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This report is part of a series describing different ResStock (TM) measures. "Measures" refers to energy efficiency retrofits that can be applied to buildings during modeling. This documentation covers the "Propane Fuel 95% AFUE and Fuel Oil Furnace 88% AFUE" measure upgrade methodology and briefly discusses key results.
The Annual Fuel Utilization Efficiency (AFUE) analysis of residential and light commercial furnaces follows ANSI/ASHRAE Standard 103-2017 (i.e., Method of Testing for Annual Fuel Utilization Efficiency of Residential Central Furnaces and Boilers) . The analysis is a complex, comprehensive method based on furnace configuration and specific components equipped, requiring detailed furnace testing and measurement data. For this reason, an AFUE Analysis Tool using Microsoft Excel enabled with Visual Basic for Applications (VBA) was developed with a user-friendly interface and comprehensive coverage. The tool consists of three worksheets: unit and configuration selection, geometry and measurement data input, and AFUE plus key results. This tool can be used to estimate the AFUE of both condensing and noncondensing furnaces with single-stage, two-stage, and step-modulating functions. The tool was validated with experimental data from Oak Ridge National Laboratory’s natural gas furnace projects that are commercially available. The results indicate the tool is reasonably accurate in the evaluation of a new R&D modified furnace unit.
This report is part of a series describing different ResStock (TM) measures. "Measures" refers to energy efficiency retrofits that can be applied to buildings during modeling. This documentation covers the "Natural Gas Furnace 95% AFUE" measure upgrade methodology and briefly discusses key results.
The objective of this project is to examine the impact that common installation practices and age-induced equipment degradation may have on the installed performance of natural gas furnaces, as measured by steady-state efficiency and AFUE. PARR identified twelve furnaces of various ages and efficiencies that were operating in residential homes in the Des Moines Iowa metropolitan area and worked with a local HVAC contractor to retrieve them and test them for steady-state efficiency and AFUE in the lab. Prior to removal, system airflow, static pressure, equipment temperature rise, and flue loss measurements were recorded for each furnace. After removal from the field the furnaces were transported to the Gas Technology Institute (GTI) laboratory, where PARR conducted steady-state efficiency and AFUE testing. The test results show that steady-state efficiency in the field was 6.4% lower than that measured for the same furnaces under standard conditions in the lab, which included tuning the furnace input and air flow rate. Comparing AFUE measured under ASHRAE standard conditions with the label value shows no reduction in efficiency for the furnaces in this study over their 15 to 24 years of operation when tuned to standard conditions. Further analysis of the data showed no significant correlation between efficiency change and the age or the rated efficiency of the furnace.
The objective of this project is to examine the impact that common installation practices and age-induced equipment degradation may have on the installed performance of natural gas furnaces, as measured by steady-state efficiency and AFUE. PARR identified twelve furnaces of various ages and efficiencies that were operating in residential homes in the Des Moines Iowa metropolitan area and worked with a local HVAC contractor to retrieve them and test them for steady-state efficiency and AFUE in the lab. Prior to removal, system airflow, static pressure, equipment temperature rise, and flue loss measurements were recorded for each furnace. After removal from the field the furnaces were transported to the Gas Technology Institute (GTI) laboratory, where PARR conducted steady-state efficiency and AFUE testing. The test results show that steady-state efficiency in the field was 6.4% lower than that measured for the same furnaces under standard conditions in the lab, which included tuning the furnace input and air flow rate. Comparing AFUE measured under ASHRAE standard conditions with the label value shows no reduction in efficiency for the furnaces in this study over their 15 to 24 years of operation when tuned to standard conditions. Further analysis of the data showed no significant correlation between efficiency change and the age or the rated efficiency of the furnace.
