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The transient plane source (TPS) technique, also referred as the Hot Disk method, has been widely used due to its ability to measure the thermal properties of an extensive range of materials (solids, liquids, and powder). Recently, it has been recognized that typical Hot Disk sensors can influence TPS results of thermally insulating materials and lead to an overestimation of thermal conductivity. Although improvements have been proposed, they have not yet been implemented in the commercial TPS, leaving researchers with non-standardized modifications or options provided by a commercial Hot Disk apparatus. An empirical study of thermally insulating materials such as extruded polystyrene (XPS) and aerogel blanket is conducted in order to address the factors that affect the reliability of thermal conductivity k obtained using the commercial TPS apparatus. Sensor size, input power, duration of the measurements, applied pressure, and, in the case of anisotropic materials, heat capacity are investigated, and the results are compared with those using a Heat Flow Meter apparatus. The effect of sensor size on the k value is ascribed to heat loss through connecting leads and is more pronounced in smaller sensors and in materials with lower k values. In the case of XPS and aerogel, the effect becomes minimal for sensors with a radius r ≥ 6.4 mm. The low input power yields a high scattering of the results and should be avoided. Applied contact pressure and the tested region of the specimen play an important role in experiments with low-density fibrous materials due to the large percentage of heat being transferred by radiation and the heterogeneous nature of the samples, respectively. Additionally, the sensitivity of anisotropic measurements to the value of the material’s volumetric heat capacity (ρCp) is shown, emphasizing the need for the precise determination.

This research article explores the behavior of a phase change material (PCM) when it undergoes interrupted melting and freezing, through experimental investigations using a heat flow meter apparatus. A fatty acid-based organic PCM, encapsulated within polyethylene and thin aluminum foil layers, was experimentally tested in this study. Experiments were designed to represent multiple interrupted phase change scenarios that could occur within PCMs applied in buildings. The experimental results were analyzed and compared with previously reported assumptions in numerical models dealing with PCM hysteresis and interrupted phase change processes. These comparisons indicated that the assumptions used in the different numerical models considered can capture the interrupted phase change phenomena with varying degrees of accuracy. The findings also highlighted the need for additional experimental research on different phase change processes that can occur in building applications of PCMs.

Experimental investigations and numerical analyses were conducted on the thermal attributes of a building system made with locally available structural and insulation materials. The structural material, which also offers some insulation qualities, is referred to as aerated slurry-infiltrated mesh. The insulation materials used in this building are based on biomass; the alternatives considered here include ground wood, shredded straw, and cellulose. Thermal conductivity tests were performed on aerated slurries of different bulk densities, and on the biomass-based insulation materials, some of which were prepared with different bulk densities. The competitive merits of the biomass-based indigenous insulation materials were assessed. The correlations between bulk density and thermal conductivity were evaluated and rationalized based on the prevalent mechanisms of heat transfer in different materials. The effects of temperature on the thermal conductivity of different biomass-based indigenous insulation materials were investigated. For wall insulation, a cost analysis was conducted in order to select the optimum insulation level. The thermal mass of the aerated slurry-infiltrated mesh building system was found to favor its energy-efficiency when compared with a similar wood building.

Manipulating thermal conductivity through nanoengineering is of critical importance to advance technologies, such as soft robotics, artificial skin, wearable electronics, batteries, thermal insulation, and thermoelectrics. Here, by examining amorphous polymers, including polystyrene, polypropylene, polyethylene, and ethylene vinyl alcohol, using molecular dynamics simulations, we find that the thermal conductivities of amorphous polymers can be reduced below their amorphous limit by size effects. Size-dependent thermal transport in amorphous materials is decomposed into crystalline, crystalline-to-amorphous, and amorphous regimes. In the amorphous regime, the mean free path of propagating heat carriers can range from tens of nanometers to more than 100 nm, contributing 16%--36% of the total thermal conductivity. A two-channel model that combines no size effect (i.e., difusons and locons) and size effect (i.e., propagons) is proposed to account for size-dependent thermal conductivity. We also find that the presence of charged molecules in polymers can significantly affect the thermal conductivity and its size effects due to electrostatic interactions. This work provides insights into the thermal conductivity of amorphous polymers that will have a broad impact on the nano- and chemical engineering of polymers for various energy-related applications.

