Buildings consume more than 30 percent of the primary energy worldwide with 65 percent of this attributed to heating ventilation and cooling. To help address this, stratified concrete panels (SCP) have been developed to provide insulation without compromising the thermal mass of concrete. SCP is created by vibrating a single concrete mix containing heavy and lightweight aggregates. Vibration causes the heavy aggregates drop to the bottom so that two distinct strata are formed; an internal structural/heavyweight layer providing thermal mass and an external lightweight layer for insulation. SCP incorporates waste products, for both financial and environmental gains, from which technical benefits also result. Stratified concrete panels have been made and tested during past research projects with results suggesting that SCP could be a competitive product in the residential construction industry, an area in which precast concrete systems have not been favoured in New Zealand. Consideration has been given to the specific rheological requirements of the concrete mix design and the hardened properties of the finished panels. This research considers the commercial viability of SCP using an industrial setting. For practicality of the setting, some materials were altered from past laboratory work to materials that are more easily sourced and better understood but with similar properties as those used previously. Several panels were cast at Stahlton precast yard in an effort to optimise the production process. Consistent results were not achieved and a range of stratification levels were produced. This showed that some capital investment is required to commercialise SCP to provide more energy for vibration such that sufficient stratification can be reliably attained. Two panels were then stood up in an exposed area with the exterior facing north to test for warping effects in a practical setting. No measurable warping occurred over this time which concurred with past work and long term readings that were taken of four year old panels. Structural, thermal and durability tests were carried out on panels with a range of stratification levels to assess the sensitivity of these properties to the level of stratification. From this it was found that the panels with better stratification had significantly better thermal properties than those with moderate to poor stratification. Generally the thermal targets for this project were not met with the total thermal resistance (R-values) not meeting current code requirements. In some cases structural properties were improved with better stratification as the structural layer was stronger through better consolidation. Delamination potential increased with stratification and with age. This requires further research to minimise this effect using fibres across the layer boundary. Porosity was increased in the structural layer in the poorly to moderately stratified panels as the structural layer was not consolidated enough due to lightweight aggregate contamination. As with any new innovation, market acceptance is largely governed by public perception. With appropriate marketing as a sustainable energy saving product, SCP has the potential to be competitive in the residential construction market with some capital investment.

In this dissertation, an increased thermal capacitance (ITC) and thermal storage management (TSM) system was simulated to reduce building energy consumption, specifically energy related to heating, cooling and domestic hot water. An increased thermal capacitance allows phase shift and amplitude reduction of heat flow fluctuations associated with the building’s internal temperature response due to weather. An adaptive allocation and control of the added capacitance through TSM significantly improves the benefits of the extra capacitance. This dissertation was conducted in three parts: (1) a first-order analysis of the ITC/TSM applied to a micro-building; (2) a transient simulation of the ITC/TSM with PCM implementation for tank volume control; and (3) a parameter study on the ITC/TSM system with added complexities such as the inclusion of DHW and a multiple story residential building. The first-order analysis was used for transient simulation comparison, as simple models are much more suitable for real time implementation in actual control systems. A first order study on a small residential building is also used to establish the merit of the ITC/TSM concept before integrating into a more complex analysis. This study determined that the ITC/TSM could potentially provide savings but required a very large thermal mass. The ITC/TSM system was then coupled with phase change materials (PCMs), which enable thermal energy storage volume reduction. The transient energy modeling software, TRNSYS, is used to simulate the building’s thermal response and energy consumption, as well as the ITC/TSM system and controls. Four temperature-controlled operating regimes are used for the ITC/TSM operations: building shell circulation, heat exchanger circulation, solar panel circulation, and storage. After this, 125 simulations were conducted to design and optimize the ITC/TSM. The three parameters of interest were: tank volume size, solar panel size, and mass flowrate. Domestic hot water usage was also included as another energy savings opportunity. Results for the parameter study showed that savings are optimized when the solar panel and the hot water tank are size together. If they are not sized simultaneously, the temperature of the large thermal capacitance is not adequately controlled. For all simulations conducted in the parameter study, the building energy usage was reduced significantly.

