# Chapter 3 - All About Gas Fireplaces
3. What to Look For
In recent years, a great deal of effort has gone in to making good gas fireplaces. Some excellent units are available that offer a visually attractive flame, a re very efficient and can save energy in your home. The key features and terminology you will come across when shopping for a gas fireplace are discussed in the following. Types of gas fireplaces Three basic types of gas fireplaces are widely avai lable in Canada: inserts, factory-built fireplaces (zeroclearance units) and free-standing designs. Your bi ggest challenge will be sorting through the wide ra nge of models available to select a unit that is as effici ent as possible and that suits your particular need s. Insertsare used to convert existing wood-burning masonry or factory-built metal fireplaces to gas. The gas burner and simulated logs are contained in a specia l metal housing that fits into the existing firepla ce cavity. The unit has a glass front for viewing and a decora tive metal trim. Existing chimneys must be relined with an approved vent when a gas insert is installed. Figure 1. Gas Fireplace Insert in Existing Wood-Bur ning Fireplace

Zero-clearance gas fireplacesare used in installations where there is no existi ng fireplace (i.e., during new home construction or as part of a renovation project). The simulated logs and burner are inside th eir own firebox, around which is an inner and outer she ll. This type of gas fireplace can be installed ins ide the house envelope, even against an outside wall. The m anufacturer's instructions must be followed careful ly to ensure proper clearances from combustibles and that approved venting materials are used. Figure 2. Zero-Clearance Direct-Vent Gas Fireplace



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1 of 9 1/31/2012 11:02 AMFree-standing gas fireplacestypically resemble some of the new wood-burning stoves. These units tend

to be more effective in supplying heat to the house , since all of the fireplace's surfaces are exposed to the room. The glass fronts used on all of these gas fireplace s can be manufactured from tempered or ceramic glas s. Ceramic glass is slightly better at transmitting in frared heat into the room. However, its principal b enefit is that it can better withstand higher temperatures as sociated with sealed units. Figure 3. Free-Standing Gas Fireplace

Types of venting Venting is required to remove combustion gases from the firebox to the outdoors. Three options are available: natural draft venting, power venting and direct venting. Many of the gas fireplaces sold today evacuate comb ustion products using a vertical chimney (gas vent) , which takes advantage of the natural draft caused b y the temperature of the flame (hot air rises). The se 

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2 of 9 1/31/2012 11:02 AMunits have a draft hood that requires extra house a ir to isolate the burner from outside pressure fluc tuations

(see Figures 4 and 5). Figure 4. Natural Draft Fireplace with Type A Draft Hood

Figure 5. Natural Draft Fireplace with Type B Draft Hood

Natural draft fireplacestypically use a B-vent or, in an existing chimney, an approved metal liner that includes a B-vent or a flexible metal liner. Some gas fireplaces feature power venting , in which an electrical fan assists the venting pr ocess. Power venting allows units to be vented with horizontal a nd vertical flues from locations in a home where a conventional flue cannot be installed. Although pow er venting is not yet common, it can improve a fireplace's efficiency and will use less house air, as a draft hood is not usually required. With a direct-vent fireplace, outdoor combustion air is drawn directl y into the firebox through one pipe, while combustion products are exhausted through ano ther. The units are sealed, so there is no room air required for combustion and no loss of heated room air to the outdoors. Direct-vent fireplaces are typ ically installed on an outside wall, with the vent running directly through the wall, although some models ar e approved for extended horizontal and vertical flues

. Figure 6. Sidewall Venting of a Direct-Vent Gas Fireplace 

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3 of 9 1/31/2012 11:02 AMVenting may be either coaxial or collinear , as illustrated in Figures 7 and 8. Coaxial ventin g uses two

concentric pipes. The outer pipe brings combustion air in from the outdoors, and the inner pipe exhaus ts the combustion products. This is the method commonl y used for sidewall venting. Collinear venting uses two completely separate pipes: one to supply outsid e combustion air and the other to exhaust combustio n products. This method is most often used where there are space limitations when an existing fireplace and chimney have been retrofitted with a gas insert or where long vent distances and cold temperatures make condensation and vent icing a potential concern. To be installed in an energy-efficient R-2000* home , a gas fireplace must be either directvented (sealed) or power-vented. This provides an a dditional level of protection against spillage of combustion products and helps increase the appli ance's efficiency. * R-2000 is an official mark of Natural Resources C anada. Figure 7. Direct-Vent Gas Fireplace with a Vertical Coaxial Vent

Figure 8. Direct-Vent Gas Fireplace with a Vertical Collinea r Vent 

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4 of 9 1/31/2012 11:02 AMEfficiency ratings