This paper presents the energy savings potential of a newly developed liner applied on the foam insulation used in refrigerator and freezer cabinets, compared with using a more commonly used liner made from high-impact polystyrene. The new polylactic acid polymer liner is made from renewable feedstock such as carbon found in plant sugars. The energy use over the life of refrigerator and freezer is calculated using the Energy-Efficient Refrigerator Analysis program developed by the United States Department of Energy to estimate the energy savings potential of various technology option upgrades (cabinet and refrigeration system) for rulemaking purposes. The simulation results show that energy savings from implementing the Ingeo liner range from 818 to 1395 kWh (7.3–12.5% of total energy use) over a 15-year period. In addition to the energy savings, the slower increase in the thermal conductivity of the insulation could allow the compressor to run fewer hours per year compared with a case in which the foam thermal conductivity increases rapidly. This change could increase the life of the compressor and the refrigerators and freezers. This study does not attempt to quantify the impact of slower foam aging on the compressor life.

Nano-size confinement induces many intriguing non-Fourier heat conduction phenomena, such as nonlinear temperature gradients, temperature jumps near the contacts, and size-dependent thermal conductivity. Over the past decades, these effects have been studied and interpreted by nonequilibrium molecular dynamics (NEMD) and phonon Boltzmann transport equation (BTE) simulations separately, but no theory that unifies these two methods has ever been established. In this work, we unify these methods using a quantitative mode-level comparison and demonstrate that they are equivalent for various thermostats. We show that different thermostats result in different non-Fourier thermal transport characteristics due to the different mode-level phonon excitations inside the thermostats, which explains the different size-dependent thermal conductivities calculated using different reservoirs, even though they give the same bulk thermal conductivity. Specifically, the Langevin thermostat behaves like a thermalizing boundary inphonon BTE and provides mode-level thermal-equilibrium phonon outlets, while the Nose-Hoover chain thermostat and velocity rescaling method behave like biased reservoirs, which provide a spatially uniform heat generation and mode-level nonequilibrium phonon outlets. These findings explain why different experimental measurement methods can yield different size-dependent thermal conductivity. They also indicate that the thermal conductivity of materials can be tuned for various applications by specifically designing thermostats. The unification of NEMD and phonon BTE will largely facilitate the study of thermal transport in complex systems in the future by, e.g., replacing computationally unaffordable first-principles NEMD simulations with computationally less expensive spectral BTE simulations.

Based on laboratory investigations for R-22 and R-410A alternative low GWP refrigerants in two baseline rooftop air conditioners (RTU), the DOE/ORNL Heat Pump Design Model was used to model the two RTUs and the models were calibrated against the experimental data. We compared the compressor efficiencies and heat exchanger performances. An efficiency-based compressor mapping method was developed. Extensive model-based optimizations were conducted to provide a fair comparison between all the low GWP candidates by selecting optimal configurations. The results illustrate that all the R-22 low GWP refrigerants will lead to slightly lower COPs. ARM-20B appears to be the best R-22 replacement at normal conditions. At higher ambient temperatures, ARM-20A exhibits better performance. All R-410A low GWP candidates will result in similar or better efficiencies than R-410A. R-32 has the best COP while requiring the smallest compressor. R-452B uses the closest compressor displacement volume and achieves the same efficiency as R-410A.

The hot box test method has been applied to evaluate both the steady-state (U-value) and dynamic thermal properties of building envelopes. However, the high construction cost of full-scale hot box apparatus and the testing time required (usually several days) may prevent its wider adoption. To overcome the limitations of full-scale hot box tests, this paper proposes a novel method to evaluate the dynamic thermal performance of building envelope components using a small-scale calibrated hot box and scaled-down specimen. In this paper, the scaling relationships of thermal properties evaluated using a full-size specimen and a scaled-down specimen are established based on the Laplace transform of the heat transfer equations. In addition, dynamic thermal properties obtained from scaled-down experimental tests are compared to the values calculated by the EN ISO13768 (ISO) method. A small-scale hot box with a 355 mm × 355 mm metering area was constructed and calibrated to validate the correlations. Three scaled-down concrete sandwich wall panels were then tested and the scaling relationship was cross-validated using the experimental results, finite difference (FD) simulations, and the ISO method. The results indicate that the dynamic thermal properties obtained from a scaled-down hot box test can be correlated to its full-size counterpart when certain conditions are met. The scaled-down hot box test is demonstrated to be an effective yet economical alternative to a full-scale test with significantly reduced experimentation cost and turn-around time.