The single family housing sector currently accounts for approximately 15% (US DOE 2002) of the total national energy consumption with the majority of the energy use associated with the HVAC system to provide comfort for the residents. In response to recent concern over the unpredictability of the energy supply and the pollution associated with its consumption, new methods are constantly being developed to improve the energy efficiency of homes. A variety of concrete wall systems including Multi-functional Precast Panel (MPP) systems and Insulating Concrete Form (ICF) systems have been proposed to not only improve the building envelope thermal performance but other important residential characteristics such as durability and disaster and fire resistance. MPPs consist of Precast Concrete Panels (PCPs) that incorporate structural elements, interior and exterior finishes, insulation, and even heating/cooling systems into a single manufactured building panel. The ICF system is a cast-in-place concrete panel system that does not offer the level of integration found in the MPP system but has become increasingly accepted in the building construction industry. This research evaluates the thermal performance benefits of concrete wall systems in detached, single family home applications. The thermal performance benefits of two MPP systems and an ICF system are analyzed within the context of a representative or prototypical home in the U.S. and are compared to two wood frame systems; one representing a typical configuration and the other an energy efficient configuration. A whole wall approach is used to incorporate the two and three dimensional conduction and transient characteristics of the entire wall assembly, including the clear wall and wall detail regions, into a whole building simulation of the prototypical house. The prototypical house heating and cooling energy consumption associated with each wall system is determined for six representative climates throughout the U.S. to evaluate the effect of various ambient conditions on the relative energy savings. For each wall system, the effect of thermal bridging on overall R value, the effect of thermal capacitance, and the role of infiltration on energy use are investigated. The results of the research include a comparison of the prototypical house energy savings associated with each of the wall systems; an assessment of the relative importance of the increased insulation, thermal mass, and improved air tightness on the overall energy load; and a comparison of the cost of ownership for the various wall systems. The results indicate that properly designed concrete wall systems can reduce annual heating and cooling costs. In addition, the results show that the most significant impacts of improved wall systems are, from greatest to least: infiltration reduction, improved insulation configuration, and thermal capacitance. Finally, the results show that while there are energy savings associated with concrete wall systems, economic justification of these systems must also rely on the other attractive features of concrete systems such as greater durability and disaster resistance. / Master of Science

This thesis describes the influence of thermal mass on the space conditioning energy consumption and indoor comfort conditions of multi-storey buildings with concrete, steel and timber structural systems. The buildings studied were medium sized educational and commercial buildings. When calculating a building’s life-cycle energy consumption, the construction materials have a direct effect on not only the building’s embodied energy but also on the space conditioning energy. The latter depends, amongst other things, on the thermal characteristics of the building’s materials; thermal mass can also be an influence on comfort conditions in the building. A modelling comparison has been undertaken between three very similar medium-sized buildings, each designed using structural systems made primarily of timber, concrete and steel. The post-tensioned timber version of the building is a modelled representation of a real three-storey educational building that has been constructed recently in Nelson, New Zealand. The concrete- and steel-structured versions have been designed on paper to conform to the required structural codes and meet, as closely as possible, the same performance, internal space layout and external façade features as the real timber-structured building. Each of these three structurally-different buildings has been modelled with two different thermal envelopes (code-compliant and New Zealand best-practice) using a heating, ventilating and air conditioning (HVAC) system with heating only (educational scheme) and heating and cooling (commercial scheme). The commercial system (with cooling) was applied only to the buildings with the best-practice thermal envelope. The analysis of each of these nine different construction and usage categories includes the modelling of operational energy use with an emphasis on HVAC energy consumption, and the assessment of indoor comfort conditions using predicted mean vote (PMV). From an operational energy use perspective, the modelling comparison between the different cases has shown that, within each category (code-compliant, low-energy and low-energy-commercial), the principal structural material has only a small effect on overall performance. The most significant differences are in the building with the best-practice thermal envelope with the commercial HVAC system, were the concrete building has slightly lower HVAC energy consumption, being 3 and 4% lower than in the steel and timber buildings respectively The assessment of indoor comfort conditions during occupied periods through using PMV for each of the three categories shows that the timber structure consistently exhibited longer periods in the over-warm comfort zone, but this was much less pronounced in south-facing spaces. To examine the reasons for the less acceptable PMV in the timber-structure versions, an analysis of indoor timber and concrete surface temperatures was carried out in both buildings. It was found that, particularly in north-facing spaces, there were large diurnal swings in the temperatures of timber surfaces exposed to solar radiation. These swings were much less in the case of concrete surfaces so the environment was perceived to be more comfortable under such conditions because of the reduced influence of higher mean radiant temperatures. To moderate this potential downside of solar-exposed internal timber surfaces, better results are achieved if, when timber is used for thermal mass, the timber is not exposed to direct solar radiation, for example locating it in the ceilings or on the south side of the building. Two other approaches to combating the potential overheating problem in the timber-structured buildings were analysed in an illustrative mode; addition of external louvres to reduce direct solar gains at critical times of day and year; and use of phase change material (PCM) linings to act as light-mass energy buffers. Although external louvres increase comfort conditions significantly by reducing the periods of an overly warm environment, they produce an increase in heating energy consumption through reducing beneficial solar gains. The use of PCM linings shows little benefit to overall indoor comfort conditions for the building of this case-study.

