Share How to Block Chimney Draughts
If you live in an older house it's likely that it will have at least one fireplace and chimney. Often such chimneys are fully disused and open fireplaces are permanently blocked. However, if you are a lover of a roaring fire in the winter months, you will be using and actively maintaining your fireplace. But if you have open fireplaces in your home that you only occasionally use, or don't use at all, during colder times of the year they can cause significant draught problems.
Article Topics:
- Understanding the Problem
- Ways to Temporarily Draught Proof a Chimney
- Hearth Cover
- Inflatable Flue Blocker
- Felted Wool Flue Blocker
- Ways to Permanently Draught Proof a Chimney
- Chimney Cap
- Decommissioning
In this article we'll talk about open fireplaces and look at ways you can prevent heat loss caused by chimney draughts negatively impacting comfort and home heating energy efficiency.
A quick note: if you have a draught coming through a window or front door, these guides will show you ways to fix them.
Your DIY Guide to Draught Proofing Windows
Expert DIY Tips for a Draught Proof Front Door
Ok, we’ll begin by taking a closer look at unused fireplaces and the benefits that blocking chimney draughts can bring.
Understanding the Problem
Before delving into the solutions to draught proof your chimney, let’s quickly look at why disused open fireplaces can be problematic.
The chimney acts as a direct pathway for cold air to infiltrate your home and for warm air to escape. Open chimneys can be like open windows in terms of heat loss, in the colder months of the year presenting a real problem with draughts, lowering indoor temperatures.
As much as 5% of your home’s heat will be lost because of open fireplace draughts.
As one of the biggest causes of a draughty home, it can make sense to block a chimney opening, especially for larger unused fireplaces. Fixing a draughty chimney not only makes your home more comfortable, it helps to lower energy costs too.
Ways Temporarily Draught Proof a Chimney
A blocked chimney flue will of course significantly reduce, or completely stop, chimney draughts. But what are the best ways to go about doing it? Let's look at some common flue sealers and how to fit them, starting with simply covering your fireplace hearth.
Hearth Cover
Hearth covers are designed to seal off the fireplace opening when the fire is not in use. They're available in a variety of styles and materials, making it easy to find one that matches your fireplace and room décor.
A magnetic hearth cover uses magnets to attach to the fireplace opening, providing a secure seal. They are simple to use and remove when you want to use the fireplace.
Installing glass or metal doors on the fireplace hearth can create an airtight seal too for when the fireplace is not in use. But this could be quite costly. A less expensive solution (although perhaps not as aesthetically pleasing) is a inflatable flue blocker.
Image Credit: Chimney Balloon
Inflatable Flue Blocker
An inflatable flue blocker, chimney pillow or chimney balloon is exactly what its name suggests. It’s an inflatable bag that is filled with air to fit snuggly in the chimney space to prevent draughts. Inflatable flue blockers are a relatively low cost chimney draught solution and come in a variety of sizes to suit a majority of home fireplaces for airtight sealing.
If you don't want a totally airtight seal, inflatable flue blockers can vary the amount of air you want to flow by the amount they are inflated. This may be if you have concerns about a complete lack of airflow exacerbating damp or condensation issues in the room.
Inflatable Flue Blocker Considerations
While inflatable flue blockers are often very effective, there may be some drawbacks. The obvious one is that they're inflatable, so can become punctured. And they are sometimes tricky to fit, to make and maintain an airtight seal.
For example, if the outside temperature drops very low, inflatable flue blockers can shrink as the air inside them contracts, and also air will need to be topped up periodically, usually once every few months, to keep draughts at bay.
A common alternative to the inflatable flue blocker is a thick, fabric mat, typically made of felted wool.
Image Credit: Chimney Sheep
Felted Wool Flue Blocker
This type of chimney draught excluder, known as a chimney sheep, works on the same principle as the inflatable draught blocker, in the sense that it fits in the chimney flue to prevent cold air coming in and warm air escaping.
Made mainly from felted wool, this kind of thick mat chimney blocker stops draughts while allowing the room to breathe as the fabric does not make an air tight seal. But the amount of air flow will be very small, similar to an air brick, window trickle air vent, or other managed air flow system in your home, so you won't feel it.
They come in different shapes and sizes to suit almost any fireplace.
Felted Wool Flue Blocker Considerations
With this style of chimney draught excluder, it's important to get your measurements right so that it stays firmly in place in the chimney. Simply measure the width and length of the lower part of the chimney flue where the blocker will go and get the appropriate blocker size and shape.
A Word of Caution
If you use a temporary flue draught excluder, use a reminder that your chimney is blocked. Some chimney blockers are supplied with a reminder tag. This will help prevent accidently lighting a fire while the chimney is blocked. Remember, it might not be you lighting the fire.
Ways to Permanently Draught Proof a Chimney
The chimney draught solutions we've talked about so far are temporary. They can work very well if you don't use your open fireplace and want to prevent draughts just during the colder months of the year.
For a permanent solution to chimney draughts, consider either a chimney cap or going the whole hog and completely decommission your fireplace. Let's look at the cap.
Chimney Cap
A cap is a simple device that blocks your chimney at the top rather than through the fireplace to prevent air leaks. They are a plastic or metal covers that go over the chimney pot to seal it, capping it off more permanently than hearth covers, inflatable and felted wool flue blockers.
If you prefer the idea of a more permanent draught solution, choose a chimney cap that can allow trickle ventilation if you want to help prevent damp and condensation in a room.
Always follow manufacturer instructions when using chimney draught proofing products.
Decommissioning
If you don't use your open fireplace and don't ever plan to, it can make sense to choose to decommission it. To permanently seal your fireplace and chimney up with brickwork will solve any draught issues once and for all.
Depending on the size and style of your fireplace, you may have the option to remodel the space, for example as bookshelves or for ornamental purposes.
The downside of taking the decommissioning approach is the that it's not really a DIY job and you will likely need to hire a tradesperson. This will raise the cost significantly compared to the other draught proofing methods discussed in this article.
Weigh the pros and cons of repurposing your fireplace space to see if it's the right solution for your home.
Final Thoughts
Blocking a chimney during colder times of the year can significantly reduce draughts and lower home heating costs, whether you choose temporary solutions such as chimney balloon or chimney sheep-types, or you decide to permanently block your chimney flue with a chimney cap, or brick it up. And don't forget to install draught protection on your interior and exterior doors.
Hopefully this article will have inspired you to take on the draughts in your home. If so, discover more about how to fix draughts in How to Draught Proof your Home.
For more DIY inspiration, visit Hiatt Hardware and browse a broad range of how-to guides, related articles and insights.
