%0 Report %D 1999 %T RESFEN 3.1: A PC Program for Calculating the Heating and Cooling Energy Use of Windows in Residential Buildings %A Robin Mitchell %A Yu Joe Huang %A Dariush K. Arasteh %A Robert Sullivan %A Santosh Phillip %X

A computer tool such as RESFEN can help consumers and builders pick the most energy-efficient and cost-effective window for a given application, whether it is a new home, an addition, or a window replacement. It calculates heating and cooling energy use and associated costs as well as peak heating and cooling demand for specific window products. Users define a specific scenario by specifying house type (single-story or two-story), geographic location, orientation, electricity and gas cost, and building configuration details (such as wall, floor, and HVAC system type). Users also specify size, shading, and thermal properties of the window they wish to investigate. The thermal properties that RESFEN requires are: U-factor, Solar Heat Gain Coefficient, and air leakage rate. RESFEN calculates the energy and cost implications of the window compared to an insulated wall. The relative energy and cost impacts of two different windows can be compared.

RESFEN 3.0 was a major improvement over previous versions because it performs hourly calculations using a version of the DOE 2.1E (LBL 1980, Winkelmann et al. 1993) energy analysis simulation program. RESFEN 3.1 incorporates additional improvements including input assumptions for the base case buildings taken from the National Fenestration Rating Council (NFRC) Annual Energy Subcommittee's efforts.

%I Lawrence Berkeley National Laboratory %C Berkeley %8 08/1999 %G eng %1

Windows and Daylighting Group

%2 LBNL-40682 Rev. %0 Report %D 1997 %T RESFEN 3.0: A PC Program for Calculating the Heating and Cooling Energy Use of Windows in Residential Buildings %A Yu Joe Huang %A Robert Sullivan %A Dariush K. Arasteh %A Robin Mitchell %X

Today's energy-efficient windows can dramatically lower the heating and cooling costs associated with windows while increasing occupant comfort and minimizing window surface condensation problems. However, consumers are often confused about how to pick the most efficient window for their residence. They are typically given window properties such as U-factors or R-values, Solar Heat Gain Coefficients or Shading Coefficients, and air leakage rates. However, the relative importance of these properties depends on the site and building specific conditions. Furthermore, these properties are based on static evaluation conditions that are very different from the real situation the window will be used in. Knowing the energy and associated cost implications of different windows will help consumers and builders make the best decision for their particular application, whether it is a new home, an addition, or a window replacement.

A computer tool such as RESFEN can help consumers and builders pick the most energy-efficient and cost-effective window for a given application. It calculates the heating and cooling energy use and associated costs as well as the peak heating and cooling demand for specific window products. Users define a problem by specifying the house type (single story or two story), geographic location, orientation, electricity and gas cost, and building configuration details (such as wall type, floor type, and HVAC systems). Window options are defined by specifying the window`s size, shading, and thermal properties: U-factor, Solar Heat Gain Coefficient, and air leakage rate. RESFEN calculates the energy and cost implications of the windows compared to insulated walls. The relative energy and cost impacts of two different windows can be compared against each other.

RESFEN 3.0 is a major improvement over previous versions of RESFEN because it performs hourly calculations using a version of the DOE 2.1E energy analysis simulation program.

%I Lawrence Berkeley National Laboratory %P 38 %8 12/1997 %2 LBNL-40682 %0 Conference Paper %B Thermal Performance of the Exterior Envelopes of Buildings VI Conference Proceedings %D 1995 %T Reducing Residential Cooling Requirements Through the Use of Electrochromic Windows %A Robert Sullivan %A Michael D. Rubin %A Stephen E. Selkowitz %X

This paper presents the results of a study investigating the energy performance of electrochromic windows in a prototypical residential building under a variety of state switching control strategies. We used the DOE-2.1E energy simulation program to analyze the annual cooling energy and peak demand as a function of glazing type, size, and electrochromic control strategy. A single-story ranch-style home located in the cooling-dominated locations of Miami, FL and Phoenix, AZ was simulated. Electrochromic control strategies analyzed were based on incident total solar radiation, space cooling load, and outside air temperature. Our results show that an electrochromic material with a high reflectance in the colored state provides the best performance for all control strategies. On the other hand, electrochromic switching using space cooling load provides the best performance for all the electrochrornic materials. The performance of the incident total solar radiation control strategy varies as a function of the values of solar radiation which trigger the bleached and colored states of the electrochromic (setpoint range); i.e., required cooling decreases as the setpoint range decreases; also, performance differences among electrochromics increases. The setpoint range of outside air temperature control of electrochromics must relate to the ambient weather conditions prevalent in a particular location. If the setpoint range is too large, electrochromic cooling performance is very poor. Electrochromics compare favorably to conventional low-E clear glazings that have high solar heat gain coefficients that are used with overhangs. However, low-E tinted glazings with low solar heat gain coefficients can outperform certain electrochromics. Overhangs should be considered as a design option for electrochromics whose state properties do not change significantly between bleached and colored states.

%B Thermal Performance of the Exterior Envelopes of Buildings VI Conference Proceedings %C Clearwater Beach, FL %8 12/1995 %G eng %L LBL-37211 %1

Windows and Daylighting Group

%2 LBL-37211 %0 Conference Paper %B SPIE 13. International Symposium on Optical Materials Technology for Energy Efficiency and Solar Energy Conversion %D 1994 %T A Review of Electrochromic Window Performance Factors %A Stephen E. Selkowitz %A Michael D. Rubin %A Eleanor S. Lee %A Robert Sullivan %X

The performance factors which will influence the market acceptance of electrochromic windows are reviewed. A set of data representing the optical properties of existing and foreseeable electrochromic window devices was generated. The issue of reflective versus absorbing electrochromics was explored. This data was used in the DOE 2.1 building energy model to calculate the expected energy savings compared to conventional glazings. The effects of several different control strategies were tested. Significant energy and peak electric demand benefits were obtained for some electrochromic types. Use of predictive control algorithms to optimize cooling control may result in greater energy savings. Initial economic results considering annual savings, cooling equipment cost savings, and electrochromic window costs are presented. Calculations of thermal and visual comfort show additional benefits from electrochromics but more work is needed to quantify their importance. The design freedom and aesthetic possibilities of these dynamic glazings should provide additional market benefits, but their impact is difficult to assess at this time. Ultimately, a full assessment of the market viability of electrochromics must consider the impacts of all of these issues.

%B SPIE 13. International Symposium on Optical Materials Technology for Energy Efficiency and Solar Energy Conversion %C Freiburg, Germany %8 04/1994 %G eng %L LBL-35486 %1

Windows and Daylighting Group

%2 LBL-35486