This article describes a novel application of thermal anisotropy for improving the energy efficiency of building envelopes. The current work was inspired by existing research on improved heat dissipation in electronics using thermal anisotropy. Past work has shown that thermally anisotropic composites (TACs) can be created by the alternate layering of two dissimilar, isotropic materials. Here, a TAC consisting of alternate layers of rigid foam insulation and thin, high-conductivity aluminum foil was investigated. The TAC was coupled with copper tubes with circulating water that acted as a heat sink and source. The TAC system was applied to a conventional wood-framed wall assembly, and the energy benefits were investigated experimentally and numerically. For experimental testing, large scale test wall specimens were built with and without the TAC system and tested in an environmental chamber under simulated diurnal hot and cold weather conditions. Component-level and whole building numerical simulations were performed to investigate the energy benefits of applying the TAC system to the external walls of a typical, single-family residential building.

This paper presents a life-cycle cost (LCC) informed co-design framework for building structures and envelope systems, holistically considering the influences of energy and natural hazard performance. The proposed method is consisted of a two-stage design and decision-making process, aiming to provide a quantitative guideline for building's structural and envelope co-design based on the its geographic locations. First, the building's structural configuration and envelope type are selected based on the life cycle cost. Then, the long-term cost effectiveness of various energy-saving building envelope options (e.g., high-performance glazing and insulation) is evaluated to refine the envelope design. The proposed co-design framework was demonstrated through the case study of a medium-size office building archetype in three locations with distinct climate conditions and seismic activities (i.e., Los Angeles, Memphis, and Boston). The results highlighted the interplay between building's structural (seismic) performance and the cost-effectiveness of energy-saving design options – e.g., for buildings located in high-seismic regions, seismic enhancing designs greatly reduce the paybak period of high performance building envelope by reducing the seismic loss; whereas for buildings located in regions with cold climate and low seismic risk such as Boston, spatial frame with high insulation building envelope shows the lowest LCC.

To identify low global warming potential refrigerants to replace R-22 and R-410A, extensive experimental evaluations were conducted for multiple candidates of refrigerant at the standard test conditions and at high-ambient conditions with outdoor temperature varying from 27.8°C to 55.0°C. In the study, R-22 was compared to propane (R-290), DR-3, ARM-20B, N-20B, and R-444B in a mini split air-conditioning unit originally designed for R-22; R-410A was compared to R-32, DR-55, ARM-71A, L41-2 (R-447A) in a mini split-unit designed for R-410A. To reveal the physics behind the measured performance results, thermodynamic properties of the alternative refrigerants were analysed. In addition, the experimental data were used to calibrate a physics-based equipment model, for example, ORNL heat pump design model. The calibrated model translated the experimental results to key calculated parameters, i.e. compressor efficiencies and refrigerant side two-phase heat transfer coefficients, corresponding to each refrigeran...

Determining the energy accommodation between gases and solids is essential to developing porous thermal insulation materials with ultra-low effective thermal conductivity that reduce energy use, greenhouse gas emissions, and fossil fuel consumption. The energy accommodation coefficients of most gases, however, have been rarely studied, especially with respect to solids that have relatively high thermal resistivity, e.g., polymers. In this work, by using all-atom nonequilibrium molecular dynamics simulations, we reveal the accommodation coefficients of He, Ar, N2, and O2 with polymers, mainly polystyrene. We find that their values are around 0.51, 0.72, 0.79, and 0.90, respectively, suggesting a critical reexamination of the commonly used theoretical maximum value of 1. We have also conducted experiments and validated the value for air, which is about 0.81. Such a change in accommodation coefficients can lead to a reduction of about 70%, 50%, 35%, and 20% in the thermal conductivity of He, Ar, N2, and O2 gases in nano pores (below 100 nm) or at low pressures (below 1 millibar). With these new accommodation coefficients, we find that in a 10 nm pore with ambient pressure at 300 K, the gas thermal conductivity of He, Ar, N2, and O2 in porous polystyrene can be as low as 9.7 × 10−4, 3.4 × 10−4, 7.3 × 10−4, and 8.5 × 10−4 W·m−1·K−1, respectively, which are two to three orders of magnitude lower than their bulk values, promising higher thermal resistivity of insulation materials. This work reveals the fundamental energy exchange between gases and polymers, providing important guidance for designing high-performance thermal insulation materials for various applications.