Natural gas furnaces are the most common space heating equipment in the U.S. residential and commercial building markets. However, current residential natural gas condensing furnaces generate substantial acidic condensate as well as significant emissions of sulfur oxides (SOx), nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons (HC), and methane (CH 4 ) contributing to environmental degradation of air, water, and soil. This report describes a novel solution to reduce the environmental impact of natural gas condensing furnaces based on the technology of a monolithic acidic gas reduction (AGR) catalyst for SOx trapping, NOx redox to nitrogen, and oxidation of formic acid, CO, HC, and CH 4 . The AGR technology offers the following benefits: (1) a neutral furnace condensate with a pH of ~7, allowing its safe release into the sewer system thus eliminating a second drainage system; (2) trapping and removing nearly all SOx emissions; (3) NOx emissions nearly at nearly 1-2 ng/J, more than 95% lower than new emissions standards in California; (4) the use of a low-cost heat exchanger as a condensing heat exchanger (HX) since the condensate is not acidic, avoiding the need for expensive stainless steel alloys; and (5) unburnt fuel energy recovery to boost efficiency.The AGR component and AGR-enabled furnace performance were broadly tested to determine their effects on long-term reliability and durability, as well as SOx storage and regeneration activity. The AGR regeneration does not impair the performance in achieving neutral condensate and ultra-low NOx emissions, and the AGR catalyst subjected to regeneration activities continued to function well and achieved slightly better annual fuel utilization efficiency (AFUE). The 400-hour reliability and durability test of the retrofitted condensing furnace with the AGR component shows that the furnace unit still achieves a neutral furnace condensate with a pH of ~7 and enables 0~3 ng/J of NOx emissions. However, the 400-hour operation slightly degraded the AFUE because of soot particle accumulation caused by frequent incomplete combustion owing to inappropriate condensate drainage during testing. Thus, proper condensate drainage is critical for AGR-enabled furnaces. Furthermore, neutron computed tomography was employed to survey the aged AGR component and demonstrate high-resolution 2D and 3D representations for the nondestructive diagnosis of the AGR component. The tomography showed that the AGR component did not deform or suffer broken AGR channels. A new AGR catalyst with low precious metal loading was preliminarily explored to identify a pathway of optimizing AGR material loading and maximizing acidic gas reduction at low cost. The new AGR component can reduce precious metal loading by 38% and still achieve neutral condensate and ultralow NOx emissions. The furnace with the AGR component of low Pt/Rh loading enables a maximum AFUE of 97%, which is meaningfully higher than the original furnace. Long-duration testing for the furnace enabled with the low precious metal loading AGR component will be vital in future research. Although the current work demonstrates a proof of concept for the AGR-enabled furnace, the AGR assembly needs to be optimized and integrated into the design of new OEM furnace products. Furthermore, the AGR technology can be applied not only for residential gas furnaces, but also for commercial rooftop units, gas heat pumps, gas-fired water heaters, combustion boilers, and other systems.
In 2010, natural gas provided 54% of total residential space heating energy the U.S. on a source basis, or 3.5 Quadrillion Btu. Natural gas burned in furnaces accounted for 92% of that total, and boilers and other equipment made up the remainder. A better understanding of installed furnace performance is a key to energy savings for this significant energy usage. Natural gas furnace performance can be measured in many ways. The annual fuel utilization efficiency (AFUE) rating provides a fixed value under specified conditions, akin to the EPA miles per gallon rating for new vehicles. The AFUE rating is provided by the manufacturer to the consumer and is a way to choose between models tested on the same basis. This value is commonly used in energy modeling calculations. ASHRAE 103 is a consensus furnace testing standard developed by the engineering community. The procedure provided in the standard covers heat-up, cool down, condensate heat loss, and steady-state conditions and an imposed oversize factor. The procedure can be used to evaluate furnace performance with specified conditions or with some variation chosen by the tester. In this report the ASHRAE 103 test result will be referred to as Annualized Efficiency (AE) to avoid confusion, and any non-standard test conditions will be noted. Aside from these two laboratory tests, steady state or flue loss efficiency can be measured in the field under many conditions; typically as found or tuned to the manufacturers recommended settings. In this report, AE and steady-state efficiency will be used as measures of furnace performance.
This report describes a Building America expert meeting hosted on July 28, 2011, by the Partnership for Advanced Residential Retrofit team. The purpose of this meeting was to identify installation practices that provide the best installed efficiency for residential gas furnaces, explain how AFUE and field efficiency can differ, and investigate the impact of installation practices on theefficiency and long-term durability of the furnace.
This report describes a Building America expert meeting hosted on July 28, 2011, by the Partnership for Advanced Residential Retrofit (PARR) team. The purpose of this meeting was to identify installation practices that provide the best installed efficiency for residential gas furnaces, explain how AFUE and field efficiency can differ, and investigate the impact of installation practices on the efficiency and long-term durability of the furnace.
