@techreport {1631, title = {Modeling Windows in Energy Plus with Simple Performance Indices}, year = {2009}, month = {10/2009}, abstract = {

The paper describes the development of a model specification for performance monitoring systems for commercial buildings. The specification focuses on four key aspects of performance monitoring:

The aim is to assist building owners in specifying the extensions to their control systems that are required to provide building operators with the information needed to operate their buildings more efficiently and to provide automated diagnostic tools with the information required to detect and diagnose faults and problems that degrade energy performance.

The paper reviews the potential benefits of performance monitoring, describes the specification guide and discusses briefly the ways in which it could be implemented. A prototype advanced visualization tool is also described, along with its application to performance monitoring. The paper concludes with a description of the ways in which the specification and the visualization tool are being disseminated and deployed.

}, author = {Dariush K. Arasteh and Christian Kohler and Brent T. Griffith} } @conference {11970, title = {Infrared Thermography Measurements of Window Thermal Test Specimen: Surface Temperatures}, booktitle = {ASHRAE Seminar}, year = {2001}, month = {01/2002}, address = {Atlantic City, NJ}, abstract = {

Temperature distribution data are presented for the warm-side surface of three different window specimens. The specimens were placed between warm and cold environmental chambers that were operated in steady state at two different standard design conditions for winter heating. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) temperature conditions were 21.1 deg. C (70 deg. F) and -17.8 deg. C (0 deg. F) on the warm and cold sides, respectively. The International Standards Organization (ISO) temperature conditions were 20.0 deg. C (68.0 deg. F) and 0.0 deg. C (32.0 deg. F) on the warm and cold sides, respectively. Surface temperature maps were compiled using an infrared thermographic system with an external referencing technique, a traversing point infrared thermometer and thermocouples. The infrared techniques allow detailed, non-intrusive mapping of surface temperatures. Surface temperature data are plotted for the vertical distribution along the centerline of the window specimen. This paper is part of larger round-robin collaborative effort that studied this same set of window specimens. These studies were conducted to improve and check the accuracy of computer simulations for predicting the condensation resistance of window products. Data collected for a Calibrated Transfer Standard showed that convective effects outside the window gap are important for predicting surface temperatures.

}, author = {Brent T. Griffith and Howdy Goudey and Dariush K. Arasteh} } @article {12093, title = {Natural Convection Effects in Three-Dimensional Window Frames with Internal Cavities}, journal = {ASHRAE Transactions}, volume = {107, Part 2}, year = {2000}, month = {06/2001}, address = {Cincinnati, Ohio}, abstract = {

This paper studies three-dimensional natural convection effects in window frames with internal cavities. Infrared (IR) thermography experiments, computational fluid dynamics (CFD) simulations, and calculations with traditional software for simulating two-dimensional heat conduction were conducted. The IR thermography experiments mapped surface temperatures during steady-state thermal tests between ambi-ent thermal chambers set at 0 deg. C and 20 deg. C. Using anon-contact infrared scanning radiometer and an external referencing technique, we were able to obtain surface temperature maps with a resolution of 0.1 deg. C and 3 mm and an estimated uncertainty of 0.5 deg. C and +/-3 mm. The conjugate CFD simulations modeled the enclosed air cavities, frame section walls, and foam board surround panel. With the two-dimensional heat conduction simulation software, weusedcorrelations to model heat transfer in the air cavities. For both the CFD simulations and the conduction simulation software, boundary conditions at the external air/solid interface were modeled using constant surface heat-transfer coefficients with fixed ambient air temperatures.

Different cases were studied, including simple, four-sided frame sections (with one open internal cavity), simple vertical sections with a single internal cavity, and horizontal sections with a single internal cavity. The sections tested in the Infrared Thermography Laboratory (IR lab) were made of PVC. Both PVC and thermally broken aluminum sections were modeled. Based on the current investigations, it appears that the thermal transmittance or U-factor of a four-sided section can be found by calculating the average of the thermal transmittance of the respective single horizontal and vertical sections. In addition, we conclude that two-dimensional heat transfer simulation software agrees well with CFD simulations if the natural convection correlations used for the internal cavities are correct.

