Author Topic: Biomass Boilers - suitable for small properties?  (Read 773 times)

IanDG

  • The p*** artist formerly known as 'Windy'
    • My Instagram
Biomass Boilers - suitable for small properties?
« on: January 22, 2020, 10:38:32 am »
Anyone had one fitted and got any experience good or bad (or decided against and if so why)? Had quotes for different systems for the cottage renovation and thoughts were towards biomass. However, recent conversation (with the plumber)  have left me questioning whether a wood pellet system is suitable for a small domestic property (155 m^2 floor area) with just 2 residents and infrequent (summer) use.

Thanks

Re: Biomass Boilers
« Reply #1 on: January 22, 2020, 02:49:08 pm »
Yep, I've had a wood pellet boiler since Feb 2014 and have an ETA PU15, plus solar thermal panels.

Pros:
* this particular boiler has very capable and adaptable software which act as a mini building management system so can work with other equipment easily.  It controls my solar hot water rather than having a separate controller, enabling it to prioritise the solar.  Can also work with other boilers, i.e. the biomass runs as lead boiler but have top up or back-up heat from a conventional oil boiler for example.  It can also handle zoned circuits with different flow temperatures to account for mix of underfloor heating and radiators.
* 7 years of renewable heat incentive income will pay back approx 70-80% of the capital cost in my case.
* mine has automatic vacuum feed of pellets from a 4 tonne pellet silo in the garden (max. vacuum feed length is approx 20m for my boiler)
* Boiler has internet connection (hard wired to a powerline adaptor) so I can do full remote control if required.  Service engineer is also set up to view it if required to investigate faults/issues.   However, many boilers now have some similar functionality.
* unlike an alternative heat pump solution I didn't need to increase radiator sizes to compensate for lower flow temperatures.
* very efficient and produces little ash.  The onboard ash box is about the volume of a couple of shoe boxes.  Even in the dead of winter I only have to empty it every few weeks.  Probably don't empty it more than 8-10 times a year. Ash goes on the garden.

Cons:
* complexity of software is not for everyone.  Fine for me, as I fine tune it throughout the year.
* boiler needs to be sized carefully for the house, as you can't just turn it on/off like a gas boiler every few minutes. Consequently, if the house is really cold it takes a long while to get the temperature up.  Accordingly, instead of switching off at night I set back the target temperature a couple of degrees and start it back up to day target temp from around 05:30 to give it a chance to get up to speed.  Summary - not particularly responsive.
* servicing costs.  I wish I'd known more about this.  It costs me around £450 a year for an annual service, plus any unexpected parts.  This is fine while you're getting quarterly RHI payments but when they run out next year it's quite a cost.
* I've had flue problems with mine - poor design, although installation options were limited.
* slight smoky smell, particularly in windy weather when you might get a bit of backdraught into the flue.  Recommend boiler is in a utility room where you can shut the door, or out in a garage.
* pellet costs, when I installed the boiler, would give delivered heat cheaper than oil. That is not currently the case, although again the RHI does compensate a bit for this.  I only need a fill up of the silo (4 tonnes) once a year, which costs around £1k for an older property of approx 155m2 heated floorspace.

Would I install another one? Thoughts:
* since I installed mine, the sustainability of wood pellets has undergone a revision in thinking and the environmental case is probably a bit weaker, especially as the electrical grid cleans up.  Nonetheless, the latest DEFRA emission factors for GHG reporting still show a significant benefit in using wood fuel.  My purchase was very much driven by environmental concerns so I definitely wouldn't revert to an oil boiler.
* ongoing service costs, additional fuel running costs (compared to current oil prices) and the space required for a pellet boiler/silo are  significant downsides.
* For an older property like mine, which isn't ideally suited to economical use of an air source heat pump, I would probably now install a hybrid heat pump/oil boiler system so that the heat pump tackles base load for most of the year and the oil boiler kicks in to deal with higher temperatures.  However, such things weren't readily available 5 years ago, and even now the installed market is limited.
* initial capital cost was eye-popping.  More recently, the RHI scheme was amended to allow the RHI payments to be assigned to a third party which has opened up the market to funded installations which overcomes some of the hurdle for homeowners.
*I'm not planning on moving house any time soon, but if I was I would have concerns about whether the heating system might put off some potential buyers a bit.

IanDG

  • The p*** artist formerly known as 'Windy'
    • My Instagram
Re: Biomass Boilers - suitable for small properties?
« Reply #2 on: January 22, 2020, 07:10:22 pm »
Thanks @Quisling, the cottage is similar size at 153 m2. Had quotes for ETA and Windhager.

Re: Biomass Boilers - suitable for small properties?
« Reply #3 on: January 22, 2020, 10:49:02 pm »
Also, make sure you consider space for delivery wagons. Our bulk blown pellets come on a 20+ tonne wagon. Blowing time into the silo is about 10 mins, so realistically the wagon is parked in the road for about 30 mins.
A mate has an Okofen boiler which is great but he skimped and manually loads in up to 3 x 15 kg bags of pellets a day in the winter which would quickly be uninviting, and also not practical if you need to keep the house protected against frost if you take a 2 week winter holiday.
The 4 tonne capacity silo is approx 2x2 metres in plan and 2.4m high, so not the most attractive garden feature ::-)

Re: Biomass Boilers - suitable for small properties?
« Reply #4 on: January 26, 2020, 11:55:37 am »
I've spoken with a few people recently who have systems fitted. These are mostly farmers living in old properties.

