Wood Burning Fireplaces - Gone for Good?

C

Chuck_IHB

New member
Does anyone know the straight story on installing or using wood burning fireplaces here in Orange County? From what I have been told, you can no longer install a true wood burning fireplace (like most of us probably grew up with) in a new home or even on a remodel. Furthermore, it seems that if you are lucky enough to own a "real" fireplace efforts are underway to limit and maybe even ban the burning of wood.



It seems that there are also many different kinds of "fake" gas log fireplaces, and that some of them can actually accept wood or duraflame-type logs, even though you may not technically be supposed to burn these in them.



Any input would be appreciated!
 
Wood burning fireplace is no longer permitted in new construction in Northern Ca. In Socal most production homes are gas only fireplace with simulated logs. These type of fireplaces have no flue and spark arrestor therefore no wood burning is allowed. Older tract homes have prefab fireplaces that allow wood burning and the firebox is connected to a flue inside a chimney with a spark arrestor at the top to contain the ember from being airborne and landing on neighbors roofs. In the last 50 years fireplaces were made in a factory and shipped out to home sites.



Even the fanciest custom homes the fireboxes were made in the factory using a light weight volcanic rock/ concrete mixture using a stainless steel flue. The bricks that we see in the firebox are thin veneers glued to the inside face of the firebox chamber.



Building a fireplace from bricks is a lost art. No one can build them because lacking the knowledge of the box dimension, height to depth ratio and opening size, the necessary angle inside the smoke chamber, and most importantly the seismic resistant masonry construction. Any slight error smoke will not draw up the chimney and blow back out into the room. The flue size is also critical to compliment the size of the firebox.



A manufactured box is engineered to draw smoke up and builders simply allow the proper space for it. The glass enclosure often is a protection measure to insure smoke is not blown back into the room. Energy conservation requires a house to be well insulated but the fireplace is a the location with a huge leak of cool conditioned air. During the hot summer months pigeons like to land on the chimney because the the air blow upward and cool off their behind. They also like to leave white poop streak marks on the chimney shrouds. Some cities require that a damper be installed to shut the chamber connection to the flue or mandatory installation of glass enclosure to seal the firebox.



Many who know about fireplaces and its properties rarely settle for a factory made box and look for a vintage home where the fireplace was built a brick at a time.
 
Thanks so much BK. My wife and I recently found a house that we liked, and it was advertised as having a wood burning fireplace (one of many realtor mistakes, it turns out) but in fact during a remodel about 9 years ago the owners ripped out the "real" fireplace and replaced it with a small "crackle" fireplace. The diameter of the fireplace flue (spelling?) was only about 6 or 7 inches and it looked really corny. The funny thing is, they built a huge mantle around this tiny fake fireplace, so even more attention was drawn to it. Our vision of a home involves sitting around a roaring fire at Christmas, not hovering around a small piece of crackling metal, so we passed on the house.....
 
I agree with most of what you said, but wonder about the part about the cool air going up the chimney and the pigeons taking advantage of it.... is what I remember about convection principle does not apply here? That is, if the air inside the house is cooler than the surround air outside the house, how can the cool air rises and go up the chimney?
 
[quote author="Astute Observer" date=1250209790]I agree with most of what you said, but wonder about the part about the cool air going up the chimney and the pigeons taking advantage of it.... is what I remember about convection principle does not apply here? That is, if the air inside the house is cooler than the surround air outside the house, how can the cool air rises and go up the chimney?</blockquote>


Air conditioners tend to generate a slight positive pressure in a well insulated house. The chimney could be the path of least resistant for the cool air to escape and equalize pressure to the outside. It's not the temperature of the air that determines the flow, rather the pressure.
 
That could be a good explanation, but how can AC increase the pressure in a house? PV=nRT if I remember my high school gas law formula, and won't decrease in air temperature decrease the pressure in the house?
 
[quote author="Astute Observer" date=1250210757]That could be a good explanation, but how can AC increase the pressure in a house? PV=nRT if I remember my high school gas law formula, and won't decrease in air temperature decrease the pressure in the house?</blockquote>


You are blowing outside air into the house - thus increasing the amount of air inside the house faster than it can escape. PV = nRT applies to a closed system only.
 
[quote author="Astute Observer" date=1250213861]well-insulated means a close system (except the AC), and there is no outside air blowing into the house.</blockquote>
My wife always thought that the air intake was at the outside A/C unit which is why she doesn't want our dog near it.



I showed her the air intake vent where we put the filter and said "This is why they tend not to put these near the kitchen... because if you cook fish... the house will smell like fish".
 
[quote author="Astute Observer" date=1250213861]well-insulated means a close system (except the AC), and there is no outside air blowing into the house.</blockquote>


Only if it is perfectly insulated and the air conditioner unit is only recycling the air. Most of the time this is not the case - especially when you have central air. For central air units you can block the recirculating path by closing some doors. At that point, the chimney may be the easiest way to equalize pressure. Of course, this depends on the specific design of your air ducts/inlets/outlets.



