Green heating in the home

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 girlymonkey 17 Feb 2021

I know this has been discussed in the past, but technology moves on so fast. 

We are about to buy the house we are living in (currently rent from my mum). We are considering whether we keep back some of our deposit to upgrade to something greener for our heating.

We are currently on a bog standard gas combi boiler and radiators. One of my husband's colleagues has got some sort of funding to put in an air source heat pump, so we are watching that with interest. 

Any other systems or experiences that you would like to share with us? Rough coats of installing Vs ongoing savings once installed?

Our house is a 1970s housing estate. 

Post edited at 06:49
In reply to girlymonkey:

No real advice, other than it's not a case of just removing the boiler and fitting the heat pump.

Technology has moved on a lot since we looked at it when we first moved in 12 years ago, but then it was going to be horrendously expensive to effectively take the house back to the cob walls (zero insulation) fit a substantial amount of internal insulation to the walls, put in insulated floor slabs, underfloor heating...

Depends on what the insulation is like on a 1970s house, and what it would cost to upgrade to deal with a heating system that runs at much lower temperature than your existing radiators.

You really need to speak to a reputable installer, not one who is just interested in harvesting grant money. A modern gas combi isn't exactly inefficient or costly to run.

 Sealwife 17 Feb 2021
In reply to girlymonkey:

I don’t have any direct comparisons gas vs air source as there is no mains gas where I live.

People I know who have made the swap from electric storage heaters to air to air units (in 70s ex council terrace) have been delighted with it.  But old storage heaters are not efficient and very expensive to run.

Few years back I looked into replacing my old oil boiler with ground source but was advised at that time that a modern condensing oil boiler would be more efficient, alongside upgraded insulation, which I did.

Technology has moved on since then though.  Do the Energy Saving Trust still do surveys which advise which is best for you?

Assuming your current boiler is operating well, I’d be tempted to seriously upgrade your insulation now, then look at the options again a few years down the line

 artif 17 Feb 2021
In reply to girlymonkey:

Been looking in to this as well, currently on electric storage heaters and multifuel stove and hot water tank. The hot water tank is total waste of money.

Previous owners had added lots of insulation (60's semi detached bungalow in South of England)  so even during this recent cold snap we only ran the stove, but we live in what some would call "cool conditions". Personally I dislike regular C/H radiators etc. always makes me feel lethargic.

Gas c/h seem cheap in money to run, but environmental cost is another matter.

Air source heat pumps seem to be cheap in money and quite good environmentally to run  if the property is well insulated, but expensive to fit.

Electric storage heaters are very green if using low carbon electric, but can be expensive, money wise to run, again a well insulated property makes all the difference. Very basic controls and little control over the heat output

Electric panel heaters are another option, with modern control systems via internet etc these seem to like they may be a viable option

Another consideration is how do you heat your water, you may need a hot water tank to be fitted for some systems or go for an electric shower and hot water tap in the kitchen.

I'm still looking for the perfect option, ideally off grid with wind and solar. 

 Jamie Wakeham 17 Feb 2021
In reply to girlymonkey:

I'm going through this decision process myself right now, and in a few days I will probably have a much more detailed reply as I'm using half term to work on calculations and forecasts.

The fundamental thing you're going to find is that mains gas is cheap.  Ridiculously cheap.  So from a purely financial PoV, it's simply impossible to beat it.  The reason for you to go down the renewables pathway is for CO2 savings.

If you get the RHI (a grant payable to you over seven years) it will, just about cover the cost of installing ASHP.  That system will be around 300% efficient, averaging across the year, but because electricity is at least three times the price of gas, it will barely break even and might actually be more expensive.  If you can bring your electricity costs down (the two obvious ways are to fit PV or to switch to a tariff with cheap periods, either E7 or one of the modern time-of-use tariffs) then you will probably be able to make it cheaper than gas, just.

I'm not saying don't do it!  The RHI only has 18 months or so to go, and if (like me) you suspect that gas prices will eventually rise from their insanely cheap position, then it's worth doing and doing now.  More so if your current gas boiler is on the way out.