In anticipation of emerging global urbanization and consequent increases in energy use and carbon dioxide emissions, better understanding and quantification of climate effects on energy use in cities are needed, requiring coordinated research into large-scale, regional, and microclimate impacts to and from the city structure. The methodology described here addresses this need by (1) demonstrating a process for creating and testing example morphologies for new neighborhoods for their impact on local and regional meteorology within a two-way-coupled four-domain nested mesoscale weather model (6 km horizontal resolution outer domain, 90 m horizontal innermost domain) and (2) allocating resulting building-level meteorological profiles to each building in a neighborhood for parallel computation of building-by-building energy use. Our Chicago Loop test case shows that the morphology of even a small new added development to a neighborhood affects not only its own microclimate, but also the microclimate of the original neighborhood to which the development was added, and that these changes in microclimate affect both neighborhoods’ building energy use. This method represents an important step toward quantifying and analyzing the relationships among climatic conditions, urban morphology, and energy use and using these relationships to inform energy-efficient urban development and planning.

Air leakage through the envelope of commercial buildings in the United States accounts for approximately 6% of their energy use. Various simulation approaches have been proposed to estimate the impact of air leakage on building energy use. Although approaches that are based on detailed airflow modeling appear to be the most accurate to calculate infiltration heat transfer in simulation models, these approaches tend to require significant modeling expertise and effort. To make these energy savings estimates more readily available to building owners and designers, Oak Ridge National Laboratory, the National Institute of Standards and Technology, the Air Barrier Association of America, and the US Department of Energy (DOE) are developing a user-friendly online calculator that applies a detailed airflow modeling approach to examine energy savings due to airtightness in commercial buildings. The calculator, however, is limited to 52 US cities and a few cities in Canada and China. This paper describes the development of an alternative, simplified method to estimate energy savings from improved airtightness. The proposed method uses the same detailed approach for hourly infiltration calculations as the online calculator but it expands the ability to estimate energy savings to all US cities using hourly outdoor air temperature as the only input. The new simple regression model-based approach was developed and tested with DOE’s standalone retail prototype building model. Results from the new approach and the calculator show good agreement. Additionally, a simple approach to estimate percent energy savings for retrofitted buildings was also developed; results were within 5% of the energy saving estimates from the online calculator.

This paper compares the results from a study conducted at Iowa Energy Center’s Energy Resource Station with EnergyPlus simulation results. The building consists of controlled test rooms, dedicated air handling units and air-cooled chillers for the purpose of obtaining quality data suitable for empirical validation studies. Weather data were also collected at the facility and used for the simulation. Empirical validation can be performed on various levels of the program such as zone level, systems level, and plant level. This study is unique in the sense that it integrates the zones, system, and plant into one analysis. For this study, the difference between empirical and EnergyPlus predicted zone cooling loads varied from 1.7% to 10.2%, but the difference for the compressor power was as much as 22.4%. The paper also describes the potential reasons why simulation results might not match field data.

In the United States, commercial buildings accounted for about 19% of the total primary energy consumption in 2012. Further, 29% of the ‘site’ energy in commercial buildings was consumed for space heating and cooling. Applying insulation materials to building envelopes is an effective way of reducing energy consumption for heating and cooling, and limiting the negative environmental impacts from the buildings sector. While insulation materials have a net positive impact on the environment due to reduced energy consumption, they also have some negative impacts associated with their ‘embodied energy’. The total lifetime environmental impacts of insulation materials are a summation of: (1) direct impacts due to their embodied energy, and (2) indirect or impacts avoided due to the reduced building energy consumption. Here, assessments of the lifetime environmental impacts of selected insulation materials for commercial buildings in North America are presented. Direct and indirect environmental impact factors were estimated for the cradle-to-grave insulation life cycle stages. Impact factors were calculated for two categories: primary energy consumption and global warming potential. The direct impact factors were calculated using data from existing literature and a life cycle assessment software. The indirect impact factors were calculated through simulations of a set of standard whole-building models.

