,transcribers ,note ,emphasized text is displayed as ,italic4 ,,farmers' ,,bulletin #abcj ,,united ,,states ,,department ,,of ,,agriculture ,,chimneys ,,fireplaces ,they ,contribute to the ,health ,comfort and ,happiness of the ,farm ,family ,,how ,,to ,,build ,,them ,illustration ,,of ,,the mistakes commonly made in home building none is more frequent than faulty design and construction of chimneys and fireplaces4 ,though the use of the fireplace is one of the oldest methods of house heating there are few who understand the principles of its action1 and even experienced masons frequently fall into errors in building which seriously detract from the efficiency of the installation4 ,no defect in the construction of the house detracts more from the comfort of the home and none is a greater menace to life and property than a poor chimney and fireplace4 ,bad chimney design is also the cause of much avoidable expense in heating the house4 ,this bulletin is designed to give the householder and prospective builder1 and especially the farmer or other rural resident who builds or superintends the building of his own home1 a working knowledge of the principles to be observed in planning and building these important parts of the house1 which1 if they are observed1 will go a long way to promote the comfort of the home and insure the safety of the property4 ,contribution from the ,bureau of ,public ,roads ,,thos4 ,h4 ,mac,d,o,n,a,l,d1 ,chief ,washington1 ,d4 ,c4 ,issued1 ,december1 #aiba2 reprint1 ,april #aibb ,,chimneys ,,and ,,fireplaces4 ,a4 ,m4 ,daniels1 ,assistant ,mechanical ,engineer1 ,division of ,agricultural ,engineering1 ,bureau of ,public ,roads4 ,,contents4 ,page4 ,chimneys3 ,function of chimneys #c ,the chimney draft #d ,shapes and sizes of flues #e ,height of chimney #g ,flue linings #g ,location and wall thickness #h ,openings into the chimney #aj ,supporting the chimney #aj ,capping the chimney #ab ,chimney and roof connections #ab ,chimney connections #ab ,chimney insulation #ad ,smoke test for leakage #ad ,cleaning and repairing the flue #ae ,fireplaces3 ,essentials of fireplace construction #ae ,area of the flue #af ,the throat #ag ,smoke shelf and chamber #ah ,shape of fireplace #ai ,throat damper #ai ,placing the throat damper #bj ,size of fireplace opening #bj ,depth of fireplace opening #bj ,the hearth #ba ,the jambs #ba ,fireplace back and sides #ba ,supporting irons #ba ,improving fireplace heating #bb ,,function ,,of ,,chimneys4 ,illustration3 ,t ,,he prime function of a chimney is to produce a draft that will cause sufficient combustion and carry off the resulting smoke2 incidentally it assists ventilation4 ,many unsatisfactory heating plants and much excessive fuel consumption are due to improperly constructed chimneys1 which are the rule rather than the exception4 ,although many of these are more inefficient than dangerous1 yet reports of the ,national ,board of ,fire ,underwriters#a show that a larger number of fires are caused by defective chimney construction than by anything else4 ,the annual loss resulting from such fires is greater than the fire loss from any other cause4 ,poor chimney construction is responsible for smoke pollution of the air1 waste of fuel1 and poor heating4 #a ,dwelling ,houses1 a publication issued by the ,national ,board of ,fire ,underwriters in the interest of fire protection1 has been used as a basis for the matter relating to the requirements and construction of chimneys and methods of fire protection4 ,the most common faults in chimney construction are3 #a4 ,the use of unsuitable materials4 ,clay sewer pipe1 hollow building blocks1 or unprotected concrete should not be used4 #b4 ,improper laying of brick4 ,brick should not be laid on edge and should be properly bonded4 ,lining should be used in all brick chimneys the walls of which are less than #h inches thick4 ,lack of mortar1 especially in the perpendicular joints1 ruins many an otherwise good chimney4 #c4 ,failure to support the chimney properly4 ,it should never be carried on any timber construction of the building1 and when it rests upon the ground sufficient masonry foundation should be provided to prevent settling4 #d4 ,building inflammable material into the chimney or against it without proper insulation4 #e4 ,failure to anchor the smoke pipe properly to the chimney4 #f4 ,neglect of the connection between smoke pipe and flue or of the flue itself4 ,the connection should be tight2 rusted pipe should be replaced2 the chimney should be kept clean and the joints in the brickwork properly pointed4 #g4 ,lack of a tight flue4 ,a flue free from leakage is unusual4 ,every flue should be tight enough to prevent escape of smoke when tested as described on page #ad4 ,a leaky flue is the most frequent cause of heating troubles1 high fuel bills1 and destructive fires4 #h4 ,failure to maintain the full sectional area at the bend when a flue is offset4 #i4 ,use of the main heating apparatus flue for water heater or other auxiliary equipment4 ,the furnace or heater should have a separate flue4 #aj4 ,failure to provide a separate tight cleanout for each flue4 ,two or more otherwise good flues may be rendered inefficient if led into one cleanout1 since air may be drawn from one into another and the draft in all affected4 #aa4 ,presence of deep pockets leading to cleanouts4 ,they may cause eddying currents that are detrimental4 ,pockets should be only deep enough to permit installing a cast-iron cleanout frame and door just below the smoke pipe entrance4 ,deep pockets allow soot accumulation that may take fire4 ,,the ,,chimney ,,draft4 ,the draft depends entirely upon the chimney flue4 ,the better the flue the more satisfactory and efficient will be the operation of the entire heating apparatus4 ,the strength or intensity of the draft is dependent mainly upon the tightness1 size1 and height of the chimney flue4 ,the most common error in chimney construction is failure to distinguish between the size of flue necessary for free passage of the volume of smoke from a given amount of fuel and that which with proper height will produce the required draft4 ,a chimney may be high enough1 yet have an area too small to carry properly the volume of smoke4 ,on the other hand1 the size may be sufficient but the chimney too low to produce a draft strong enough to pull the air through the fire at a sufficiently rapid rate4 ,either fault or a combination of the two will result in unsatisfactory service4 ,draft in a chimney flue is caused by the difference in weight between a volume of air on the outside and an equal volume of products of combustion from the fire on the inside4 ,the higher the temperature of a given weight of air1 the greater is its total volume and the lighter the weight of its unit volume4 ,this produces a condition of unbalanced pressures at the base of the flue4 ,the rising of the lighter gases within the chimney tends to equalize the pressures4 ,so long as the fire burns this condition of unbalanced pressure