Saving money on heating – 2

This is an expansion of the previous post, as it seems I have more luck with a wood stove than the general experience.

Saving energy seems to be all the rage these days, it isn’t just me, both the Grauniad and the Daily Fail seem to be at it. Looking at the scepticism in the Grauniad article comments, it seems not everyone can make a wood-burning stove work for them from a financial viewpoint.

My experience is most definitely that a wood burning stove can reduce heating bills. Indeed, if I could think of an intelligent way to go about hot water I could bring my gas bill down to just cooking; I managed to avoid running the central heating at all last year, but I didn’t particularly want for heat.

I figured it would be interesting to revisit this, to bring out the parameters that enable me to heat the whole house, which seems key to transforming a wood burning stove from lifestyle accessory to money saving tool. I have to admit that I bought the stove as a lifestyle accessory in the easy party times before I realised I wanted to retire early, so I am sweating an existing asset πŸ˜‰

#1 Don’t own too much house

I had a rough experience with negative equity early in my house owning career. This has made my vision of a house very different to that of most of my fellow Britons. I do not have a deep existential belief that property always goes up in value.

Sarah Beeny and the rest of Britain may believe houses always go up, but I don’t, because I know otherwise from personal experience

As a result I didn’t stretch myself to the maximum mortgage I could get after that first one, I bought as much house as my living requirements wanted. As a single man I bought a two-up-two down, because that was all I could afford. When I bought this house, with DxGF we went for a three bed semi, which suited us about right, and it suits my current living arrangements right for DW and I.

It is small compared to the houses of many of my work ex-colleagues, many of whom subscribed to the mantra of buying lots of house because it made them feel good about themselves, and well, y’know, housing always goes up so it’s a great investment too. Good luck to them, and obviously with kids you need more than the one spare room we have. Somewhere between when I grew up and now, we also collectively decided that children each had to have their individual bedrooms, which obviously puts the pressure on families as we increasingly live separate lives.

Nationwide house price index. House prices never go down, well, until they do.

Over a thirty-year plus house owning career the price of a house probably does go up in real terms, but the change is not smooth or monotonic. There be switchbacks in the housing market, and woe betide you if you buy and take a switchback at the same time as some bad luck. If you can sweat it out that’s great, but lose your job or need to move at the wrong point in the cycle and you are exposed to negative equity. I cannot describe the soul destroying feeling of paying down a mortgage on a house you’ve sold for less than the mortgage…

What’s that got to do with heating? It’s a damn sight easier to heat a small space than a big one πŸ˜‰ Heating a modest house is always going to be easier than heating a McMansion, all other things being equal. That is not the only extra cost of a larger house, you also have to clean, furnish and decorate the extra space too.

FWIW some people claim you can get round having too much house by just heating part of it. Don’t do that for long periods. You may be able to get away with it in drier parts of America but not in the damp of a British winter. You need both ventilation and some heat in a house otherwise condensation will get you, and you’ll have to redecorate that room in Spring πŸ˜‰

#2 prize features in the house that help you save energy

The trouble with these are you have to do this before you buy the house. I was lucky in getting a collection of features that worked well with a wood burner, but it may be of value to call them out.

The principal disadvantage of a terraced house or semi is you get to hear your neighbours, so you want to avoid choosing a house next a young couple of child-bearing age πŸ˜‰ I should have jumped to that with my first house. On the upside, you get to use some of their heat on the party wall, which is a quarter of your wall area. Although it’s probably a significant effect it isn’t make or break. In an ideal world I’d like to live in a detached house, and would look to retain some of the following features:

Cavity walls

wall temp upstairs

My house was already cavity wall insulated, which is something else to look for, but it had crappy single glazing which I put up with for far too long. The actual cost of changing this wasn’t too bad – I had a grossly inflated expectation of the cost which is why I stalled it for a long time. I’d buy a house with single glazing over one of a similar size that didn’t have cavity walls any time. I’d go as far as not having cavity walls would be a dealbreaker for me in any future house purchase unless power costs came down a lot. Retrofitting cavity insulation is cheap enough, andΒ  you can do something about single glazing, but insulating solid walls is very, very dear it seems. Having lived with both, solid walls are comparatively cold in winter, and seem to increase the thermal delays of the house. That’s bad for the typical work pattern of non-occupation during the day, unless you can reduce draughts so the heat isn’t lost in the day. That doesn’t usually go with the sort of house that has solid walls, because of their age.

Central chimney

the chimney wall temperature is 22C, 2C higher even after the stove has not been running for more than 12 hours overnight

If you are going to use a stove that is, obviously irrelevant if you use gas central heating. You want to use that precious heat all for yourself. You don’t want to share half of it with the neighbours, or even worse do your bit for global warming by sharing it with the great outdoors.

