Ground source and woodburners

[lou]

We have just had the most impenetrable quote for ground source heating which looks like it might cost somewhere in the region of either £16k or £25k both of which, for a smallish farmhouse seem a little excessive. Added to which, the quote appears to say, (though I could be wrong here) that we would need to back up with a gas or oil boiler. We have an ancient rayburn that we were planning to overhaul which seems to be able to pump water around (obviously I'm not very expert at this!) and had also anticipated having a wood/coal burner. Can anyone give me the benefit of their knowledge and/or experience in using and/or combining alternative energy sources please? We are in Monmouthshire so if anyone knows of a good supplier within say 30 miles - who can quote in English - I'd be very grateful.

 

[MdB]

Our ground source heat pump system including pipe work in the garden, heat pump, pipe fluid, underfloor heating system and mini digger hire cost us £6.5k less £1.2k that the government gave us back for a total of £5.3k. However this didn't include any of the installation costs which we did ourselves - hard work but not difficult.

We got ours from Kensa Engineering (http://www.kensaengineering.com/) who are local to us but not anybody else. They are worth a call though as they have local reps I think. There is a lot of useful stuff on their website too.

Heat pumps are poor with radiators, underfloor is much better and they need a house that is well insulated. This is due to the low(ish) temperatures that they output (+35 deg C ish) so require a large surface area such as the floor to radiate from. With a poorly insulated house, there isn't enough to get the house to a good temperature.

They are also not great for heating upstairs as the underfloor solutions are not ideal. We currently have none and rely on heat rising from downstairs. When we get the back of the house insulated properly, this hopefully should be enough.

With a suitable mixer valve and a secondary pump, I see no reason why you couldn't plumb a second heat source into an underfloor system together with a heat pump. I'm not an expert in this however. Kensa or the underfloor pipe manufactures would know.

We are very happy with our system. Our total electricity bill for the last two months was £50 per month. This includes all our heating, hotwater and everything else as we are completely electric. We believe the yearly cost of running the heating will be in the £300 to £350 bracket which isn't bad for a four bed house especially as there aren't servicing costs either.

 

[DaveBrigg]

Air source heat pumps are also available; we have friends in a house with modern standards of insulation who use one in their loft to run the central heating.

 

[worms]

I've a sense of deja vu here of being roundly condemned for the suggestion, but I think I would look at an accumulator/heat store tank and feed the ground-source and the Rayburn both into it. My wish-list for a long-term solution to my heating is a modern wood boiler and heat-store in the garage, supplemented (in summer) by solar panels on the garage roof and (in winter) by the Rayburn in the kitchen.

 

[Jon Maine]

You don't need a gas boiler as back up necessarily, If you are having wood burners you can introduce a thermal store which will sink heat from both sources prioritising the cheaper way to heat as the preferable source. Underfloor heating is best as Mdb says however I disagree about it being inefficient. There are lots of mediocre systems we installed an Osma system which works well. If your floor joists are strong enough or can be strengthened a 2" mortar screed tight under floorboards on top of insulation works well too.
We have 2 heat pumps running on boreholes from Ice Energy, Total cost for a 9kw and a 6 kw with 313m of borehole ( inc a water well) was £20k self install which we got £3k back from N-Power by way of grant through Ice Energy.
We have not got a thermal store but do have wood burners to heat in conjunction, i.e. the wood burners run the heat pump thermostat cuts it out more.
We have tuned the system a bit more now but it took around 100kw per square metre to heat the house and produce hot water.
In an older building when exceptionally cold certain areas may struggle to get warm enough with a heat pump which is why we supplement with wood burners.
If you wanted to come and see it working you would be welcome

 

[Jon Maine]

I've a sense of deja vu here of being roundly condemned for the suggestion, but I think I would look at an accumulator/heat store tank and feed the ground-source and the Rayburn both into it. My wish-list for a long-term solution to my heating is a modern wood boiler and heat-store in the garage, supplemented (in summer) by solar panels on the garage roof and (in winter) by the Rayburn in the kitchen.

Thats what I just wrote at the same time you did!!

 

[MdB]

Underfloor heating is best as Mdb says however I disagree about it being inefficient. There are lots of mediocre systems we installed an Osma system which works well. If your floor joists are strong enough or can be strengthened a 2" mortar screed tight under floorboards on top of insulation works well too.

Efficiency isn't quite the right word. Heat transfer per unit area is a bit more like it. Underfloor with a low return temperature means that there isn't a big differential between the floor temperature and the room temperature to give a good heat flow. Heat pumps operate most efficiently with a low return temperature which is the opposite of an oil / gas boiler.

Underfloor for upstairs requires a heat store if you are going to run off cheap electric which is often not possible and it is much more expensive than pipes in the screed downstairs.

 

[Jon Maine]

Underfloor heating is best as Mdb says however I disagree about it being inefficient. There are lots of mediocre systems we installed an Osma system which works well. If your floor joists are strong enough or can be strengthened a 2" mortar screed tight under floorboards on top of insulation works well too.

Efficiency isn't quite the right word. Heat transfer per unit area is a bit more like it. Underfloor with a low return temperature means that there isn't a big differential between the floor temperature and the room temperature to give a good heat flow. Heat pumps operate most efficiently with a low return temperature which is the opposite of an oil / gas boiler.