You will need much bigger rads, or (preferably) wet UFH.  ASHP works much better at delivering lots of water at 35C, all day long, not a small amount at 70C for an hour or two in the mornings.

And to make it work, you need to insulate as far as possible.  Ignore the crappy current standards and look at getting as close to passivhaus as you reasonably can.  

 girlymonkey 17 Feb 2021
In reply to Sealwife:

Yes, have sent a request to Energy saving trust for a survey, but it's good to hear people's experiences too. Also, not sure if they are actually doing surveys just now!

Our insulation in most of the house is reasonable, but one room is an old garage conversion and it's freezing. We just use it as a kit store and drying room (with a dehumidifier), and keep the door shut to minimise heat loss.

I really want underfloor heating, so if we do change the heating system that is definitely high up the priorities, but very expensive! 

 girlymonkey 17 Feb 2021
In reply to Jamie Wakeham:

Thanks.

I have a suspicion that gas prices will ramp up as the gov try to move us to greener sources, heating is a big source of emissions. I am certainly more interested in it from an emissions saving than money saving but it does need to be affordable too. We are currently with bulb for our electricity, so I feel at least we are reducing our impact there. 

 MeMeMe 17 Feb 2021
In reply to girlymonkey:

If you are looking at an ASHP then it's worth getting someone in to spec it out before you make decisions on changing your heating. We got some way down the road to getting one but the spec of it meant that we'd have to get our electricity supply upgraded which would have cost an additional £7000 which put it out of consideration.

If you can get someone with expertise to come out and look at your house and make recommendations it's really worth it, we wish we'd got better external expertise before we started making changes!

 Jamie Wakeham 17 Feb 2021
In reply to MeMeMe:

That seems odd.  Even a biggish ASHP - with an output of, say, 12kW - will only be drawing around 4 or at most 5kW.  A bog standard UK single phase domestic supply should be good for 20kW.

Do you have some sort of lower powered supply?  I'm not saying you're wrong, but genuinely interested. 

In reply to Jamie Wakeham:

> You will need much bigger rads, or (preferably) wet UFH.  ASHP works much better at delivering lots of water at 35C, all day long, not a small amount at 70C for an hour or two in the mornings.

Only thing I can add is that I have added UFH to the kitchen in my house, as the floor slab was destroyed and needed relaying and it made sense to bury pipes in there when doing so. I run it with a water temperature of 35C and the room is now the warmest in the house and stays warm all day, many hours after the boiler is off as the thermal mass of 6 tonnes of concrete is very high. Floor temperature peaks at 26C and it drops to 21C in about 6 hours in with sub zero outside temperatures in a Wimpey No Fines concrete house. It's good stuff.

 MeMeMe 17 Feb 2021
In reply to Jamie Wakeham:

It was specced at a 16kW (output) heat pump maybe that's the issue?

We don't have a low powered supply as far as I know, the supply is good to 100A.  We're very rural, not sure if that makes any difference. 

It's interesting though that as far as I know we didn't have to talk to the electricity supplier when we fitted the car charger, the installer just needed to know that we were rated up to 100A and the car charger pulls up to 7kW.

 Jamie Wakeham 17 Feb 2021
In reply to MeMeMe:

Might be worth getting a second opinion.  100A at 230V gives you 23kW to play with (actually usually quoted as 20kW, both to build in some safety margin and also because using P=VI on AC isn't really accurate). 

I've just looked at the spec for a typical 16kW pump, and the max current draw is 26A (so about 6kW).   You should be able to run that, your 7kW EV charger, and a toaster, hair dryer and electric kettle, and still not go over your max power.

In reply to Jamie Wakeham:

Old electrics and the specifier's professional opinion that the house requires a rewire perhaps?

 jimtitt 17 Feb 2021
In reply to Jamie Wakeham:

> That seems odd.  Even a biggish ASHP - with an output of, say, 12kW - will only be drawing around 4 or at most 5kW.  A bog standard UK single phase domestic supply should be good for 20kW.

> Do you have some sort of lower powered supply?  I'm not saying you're wrong, but genuinely interested. 

