In the News
New Literature
Hotline Newsletter
< Article Summaries
< 2009
< 2008
< 2007
< 2006
< 2005
< 2004
< 2003
< 2002
< 2001
The Hotline Newsletter
Summer 2009
ENERGY MODELING
Documented Energy Savings for
Blow-Thru® Space Heaters
Computer building simulation and energy modeling are new tools to help contractors, developers, property managers and owners select the most cost-effective energy efficient building systems. They can help obtain EPAct federal tax deductions, state and local tax incentives and utility rebates for saving energy and reducing a building’s carbon footprint. Energy modeling is also used to obtain credit points for LEED/Green building projects.
What is Energy Modeling?
It’s a process that combines building design details and weather information using computer
algorithms to calculate heating, cooling, ventilation and lighting loads hour-by-hour through a typical year
. Energy modeling is used to evaluate the performance of separate building systems by documenting predicted energy savings. It is a valuable tool for providing unbiased answers to questions pertaining to a building’s energy usage.
New Energy Modeling White Paper
Heating, ventilating and lighting consume most of the energy in non-refrigerated warehouses. Installing more efficient lighting to save electrical energy is well documented by computer modeling. However, until now there have been few energy modeling guidelines for selecting more efficient heating and ventilating equipment that accounts for 75% to 95% of the total gas used at these facilities.
A new white paper summarizes the approach, results and conclusions of the first published energy modeling analysis documenting predicted energy performance for six types of gas fired heating systems commonly used in warehouses and commercial/industrial buildings with large open spaces. The computer simulation analysis also includes a comparison to the ASHRAE 90.1 baseline heating system. A set of Best Practices Guidelines is provided at the end of the white paper.
Energy Modeling Analysis
The energy performance of six common heating systems was modeled by an experienced independent consulting firm. They used EnergyPlus software developed by the U.S. Department of Energy (DOE). This advanced building simulation software meets the requirements of the U.S. Green Building Council for determining LEED energy credit points. It conforms to the modeling requirements of ASHRAE Standard 90.1 and is an IRS approved energy modeling software for obtaining Energy Policy Act (EPAct) federal tax deductions.
A 200,000 ft² generic warehouse facility was developed for this study. Everything, including the building construction, insulation, lighting and heating system, was designed to meet ASHRAE 90.1 guidelines for energy efficiency. Internal loads included workers, forklift trucks, stored materials, equipment operation, infiltration and dock door activity. Six different building conditions were simulated for all heating systems to determine the impact on energy use resulting from different ventilation rates and different levels of temperature stratification.
Results and Conclusions
1. Direct fired, high temperature rise Blow-Thru Space Heaters always used the least amount of energy to heat/ventilate the warehouse. Energy modeling predicts 35% to 38% less gas usage (therms) compared to the ASHRAE 90.1 baseline heating system. In fact, using any of the other heater systems increased total therms required to heat the facility by 24% to 59% as shown in Figure 1.
Blow-Thru heaters use the least amount of energy to heat/ventilate large warehouses based on the following advantages of their design:
• Higher 92% efficiency vs. 80% rating for indirect fired systems
• More efficient, variable capacity, modulating control burner
• Higher 160°F maximum temperature rise/discharge temperature capability provides a high Btu/cfm ratio. This reduces the effective heating load compared to lower temperature rise draw-thru make-up air and recirculation type direct fired heating systems.
• Electrical energy is reduced by a smaller
blower motor, lower static pressure and the ability to provide both space heat and tempered ventilation using the least amount of outside air.
2. Air Turnover, Draw-Thru Make-Up Air and Recirculation type heating systems out-performed the ASHRAE 90.1 baseline heating systems by only 13% to 22%.
3. Power vented Unit Heaters, a common way to heat warehouses, were found to virtually match the ASHRAE 90.1 baseline heating system for natural gas use.
4. Although Infrared (radiant) heating is a good way to heat stationary objects and small facilities with open spaces, the computer simulation results indicate it to be a poor performer for large buildings that require both space heating and mechanical ventilation. Some manufacturers of infrared heaters recommend using their systems with a rated output 80% to 85% lower than the heat loss calculated by the ASHRAE Handbook or by turning down the space thermostat by an equivalent amount. This analysis did not incorporate either approach.