The chimney in my house goes up the middle of the house. As such the flue runs past the bedroom wall and the wall of my den (the second bedroom) and the heat does warm the walls and the room perceptibly – though with a latency of several hours. As shown, the temperature of the chimney breast upstairs is 2C higher than the adjacent wall, so it is effectively a low-temperature radiator about 0.5m by 2m area. This is measured 12 hours after the stove has stopped running, outside temperature was about 14C.

That’s good in practice, we tend to start the fire when the sun goes down and the first floor is perceptibly warmer the next day than the ground floor. Which is great, it works with the usage pattern of the space. I would also favour a house with a chimney running through the middle of the house in a future purchase, assuming it were a two-storey house.

Of course you don’t get character with a house like mine. This sort of thing doesn’t particularly trouble us, but from TV shows it seems this matters to many people, not just Sarah Beeny πŸ˜‰ In general you need more energy to heat a house with character because they tend to be more draughty and have solid walls, this is all part of the complex tradeoff you have to make when choosing somewhere to live. Having a significant heat gradient from the room to the fire does make things feel more homely, as it draws people together, and probably panders to some atavistic memory of our forebears in front of the fire. Not for nothing does the cat curl up in front of the fire rather than the radiator. That is also part of the character of a place, I love it when we go away to somewhere in the winter with a massive open fire in a huge inglenook fireplace with a heat gradient thatΒ  made us feel cosy in the warm space. However, I wouldn’t like to pay for it every winter day.

#3 Insulate and draught-proof first

The great thing about insulation is that it’s cheap, and a reasonably easy DIY win. I only have three inches of loft insulation, and a reasonable amount of junk up there. Go for more than 3 inches and you can’t use the loft for storage since 3 inches is the typical depth of the rafters. In a modern house you can’t store much in the loft anyway, because of the cheap prefab woodwork cluttering up the loft. Although I only have three inches of rockwool and the current recommendation is for more than twice that, the loft boards and the junk probably help. It’s damn cold in the loft compared to the house in winter πŸ™‚

Draught-proofing is best done in double glazed windows using integral rubber seals, but you can DIY here, though none of the DIY solutions last more than a couple of years. They are at least cheap DIY. Doors are also a problem. For me the double glazing fixed draughts almost totally (there is a porch and old conservatory that keep draughts from the main front and back door). I believe nutting draughts is a major part of why I can avoid using the central heating, because the house can hold the heat from a fire in the evening almost through to the next afternoon.

My previous Victorian two up two down had individual room gas fires. For a gas fire to work it has to be open to the outside to vent the flue and open to the inside for the heat to get out. No complaints about the efficacy of the gas fires, but the house would not hold heat from the evening to the morning, let alone the afternoon. It was always brass monkeys in the morning, and that’s a bastard for getting up to go to work.

In the current house I didn’t notice the problem of the house not holding heat, because like most people I’d set the central heating to come on a bit before it was time to get up. So that solved the problem with the brass monkeys, but the leakage of heat meant the wood burning stove couldn’t work well for the whole house – it had the same problem as the previous house, it was freezing in the morning. So I used the central heating just for the morning. This combination reduced the gas bill, but what transformed things was fitting the double glazing. That allowed the wood stove to take over the heating of the whole house. The stove is a small one with a rated max output of 6.5kW. In all fairness to the installers, it was only specified to heat the front room, which it was easily able to do despite the initial draughts, and those draughts were hardly perceptible to me. It’s extremely necky to then pitch for using a single room heating appliance to heat the entire house, but it works for me.

So the takeaway is that you can heat your house with a log-burner alone, as long as the house isn’t too big, as long as you have dealt with insulation, double glazing and draught-proofing properly first. Insulation and draughtproofing are relatively cheap to do compared to installing a log burner. I’ve probably spent Β£10k on windows and the log burner combined. It’s hard to say where the break-even point is. The windows have probably added something to the value of the house, if only because the previous ones were obviously ropey. If I say the total outlay is Β£8k allowing for that then the breakeven point is about 8 years or so, shorter if gas prices rise faster than inflation.

various other related issues

My gas boiler is over 20 years old, and a modern one would undoubtedly be more efficient. I have savings allocated to replacing that, but I am putting that off because there seem to be very serious reliability problems associated with condensing boilers which is the only type allowed to be fitted these days. The problem seems to be the extra complexity, and the condensate has to be discharged outside, and there is a problem with the discharge pipe freezing so the condensate backs up and the safety system shuts down the boiler. A heating system that doesn’t like freezing temperatures outside isn’t the greatest triumph of engineering smarts IMO. On the other hand, I would benefit from a modern pressurised on-demand hot water system without storage. Downsides of that are I have mixed feelings about the lack of resilience against interruptions to the mains water supply that I expect to be increasingly likely as we have interruptions to the mains power supply. The 25 gallon cold water tank in the loft gives some peace of mind there πŸ˜‰

Since I don’t use the boiler for heating I can eat the lack of efficiency, and I haven’t come to a conclusion about the hot water. Losing the storage tanks would KO any opportunity to use solar hot water, and I could probably halve the dwell time of the boiler by changing the primitive mechanical programmer for a modern electronic one to get just one heating period for hot water a day rather than the two the current programmer insists on. You probably need that for a four-person family but it’s overkill for the two of us most of the time.