Most people who have central air can try this and check for drafts by the chimney, indoor water heater, or wherever there is a opening to the outside as they close doors throughout the house.



Another good example of building up pressure is the incorrect use of an attic fan. If you suck out air from the attic too fast, you generate a negative pressure that will cause the cool air in the house to flow into the attic (and warm air from the outside to flow into the house).



If you have a perfectly insulated room and an AC unit that draws air only from that room and blows it right back into it, you are right. Pressure would be determined by the ideal gas equation and result in a negative pressure relative to the outside world. However, you'd probably die in that room since there would be no way to replenish the oxygen you'd be consuming. :p
 
See, if bk mentioned pressure differential, then I would have shut up a few posts ago! But as you mentioned, this depends on the design and how the duct works are done, so your explanation means that only a portion of the house have this problem with the chimney leaking cool air.



I may want to take you up on the oxygen thing since no matter how tight you insulate a house, there will always be some air exchange going on due to open/closing of door, etc.,. but that would be a bit hair splitting there.
 
[quote author="Astute Observer" date=1250222643]See, if bk mentioned pressure differential, then I would have shut up a few posts ago! But as you mentioned, this depends on the design and how the duct works are done, so your explanation means that only a portion of the house have this problem with the chimney leaking cool air.



I may want to take you up on the oxygen thing since no matter how tight you insulate a house, there will always be some air exchange going on due to open/closing of door, etc.,. but that would be a bit hair splitting there.</blockquote>


You're right, it totally depends on the house and the design of the ventilation system. Some places will not suffer from this - others will. If you light up an incense stick you can play detective and easily chase drafts by watching how the smoke flows near suspicious places (fireplace, water heater exhaust vent, bathroom vents, kitchen vent, windows, etc). This flow may change as you start closing doors one by one (while the AC is running).



One unfortunate consequence of using a way too powerful attic fan is that the resulting negative pressure can actually pull in the exhaust from an indoor water heater. Being a source of carbon monoxide this can have drastic consequences.



BTW, old school fireplaces are a major fire hazard. I'm glad they are not putting those in anymore. A gas flame is less charming, but way more predictable.
 
On a hot day where the Socal temperature is like 100 degree outside even when the hottest conditioned air leak through the fireplace and up the chimney the air may even be 85 degree exiting and that is still a 20 degree cooler breeze up the pigeon butts assuming the thermostat set at 80 degree. The AC condenser located outside has a fresh air intake valve to mix air into returned air inside the FAU unit located either in garage, attic or assigned closet inside a home.



In a static mode after a home established its 78 degree comfort zone the air is turned off. What would happen when one opens a window of door on a hot day. The hotter air from the outside has a different pressure thus move into the direction of the cooler air and pushes into the cooler air volume since the room volume is constant air needs to escape. The escaped air is resultant air mixed with hotter air and cool air inside the room. The cycle will continue until the inside and outside air reaches equilibrium.
 
[quote author="green_cactus" date=1250227522][quote author="Astute Observer" date=1250222643]See, if bk mentioned pressure differential, then I would have shut up a few posts ago! But as you mentioned, this depends on the design and how the duct works are done, so your explanation means that only a portion of the house have this problem with the chimney leaking cool air.



I may want to take you up on the oxygen thing since no matter how tight you insulate a house, there will always be some air exchange going on due to open/closing of door, etc.,. but that would be a bit hair splitting there.</blockquote>


You're right, it totally depends on the house and the design of the ventilation system. Some places will not suffer from this - others will. If you light up an incense stick you can play detective and easily chase drafts by watching how the smoke flows near suspicious places (fireplace, water heater exhaust vent, bathroom vents, kitchen vent, windows, etc). This flow may change as you start closing doors one by one (while the AC is running).



One unfortunate consequence of using a way too powerful attic fan is that the resulting negative pressure can actually pull in the exhaust from an indoor water heater. Being a source of carbon monoxide this can have drastic consequences.



BTW, old school fireplaces are a major fire hazard. I'm glad they are not putting those in anymore. A gas flame is less charming, but way more predictable.</blockquote>


Old school Fireplace is not a hazard unless the brick flue and chimney mortar begin to separate and the hot ember is trapped inside the cracks and ignite the wood framings attached to the chimney.



Earthquake is lateral forces that cause damages to uninforced masonry. Fireplaces located inside wall has the floor framing to brace the bricks and it is structurally safer but if there is a crack then it is buried. Most fire are caused by this type of set up where the ember smolders inside the framing. Chimney located on outside wall is weaker but much safer because the cracks can be seen. Outside air also lower the temperature of the hot ember. The key is reinforced masonry where steel and straps are incorporated into the construction. Very few construction trades know how to design and build it so the solution is to default to a factory made unit and install it like an appliance.



Just like any appliance the aesthetic will get dated. Kitchen is the #1 area of the house that get dated.
 
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