THE LAB REVIEW:

INDUSTRIAL SPACE HEATING SOLUTIONSReveiw of 3 top solutions for warehouse facilities in New England

p r e s e n t e d b y m a s s e n e r g y l a b i n c .

CONTENTS

IntroductIon.......................................................................................

conepts ..............................................................................................

system types ................................................................................

comparIsons ...................................................................................

solaronIcs ......................................................................................

references ...................................................................................

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Johnson aru ..............................................................................6

cambrIdge s-serIes .................................................................6

INTRODUCTION

INTRODUCTION:

No industrial building manager has ever enjoyed paying energy bills during the heating season in New England. Yet until recently, such costs were an accepted expense and, were not a ma-jor concern given very low energy prices. However, within the past 5-10 years a confluence of several factors has resulted in much greater attention being paid to how much companies are spending to heat their facilities.

The first of these is the rising cost of energy. The wholesale price of heating oil, which many facili-ties still use to fire old boilers, has increased roughly 366% in the past 15 years. Over the same time period the trading price of natural gas has increased roughly 80%,1 and despite increasing do-mestic production, is expected to rise another 37%2 over the next 15 years.

The second is that improvements in energy efficient technology over the past 20 years have made replacing old inefficient heating equipment an economically sound investment. Systems that significantly decrease fuel consumption only pay for themselves quickly if fuel prices are high.

The final piece of the puzzle has fallen into place in the past 5 years as green living and sustain-ability have risen to the top of the nation’s social agenda. Corporations which may not have previously taken the time to consider efficiency upgrades in their facilities (despite any financial gains), are now eager to support such efforts for the sake of their public image and promoting themselves as a sustainable company.

The effects of the aforementioned factors have been even more pronounced in Massachusetts. Industrial gas rates, for instance, are the 4th highest in the country and as of May 2011, are 54% higher than those in California. Among other motivations, the challenges in supplying energy to Northeastern states have prompted state officials to enact aggressive mandates for energy reduction. Such mandates coupled with sizeable incentives to encourage building owners to implement energy reduction strategies have prompted building owners and managers to ac-tively seek ways to maximize the energy efficiency of their buildings.

There is tremendous opportunity for energy reduction in the industrial sector which accounts for more energy consumption than any other sector at 30% (commercial-19%, residential 22%, trans-portation 29%).

Concerning industrial building energy consumption, the U.S. Department of Energy notes Industrial sites employ energy-intensive systems to heat, ventilate, air condition, light, and other-wise support processes and personnel. These support functions consume up to 33% of all energy used in manufacturing sub-sectors... The energy used annually by manufacturing buildings costs industry about $12 billion and is equivalent to the energy used in 34 million passenger cars or in 11 million homes.

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U.S Energy Information Administration data from indicates that Warehouses in the U.S. spend an average of US $0.70 per square foot (ft2) on energy: About half of that cost is for natural gas and half for electricity. Energy costs for some warehouses are more than 10% of their total revenue. Heating and lighting are the two largest energy end uses for warehouses, together accounting for 64% of total warehouse energy use. That makes those systems the best targets for energy sav-ings. Accordingly, this report will focus on industrial building energy reduction solutions for build-ings that are over 100,000 ft2 with load requirements upwards of 1 mmbTu/h.

The majority of buildings in Massachusetts’ industrial building landscape, like most such spaces in the Northeast, are not actively cooled during the summer, nor are the buildings mechanically ventilated (i.e. the load is static). The general term for heaters which seek to satisfy the needs for this type of building are industrial space heaters. There are numerous industrial space heat-ing system manufacturers that claim their products yield energy savings from 10% up to 70%. The most prevalent systems in the market are considered in this evaluation. This report will review and compare the Cambridge S-series direct fired heater, the Johnson air rotation unit, and the Solar-onics SunTube low-intensity radiant heater.