In the United States, forty-eight (48) percent of the residential end-use energy consumption is spent on space heating and air conditioning. Reducing envelope-generated heating and cooling loads through application of phase change materials (PCMs) in building envelopes can enhance the energy efficiency of buildings and reduce energy consumption. Experimental testing and numerical modeling of PCM-enhanced envelope components are two important aspects of the evaluation of their energy benefits. An innovative phase change material (nano-PCM) was developed with PCM supported by expanded graphite (interconnected) nanosheets, which are highly conductive and allow enhanced thermal storage and energy distribution. The nano-PCM is shape-stable for convenient incorporation into lightweight building components. A wall with cellulose cavity insulation and a prototype PCM-enhanced interior wallboard was built and tested in a natural exposure test (NET) facility in a hot-humid climate location. The test wall contained the PCM wallboard and a regular gypsum wallboard, for a side-by-side annual comparison study. Further, numerical modeling of the wall containing the nano-PCM wallboard was performed to determine its actual impact on wall-generated heating and cooling loads. The model was first validated using experimental data, and then used for annual simulations using typical meteorological year (TMY3) weather data. This article presents the measured performance and numerical analysis evaluating the energy-saving potential of the nano-PCM-enhanced wallboard.

The main objective of this study is to indentify advanced wall frame assemblies applicable for residential and small commercial buildings, that have or could reach R-values larger than RSI – 3.5 m2 K/W (U-value lower from 0.29). An extensive literature review of existing and past practices is used as the main vehicle to analyze: framing and wall insulation methods, architectural details with focus on minimizing thermal bridges, structural adequacy aspects with respect to gravity and lateral loads, and ability to provide fire and sound breaks. In this paper a wide selection of advance framing wall assemblies is discussed in details with main focus on construction methods, architectural details with minimized thermal bridges, and structural (strength) concerns. High performance wall technologies of consideration include: double walls, Larsen truss walls, optimum or advanced framing walls, walls using distance spacers (furring) and walls made of wood-based composites. Since wood framing for wall applications is mostly used in North America, Scandinavia, and Central Europe, this study is focused on research studies from these regions. In addition, field test studies are presented discussing an application of high R-value of new and retrofitted wall assemblies in actual test houses that have been constructed and being currently monitored.

This article describes a proposed protocol that is intended to provide a comprehensive list of factors to be considered in evaluating the direct and indirect environmental impacts of building insulation materials, as well as detailed descriptions of standardized calculation methodologies to determine those impacts. The energy and environmental impacts of insulation materials can generally be divided into two categories: (1) direct impact due to the embodied energy of the insulation materials and other factors and (2) indirect or environmental impacts avoided as a result of reduced building energy use due to addition of insulation. Standards and product category rules exist, which provide guidelines about the life cycle assessment (LCA) of materials, including building insulation products. However, critical reviews have suggested that these standards fail to provide complete guidance to LCA studies and suffer from ambiguities regarding the determination of the environmental impacts of building insulation and other products. The focus of the assessment protocol described here is to identify all factors that contribute to the total energy and environmental impacts of different building insulation products and, more importantly, provide standardized determination methods that will allow comparison of different insulation material types. Further, the intent is not to replace current LCA standards but to provide a well-defined, easy-to-use comparison method for insulation materials using existing LCA guidelines.

Vacuum insulation panels (VIPs), due to their high thermal performance, provide an attractive alternative to traditional building insulation materials, especially as an option for retrofitting old, poorly insulated buildings. This article describes the complete retrofit of all exterior walls of a single-story building in a cold climate using VIPs. A recently-developed low-cost VIP, called modified atmosphere insulation (MAI), was used in this study. Two buildings of near-identical construction were studied, with one remaining unaltered and serving as the baseline while the other served as the retrofit building. The VIPs or MAI panels proved to be a feasible and durable option for retrofitting building envelopes. Thermal performance of both buildings was analyzed using in-situ temperature and heat flow sensors. Numerical models of the two buildings were created, benchmarked using experimental data and used for predictions of annual energy savings due to the addition of MAI panels to the exterior walls. The models predicted significant reduction in the annual heating energy consumption in the retrofitted building compared to the baseline building.

