Fireplace Questions

[Randy Klein]

I have a few questions regarding the fireplace in my house and wanted to see what everyone thought.

It's a standard fireplace, uses room air for combustion, has a metal screen and glass doors.

Questions:
1. I've heard that a fireplace actually makes your house colder by sending your already heated room air out the chimney and cannot provide enough heat to counter that. So while the space in front of the fireplace is warmer, the rest of the house is colder. Is this true?

2. When using the fireplace, should I keep the glass doors open or shut? Even when shut, there seems to be air slots at the bottom so air can still get in. With the glass doors open, the metal screens are still shut to prevent embers from jumping out.

3. I burn alot of my hardwood scraps that can't seem to find another life as pen blanks (can you get smaller than that) or other uses. And I know you shouldn't burn MDF or plywood, but is kiln-dried SYP and/or SPF (2x material) fine to burn? Or does that lead to too much creosete buildup?

[randall rosenthal]

at one time here the only heat houses here had were fireplaces. it is a matter of efficiency. a fireplace will heat your room and eventually any enclosed space....however unevenly. it just takes a very long time to overcome its innate bad design. the hotter the fire the more heat and a roaring fire will heat an interior space......but will consume much more fuel than a good air tight stove....which is how i heat my home and shop. a fireplace is nice to have and will add heat but isnt a good choice for primary heating. real nice to sit in front on a cold night with a good drink.

[Jim O'Dell]

I think the pellet stoves would be a little more efficient. Probably safer in a shop setting also They do make them as inserts for regular fireplaces. But I'd bet the free standing ones would allow more heat to stay in the room. If you have central air, proper location of the stove and an intake vent would help move the heat around the house. Just have the fan on. Jim.

[Sonny Edmonds]

Questions:
1. I've heard that a fireplace actually makes your house colder by sending your already heated room air out the chimney and cannot provide enough heat to counter that. So while the space in front of the fireplace is warmer, the rest of the house is colder. Is this true?

That depends on several things. First, a "fireplace" does need air for combustion and venting the smoke out. And it will draw that from the house anyway it can, Ie: leakage around doors, through receptacles or switches, any air leaks that can let air in. (You'll feel drafts of cold air coming it these places).
You CAN negate that by making a fresh air inlet as near the fireplace as possible. That way the combustion air comes in very near where it is going out. Not from the other end of the house.

2. When using the fireplace, should I keep the glass doors open or shut? Even when shut, there seems to be air slots at the bottom so air can still get in. With the glass doors open, the metal screens are still shut to prevent embers from jumping out.

You want something to keep the embers from coming out into the room when the wood pops or crackles.
But the fire must have air intake to allow it to vent outside. Even "air tight" inserts or stoves have some air being let in, or the fire would snuff itself out.
And you would do well to install, or have installed an air tight insert if you are interested in using the fireplace for heating. You can always open it up for the aesthetics of an open fire (with or without a hot toddy or cider, glass of wine, fun on the bear skin rug, ...:D

3. I burn alot of my hardwood scraps that can't seem to find another life as pen blanks (can you get smaller than that) or other uses. And I know you shouldn't burn MDF or plywood, but is kiln-dried SYP and/or SPF (2x material) fine to burn? Or does that lead to too much creosote buildup?

I'm not sure what SYP or SPF is. SPF to me is Sun Protection Factor of sunscreen we slather on the kids when boating. :)
I used to burn anything that would burn. If you have more good wood to burn (Oak or hardwoods) than poop wood, you will keep your build up to a minimum.

All of this is based on most of my adult life using wood of some sort as a source of heat. Now that I am maturing like fine vinegar, I just have the wife pay the Gas Company, or electric company, depending on what season it is. (My back does not like me chopping or hauling firwood around) :rolleyes:

[Frank Hagan]

You might check the outside of the chimney, at the base. A lot of fireplaces have an opening that is about 4" square, intended for outside air for combustion. Using that, and good glass fireplace doors (with louvers that shut), will still heat your home without sending most of it up the chimney.

SYP (southern yellow pine) is fine, I think. I'm certainly no expert, but I've heard that most of the lumber we'd use for woodworking can be burned. Really resinous woods should be avoided. And you never burn any pressure treated, glue laminate beams or plywood (or, especially, OSB) in a domestic fireplace.

[Randy Cohen]

Fireplaces are less likely to form a lot of creosote since they are always burning hot, unlike an airtight woodstove which can burn slowly and therefore less hot giving the smoke more of a chance to condense on the walls of the flue/chimney. I think burning southern yellow pine or spruce/pine/fir is fine but they burn much faster than hardwoods. You will end up feeding the fire a lot more.

[Ross Ellis]

Burning any soft wood results in more creosote. Most people around me burn hardwood only. If you do burn softwood, check your chimney frequently for build up.

[Randy Klein]

You might check the outside of the chimney, at the base. A lot of fireplaces have an opening that is about 4" square, intended for outside air for combustion.

My chimney is not against an exterior wall, so there is no such opening. It's rather annoying that way.

[Matt Ocel]

Randy -
I believe that when it is said that " fireplaces actually makes your house colder" is when the fireplace is not in use.

and

The reason the rest of your house gets colder is because the fireplace typically tells tricks the thermostat not to turn on the furnace.

Set your thermostat so the fan is running continuosly when the firepalce is on to distribute the warm air throughout your home.

[Pat Germain]

I think Sonny has it right. A traditional fireplace could make a room colder. It did so by pushing hot air up through the chimney and sucking in room air to replace it. Thus, the fireplace would provide some ambient heat, but it was pulling cold air into the house and pushing it out the chimney.

This is why Franklin invented his stove. Since the combustion chamber is inside the room, you get much more radiant heat.

I experienced the room getting colder when I lived in an old farmhouse in Oklahoma. A wood stove was the only source of heat in the house. I would get a fire going and leave the stove door open thinking it would provide more air and make the fire burn hotter. It actually just sucked cold air into the house. Then my dad showed me that by closing up the stove, it would draw air from outside and really heat up the room.

I think Randy would be much better off getting glass doors for his fireplace. He could get the fire going, then close the glass doors. This would prevent most of the air from being sucked in from the room. As the bricks in the fireplace heat up, they will provide radiant heat for the room.

[Randy Klein]

Well, I ran a fire for most of this weekend with the glass doors open, but the metal screen still closed of course. It seemed to raise the house by 2 degrees. The thermostat normally reads 68, but was reading a constant 70 when the fireplace was burning. The thermostat is not located in line-of-sight of the fireplace (nor in the same room) but is located under the main return vent.

So whatever it was sending up the chimney it was replacing and then some.

This next weekend I'll run the fireplace with the glass doors shut and see what happens.

[Matt Ocel]

Well now -
You guys got me thinkin (and it hurts a little) I usually have a fire and leave the door open. Although it keeps the main level of my home quite toasty, will I notice a difference when I burn with the door closed. As the lower level does cool off.

I'm going to start a fire now and check it out.

My fireplace is an Acucraft, plate steel with a sealed door.
I do have a 4" combustion air to the firebox and a 6" fresh air intake to the furnace, along with a HRV.

I'll let you know the results.

[Matt Ocel]

No noticable difference.