Fireplace and chimney

Fireplaces are a popular feature of Spanish villas. They can be a focal point within the house, add a certain degree of style, as well as being an economic way to heat the house in the colder months, especially if you have access to cheap wood.

In contrast to British fireplces, which tend to have a relatively small inside footprint area, and have a grate and ashpan, most Spanish fireplaces are much larger in terms of area, and the fire is often made directly on the stone floor, with grates and ashpans being optional.

The larger area may have to do with the British preference for coal versus the Spanish preference for firewood. But what about the grate and ashpan? Is this just a cultural thing or are there other reasons they aren't so popular here?

Also, what about smoke? I have lived in several houses in Britain with open fireplaces and don't recall smke in the living room ever having been a problem. My Spanish chimney has a very good draught. I notice for examle that its much easier to start a fire than in the fireplaces I used to have. I'm using much less tinder and kindling and the fire gets hot much more quickly. The problem though is that when the fire burns down, and the cinders start to smoulder, that smoke drifts into the room. Maybe this is due to a combination of a hot chimney flue and a no longer as hot firebed. Does anybody else have this problem? Any ideas?

Normally a hot flu helps the fire draw, it's when the flue or chimney starts to cook that the problems start. depending n what type of chimney you have fitting an aspirator (spinning top) can help as it creates its own draught as it spins..

QUOTE from internet;- 

Cowls for “downdraught” problems

The problems of “downdraught” or cold air comming down the chimney are not uncommon. The reasons for downdraught are also not well understood by many as there are often multiple factors involved. Solving the problem requires some investigation and questioning regarding each individual case. Some of the factors are: Chimney height, terminal position, terminal design, building architecture, proximity to other structure including trees & hedges, chimney temperature, internal building layout, forced air extraction etc. etc. It can get complicated so you need someone who understands all this to advise you. It is unlikely that fitting a cowl will increase the draught of a chimney, indeed the added restriction will most likely reduce the up-draught further. Fitting a rotary type cowl can solve the problem but only if the problem occurs when it is windy. The best solutions for inadequate draught are relining with an appropriate sized liner for the appliance, increasing the chimney length or installing a chimney fan (last resort).

One of the main causes of smoke failing to rise in masonry chimneys is cold sink. If the chimney is built on the outside of the house rather than incorporated into the walls, the masonry cools quite quickly when the fire dies down causing the cold air to sink, which also brings the stack smoke down with it into the room. This is worse on cold, windy and/or rainy days.

The only economical solution is to close the fireplace by adding fire doors – that is why log burners are so popular. Log burners can also suffer from a similar problem in certain conditions when fitted with a spinning cowl. The metal flue cools rapidly and condensation forms in the pipe-work which can quickly form a solid blockage, especially when the fire is on tick-over or cooling. The condition can be alleviated by fitting a directional cowl which is operated by the wind and will never face into the wind to cause downdraft and fast cooling. It is always a plan to fit a TEE piece into the flue (instead of a 90deg bend) with a removable cap at the bottom so that any build-up can easily be removed before it causes problems and of course prevents the need to deconstruct the flue to clean it.

It is interesting that the traditional Spanish method is to run the flue pipe inside the room as high as possible before punching through the wall as the heated flue also acts as a heating unit. Brits tend to go for ‘the tidy look’ and exit the flue immediately behind the burner smoke outlet which just heats the air outside and gives a larger area of metal to cool quickly.

Thanks for all your replies.

My fireplace is open and I don't have any doors to close. The chimney is inside the house, but backs onto an outside wall so cooling of the chimney could be a problem. This wall is part of the old core of the house, made of local rocks rather than bricks, and at least 40cm thick (the house was a circa 100 year old ruin restored by a previous owner, and its not entirely clear which bits are original and which aren't). This probably means the wall takes longer to acquire heat than a modern brickwork equivalent but should also be slower to cool. The chimney has a roof on it and it would be difficult to fit a cowl or fan without doing major changes to the masonry. Looking up the chimney flue with a torch it appears to be brick for the first metre above the opening and then a metal tube beyond that. The chimney is straight and I can see the daylight coming in at the top. The chimney appears to be fairly clean on the inside. 

One solution a neighbour suggested would be to not let the cinders smoulder but to transfer them to a metal bucket (with lid) using a shovel as soon as the smoking starts, and then put the bucket outside to cool.