Not when the electric heater turns on which most have either for defrosting and/or to maintain output when things aren't working well. Typically they then can draw slightly over the rated heat output.

In reply to jimtitt:

Just had a quick browse through several manufacturers' specs and the absolute max current seems to be around 30A, with a 32A fuse, so it doesn't really explain it. The installer must have really seen something that spooked them in the electrics.

 ogreville 17 Feb 2021
In reply to girlymonkey:

Possible gas alternatives could be an Air Source Heat Pump, Ground Source Heat Pump, Biomass Boiler, Solar Thermal (for hot water) or modern, super efficient Storage Heaters. ASHP seem to be the way the industry is going these days.

The Domestic RHI scheme has been extended to 31st March 2022.  Apply before that date to potentially getting payment until 2029. Jury is out on what any future incentive schemes will look like to to meet the uk 2050 net zero target. You'll need an EPC from last 24 months with no recommendations for cavity wall or loft insulation in order to apply to DRHI, so factor in insulation costs if required.

You'll probably find that the DRHI covers the lion's share of the install costs (depending on property size, heat demand and system type), so it really boils down to how much more expensive a heat pump is to run, service and repair than a combi boiler.

It WILL be more expensive, so the questions are 'How much more?' and 'Is it worth it to get your Greta Thunberg merit badge?'

Quoting installers should be providing a calculation of electrical usage over the course of a year based on your EPC heat demand and pump spec, which you should then discuss with your energy provider to establish annual cost of running. But....check the installers 'math'  - ask them to demonstrate how they calculate it and where the figures came from on the system spec tables etc.

 MeMeMe 17 Feb 2021
In reply to Alkis:

The installer was fine with the electrics, it's nothing to do with the house electrics, it's a supply issue.

We just needed our electricity supplier to confirm they could provide the appropriate current but they declined to do so and said they wanted to upgrade the supply. Beyond that I don't know the details. It's probably somewhat of a distraction to the aim of this thread now!

In reply to Sealwife:

>  Few years back I looked into replacing my old oil boiler with ground source but was advised at that time that a modern condensing oil boiler would be more efficient

That assumes you're running it in the condensing temperature range. Otherwise it's not really much different to what you had before.

Girlymonkey, theoretically, the only way forward from a green perspective is electric heating because it's the only option not using fossil fuels. So, what you need to decide is the method of electric heating - output-wise it's either storage, panel, u/f or a mixture thereof, input-wise it's boiler, airsource heatpump, groundsource heatpump, or mixture thereof.

Pros/cons - heatpumps are only really efficient at low output temps, so you need a large heat emitter surface to extract that low temperature difference. U/f is ideal for heatpumps because it's a large emitter in a place where it doesn't take up room. It isn't very controllable though (taking days/hours to warm up and cool down) so you need to consider it as 'baseload' heating which you're prepared to top-up if necessary with direct heating (coal fire / woodburner / portable heater).  You can use online radiator requirement calculators such as this one https://www.theradiatorcompany.co.uk/heat-output-calculator to work out your heating requirement, but you need to look at the temperature delta specified and amend your calculations as necessary to find out the size of radiators required.  It may be that you simply don't have the space for the larger rads required to run a heatpump (or gas/oil condenser boiler) in it's optimum temperature range. If that's the case, then you can instantly eliminate things from your options.

Assuming you can have the requisite emitter size, then the choice between airsource or groundsource heatpump will depend on the amount of space in your garden for a shallow pipe or softness of rock for a deep pipe. Experience is key here as I know of someone who froze their garden and killed off all the plants because they extracted so much heat from the soil.

Once you have a quote / survey ask on your local facebook groups for personal experiences.  It's one thing having a theoretical solution, but you'll need to temper that with practicalities for people living in your area. For example, I'd love an electric boiler for green reasons and financial reasons (our 'mains' gas is imported butane/air mix and hyper expensive), but I know getting a suitably fat cable from my meter cupboard to the boiler location will be a massive ballache.  Good luck and let us know how you get on .