}, author = {Arlid Gustavsen and Brent T. Griffith and Dariush K. Arasteh} } @article {1911, title = {Three-Dimensional Conjugate Computational Fluid Dynamics Simulations of Internal Window Frame Cavities Validated Using IR Thermography}, journal = {ASHRAE Transactions}, volume = {107}, year = {2000}, month = {06/2001}, pages = {538-549}, address = {Cincinnati, Ohio}, abstract = {

This paper studies the effectiveness of one commercial computational fluid dynamics (CFD) program for simulating combined natural convection and heat transfer in three dimensions for air-filled cavities similar to those found in the extruded frame sections of windows. The accuracy of the conjugate CFD simulations is evaluated by comparing results for surface temperature on the warm side of the specimens to results from experiments that use infrared (IR) thermography to map surface temperatures during steady-state thermal tests between ambient thermal chambers set at 0 {\textdegree}C and 20 {\textdegree}C. Validations using surface temperatures have been used in previous studies of two-dimensional simulations of glazing cavities with generally good results. Using the techniques presented and a noncontact infrared scanning radiometer we obtained surface temperature maps with a resolution of 0.1 {\textdegree}C and 3 mm and an estimated uncertainty of +/-0.5 {\textdegree}C and +/-3mm. Simulation results are compared to temperature line and contour plots for the warm side of the specimen. Six different cases were studied, including a simple square section in a single vertical cavity and two four-sided frame cavities as well as more complex H- and U-shaped sections. The conjugate CFD simulations modeled the enclosed air cavities, the frame section walls, and the foam board surround panel. Boundary conditions at the indoor and outdoor air/solid interface were modeled using constant surface heat-transfer coefficients with fixed ambient-air temperatures. In general, there was good agreement between the simulations and experiments, although the accuracy of the simulations is not explicitly quantified. We conclude that such simulations are useful for future evaluations of natural convection heat transfer in frame cavities.

}, author = {Arlid Gustavsen and Brent T. Griffith and Dariush K. Arasteh} } @conference {1890, title = {THERM 2.0: A Building Component Model for Steady-State Two-Dimensional Heat Transfer}, booktitle = {Building Simulation 99, International Building Performance Simulation Association (IBPSA)}, year = {1999}, month = {09/1999}, address = {Kyoto, Japan}, abstract = {

THERM 2.0 is a state-of-the-art software program, available without cost, that uses the finite-element method to model steady-state, two-dimensional heat-transfer problems. It includes a powerful simulation engine combined with a simple, interactive interface and graphic results. Although it was developed primarily to model thermal properties of windows, it is appropriate for other building components such as walls, doors, roofs, and foundations, and is useful for modeling thermal bridges in many other contexts, such as the design of equipment.

}, author = {Charlie Huizenga and Dariush K. Arasteh and Elizabeth U. Finlayson and Robin Mitchell and Brent T. Griffith and Dragan C. Curcija} } @conference {11866, title = {Experimental Techniques for Measuring Temperature and Velocity Fields to Improve the Use and Validation of Building Heat Transfer Models}, booktitle = {Thermal Performance of the Exterior Envelopes of Buildings VII}, year = {1998}, month = {12/1998}, address = {Clearwater Beach, FL}, abstract = {

When modeling thermal performance of building components and envelopes, researchers have traditionally relied on average surface heat-transfer coefficients that often do not accurately represent surface heat-transfer phenomena at any specific point on the component being evaluated. The authors have developed new experimental techniques that measure localized surface heat-flow phenomena resulting from convection. The data gathered using these new experimental procedures can be used to calculate local film coefficients and validate complex models of room and building envelope heat flows. These new techniques use a computer controlled traversing system to measure both temperatures and air velocities in the boundary layer near the surface of a building component, in conjunction with current methods that rely on infrared (IR) thermography to measure surface temperatures. Measured data gathered using these new experimental procedures are presented here for two specimens: (1) a Calibrated Transfer Standard (CTS) that approximates a constant-heat-flux, flat plate; and (2) a dual-glazed, low-emittance (low-e), wood-frame window. The specimens were tested under steady-state heat flow conditions in laboratory thermal chambers. Air temperature and mean velocity data are presented with high spatial resolution (0.25- to 25-mm density). Local surface heat-transfer film coefficients are derived from the experimental data by means of a method that calculates heat flux using a linear equation for air temperature in the inner region of the boundary layer. Local values for convection surface heat-transfer rate vary from 1 to 4.5 W/m2K. Data for air velocity show that convection in the warm-side thermal chamber is mixed forced/natural, but local velocity maximums occur from 4 to 8 mm from the window glazing.

