LPG (until Mains gas available) or Oil?

[JohnW]

Hi All
We're at the stage where we need to make a final decision about our Heating & Hot water system and we would really appreciate some advice.

 

We're building a 230 sq metre, 2 storey house (GF 120, FF 110) in Co. Down, Northern Ireland...

• Family of 2 adults, 2 teenage boys (long showers, most days)
• Work/school means the house is unoccupied for a large part of the day
• Block built full-fill 150mm cavity walls
• Triple glazed windows throughout
• Mechanical ventilation with heat recovery
• Underfloor heating on the ground floor and radiators on the first floor
• Multi-fuel, back boiler stove
• Airtightness target of 1 m³/(m² h)

 

We will have a south facing pitched roof which is crying out for solar panels, but with no RHI in NI both solar thermal & photovoltaic are expensive options. My preference is PV panels and I plan to put all the wiring in place during the build and then at some point in the future add the panels.

 

Mains gas is on it's way to us but won't be available until at least 2 years after we finish the build. I'm working on the assumption that mains gas is the best option and therefore we should put something temporary in place and then switch to mains gas when it is available.

 

We've ruled out Air Source Heat Pump due to cost (we saved £11.5k when we removed it from our spec and replaced it with Oil).

 

I would really appreciate some guidance as my head is pickled thinking of each option and permutation.

 

My specific questions are;

1. With a reasonably airtight/insulated house we hopefully won't need too much energy. Therefore am I over-thinking the whole issue? (In which case Oil is probably the way we'll go)
2. Whichever fuel we decide on, what's the best way to use the energy provided by PV panels on those few days it actually is sunny in NI? 
3. We've been advised to let intelligent heating controls (Dataterm IHC) run the UFH, but as the house will be unoccupied for long periods is this not wasteful?
4. Anything else I should consider?

 

Thanks in advance

[ProDave]

Have you done a SAP assesment or otherwise calculated the maximum heap input requirement?  That is quite crucial to the outcome.

 

What size ASHP did you have specified that was going to cost £11.5K?  (mine cost just under £500 and I will be self installing it)

 

Are you SURE mains gas will arrive and what will the connection cost be?

 

I am not a fan of LPG for heating  Your 2 options are a bulk tank, or a bank of 47Kg cylinders on a changeover regulator. 

 

The bulk tank will have an install cost, and a removal cost, check also you are not tied into a long contract. Asking them what the cost of removal will be "should you wish to change fuel" may ring alarm bells with the supplier.

 

A bank of 47Kg cylinders is probably the short term solution, but the gas is more expensive. The only install cost is a changeover regulator and set of hoses, you can usually blag free cylinder hire as they know you will be a regular user (at least for 2 years)

 

Make sure you keep the mains gas jets for the boiler safe for the mains conversion later.

 

Re the PV, that dictates a hot water tank really (so not a combi boiler), but if having a stove with a back boiler as well you will be having a hot water tank (probably a thermal store) in any case.

[Nickfromwales]

16 minutes ago, JohnW said:

We've ruled out Air Source Heat Pump due to cost (we saved £11.5k when we removed it from our spec and replaced it with Oil).

 

Holy ?  

Was the ASHP 24 carat gold plated, and decorated with unicorn feathers?

I think you need a serious look again over this lot as you've obviously been given some duff info here. 

Seems an ASHP would be much cheaper for space heating and DHW preheat, 

Scrap the "intelligent heating controls" and put that money towards PV. 

Why the multifuel stove? If you want a stove then just have a gas ( LPG ) / electric dial fuel stove / range. That would save a lot of cost and complexity IMO, so more £££'s to go towards the PV . 

Do you have any quotes or designs you can upload ? Please remove any sensitive information first  

My 2 cents:-

ASHP. 

HP UVC.  

Buffer tank and DHW pre heat. Preheat optional as you can live without it. Down to available plant room space for the two cylinders. 

PV into both / and ASHP to reinforce ( reduce ) grid consumption. 

LPG cooking if you don't like electric. 

Job done and cheap as chips to run. 

