Sandwich elements are widely used in the building envelope, in walls and foundations in particular. The thickness of sandwich elements is increasing as the demand for reduced heat loss from the building envelope is required. The building industry is searching for means and alternative materials to reduce the volume of the building envelope, but at the same time obtain the same thermal performance. Sandwich element constructions might be suitable for highly effective insulation materials as VIPs (Vacuum Insulation Panels). The possibilities of optimizing the thermal performance and by the same time decreasing the thickness and reducing the volume of aggregated clay sandwich construction block systems with VIPs has been investigated. Numerical simulations with heat conduction models and also CFD-models have been performed in order to study the optimal design of the block, the influence of thermal bridges and the influence of vertical and horizontal joints on the thermal performance of a wall. The work has resulted in an optimal design for a prototype block which has been produced and general knowledge about the influence of convection in vertical joints. The simulations show that for vertical joints less than 3 mm in width there will be no significant heat transport by convection. The numerical simulations also show that an U-value of 0,08 W/m2K can be achieved for such a system, with a thickness of the block being 300 mm. The work was carried out in the framework of the Norwegian centre for Zero Emission Buildings (ZEB).

In order to reach the goal of a zero emission building (ZEB), CO2 emission data has to be made available and verified for traditional building materials, new ‘state-of-the-art’ building materials and the active elements used to produce renewable energy. However, an initial literature review found that although there are databases of embodied carbon values for most building materials, the range in results for some materials are varied and inconsistent.

This paper follows on from previous work on the development of a transparent and robust method to calculate CO2eq emissions of the materials used in the concept analysis of the ZEB residential model, single family house. The aim of the concept analysis was to investigate if it was possible to achieve an "all-electric" ZEB-building by balancing operational and embodied emissions by PV-production on the building. The analysis has not considered minimising the embodied emissions but is rather a documentation of the embodied carbon dioxide emissions using traditional materials in the envelope and in the ventilation and heating systems, as well as, those associated with the renewable energy system, such as the photovoltaic panels and solar thermal collectors. Material inventories have been imported from the Revit BIM model, via MS Excel. The material inputs are structured according to the Norwegian table of building
elements, NS 3451-2009 and emission factors (kgCO2eq per functional unit) for the calculations are sourced from SIMAPRO/ Ecoinvent version 2.2.

The goal of these calculations is to estimate, and thus provide an overview of the materials and components in the ZEB residential model, which contribute the most to the embodied carbon dioxide emissions. The calculations are based on the principles of environmental assessment through life cycle analysis. It should be noted that in this first round of calculations, not all life cycle phases are included. In the next stage of the calculations, the model will be optimised and the impact on emissions recalculated accordingly

Abstract

The building envelope plays a crucial role in reducing operational energy demand. In particular, the two main properties of the building envelope to look at in this perspective are thermal transmittance (U, W/m2K1) and thermal inertia, which is often expressed by a metric called periodic thermal transmittance (Yie, W/m2K1). These two properties are also traditionally connected to two different energy demands: while thermal transmittance is crucial to reduce heating energy demand, thermal inertia has an impact on energy demand for cooling. However, a question may rise about the impact of each property on the other demand – i.e. the impact of thermal insulation on the cooling energy demand and the impact of thermal inertia on the heating demand.
A parametric analysis on the influence of the thermal inertia on the energy performance of a single family house in a Nordic climate has been carried out to find an answer to this question. “Ideal envelopes” have been modelled and simulated, meaning that used thermophysical properties do not represent any configuration, but the entire spectrum of technological configurations.
The results show that the influence of the thermal inertia on the heating energy need is very limited. Even a relatively high value of Yie, which means no or little thermal inertia, does not determine a significant increase in energy need. Parallel to this, solutions characterized by very high thermal inertia do not allow heating energy demand to be sensibly decreased. Periodic thermal transmittance has instead an impact on the heating load. The impact of the thermal inertia is also assessed in the warmer season, and the results show that this parameter does not significantly contribute to a better behavior (especially when the upper limit of the indoor air temperature is controlled). Limitations to value of thermal transmittance are also pointed out to avoid non-energy effective conditions when the total (heating plus cooling) annual performance is considered.

Abstract

The building envelope plays a crucial role in reducing operational energy demand. In particular, the two main properties of the building envelope to look at in this perspective are thermal transmittance (U, W/m2K1) and thermal inertia, which is often expressed by a metric called periodic thermal transmittance (Yie, W/m2K1). These two properties are also traditionally connected to two different energy demands: while thermal transmittance is crucial to reduce heating energy demand, thermal inertia has an impact on energy demand for cooling. However, a question may rise about the impact of each property on the other demand – i.e. the impact of thermal insulation on the cooling energy demand and the impact of thermal inertia on the heating demand.
A parametric analysis on the influence of the thermal inertia on the energy performance of a single family house in a Nordic climate has been carried out to find an answer to this question. “Ideal envelopes” have been modelled and simulated, meaning that used thermophysical properties do not represent any configuration, but the entire spectrum of technological configurations.
The results show that the influence of the thermal inertia on the heating energy need is very limited. Even a relatively high value of Yie, which means no or little thermal inertia, does not determine a significant increase in energy need. Parallel to this, solutions characterized by very high thermal inertia do not allow heating energy demand to be sensibly decreased. Periodic thermal transmittance has instead an impact on the heating load. The impact of the thermal inertia is also assessed in the warmer season, and the results show that this parameter does not significantly contribute to a better behavior (especially when the upper limit of the indoor air temperature is controlled). Limitations to value of thermal transmittance are also pointed out to avoid non-energy effective conditions when the total (heating plus cooling) annual performance is considered.

Abstract

Introduction of more dynamic building envelope components have been done throughout the last decades in order to try to increase indoor thermal comfort and reduce energy need in buildings for both temperature and light control. One of these promising technologies is phase change materials (PCM), where, the latent heat storage potential of the transition between solid and liquid state of a material is utilized as thermal mass. A PCM layer incorporated in a transparent component can increase the possibilities to harvest energy from solar radiation by reducing the heating/cooling demand and still allowing the utilization of daylight. The introduction of dynamic components in the building envelope makes the characterization of conventional static performance indices insufficient in giving a clear picture of the performance of the component in question.
Measurements have been performed on a state-of-the-art window that integrates PCM using a large scale climate simulator. The glazing unit consists of a four-pane glazing with an integrated layer that dynamically controls the solar transmittance (prismatic glass) in the outer glazing cavity. The innermost cavity is filled with a phase change material.
This article presents and assesses the series of measurements and the related methodologies with the aim of investigating the thermal behavior and thermal mass activation of the PCM-filled window. The experiments have been carried out using several static and dynamic test cycles comprised of temperature and solar radiation cycling. A conventional double-pane window has also been experimental investigated using the same test cycles for reference purpose.
It was found that even for temperatures similar to a warm day in Nordic climate, the potential latent heat storage capacity of the PCM was fully activated, but relatively long periods of sun combined with high exterior temperatures are needed.