A year on, Liz reflects on the decision to install a log-fired biomass boiler.
Why on earth would Charlie and I want to commit ourselves to years and years of wood processing and stoking a boiler to heat our house?
It’s a question I’ve asked myself on many occasions. But the decision to install a log-fired biomass boiler wasn’t something we did on a whim after too many gin and tonics.
This wasn’t a rushed decision. We thoroughly researched, costed and planned for more than 2 years before we finally took the plunge in November 2020. So, as we approach November 2021 this seems a good time to reflect on that decision.
Why biomass?
Well quite simply we wanted to get away from relying on fossil fuels.
When we bought Craigellie House in August 2018 there were 3 oil boilers servicing different parts of the house and 3 oil tanks in the garden. The oil boilers were taking up valuable cupboard space. The 3 large green monstrosities sitting in the back garden overlooking the house weren’t exactly pretty and the cost to fill them was eyewatering.
So, we researched the alternatives, egged on by the desire to move away from the need to wear 5 layers of jumpers in the winter.
A ground source heat pump with enough beef to heat our sizeable property required 3-phase electricity. We don’t have 3-phase, so that was out. Air source heat pumps work at a constant low heat. However, our house has high ceilings and stone walls. These features mean we need a higher temperature to warm the rooms, even with our best insulation efforts. Loft insulation, under floor insulation, magnetic secondary glazing are all part of the puzzle, but more on that in another post. Additionally, air source heat pumps are expensive to run. In reality, most of the heat is required in the winter when we’re lucky if we have any excess solar at all from our solar panels.
So, biomass it had to be, or not at all.
Incentives
The costs to install a biomass boiler are huge so let’s face it, not many people would do so without some kind of incentive. Let’s take a look at what was on offer in terms of RHI (Renewable Heat Incentive) at the time.
RHI is a UK-wide, government-backed scheme. It encourages homeowners to move away from fossil fuels for heating (oil, gas) towards more renewable alternatives. A number of years ago when this scheme first came out the installation costs were even higher than now, and the subsequent pay-out was also very favourable.
Participants in the early scheme receive payment based on their heat production with no upper limit to these payments. Some even left windows open with the heating on full blast. Others abused the scheme. They were using the biomass boiler to dry wood chip, which was then being left out to get wet so that more RHI could be generated by drying it again.
More recent RHI applications must be accompanied by an EPC (Energy Performance Certificate) and the incentive is capped.
We did some quick calculations about the domestic RHI. Despite paying out over 8 years, it wouldn't come close to covering our substantial installation costs.
Next, we investigated the commercial package. The criteria were specific. We had to prove our quarterly heat usage for commercial use exceeded that of our private living space. Thankfully, we found we were eligible because our East Wing operates as a self-catering property, and we were setting up our West Wing for B&B.
Logs, chip or pellets?
The decision was primarily a financial one, though we certainly did look closely at the other options. We first ruled out chip which, in our opinion, is better suited to farms or those with significant space and machinery to move it around.
Pellets are certainly more convenient, but there are a few issues. Firstly, most are imported. Secondly, they are dried using huge log-fired biomass boilers – so maybe not quite as green as we would like to think. And thirdly, you are very much at the whim of the supplier in terms of rising pellet costs.
In our part of Perthshire there is no shortage of trees and raw timber is not difficult to come by. So, it was the log boiler which won the day.
The negatives of a log boiler
Yes, there definitely are.
Our wood needs to be seasoned – left sitting for at least a year for the sap to dry out – as ‘green’ timber has too high a moisture content. Burning wet wood produces more smoke and harmful polluting by-products and tars up the flue. It is also much less efficient. Storing that much timber takes up a lot of space.
We process the wood into logs – cutting to length and then splitting. These are then stacked and stored in a shed where they continue to dry out. That’s a lot of man – and woman – hours.
The biomass also needs constant attention – stoking, filling, checking up to 6 times a day in winter – and it’s a smelly job because the smoke wafts out and gets in your clothes and hair. The biomass chamber also needs cleaning out to get rid of the tar build up – and that’s an even filthier job which takes several hours (thankfully not mine).
But there are positives too
Our house is warm!
We have one boiler in our paddock (and a back-up oil boiler in our garage so that we can go away). And there are none in the house, so space was freed up for storage.
We also keep fit and strong doing all the logs. Actually, in moderation, it’s not such a bad job.
We use zero oil and with oil prices on the up that’s a really good thing.
There has to be a feel-good factor too – we are doing our bit for the environment. Thus far we have only used logs from our own trees so zero road miles. The longer-term plan is to purchase locally cut timber and process it ourselves.
And with our first RHI payments in the bank we are starting to claw back our investment – just 20 years to go!