persists1 the result being draft4 ,this is the basic principle which governs chimney action and upon which the draft depends4 ,the greater the difference between the temperature in the flue and that outside the greater the tendency toward equalization of pressure and hence the better the draft4 ,in summer the draft of a chimney is not as good as in winter because the difference in temperature between the outside air and that of the gases in the flue is less4 ,illustration3 ,round4 ,elliptical4 ,square4 ,oblong4 ,fig4 #a4--,round flues offer the least resistance to the passage of gases1 but most residence flues are made either square or oblong for structural reasons4 ,,shapes ,,and ,,sizes ,,of ,,flues4 ,the most efficient chimney is one built perfectly straight with a round or nearly round flue and a smooth interior surface4 ,there is no advantage in reducing the sectional area toward the top4 ,the cross section and height are determining factors4 ,the transverse area must be sufficient to pass the volume of air required to burn the fuel properly1 and the height must be great enough to insure against interference with the draft by adjoining buildings or projections of the same building and to produce a sufficiently strong draft4 ,loss in draft strength is due to air leakage1 and friction of the gases against the sides of the chimney4 ,a round flue 7see fig4 #a7 is the most desirable because it offers less resistance to the spirally ascending column of smoke and gases4 ,the elliptical is second choice so far as the movement of the gases is concerned1 but the difficulties that it presents in manufacture and construction eliminate this shape4 ,a rectangular chimney either square or oblong is not effective over its full transverse area2 for the rising column1 being approximately circular in section1 does not fill the corners4 ,however1 square or oblong forms are far more common than the round1 owing to the greater cost of round flue construction4 ,square flues are preferable to oblong so far as efficiency is concerned1 but in the larger sizes of house flues the oblong shape is more generally used because it fits to better advantage into the plan of the house4 ,an oblong flue should never have the long side more than #d inches greater than the short side4 ,a flue #h inches by #af inches is bad flue construction for draft purposes4 ,the sizes given in ,table #a are recommended by the ,national ,warm ,air ,heating and ,ventilating ,association4 ,like all data for both high and low pressure flues1 these sizes are based on experience1 not on scientific data1 and are subject to modification by further research4 ,the dimensions given are for unlined flues4 ,the actual inside dimensions of flue tile are slightly different because of the lack of standardization4 ,in selecting the flue for a furnace or other large heating unit an #h-;inch by #ab-;inch size should be considered the minimum for a lined or unlined flue1 and #ab inches by #ab inches the minimum for a lined or unlined flue whose height is more than #ce feet measured above the grate level4 ,if the chimney is designed for a small unit such as a laundry stove or kitchen range an #h-;inch by #h-;inch flue may be used4 ,illustration3 ,fig4 #b4--,top of chimney should be at least #b feet above the top of ridge in order that the wind currents may not be deflected down the chimney4 ,the proper size of flue depends upon the size of the heater or furnace for which is to be used4 ,all manufacturers' catalogues contain the size of the smoke pipe for each particular heater1 and from ,table #a 7minimum7 dimensions for round1 square1 and oblong flues may be selected2 or if the catalogue contains stack sizes select the proper one4 ,the flue tile to be used should have a transverse net inside area approximately equal to that of the smoke pipe4 ,table #a4 ,diameter ,diameter of smoke of smoke pipe or ,height of pipe or ,height of round ,size of chimney round ,size of chimney chimney chimney flue above chimney chimney flue above flue4 flue4 grate4 flue4 flue4 grate4 ---------------------------------------- ----------------- ,inches4 ,inches4 ,feet4 ,inches4 ,inches4 ,feet4 #h #h by #ab #ce #ae #af by #af #de #i #h by #ab #ce #af #af by #ah #de #aj #ab by #ab #ce #ag #af by #bj #ej #aa #ab by #ab #dj #ah #af by #bj #ee #ab #ab by #ab #dj #ai #bj by #bj #ee #ac #ab by #af #dj #bj #bj by #bd #fj #ad #ab by #af #de ,,height ,,of ,,chimney4 ,in ,table #a the minimum height of the chimney above the grate is given as #ce feet4 ,higher chimneys are considered more satisfactory1 and authorities claim that any flue under #dj feet in height will produce an erratic draft1 good on some days but poor on others ,the force or direction of the wind may be the cause1 or the amount of moisture in the air1 or the quality of the fuel may be responsible4 ,the higher the chimney the less will be the possibility of counter air currents and the stronger and more constant the draft4 ,soft coal and the sizes of hard coal known as pea and buckwheat are apt to cake and fill up the air spaces through the bed of the fire1 with the result that an intense draft is required to give the fuel sufficient air4 ,the top of the chimney should extend at least #c feet above flat roofs and #b feet above the ridge of peak roofs 7see figs4 #b and #c71 and it should not be on the side of the house adjacent to a large tree or a structure higher than itself 7see fig4 #d71 for these may ,cause eddies and force air down the chimney4 ,a poor draft will most likely result when the wind is blowing in the direction indicated4 ,illustration3 ,fig4 #c4--;,extensions to the chimney required ,in order that it might draw properly4 ,,flue ,,linings4 ,although chimneys are built unlined to save expense1 those properly lined with tile are undoubtedly more efficient4 ,linings prevent disintegration of mortar and bricks through the action of flue gases4 ,this disintegration and that occurring from changes in temperature result frequently in open cracks in the flue 7see fig4 #e-;,b7 which reduce or check the draft4 ,if loose brick and mortar should fall within they may lodge so as to cause partial or almost complete stoppage 7see fig4 #e-;,d74 ,the danger of this latter condition is greater if the flue be built with offsets or bends4 ,any change in direction should be made as gradual as possible and with an angle not greater than #cj degrees with the perpendicular4 ,the most important requirement for a flue lining is that it withstand high temperatures and not be subject to disintegration by ordinary flue gases4 ,it should be made of fire clay and for the purpose4 ,the thickness should be #a inch4 ,it should be set in cement mortar with the joints struck smooth on the inside4 ,each length of flue lining should be placed in position1 and the brick should then be laid around it2 if the lining is slipped down after several courses of brick have been laid1 the joints can not properly be filled with mortar and leakage is almost sure to result4 ,illustration3 ,fig4 #d4--,large trees located near chimney tops may deflect wind currents down the chimney4 ,this may be avoided by placing the chimney on the opposite side of the building4 ,well-burned clay flue linings are generally satisfactory for dwelling-house chimneys used for stoves1 ranges1 fireplaces1 and furnaces4 ,in regions where the fuel is natural gas1 hot flue gases are said to have caused linings to disintegrate and crumble off4 ,in such a case it may be necessary to use a fire clay that has stood the test or line the chimney with fire brick4 ,linings are manufactured in round1 square1 and oblong shapes1 but not in elliptical4 ,the oblong and square shapes are better adapted to brick construction than the round4 ,they permit of simpler and less expensive masonry work4 ,on the other hand1 the round shape produces better draft and is easier to clean4 ,a fireplace flue1 if straight1 should be lined from the throat continuously to the top4 ,the smoke chamber should be lined with fire clay or cement mortar one-half inch thick4 ,in case the masonry in front of the throat is less than #h inches thick the lining should start at the bottom of the lintel4 ,the hottest part of the flue is at its throat1 and if it is not lined at that point or if the masonry is not of sufficient thickness1 there is danger of overheating4 ,careful attention should be given to details of flue construction in order to assure satisfactory operation and reduce the fire hazard4 ,,location ,,and ,,wall ,,thickness4 ,the best location for the chimney is near the center of the building1 for when so located its four walls are kept warm2 cold winds can not chill it and cause it to draw poorly4 ,however1 it is not always possible to plan the arrangement of rooms so that the chimney may be thus located4 ,the outside wall of a chimney should be at least #h inches thick in order to reduce heat loss and the chance of air leakage into the flue4 ,illustration3 ,fig4 #e4--;,a4 ,an unlined chimney before use4 ,b4 ,same chimney1 after being in service4 ,frequently the heat and weather cause the mortar to disintegrate so that air leaks in through the joints1 causing a reduction in the draft4 ,c4 ,same chimney as ,a1 showing terra cotta flue lining in place4 ,d4 ,an unlined chimney with offset4 ,loose brick and mortar may fall and become lodged at the offset during construction or loosening of the points and disintegration may cause bricks from an uncapped chimney to check the draft completely4 ,if the flue is lined and the chimney is not higher than #cj feet1 its walls1 if of brick1 may be made #d inches thick1 provided adjacent inflammable material is properly insulated4 ,if unlined1 the walls should not be less than #h inches thick4 ,it is not good practice to place the linings of two flues side by side4 ,if there is more than one flue in a chimney1 the flues should be separated from each other by a division wall of brick at least #d inches thick 7see fig4 #f71 bonded into the side walls1 and the joints of the flue linings should be staggered or offset at least #f inches 7see fig4 #g74 ,this construction insures stability1 reduces the chance for air leakage between flues1 and prevents the possibility of a fire in one flue involving an adjacent flue4 ,if stone is used in chimney construction1 the walls should be at least #d inches thicker than brick walls4 ,walls of concrete chimneys should be not less than #d inches thick or else they should be reinforced in both directions2 otherwise cracking during the setting of the concrete or1 later1 due to temperature changes or unequal settlement of the foundation is apt to occur4 ,concrete blocks are not recommended1 but if they are used each block should be reinforced with steel running continuously around it and the blocks should be not less than #d inches thick4 ,they should be lined with the best flue lining4 ,all monolithic concrete chimneys with walls less than #h inches thick should be lined4 ,,openings ,,into ,,the ,,chimney4 ,it is not unusual to find an opening into a chimney other than for the smoke pipe of the main heating apparatus4 ,this is a frequent cause of unsatisfactory operation4 ,no range1 stove1 fireplace1 or ventilating register should be connected with the chimney flue built for the heating apparatus4 ,if it should be desired to use an existing abandoned fireplace chimney for a range or stove the fireplace flue should be closed tight about a foot below the place where the smoke pipe enters4 ,illustration3 ,fig4 #f4--;,a division wall of at least #d inches of brick should separate each flue from any others in the same chimney4 ,either of the arrangements shown will produce a good bond4 ,there should be but one connection with a flue1 if for no other reason than to decrease the fire hazard4 ,fires frequently occur from sparks that pass into the flue through one opening and out through another4 ,two stoves1 one on the first floor and one on the second1 may be connected with the same chimney flue1 but if the fire in the upper stove is hotter than in the lower1 the lower will have practically no draft4 ,a soot pocket provided with a door for cleaning it out is very convenient4 ,the door should be placed just below the smoke pipe opening1 and care must be taken to see that it fits snugly and is always closed so tight that no air can get in4 ,,supporting ,,the ,,chimney4 ,all chimneys should be built from the ground up4 ,none of the weight should be carried by any part of the building except the foundation4 ,proper foundations should be provided at least #ab inches wider all round than the chimney4 ,if the chimney is an exterior one1 and there is no basement or cellar1 its foundation should be started well below the frost line4 ,otherwise the base of the chimney should be at the same level as the bottom of the foundation of the building4 ,no chimney should rest upon or be carried by wooden floors1 beams1 or brackets1 nor should it be hung from wooden rafters4 ,wood construction shrinks1 and beams supporting heavy loads always deflect in time4 ,sagging of the beams injures the walls and ceilings of the house and is apt to crack the chimney and render it dangerous4 ,chimneys usually extend several feet above the roof1 exposing considerable surface to the wind1 and unless the support is stable they are likely to sway during a gale with the possibility of the joints at the roof-line opening4 ,openings in a flue at this point are especially dangerous1 for sparks from the flue may come into contact with the woodwork of the roof4 ,this swaying may also cause leaks in the roof4 ,illustration3 ,fig4 #g4--;,chimney and roof connection4 ,sheet metal ,a should have shingles ,k over it at least #d inches4 ,apron ,b bent as at ,e with base flashings ,c1 ,d1 and ,h and cap flashings ,p and ,g1 lapping over the base flashings provide watertight construction4 ,when the chimney contains two flues the joints should be separated as shown4 ,the brickwork around all fireplaces and flues should be