In reply to MeMeMe:

Sure, we're going off topic. It's just odd. Better not get an induction cooker if they reckon your supply cannot deal with an additional 32A current draw, though!

In reply to Toerag:

>  It isn't very controllable though (taking days/hours to warm up and cool down) so you need to consider it as 'baseload' heating which you're prepared to top-up if necessary with direct heating (coal fire / woodburner / portable heater).

That depends on the system. Low profile systems have a limited thermal mass and react pretty quickly. They are also the most suitable for a renovation/retrofit. Systems like mine do take a long time to heat up (although it's hours in my case, not days).

Post edited at 14:51
 MeMeMe 17 Feb 2021
In reply to Alkis:

We've already got one! 

Maybe that's the issue, by the time we add up the cooker and the car charger maybe the ASHP is going to tip us over...

In reply to Alkis:

> Just had a quick browse through several manufacturers' specs and the absolute max current seems to be around 30A, with a 32A fuse, so it doesn't really explain it. The installer must have really seen something that spooked them in the electrics.


30amps draw requires 10mm2 cable to guarantee it's safe to use in any installation method - cable clipped to an external wall with lots of space to lose heat into can handle more current than cable hidden in insulation for example.  If they knew it was a cable run which can lose heat and theoretically cope with 6mm cable there's still the voltage drop to consider if it's a long run.  I suspect they baulked at it because it will require a new 10mm cable running through places where it's a ball-ache to do so.

 girlymonkey 17 Feb 2021
In reply to Toerag:

Thanks, that is a very clear summary of it. Helps me to get a clearer picture of what we are looking at. 

 s kennedy 17 Feb 2021
In reply to girlymonkey:

I moved into a house with storage heaters in rural north of Scotland so not on mains gas. We did not even turn them on to see how expensive they would be to run. I briefly considered heat pumps, but was not convinced by the proposed benefits considering the house is timber suspended floors and not that well insulated. I ended up installing a wet system heated with a wood burner which was not eligible for funding. It fitted best with us and the layout of the house as did not want to give up space for wood chip/pellet burner. I acquire most of the wood I burn for free. 

I recently came across this discussion on Hydrogen Boilers, Heat Pumps & The Future of Heating which reinforced my decision. Very interesting discussion. 

https://www.youtube.com/watch?v=4uNKPDREa-Q&

If I was on gas with existing wet system I would have likely just improved insulation as and when it made sense, ripping everything out has an environmental cost too.

 girlymonkey 23 Feb 2021

In reply to logomaestro:

Thanks. I'm not sure that we have enough south facing roof space for solar, but worth doing some calculations.

Cooling is not an issue - we live in Scotland! 🤣😂

 Jamie Wakeham 23 Feb 2021
In reply to logomaestro:

Hmm.  A new poster, who it seems has joined a climbing forum solely to resurrect an effectively dead thread on a subject not at all connected with climbing, posting what seems to be generic blurb.  That doesn't look dodgy at all...

Post edited at 17:22
 Ben Bowering 23 Feb 2021
In reply to MeMeMe:

Are you sure your supply is 100A? The cut out may have 100A written/embossed on the outside but this only means that it is able to carry 100A fuses, not that it actually does. It could easily be 63A. 

In reply to girlymonkey:

Personally I'd go for one more gas boiler (just as I went for one more ICE car) as the technologies will be a lot more mature in 5-10 years.

I'm almost certain the next time I buy a car it will be at the very least a hybrid and possibly pure electric, and that the next heating appliance I buy won't be a gas boiler.

Post edited at 23:00
In reply to MeMeMe:

> Maybe that's the issue, by the time we add up the cooker and the car charger maybe the ASHP is going to tip us over...

Don't forget that you can apply "diversity" - you don't need a supply that adds up to everything you could possibly have on in the whole house, just everything you're likely to use at once plus a bit.  There are formulae to calculate it, or if it's too complex ask a sparky.

Simplest example of this is that your socket ring is on a 32A breaker, but if you add up the number of sockets and multiply by 13 you'll note that the number you get is rather higher than 32.

Post edited at 22:58

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