Later On

A blog written for those whose interests more or less match mine.

The Rumford Fireplace

with 26 comments

The fireplace invented in 1796 by Count Rumford is a great improvement on traditional fireplaces. Rumford’s design was widely used from the time of its invention through the middle of the 19th century, and it’s still worth considering if you’re installing or renovating a traditional fireplace. I’m (re)running this piece now so you can complete the work before winter comes on.

Rumford fireplaces are tall and shallow to reflect more heat, and they have streamlined throats to eliminate turbulence and carry away the smoke with little loss of heated room air.

Rumford fireplaces were common from 1796, when Count Rumford first wrote about them, until about 1850. Jefferson had them built at Monticello, and Thoreau listed them among the modern conveniences that everyone took for granted. There are still many original Rumford fireplaces – often buried behind newer renovations-throughout the country.

Count Rumford, for whom the fireplace is named, was born Benjamin Thompson in Woburn, Massachusetts in 1753 and, because he was a loyalist, he left (abruptly) with the British in 1776. He spent much of his life as an employee of the Bavarian government where he received his title, “Count of the Holy Roman Empire.” Rumford is known primarily for the work he did on the nature of heat.

Back in England, Rumford applied his knowledge of heat to the improvement of fireplaces. He made them smaller and shallower with widely angled covings so they would radiate better. And he streamlined the throat, or in his words “rounded off the breast” so as to “remove those local hindrances which forcibly prevent the smoke from following its natural tendency to go up the chimney…”

As with any popular invention, variations exist and “pseudo-Rumfords” came to be that lacked the efficiency of the Rumford design.

The objective [is] to reflect or re-radiate as much heat out of the face of the fireplace as possible. It doesn’t hurt to whitewash the firebox or to insulate behind the firebrick. It does hurt to cover the opening with glass doors, which cut about 80% of the infrared radiation.Tall, wide shallow fireplaces [the Rumford design] tend to smoke. The other half of Rumford’s genius is his intuitive understanding of fluid dynamics – way ahead of his time. By rounding the breast to “remove those local hindrances which forcibly prevent the smoke from following its natural tendency to go up the chimney…” he essentially created a venturi, a nozzle, like an inverted carburetor, that shot the smoke and air up through the throat into the receiving smoke chamber.

Because the true Rumford design is based on the science of airflow, it does not smoke. If you have a Rumford-like fireplace that does tend to smoke, something is wrong: either it’s a pseudo-Rumford with a bad throat design, or the throat’s obstructed or has been damaged. True Rumford fireplaces simply do not smoke—that’s why they were so popular.

The fire in a Rumford fireplace is laid with a large horizontal log at the back and smaller logs placed vertically, leaning over it.

Much more information is avaialble through a Google search on “Count Rumford fireplace.”

If you have a fireplace of the genuine Rumford design, please tell us about it in the comments.

Written by Leisureguy

28 July 2006 at 11:20 am

26 Responses

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  1. Throws a lot of heat

    but must be very careful in placing and watching wood, or smoke comes out.

    Not sure I would build another one because of that problem.

    Like

    steve

    24 November 2006 at 3:57 pm

  2. Interesting. Wonder how much tolerance there is in the Venturi design of the throat—i.e., I wonder if that’s just a little bit not right, it messes everything up.

    Like

    LeisureGuy

    24 November 2006 at 4:27 pm

  3. Hi there,

    As a General Contractor and Mason, I have built numerous Rumford fireplaces, and I have never built one that didn’t work very well.

    If it is built using the proper formulas, the Rumford fireplace will work fine.

    Regarding the Venturi design of the throat, it is the most critical part of the design. Although there is some acceptable tolerance in the rolled throat and Venturi design, if there is too much variation from Count Rumford’s formulas, there could be a problem with the fireplace draw and downdrafts. This would be especially true on some very windy or damp days/nights.

    The Rumford fireplace is much more efficient than a standard fireplace. It is also a much cleaner burning fireplace.

    For anyone considering installing a masonry fireplace, I would highly recommend a Rumford fireplace.

    Best of luck in all your projects.