 

[Guest Alphonsox]

We went through the same considerations with our Co Down build a couple of years ago.  At the time LPG was prohibitively expensive in NI  (I doubt that has changed ) so I would only consider this as a short term option if you were certain that Natural Gas was going to turn up. I guess the plus point is that the conversion from LPG to NG will be a relatively simple switch.

As a potential stopgap until the NG arrives how about heating the whole place plus DHW with electricity on E7. It will be more expensive than oil to run but would be very cheap to install.

 

The PV market in NI is dysfunctional at the moment, like you I have wiring in place to make use of if sanity breaks out at any point in the future.

[dpmiller]

Never mind the nay-sayers, @JohnW what stove were you thinking of, and have you had any discussion with the BCO about it's install ref MVHR?

[PeterW]

41 minutes ago, dpmiller said:

Never mind the nay-sayers, @JohnW what stove were you thinking of, and have you had any discussion with the BCO about it's install ref MVHR?

 

I had that discussion with mine - and the stove fitter - as we only have a 4.5Kw stove but the only “feed” is the MVHR. Had a long chat as neither can decide what the “correct” stance is as we aren’t at passive house air tightness but the imbalance is negligible ...

 

So we have no fresh air feed but will see what happens with MVHR balancing ..! Do we balance with the stove lit and then without .....??

[Tom]

I might jump in here with my two penneth: pretty sure you'll need an isolated air supply for your stove. It's been discussed on the board before and the general consensus is that it will wreak havoc with your MVHR. A vented stove would keep you airtight too.

[ProDave]

From a building regs point of view you only need an air in provision for a stove of 5KW or more.

 

For use with mvhr I would still get one that has ducted air in straight to the stove so it does not draw air from the room.

[dpmiller]

One local vendor was refusing to supply a direct air stove to me, citing that only a DIBt- certified unit would suffice in a dwelling with MVHR. Scaremongering...

[JohnW]

7 hours ago, ProDave said:

Have you done a SAP assesment or otherwise calculated the maximum heap input requirement?  That is quite crucial to the outcome.

 

What size ASHP did you have specified that was going to cost £11.5K?  (mine cost just under £500 and I will be self installing it)

 

Are you SURE mains gas will arrive and what will the connection cost be?

 

I am not a fan of LPG for heating  Your 2 options are a bulk tank, or a bank of 47Kg cylinders on a changeover regulator. 

 

The bulk tank will have an install cost, and a removal cost, check also you are not tied into a long contract. Asking them what the cost of removal will be "should you wish to change fuel" may ring alarm bells with the supplier.

 

A bank of 47Kg cylinders is probably the short term solution, but the gas is more expensive. The only install cost is a changeover regulator and set of hoses, you can usually blag free cylinder hire as they know you will be a regular user (at least for 2 years)

 

Make sure you keep the mains gas jets for the boiler safe for the mains conversion later.

 

Re the PV, that dictates a hot water tank really (so not a combi boiler), but if having a stove with a back boiler as well you will be having a hot water tank (probably a thermal store) in any case.

Thanks @ProDavewe have a as-designed SAP report, but unfortunately it is based on our spec before it was trimmed due to budget.

The SAP report was based on a 200mm cavity, 140mm inner skin (u-value 0.15) & ASHP, these have been reduced to 150mm cavity, 100mm inner skin (u-value 0.19) & Oil fired boiler, so I'm not sure it still applies.

 

We didn't size the ASHP, that was up to the builder/plumber, but I suspect it was deliberately priced very high, because they are not familiar with the setup and would prefer to install what they are used to installing, i.e. Oil.

 

Yes, mains gas will definitely arrive but you make a very valid point about cost of connection. The gas company will prioritise higher populated areas and therefore I suspect it might be 4 or 5 years before they are coming passed our site which is on the outskirts of town. Therefore it would be very expensive to get them to track to our site before the other areas.

 

Calor Gas are currently offering either a "free" boiler or £500 towards the boiler of our choice, which would involve a 24moth tie-in period. This has made me consider LPG as an option as I was hoping mains gas would be available by the end of the 24months.

 

Thanks for the pointer about no combi boiler if we're using PV - this is the sort of thing I need to know, thank you.

