A Really Large Fireplace?

I am designing a large fireplace for a hotel in North Carolina. The hearth opening is approximately 8'-0" wide x 4'-0" high. Do you have any guidelines for a fireplace this large? We have plenty of information for residential scale fireplaces, but nothing for something this large.

Thanks for your time and trouble. David

Hi David,

No, we don't have any information on large conventional fireplaces. My only advice would be to have your liability insurance paid up because so many of these fireplaces fail to function properly. The key variable is not so much flue size and height as it is the pressure difference in that part of the hotel caused by air handlers and exhaust fans. The best insurance is to make sure that area is always pressurized relative to outdoors.



Designing a Fireplace

Hi. You have a great website. We are looking for a design for a forced air fireplace. We are building our own home/fireplace. Thanks for your help. Gina

Hi Gina,

We don't think wood burning appliance design and construction is a do-it-yourself kind of job. I would strongly recommend that you buy a good factory-built, EPA certified fireplace and then use your own skills and creativity to design and install the facing materials and mantel that make it your own special fireplace. Leave the design of its internal workings to people and companies that have spent decades of effort getting it right.



Wood Burning Fireplace vs. Gas

We are building a new home. My husband would like to put in a wood-burning fireplace. He thinks gas fireplaces are too "fake". I can't say I disagree with him but I know gas fireplaces are more efficient, easier to use, etc.

The sales people encourage us to put in gas as well. I would like us to make an educated decision on this - do you have any suggestions? I look forward to hearing from you. Sincerely, Rachel

Hi Rachel,

In addition to what you can read on our site about why you might want to choose wood, and suggestions about what type of wood burning fireplace to go with, here is more food for thought on the subject:

You should buy a gas fireplace if:

  • you live in an urban condo or apartment
  • when you look at an operating gas fireplace it doesn't look fake to you
  • the thought of wood chips and ash dust near your hearth is truly scary
  • you don't worry about escalating fossil fuel prices
  • a broken fingernail is considered a crisis of sorts
  • you prefer take-out to home cooked meals
  • you don't mind emitting greenhouse gases from your hearth

You should buy a wood fireplace if:

  • you grow flower gardens or a vegetable garden
  • the idea of moving and stacking firewood sounds like fun
  • you find the concept of self-sufficiency appealing
  • getting to build a fire on the hearth is a form of compensation for the fact that summer is over
  • you can't take your eyes off a natural fire
  • you'd rather not suffer in the cold when the power goes off in a storm
  • you like to stay in touch with the natural world

If a fireplace retailer tries to talk you into a gas fireplace, you should not buy from that retailer, particularly if you end up going with wood. Gas fireplaces are not more efficient than wood. You can buy a woodburning fireplace that delivers at least 75% net seasonal efficiency which is competitive with just about any gas fireplace.

If you decide on wood, we strongly recommend either a masonry heater or an EPA certified factory-built fireplace. If you build a conventional masonry fireplace, it is our view that you are throwing your money away and that it will probably behave badly in your new house.



Two-sided Fireplace

Hi...I reviewed the answers in your installation section...I'm not sure if your objection to Bruce the architect's design was the see-through nature of the fireplace, or the overall size, so I just wanted to check.

We are planning a cottage guest-house (that will be used in the winter) of about 500 sq. ft., and we were hoping to have a single fireplace with a glass face on the living room and another glass face on the opposite side of the fireplace, facing the bedroom. Would this have a large impact on the efficiency / safety of the fireplace?

Thank you for any information, Brenda

Hi Brenda,

See-through fireplaces are usually troublesome when they don't have glass doors or when the doors are open because the ratio of hearth opening to chimney area is too large so they tend to spill smoke into the room. You say you intend to put glass doors on both sides, so smoke spillage may not be a big problem, but be prepared to clean the glass often, like after every fire.

There are a few factory-built, two sided fireplaces that I don't mind recommending because they have reasonable combustion features and a heat exchanger, and air-wash to keep the glass clear. One is made by RSF, but there is one or two others. You might see if you can find a dealer so you can at least have a look at them.

A conventional two-sided masonry fireplace is more likely to be a wood hog and not provide much heat. If all you want is a decorative fire without heat, you are probably at the wrong web site because, as I think we make quite clear, we don't support these for environmental reasons.



Giving up on a two-sided fireplace?

