You know you want a wood fire for home, but how do you work out the right model for you?
We wondered the same thing, so we went and spent some time with the experts at Jetmaster Heat & Glo to learn about the different aspects of wood heaters that affect both the initial purchase price and the running costs over the long term.
In this article we will cover:
- Design Features & technology of slow combustion heaters, that affect the upfront cost
- The different aspects that determine the running costs of wood heaters:
- Average Burn Time
- Average Efficiency
- Peak Efficiency
- Heating Capacity
- Maximum Log Length
Like most things in life you really do get what you pay for. And it definitely applies in the wood heater market.
Even though we have been burning wood to keep warm for the longest time, there have been real improvements in design features and technology, that are only included in the more efficient wood heater models.
One of the most important things to look for is the preciseness of the air control that the wood heater offers – it’s this feature that will be the really big determinant of the efficiency of your wood heater, so make sure you ask.
Then there is the type of insulation used inside the unit – better units will use ceramic insulation or firebricks to help with insulation and thermal efficiency. Insulation is important because it extends the period of time that heat is retained for, which improves the performance of your wood heater. Plus at the same time it protects the internal firebox from the high temperatures produced by the fire, helping with the longevity of the unit.
Slow combustion heaters are a great source of heat, however the heat generated is generally isolated to the room the heater is installed in. There is now a wood heater on the market that has the ability to operate much like a ducted central heater – it uses ducting and air movement to transfer the heat to other rooms in the home. This is a game changer for people living in areas where natural gas is unavailable, as it gives home owners an option to enjoy the benefits of ducted heat. The only difference is that the heat is generated by an efficient slow combustion heater rather than gas. The good news is that it offers greater performance than an equivalent gas operated unit. Interested? Check out the Australian made Kemlan slow combustion wood heater.
And of course then there is the styling and look of the unit.
There are probably six different variables that need to be looked at when you are assessing the efficiency of any slow combustion heater that you are looking to buy. These are average burn time, average efficiency, peak efficiency, emissions, heating capacity and maximum log length.
Understanding what each of these variables means is helpful in making you make the right choice, and understanding the running costs of the wood heater you are buying.
This is the amount of time that a wood heater unit takes to burn through a standard load of wood. What’s influencing the result? The size of the wood burning box is definitely a key one – the larger the unit, the larger the standard load of wood, the longer the burn time. But how well the unit seals and draws air also contribute. How many hours should you be looking for? An average burn time of 8 hours is good, as this is equivalent to an overnight burn, so you should wake up to a warm house. But it goes up from there – with one unit recording an incredible 21 hour burn time.
Wood Heater Efficiency is simply a measure of how effectively a wood heater can convert combusting wood into heat. Average efficiency is the measure of how effectively the wood heater puts out heat across the whole burn time, whereas peak efficiency is a measure of how efficiently the wood heater emits heat at the optimum point during the burn. The key thing to understand about the difference between average and peak efficiency is that the gap is the amount of air control you have. It’s not possible to run a unit at peak efficiency the whole way through a burn time. That’s why the average efficiency number is so important in determining your running costs.
In Australia, guidelines for the emissions that any wood heater or slow combustion heater being sold can emit must be compliant to AS/NZS 4013 . These are minimum standards. They measure the size of the particles (smoke) coming out of the chimney during a burn cycle. The current standard is that all wood heaters must produce less than 2.5 grams per kilogram of wood burnt. When you are choosing a new wood heater the environment will thank you for choosing one that has low emissions.
When you are looking to buy a new wood heater, choosing a unit that is the right size for your space is actually one of the best ways of ensuring that you’ll get the most efficient heating performance. Most slow combustion heaters come with a recommended heating capacity rating. It’s important to remember that any wood heater can be effective at heating up the room it is located in, but not necessarily beyond that. It is important to ask a professional with experience. In addition to the room dimensions, it is also worthwhile discussing with your heating consultant:
- How well insulated your home is
- Are there floor coverings and window furnishings
- If the windows are single or double glazed
- Age of the house (is it drafty?)
- How cold your winters are
Keeping these variables in mind will help you give the right information to a professional to assist you in choosing a wood heater that will be efficient in your home.
While not strictly a driver of heating efficiency, a larger unit that can take larger logs will reduce the amount of wood chopping, fetching and carrying that needs to be done! So depending on where you source your firewood from, it is worth thinking about the size and length of the logs you have, and matching these to the width of the slow combustion heater you are buying.
Biggest Determinant of Wood Heater Efficiency
This should come as no surprise, but if you’re spending time looking for the most efficient slow combustion heater on the market, then make sure you’ve also sorted out where you’ll be sourcing high quality wood from.
The quality of wood that you put into your wood heater is the single biggest determinant of how efficiently it will burn, and therefore how much wood you’ll use over winter and what your running cost will be.
Plus using poor quality fuel can also reduce the ability of your wood heater to burn efficiently, create a dangerous build up of creosote in your flue, cause the glass to become smoke stained and the reduce longevity of your heater.
So make sure you store your firewood in a dry environment, stacked and covered to ensure plenty of airflow and burn only hardwood with a moisture content between 12 - 20%. More information on fuel quality can be found here.
Thanks to the knowledgeable staff at Jetmaster Heat n Glo Richmond for sharing with us what to look for when buying a wood burning heater.