}, author = {Brent T. Griffith and Daniel Turler and Howdy Goudey and Dariush K. Arasteh} } @conference {12207, title = {Rapid field testing of low-emittance coated glazings for product verification}, booktitle = {ASHRAE/DOE/BTECC Conference, Thermal Performance of the Exterior Envelopes of Buildings VII}, year = {1998}, month = {12/1998}, address = {Clearwater Beach, Florida}, abstract = {

This paper analyzes prospects for developing a test device suitable for field verification of the types of low-emittance (low-e) coatings present on high-performance window products. Test devices are currently available that can simply detect the presence of low-e coatings and that can measure other important characteristics of high-performance windows, such as the thickness of glazing layers or the gap in dual glazings. However, no devices have yet been developed that can measure gas concentrations or distinguish among types of coatings. This paper presents two optical methods for verification of low-e coatings. The first method uses a portable, fiber-optic spectrometer to characterize spectral reflectances from 650 to 1,100 nm for selected surfaces within an insulated glazing unit (IGU). The second method uses an infrared-light-emitting diode and a phototransistor to evaluate the aggregate normal reflectance of an IGU at 940 nm. Both methods measure reflectance in the near (solar) infrared spectrum and are useful for distinguishing between regular and spectrally selective low-e coatings. The infrared-diode/phototransistor method appears promising for use in a low-cost, hand-held field test device.

}, author = {Brent T. Griffith and Christian Kohler and Howdy Goudey and Daniel Turler and Dariush K. Arasteh} } @article {1880, title = {Teaching Students about Two-Dimensional Heat Transfer Effects in Buildings, Building Components, Equipment, and Appliances Using THERM 2.0}, journal = {ASHRAE Transactions}, volume = {105, Part 1}, year = {1998}, month = {01/1999}, address = {Chicago, IL}, abstract = {

THERM 2.0 is a state-of-the-art software program, available for free, that uses the finite-element method to model steady-state, two-dimensional heat-transfer effects. It is being used internationally in graduate and undergraduate laboratories and classes as an interactive educational tool to help students gain a better understanding of heat transfer. THERM offers students a powerful simulation engine combined with a simple, interactive interface and graphic results. Although it was developed to model thermal properties of building components such as windows, walls, doors, roofs, and foundations, it is useful for modeling thermal bridges in many other contexts, such as the design of equipment. These capabilities make THERM a useful teaching tool in classes on: heating, ventilation, and air-conditioning (HVAC); energy conservation; building design; and other subjects where heat-transfer theory and applications are important. THERMs state-of-the-art interface and graphic presentation allow students to see heat-transfer paths and to learn how changes in materials affect heat transfer. THERM is an excellent tool for helping students understand the practical application of heat-transfer theory.

}, author = {Charlie Huizenga and Dariush K. Arasteh and Elizabeth U. Finlayson and Robin Mitchell and Brent T. Griffith} } @article {11949, title = {Improving Computer Simulations of Heat Transfer for Projecting Fenestration products: Using Radiation View-Factor Models}, journal = {ASHRAE Transactions}, volume = {104, Part 1}, number = {Part 1}, year = {1997}, abstract = {

The window well formed by the concave surface on the warm side of skylights and garden windows can cause surface heat-flow rates to be different for these projecting types of fenestration products than for normal planar windows. Current methods of simulating fenestration thermal conductance (U-value) use constant boundary condition values for overall surface heat transfer. Simulations that account for local variations in surface heat transfer rates (radiation and convection) may be more accurate for rating and labeling window products whose surfaces project outside a building envelope. This paper, which presents simulation and experimental results for one projecting geometry, is the first step in documenting the importance of these local effects.