We purchased our home about three years ago and it had a beautiful see-through fireplace between the living room and dinning room. We get next to no heat from it unless you are standing right in front of it. I have tons of concerns. First, wasting firewood, wasting the conventional home heat, and wasting money. I also have environmental concerns; we are not only polluting the outside, but it frequently drafts back into living room so we are polluting the inside.

The question; is our solution only a single sided insert? I have looked online and have had no luck in finding a two sided insert. Will doors on both sides increase the efficiency enough to use this fireplace again? Or should I just give up and find a nice bouquet of fake flowers to stick in there permanently?


Hi Mike,

You can't find a two-sided insert because there are none that are EPA certified so we can recommend them. There is no way that a manufacturer could pass EPA's emissions test with an expanse of glass on two sides of the firebox. You could put doors on both sides, but they will probably block most of the heat so there would be hardly any efficiency improvement; plus they will soot up during every fire.

Here's an idea: Put a good insert in one side and put the fake flower arrangement on the other side.



Loss of Central Heat with Use of Fireplace?

I told my friend Ann that I planned to keep my thermostat lower this winter and use my fireplace to save on utility bills. She felt I would increase my bills because of heat loss up the chimney. When there is an active fire in a fireplace will central heat be lost up the chimney? I would love to get this resolved. Ann for years has avoided using her lovely fireplace for this very notion. I grew up with a fireplace as the main heat. I never questioned this before.

Thank you, Carrie

Hi Carrie (and Ann),

This is a long-standing argument among wood heat and energy specialists, and some who see themselves as experts have never managed to understand why net energy from conventional fireplaces is so low.

First, a clarification. When we say that a conventional fireplace can produce zero efficiency or less, we are talking about a fireplace without doors or one operated with doors open and the situation is always worse when there is a large indoor/outdoor temperature difference, i.e. when it is cold outside. If the outside temperature is only 5 or 10 degrees below room temperature, you can actually gain some heat from an open fireplace, particularly if the fireplace is massive and some of the heat is stored in the masonry.

Any air passing through the combustion and venting system that doesn't participate in the combustion reaction is called excess air; that is, air from which no oxygen reacts with the carbon and hydrogen from the wood to produce heat and light. It turns out that all combustion reactions require quite a bit of excess air, partly to produce turbulence in the chamber and partly because there is no way that all the oxygen molecules in a given volume of air can be easily reacted, so you have to provide extra. This is true for all combustion reactions, from gas and oil furnaces to cars and airplanes. Excess air is expressed as a percentage of the amount of air theoretically needed for combustion.

A good wood stove will run at low excess air levels, maybe only 160%, or 60% more than is strictly required. But that open fireplace will run 1000% or 1500% excess air or more depending on its design and how big a fire you put on and how you set the damper. Excess air kills efficiency in two ways: first it 'rinses' much of the heat produced right up the chimney and out of the house so little heat is delivered to the room, and second, the air rushing up the chimney must be replaced by outside air which must be heated up to room temperature, at a considerable energy loss.

Plus, open fireplaces don't have heat exchangers, so most of the heat you gain is radiation right off the flames. Most of the heat produced gets sucked right back up the chimney. Remember the centuries old wingback chairs? The wings are to trap the radiation from the open fire around your body and to keep the cold draft from under doors and windows that is being sucked towards the fire, off your back.

If you want to shield your household from high conventional energy costs, the most effective, economical and safe way to do it is have an EPA certified fireplace insert installed in your fireplace. You would be amazed at the performance difference and the relatively tiny amount of wood you would burn compared to the fireplace. You are probably looking at more than $3000 for a fully installed insert with a stainless steel liner to the top of the chimney, so it is a serious commitment.

I think you should try your fireplace, but I would be very surprised if it produced much useful heat, unless you live in a very warm place. Once it gets cold out, why not turn the thermostat right off, build a fire and see what happens. Most people find that the house gets cold, and quickly too.

On the other hand, if you had a fireplace with doors and a circulation chamber around the firebox with vents top and bottom to the room and you ran it with the doors closed, you might get some heat, but usually the efficiency is quite low, typically in the 20% range, compared to 60 to 70% for a good insert.

Ann was right on this one.