Thermal mass can be used in buildings to reduce the need for and dependence on mechanical heating and cooling systems whilst maintaining environmental comfort. Active thermal mass strategies further enhance the performance of thermal mass through integration with the Heating, Ventilation and Air Conditioning (HVAC) systems. For the design of new buildings to include active thermal mass strategies, experience from operational projects and design guidelines are normally used by engineers. However, dynamic thermal modelling is required in most cases to accurately determine the performance of its integration with the environmental systems of the building. Design decisions made in the preliminary stages of the design of a building often determine its final thermal characteristics. At this stage, reasons for not integrating active thermal mass strategies include the lack of knowledge about the performance of previous buildings and the time and resources required to carry out detailed modelling. In this research project a commercially available dynamic building thermal program has been used to construct models for active thermal mass strategies and compare the results with monitored temperatures in buildings incorporating the strategies in the UK. Four active thermal mass strategies are considered (a) hollow core slabs (HCS), (b) floor void with mass, (FVWM) (c) earth-to-air heat exchanger (ETAHE) and (d) thermal labyrinth (TL). The operational strategies and monitoring are presented and their modelling is described in terms of geometrical configuration and input parameters. The modelling results are compared with the measured parameters successfully. Using the calibrated model, an excel based tool (TMAir) was then developed that can be used at the concept design stages of a typical office building to determine the benefits of integrating an active thermal mass strategy. Key design parameters were identified for each system. These parameters can be split into two categories; fixed parameters and user selected parameters. The fixed parameters are pre-selected for the design tool and have to be a fair representation of the projects that the tool will be used for. The user selected parameters are chosen by the user to represent the way the building will be used, and to look at the effect of key design decisions on the performance of the building. The tool has an easy-to-use interface which allows direct comparison of the different active thermal mass strategies together with the effects of changing key design parameters. Results are presented in terms of thermal comfort and energy consumption. TMAir has then been used to carry out a series of parametric analyses. These have concluded the following:  There is only a benefit in integrating a HCS strategy when night cooling is introduced  There is no benefit in integrating a FVWM strategy when only one parameter is improved  An ETAHE and TL strategy will always provide a benefit, although the benefits are greater when night cooling is introduced, solar and internal gains are reduced and when the air change rate is increased. When all of the parametric improvements are applied to the test room the results show that all of the active thermal mass strategies can provide a reduction in annual overheating hours when compared to the Standard Strategy. Only a small benefit is found for the FVWM Strategy, however around a 25% reduction is found for the HCS Strategy, over a 50% reduction for the TL Strategy and nearly a 75% reduction for the ETAHE Strategy. This demonstrates the importance of applying a low energy, passive approach when considering the application of active thermal mass strategies. The key results have shown that when comfort cooling is provided, adding a HCS or FVWM strategy always results in an increase in the annual cooling load. This is as a result of the temperature of the air being supplied into the cores or floor void being higher than that of the internal surface temperatures of the cores or void. This results in the supply air being heated, and less cooling provided to the test room per cooling energy delivered. Due to the pre cooling effect of the ETAHE and TL strategies, these strategies always result in a reduction in the annual cooling load. The key results have shown that the annual heating load is reduced by a small amount for the HCS and FVWM strategies unless the solar gains or internal gains are reduced, whereas the ETAHE and TL strategies always result in a around a 10% reduction in annual heating load as a result of the preheating effect these strategies have on the supply air.