Though minimal objective information is readily available on each system, Mass Energy Lab Engineers have reviewed the available research on each product and amassed a substantial amount of quantitative and qualitative data to substantiate the primary assertions made in this evaluation. It is important to note that any third party studies have been obtained from the prod-uct manufacturers themselves, and could conceivably suffer from a selection bias.The point to pay closest attention to in any case study besides the energy savings, is the heating system that has been replaced. Naturally, the more inefficient the original system the higher the savings will be when it is replaced. Many, even most, company case studies compare themselves to older unit heaters, boilers, and furnaces. These also happen to be the most inefficient systems. With this in mind, hard numbers are presented where they have been made available, but for now much of the information included in this report is subjective opinion based on the personal experience of the individuals consulted.

USEFUL CONCEPTS:

Stratification: This term refers to the vertical temperature difference that may develop between the floor and the ceiling of an indoor space. Warm air, being less dense, naturally rises while cooler air sinks. In a space where air does not mix properly, warm air exiting from a heater will retain its thermal energy and therefore remain at a higher temperature than the ambient air. This means that it will keep its buoyant property and rise, or stratify. In small spaces with 8-10 foot ceilings this is not noticeable (though it may be detected between floors). In warehouses, where roofs are regularly 30’+ the effects of stratification can be pronounced, often to the tune of 10º F or more. This creates two problems. The first is that if all the warm air is stuck at ceiling level it is not doing its job of keeping occupants and goods at ground level warm. The second problem is that by creating a greater temperature difference across the roof, the rate of energy loss through the roof increases proportionally.

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CONCEPTS

Infiltration: This is a measure of how fast the air in a building is replaced by air from the outside. Every structure “breathes” to one degree or another, with air constantly flowing in and out through gaps in walls and through open window, doors, and vents. Since it is very difficult if not impossible to measure the infiltration rate directly, ANSI standards provide an approximation of the infiltration. For large warehouses this number is 0.18-0.2 air changes per hour. In other words, approximately 20% of the air volume in the warehouse will leak out every hour and be replaced by outside air.

LEED Credits: Under the guidelines for LEED certification, credits are awarded to building proj-ects for compliance with ASHRAE standard 62.1 which governs the proper ventilation of various building types. For buildings with low occupant densities such as warehouses one of the require-ments for proper ventilation is to meet a minimum outflow rate of air from the space, in this case 0.06 cfm/ft2. If this requirement is met along with others (air cleaning, commissioning etc.) 1 LEED point is awarded toward certification. An additional point can be earned by increasing this rate to 0.078 cfm/ft2.

EPAct and Utility Incentives: In seeking to calculate the up-front cost of a project one should be aware of the available incentives that can help fund the project and potentially make it much more financially attractive. Two major programs currently in place are the Energy Policy Act (EPAct) and a utility incentive program. EPAct provides tax deductions of up to $1.80/ft2 for energy efficiency upgrades to buildings which can decrease their total energy use to 50% below ASHRAE 90.1 (2004) standards. To receive the full deduction, HVAC or other mechanical projects must me combined with lighting and envelope projects. However, businesses may still receive up to $0.60/ft2 for heating projects alone. Utility incentive programs were established as part of the American Recovery and Reinvestment Act and their details vary from state to state. Essen-tially, the federal government mandated that every gas and electric utility must take a certain amount of capacity offline each year. This is part of the government’s larger push to reduce the country’s fossil fuel dependence and decrease its carbon footprint. Money from the stimulus package has been provided to the utilities with the mandate that they dole it out to customers who reduce their demand on the utility grid. The utility pays and certain amount up front to the customer per therm or kWh conserved (anticipated) per year.

SYSTEM TYPES:

Boiler: These heating systems burn either oil or gas though most systems encountered will be oil fired. The energy converts liquid water into high pressure water or steam which is then sent to radiators throughout a building. It is the radiators which heat the air. Combustion exhaust gas is vented out a flue. Despite the fact that even modern boilers are very inefficient at heating large industrial spaces, they still represent a significant percentage of the heating systems encoun-tered in older buildings. This is because they date from an era when fuel costs were of little con-cern.

