What Is an External Air Kit for a Wood-Burning Stove?
If you’re shopping around for a wood-burning stove for your home, then you may have come across the term ‘external air kit’. If you’re not sure what an external air kit is, and whether you need one, then keep reading to find out.
What is an external air kit?
So, what is an external air kit (also known as a direct air kit or external air ventilation kit)?
The most commonly accepted definition is a component which allows a wood-burning stove to draw air from outside the room in which it is located.
Stoves, like other appliances that burn fuels to generate heat, require a continual source of oxygen in order to start and sustain combustion.
Wood-burning stoves typically obtain this oxygen from the room in which they are located. They will draw air into their firebox using a series of air vents. These air vents can normally be modulated (e.g., opened or closed to a greater or lesser extent), in order to control how fiercely the fire burns inside the stove.
So, close the vents slightly to dampen the fire and calm it down. Open the vents to make the fire burn more fiercely.
However, it’s not always practical, suitable, or safe for wood-burning stoves to draw the oxygen they need from the room in which they are situated.
Enter external air kits.
How does an external air kit work?
Before we dive into the details of external air kits, we want to raise a very important point.
Only certain wood-burning stoves are compatible with external air kits. These stoves will typically be listed as being ‘external or direct air compatible’. They are alternatively described as ‘room sealed stoves’.
In other words, if you want to use an external air kit, you’ll need to buy a compatible stove.
Okay, with that out of the way, let’s take a closer look at how external air kits work.
How external air kits are installed
External air kits normally consist of either a solid or flexible tube. This is the tube which connects to a spigot on the rear or underneath of the stove, and then passes through an external wall of your home.
How this tube connects to your stove varies depending on the kit you buy. Some kits will have special connectors, whilst others will simply use a Jubilee clip.
The other end of the tube (the end which emerges from the external wall of your home), is usually capped with a grill to prevent detritus or small animals from getting into the vent.
Partial sealed vs total sealed vs leak sealed
There is an important point to note when it comes to the installation of an external air kit; you can install an air kit in a partial sealed, total sealed, or leak-sealed configuration.
In a partial sealed configuration, the external air kit will provide most, but not all, of the required air for the stove. The remaining air will be drawn from the room in which the stove is located.
A partial sealed configuration is fine for homes which have a bit of existing ventilation, but not enough to run the stove completely. This typically covers homes built prior to the early 2000s, when air permeability criteria were added to the Building Regulations.
In a total sealed configuration, the external air kit will provide all the air required for the operation of the stove.
A total sealed configuration is ideal for much newer homes which have low levels of air permeability.
In a leak sealed configuration, the external air kit will provide all the required air for the stove.
This type of external air kit installation is often only used in PassivHaus homes, where the home is airtight and not able to provide a supply of air from within the room in which the stove is located.
Note - always follow the manufacturer’s instructions when installing an external air kit and wood-burning stove.
When do you need an external air kit for a wood-burning stove?
Does every wood-burning stove require an external air kit? No.
The main reason most people need to use an external air kit with their wood-burning stove is when the room in which their stove is located has insufficient ventilation.
The types of scenarios in which an external air kit is required include:
- The room in which you are placing the stove does not have a non-closable vent.
- You live in a home which has been designed and built to PassivHaus standards.
- You live in a home which uses Mechanical Ventilation Heat Recovery (MVHR) technology.
Below, you’ll find more information on each of these scenarios.
You don’t have a non-closable vent in the room you are placing the stove
Today’s new build homes are required to be more energy efficient than ever before. However, that energy efficiency is usually achieved at the expense of the air permeability of a building.
In other words, buildings are becoming increasingly airtight - with many house builders no longer including non-closable vents within the fabric of the building.
Whilst this is great for keeping warmth trapped within the walls of your home, it does make installing a wood-burning stove more challenging.
The Building Regulations stipulate that solid-fuel burning appliances (like log burners), require the installation of a ‘non-closable vent in an external wall’.
The traditional solution was to install an air vent into one wall of the room in which your stove is located.
However, there’s no getting around the fact that this leaves an open hole in the wall of the room. That’s not an appealing prospect for many homeowners.
So, what’s the solution? To use an external air kit.
You live in a home which has been built to PassivHaus standards
An increasing number of people are choosing to build their homes to PassivHaus standards.
As we wrote earlier this year, PassivHaus is a set of standards designed to create radically energy efficient homes. The flow of heat, in, out, and around the home is strictly regulated, creating a nearly airtight home.
If you’re intending to install a wood-burning stove in a PassivHaus, this is entirely possible, but you’ll definitely need to use an external air kit.
As we mentioned above, this air kit will need to be installed in a ‘leak sealed’ configuration so that your stove is completely sealed from the room in which it is located.
To achieve the best result, we recommend looking for wood-burning stoves which have been DIBt tested. This is a test which assesses the effectiveness of a wood-burner's room seal - particularly the air tightness of the stove’s door.
Buying a stove which has been tested to the DIBt standard will ensure your stove truly is ‘room sealed’ and thus suitable for use in a PassivHaus.