abstract: Passive cooling designs & technologies offer great promise to lower energy use in buildings. Though the working principles of these designs and technologies are well understood, simplified tools to quantitatively evaluate their performance are lacking. Cooling by night ventilation, which is the topic of this research, is one of the well known passive cooling technologies. The building's thermal mass can be cooled at night by ventilating the inside of the space with the relatively lower outdoor air temperatures, thereby maintaining lower indoor temperatures during the warmer daytime period. Numerous studies, both experimental and theoretical, have been performed and have shown the effectiveness of the method to significantly reduce air conditioning loads or improve comfort levels in those climates where the night time ambient air temperature drops below that of the indoor air. The impact of widespread adoption of night ventilation cooling can be substantial, given the large fraction of energy consumed by air conditioning of buildings (about 12-13% of the total electricity use in U.S. buildings). Night ventilation is relatively easy to implement with minimal design changes to existing buildings. Contemporary mathematical models to evaluate the performance of night ventilation are embedded in detailed whole building simulation tools which require a certain amount of expertise and is a time consuming approach. This research proposes a methodology incorporating two models, Heat Transfer model and Thermal Network model, to evaluate the effectiveness of night ventilation. This methodology is easier to use and the run time to evaluate the results is faster. Both these models are approximations of thermal coupling between thermal mass and night ventilation in buildings. These models are modifications of existing approaches meant to model dynamic thermal response in buildings subject to natural ventilation. Effectiveness of night ventilation was quantified by a parameter called the Discomfort Reduction Factor (DRF) which is the index of reduction of occupant discomfort levels during the day time from night ventilation. Daily and Monthly DRFs are calculated for two climate zones and three building heat capacities. It is verified that night ventilation is effective in seasons and regions when day temperatures are between 30 oC and 36 oC and night temperatures are below 20 oC. The accuracy of these models may be lower than using a detailed simulation program but the loss in accuracy in using these tools more than compensates for the insights provided and better transparency in the analysis approach and results obtained. / Dissertation/Thesis / M.S. Mechanical Engineering 2011

Published Article / The purpose of this paper is to analyse the thermal performance of two buildings. The one has a large thermal mass and the other a highly insulated low thermal mass. A typical 120 m2 suburban building was modelled in Ecotect. As part of the model infiltration rate, wind sensitivity and a central Pretoria weather file were used. New material composites were introduced in the materials database to represent typical building materials used in the construction of heavy and light-weight buildings in South Africa. The thermal characteristics of these new materials were then calculated within Ecotect. Ecomat was used to calculate thermal lag which was used as an additional input into Ecotect. The research indicates that a low thermal mass and highly insulated building have been shown to use 18.3% less annual space heating and cooling energy when compared to the high thermal mass building. The good thermal performance results of the light-weight building will help in clearing scepticism to adopting this construction technology in southern Africa where high thermal mass masonry is still predominant.

Patterned resistive sheets (PRS) are resistive sheets with periodic patterns which provide further advantages to the functionality of the microbolometer. This study examines the potential of both single- and double-layer designs to achieve spectral selectivity in both broadband and narrowband absorption in the microbolometer's application. First, important design parameters, including rules and processes, are established. These include descriptions of sheet resistance, air gap, material refractive index, thicknesses of dielectric and bolometric layers, mirror, pattern shape and size, and unit cell period. Moreover, interactions among these elements are examined. Second, single-layer designs using dipole and slot PRS are introduced as initial designs for the reduced thermal mass design. Applying holes without changing spectral selectivity are investigated for narrowband application. Moreover, the method to tune the change of spectral selectivity is introduced. Third, newly stacked two-color design is suggested. The out-of-band transmission and reflection characteristics of the dipole and slot PRS are investigated to increase the absorption of each layer. Additionally, different pattern shapes, such as the circular patch and square patch, are investigated for easier fabrication. / text

