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Author Topic: GSHP RHI - newbie advice needed!  (Read 38071 times)
europa
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« on: April 09, 2015, 01:53:58 PM »

Hello all.

I am about to purchase a three-bed semi-detached house, where i will be doing a complete renovation, including loft conversion and, possibly, side/rear extension. I am planning on (extrernally) insulating the solid walls and installing underfloor heating throughout. I have a current EPC which recommends 270mm loft insulation and solid wall insulation. Cavity wall N/A. Essentially i am after some advice wrt the RHI and GSHP installation.

My understanding is that only the 270mm loft insulation is relevant for the RHI (as there are no cavity walls in this case).

- Can i have the GDAR done whilst works are still ongoing?
- If so, given that the RHI payments are based on the heat demand, should i get a GDAR prior to insulating the walls (to avoid reducing the heat demand and payments)?
- I know the SPF is a big factor in the payments, and i am keen to avoid the 'worst room' scenario. Might that still be an issue if i installed underfloor heating throughout? Also, am i correct in assuming i should get the SPF assessment done at the end of the works (so as to maximise it)?
- If i decide to leave the extension till later, say in a year or two's time, would that affect the SPF/payments in any way?

Any other tips/considerations much appreciated!

Thanks in advance.
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dhaslam
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« Reply #1 on: April 10, 2015, 01:20:12 AM »

Without going into  the  details of regulations  there is  a financial issues involved.   If you  set up a system that needs  greater capacity  than the long term need  it is going to mean extra investment that would be better spent on  insulation initially.       
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europa
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« Reply #2 on: April 10, 2015, 09:38:28 AM »

Thanks, but i don't really understand what you mean.
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Ted
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« Reply #3 on: April 10, 2015, 10:08:17 AM »

If your property is poorly insulated then the larger (and more costly) a GSHP system you will be required to install. This will get you more money back under the RHI (eventually) but you may be better off by paying for insulation first and then installing a smaller (and less costly) GSHP. You might be able to get an installer to give you two quotes in order to compare the net returns.
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JonG
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« Reply #4 on: April 10, 2015, 10:15:43 AM »

EPC ASAP.
Then insulate
Then get correct size HP
Max RHI min installed cost min run cost
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Ted
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« Reply #5 on: April 10, 2015, 11:00:09 AM »

Those in the RHI scheme have an ongoing obligation to inform OFGEM of any changes in circumstances that may affect their payments. This, I interpret, would include making changes to the level of insulation that the EPC (and therefore the deemed heat value) was based on. Failing to make such a notification could amount to fraud.
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brackwell
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« Reply #6 on: April 10, 2015, 11:32:46 AM »

Just to clarify that in order to claim RHI you have to achieve a min level of efficiency in the total system and that to get any decent return you need to achieve an efficiency which is not cheap and easy bearing in mind that it has to be achieved in virtually all the rooms  as it is the worst room that dictates the efficiency/RhI  for the whole house.

Ie you can spend a lot of money and get a big return or smaller amount and get smaller return. 6 of one ....

Much more logical to do as above have suggested.

Ken
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JonG
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« Reply #7 on: April 10, 2015, 12:06:51 PM »

I specifically asked Patrick Allcorn about this point at the launch a year ago and he completely endorsed it on the basis that for the government it was the best possible result. I.e more units of renewable energy sold and improved stock.
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skyewright
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« Reply #8 on: April 10, 2015, 05:51:54 PM »

Surely it must be the case that the heating system has to be designed to be capable of providing for the heat demand stated in the EPC (and thus the basis for the RHI calcs)? Anything else would be a nonsense (okay, so that's not impossible when it comes to government schemes...)

Our EPC/GDA reckon just short of 17,000kWh/annum. We are currently "all electric" and our electricity meter (we have a separate one for heating, both space & DHW) reckons just over 6,500kWh/annum. This discrepancy is probably one of the main factors that means we'll not be taking the GSHP/RHI route. We haven't quite decided yet, but the way things look at present the quotes don't make sense from either an economic point of view (it would take around 15 years to 'pay off' the difference between the quotes & the RHI funding from savings in electricity cost[1]) or a CO2 one (we could have a much bigger CO2 impact by making alternative use of the the difference between the quotes & the RHI funding).

If someone was going to pay us based on the EPC heat demand for a system designed to meet our known heat demand the figures might be very different, but I'm not expecting that to happen.

[1] Assuming 6,500kWh/annum heat energy, powered by electricity factored by the SPF, and allowing for 10% energy inflation.
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Regards
David
3.91kWp PV  (17 x Moser Baer 230 and Aurora PVI-3.6-OUTD-S-UK), slope 40, WSW, Lat 57 9' (Isle of Skye)
europa
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« Reply #9 on: April 10, 2015, 07:49:56 PM »

Thanks; it seems a lot more complicated than i thought!