When purchasing a gas fireplace, ask about its effi ciency first. However, a word of caution is necessa ry: many different methods have been used to measure th e efficiency of gas fireplaces, some of which can g ive misleading results. Until recently, most efficiency ratings were steady -state measurements – the maximum efficiency the fireplace could achieve operating under controlled laboratory conditions and after running at equilibr ium for a long period of time. This measurement does not ta ke into account many of the ways in which heat loss occurs in a fireplace. A steady-state rating is comp arable to the good gas mileage a car achieves when cruising on the highway, as opposed to the much low er mileage you get in start-and-stop city driving. With a gas fireplace, the actual operating efficiency of the unit once it is installed in your home will belower than the steady-state efficiency – in some cases, much l ower. The new EnerGuide Fireplace Efficiency (FE) rating The best way to determine the efficiency of a gas f ireplace is to ask for its Fireplace Efficiency rating based on the CSA-P.4 test method. Tests using this C anadian standard for measuring annual fireplace efficiency have shown that some units operated in t he 30 percent range, while the better units ranged from 50 percent to 70 percent. As of September 2003, an agreement between the Gover nment of Canada and the Heating, Refrigeration and Air Conditioning Institute of Canada (HRAI) establis hed an energy efficiency rating system for vented g as fireplaces. The EnerGuide rating system provides co nsumers with the assurance of a standardized method of testing, allowing them to accurately compare different makes and models. The testing provides a Firepl ace Efficiency (FE) rating based on products tested and certified to the Canadian Standards Association (CSA) test standard P.4.1-02. The standard assesses all gas fireplaces, whether t hey are decorative units or are used for space heat ing. It is an accurate measurement that reflects the overal l operation of the fireplace, taking into account i ts use and performance throughout the entire heating seaso n. The FE rating is expressed as a percentage; therefore, the higher the rating, the more efficien t the unit. The FE appears on the EnerGuide label a nd is presented in one of two ways, depending on whether the product literature lists only a single model or multiple models. The EnerGuide label for gas fireplaces 

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5 of 9 1/31/2012 11:02 AMThis EnerGuide label with the vented gas fireplace FE rating is shown on manufacturers' product litera ture

that features a single model. As noted in the rating system explanation in the preceding, the higher th e percentage, the more efficient the model.

This label is featured in product literature where multiple models with different FE ratings are shown . Each model number listed in the literature will identifythe EnerGuide FE rating directly beside the model number. Note that both labels show the statement “Based on CSA P.4.1-02.” This statement demonstrates that theFE rating is based on the testing method that all gas fireplaces sold in Canada must adhere to. Energy efficiency considerations Gas fireplaces are becoming popular, both for new h omes and for replacement of units in existing dwell ings. Most units are built-in, whereas others are free-standing and resemble a wood stove. If you are lookin g for a gas fireplace, consider its particular applicatio n: Are you looking for a decorative appliance or a h eating appliance? Is the unit the right size for the space , or are there supplemental ways to help move the h eat to other areas of the home? Do you understand the difference between zone heating and central heating? Consider these points: Every make and model has an EnerGuide rating, not j ust the most efficient ones. Vented gas fireplaces can look attractive and still be energy efficient. The EnerGuide label provides an FE number – the hig her the number, the better the efficiency. Higher-efficiency equipment saves energy. The actua l saving depends on location (i.e., the regional climate and cost of fuel), the efficiency of the ve nted gas fireplace and the efficiency of the house itself. Be careful when comparing the different ratings for appliances that are classed as “decorative” and “heater.” EnerGuide gas fireplaces directory A directory of gas fireplaces will be made availabl e to Canadian consumers by fall 2004. The directorywill enable you to compare the energy performance and op erating costs of similar models. Input and output ratings A gas fireplace's input rating is the amount of fue l energy the fireplace can consume in one hour. Theoutput rating is the amount of heat supplied by the firepl ace to the house. Both ratings are usually expresse d in British thermal units per hour (Btu/h) or in gigajo ules per hour (GJ/h). A high input rating does not guarantee high heat ou tput; heat output depends both on gas input and on the fireplace's efficiency. A high-efficiency fireplace burns much less gas in order to supply the same amo unt of heat compared with a low-efficiency fireplace. For example, a 20 000 Btu/h fireplace operating at 70 p ercent 