All round, saving money on energy/heating demands a whole systems approach and a reasonably methodical process before you do anything, and the opportunities may well be constrained by the design and size of your house.You have to start with what you have and work with it, and unfortunately the main issues are the size and design of your house, which you’re pretty much stuck with.

Running a 25 year old boiler and a modern wood stove isn’t the obvious way to attack this, but it works well enough for me, my combined gas and electricity bill is ~Β£500 and I believe they are still significantly overcharging me on estimated consumption. This is less than half the typical UK power bill, and it is notable that about a third of it is the fixed standing charges.

I was lucky with some of the features of my house, but only realised the benefits once the last link had been completed of the insulate and draughtproof chain, which was replacing the windows. Unfortunately, it looks like you have to get everything to work together before you can use a wood burning stove for the main or only heat source. Mine is only 6.5kW flat out. Using this calculator a replacement whole house boiler for my house would need to be 17kW with typical assumptions. The improved heat holding capacity I’ve ended up with probably explains why a wood burning stove works for me. I can leverage the investment by using it to replace my heating gas consumption, shortening the break-even period.

Looking at all the grousing in the Guardian comments, many people buy wood stoves as a lifestyle acessory, and there’s nothing wrong at all in that. It is then a lifestyle cost, not a way to save money, even though some of the cost is defrayed by reduced gas usage. It’s reasonable to allow for that but it won’t pay for it.

Bear in mind that in the UK people typically move house every seven years so the opportunity for cost recovery is limited. I’m unusual in that I stayed in my first house ten years and have only moved once, I’ve lived in this house for 14 years and don’t have any current plans to move, soΒ  I can expect to reach breakeven and into the free lunch beyond.


13 thoughts on “Saving money on heating – 2”

  1. The house we have just moved to has still got single-glazed windows and is fairly limited in the insulation department. It is already starting to get pretty cold without the central heating on and i reckon it is going to be a chilly (or expensive) winter coming up in the new home!

    I’m going to get a few double-glazing quotes, but not sure if i want to commit to the cost just after moving in.

    The previous owners had installed a rather fetching victorian fireplace, but it is quite small and looks like it is more suited to burning coals rather than wood. Looking forward to getting it fired up though anyway.

    Not sure if the missus wold permit a move to a wood burner straightaway, but i’ll bear it in mind for the future, especially as the chimney is positioned in the centre of the house too.

    Interested in your point about interruptions to the mains water supply becoming more frequent. Do you believe that will happen due to the water infrastructure falling into decline or dis-repair through under investment?


  2. > The stove is a small one with a
    > rated max output of 6.5kW

    Zounds, that is smaller than I realized! Our small woodstove (heats downstairs 800 sq ft) is 19kW and the bigger one is 20.6kW (upstairs 1000 sq ft with bedrooms). Downstairs is on a concrete slab, so without a blower

    After getting experience with both of them, the larger one’s features (large firebox, damper bypass, fan, & dual level cooking surface) have made it my favorite by far.

    A new feature that appeared this year (wonder if it can be retrofitted) is an electric start. The igniter heats room air to 1400 deg F in a concentrated jet directly onto your kindling getting the fire underway in about 2 minutes… no newspaper needed, no opening the door to establish a draft.


  3. “so without a blower”…

    So without a blower, the thermal mass means the air takes about 2 hours to come up to temperature.


  4. @Donal it is definitely worth getting quotes for double glazing. I thought it would be about 10k but it turned out less than half that. The improvement it makes to heat retention is remarkable, and if you’ve just moved in then you have most time to amortise the capital cost. But then you’re probably boracic lint due to all the moving costs. I got this wrong leaving it 10 years πŸ˜‰

    Re the water, I believe our water supply is now pressurised using pumps rather than the static head from water towers (obviously intermittently pumped in those days). Britain is going to be desperatly short of power in the coming few years. This is according to ofgem, rather than a bunch of tinfoil hatters, due to known issues of having to close some high carbon plant. I would say we are reaping the whirlwind of the Thatcher sugar rush – electricity used to be dearer than it is now in real terms but the likes ofthe CEGB worried about resilience, which we don’t any more, because the market will sort it out… The market improves efficiency, which also drives out resilience.

    That pump pressurised network will therefore lose pressurisation as soon as power fails, unlike in days gone by when the head of the water towers gave some resilience at least for a controlled shutdown, and the recovery time is lengthened if air gets drawn into the water system ISTR, for health reasons.