Not one of them would recommend it - if it wasn't for RHI they would have chosen something else and RHI doesn't last forever (7 years?) They do all say their houses are warmer than before but costs have increased. These are all wood pellet systems and the price of pellets has outstripped the price of oil. I'm told that part of the increase is that horse owners have started using pellets as bedding (no dust, absorbent) which has affected the price of pellets.

It's hard to find a good installer to properly design and fit the system and who is capable of diagnosing breakdowns. These can be complicated systems. A couple of those I was speaking with had used the same guy but none of them were totally happy and dread a major breakdown.

You will use far more pellets than they will tell you! By some margin. I remember our neighbour telling us when he had his boiler installed that he would only need a couple of pallets (bagged) a year. Work out the kWh values.

We use LPG in our own 2 bed cottage - don't tell Greta  :P  but at 88 m² it's easy to heat. And we've been using LPG for 30 years. It works well for us but keeping on top of suppliers to get a good price is vital. A new boiler uses very little gas, it's very controllable, 10 year warranty if you choose carefully, £65 a year to service it (check it over basically) and if it does break down even out of warranty, any LPG heating engineer can fix it with off-the-shelf parts. As a new customer, any of the LPG suppliers will offer you a free bulk tank and some free gas to entice you. 

As an alternative, what about an air-source heat pump? I've a bit of experience with those too, my mum had one fitted two years ago by her housing association. It's been great - low bills, reliable and has 'fit and forget' controls which is ideal for mum. Another neighbour has it in his farm conversion (rebuild) and says he's happy with it. His is huge though and the fan is very noisy, but he sited it where he doesn't hear it.

And my BiL is having one fitted in the next few weeks in his new build. He's hoping it will be future proof and with green electricity seems a reasonable choice. The one thing to realise about a heat pump is that they need to work almost continuously at a low flow temperature (large radiators or underfloor) so they're perfect for those at home all day in a well insulated house, not so good if you are away a lot and in an older property that can't be easily insulated.

HTH
 


Re: Biomass Boilers - suitable for small properties?
« Reply #5 on: January 26, 2020, 12:03:43 pm »
£1k for 4 tons is the same price as kiln-dried ash logs, which surprises me.  I thought the pellets would be made from waste (sawdust) and twiggy stuff that's useless in a conventional stove.
Never tell me the odds.

Re: Biomass Boilers - suitable for small properties?
« Reply #6 on: January 26, 2020, 12:13:53 pm »
I've spoken with a few people recently who have systems fitted. These are mostly farmers living in old properties.

Not one of them would recommend it - if it wasn't for RHI they would have chosen something else and RHI doesn't last forever (7 years?) They do all say their houses are warmer than before but costs have increased. These are all wood pellet systems and the price of pellets has outstripped the price of oil. I'm told that part of the increase is that horse owners have started using pellets as bedding (no dust, absorbent) which has affected the price of pellets.

It's hard to find a good installer to properly design and fit the system and who is capable of diagnosing breakdowns. These can be complicated systems. A couple of those I was speaking with had used the same guy but none of them were totally happy and dread a major breakdown.

You will use far more pellets than they will tell you! By some margin. I remember our neighbour telling us when he had his boiler installed that he would only need a couple of pallets (bagged) a year. Work out the kWh values.

We use LPG in our own 2 bed cottage - don't tell Greta  :P  but at 88 m² it's easy to heat. And we've been using LPG for 30 years. It works well for us but keeping on top of suppliers to get a good price is vital. A new boiler uses very little gas, it's very controllable, 10 year warranty if you choose carefully, £65 a year to service it (check it over basically) and if it does break down even out of warranty, any LPG heating engineer can fix it with off-the-shelf parts. As a new customer, any of the LPG suppliers will offer you a free bulk tank and some free gas to entice you. 

As an alternative, what about an air-source heat pump? I've a bit of experience with those too, my mum had one fitted two years ago by her housing association. It's been great - low bills, reliable and has 'fit and forget' controls which is ideal for mum. Another neighbour has it in his farm conversion (rebuild) and says he's happy with it. His is huge though and the fan is very noisy, but he sited it where he doesn't hear it.

And my BiL is having one fitted in the next few weeks in his new build. He's hoping it will be future proof and with green electricity seems a reasonable choice. The one thing to realise about a heat pump is that they need to work almost continuously at a low flow temperature (large radiators or underfloor) so they're perfect for those at home all day in a well insulated house, not so good if you are away a lot and in an older property that can't be easily insulated.

HTH

Wood pellets also compete for materials with kitchen manufacturers demand for chipboard.