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SYSTEM TYPES

Direct Fired vs. Indirect Fired: The difference between these two systems lies in whether or not the combustion process takes place directly in the buildings inlet airstream. In a direct fired burner the fuel is burned in the incoming airstream and the exhaust gas including the products of com-bustion is vented directly into the space. In an indirect fired heater the building’s air supply and the air supplied for combustion are kept separate with heat transfer taking place between the two via a heat exchanger. However, not all the available energy is transferred from the exhaust stream in the heat exchanger and thus some is lost it leaves out the vent. This difference results in the indirect fired systems being 80-85% thermally efficient as opposed to 92% for direct fired heat-ers. Note that many direct fired systems will say that they are 100% efficient. What this number actually refers to is the combustion efficiency of the burner, which means that all the chemical energy available in the fuel is converted to heat. However, 8% of this energy resides in the latent heat that represents energy difference between liquid water and steam. Therefore, the distinc-tion between combustion and thermal efficiency must be kept in mind in to avoid confusion when comparing the stated efficiencies of two systems. Unit Heater: A form of indirect fired heater which are comparatively small and ceiling mounted. They represent roughly 60% of the space heating market, probably because they are the cheap-est to install based on first cost. However, besides boilers and furnaces they are the most costly operate.

Infrared or Radiant Tube Heater: A form of indirect fired heater which is hung from the ceiling. These gas fired units are passive which means that they bring no outside air into the space. Out-side air is heated in a combustion chamber and then passes through a tube at 350⁰F -1000⁰F. A reflector focuses the tube’s radiant heat down toward the floor warming the occupants and the building’s contents directly instead of first warming ambient air. It is able to do this because the system transfers hear via infrared radiation rather than convection as every other heater does. The heated objects, such as the floor, then reradiate some of this energy and warm the ambient air.

Air-Rotation: These large, stand-alone systems are also indirectly fired. They draw in cold air at ground level and heat it, usually with an internal gas furnace, and then duct the warm air up to the top of the unit where it is “thrown” radially outward. The thrown air hits the walls, sinks, and then returns along the floor following the layout of the racks in the warehouse.

Direct Fired 100% Make-Up Air: These systems bring in 100% outside air and will it as heat as high as 160º F before exhausting it into the building. They come in two varieties blow-thru and draw-thru. These descriptions refer to whether the blower is placed upstream or downstream of the burner section.

80/20 Make-Up Air: Another form of direct fired system whose inlet air is composed of 20% fresh outside air and 80% recirculated inside air. These units are a sort of hybrid, intended to combine high bTu/cfm ratio of direct fired heaters with the recirculation benefits of air-rotation. These sys-tems are larger than 100% MUA units, which are usually roof mounted, and can be wall mounted in the vertical positions to behave more like air-rotation units.

SYSTEM TYPES

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GENERAL SYSTEM COMPARISONS:

Cost:

Table 1 shows a general cost breakdown for some systems commonly considered for space heating applications. Estimates were provided based on a 100,000 ft2 warehouse. Total installa-tion costs are not quantified but rated in relative terms with 1 being the least expensive and 4 the most expensive.

GARD Study Efficiency Evaluation:

The only third party study that Mass Energy Lab was able to obtain which quantitatively com-pared the efficiencies of various space heater came from Cambridge Engineering. The mod-elling simulation was performed with EnergyPlus software and based on a generic 200,000 ft2 warehouse. Cases were run covering ventilation rates of 0,100%, and 130% of ASHRAE 62.1 lev-els. For each of these, maximum stratification levels of 4º F and 10º F were tested, for a total of 6 cases. Boilers and units heaters experience significant stratification while in the other systems it is much more limited. Therefore, for a given ventilation rate the energy consumption rates for the boiler and unit heater were taken from the 10º F stratification simulation run. A maximum strati-fication of 4º F was assumed for all other systems. Note that the boiler was not modeled for the cases any ventilation.

COMPARISONS

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TARGET SYSTEM ADVANTAGE AND DISADVANTAGES:

Solaronics Low-Intensity SunTube Heater:

Advantages:Control: Infrared systems can direct their radiant energy precisely to the areas where it is need-ed to warm people and equipment directly without having to heat all the air in the building. This fact makes the SunTube excellent for zonal application where only a fraction of the floor space is occupied and requires heating.