 

 

 

 

Edited March 11, 2018 by JohnW

[JohnW]

5 hours ago, Nickfromwales said:

Holy ?  

Was the ASHP 24 carat gold plated, and decorated with unicorn feathers?

I think you need a serious look again over this lot as you've obviously been given some duff info here. 

Seems an ASHP would be much cheaper for space heating and DHW preheat, 

Scrap the "intelligent heating controls" and put that money towards PV. 

Why the multifuel stove? If you want a stove then just have a gas ( LPG ) / electric dial fuel stove / range. That would save a lot of cost and complexity IMO, so more £££'s to go towards the PV . 

Do you have any quotes or designs you can upload ? Please remove any sensitive information first  

My 2 cents:-

ASHP. 

HP UVC.  

Buffer tank and DHW pre heat. Preheat optional as you can live without it. Down to available plant room space for the two cylinders. 

PV into both / and ASHP to reinforce ( reduce ) grid consumption. 

LPG cooking if you don't like electric. 

Job done and cheap as chips to run. 

 

Thanks @Nickfromwales

Yes, Holy ? indeed, that's exactly what I said when I saw the quote!

I suspect the builder asked their usual plumber to price it and I don't think they are familiar with ASHPs as almost all houses in the area are Oil. Therefore and I'm guessing here, but I think the price was inflated to cover all eventualities to the point were it was too expensive for us.

 

We like a fire in the living room, hence the stove and if we're having a stove we thought it might as well heat the water while it's at it. It will be a room sealed stove with it's own external air supply. It sounds like the back-boiler complicates the plumbing somewhat, hmmmm . It'll be a hard sell to my better half to try to remove the back-boiler.

 

Unfortunately I don't have any quotes or designs, we had originally spec-ed ASHP and when the first price for the build came back we had to find areas for reduction, so we changed to Oil and were shocked at the reduction of £11.5k but it was also very welcome - double edged sword. 

 

Would you have any designs you could share for a similar setup to the one you mentioned above, i.e. ASHP/HP UVC/Buffer tank & DHW pre-heat etc...?

 

No great love of cooking with gas, the only reason I'm entertaining LPG is because I assume it would be cheaper to convert from it to mains gas when available.

[JohnW]

5 hours ago, Alphonsox said:

We went through the same considerations with our Co Down build a couple of years ago.  At the time LPG was prohibitively expensive in NI  (I doubt that has changed ) so I would only consider this as a short term option if you were certain that Natural Gas was going to turn up. I guess the plus point is that the conversion from LPG to NG will be a relatively simple switch.

As a potential stopgap until the NG arrives how about heating the whole place plus DHW with electricity on E7. It will be more expensive than oil to run but would be very cheap to install.

 

The PV market in NI is dysfunctional at the moment, like you I have wiring in place to make use of if sanity breaks out at any point in the future.

Thanks @Alphonsox, good to know someone else has been through the same dilemma and has come out the other side.

 

Economy 7 heating, an idea I hadn't thought of - I used to live in a house in Portsmouth years ago with the old economy 7 storage heaters and I thought I'd seen the last of them!!

 

Have you installed an ASHP at your build? If so, I would be very interested in having a chat about your experience and maybe even get a referral for someone who could give me an install-price that I could live with.

 

PV is very much on the long-finger.

[JohnW]

3 hours ago, dpmiller said:

Never mind the nay-sayers, @JohnW what stove were you thinking of, and have you had any discussion with the BCO about it's install ref MVHR?

Thanks @dpmiller,

I'm aware that the stove needs to be room sealed and have it's own air feed - the model we're currently looking at is the Stovax View 8HB.

[JohnW]

3 hours ago, PeterW said:

 

I had that discussion with mine - and the stove fitter - as we only have a 4.5Kw stove but the only “feed” is the MVHR. Had a long chat as neither can decide what the “correct” stance is as we aren’t at passive house air tightness but the imbalance is negligible ...

 

So we have no fresh air feed but will see what happens with MVHR balancing ..! Do we balance with the stove lit and then without .....??