laid with cement mortar1 as it is more resistant than lime mortar to the action of heat and flue gases4 ,it is well to use cement mortar for the entire chimney construction4 ,all mortar used for chimney construction1 except for laying firebrick1 should be proportioned as follows3 ,two bags of ,portland cement1 not less than #ahh pounds1 and one bag of dry hydrated lime1 #ej pounds1 thoroughly mixed dry1 and to this mixture should be added three times its volume of clean sand with sufficient water to produce proper consistency4 ,when dry hydrated lime is not available1 #a cubic foot of completely slaked lime putty may be substituted for the dry hydrate4 ,,capping ,,the ,,chimney4 ,brick chimneys should be capped with stone1 concrete1 or cast-iron4 ,unless a chimney is capped the top courses of brick may become loosened and therefore dangerous4 ,plain topped chimneys will last longer and are safer than those of an ornamental character4 ,the opening in the cap piece should be the full size of the flue4 ,,chimney ,,and ,,roof ,,connection4 ,where the chimney passes through the roof the construction should provide space for expansion due to temperature changes1 settlement1 or slight movement of the chimney during heavy winds4 7,see fig4 #g47 ,copper is the best material for flashings4 ,it is easier to handle than galvanized sheet-metal1 which is more often used because of its lesser cost1 but which will corrode in time1 both from inside and outside exposure4 ,tin or black iron are cheaper but will rust quickly unless frequently painted4 ,lead and zinc are expensive and should not be used for chimney flashings1 for in case of fire under the roof they will melt and leave an opening to create a draft by which the intensity of the fire will be increased4 ,illustration3 ,fig4 #h4--;,a4 ,wrong connection1 producing interference and a poor draft4 ,b4 ,correct construction1 producing a good draft by providing a free passage for the gases4 ,,chimney ,,connections4 ,proper care in setting and looking after smoke pipes connecting with chimneys would greatly lessen the number of fires chargeable to defective construction4 ,in fitting the smoke pipe no opening should be left around it1 and the pipe should not project into the flue lining4 7,see fig4 #h47 ,the joint should be made air-tight by a closely fitting collar and boiler putty or fireproof cement4 ,the proper construction is shown in figure #h-;,b1 but if the pipe extends into the flue a shelf is formed on which soot will accumulate1 the flue area will be reduced and a poor draft may result4 ,smoke pipes should enter the chimney horizontally1 and the connection through the chimney wall to the flue should be made with fire clay or metal thimbles securely and tightly set in the masonry4 ,if the walls are furred1 no wood should be within #ab inches of thimbles or any part of the smoke pipe4 ,the space between the thimble and wood furring should be covered with metal lath and plaster4 ,illustration3 ,fig4 #i4--,smoke pipe passing through a partition4 ,a1 #g_/h-;inch sides of partition2 ,b1 #b by #d studs in partition2 ,c1 ventilating holes in the double galvanized iron ventilating thimble ,d4 ,thimble should be at least #ab inches larger than pipe ,s4 ,flue holes when not in use should be closed with tight fitting metal covers4 ,if the room is papered the metal covers may also be papered1 provided there is no other smoke connection with the flue1 or provided a protective coating of asbestos paper is first applied over the metal4 ,if there is another connection the metal may become hot enough to scorch the unprotected wall paper or set it afire4 ,no smoke pipe should be permitted within #ah inches of any woodwork unless at least that half of the pipe nearest the woodwork is protected properly by #a inch or more of fireproof covering4 ,a metal casing #b inches from the upper half of the pipe is sometimes employed to protect woodwork directly above it4 ,when a smoke pipe is so protected it should never be less than #i inches from any woodwork or combustible material4 ,the storage of wooden boxes1 barrels1 or any combustible should not be permitted under or near a furnace smoke ,pipe4 ,if a smoke pipe must be carried through a wood partition the woodwork should be properly protected4 ,this can be done by cutting an opening in the partition and inserting a galvanized iron double-walled ventilating thimble at least #ab inches larger than the smoke pipe 7see fig4 #i71 or protection may be afforded by at least #d inches of brickwork or other incombustible material4 ,smoke pipes should not pass through floors1 closets1 or concealed spaces4 ,they should not enter a chimney in a garret4 ,they should be cleaned at least once a year4 ,,chimney ,,insulation4 ,all wooden construction adjacent to chimneys should be insulated4 ,a space of #b inches should be left between the outside face of a chimney and all wooden beams or joists4 ,this space should be filled with some porous1 nonmetallic1 incombustible material4 ,loose cinders serve well4 7,see fig4 #aj47 ,do not use brickwork1 mortar1 or solid concrete4 ,the filling should be done before the floor is laid1 as it not only forms a fire stop but prevents accumulation of shavings or other combustible material4 ,baseboards fastened to plaster which is directly in contact with the outside wall of a chimney should be protected by placing a layer of fireproof material at least one-eighth inch thick between the woodwork and the plaster4 7,see fig4 #aj47 ,illustration3 ,fig4 #aj4--,no woodwork should be permitted closer than #b inches to the outside face of a chimney4 ,baseboards in front of chimneys should be protected with asbestos board4 ,wooden studding1 furring1 or lathing should not under any circumstances be placed against a chimney4 ,wooden construction should be set back from the chimney as indicated in figures #aa and #ab2 or the plaster may be applied directly to the masonry or to metal lathing laid over the masonry4 ,the former is the better method1 as settlement of the chimney will not crack the plaster4 ,it is recommended that a coat of cement plaster be applied directly upon the masonry of any parts of a chimney that are to be incased by a wooden partition or other combustible construction4 ,illustration3 ,fig4 #aa4--,no wooden studding1 furring1 or lathing should be placed against the chimney4 ,it should be set back as indicated in this figure and in fig4 #ab4 ,illustration3 ,fig4 #ab4 ,,smoke ,,test ,,for ,,leakage4 ,every flue should be subjected to a smoke test before the heater is connected with it4 ,this may be done as follows3 ,build a paper1 straw1 wood1 or tar-paper fire at the base of the flue1 and when the smoke is passing in a dense column tightly block the outlet at the top by laying a wet blanket over it4 ,if leakage exists at any point1 it will immediately become apparent by the appearance of smoke at the opening4 ,flues so tested frequently reveal very bad leaks into adjoining flues or directly through the walls