    Like

    Tony

    26 December 2006 at 8:42 pm

  4. I have a Rumford built in 1979 by guys who were good masons but had never done a Rumford; they used Vrest Orton’s 1974 book as a guide. It doesn’t include the rolled throat feature, so my fireplace fits all Orton’s dimensions for the throat, slanted back, etc. but it has no “roll.” And it has a chimney-top damper. Still, it works well; but I have to be somewhat careful about wood placement or it will smoke a wee bit. The masons didn’t think it would work, but the architect insisted that they follow the book, and they were really surprised that it worked! It is a solid fieldstone fireplace except for the firebricks and flue; no concrete blocks used anywhere; and after 25 years, no cracks in the mortar.

    F.W., Richmond, KY

    Like

    Frank Williams

    12 April 2007 at 11:22 am

  5. I have a Rumford design fireplace, built in 1995 in a Quaker Meeting House that I own. In the PA humidity, the fireplace odor can be stronger than I would like. The fireplace box is masonry and painted (I suppose whitewashed) white. I think whitewashing it again will help seal in the odor, however, the box walls are shiny black (I suppose creosote). Do I paint right over the black stuff? If not, how do I remove it? What is whitewash? Do I buy it or make it? Thanks sooooooo much for your help!

    Like

    Hero Quigley

    26 June 2007 at 2:01 am

  6. You went right beyond my expertise. Maybe Tony, in the comment above, could offer some sound advice. Try emailing him or visiting the web site for a contact number. Good luck.

    Like

    LeisureGuy

    26 June 2007 at 6:18 am

  7. Six years ago, I built two Rumford fireplaces in my home. The fire box is internal (on a 45 angle) and the chimneys are external. I was very careful not to exceed the specified angles for the flues, but I have a little problem that I can’t seem to figure out. The fires burn clean, hot and without any smoke, but always want to go out.

    Any suggestions?

    Thanks,
    Josh Rich

    Like

    Josh Rich

    23 September 2007 at 7:44 am

  8. I don’t know that it will help, but:

    First, obviously it’s important to have well-seasoned firewood, preferably a hardwood like oak.

    Second, I’ve read that in the Rumford fireplace one places a large log horizontally at the back, and then leans the other logs vertically over it and against the back wall.

    Finally, it might help to support the logs above the fireplace floor on a grate of some sort.

    Those are the only things that occur to me.

    Like

    LeisureGuy

    23 September 2007 at 8:13 am

  9. Why is it so hard to find a door that will work on my Rumford fireplace? I would like to put them on to close it off when we go to bed at night. I feel that has the fire dies down it sucks the heat out of the house. Also on a really windy day we do get a bit of smoke blowing back in. We just raised the chimney another 6 feet and that helped a lot. Would sure like to find doors. Jim

    Like

    JIM STAV

    16 October 2007 at 8:05 am

  10. I have four original rumford fireplaces, two of which I use often. If you get them going and keep them going they will heat the 20×15 room that they are in with no problem, even in my drafty 200 year old house.
    If the logs come too far out though, I do get some smoke.
    We love old houses. Please visit our website at http://antiquehomesofnewengland.com
    Dina

    Like

    Dina

    5 November 2007 at 7:07 pm

  11. i have recently finished building a rumford fireplace, it tends to smoke when i first start it, or if the log placement is off. help

    Like

    tony

    9 December 2007 at 2:57 pm

  12. There are many reason that could be causing this. Some of the things you should be looking at is the height of the chimney. Here in Canada the top of the chimney must be 3 feet above a 10′ ft horizontal. That also includes the trees if they are within a 10 foot radius of the chimney.

    You could be dealing with negative air pressure. This happens usually with lower level or basement installation. Open the window before you start your fireplace and don’t close the window until the chimney has been heated and drawing.

    I’m not sure what a Rumford fireplace is but all solid fuel appliances deal with the same problems.

    Like

    Deb

    17 December 2007 at 10:30 am

  13. I built a Rumford Fireplace following Vrest Orton Book Printed in 1974. I used large flue tiles cut into pieces to get the proper throte configuratiuon. I start fire with one large locust piece of wood with aproximatly 1 inch thick ashe or red oak leaned vrticaly agianst it.I keep the rest of my wood split small for a clean burning hot fire. If your fire brick do not burn off white then your wood is too big or wet/green.