Guide - for more information about installing wood-burning stoves in airtight homes, read our complete guide.
You live in a home which uses Mechanical Ventilation Heat Recovery (MVHR)
MVHR is a technology which, as the name suggests, involves mechanically blowing air through your property via heat exchangers.
This has the benefit of pulling fresh air into your home, whilst retaining the heat that’s already been used to heat your home - thus reducing your overall heating bills.
However, as you can imagine, the act of mechanically pushing air around your home can have a negative impact on the internal air pressure.
Air pressure is crucially important to the proper functioning of a wood-burning stove. Disturbing this air pressure can make a stove difficult, even impossible, to light and keep burning efficiently.
As such, if you’re intending to install a log burner in a home which uses MVHR, you’ll need to use an external air kit. This will prevent your stove from being affected by changes in air pressure within your home.
In a home with MVHR, it is recommended that you install an external air kit in a leak sealed configuration.
Note - if you are intending to install a stove in a PassivHaus or home with MVHR, the installation is subject to strict criteria. If you are not sure if your proposed set-up will be compliant with these criteria, please contact your local building control department first!
The best external air compatible stoves UK
If you’re looking for an external air compatible stove for your home, then take a look at our selection of the very best external air compatible stoves below.
Woolly Mammoth 5 Widescreen Wood Burning/Multifuel EcoDesign Stove
Are you looking for a larger-than-average, impactful, classic wood-burning stove? Then consider the Woolly Mammoth 5.
Thanks to its generous proportions and large, widescreen viewing window, this stove will capture and hold your attention.
Thanks to its 5kW heat output, it will provide more than enough heat to keep medium to large-sized rooms warm on even the crispest of autumn or winter mornings.
As this is an EcoDesign stove, it’s incredibly efficient and clean burning, reducing the production of combustibles and particulate matter. With a 75.6% efficient rating, the Woolly Mammoth 5 will go a long way to reducing your firewood bills!
What’s more, this stove is DEFRA-approved, meaning it can be used in smoke control areas such as many towns and cities.
As an added aesthetic touch, the Woolly Mammoth 5 is available with different door finish options including cream, red, or grey, so it’s easy to add a splash of colour to your fireplace!
Woodford Turing Wood Burning/Multifuel EcoDesign Stove
Bold. Simple. Elegant. These words perfectly sum up the Woodford Turing stove.
Featuring sleek, clean lines, this is a timeless-looking stove that’ll fit in traditional and contemporary contexts alike.
It’s not just about looks, though.
The Woodford Turing is highly practical and efficient, too. Able to burn either firewood or solid smokeless fuel, the Turing has an efficiency rating of 75.6% for wood, and a rating of 86.5% for solid fuel.
In other words, the Turing will make your fuels go that much further!
It also has an A+ energy rating and is incredibly clean burning and is DEFRA-approved, meaning it can be used in smoke control areas. The Turing also has Woodford’s ‘Cleanburn’ technology, which will keep the stove glass crystal clear.
Esse 550 Wood Burning/Multifuel EcoDesign Stove
For some people, only the most traditional, classic wood burners will do. If that’s you, then you’ll love the Esse 550.
Esse is a stove brand with a truly unrivalled heritage. Since 1858, Esse has been designing and building stoves in Britain. In fact, Esse has supplied stoves to such historical greats as Ernst Shackleton, Robert Falcon Scott, and Florence Nightingale.
The Esse 550 embodies this tradition with its simple, classic styling, robust, chunky proportions, and timeless silhouette.
The function of the Esse 550 is cutting edge, however.
Providing 5kW of heat, the Esse 550 does so in a highly-efficient way, with a remarkable A+ energy efficiency rating of 82.9%.
With its primary and secondary air vent controls, the Esse 550 is also very clean burning, meeting the latest EcoDesign standards. It’s also DEFRA-approved, meaning it can be used in built-up areas.
In addition to firewood, the Esse 550 can also burn solid smokeless fuels, providing you with greater flexibility when it’s time to stock up on fuel.
The stove’s airwash system also keeps the stove glass crystal clear, so you can enjoy the sight of the fire burning away.
Try out Direct Stove’s video survey service today
Not sure if your chosen stove will fit in your home? Then Direct Stove’s video survey service can help!
Simply book an appointment, and one of our stove experts will arrange a time to speak to you over a video call.
You can show them the room where you want to install the stove, and they’ll be able to advise you whether it’s a suitable location.
Our experts can also answer any additional technical or installation questions you may have.
Give it a try today!
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As one of the UK’s biggest online retailers of wood-burning stoves, we know how to make buying your stove as easy as possible.
Not only do we offer FREE UK mainland delivery on all of our stoves, but we also offer 14-day no hassle returns. There are also a range of easy finance options (including 0% over 12 months) to help you spread the cost of your new log burner.
Our experts are also on hand to answer any questions you may have prior to purchase. You can reach them on 0161 516 9648 or at: [email protected]
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