    You can live days without power, and indeed days without heat, though I have local storage of fuel. But you just can’t live long without water in a town, particularly because of sanitation rather than drinking water, which they usually dispense from bowsers. I recall digging holes in the garden in the 1970s because you had to eke out the bathtub full of water carefully. So I like my header tanks in the loft, even if they aren’t fashionable! So the long answer is it isn’t the water system I think is the problem with investment, it is the power system. And yes I did buy some AGK after the 7% drop, and I will add to the holding if the price drops more. Their time will come IMO as the JIT world meets energy realities, both in the First and in the emerging world πŸ˜‰

    @George remember that UK homes are _much_ smaller than US homes, and generally of brick or cinder block construction where I believe wood framing is more the US thing. Not sure if that makes a difference in draft-penetration.

    My stove is an Island 1 which is apparently 2-7kW. If I were starting again I would probably go for the II with a back boiler for hot water too. US homes I’ve visited have often used forced air heating which is probably a good match to a solid fuel stove, UK houses almost universally use circulated water as the heat conductive medium in central heating, so there isn’t much solid fuel central heating here AFAIK.

    Do you use both at the same time? Fuelling 20-30kW with wood is going to be a pretty physical activity, you storage must be quite sizeable. I can see why you felt the harvest from your land might need augmenting a little bit!

    The electric start sounds nice, as long as it’s possible to use the old fashioned way as well, to avoid the dependency on the power grid, particularly in rural areas πŸ˜‰


  5. USA homes built after 1970-ish, at least where it gets cold, usually have a plastic vapor barrier over wood frame regardless of whether the house is brick or not.

    Water as a heat distribution system is rare, though with the advent of PEX tubing and radiant floor modules, it’s gaining popularity in places where natural gas pipelines are available.

    In the fall & spring, we typically burn 1 arm load of wood(*) in the morning and/or evening in the upstairs stove. If we want heat downstairs, then we’ll stoke the other stove with the same amount over a slightly longer period, usually when we’re expecting company.

    Neighbor who is burning wood in a fireplace (I don’t think they have a stove insert) likes to have 6 cords of wood (about 22 m^3) for the year. If he doesn’t have a stove insert, then we’d probably only need 3-4 cords per year.

    Another neighbor has a huge propane tank (as big as a luxury car) instead of chopping wood. That’s a pretty good way to go, except the propane has to travel at least 100 miles via truck to reach his house. And I’m not sure if the propane comes via a pipeline to the distribution center here or if it has to be shipped in.

    Power outages are common during the winter when you’re living outside the metropolitan areas. When it’s only a few hours (80% of the time), it’s not a big deal, but you can usually expect to go without power for a couple days every winter, so it’s important to have a heat source that doesn’t rely on the grid. In 2008, I think it was, we were without electricity for 5 days!

    (*) 1 arm load is 5-6 pieces split to about a 4″ triangular shape by 16″ long. I haven’t been able to estimate how many cords or cubic meters that is.


  6. @George you have strong arms πŸ˜‰ Even allowing for a 14″ stove width, I wouldn’t expect to get through more than two of those size logs perhaps three if it were snowing outside!

    Underfloor heating is excellent, I don’t have it myself but I’ve experienced it.I still don’t feel right plumbing with anything other than soldered copper, but I’ll have to join the 21st century PEX world one day, if only for cost reasons πŸ˜‰


  7. @Ermine that’s very scary about the whole power issue, but not really surprising. It’s a shame we didn’t keep on investing in our nuclear industry back in the day.

    i think the environmentalists got it wrong regarding nuclear waste. Yes it’s horrible stuff, but all the coal burning power stations have produced a similar form of pollution too. Anyway, i digress. Thanks for the info on the water infrastructure, i’d never really thought much about how water comes out of my taps. There are a lot of things we take for granted.

    Maybe the government will be requisitioning all those old water towers that have been converted into family homes in the next few years!!

    BTW have you seen these:

    We could be using them to charge our ipods in the future πŸ™‚


  8. @george looks I must start pumping iron πŸ˜‰

    @Donal I was under the impression that we were continuing with nuclear build, overbuilding on the existing sites that are reaching end of life? It seems to be the finance and commercials that we’re making a right muddle of, ’twas ever thus.


  9. I used a multi fuel stove and it was great to have the optons of both wood,coal and others. We found that when we opened all the doors ( large 250 year old cottage but have now downsized) we hardly had to use the oil central heating. If the coal is used properly (I know not the most environmentally friendly fuel but i’ll stop using it when China, The States and India get on board and sign the Kyoto Treaty- and we did use the more eco firendly smokeless coal) we could get up in the morning and get the stove going again. The house would still be warm. I wish I had installed a back boiler at the time of our renovations!


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