation, material, construction and end-of-life and can be documented according to EN 15978. Calculation procedures should include system boundaries, embodied emissions from materials, transport, the construction process and waste handling according to the ambition level. CO2 eq emissions factors, service life estimates and payback scenarios for CO2 emissions need to be considered.
The report does not contain one single clearly defined method, but rather a state-of-the-art summary on the different issues and refers to other relevant national and international work in the field of ZEB definitions. The issues presented here are in early stages of development and will need to be verified and further developed.
The paper aims to investigate whether it is possible to achieve a net Zero Emission Building (nZEB) by balancing emissions from the energy used for operation and embodied emissions from materials with those from on-site renewables in the cold climate of Norway. The residential nZEB concept is a so-called all-electric solution where essentially a well-insulated envelope is heated using a heat pump and where photovoltaic panels (PV) production is used to achieve the CO2eq balance. In addition, the main drivers for the emissions are revealed through the CO2eq calculation for a typical Norwegian, single-family house. This concept building provides a benchmark rather than an absolute optimum or an architectural expression of future nZEBs. The main result of this work shows that the criteria for zero emissions in operation (ZEB-O) is easily met, however, it was found that the only use of roof mounted PV production is critical to counterbalance emissions from both operation and materials (ZEB-OM). The results show that the single-family house has a net export to the electric grid with a need for import only during the coldest months. In the next stage of the work, the concept will be further optimised and the evaluation method improved.
The German definition of the passive house standard is strongly related to the air-heating (AH) concept, while this concept is not explicitly connected with the Norwegian definition (NS 3700 standard). As AH presents an opportunity for space-heating (SH) simplification, the AH potential is here investigated in the Norwegian context. The questions of the required AH temperatures, of the temperature distribution between rooms and the influence of losses from ventilation ducts are investigated using detailed dynamic simulations (here using TRNSYS). This is done using a typical detached house typology, both considering different building construction materials as well as different climate zones (Oslo, Bergen and Karasjok). Simulation results present the potential and limitation of the AH for this common building typology but also enable to derive guidelines for the proper design of AH systems in Nordic conditions. For example, the standard SH design conditions (STD) appear to be the most severe conditions in term of AH temperatures and uneven temperature distribution between rooms.