Thanks @PeterW

We've specified a dedicated air feed for the stove in our plans, so hopefully it won't impact the MVHR

[JohnW]

2 hours ago, Tom said:

I might jump in here with my two penneth: pretty sure you'll need an isolated air supply for your stove. It's been discussed on the board before and the general consensus is that it will wreak havoc with your MVHR. A vented stove would keep you airtight too.

Thanks @Tom

We're planning to have a dedicated air supply for the stove.

[JohnW]

2 hours ago, ProDave said:

From a building regs point of view you only need an air in provision for a stove of 5KW or more.

 

For use with mvhr I would still get one that has ducted air in straight to the stove so it does not draw air from the room.

Thanks @ProDave

Dedicated air supply will be used, so hopefully won't impact MVHR

[JohnW]

6 hours ago, Nickfromwales said:

Scrap the "intelligent heating controls" and put that money towards PV. 

If I scrap the "intelligent heating controls" what's the best way to operate the UFH whether it's on Oil or ASHP? 

[JohnW]

Ok, the more I think about it, we really should revisit our original plan and get a second opinion on price to install an ASHP.

 

Before I approach anyone for a price, I'd like to fully understand what the differences are between the plumbing requirements for ASHP and Oil. I had assumed the only differences were the heat source and that the rest of the plumbing system was pretty much the same in both cases. Can any of you set me straight please?

[Guest Alphonsox]

To be honest I couldn't fine a reasonably priced ASHP installer in NI when I looked, I'm sure they're out there somewhere. My intention is/was to self install an ASHP system at some point. I was extremely lucky to acquire a couple of Kingspan units for a very low price when they got out of the market - They're currently at the back of a friends shed awaiting installation.

Our build is close to Passive spec with UFH downstairs currently fed from a 3kw immersion heater run from E7. The slab acts as a very big storage heater, warming up overnight and cooling slowly during the day. Over the last few weeks we have had to top this up in the evening  but overall E7 has largely been a very successful heating mechanism.

That being said - if we had had the option of natural gas then we would have used it. You're welcome to drop in and have a look around, PM me if interested.

[dpmiller]

How many kW do you require, @JohnW?

[Declan52]

18 minutes ago, Alphonsox said:

To be honest I couldn't fine a reasonably priced ASHP installer in NI when I looked, I'm sure they're out there somewhere. 

I was all set for an ashp but we went to maybe 2-3 of the self build shows in Belfast and spoke to every one there who done them and every single one told you something different. Knowing what I know now about them they where all just winging it to an extent. 

Withthe rhi scheme dead here there is hardly anyone out there left that does do them.

I would put the money towards PV and use an E7 style setup until such times that gas is available. Put all the pipe work in so it just needs a gas boiler put in and connected up when the time comes.Even here we get enough from the PV for my hot water needs for maybe 6 months of the year. 

[JohnW]

16 minutes ago, dpmiller said:

How many kW do you require, @JohnW?

According to the as-designed SAP report... (which uses 0.15 U-value for external walls, which will actually be closer to 0.19 now we've changed the spec)

 

DHW - 2500 kWh/year

Space Heating - 5200 kWh/year

 

[JohnW]

38 minutes ago, Alphonsox said:

You're welcome to drop in and have a look around, PM me if interested.

PM sent - Thanks

[JohnW]

13 minutes ago, Declan52 said:

I was all set for an ashp but we went to maybe 2-3 of the self build shows in Belfast and spoke to every one there who done them and every single one told you something different. Knowing what I know now about them they where all just winging it to an extent. 

Withthe rhi scheme dead here there is hardly anyone out there left that does do them.

I would put the money towards PV and use an E7 style setup until such times that gas is available. Put all the pipe work in so it just needs a gas boiler put in and connected up when the time comes.Even here we get enough from the PV for my hot water needs for maybe 6 months of the year. 

Thanks @Declan52 How do you use your PV, is it connected to an immersion heater?

[Declan52]

Yeah any that would normally be sold back to the grid is used to heat the water. The device is one of these.

https://www.marlec.co.uk/product/solar-iboost/?v=79cba1185463

 

Last year I got near £480 for the amount I generated plus £65 for the excess I sold back. Not sure how I would calculate the amount it saved me by heating the water. As the tariffs have all changed you would get less though.