Comfort: When large bay doors open in a smaller building such as a garage all the warm air quickly rushes out and it may be some time before traditional space heaters are able to reheat all the air within the building. In contrast, infrared heaters continue to warm occupants directly via radiant energy so there is minimal loss off warmth even with a drop in air temperature. Any people and equipment entering the building will quickly feel the effects of such a heating sys-tem.

Stratification: The SunTube heats the ambient air only gradually through reradiation from warmed objects in the building. There are no jets or plumes of hot air as there are with other types of heat-ing systems. Therefore, there is generally little stratification.

Efficiency:: Solaronics claims that customers can save up to 75% on their energy bills by replacing their old heaters. The case studies provided by Solaronics and its distribution partners

(Table 1) suggest that savings will usually be over 50%.

SOLARONICS

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Installation & Maintenance: In terms of up front costs, infrared systems are relatively inexpensive compared to air-rotations units and direct fired units. The equipment cost may be higher in rela-tion to these other units, but this is more than offset by the low installation cost of infrared heaters.

Disadvantages:

Comfort: The heaters have no circulation capability and therefore hot and cold spots may de-velop within the warehouse. Air curtain heaters should be added over dock doors to prevent infiltration of cold air since passive systems do help with this.

Ventilation and Air Quality: The SunTube does not bring in fresh outside air into the space and therefore provides no indoor air quality benefit. For the same reason it can not ventilate during the summer months to bring cooler air into the space. Seperate fans or make-up air units must be installed to provide these comfort benefits.

Stratification: Although the heaters themselves may not produce hot, buoyant air, other machin-ery in within the space may still do so. Since the heaters do not circulate and mix the air this will result in stratification.

Efficiency: Though Solaronics claims a thermal efficiency of 85%-92% for the SunTube, actual ef-ficiency is in the high 70% to high 80% range.

Installation & Maintenance: In warehouses, even a small accumulation of dust on the reflectors will lower their reflectance and severely impair the unit’s effectiveness and energy efficiency. Any regular service or replacement of parts must be performed on each individual unit, often high up at ceiling level. This can be very time consuming and inconvenient. Low hanging systems over loading bays are also prone to being struck by passing forklifts which can easily damage the reflectors. Moreove, because of their smaller heat output, dozens of SunTube heaters often need to be installed to meet the heating requirements of a single warehouse. The resulting maze of gas and electrical lines clutter up the ceiling. Finally, the initial equipment cost is considerably higher than Cambridge heaters and slightly higher than air-rotation units (see Table ??). Re-placement parts are similarly expensive.

Other Considerations: Solaronics claims that the exhaust from its units can be directly vented into the space and thus act like a more efficient direct fired heater as opposed to an indirect one. Though technically feasible, this is actually a very bad idea. As mentioned previously these units provide no ventilation benefits. On the other hand they still produce large quantities of water vapors (~9 gal. liquid per unit per day) and fumes which will quickly fill the warehouse and make it an extremely unpleasant place to work.

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SOLARONICS

Bottom Line: The SunTube is a sound product which can yield significant energy savings of up to 75% if deployed properly. This infrared heater is good for use small industrial facilities (<25,000 ft2) and other buildings such as garages with comparatively large sporadic influxes of cold air. Its ability to direct radiant energy and quickly warm workers standing within its area of effect make it an excellent choice for applications where employee comfort is the primary focus. In addition, the ability to specific systems of highly variable size give it an edge in capital cost over systems such as the Cambridge for smaller heating loads. However, for space heating applications where the focus is less on the building occupants and more preventing cold damage to stored equipment merchandise the SunTube is not the proper choice. Infrared systems are much more expensive to operate as space heaters than either direct fired heaters of air rotation units. Ad-ditional ventilation and maintenance requirements should be carefully considered before pur-chasing this product.

Johnson Air-Rotation Unit:

Advantages:

Control: The Johnson heater possesses a high degree of customizability. The unit can be heated with gas, oil, or steam depending on customer preference. Humidification and energy recovery systems are available to improve air quality control and increase energy efficiency. Ventilation air can also be brought, reduce infiltration and cool the space in the summer in from outside either to improve indoor air quality.