A generic specimen, called the foam garden window, was used in simulations and experiments to investigate heat transfer of projecting surfaces. Experiments focused on a vertical cross section (measurement plane) located at the middle of the window well on the warm side of the specimen. The specimen was placed between laboratory thermal chambers that were operated at American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) winter heating design conditions. Infrared thermography was used to map surface temperatures. Air temperature and velocity were mapped throughout the measurement plane using a mechanical traversing system. Finite-element computer simulations that directly modeled element-to-element radiation were better able to match experimental data than simulations that used fixed coefficients for total surface heat transfer. Air conditions observed in the window well suggest that localized convective effects were the reason for the difference between actual and modeled surface temperatures. U-value simulation results were 5 to 10\% lower when radiation was modeled directly.

}, author = {Brent T. Griffith and Dragan C. Curcija and Daniel Turler and Dariush K. Arasteh} } @article {1794, title = {The Significance of Bolts in the Thermal Performance of Curtain-Wall Frames for Glazed Fa{\c c}ades}, journal = {ASHRAE Transactions}, volume = {104, Part 1}, year = {1997}, month = {01/1998}, address = {San Francisco, CA}, abstract = {

Curtain walls are assemblies of glazings and metal frames that commonly form the exterior glass fa{\c c}ades of commercial buildings. Evaluating the thermal performance of the bolts that hold curtain wall glazings in place is necessary to accurately rate the overall thermal performance of curtain walls. Using laboratory tests and computer simulations, we assessed the thermal performance of several different configurations of bolts and glazings. Curtain-wall samples were tested in the infrared thermography laboratory at the Lawrence Berkeley National Laboratory (LBNL) in Berkeley, California. Experimental results were compared to two-dimensional simulations approximating the thermal effect of the bolts using the parallel path and the isothermal planes calculation methods. We conclude that stainless steel bolts minimally affect curtain-wall thermal performance (approximately 18\%) when spaced at least nine inches apart, which is the industry standard. Performance is increasingly compromised when there is less than nine inches between bolts or when steel bolts are used. We also show that the isothermal planes method of approximating curtain wall thermal performance can be used with 2-D heat transfer software typical of that used in the window industry to give conservative results for the thermal bridging effect caused by bolts.

}, author = {Brent T. Griffith and Elizabeth U. Finlayson and Mehry Yazdanian and Dariush K. Arasteh} } @conference {11894, title = {Gas Filled Panels: An Update on Applications in the Building Thermal Envelope}, booktitle = {BETEC Fall Symposium, Superinsulations and the Building Envelope}, year = {1995}, month = {11/1995}, address = {Washington, DC}, abstract = {

This paper discusses the application of Gas-Filled Panels to the building thermal envelope. Gas-Filled Panels, or GFPs, are thermal insulating devices that retain a high concentration of a low-conductivity gas, at atmospheric pressure, within a multilayer infrared reflective baffle. The thermal performance of the panel depends on the type of gas fill and the baffle configuration. We present computer simulation results showing the improvement in thermal resistance resulting from using an argon-GFP in place of glass fiber batt insulation in wood-frame construction. This report also presents estimates of the quantity and cost of material components needed to manufacture GFPs using current prototype designs.

}, author = {Brent T. Griffith and Dariush K. Arasteh and Daniel Turler} } @techreport {58588, title = {An Infrared Thermography-Based Window Surface Temperature Database for the Validation of Computer Heat Transfer Models}, year = {1995}, month = {03/1995}, abstract = {

Fenestration heat transfer simulation codes are used in energy performance rating and labeling procedures to model heat transfer through window systems and to calculate window U-values and condensation resistance factors. Experimental measurements of window thermal performance can direct the development of these codes, identify their strengths and weaknesses, set research priorities, and validate finished modeling tools. Infrared (IR) thermography is a measurement technique that is well suited to this task. IR thermography is a relatively fast, non-invasive, non-destructive technique that can resolve thermal performance differences between window components and window systems to a higher degree than a conventional hot box test. Infrared thermography provides spatial resolution of system performance by generating surface temperature maps of windows under controlled and characterized environmental conditions.

