Chimneys are still a very common sight in our neighbourhoods, and yet very few of them are actually used anymore. If your house has an old unused chimney, does it still need to be ventilated?
It’s important for an unused chimney to still be ventilated either at the top or bottom. Venting the chimney assists the airflow in keeping the chimney dry, preventing condensation from forming inside of it. Without this critical airflow, the condensation could freeze and cause the stack to collapse.
Regulations typically do state that any unused chimney must be ventilated to prevent this from happening. So, from both a safety and a legal standpoint, all chimneys should be ventilated regardless of their state of use. Read on for further guidance.
What is the purpose of a chimney vent?
Safety should always be your first concern with the structural aspects of your home or any building you own. This is the main reason, broadly speaking, why ventilation is important for an unused chimney. Chimney stacks are naturally much less stable than the rest of the building. So, they are prone to structural damage over time which could cause them to fall in the worst case.
The main issue with an unventilated blocked chimney is that, even if it’s not being used, rainwater can still enter through the brickwork. With no airflow, that water will turn to condensation, and in the right conditions could freeze inside your chimney. This can cause it to become damaged and, as we already mentioned, even collapse. On top of that, unchecked moisture seeping into your walls from outside will eventually cause dampness. Proper ventilation of a chimney prevents this from happening.
How do you ventilate a chimney flue?
When ventilating an unused chimney, the important thing is that there is airflow at only one end. Common practice is to completely seal off the airflow from inside your home, where the chimney meets the floor. Then seal off the chimney at the top with a ventilated metal sheet. This is often a task that is simpler than most people think. If you have an unused chimney or unwanted fireplace covering it up is a perfectly viable option. As long as you are sure to keep the chimney itself ventilated.
For ventilating at the roof, we recommend a supply and fit service, rather than DIY. For chimney flutes, common practice is to have a cap fitted. Whether your chimney can be capped or not, it’s best to have the job done by a professional. We will look at the cost of that shortly.
The cap should prevent rain from coming in without creating an airtight seal, allowing airflow to continue and preventing the build-up of condensation. You can also ventilate the chimney at the bottom and seal it at the top. But this can create greater heat loss than sealing it at the bottom.
Does an unused chimney need ventilation?
It’s better to ventilate an unused chimney, rather than blocking it entirely.
Completely blocking the unused chimney might seem like a good idea and the simplest solution, but it comes with a lot of potential problems. Some would say that the answer is based much more on the individual building, and that particular factors should be taken into account. For example, a house in an area with very low rainfall is at a lower risk of the kinds of condensation damage we’ve discussed.
But there’s really no reason to gamble with it like this. Though it may take longer, the moisture will still gather in there. It always has the potential to cause damage if the chimney is completely blocked with no airflow to keep it dry.
Before you close off and ventilate your chimney, make sure you give it a good clean on the inside. To do this, you might like to grab a hazmat suit to protect your close from chimney grime. It’s also recommended to wear an FFP2 Mask and safety goggles whilst cleaning your chimney out.
Should you block up an unused chimney?
Capping is another important part of dealing with an unused chimney. This is probably the best and most efficient protection for your chimney in three important ways.
The first, as mentioned, is moisture. A cap on the top of your chimney keeps water out and air in. They are not sealed airtight so even when your chimney is capped air can still come in.
The second is thermal insulation. An uncapped chimney allows a lot of heat to escape from your house. So, capping it retains the heat while also preventing dampness and condensation.
Finally, capping the chimney will prevent animals from getting in. A bird getting stuck in your chimney is not something anyone wants to have to deal with.
So, capping the chimney at the top and sealing it at the bottom is one of the best ways to prevent numerous problems.
How much does it cost to add a vent?
The average lower-end cost of a basic chimney cap, for a supply and fit service, will be somewhere between $250 and $350. This cost can rise considerable depending on the chimney and the complexity of the task. The cost does vary depending on the home as well. If there is more than one flute to be capped, the cost will change again. The same as if there is more than one exit that needs to be ventilated, again this will affect the cost. Also, you need to consider how accessible your chimney is. If getting to your roof isn’t very easy, scaffolding might be necessary. This can be an extra cost for the process, but vital for rooftop work safety.
But there are many other things to remember before dreading the cost of ventilating our unused chimney. The money that will be lost with the heat during colder months will quickly add up to more than the cost of ventilation. In the long run, ventilation will save you money.
Also, the potential for serious structural damage will be very high and a very real possibility without this ventilation. Having to repair this damage will be considerably more than ventilating and capping the chimney properly in the first place. The cost of not ventilating your unused chimney always has the chance to be far higher than a one-off cost to get the job done right.
The cost of not ventilating your chimney has the potential to be very high. Especially compared to the one-off cost of getting the job done right at the beginning. Not to mention that, once you have fixed structural damage, you would still then need to have it capped or ventilated properly.
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