Spanish Chimneys

 

Hi John,

We have recently moved into the valley to get away from the cold English climate, we have no heating except for a log burning fire. Before moving in we romantically envisaged sitting in front of the fire, being gently roasted, trying to make pictures and objects out of the flickering flames as the logs burn.  The reality is that every time we light our fire we are smoked out; we are bloody cold and have resorted to using several electric oil filled radiators just to keep warm.


Any suggestions would be appreciated.


Regards Janet


Hi Janet,

As you have quickly realised Spain is a cold Country which has the sun and winter evenings can be very chilly. You are not alone in suffering from smoke filled rooms when burning an open fire, many villas both new and old have the same problem. Chimney and open fireplace construction is a skill which has eluded many constructors, leaving homeowners with fireplaces which are totally useless, except maybe for a flower arrangement or candles. There are many factors which will determine how well a log fire will burn and these factors listed below are all designed to achieve one basic function, which is to remove the products of combustion (smoke etc.) from the fire as quickly as possible.

1. The fireplace opening must be in the correct proportion to the cross sectional area of the chimney.
2. Above and behind the mantelpiece there should be a “throat” or narrow slot of the correct size to create a draw on the chimney, this throat is usually constructed of angled gather plates.
3. The height of the chimney is very important; flues of over 4mts. in height will create a better draw than a smaller one.
4. The top of the chimney is also important; traditionally Spanish constructors tile the top of their chimneys forming vent holes below. These vent holes are often too large or too small, allowing either water into the chimney or restricting smoke out of the chimney.
5. One of the most common failures in Spanish chimney construction is the flue itself. If the inside of the chimney is rough with poor brickwork or filled with debris you will have problems. Generally the smoother the flue the less resistance there will be for the smoke to reach the top, the longer this takes the greater the chance that the smoke will cool and start to go back down the chimney and smoke fill the room.
6. Another factor that is often given little consideration is the location of the property, is the house situated in a valley or surrounded by many trees.

If you have problems with any of the above the following remedies may be of interest.

1. If the fireplace opening is too large, as is common, the grate can be raised on bricks or a steel plate inserted in the top of the opening to reduce the size of the aperture. This is enough in many cases to stop serious amounts of smoke from entering the room.
2. If the opening is large and the chimney wide and open, a throat and gather plate should be installed at the correct angles to create a “draw” venturi in the lower section of the chimney.
3. If there is very little draw then the chimney height may need to be increased. High chimneys over 8-10mts. can have overdraw problems and chimneys in excess of 12mts may return to a slow draw situation as a result of cool and slow moving products of combustion at the top. Consideration should also be given to where the chimney terminates above the roof line. In general terms it is usually better if the chimney terminates a minimum of 60cm. above the highest part of the roof.
4. Chimney terminations can usually be resolved by opening or closing vent holes, ensuring a through draught is always maintained.
5. If you have a chimney that is poorly constructed, choked with debris or takes a convoluted route through walls and ceilings then reconstruction may be the only option. The installation of a flexi liner, which will give a smooth flow for gases is preferred, this liner should always extend from the mantelpiece to the top of the chimney.
6. If your house is located in a narrow valley, on the side of a steep hill, surrounded by high trees or in areas where cold air accumulates, draw may be affected. Draw can also be noticeably affected by adverse atmospheric conditions and unfortunately little can be done to resolve these factors, except perhaps moving house!
7. Finally it is conceivable that you may not be able to completely resolve a smoking fireplace / chimney and that the installation of a wood burning stove and lined flue may be the only solution.
 
The problems you are encountering will be as a direct result of one or more of the above mentioned faults, my advice would be to contact Meridian Stoves on 966480905 (they are located at the side of the petrol station in Jalon) they have been installing gas and wood burning fires for the last 9 years and in this time have also rectified many problem fires and chimneys.  Finally when you appear to have all the factors for a good wood burning fire in your favour, make sure you have the chimney swept every 2-3 years, as this will reduce the risk of chimney fires and also help to keep the fire working efficiently.

John Phillips (F.I.A.S. F.A.B.E. M.I.B.C.O. F.F.B. M.R.S.H. C.M.W.O.B.O. M.B.I.M)
Construction Buena Vista

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