This paper summarizes basic theory and techniques for maximizing the accuracy and utility of infrared thermographic temperature measurements of window systems and components in a controlled laboratory setting. The physical setup of a complete infrared thermographic test facility at a major U.S. national research laboratory is described. Temperature measurement issues, and accuracy limits, for quantitative laboratory infrared thermography are discussed. An external reference emitter allows test-specific correction of absolute temperatures measured with an infrared scanner, resulting in {\textquoteright}an absolute measurement accuracy of {\textpm}O.5{\textdegree}C. Quantitative IR thermography is used to form a database of window surface temperature profiles for the validation of finite-element and finite-difference fenestration heat transfer modeling tools. An IR window surface temperature database with complete technical drawings of the windows tested; specification of all test window dimensions, materials, and thermal conductivities; environmental conditions of the tests with associated measurement errors; and two-dimensional surface temperature maps and selected cross sectional temperature profiles in a spreadsheet database format on an electronic media are presented.

}, author = {Fredric A. Beck and Brent T. Griffith and Daniel Turler and Dariush K. Arasteh} } @conference {12004, title = {Issues Associated with the Use of Infrared Thermography for Experimental Testing of Insulated Systems}, booktitle = {Thermal Performance of the Exterior Envelopes of Buildings VI Conference }, year = {1995}, month = {12/1995}, address = {Clearwater Beach, FL}, abstract = {

Infrared scanning radiometers are used to generate temperature maps of building envelope components, including windows and insulation. These temperature maps may assist in evaluating components thermal performance. Although infrared imaging has long been used for field evaluations, controlled laboratory conditions allow improvements in quantitative measurements of surface temperature using reference emitter techniques.

This paper discusses issues associated with the accuracy of using infrared scanning radiometers to generate temperature maps of building envelope components under steady-state, controlled laboratory conditions. Preliminary experimental data are presented for the accuracy and uniformity of response of one commercial infrared scanner. The specified accuracy of this scanner for temperature measurements is 2 {\textdegree}C or 2\% of the total range of values (span) being measured. A technique is described for improving this accuracy using a temperature-controlled external reference emitter. Minimum temperature measurement accuracy with a reference emitter is estimated at {\textpm}0.5 {\textdegree}C for ambient air and background radiation at 21.1 {\textdegree}C and surface temperatures from 0 {\textdegree}C to 21 {\textdegree}C.

Infrared imaging, with a reference emitter technique, is being used to create a database of temperature maps for a range of window systems, varying in physical complexity, material properties, and thermal performance. The database is to be distributed to developers of fenestration heat transfer simulation programs to help validate their models. Representative data are included for two insulated glazing units with different spacer systems.

}, author = {Brent T. Griffith and Fredric A. Beck and Dariush K. Arasteh and Daniel Turler} } @article {1872, title = {Surface Temperatures of Insulated Glazing Units: Infrared Thermography Laboratory Measurements}, journal = {ASHRAE Transactions}, volume = {102}, year = {1995}, month = {12/1995}, abstract = {

Data are presented for the distribution of surface temperatures on the warm-side surface of seven different insulated glazing units. Surface temperatures are measured using infrared thermography and an external referencing technique. This technique allows detailed mapping of surface temperatures that is non-intrusive. The glazings were placed between warm and cold environmental chambers that were operated at conditions corresponding to standard design conditions for winter heating. The temperatures conditions are 21.1 {\textdegree}C (70 {\textdegree}F) and -17.8 {\textdegree}C (0 {\textdegree}F) on the warm and cold sides, respectively. Film coefficients varied somewhat with average conditions of about 7.6 W/m2 K (1.34 Btu/h ft2 {\textdegree}F) for the warm-side and 28.9 W/m2 K (5.1 Btu/h ft2 {\textdegree}F) for the cold-side. Surface temperature data are plotted for the vertical distribution along the centerline of the IG and for the horizontal distribution along the centerline. This paper is part of larger collaborative effort that studied the same set of glazings.