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6 of 9 1/31/2012 11:02 AMefficiency will provide the same amount of heat as a 40 000 Btu/h unit operating at 35 percent efficie ncy –

and it will use only half the fuel in doing so! Heat output, not input, is the important indicator when determining the proper size of appliance for y our needs. Remember that a bigger fireplace is not nece ssarily better. Take into consideration your home's overall heating demand as well as the area where th e fireplace will be installed, and select a unit th at will match your needs. In a small room, a fireplace with a high output rating could be overpowering and cau se overheating and discomfort, rather than cosiness. I t will also consume more fuel than necessary to hea t the room. A common problem is oversizing the fireplace for the application. A fireplace with a lower output is the obvious solution . A fireplace that allows you to “dial down” the inp ut considerably through modulation or turndown, or that has some means of m oving heat out of the room to other parts of the house, will allow for greater control of heat outpu t to prevent overheating. Electronic or intermittent ignition vs. continuous pilot lights In many gas fireplaces, a pilot light ignites the m ain burner as the unit is turned on. A pilot light is a small gas flame that, on its own, can consume from 600 to 1500 Btu of gas per hour and, if left to run continuously, can significantly increase your annua l energy costs. You will save energy and money by turning off the pilot light when the fireplace is n ot being used, especially during the summer, but al so when the fireplace is not in frequent use during the hea ting season. Other fireplaces have an automatic starter, such asan electronic ignition or another type of intermittent ignition device, that eliminates the need for a con tinuous pilot by restarting gas combustion each tim e a flame is desired. When purchasing a gas fireplace, consider one that does not have a continuous pilot light. Some homeowners prefer a fireplace with a continuou s pilot light because it gives them an auxiliary he at source that is not dependent on electricity (i.e., the fireplace will operate even when there is a pow er failure). If this is your preference, look for a un it with a simple method for shutting off the pilot and a similarly convenient and safe means of relighting t he pilot. Do not confuse this feature with most rem ote control or wall-mounted switches, which often contr ol the main gas flame while leaving the pilot to ru n continuously. Figure 9. Gas Fireplace with Pilot Light

Variable-setting controls and thermostats A variable-setting control, which allows you to adj ust heat output by regulating the fireplace's rate of gas consumption, is another energy-saving feature to lo ok for when purchasing a gas fireplace. This feature, also known as turndown, enables you to maintain better comfort levels, prevent overheating and still h ave a flame for viewing. At the same time, you may use le ss fuel by avoiding much of the energy loss that re sults when a fireplace repeatedly cycles on and off. Look for a model that has a wide turndown range. Som e gas fireplaces allow you a small turndown to only 

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7 of 9 1/31/2012 11:02 AM70 percent of full load (for a 30 000 Btu/h firepla ce, this means being able to reduce gas consumption to 21

000 Btu/h). Other models will allow you to go as lo w as 20 percent of full load (or down to 6000 Btu/h for a 30 000 Btu/h fireplace). Some fireplaces can be connected to a certain amoun t of ductwork (much like a furnace), which can help distribute heat to more remote areas of the home wh ile preventing overheating of the room in which the fireplace is installed. Many gas fireplaces also offer automatic thermostat controls, which help keep the room temperature at a more constant level by automatically adjusting the firing rate. On efficient fireplaces that have a wi de turndown range, this thermostat feature can reduce energy consumption while maintaining comfort and continuous viewing pleasure. However, on units that operate at one setting only or that have a limited turndown capability, the thermostat may end up turn ing the fireplace on and off frequently, which may affect your enjoyment of the flame and can even waste energy. Heat exchange and transfer An important factor to consider when purchasing a g as fireplace is the unit's heat-exchange capabiliti es. Gas fireplaces transfer heat to the house by two primary means: radiation and convection. Radiation is the transfer of heat from flames and h ot surfaces to solid objects, such as furniture, wa lls and people, that are in the direct path of the heat sou rce by means of infrared radiation. The hotter the source and the greater its ability to emit heat, the bette r the radiant heat transfer. Radiant heat allows pe ople to feel warm, even when the air around them may be coo l. In other words, when you can see the flame, you can be comfortably warmed by radiant heat. This cap ability distinguishes fireplaces from many other he at sources, including central furnaces. A factor worth considering is fireplace surface are a and exposure. The more a unit's surface is expose d to a room, the more readily it gives up heat by radiatio n and convection. For this reason, free-standing an d hearth-mounted fireplaces that protrude from the wa ll tend to have higher efficiencies. Figure 10. Convection and Radiant Heat

A well-designed fireplace will have channels around and behind the combustion chamber, through which room air will naturally circulate by convection. Th is is a process of heat transfer where the cool roo m air picks up heat energy from the fireplace surface cau sing air currents that transport heat throughout th e room. In addition to relying on convection, some un its have a heat exchanger that extracts more heat f rom the combustion gases and transfers it to the house. Fireplaces that have this feature, known as second ary heat exchange, will usually be more efficient than those that do not. Variable-speed fireplace fans can increase the amou nt of convective heat supplied by a fireplace by fo rcing heat into the room. These fans also improve the circulation of air throughout the room. Look for quiet fans that won't take away from your enjoyment of the fire. A ceiling fan can improve circulation of the heated air from a fireplace and pull the more buoyant hot air down from the ceiling.
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