Stratification: Of all the heating systems available air-rotation units are the best at providing a uniform temperature distribution throughout the warehouse preventing stratification. Wall-to-wall, spaces heated with a Johnson system should see temperature variations of no more than 0.25⁰F and possibly as low as 0.1⁰F. One can expect to have vertical temperature stratification of about 1.0-1.5⁰F per 10 ft. of ceiling height, possibly less.

Efficiency: An air rotation unit is more efficient and costs significantly less to run than either unit heaters or radiant heaters (See Table 1).

Installation & Maintenance: One of the primary benefits of choosing air rotation units over unit and infrared heaters is that it consolidates operations to a few large units rather than many small ones, sometimes just one. This drastically reduces the need for ductwork and piping and avoids having to cut holes in the roof or walls for ductwork (though if you’re replacing old heaters you may already be out of luck) and there is no need to worry about bracing and structural integrity. Since the entire system stands alone and sits on the facility all that is needed for heating applica-tions is to wheel it in and hook it up to a fuel line. Johnson says that this can be done by two men in roughly 1 ½ days. Our own experience here at Mass Energy Labs tells us that it usually takes 1-2 weeks to install a Cambridge heater depending on the precise application and the contractor. Maintenance is also easier once installed because all machinery including fans and heating ele-ments are located at ground level. There is no need for lift equipment or to climb on top of the roof in order to perform maintenance.

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JOHNSON ARU

Disadvantages:

Control: Many buildings will often use only one air-rotation unit to heat the entire space and this means that little if any independent zoning control is afforded to the building manager.

Ventilation and Air Quality: Although the Johnson heaters can be outfitted with ventilation capa-bilities, bringing in cold outside air during the heating season greatly reduces the system’s effi-ciency. Therefore, most units are run purely in heating mode without any ventilation.

Efficiency: Like the SunTube, the Johnson heater is indirectly fired and therefore less thermally ef-ficient than blow-thru heaters heaters. It must also circulate and process a much larger volume air than a direct fired system. In consequence, the heater uses larger blowers and fans which consume 3 times as much electricity as those in the Cambridge heater.

Additional Considerations: From an inventory standpoint, large air rotation units consume valu-able warehouse. They generally have a footprint of about 150 ft2 and in order to function prop-erly must reach nearly to the ceiling meaning they occupy an enormous volume.

Bottom Line: The question of whether or not to invest in an air-rotation unit centers around wheth-er or not you need to ventilate the space during the heating season. If the answer is “yes,” such when a LEED certification is desirable, then an air rotation unit is not the right choice for you. Though it may yield energy savings when replacing boilers and unit heaters, you’re better often going with a direct fired make-up air unit. These generally use 100% outside air and will provide the necessary ventilation without the huge increase in energy use. On the other hand, if no ven-tilation is required then an air-rotation unit is worth considering as the most energy efficient op-tion. Additional features available with the Johnson, along with its ability to deliver very precise temperature control may also make it an attractive option in certain situations where heating efficiency is not the only consideration.

Cambridge S-series Industrial Space Heater:

Advantages:

Control: The exhaust temperature can be reset manually if required.

Comfort: Like other direct fired heaters the Cambridge uses 100% outside air and therefore does not recirculate fumes or airborne particulates (e.g. cardboard and cement dust). Exhaust nozzles can also be aimed at dock doors to help prevent infiltration at keep workers warm. Since the systems are so effective at heating the air they do not need to run constantly and thus employ smaller motors. When combined with a smooth, steady ramp up operation this yields a relatively quite heating system.

Stratification: The Cambridge heater uses high velocity exhaust nozzles to promote proper mixing of the air and prevent stratification. Even for warehouses with ceilings of roughly 30 ft. a tempera-ture difference of 4º F or less may be achieved.