Insulating Above a Fireplace

I have what is hopefully a simple question. My fireplace is installed inside what is basically a triangle created by the walls of two rooms and a hallway. The walls that border the fireplace are not insulated and allow heat from the attic to enter the house in the summer and allow warm air to leave the house in the winter. When looking down from the attic one can see the fireplace and the uninsulated walls. I would like to insulate this space by placing an insulated barrier around the flue up in the attic. The flue is triple wall pipe and the required offset from the flue to flammable material is indicated by a sticker placed on the pipe. Is it safe to insulate above a fireplace like this? What are the code requirements? I live in Southeast Georgia, so the fireplace is not used that much. I am just afraid that if I insulate above the fireplace, even though there would be over 5' of clearance, that it will get too hot in the walls. Thank you.


Hi Bryan,

It is a good thing you sent the drawing, because I had misunderstood the location you want to put insulation.

Yes, you can go ahead and insulate that area, provided you leave the required clearance around the chimney, which is usually 2", but I can't be sure. There are standard certified components for these chimneys called attic radiation/ insulation shields, that are designed to sit in the framed joist space where the chimney passes through. These shields establish the minimum clearance and most of them are closed at the top with a sloped shape so you could actually blow insulation in without having it remain against the chimney surface. You can achieve the same thing by, for example, forming a sheet metal cylinder around the chimney to keep the insulation back. The advantage of the certified component is that it will also keep rodent nests out of the space next to the chimney. Once you are finished insulating, be sure there is no insulation material within the 2" installation clearance.



Fireplace Odors

I enjoyed your website. I will be looking at the other links for more information. The questions and answers helped but didn't specifically identify the problem with my fireplace.

I purchased a 15 year old home a few years ago. I've used the fireplace exactly 4 times with very undesirable effects.

The house is a two story home with a great room behind the garage which serves as a family room with the fireplace on the outside wall. There is a cathedral ceiling which goes up to the second floor loft ( a common design in this neighborhood). The brick/clay fireplace is on an outside wall and the brick chimney is high enough only to meet code and does not reach above the peak of the house. There are two smaller gas forced air furnaces in the basement (up & down) and they are 20 ft. away from the chimney and therefore require a vent fan that runs on the flue. Whenever I use the fireplace the house smells strongly of soot for days afterward even if I clean the ashes. It is so strong you would expect to see fire damage somewhere. Although I hadn't found your website yet I selected a reputable chimney sweep for an opinion. He seemed to be looking for some brickwork at the tune of $1,000.00 and didn't seem to offer any solution to the problem. ( The only worthwhile mumbling may have been about finishing off the smoke chamber to make is smooth.)      A heating contractor installed a fresh air vent into the basement for the furnaces but this doesn't help and the vacuum from the furnace exhaust fan actually pulls the basement door tightly closed when it turns on (so much for the fresh air intake providing the makeup air and breaking the vacuum on the house.

These contractors are well-intentioned however they are not overpowering in their engineering knowledge. Or , maybe they are trying to cover up a poor design.

Give your readers some good advice. If you build a fireplace or have a chimney in a new home put it in the center of the house where civilized man has been building it for centuries. They draft better and don't cause problems like mine. In my old house with two old converted gas boilers you could feel the draft in the flue even in the summer. The old-timers knew how to build better 80 years ago.

Do you have any suggestions for me or should I move and forget about it? My compliments to you on your web-site!


Hi Richard,

Your analysis is correct. Have you seen our article on the evil outside chimney? And the section on outdoor air?

It sounds like you have a classic case of cold backdraft at standby complicated by some other factors. As I think you are aware, there is no sure-fire solution to the problem because it is caused by the physical relationship between the chimney and the house, which is not easily changed.

But the bottom line is that the cold backdraft can be avoided easily at the design stage, but not once the house and fireplace are built.

You could consider gutting the smoke shelf/throat damper/smoke chamber area and install a chimney top damper operated by a chain. This would reduce cold backdrafting. Or you could consider putting in a fireplace insert with a full stainless chimney liner. Neither option is a 100% certain cure, but either will usually help some. Maybe you need to keep looking for a qualified professional to help.



Outdoor Air Supply for Fireplaces

Please provide info on a fresh air damper for a masonry fireplace. Do they actually work? The idea is that they pull outside air for combustion and do not pull heated air out of the living space. The problem is that my local brick association recommends the installation of one in a new masonry fireplace although they cannot tell me where to secure one. Please inform me ASAP as I am planning a new masonry fireplace in an addition that will take place in June.