I called the RHI application helpline and it confirmed there is no problem with insulating after the GDAR/EPC (to maximise RHI). However, reading between the lines, are you guys implying the GSHP may not be worth it anyway? Up until now, i have simply been going by the 'typical' payments listed on other sites such as which.co.uk (which seem to imply a repayment time of roughly five years, which, to me, is a no-brainer).
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skyewright
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« Reply #10 on: April 10, 2015, 09:49:35 PM »

Up until now, i have simply been going by the 'typical' payments listed on other sites such as which.co.uk (which seem to imply a repayment time of roughly five years, which, to me, is a no-brainer).
Don't necessarily take my case as typical.

a) I think our EPC heat demand is a bit weird[1].
b) Local ground conditions mean the ground works quote is much higher than it might be elsewhere.

You need to do you own analysis on you own figures & make up you own mind.

That aside the economics you mention seem odd. Since you get RHI payments for 7 years, to have it "paid off" in 5 sounds like getting more in RHI than the cost of the system. I know that happens with FITs (we are on course to cover costs in 8-10 years), but does it happen with domestic RHI?


[1] We have 2 large (unheated) conservatory/sunspaces. So far as I can tell the EPC seems to think all they do is make those walls sheltered. Our experience is that they do far more than that, acting both as "insulation" and as sources of significant solar gain (Though no where near 10,000kWh/annum worth!).
« Last Edit: April 10, 2015, 09:57:55 PM by skyewright » Logged

Regards
David
3.91kWp PV  (17 x Moser Baer 230 and Aurora PVI-3.6-OUTD-S-UK), slope 40, WSW, Lat 57 9' (Isle of Skye)
europa
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« Reply #11 on: April 11, 2015, 08:37:07 AM »

http://www.which.co.uk/energy/creating-an-energy-saving-home/guides/renewable-heat-incentive-rhi-explained/rhi-costs-and-earnings/

This implies the cost of GSHP installation to be between 11 & 15k. My house will be a 4-bed semi, so it looks like i should get at least 20k back over seven years. So, yes, my understanding is that Domestic RHI should more than pay for the GSHP installation. If that is incorrect, then i would definitely reconsider.
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brackwell
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« Reply #12 on: April 11, 2015, 09:09:16 AM »

" so it looks like i should get at least 20k back over seven years." How do you get to this fig.

Also does the installation cost include the internal house costs that you will need to achieve the SPF you are assuming?  Bearing in mind you have to achieve this in all rooms. Your personal living habits and the EPC having nothing to do with it as it is all based on calculations by the the MCS approved installer regarding heat requirement and size of emitters.

Focusing on the money leads to tail wagging dog. Why game the system by spending considerable extra money in the beginning on equipment you will not be needing.

Also after the 7 yrs where are you. You will have to have gone the insulation any way or put up with larger bills.
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brackwell
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« Reply #13 on: April 11, 2015, 10:13:24 AM »

Now found this   http://www.refrigeration-engineer.com/forums/showthread.php?43843-Domestic-RHI-heat-demand-calcs-EPC-vs-MCS&s=96405056db229c56b56005022b546881

My understanding is that the first paragraph is wrong. Anyone agree.

Ken
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Ivan
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« Reply #14 on: April 11, 2015, 06:06:39 PM »

I think the first paragraph is correct: 1)The RHI payments are calculated from the EPC (so they need to get an EPC done - assuming they haven't already got one. If they have already got one, then they should not need to get another one EXCEPT if it's one of the old style ones that isn't on the government database 2)The room-by-room heatloss calculation is not the basis for the RHI payments (instead, this is required for correctly sizing the heatpump to the house).

The room-by-room heatloss calculation does however have some bearing on the RHI payments for heatpumps - it's used to classify the heat emitter efficiency (ie to calculate the penalty factor for not having insufficient area of heat-emitter.)


The heatloss calculation could be much better than the EPC, if insulation/improvements have been done on the house since the EPC was calculated. So you could have an example where the EPC calculates a high RHI payment, and the heatloss calculation demonstrates a smaller heatpump is required.


In my view, a GSHP is a good idea, as long as you have oversized radiators. From an RHI point of view you really want underfloor heating or 4.3x oversized radiators IN EVERY ROOM. As long as you are not using vertical ground loops (very expensive), then it's generally going to have a reasonable pay-back period with RHI. Navitron is selling MCS-certified GSHPs incidentally, but due to long delays in getting new things onto the website, it's not listed online yet. Give Navitron a call if you're interested in purchasing, or if you need an installer. These are the GSHPs that Navitron is selling: http://www.viessmann.co.uk/content/dam/internet_uk/literature_new_website/groundsource_heatpumps16ppweb.pdf
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