This report describes a Building America expert meeting hosted on July 28, 2011, by the Partnership for Advanced Residential Retrofit (PARR) team. The purpose of this meeting was to identify installation practices that provide the best installed efficiency for residential gas furnaces, explain how AFUE and field efficiency can differ, and investigate the impact of installation practices on the efficiency and long-term durability of the furnace.
Natural gas furnaces are the most common space heating equipment in the U.S. residential and commercial building markets. However, current residential natural gas condensing furnaces generate substantial acidic condensate as well as significant emissions of sulfur oxides (SOx), nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons (HC), and methane (CH 4 ) contributing to environmental degradation of air, water, and soil. This paper describes a novel solution to reduce the environmental impact of natural gas condensing furnaces based on the technology of monolithic acidic gas reduction (AGR) catalyst for SOx trapping, NOx redox to nitrogen, and oxidation of formic acid, CO, HC, and CH 4 . This technology offers a new condensing natural gas furnace with both ultra-clean flue gas and neutral condensate. Here, a prototype of the condensing gas furnace with the AGR component is demonstrated to have condensate with pH = 7, NOx emissions of 1–2 ng/J, and an annual fuel utilization efficiency (AFUE) of 96%. The AGR component and the AGR-enabled furnace were tested for long-term reliability and durability, as well as for SOx storage and regeneration activity. In addition, this paper provides new data on measurements of the specific acidic gas content in natural gas condensing furnaces.
A clean condensing furnace was developed by using acidic gas reduction (AGR) catalysts. The AGR catalyst technology is capable of minimizing condensate acidity and NOx emissions in advanced gas furnace. In the study, different AGR catalyst materials were explored. The AGR with low Pt/Rh loading achieves an improved annual fuel utilization efficiency (AFUE) without impairing the performance in achieving neutral condensate and ultralow NOx emissions. The AGR with low Pt/Rh loading enables even better ability to convert NOx. Moreover, the low-cost AGR realizes nearly zero cold-start CO emissions, as is attractive in the battle to keep public safe from dangerous CO in furnaces.
TO4 Task 3.1 - K Hovnanian Chicago, IL DOE Challenge Home Program Certified Home Constructed and Verified Specifications DOE Challenge Home Building envelope Ceiling R-49 blown fiberglass, Grade I Walls 2x4 framing @ 16 o.c. with R-13 fiberglass batts, Grade I and 1"" R-5 extruded polystyrene (XPS) insulating sheathing Frame Floors R-38 blown fiberglass, Grade I Basement Walls R-19 fiberglass batts draped full height, Grade I Basement Slab uninsulated Windows Above Grade: ENERGY STAR certified, U=0.29, SHGC=0.28 Basement: Non ENERGY STAR certified, U=0.29, SHGC=0.24 Infiltration 2 ACH 50 Mechanical systems Heat 95% AFUE sealed combustion natural gas furnace in conditioned space Goodman GMH950703BXAF Cooling 13 SEER split system Goodman GSX130301BC DHW AO Smith Vertex 100 0.96 EF natural gas tank water heater in 2nd floor utility closet Hot Water Distribution Redesigned trunk and branch Compliant with EPA WaterSense Efficient Distribution Requirements Ducts Located 100% in conditioned space via floor joists leak free to outside (5% or less) Ventilation Central Fan Integrated Supply (CFIS) ventilation with 6"" insulated outside air duct Fan Controller: Air Cycler FRV, with 6"" motorized damper 50 CFM outside air flow, 33% duty cycle (10 minutes on, 20 minutes off); ASHRAE 62.2-2010 compliance via an exhaust fan - Panasonic FV-08VQ5 WhisperCeiling Rerturn Pathways Active Return at Master Bedroom Transfer Grilles in Secondary Bedrooms Appliances, Lighting, MELs Lights 80% ENERGY STAR certified CFL Appliances ENERGY STAR certified refrigerator, dishwasher, and clothes washer; Natural gas range/oven and clothes dryer" STRUCTURE - Test House Lot 145 - 2013 DOE Challenge Test House Task 3.1 Bolingbrook, IL 60490 House is constructed and is DOE Challenge Verified by Don Nelson, a local rater. The purpose of this project was to evaluate integrated packages of advanced measures in individual test homes to assess their performance with respect to Building America Program goals, specifically compliance with the DOE Challenge Home Program. To that end, Building Science Corporation (BSC) consulted on the construction of five test houses by three cold climate production builders in three separate U.S. cities. (1) K. Hovnanian