    Like

    matthew braswell

    19 January 2008 at 6:29 pm

  14. Our Rumford fireplace was built when our house was built in 1980. Our house was built as a “sealed” house. That is, the house was required to meet a requirement for only a a very small allowable amount of air infiltration (heat loss) with air exchange taking place with a programmed air exchange unit. When the contractor saw that the contract required a fireplace, he had expected it to be an electric fireplace as he did not recognize the term “Rumford” in the specification for the house. We “stuck to our guns” and it resulted in an experienced mason taking on the challenge. The mason was very pleased to take on the challenge as he had never been requested to build one before.

    The fireplace is built in the Rumford design, sloping sides, vertical rear firebox back that is sloped forward about half way up to meet the breast or throat with the required opening at the top for the damper. The sloping rear wall reflects the radiant energy down and out the front of the fire box. When not in use the fireplace opening is closed off with sealed glass doors. The fireplace opening is air sealed when not in use.

    Combustion air for the fireplace comes from two openings in the bottom sides of the vertical, 45 degree sloping sides of the firebox hearth. These two openings on either side have a sliding door to regulate the admittance of the combustion air.

    The fireplace works very well. In order to start it, the front doors are opened and the combustion air doors are opened wide. I place a log about 6″- 8″ in diameter across the front of the firebox set in from the front opening by about 4″. Behind the log i place a lot of rumpled paper against the rear wall along with kindling about 1″ in dia. or smaller. i put quite a bit of kindling but not enough to choke the fire and cause a lot of smoke. While I am doing this I can feel a draft coming out of the fireplace. When I light the paper, I quickly close the doors and the initial smoke wanders around in the firebox for a very few brief moments until the heat causes the smoke to rise and the flue begins to heat up. The draft from the incoming combustion air fans the fire and it becomes a brisk hot fire very quickly. I open the doors and add larger logs onto the fire with one end of the logs resting on the log placed across the front and the other end of the logs being added are at the back of the firebox. The object is to create a lot of embers at the back wall of the firebox. Soon there is not a roaring fire but a lot of hot embers glowing along the the back wall. The heat radiating from the fireplace can become quite intense and furniture is kept well away from the hearth.

    Later, when the fire dies down the radiating heat lasts for some hours. Finally, before bedtime I close the front glass doors. The walls of the firebox particularly near the bottom are white or fire brick colour, no black soot. The ash is powdery and fine. The log placed across the front has been pushed into the fire box rear as the last log to be added to the fire.

    The only smoke is that which takes place until the flue and firebox have heated. The draft from the operation is quite strong and occasionally will whistle in the early start of the fireplace. The room is a large room with 16 ft ceiling. The chimney is probably 20 or 24ft high and is nearly as high as the roof ridge. There are no trees nearby and the only sign of fireplace operation is a shimmer from the top of the chimney. Did I mention that the fireplace is located across the diagonal corner of the room? I know the fireplace is working well when guest move away from the front and sit on the other side of the room. We love our Rumford and can recommend it to anyone considering building a fireplace.

    Like

    David Hale

    27 January 2008 at 1:39 pm

  15. In a previous incarnation, I was a chimney sweep. In reference to Hero Quigley’s question about removing the “black stuff” on his firebrick, I remembered that there is a product called ACS- Anti-Creosote. It is sprayed onto your wood on a regular basis and burned right along with the wood. It is released into the creosote build-up and, over time, makes it easier to remove the glazed on cresote. Even then it will take a sharp scraper, wire brushes (wire brushes on a rotary drill can be helpful) and elbow grease. This procedure will actually need to be done over the course of a season as it does require spraying the ACS onto the wood and then burning the wood. After a cord or so, it should be ready for the cleaning.
    Usually the creosote doesn’t bake on in the firebox as that is where the fire is the hottest. It usually glazes onto the flue tiles, further up, where there is less heat and the oils in the creosote condense back into their original state.