Thank You, Chris

Hi Chris,

The real question is not what your brick association contact's opinion is about outdoor air supplies, but what are the requirements in your local building code. Many jurisdictions in North America make outdoor air supplies for fireplaces mandatory and if that is the case where you are, then you have no choice but to put one in.

I should point out, however, that mandatory outdoor air rules appearing in building codes were added because it was a widely held opinion that outdoor air made sense. See the discussion on our site about outdoor air supplies.

It turns out that the best way to prevent smoke spillage from fireplaces is to give them tight fitting doors and combustion systems that will sustain flaming combustion. It is also important that the venting system be well designed and that the pressure in the house be managed within reasonable limits.

In answer to your question, no, outdoor air supplies don't work, but you may have to put one in anyway. I don't know where to get an outdoor air kit for a masonry fireplace, but I would be surprised if a local mason couldn't tell you, since if they are mandatory, the masons must be using something.

But aside from the issue of outdoor air, our advice is NOT to build a conventional masonry fireplace. You would have much better performance and much less pollution from either a masonry heater or an EPA certified factory-built fireplace.



New Smoking Fireplace

We just built a brand new home in November. Our zero clearance wood fireplace (Heatilator) upstairs burns fine if the doors to the fireplace are closed, but if we open them smoke comes out into the living room. We were told that our home is very airtight and we need to install a hole (vent) for outside air in the fireplace side wall to equalize the air pressure into the room. The fire burns very well and we have no smoke until we open the glass doors of our fireplace.

Can anyone give me any advice on this? Thank you for your time, John

Hi John,

Open fireplaces were fine for leaky old houses, but now that we demand draft-free comfort and low heating/cooling bills, houses have had to be built tighter, so open fireplaces should be relegated to history books. See the article on our site about open fireplaces.

Outdoor air for the fireplace is a widely promoted solution, but it doesn't work. See our section on outdoor air supplies.

My advice is to keep the doors closed. I'm a little surprised someone didn't warn you about this in advance.



Sharing Flues?

I have a woodstove in the basement connected to the same flue as our natural gas furnace. Recently my landlord installed an aluminum liner in the flue rendering my woodstove use inoperable.

I would like to tap into the 2nd flue of the chimney (from basement) that services the upstairs fireplace. What I need to know is if this is possible? I am guessing I would have to brick the upstairs chimney closed. It looks as though the ash vent at bottom of fireplace would provide enough draft but again, I'm not sure.   Any recommendations or direction I could find info would be helpful.

Thanks in advance. Dave

Hi Dave,

Neither flues serving gas appliances or those serving fireplaces are acceptable for venting of wood stoves. In theory you could brick up the fireplace and use the flue but that is more complicated than it seems. What you really need is to talk to an experienced dealer to inspect it and advise you.



Reading between the lines of fireplace plans

In the past I have received some valuable insight on fireplaces and the best way to build the chimney (inside!)  I hope you can help me with the rest of the much needed information I need before we begin construction.  We are planning to add a room onto our two story farmhouse with a fireplace in it.  I would like to know where I could get plans to build a energy efficient one, (size wise what are my options), possibly run a gas line to it for down the road, and how do I insulate behind it since it will be fully enclosed inside the room with vinyl siding on the outside.



There are a few things about your message that make me think you are about to make a big mistake.  If the addition to are planning will be a single storey, you could create a fireplace that cold backdrafts even if you install the chimney inside. You'll find a discussion of the issue in our chimneys section.

When you install a fireplace and its chimney inside the warm part of the house, the only insulation that is necessary is the standard wall insulation.  If you are talking about making the back of the fireplace flush with the outside wall, you are setting yourself up for a bad fireplace that backdrafts and stinks.

We don't consider the construction of an effective woodburning system a do-it-yourself job.  The only masonry device that we think is worth considering is a masonry heater, and that is certainly not a job for an amateur.

Finally, we don't support the wasting of wood in fireplaces that are designed only to be used for watching the fire.  Plus, decorative fireplaces are the ones that most often fail to work properly.  My advice is to buy an efficient factory-built fireplace or have an experienced professional build a masonry heater for you. Save yourself a lot of aggravation and do the environment a favor.