}, author = {Brent T. Griffith and Daniel Turler and Dariush K. Arasteh} } @conference {1946, title = {Using Infrared Thermography for the Creation of a Window Surface Temperature Database to Validate Computer Heat Transfer Models}, booktitle = {Windows Innovations Conference 95}, year = {1995}, month = {06/1995}, address = {Toronto, Canada}, abstract = {

Infrared thermography is a non-invasive, non-destructive technique for measuring surface temperatures of an object. These surface temperatures can be used to understand the thermal performance of window components and complete window systems. Infrared (IR) thermography has long been used for qualitative field assessment of window thermal performance, and is now being used in the laboratory for quantitative assessments of window thermal performance. As windows become better and better, more refined test methods and/or simulation tools are required to accurately detect performance changes and make comparisons between products. While hot box calorimetery has worked well to characterize the thermal performance of conventional insulating products, differences in the thermal performance of new highly insulating systems are often less than the resolution of conventional hot box calorimeters. Infrared imaging techniques offer the opportunity to resolve small differences in the thermal performance of components of highly insulating window systems that hot box measurements are not able to identify.

Lawrence Berkeley Laboratory (LBL), a U.S. national research laboratory, is currently using infrared thermography to develop a database of measured surface temperature profiles for a number of different fenestration products for use in validating both basic and advanced two- and three-dimensional finite element method (FEM) and finite difference method (FDM) fenestration heat transfer simulation programs. IR surface temperature data, when taken under controlled laboratory conditions, can be used to direct the development of these simulation codes, identify their strengths and weaknesses, set research priorities, and validate finished modeling tools. Simulation of fenestration heat transfer is faster and less expensive than hot box testing of fenestration products, and forms the basis of window energy codes being implemented, developed, or considered in the US, Canada, the Former Soviet Union, Europe, and Australia. The National Fenestration Rating Council (U. S.) has developed a simulation-based standard which is used to rate and label window U-values for a published directory of over 10,000 different window products.

}, author = {Fredric A. Beck and Brent T. Griffith and Daniel Turler and Dariush K. Arasteh} } @conference {11987, title = {Integrated Window Systems: An Advanced Energy-Efficient Residential Fenestration Product}, booktitle = {19th National Passive Solar Conference}, year = {1994}, month = {06/1994}, address = {San Jose, CA}, abstract = {

The last several years have produced a wide variety of new window products aimed at reducing the energy impacts associated with residential windows. Improvements have focused on reducing the rate at which heat flows through the total window product by conduction/convection and thermal radiation (quantified by the U-factor) as well as in controlling solar heat gain (measured by the Solar Heat Gain Coefficient (SHGC) or Shading Coefficient (SC).

Significant improvements in window performance have been made with low-E coated glazings, gas fills in multiple pane windows and with changes in spacer and frame materials and designs. These improvements have been changes to existing design concepts. They have pushed the limits of the individual features and revealed weaknesses. The next generation of windows will have to incorporate new materials and ideas, like recessed night insulation, seasonal sun shades and structural window frames, into the design, manufacturing and construction process, to produce an integrated window system that will be an energy and comfort asset.

}, author = {Dariush K. Arasteh and Brent T. Griffith and Paul LaBerge} } @conference {12156, title = {Optimizing the Effective Conductivity and Cost of Gas-Filled Panel Thermal Insulations}, booktitle = {22nd International Thermal Conductivity Conference}, year = {1993}, month = {11/1993}, address = {Tempe, AZ}, abstract = {

Gas-Filled Panels, or GFPs, are an advanced theimal insulation that employ a low-conductivity, inert gas, at atmospheiic pressure, within a multilayer reflective baffle. The thermal performance of GFPs varies with gas conductivity, overall panel thickness, and baffle construction. Design parameters of baffle constructions that have a strong effect on GFP thermal resistance are (1) cavities per thickness, (2) cavity surface emittance, and (3) conductance of the baffle materials. GFP thermal performances, where the above parameters were varied, were modeled on a spreadsheet by iterative calculation of one-dimensional energy balances. Heat flow meter apparatus measurements of prototype GFP effective conductivities have been made and are compared to results of the calculations. The costs associated with varying baffle constructions are estimated based on the prices of commercial material components. Results are presented in terms of cost per area per unit thermal resistance ($/Area*R-Value) and are usefid for optimizing GFP designs forsair, argon, or krypton gas fills and a desired effective conductivity and thickness.

}, author = {Brent T. Griffith and Daniel Turler and Dariush K. Arasteh} }