    Like

    Casey

    30 January 2008 at 3:02 pm

  16. I am an architect, and used to building traditional fireplaces, with no
    smoking problem whatsoever.
    Now I built my house and as David Hale comments above it is completely sealed, the consequence is that the fireplace becomes short of air and begins coughing and the smoke starts wobling with no ascending draft, finally getting inside the room.
    I tried to make a ventilation on the front part of the fireplace floor, but the cold draft from outside clashes the smoke to the back of the fireplace and bounces outside of the mouth.
    On the other hand it cools the air on top of the fire, you can feel a draft comming from above.
    The formula I use is: the mouth area/8, is the area of the chute.
    The throat opens the width of the fireplace 140cm also 1/8 of the height of the fireplace(180cm)
    My fireplace(mouth) is 6ft(180cm) tall and 4,5ft(140cm wide),2ft deep.
    I made a hole at the back of the fireplace and closing the one on the floor but I cannot get a solid draft of hot air climbing to the chute, or on the most there’s a slight current of smoke that falls out of the mouth on the corners, annoying me greatly.
    Please if you have any suggestions; I am looking for the measures to see if I can adapt my fireplace to the Rumford original.
    Thank you

    Like

    jaime boxer

    31 July 2008 at 8:49 am

  17. We do not know what to do to avoid our Rumford, from smoking up the house

    Like

    Jim

    27 November 2009 at 6:00 pm

  18. @ Jim: See above. If your fireplace smokes, it is not a Rumford fireplace (unless by chance your house is in a location that defies the laws of physics). Some possibilities:

    a. It’s a “Rumfordesque” fireplace: the general look.
    b. It’s a pseudo Rumford: a knockoff of the original but without things like the Venturi effect.
    c. It’s a true Rumford, but some damage has disrupted the airflow—possibly an obstruction and/or damage to the curved molding.

    Like

    LeisureGuy

    27 November 2009 at 6:13 pm

  19. One additional possibility occurred to me:

    d. It’s a true Rumford, but a “restoration” subverted the design and ruined the airflow.

    Like

    LeisureGuy

    29 November 2009 at 4:38 pm

  20. As a Seattle Masonry Contractor we build several Rumford Masonry Fireplaces each year. Our masons are all certified Rumford masons.

    As stated above, a Rumford Fireplace that is built right will burn hot and clean.

    Several things go into building a good Rumford Fireplace. The first thing you should know is that your local Masonry supply house can order the proper components you need to build a Rumford Fireplace.

    If not, the web will be your next stop. Just type in Rumford Fireplace Supples.

    A well built Rumford Fireplace is a joy to have; it burns hotter and cleaner then a regular fireplace.

    There are some small things that you can do to help your Rumford Fireplace. If you are in the Seattle area and are in need of help, we offer a free fireplace Inspection

    Like

    Timwmason

    19 May 2010 at 5:21 pm

  21. Constructing a fire pit is a fun and rewarding project to undertake. Fire pits come in a variety of materials such as brick, metal and stone. Creating a fire pit for warmth or cooking adds value to property and provides another area for entertaining or relaxing.

    Like

    jef brown

    6 July 2010 at 1:22 am

  22. Going back to Jim Stav who wrote in October of 2007, what do people do to keep heat from escaping up their historical Rumfords when they are not in use? Ours was built mid-1800s and I don’t want to try putting doors on it. We’re looking for something movable that we can put in once the heating season starts. Doesn’t have to be pretty, but can’t be too heavy to lift. It could be moved totally or have doors you could open and close in front. Due to cost and weight of tempered glass, I’m assuming metal here. It’s away from the hearth or has the doors open when you make a fire, then when you want to go to bed at night, or to keep heat from going up the flue when the fire’s not going, you close it up again. Is there anything out there that won’t cost your first born child?

    Like

    Jill

    22 October 2010 at 5:54 am

  23. This is for Jill, I don’t have a Rumsfords I have a reg one my fireplace chokes in the rear and has a square flu but works well. I actually load the firewood in opposite. To solve the problem when going to bed. I bought a STOVE BOARD that comes in diff. sizes usually coated in sheet metal on one side, the METAL side facing the room it looks better. ALSO buy a peice of ALUMINUM CHANNEL the width of fireplace opening and use rubber cement to glue a strip of rubber padding used primarily for tool box drawer lining to the inside of channel and the bottom to keep the board from slipping when at a slight angle. PRICE $50.00-60.00 Lowes or home depot

    Like

    Scott

    9 January 2011 at 9:45 pm

  24. We are a 4th generation masonry co. located in CT.

    I have been building slanted rumford fireplaces and crafting custom dampers for niche situations ever since reading Vrest Ortons book back in 1970.