I'm working on a plan to move our heating from gas to air source heat pump in the next couple of years. The house is old, so needs some investment in more insulation first, but we'll get there. I'm still far from convinced that biomass is a good use of land and materials, although it's probably better than digging up long dead trees.

Kim

  • Timelord
Re: Biomass Boilers
« Reply #7 on: January 26, 2020, 12:59:27 pm »
* since I installed mine, the sustainability of wood pellets has undergone a revision in thinking and the environmental case is probably a bit weaker, especially as the electrical grid cleans up.  Nonetheless, the latest DEFRA emission factors for GHG reporting still show a significant benefit in using wood fuel.  My purchase was very much driven by environmental concerns so I definitely wouldn't revert to an oil boiler.

Are we talking CO2, or does this account for particulates as well?  I can't imagine burning biomass is anywhere near as clean as gas or oil, even in a well-controlled boiler.

Particulate emissions from wood burning seem to be an elephant in the room that people are starting to wake up to, and I'd be reluctant to invest in a system that could easily fall foul of future regulation, even if it's a negligible problem in rural areas.
Careful, Kim. Your sarcasm's showing...

Re: Biomass Boilers - suitable for small properties?
« Reply #8 on: January 26, 2020, 01:49:15 pm »
I think I'd be focussing on measures to reduce heating requirements through insulation, etc., more than on which source of power.   I suspect electricity, remotely generated &/or via solar panels is probably the most future-proof.

IanDG

  • The p*** artist formerly known as 'Windy'
    • My Instagram
Re: Biomass Boilers - suitable for small properties?
« Reply #9 on: January 26, 2020, 02:36:58 pm »
I think I'd be focussing on measures to reduce heating requirements through insulation, etc., more than on which source of power.   I suspect electricity, remotely generated &/or via solar panels is probably the most future-proof.

That's why I've been stripping out all the existing stud walls. Going to be 4" kingspan all around the inside of external walls. Currently has oil system but the boiler is condemned and the tank is old, only single skin and needs replacing/moving - so have the option to start again.

IanDG

  • The p*** artist formerly known as 'Windy'
    • My Instagram
Re: Biomass Boilers - suitable for small properties?
« Reply #10 on: January 26, 2020, 02:43:34 pm »
I think I'd be focussing on measures to reduce heating requirements through insulation, etc., more than on which source of power.   I suspect electricity, remotely generated &/or via solar panels is probably the most future-proof.

That's why I've been stripping out all the existing stud walls. Going to be 4" kingspan all around the inside of external walls. Currently has oil system but the boiler is condemned and the tank is old, only single skin, too close to the house so needs replacing/relocating - so have the option to start again

Re: Biomass Boilers - suitable for small properties?
« Reply #11 on: January 26, 2020, 03:05:24 pm »
I'd really prefer to go air source heat pump (or ground source) if it becomes viable to replace the gas boiler rather than install any system dependent upon deliveries and onsite storage.

The insulation project will be more or less completed this year with luck and a fair wind so a change away from gas fired central heating moves a step closer.

Seems far more sustainable too in the longer term which also appeals.

Mrs Pingu

  • Who ate all the pies? Me
    • Twitter
Re: Biomass Boilers - suitable for small properties?
« Reply #12 on: January 26, 2020, 03:10:25 pm »
Ian, just a comment on your insulation - are your walls not mass masonry? I didn't think Kingspan was breatheable
Do not clench. It only makes it worse.

IanDG

  • The p*** artist formerly known as 'Windy'
    • My Instagram
Re: Biomass Boilers - suitable for small properties?
« Reply #13 on: January 26, 2020, 06:29:03 pm »
Ian, just a comment on your insulation - are your walls not mass masonry? I didn't think Kingspan was breatheable

I think it's Kingspan - a stud wall with 100mm insulating material and a 40mm gap between the outside wall and the insulation and external vents for air flow. Will loose 6"+ of room space on each external wall

Re: Biomass Boilers - suitable for small properties?
« Reply #14 on: January 27, 2020, 01:33:06 pm »
My MiL went for ground source heat pump a few years ago, and is very happy with it - it would be top of my list for consideration if I was building or refurbing a property that was remotely suitable.

(She's in a bungalow with solid floors, and also installed wet underfloor heating as part of the process. Unknown insulation under the slab - probably none - but that hasn't affected comfort levels and while she's undoubtedly losing heat downwards her energy use remains acceptably low, I think about €300 of electricity pa for heating, hot water, lighting and cooking.)

Re: Biomass Boilers - suitable for small properties?
« Reply #15 on: January 28, 2020, 10:59:03 pm »
@Kim re: sustainability of pellet fuel, the DEFRA figures mentioned above cover CO2 or CO2e ( including other Kyoto GHGs).  As you point out, particulates are now being identified as a major issue.
A recent report on road deaths argues that you’re 20x more likely to be killed by the back of a vehicle (I.e. poor air quality) than being hit by the front.

Had my house refurb budget/programme extended to underfloor heating I would definitely have bought an air-source heat pump rather than biomass. Sadly not.