Open Fireplace Question

[sbest1973]

Hi Guys,

First time poster here so please forgive me if I have posted this in the wrong section!

We are about to insert a slow combustion wood heater into our open fireplace. We have pretty much picked the model we want however I seem to be getting some inconsistent advice on fluing. One person has said as long as the chimney is in good condition there is no need to put in a flu.

Another guy (from a shop) said if we don't put in a flu then we will lose a lot of heat up the chimney. This doesn't sound right to me. A little bit of heat will obviously escape from the round hole on top of the unit, but would a flu really make it more effective then not having a flu and just making use of the chimney?

Obviously installation will be easier without a flu and will also be a lot cheaper.

Any advice would be greatly appreciated.

Thanks.

[blockhed]

hello sbest1973
and welcome to the forum.
looking up the chimney in my lounge room, the gap would be too big for any combustion heater. a lot of the heat would escape as opposed to using a much smaller copper flue. have a look to the left column under "renovation forum" and put your post in there.
i think you would get heaps of comments there.
regards
the block

[LanceC]

Hi Sbest,

Having recently gone through installing a fireplace, and talking/researching with a lot of people, my understanding is as follows.

An important function of the flue is the (relatively) high rate of air travel. You want fast moving air to ensure that all particles are lifted up and out fo the chimney. Now if you have a small opening at the top of your firebox, into a large volume chimney with a small opening at the top, you can see that the air in the large space is going to be moving very slowly, and not really able to support carrying particles in the updraft. This is also one of the reasons that you use a double/tripple skinned flu when on the outside of a house, so as to keep the heat in the air, maintaining the upgraft.

I hope that helps.