or between the linings and the wall4 ,when the smoke test indicates leakage1 the defect should be remedied before the chimney is accepted for use4 ,remedying such defects is usually difficult1 hence it is wise to watch the construction closely as it progresses4 ,many brick masons say that all flues leak4 ,this is not true2 every flue should be tight4 ,,cleaning ,,and ,,repairing ,,the ,,flue4 ,if a smoke test shows no leakage and the flue is straight1 a hand mirror held at the proper angle at the base affords a means of examination for obstructions4 ,usual causes of stoppage are broken tile leaning inward1 mortar accumulations1 loose bricks1 bird's nests1 partly burned paper1 soot from soft coal1 tarry deposits from burning wood1 etc4 ,a weighted bag of hay or straw attached to the end of a rope may be passed up and down the flue to clean it if there is not too great an offset in it4 ,,fireplaces4 ,the use of the fireplace is a very old method of house heating4 ,as ordinarily constructed fireplaces are not efficient and economical4 ,the only warming effect is produced by the heat given off by radiation from the back1 sides1 and hearth of the fireplace4 ,practically no heating effect is produced by convection2 that is1 by air currents4 ,the air passes through the fire1 is heated1 and passes up the chimney1 carrying with it the heat required to raise its temperature from that at which it entered the room and at the same time drawing into the room outside air of a lower temperature4 ,the effect of the cold air thus brought into the room is particularly noticeable in parts of the room farthest from the fire4 ,the open fireplace1 however1 has its place as an auxiliary to the heating plant and for the hominess that a burning fire imparts to the room4 ,if one is to be provided1 the essentials of construction should be understood and followed so that it will not smoke4 ,,essentials ,,of ,,fireplace ,,construction4 ,in order that satisfactory results may be obtained from an open fireplace1 it is essential3 ,first1 that the flue have the proper area2 second1 that the throat be correctly proportioned and located2 third1 that a properly-constructed smoke shelf and chamber be provided2 fourth1 that the chimney be carried high enough to avoid interference2 and fifth1 that the shape of the fireplace be such as to direct a maximum amount of radiated heat into the room4 ,,area ,,of ,,the ,,flue4 ,the sectional area of the flue bears a direct relation to the area of the fireplace opening4 ,the area of lined flues should be a tenth or more of that of the fireplace opening4 ,if the flues are unlined the proportion should be increased slightly because of greater friction4 ,thirteen square inches of area for the chimney flue to every square foot of fireplace opening is a good rule to follow4 ,for the fireplace shown in figure #ac-;,a1 the opening of which has an area of #h4be square feet1 there is required a flue having an area of #ajg square inches4 ,if this flue were built of brick and unlined it would probably be made #h inches by #af inches1 or #abh square inches1 because brickwork can be laid to better advantage when the dimensions of the flue are multiples of #d inches4 ,if the flue is lined the lining should have an inside area approximating #ajg square inches4 ,it is seldom possible to secure lining having the exact required area1 but the clear area should never be less than that prescribed above4 ,illustration3 ,fig4 #ac4--;,a4 ,top of throat damper is at ,,dd1 smoke shelf at ,,co4 ,side wall should not be drawn in until the height ,,dd is passed4 ,this assures full area4 ,if the drawing in is done as indicated by lines ,,ef and ,,eg1 the width of the throat becomes less than the width of the opening and causes the air currents to pile up in the corners of the throat1 resulting frequently in a smoky fireplace4 ,b4 ,correct fireplace construction4 ,failure to provide a chimney flue of sufficient sectional area is in many instances the cause of an unsatisfactory fireplace4 ,the cross section should be the same throughout the entire length of the chimney4 ,do not contract the flue at the chimney top1 for that would nullify the larger opening below2 if it is necessary to change the direction of a flue the full area should be preserved through all turns and bends1 and the change should be made as gradual as possible4 ,,the ,,throat4 ,in figure #ac-;,b is shown the throat1 the narrow opening between the fireplace and the smoke chamber4 ,correct throat construction contributes more to efficiency than any other feature except proper flue design4 ,a flue twice as large as is necessary brought straight down to the fireplace without constriction at the throat would result in a poor draft1 for the draft does not depend upon the largeness of the flue but upon its proper proportioning to the fireplace and throat4 ,the arrows indicate the upward flowing currents of warm air which are thrown forward at the throat and pass through the smoke chamber into the flue on the inner side4 ,this rapid upward passage of air causes a down current on the opposite side1 as indicated by the descending arrows4 ,the down current is not nearly as strong as the up current1 but it may be of such force that if there be no throat to the fireplace 7see fig4 #ad7 to increase the velocity of the upward current by constricting it1 the meeting of the two currents will result in smoke being forced out into the room4 ,thus it frequently happens that a fireplace has an ample flue area and yet smokes badly4 ,the influence of the throat upon the upward and downward air currents is shown in figure #ac-;,b4 ,illustration3 ,fig4 #ad4--;,fireplaces constructed like this without throat will very likely smoke4 ,the area of the throat should not be less than that of the flue4 ,its length should always be equal to the width of the fireplace opening4 7,see fig4 #ac-;,a47 ,the sides of the fireplace should be vertical until the throat is passed4 7,,dd in fig4 #ac-;,a47 ,above the throat the sides should be drawn in until the desired flue area is attained4 ,the throat should be set #h inches above the location of the lintel1 as shown in figure #ac1 ,a and ,b4 ,the wrong way to place the throat damper is shown in figure #ae4 ,the throat should not be more than #d or #e inches wide4 ,the lesser width is a safe standard4 ,if a damper is installed the width of the brick opening at the throat will depend upon the width of the frame of the damper1 the width of the throat proper being regulated by the hinged cover of the damper4 ,if the throat damper is omitted the opening should be #d inches1 as shown in figure #af4 ,the smoke shelf should not be bricked up but should conform to the dotted lines4 ,the depth of the smoke shelf should be the same for a #b-;foot as for a #aj-;foot fireplace opening4 ,proper throat construction is so necessary to a successful fireplace that the work should be carefully watched to see that the width is not made more than #d inches and that the side