The limits of long-distance diagnostics

I'm glad to find your web-site! We are having a problem only an expert might be able to solve. We are restoring a 105-year-old house and have finished (we thought) the restoration of our 5 fireplaces. However, as soon as we started a fire in our newly restored fireplace the attic fills with smoke! We installed new flues and dampers in all the chimneys, size of liners/dampers specified by flue manufacturer, and rebuilt the firebox, smoke chambers and hearths with the assistance of a mason. Still it smokes. We also installed gas lines to each in the event we decided to burn gas or use a gas starter. Our concern is number one; the smoke from the wood-burning and two; carbon monoxide or in the case we use gas the fumes from the LP gas.

Any ideas? Any help would be most appreciated!!



You have a problem that is too complicated to diagnose this way. You need to find an experienced fireplace specialist locally to inspect the systems and give advice. Check yellow pages and building contractors for leads.

You are right to be concerned about the safety of the fireplace if you just convert it to propane. When a wood fireplace spills, it is usually just an annoying smell; when gas spills it can be deadly because it doesn't smell much and it runs unattended.



Upgrading a 1913 fireplace without ruining the look

Hi, I really enjoyed your site and your discussion of open fireplaces.  I came to your site because I would like my 1913 fireplace to stop stealing heat from my house and maybe even supply some! I love my fireplace but realize I need to do something.  You suggested doors....is that all I can do?  The fireplace is arched brick and my house is charming in its craftsman style, and I really do not want cover the arch or ruin the look with a 1970's-looking "insert."

Should I have someone make doors?  Can I have a custom designed insert that won't ruin the look?  Where should I turn?  Thanks for your help. I am at a loss and getting cold. Thanks!!! Susan


Sorry, there is no simple answer to your dilemma. You cannot get the performance you want and retain the period look of the fireplace exactly as it is. I think you will find custom doors costly, yet unsatisfactory from a heating point of view. You don't want to attempt a custom insert; that approach would undoubtedly be very expensive and unsuccessful.

Here's what I would do. Visit some wood stove stores to find a new attractive cast iron wood stove and install it on/in the hearth and connect it to a full stainless steel chimney liner running to the top of the chimney. That way you wouldn't completely destroy the look of the fireplace because the opening would not need to be covered. Note that Ben Franklin stuck stoves in front of brick fireplaces, so a hearthmount stove is not out of place in a period setting, especially if it is an ornate cast iron model.

Good luck with it.


Susan responds:

Thanks so much John! I think this is the best option I have heard so far.



See-Through Fireplace Design

I am an architect in Maryland trying to find information that will allow me to design a 48" wide x 40" high fireplace with a 45' chimney.  I need to offset the flue 2' to 3' between the first and second floor lines (12').  I will need to start with an offset, high-form damper and then construct a metal throat which will also be offset. At the second floor line, the flue will start (24" x 24" ).  I am assuming that an Exhausto fan will be needed to insure operation if the draw becomes a problem.  I would appreciate your providing me with your fax number so that I can send you a sketch of what I am proposing.  I also need contact telephone numbers (or fax, web page or e-mail addresses) for Exhausto, high-form damper companies (Donely, Vestal, etc.), and any other sources you can recommend.  The project this information is needed for is under construction, so time is of the essence. Thank you,Bruce


The fireplace design you contemplate for your client is the antithesis  of everything we at woodheat promote.  Huge conventional fireplaces are inherently wasteful and polluting of both the indoor and outdoor air, and see-through designs tend to be the worst.  Over the course of my career I have seen many of these fireplaces cause disappointment, heartbreak and lawsuits.  When I owned a fireplace shop in the 1980s we had a policy of refusing to get involved in such fireplaces, knowing they are much more trouble than they are worth.  On the other hand, we were called in several times to help resolve the problems they create.  See the article on our site about fireplace problems.

You are right that you will need an Exhausto or similar unit to make the fireplace work at all since the basic design is incompetent on its own.  But make sure there are no other spillage-susceptible combustion systems in the house, like an atmospheric gas water heater or furnace/boiler, because they will tend to backdraft when the fireplace is operating, unless you force a large volume of make-up air in from outside.

Knowing what I know, my advice to you would be to dissuade the client from this folly that so many others have fallen victim to and if they don't agree, then run from the contract. This fireplace is a statement of ego that runs hard up against the laws of physics, and even if you can make it work and escape being sued, the environment will suffer. There are alternatives that will work, but not at the huge scale you describe. We don't promote specific products, so if you are interested you need to do some searching and talk to some fireplace specialists who earn their living by advising customers and selling products.  By the way, I typed Exhausto into a search engine and immediately came up with their web site.