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CAMBRIDGES-SERIES

Efficiency: A third party study by GARD Analytics showed that for medium sized warehouses with ventilation rates ranging from 0-130% of those dictated by ASHRAE 62.1 the Cambridge S-series is the most efficient, generally by a significant margin (Figures 1). It maintains an advantage over infrared, air-rotation, and unit heaters because these systems are indirect fired as opposed to direct fired. It has an efficiency advantage over other blow-thru and draw-thru systems because it is the only direct fired heater that can produce a 160º F temperature rise. Consequently, the S-series can put out the more bTu/cfm than any other device. The result of this is that less cold outside air must be brought in, and in turn, less warm inside air must be forced out and wasted.

Installation and Maintenance: By engineering a blow-thru heater Cambridge has taken the blower out of the hot air flow downstream stream of the burner. This results in longer life for the motor, the fan belt and other components which might otherwise regularly break down. Cam-bridge offers a 2 year warranty on the S-series, and covers the burner itself for 5 years. This is in contrast to blanket 2 year warranties offered by other manufacturers. Direct fired heaters in general also have fewer moving parts when compared to boilers and air rotation units and this means fewer parts that can break. A key factor to keep in mind is the age of a heating unit. While most will operate relatively trouble-free for their first 10 years of life, after 15-20 years of ser-vice emergency repair costs may well equal or even exceed annual maintenance costs. This is not nearly as big an issue with Cambridge designed heaters for the reasons stated above. The S-series can be installed in 5 different configurations depending on user needs. First costs are lower than for air rotation units.

Drawbacks:

Ventilation and Air Quality: Because the Cambridge heater exhausts the products of combustion directly into the building condensation, and in turn mold, may become a concern in rare cases. Relief vents may also need to be added in the floor to address possible carbon monoxide issues.

Installation and Maintenance: This system is significantly more expensive to install than either in-frared or unit heating systems.

Additional Considerations: The space should be at least 100,000 ft2 to insure that annual energy savings are sufficient to justify the capital cost. Installation in smaller spaces may still be economi-cally feasible but the ROI will probably not be as attractive.

Bottom Line: For space heating applications in large factory and warehouse facilities the Cam-bridge S-series blow-thru stands alone in terms of performance, especially when LEED certifica-tion is being sought. With the potential to save 40-70% on a building’s gas energy bill and an estimated payback time of less than 3 years it is a clear first choice.

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CAMBRIDGES-SERIES

About This Report

It is our goal at Mass Energy Lab to provide the most comprehensive and objective data pos-sible on the energy efficiency products we survey in order to help you make informed business decisions. However, as mentioned at the beginning of this report, reliable quantitative data is not always available. Thus much of the information presented in this report is qualitative and based on the personal experience of several industry professionals. Combined, they have been in thou-sands of industrial spaces across the country. We consider it inevitable that some manufactur-ers of heating equipment will view this report and take issue with our characterization of certain systems. We therefore strongly encourage those companies, as well as anyone else in possession of case studies and/or other numerical data, to send it to us so that we have the opportunity to correct and expand this report. This white paper should not be viewed as a static document, but rather as a dynamic body of knowledge where additional input is always valued.

Mass Energy Lab would like to thank the following individuals for their generosity with their time knowledge which was central to compilation of this report: Bill Bissmeyer, Dennis Campbell, Frank Horstmann, Jim Melcher, Bob Rush, and Ken Williams

References:

http://www.eia.gov (Aug. 2011)

Newell, R.G. (Feb. 2011). The Long Term Outlook for Natural Gas. U.S. EIA. Retrieved August 18, 2011, from http://www.eia.gov/naturalgas/reports.cfm?t=186

Hedrick, R.L. (2009). Simulation Analysis Using EnergyPlus: Energy Performance of Warehouse Heating System. GARD Analytics, Proj. No. CAM365.

Taylor, S.T. (Sept. 2005). LEED and Standard 62.1. Retrieved August 14, 2011, from http://www.taylor-engineering.com/downloads/articles/ASHRAE%20Journal%20-%20LEED%20and%20Stan-dard%2062.1-Taylor.pdf

http://www.johnson-air.com (Aug. 2011)

http://www.cambridge-eng.com (Aug. 2011)

http://www.solaronicsusa.com (Aug. 2011)

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REFERNCES