Environmental consciousness leads the construction industry to greater concerns about local adaptation, less waste of resources and energy efficiency In Brazil, earth construction is a feasible approach to house building in many locations and can play a useful part in resolving the housing problems faced by that country, being already a popular approach to providing affordable housing for low income groups within the population, particularly in the Northeast Region of the country, although usually not built correctly. Although used since the colonial period, from 1500, knowledge around earth systems is not formally embedded within the Brazilian building standards and this is unhelpful in terms of promoting quality of performance of buildings thus constructed. For example, appropriate use of high thermal mass in conjunction with natural ventilation, which is frequently used in Brazil due to energy costs, can significantly influence the thermal comfort within residences, but appropriate guidance is lacking. This research considers the combined effects of earth construction and natural ventilation upon thermal comfort within social housing in Northeast Brazil. The main thesis hypothesis is that the use of thermal mass provided by earth construction combined with natural ventilation results in acceptable levels of thermal performance with respect to thermal comfort in both hot and humid and hot and dry climates. The aim is to evaluate the thermal performance of high thermal mass dwellings using adobe system combined with natural ventilation in the bioclimatic zones of Brazil's Northeast Region. The method explores thermal performance simulation using Design Builder, a graphical interface for Energy Plus program. The assessment uses parametric analysis and the adaptive thermal comfort index from de Dear and Brager (1998). The results suggest that earth construction provides a high number of comfort hours in all bioclimatic zones in Northeast Brazil and ventilation use enhances the comfort sensation.

<p>The main objectives of this thesis have been to evaluate how, under which premises, and to what extent building thermal mass can contribute to reduce the net energy demand in office buildings. The thesis also assesses the potential thermal environmental benefits of utilizing thermal mass in office buildings, i.e. reduction of temperature peaks, reduction of temperature swings, and the reduction in the number of hours with excessive operative temperatures. This has been done by literature searches, and experimental and analytical assessments. This thesis mainly concerns office buildings in the Norwegian climate. However, the methods used and the results obtained from this work are transferable to other countries with similar climates and building codes.</p><p>Within the limitations of this thesis and based on the findings from all parts and papers this thesis comprises, it is shown that utilization of thermal mass in office buildings reduces the daytime peak temperature, reduces the diurnal temperature swing, decreases the number of hours with excessive temperatures, and increases the ability of a space to handle daytime heat loads. Exposed thermal mass also contributes to decrease the net cooling demand in buildings. However, thermal mass is found to have only a minor influence on the heating demand in office buildings.</p><p>The quantity of the achievements is dependent on the amount of exposed thermal mass, night ventilation strategy, and airflow rates. In addition, parameters such as set point temperatures, control ranges, occupancy patterns, daytime ventilation airflow rates, and prevailing convection regimes are influential for the achieved result. The importance of these parameters are quantified and discussed.</p> / <p>Hovedmålene med denne avhandlingen har vært å evaluere hvordan, under hvilke forutsetninger og i hvilken utstrekning termisk masse kan bidra til å redusere netto energibehov i kontorbygninger. Avhandlingen vurderer også hvilke potensielle fordeler termisk masse har for det termiske inneklimaet, dvs. reduksjon av maksimumstemperatur, temperatursvingninger og antall timer med overtemperaturer. Disse undersøkelsene er gjort gjennom søk i litteraturen, feltstudier og analytiske metoder. Avhandlingen omfatter i hovedsak kontorbygninger under norske forhold, men metodene og resultatene er overførbare til andre land med sammenlignbare klimatiske forhold og byggeskikk.</p><p>Innenfor avgrensningene gjort i avhandlingen og basert funnene i de ulike delene og artiklene avhandlingen består av, er det vist at utnyttelse av termisk masse i kontorbygg bidrar til å redusere netto energibehov. Termisk masse reduserer også maksimumstemperaturen dagtid, demper temperaturvariasjonene over døgnet og reduserer antall timer med overtemperaturer. Utnyttelse av termisk masse bidrar også til at rom kan tåle en høyere intern varmelast enn lette rom uten at dette går ut over den termiske komforten. Termisk masse har imidlertid liten betydning for energibehovet for oppvarming i kontorbygg.</p><p>Gevinsten med å utnytte termisk masse avhenger av tilgjengeligheten av eksponerte tunge materialer, strategi for nattventilasjon og ventilasjonsluftmengder. I tillegg innvirker parametere som settpunkttemperaturer, dødbånd og kontrollintervaller for ventilasjonen og bruksmønster. Innvirkningen av disse parametrene er diskutert og kvantifisert.</p>