    We believe that if Count Rumford extended his experimentations with the slanted version he would have realized that one could impede [gentle slant] the vertical rise of heat and not have the smoke escape into the room.

    For over 100 years now the slanted version has been built in homes, of which some work well and others not.

    The successful ones have the throat just behind the face[4 to 8″]and start the slope just 8 to 10″ above the floor and continue well above the breast by 12 to 16″. We have found it not necessary to round the breast because; 1] it’s not more than 4″ thick and 2] the inside wall of the face leading to the throat is plumb as is the positioning of the flue above,although one can gently slope the flue back as needed on the way up.This is in contrast to the thicker breasts of a straight version which can run over 12″ behind the face.

    Along with the thicker breast comes a shorter un-dampered throat because in positioning the throat farther back and having a thicker breast to drag smoke back under it, the damper can’t be played with or it would result in eddies.

    The basic difference created by slanting the fireback is the throat becomes longer because the side walls widen toward the face,due to angled side walls which both boxes employ.The naysayers claim this to be an excessive heat lose over the shorter throat of a straight back because Rumford stated the throat should stay basically at a fixed 4″.

    But as time passed the damper was invented which enabled the longer throat to be choked down and of course to do this, a chimney needs to have a good draft but then again, all fireplaces should have the same.The best thing to provide this is to build the chimney on the interior and close to the ridge as possible but good working slants can be built outside with proper precautions.

    In short I see it this way [and my over 35 years of fire place building successful slant backs have proven it].

    If one could capture more heat and radiate it better by slanting the back forward just behind the face [which also gets hotter], then why steer it to the back via a rounded breast and a throat and flue, both set further back than a properly built slant back, all of which aid in heat exiting straight up through the rear.

    I have a nice working slanted rumford 48″x 48″ which I built in the middle of my home some 18 years back. I usually have the damper choked to 2-3/4″ and it spews nothing but heat.

    This reduced throat opening results in at least the sq. area of the straight backs therefore equaling the heat escape but the slanted back captures and radiates far more heat into the room and front face, not to mention the extra log area at the floor which enables laying logs horizontally vs. vertical. There is also a huge difference in embedded coal capacity.

    I have a Christmas video showing my slanted Rumford burning smoke free with the damper at 2-3/4″ on my Facebook site and provide a link to Youtube, where I have others. I also answer any questions to anyone whom needs info.

    Francis Casini DBA Casini Masonry

    Like

    Francis Casini

    10 April 2011 at 1:44 pm

  25. The Orton styled 50” Rumford is now burning at a 1:30 ratio. This is throat area to fireplace opening area. My basement 36” Orton is at 1:26 with a customized vestal damper A straight can only get 1/20 due to the short throats that result from being at the rear. I have developed a damper for slanted Rumfords as well as anothe invention which discourages eddys when choked to this fantastic ratio.The basement also uses this along with the vestal. Jim Buckley cannot belive it. I will do more closeup vides for him this winter and perhaps he’ll stop saying his straight back Rumfords have the smaller throats and waste less heat!!

    Like

    Francis Casini

    22 November 2013 at 3:36 pm

  26. I built a Rumsford in 1961, from details explained in an Audels Manual about stone masonry. It had angled side walls , the rear wall was vertical to a short height, then slanted forward. The throat venturi was built by corbeling the fire brick in small increments, and finished with fire clay mortar. The front of the venturi was supported by a steel “T” angle lintel, which also served as a support for the face stone over the front opening. A cast iron damper was set atop the throat, and the smoke chamber extended upwards another ten or twelve inches to a point where the 8″ X 13″ flue liner and block structure was built upwards and exited through the roof. Fire clay brick, and fire clay mortar were used throughout. This was built entirely inside the house, and then exited through the roof. The front was faced with cut Tennessee stone and Georgia marble. The hearth was made from smooth finished cut stone. Our family enjoyed this fireplace until 1996 without any major difficulty. More than likely, the fireplace continues to function well today.

    Like

    Robert Richards

    14 January 2017 at 1:34 pm


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