The original heating load line analysis of ORNL TM-2015/281 was modified to incorporate two adjustments of (1) removing mechanical ventilation and (2) resizing the heat pump units based on new criteria. This resulted in a lowering of the HLL slope factor from the originally rounded 1.3 level to 1.15 in DOE Region IV and V while leaving unchanged the zero-load ambient at a rounded value of 55 F. For the other four DOE regions, the zero-load ambients dropped by 1 to 2 F from those found earlier and the rounded HLL slope factors ranged from 1.05 to 1.3. The average rounded HLL slope factor over all six DOE regions is 1.15. Effects of the revised slope factor on rated HSPFs (Region IV) for single- and two-capacity units dropped from 16% in the original work to 12.6% in this report. For VS units, the HSPF reductions of 14 to 25% in the original report were lowered to a range of 9 to 21%. As in the original report, for VS units that do not limit minimum speed operation below 47 F ambient, the average HSPF reduction for the cases evaluated is approximately the same as for single- and two-capacity units. Formore » VS units that do limit minimum speed operation below 47 F ambient, the lower 1.15 slope factor of this report generally results in small overpredictions of rated HSPF by 1 to 3% compared to functional HSPF. An exception is minimum-speed-limited VS units where the minimum speed COP at 47 F is higher than that at 62 F; one such unit was found to have an HSPF overprediction of over 14% with the 1.15 HLL slope factor level. For such VS exception cases, a default HSPF penalty should be considered. For the more typical VS units that limit minimum speed operation, use of a 1.15 slope factor for rated HSPF was found to still acceptably limit the HSPF error. If slope factors lower than 1.15 are used for HSPF ratings, some means should be considered to appropriately derate the HSPFs for VS units which limit minimum speed operation below 47 F ambient.« less

In recent years, calibrated energy modeling of residential and commercial buildings has gained importance in a retrofit-dominated market. Accurate weather data play an important role in this calibration process and projected energy savings. It would be ideal to measure weather data at the building location to capture relevant microclimate variation but this is generally considered cost-prohibitive. There are data sources publicly available with high temporal sampling rates but at relatively poor geospatial sampling locations. To overcome this limitation, there are a growing number of service providers that claim to provide real time and historical weather data necessary for building modeling at 15–40 km 2 grid across the globe; common variables such as temperature and precipitation have been constructed on ∼1 km 2 grids [1] . Unfortunately, there is limited documentation from 3rd-party sources attesting to the accuracy of this data. This paper compares provided weather characteristics with data collected from a weather station inaccessible to the service providers. Monthly average dry bulb temperature; relative humidity; direct normal, diffuse and global solar radiation; wind speed and wind direction are statistically compared. Moreover, we ascertain the relative contribution of each weather variable and its impact on building loads. Annual simulations are performed for three different building types, including a closely monitored and automated energy efficient research building. The comparison shows that the difference for an individual variable can be as high as 90%. In addition, annual building energy consumption can vary by ±7% while monthly building loads can vary by ±40% as a function of the provided location's weather data.

The reduction and efficient use of resources are critically important issues for the U.S. Department of Defense. The Army builds and uses temporary shelters commonly known as B-huts at forward operating bases, where energy efficiency is mission critical. B-huts are typically not insulated, lack airtightness, and are inherently energy inefficient. Significant opportunities exist to improve the energy performance of these temporary shelters. This work tested the performance and feasibility of several common technologies and techniques to improve overall energy efficiency, constructability, and sustainability of the B-hut. The performance of one control (baseline) B-hut shelter was compared with the performance of one enhanced B-hut shelter, which used the tested commercially available technologies. The data indicate that improvements made to the Enhanced Shelter reduced its energy consumption to at least one-fourth that of the Control Shelter.

This report reviews the suitability of the existing Heating Seasonal Performance Factor (HSPF) ratings and testing requirements for the current generation of variable-speed (VS) air-source heat pumps. Recent field test results indicate larger discrepancies between rated HSPF and field-observed HSPF for VS models than for single-speed models in the same houses. These findings suggest that the heating season test and ratings procedure should be revisited for VS heat pumps. The ratings and testing procedures are described in ANSI/AHRI 210/240 (2008) for single-speed, two-capacity, and variable-speed units. Analysis of manufacturer and independent test performance data on VS units reveals why the current VS testing/ratings procedure results in overly optimistic HSPF ratings for some VS units relative to other types of heat pumps. This is due to a combination of extrapolation of low speed test data beyond the originally anticipated ambient temperature operating range and the constraints of unit controls, which prevent low speed operation over the range of ambient temperatures assumed in the procedure for low speed. As a result, the HSPFs of such units are being overpredicted relative to those for single- and two-capacity designs. This overprediction has been found to be significantly reduced by use in the HSPF ratingsmore » procedure of an alternative higher-load heating load line, described in a companion report (Rice et al., 2015).« less