Underfloor for upstairs requires a heat store if you are going to run off cheap electric which is often not possible and it is much more expensive than pipes in the screed downstairs.

So the mortar screed is best upstairs then? That stores heat well.

We have had good results with our Osma system, but it does not store the heat well it certainly heats the room and there normally seems to be a reasonable difference between flow and return, although the computer manages this and as soon as the return starts to get to warm shuts it down.

We are not on economy 7 or similar, which if you had thermal store everywhere would mean you could utilise most of your daily heat by topping the screed up at night. Our system is responsive to the thermostats both inside and out and on the return to calculate what temperature is required.

 

[MdB]

Yes the screed floor would be best if you want to use the cheap electric as it would act as a large heat store. Without it, the room would heat quickly when the system was on and cool when the system was off. Alternatively, you can use a heat store tank as you suggest.

Anybody with a heat pump (or electric night storage) running on Economy 7 should have a careful look at Economy 10. Prices are similar to E7 but you get 10 hours of cheap electricity and more importantly you get 3 hrs during the afternoon and 2 hrs in the evening which allows you to give the house a boost at those times.

 

[FamilyWiggs]

We have tuned the system a bit more now but it took around 100kw per square metre to heat the house and produce hot water.

:shock: Do you mean 100w per sq.m? Or is that an annual total?

 

[Jon Maine]

We have tuned the system a bit more now but it took around 100kw per square metre to heat the house and produce hot water.

:shock: Do you mean 100w per sq.m? Or is that an annual total?

100kw annually although that should come down this next year as we have started to fine tune the system.

 

[Cloudscape]

I've been trying to work out which model of Rayburn that is... a No 3? A Royal with a single lid?

http://www.rayburn-web.co.uk/raytech/ident/ident2.htm

Info is still available for all models to tell you what they are capable of. My Royal makes hot water all day, but the specs say it could only heat a towel rail in addition to the water. You might be able to integrate yours in some way.

 

[lou]

OK, thanks.. very useful when I have digested it all! I do want to have underfloor heating but flags are laid on earth and JoceAndChris (or one of them anyway) said this was a SPAB-related crime. And I'm still trying to find out if it's actually possible to put UFH directly between the earth and flags. SPAB told me that my house won the record for nil energy performance - there's absolutely nothing there at the moment and you can see sky through the holes in the ceiling and the slates. There are some very old floorboards in some upstairs rooms that will probably have to be taken up, if only to have a nose around, and we will insulate between the downstairs ceiling and upstairs boards, and we'll do the roof when it's replaced. So sounds like ground source is a go-er and Jon, may take you up on your offer of a visit.

And, MdB, thanks for useful contact but the secondary boiler you refer to, is that a smaller, or different type?

I don't know anything about accumulator/heat stores but will google. I did think about getting a consultation from the Alternative Technology Centre in mid-Wales but was worried that they might tear me off a strip for occasionally putting form before function/the future of the planet.

The pic shows the general outside state of the building.

 

[Flyfisher]

And I'm still trying to find out if it's actually possible to put UFH directly between the earth and flags.

It's certainly possible there's not much point as you'll lose most of the heat trying to warm up the earth. The basic idea is to put a well-insulated layer below the UFH piping so that the only way for the heat to go is through the flooring and into the house. Anything else would be a waste of time, money and energy.

But that's only the theory; there are others on here that can explain far better from first-hand experience.

 

[Jon Maine]

And I'm still trying to find out if it's actually possible to put UFH directly between the earth and flags.

It's certainly possible there's not much point as you'll lose most of the heat trying to warm up the earth. The basic idea is to put a well-insulated layer below the UFH piping so that the only way for the heat to go is through the flooring and into the house. Anything else would be a waste of time, money and energy.

But that's only the theory; there are others on here that can explain far better from first-hand experience.

I agree, if you do this you need insulation. Ideally a leca/limecrete floor would be good.

 

[MdB]

Option 1: - compacted gravel - 150mm concrete - dpm - 100mm celotex - underfloor pipes - 75mm screed - flagstones

Option 2: - compacted leca - 300mm(??) insulated limecrete, underfloor pipes - 100mm(??) limecrete - flagstones.

Both options give you a nice heated floor and keeps your flagstones (which I would love).

I found out recently that our house would have likely had a sand floor in years past which I hadn't heard of before. Has anybody else heard of this?

 

[JoceAndChris]

OK, thanks.. very useful when I have digested it all! I do want to have underfloor heating but flags are laid on earth and JoceAndChris (or one of them anyway) said this was a SPAB-related crime.

Good Lord don't take what I say too seriously. Have PM'd you.

 

[Inspector John]

Has anyone seen these masonry heaters http://www.mha-net.org/
I'm thinking of building one

 

[Jon Maine]

Has anyone seen these masonry heaters http://www.mha-net.org/
I'm thinking of building one

Well not exactly like that but yes I is a sound principle which works.

We have a large Inglenook with an Esse range in it which heats the surrounding masonry to approaching 40 degrees C so this radiates for some hours after the fire has gone out.

Dont forget to build in a bread/pizza oven too. When its finished we can come and try a Pizza with you!!

 

[MdB]

I've not come across those before. I guess they would be a pain to get going when the chimney was cold but otherwise they look like a neat idea.