walls are carried up perpendicularly until the throat is passed1 so that the full length of opening is provided4 ,all masons do not appreciate these fine but necessary points4 ,many prefer their own and sometimes will ignore the proper methods4 ,it is therefore advisable to inspect the work several times a day as it progresses and thus avoid poor results4 ,when trouble is experienced in an existing fireplace that has ample flue area1 it is usually found that the formation of the throat is the cause4 ,illustration3 ,fig4 #ae4--,wrong location for throat damper4 ,the throat is so low that the accumulation of gases at the point constricted weakens rather than improves the draft with greater likelihood of a smoky fireplace4 ,note that the smoke shelf is bricked up4 ,this is wrong4 ,,smoke ,,shelf ,,and ,,chamber4 ,a smoke shelf and chamber are absolutely essential4 ,the shelf is formed by setting the brickwork back at the top of the throat to the line of the flue wall4 ,the shelf should be the full length of the throat4 ,the depth of the shelf should be not less than #d inches4 ,it may vary from this to #ab or more1 depending upon the depth of the fireplace4 ,the purpose of the smoke shelf is to change the direction of the down draft so that the hot gases at the throat will strike it approximately at a right angle instead of head on4 ,therefore the shelf should not be bricked up as shown in figures #ae and #af1 but should be made as wide as the construction will permit at a height of #h inches above the top of the fireplace opening4 ,the smoke chamber is the space extending from the top of the throat up to the bottom of the flue proper and between the side walls1 which may be drawn in after the top of the throat is passed4 ,the area at the bottom of the chamber is quite large1 since its width includes that of the throat added to the depth of the smoke shelf4 ,this space is capable of holding accumulated smoke temporarily in case a gust of wind across the top of the chimney momentarily cuts off the draft4 ,smoke might be forced into the room if there were no reservoir to hold it4 ,the smoke chamber also lessens the force of the down draft by increasing the area through which it passes4 ,if the walls are drawn inward #a foot for each #ah inches of rise1 friction is reduced and interference with the draft lessened4 ,the walls should be smooth inside1 for roughness seriously impedes the upward movement of the air currents4 ,,shape ,,of ,,the ,,fireplace4 ,the shape of the fireplace proper should be as indicated in figure #ac-;,a4 ,the back should pitch forward from a point a little less than half way from the hearth to the top of the opening1 and the sides should be beveled as indicated4 ,straight back and sides do not radiate as much heat into the room4 ,illustration3 ,fig4 #af4--,this construction without a throat damper directs the down draft so that it meets the up draft almost at the throat1 which is more faulty than the construction shown in fig4 #ae1 for there the lid of the damper deflects the down current4 ,,the ,,throat ,,damper4 ,a properly designed throat damper affords a means of regulating the fire4 ,the damper consists of a cast-iron frame with a lid hinged preferably at the back so that the width of the throat opening may be varied from nothing to #f inches4 ,there are a number of patterns on the market1 some of which are designed to support the masonry over the fireplace opening4 ,a roaring pine fire requires a full throat opening1 but slow-burning hardwood logs require but #a or #b inches of opening4 ,regulating the opening according to the kind of fire prevents waste of heat up the chimney4 ,closing the opening completely in summer keeps flies1 mosquitoes1 and other insects from entering the house by way of the chimney4 ,in houses heated by furnaces or other modern systems fireplaces without throat dampers interfere with even heating1 particularly in very cold weather4 ,an open fire must be supplied with air and the larger the fire the greater the quantity required2 a fireplace with a width of #e feet or more may pull air from distant parts of the house4 ,this air that is heated at the expenditure of fuel in the furnace is carried up the chimney and wasted1 but with a throat damper open only #a or #b inches a slow fire of hardwood can be kept going without smoking the room1 thus reducing materially the waste of hot air4 ,illustration3 ,fig4 #ag4--,smoke dampers with lids hinged in the center do not turn the up draft as well as do those hinged at the rear side4 ,,placing ,,the ,,throat ,,damper4 ,the throat damper should be as wide as the fireplace1 so the side walls should not be drawn in until after the throat is passed4 ,smoke dampers with lid hinged at the back will help the smoke shelf to turn the down draft2 if the lid is hinged in the center the downward and upward currents are apt to conflict4 ,the placing of the damper varies with the type1 but generally the bottom of the frame is built into the brickwork at the level of the top of the fireplace opening1 forming the throat and supporting the masonry above it4 ,,size ,,of ,,fireplace ,,opening4 ,pleasing proportions in the fireplace opening are desirable4 ,the width should generally be greater than the height1 but as #cj inches is about the minimum height consistent with convenience in tending the fire1 a narrow opening may be made square4 ,three feet and a half is a good maximum for height of opening unless the fireplace is over #f feet wide4 ,the higher the opening the greater the chance of a smoky fireplace4 ,a fireplace should be in harmony with the rest of the room in proportions and details4 ,this consideration and the kind of fuel to be used largely determine the size of opening4 ,generally speaking the day of large farmhouse fireplaces capable of receiving cordwood is past4 ,the tending of fires usually falls to the housewife1 and cordwood is a heavier weight than she should handle and can not be stored near at hand4 ,cordwood cut in two is easily handled2 so that a #cj-;inch width is about the minimum for farmhouses where wood is used for fuel4 ,if coal is burned the opening may be made narrower4 ,,depth ,,of ,,fireplace ,,opening4 ,unless a fireplace with a #f-;foot opening is made fully #bh inches deep1 in order that large logs will lie well inside1 the advantage of the wide opening is lost1 for the logs will have to be split4 ,a shallow opening throws out more heat than a deep one of the same width1 but can take only sticks of smaller diameter2 thus it becomes a question of preference between the greater depth which permits of large logs that burn longer and require less frequent replenishing and the shallower which takes lighter sticks and throws more heat4 ,in small fireplaces a depth of #ab inches will permit good draft if the throat is constructed as explained above1 but a minimum depth of #ah inches is advised1 to lessen the danger of brands falling out on the floor4 ,wire guards should be placed in front of all fireplaces4 ,in general1 the wider the opening the greater should be the depth4 ,,the ,,hearth4 ,the hearth should be flush with the floor1 for sweepings may then be brushed into the fireplace4 ,an ash dump located in the hearth near the back of the fireplace is convenient for clearing ashes and other refuse from the hearth provided there is space below for an ash pit4 ,the dump consists of a cast-iron metal frame1 with pivoted cover1 through which the refuse can be brushed into the ash pit below4 ,the ash pit should be of perfectly tight masonry and provided with a tightly fitting cleanout door4 ,if a warm-air flue1 as described on page #bg1 is provided1 the ash dump will have to be located near one side of the hearth instead of in the center4 ,,the ,,jambs4 ,the jambs of the fireplace should be of sufficient width to give stability to the structure both actually and in appearance4 ,for a fireplace opening #c feet wide or less1 #af inches is generally sufficient2 for wider openings similar proportions should be kept4 ,greater widths may be required to harmonize with the proportions of the rooms1 and the above should be taken as a minimum4 ,,fireplace ,,back ,,and ,,sides4 ,the back and sides of the fireplace should be constructed of firebrick only4 ,the bricks should be laid flat with the long sides exposed1 for if placed with the face exposed there is danger of their falling out4 ,,supporting ,,irons4 ,in small fireplaces sagging of the arch over the opening seldom occurs1 but in fireplaces over #d feet wide it is not uncommon4 ,it is due to insufficient support of the masonry4 ,except in massive construction there generally is not sufficient masonry at the sides of the opening to resist the thrust of arch construction2 hence it is usual to support the masonry with iron1 which1 if too light1 will sag4 ,too small an iron will become so hot that its tensile strength is lowered until it bends4 ,a heavy flat bar at least one-half inch thick is sometimes used or a ,t-bar which has greater strength1 but less metal2 the wider the opening the heavier the bar required4 ,,improving ,,fireplace ,,heating4 ,a number of patents have been obtained for improvements in fireplace heating4 ,most of them1 depending on the fact that hot air rises1 deliver air heated in or around the fireplace through a register1 located above the fire1 into the upper part of the room1 which is always the warmest part4 ,furthermore1 they require a specially built chimney1 precluding the installation of such a device in an existing fireplace4 ,unless fresh outside air is supplied there is no improvement in the warming of the room4 ,patent ,no4 #abeaiaf1 issued to ,joseph ,parsons1 of ,lakeville1 ,conn41 and by him assigned to the ,united ,states ,government1 presents means of greatly increasing the efficiency of fireplace heating4 ,the inventor's claim differs from other claims for improving fireplace heating in that the operation of his device depends upon the suction created in the chimney by the hot air rising from the fireplace and therefore makes possible the delivery of heated air through a register located at any place in the room or at the hearth4 ,furthermore1 it permits of installation of one of the simpler types in an existing chimney4 ,for a fire to burn it must be supplied with oxygen4 ,if a fire were built in a fireplace in an air-tight room it would go out as soon as the oxygen present had been consumed unless a down draft in the chimney supplied the needed air4 ,as our fireplace fires do not go out so long as they are fed with fuel it is obvious that the required air supply is obtained from somewhere4 ,any one who has depended upon a fireplace to heat a room knows that the part of the room farthest from the fire is the coldest and that the temperature around the windows is especially low4 ,in fact the harder the fire burns the colder it is at the windows4 ,the fire must have air1 and as cracks exist around windows and doors the air enters through them4 ,the volume entering is equal to that passing up the chimney4 ,this air comes from outside at a low temperature4 ,figure #ah illustrates how a fireplace fire supplies its needs4 ,when it grows colder outside a bigger fire is made4 ,the bigger the blaze the greater the quantity of outside air drawn into the room through every crack and crevice until1 when the outside temperature gets below the freezing point1 there is no comfort in the room beyond the immediate vicinity of the fire4 ,illustration3 ,fig4 #ah4--;,all air required for feeding the fire must pass through the room1 entering through cracks around windows and doors and producing an uncomfortable temperature in all parts of the room except near the hearth4 ,if a room were so tight that the air leakage were insufficient to supply a fireplace fire1 it would not burn properly and would smoke4 ,if a pane of glass were removed from a window cold air would rush in through the opening4 ,if the glass were replaced and an opening of equal area be made through the chimney1 as shown in figures #ai1 ,a and ,b1 so that air could be admitted into the room as indicated by the arrows in the plan1 figure #ai-;,b1 an equal volume of cold air would be drawn through this opening4 ,as it comes into contact with the metal form the air becomes heated1 so that when delivered into the room its temperature would be #ajj degrees or higher1 depending upon the radiating surface of the hearth1 assuming an outside temperature of #cb degrees4 7,tests by the writer have shown this temperature to be higher than #abe degrees47 ,if the chimney opening be closed and the pane of glass be again removed the temperature of the air entering through the window would be #cb degrees4 ,it is obvious that the room will be more effectually heated when the air required for combustion is supplied at a high temperature than when supplied through cracks and crevices at a low temperature4 ,all our homes should be made fairly tight for greater comfort in winter4 ,in such a house1 with doors and windows closed1 the suction caused by the fire can thus be utilized to draw into the room outside air heated in passing through a metal flue on which the fire is burning4 ,the principle may be applied in various forms4 ,figure #ai-;,a illustrates a simple form for use in connection with an outside chimney4 ,a piece of galvanized sheet iron is bent to the proper form and set into the fireplace so as to leave an air space between it and the back and sides of the fireplace4 ,an opening to the outside is made by removing two or three courses of brick4 ,air enters through this1 becomes heated by contact with the metal1 and is delivered into the room at the sides of the fireplace1 as indicated in the plan of figure #ai-;,b4 ,it immediately rises within the room1 gives up part of its heat1 and eventually whirls about and into the fire1 as indicated by the arrows in figure #ai-;,a4 ,this form would not necessarily heat the entire room effectually2 it would1 however1 supply heated air for the fire