Gas filled insulation panels (GFP) are very light weight and compact (when uninflated) advanced insulation products. GFPs consist of multiple layers of thin, low emittance (low-e) metalized aluminum. When expanded, the internal, low-e aluminum layers form a honeycomb structure. These baffled polymer chambers are enveloped by a sealed barrier and filled with either air or a low-conductivity gas. The sealed exterior aluminum foil barrier films provide thermal resistance, flammability protection, and properties to contain air or a low conductivity inert gas. This product was initially developed with a grant from the U.S. Department of Energy. The unexpanded product is nearly flat for easy storage and transport. Therefore, transportation volume and weight of the GFP to fill unit volume of wall cavity is much smaller compared to that of other conventional insulation products. This feature makes this product appealing to use at Army Contingency Basing, when transportation cost is significant compared to the cost of materials. The objective of this study is to evaluate thermal performance of walls, similar to those used at typical Barracks Hut (B-Hut) hard shelters, when GFPs are used in the wall cavities. Oak Ridge National Laboratory (ORNL) tested performance of the wall in the rotatable guardedmore » hotbox (RGHB) according to the ASTM C 1363 standard test method.« less

The US Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy (EERE) and Traco partnered to develop high-performance windows for commercial building that are cost-effective. The main performance requirement for these windows was that they needed to have an R-value of at least 5 ft2 F h/Btu. This project seeks to quantify the potential energy savings from installing these windows in commercial buildings that are at least 20 years old. To this end, we are conducting evaluations at a two-story test facility that is representative of a commercial building from the 1980s, and are gathering measurements on the performance of its windows before and after double-pane, clear-glazed units are upgraded with R5 windows. Additionally, we will use these data to calibrate EnergyPlus models that we will allow us to extrapolate results to other climates. Findings from this project will provide empirical data on the benefits from high-performance windows, which will help promote their adoption in new and existing commercial buildings. This report describes the experimental setup, and includes some of the field and simulation results.

As a contribution to the AHRI Low-GWP Alternative Refrigerants Evaluation Program (AREP), this study compares the performance of four lower-GWP alternative refrigerants, ARM-31a, D2Y-65, L-40, and R-32 + R-134a mixture, to that of refrigerant R-404A (baseline) in a scroll compressor designed for medium temperature refrigeration applications. These comparisons were carried out via compressor calorimeter tests performed on a compressor designed for refrigerant R-404A and having a nominal rated capacity of 23,500 Btu/hr. Tests were conducted over a suction dew point temperature range of -10 F to 35 F in 5 F increments and a discharge dew point temperature range of 70 F to 140 F in 10 F increments. All the tests were performed with 20 F superheat, 40 F superheat, and 65 F suction temperature. A liquid subcooling level of 10 F to 15 F was maintained for all the test conditions. However, the cooling capacities reported in this study are normalized for 0 F subcooling. The tests showed that the compressor energy efficiency ratio (EER) and cooling capacity with all four alternative refrigerants tested are higher at higher saturation suction and saturation discharge temperature and lower at lower saturation suction and saturation discharge temperature, compared to that ofmore » R-404A. Discharge temperatures of all the alternative refrigerants were higher than that of R-404A at all test conditions.« less

This report presents experimental and numerical results from thermal performance studies. The purpose of this Cooperative Research and Development Agreement (CRADA) between UT-Battelle, LLC and John s Manville was to design a basic concept of a new generation of thermally-enhanced fiber glass insulation. Different types of Phase Change Materials (PCMs) have been tested as dynamic components in buildings during the last 4 decades. Most historical studies have found that PCMs enhance building energy performance. Some PCM-enhanced building materials, like PCM-gypsum boards or PCM-impregnated concretes have already found their limited applications in different countries. Today, continued improvements in building envelope technologies suggest that throughout Southern and Central U.S. climates, residences may soon be routinely constructed with PCM in order to maximize insulation effectiveness and maintain low heating and cooling loads. The proposed thermally-enhanced fiber glass insulation will maximize this integration by utilizing a highly-efficient building envelope with high-R thermal insulation, active thermal mass and superior air-tightness. Improved thermal resistance will come from modifications in infrared internal characteristics of the fiber glass insulation. Thermal mass effect can be provided by proprietary thermally-active microencapsulated phase change material (PCM). Work carried out at the Oak Ridge National Laboratory (ORNL) on the CRADA is describedmore » in this report.« less