Adding firebricks or soapstone bricks to a zero-clearance fireplace

[dbsimpson]

Hi all.

Apologies in advance if this is already answered elsewhere. I did about a 10 minute search in the Q&A section but couldn't find anything about this.

My question was, is it okay to place additional firebricks or some soapstone inside a zero-clearance fireplace? Or will this make the fire too hot and so violate the original design intent of the whole zero-clearance specifications?

I was thinking that adding some firebricks to the inside of the firebox may soak up more heat, rather than having almost all the heat go straight up the chimney. Currently I have just the standard zero-clearance type firebox, with the metal casing and a thin liner of brick-lick ceramic for looks. If I line some parts of the box with some soapstone or firebrick perhaps some additional heat will stay in the house and radiate back slowly.

My instincts tell me that this will increase the fire temperature and therefore go against the original operating specs. Just thought I would check.

Thanks.

-DBS

 

[Rhone]

Firebrick is very different than soapstone, firebrick is designed to reflect heat and hold nothing. It's even worse than normal brick for holding heat. Its purpose is to reflect heat back into the fire to get higher temperatures so the fire burns better and also to protect usually the steel from getting too hot. It allows a very responsive fire, as it gets the heat out of it and into the living area.

Soapstone is the opposite. Instead of being a reflector it's a battery for heat (natures most heat holding and transferring solid material on the planet). You light a fire, and you have to wait for the soapstone to "charge" up before you feel heat. Likewise, if you lower the air control you have to wait for the soapstone to "discharge" its stored heat before it catches up with your lower setting. It's very different than what you're used to if you've never experienced soapstone, and rather comparitively expensive.

Either way you shouldn't mess with the design of your unit, soapstone has the properties you're looking for and I think you'll get very little of its benefits by retrofitting. Units designed around soapstone take advantage of it.

 

[wg_bent]

I had similar ideas, but more in the line of adding the soapstone in front of the fireplace or as part of the mantle. The conclusion I came to was that if I put the stone outside of the fireplace, I wasn't doing much other than delaying the heat transfer. With a fireplace, generally you want heat "now". It's kinda natural to want to improve on the design of your fireplace. Kind of like putting a better air filter on your car for improved performance. But I really don't think that fireplaces can be helped. Most 0 clearance fireplaces are actually designed to get rid of most of the heat and prevent you from burning down your house. They all seem to do that quite well. Some with fans can heat a room o.k., but they probably cool off the rest of the house.

Here's a little thing I did one day. While the fireplace (pre-wood stove) was burning, I was up on the roof. I held my hand over the flue pipe to see how hot the air was. Surprisingly, it wasn't too hot, but the huge volume of air coming out of the 11" pipe was really surprising. That means that the hot fire air was mixing with a lot of cold air from somewhere. Well, the only source of that air was the inside of my house.

The bottom line: If you want to improve on the efficiency, you really need a different heating appliance. I'm working on that right now. Read my "Before the Osburn" thread in the Pictures forum. My goal there is to show the installation in sort of large steps with some pictures. I wish I had seen some before I did my install.

 

[dbsimpson]

Thanks for the replies guys. That's pretty much what I figured.

Nice to see the steps of your install as well, Warren. I almost went through the same thing but had so many building code questions that I decided to check with our city engineers first (and actually got responses!). I have a wood-burning fireplace on my ground floor which would perfectly fit a Regency 'Hearth Heater' model, which comes out on to the floor a bit more. It would run about $2500 installed not including the extra finishing I would have to do, so I'm kind of on the fence, especially when it comes to cleaning later.

One question I have, what is the grey wall material you have installed up on the wall there? And, is there still combustible material in behind it?

-DBS

 

[wg_bent]

The grey material is called Durrock. or better known as cement board. It's a cement product you can get at the BORG, and has a fiberglass mesh that is also non-combustable (even tried just to be sure). There is a stud wall directly behind it. What isn't there yet is a second layer of the cement board that will have an air gap created using non-combustable spacers (small peices of the cement board), then the surface will be tiled. Outside of the tile there will be a federal style mantle. Code and clearances are being followed here. The biggest reason I tore the previous hearth off was that is didn't meet the clearance nor the non-combustable limits. (It was also seriously ugly)