in volume sufficient to replace or materially reduce the quantity of cold air which would otherwise enter through window and door cracks4 ,with a brisk fire burning1 a rush of warm air can be felt #f or #h feet away from the fireplace4 ,illustration3 ,,perspective ,illustration3 ,fig4 #ai4--,simple form of warm-air flue for outside chimney4 ,air required for feeding the fire is brought in from the outside around a metal form set in the fireplace1 with a space between it and the back and sides of the brickwork4 ,as the cold outside air passes around the metal it becomes heated and is delivered into the room at a temperature much higher than where it is pulled in through window and door cracks4 ,the result is a much more comfortable room4 ,this simple form may be built as follows3 ,a piece of roofing tin about #f inches wider than the height of the fireplace opening1 with length equal to the width of the opening plus twice the depth of the side1 should be secured4 ,it should then be marked and cut as indicated in the form 7fig4 #ai-;,b71 and bent into a shape similar to that shown in the perspective1 same figure4 ,when placing it1 there should be a space left between the tin and the brickwork at both back and top4 ,the back and sides at the top should be bent back #b inches to meet the brickwork4 ,the crack or joint should be tightly closed with asbestos or furnace cement4 ,the tin form rests on the #d-;inch bottom flange4 ,the joint here can be made tight by placing a few brick on the flange and covering with ashes1 or a metal plate cut to the proper shape may be laid upon and preferably riveted to the lower flanges of the back and sides4 ,the form should be as high as the opening and the metal sides should project about #c inches beyond the jambs1 so as to throw the heated air well out into the room4 ,a one-fourth-inch rod placed across the top of the tin form directly under the arch iron of the fireplace assists in holding the top of the tin firmly against the brickwork4 ,illustration3 ,fig4 #bj4--,simple form of warm-air flue for inside chimney4 ,illustration3 ,fig4 #ba4--;,improved form of warm-air flue for ,inside chimney4 ,the increased radiating surface obtained by conducting the metal flue up the back of the fireplace heats the air to a higher temperature so that it is delivered into the room farther from the outlet duct4 ,figure #bj shows a simple form for use with an inside chimney4 ,a hole may be cut in the hearth on one side and connected with the outside by means of a passage through the chimney foundation4 ,the manner of providing this passage will depend upon the construction in the particular case4 ,a galvanized sheet-metal box with a division plate extending part way through it is set on the hearth4 ,the side over the opening is bent down in front1 as at ,a1 so that the entering cold air must pass to the rear around the division plate and then out into the room in front of the hearth1 as at ,b4 ,the fire1 on top of the metal flue1 heats the air issuing at ,b as it flows under it4 ,figure #ba shows an improved form in which the flue and division plate are extended up the back of the fireplace4 ,this presents considerably more radiating surface1 so that the air can be heated to a higher temperature4 ,the air issuing from this flue at ,b is discharged farther out into the room4 ,if there is a cellar under the floor a metal duct must be employed to bring fresh air from an opening in the outside wall1 just below the joists1 to the hole in the hearth4 ,cellar air should never be sucked through the flue4 ,all openings under the house or through the wall should be screened to keep out rats and mice1 and doors should be provided to close the openings entirely if desired4 ,illustration3 ,fig4 #bb4--;,improved form of warm-air flue with floor register4 ,this method increases the efficiency of fireplaces many times by delivering the air that must be supplied to the fire into the room at temperatures of #ajj and higher1 depending upon the form and extent of the heating surface at the back of the fireplace1 and delivering it to the coldest part of the room so that heat is distributed more effectively and the entrance of cold air around windows and doors is reduced to a minimum4 ,figure #bb shows a more elaborate installation4 ,this insures very satisfactory heating with a fireplace fire4 ,the piece ,a ,b ,c ,d of galvanized metal has a rectangular cross section4 ,two or three courses of brickwork are omitted and the metal duct is set into the fireplace1 so that radiation from the fire impinges upon its surface from ,b to ,d4 ,the air entering from outside at ,,ae is heated as it passes through the flue behind and under the fire and is carried through another rectangular duct under the floor to a register located in a far part of the room4 ,out of this register air in large volume is discharged at a high temperature4 ,this air heats the far part of the room and other parts as it travels from the register upward and through the room to the fireplace4 ,thus the fireplace heats the room by convection of heat as well as by radiation1 and all parts of the room are more comfortable than if radiation alone were depended upon4 ,a test of an installation similar to that shown in figure #bb was made by the writer4 ,the fireplace and suction flue were built in a cabin measuring #bd feet square by #i feet high4 ,the test was conducted late in ,november on a night when the outside temperature was #bd ,f4 ,it was the first fire built in the fireplace in that season1 consequently all the materials of the building were cold4 ,the room was practically air-tight2 very little leakage could be felt around the windows4 ,a temperature of slightly over #ajj was recorded directly over the register1 in the center of the room it was #gb1 and in the farthest corner a thermometer1 hung about #ah inches from the wall between two windows1 showed #fe4 ,thus the efficiency of fireplaces may be materially increased1 the degree depending upon the character of the air duct installed4 ,even in the simple types the air required to make the fire burn enters the room at a higher temperature at the floor instead of around windows and doors at a low temperature2 windows and doors may therefore be made tight1 so as to reduce the cold-air leakage4 ,the type with a register in the far part of the room supplies heat to parts of the room or to an adjoining room1 which would receive little heat if radiation only were relied upon4 ,this means of improving fireplace heating is particularly adapted to small houses in the ,south1 where the open fire is the most common method of house heating4 ,as the simple types require only galvanized ,sheet metal bent at right angles1 it is within the means and ability of many to supply themselves with flues of their own making4 ,,washington3 ,,government ,,printing ,,office3 #aiba ,transcriber ,note ,illustrations were moved so as not to split paragraphs4 ,hyphenization has been standardized to the most common form4