Homes, Chicago, Illinois (2) David Weekley Homes, Denver, Colorado (3) Transformations, Inc., Devens, Massachusetts. Overall, the builders have concluded that the energy related upgrades (either through the prescriptive or performance path) represent reasonable upgrades. The builders commented that while not every improvement in specification was cost effective (as in a reasonable payback period), many were improvements that could improve the marketability of the homes and serve to attract more energy efficiency discerning prospective homeowners. However, the builders did express reservations about the associated checklists and added certifications. An increase in administrative time was observed with all builders. The checklists and certifications also inherently increase cost due to: (1) Adding services to the scope of work for various trades, such as HERS Rater and heating, ventilation, and air conditioning contractor. (2) Increased material costs related to the checklists, especially the U.S. Environmental Protection Agency Indoor airPLUS and WaterSense Efficient Hot Water Distribution requirement. Ceiling - 18" cellulose Walls - 12" open cell spray foam in double stud walls Foundation - R-10 under slab, 3 1/2" closed-cell spray foam at walls Windows - Harvey U=0.20, SHGC=0.22 Infiltration - 1.0 sq in per 100 sq ft Heating - Mini split heat pump, 10.6 HSPF, 23 SEER Cooling - Mini split heat pump, 10.6 HSPF, 23 SEER DHW - 0.97 EF instantaneous propane water heater Ventilation - bathroom exhaust fans as basic option, HRV upgrade option Adams Circle Devens MA 01434 Cavite Street Devens, MA 01434
In order to limit heating capacity degradation at -25 C (-13 F) ambient to 25%, compared to the nominal rating point capacity at 8.3 C (47 F), an extensive array of design and sizing options were investigated, based on fundamental equipment system modeling and building energy simulation. Sixteen equipment design options were evaluated in one commercial building and one residential building, respectively in seven cities. The energy simulation results were compared to three baseline cases: 100% electric resistance heating, a 9.6 HSPF single-speed heat pump unit, and 90% AFUE gas heating system. The general recommendation is that variable-speed compressors and tandem compressors, sized such that their rated heating capacity at a low speed matching the building design cooling load, are able to achieve the capacity goal at low ambient temperatures by over-speeding, for example, a home with a 3.0 ton design cooling load, a tandem heat pump could meet this cooling load running a single compressor, while running both compressors to meet heating load at low ambient temperatures in a cold climate. Energy savings and electric resistance heat reductions vary with building types, energy codes and climate zones. Oversizing a heat pump can result in larger energy saving in a less energy efficient building and colder regions due to reducing electric resistance heating. However, in a more energy-efficient building or for buildings in warmer climates, one has to consider balance between reduction of resistance heat and addition of cyclic loss.
Case study of a DOE 2015 Housing Innovation Award winning production home in the cold climate that got a HERS 38 without PV, with staggered 2x4 studs every 8”on a 2x6 plate with dense-packed R-25 cellulose, basement with 3” XPS exterior and 2: XPS under slab; a vented attic with spray foam top plates and R-60 blown cellulose; 96% AFUE furnace, 14 SEER AC, plus fresh air intake.
Case study of a DOE 2015 Housing Innovation Award winning custom home in the cold climate that got a HERS 48 without PV, with 2x6 24” on center walls with R-23 blown fiberglass, ocsf at rim joists, basement with plus 2x4 stud walls with R-23 blown fiberglass, with R-20 around slab, R-38 under slab; a vented attic with R-100 blown cellulose; 95% AFUE furnace, 14 SEER AC, ERV; heat pump water heater.
Case study of a DOE 2015 Housing Innovation Award winning production home in the hot-dry climate that got a HERS 52 without PV, or HERS -2 with PV, with 2x6 16” on center walls with R-14 ocsf plus R-4 rigid exterior; slab on grade with R-8 slab edge; sealed attic with R-31 ocsf under roof deck; 92 AFUE furnace, 15 SEER AC, 100% LED.
Case study of a DOE 2015 Housing Innovation Award winning custom home in the cold climate that got a HERS 50 without PV, or HERS 21 with PV, with 2x6 24” on center walls with R-13 ccsf plus 3.5” blown fiberglass, plus R-10 rigid exterior; R-22 ICF basement walls; vented attic with spray foam over top plates, R-65 blown fiberglass; 96 AFUE furnace, triple-pane windows, 80% LED.