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Author Topic: Complete House System Advice  (Read 1406 times)
Bikerzz
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« on: October 21, 2019, 07:42:19 AM »

Hi All

Ive been on here a while and really enjoy reading what you guys/girls have managed etc.... Ive finally got to the stage where I need to take the plunge and decide what Im going to ask a plumber to do (I word it like that deliberately as many of you have said in the past, TELL the plumber what you want and take their advice with a pinch of salt as they will do whatever is easiest and suits them).

2 Story home (planning doing a loft conversion in future), 1967 built, Off mains Gas lines, 240m2 (over 2 floors), 50mm CWI filled, Triple Glazed, 200mm Loft Insulation. Oil system, 2 cold tanks in loft, HW in cupboard upstairs. TINY rads
Currently use 500 electric a year and about 1000L oil (not bad at all really). Typical 30s couple working during day, although both do work from home prob 1 day a week each on average. Plan to live here for 30 years. I have 0.5Acre but not suitable for ground source.

I have the UFH going in next month, Block and beam, 50-80mm Celotex, 50mm liquid screed with 16mm pipes. Yes whole ground floor renovation (re-wiring). Whole downstairs will be tiled bar living room which will have a carpet, all rads downstairs out. Oil boiler is on its last legs and not sure when it goes I should replace it or not going forward?
I would like a Unvented cylinder in new kitchen for these reasons : Space do do staircase for loft conversion next year, removing HW tank and the 2 cold water tanks from loft. I can stick 1 or 2 Immersuns in the tank to run off spare solar (no solar yet).
I could look at a ASHP to run just the UFH?
Rads upstairs need changing next year, so will go large decorative ones as already have the cost to change anyway if run these off ASHP?
Its now a 4 bed house (with 4 bathrooms), lost conversion would be games room for me/children, so no extra bathrooms planned.

Do I put a unvented cylinder in? The current one is original and should prob be changed at some point, various leaks bodged in the past. New kitchen Utility going in and have planned space for it with ease. No idea on mains pressure (although 1 of the power showers does have high pressure at it and causes the "whine"), but I heard this can be overcome with a extra pump fitted if needed.

Where do I plumb the UFH into? A unvented cylinder to act as a buffer/free heat from solar? Not sure about short cycling a very old oil boiler to UFH that doesnt need 70c water.
Do I look at plumbing in a ASHP now for just UFH? Or put it into a Unvented cylinder (like a TS).

Sorry this is very messy wording and I know you guys will have plenty of questions, however I need to plan this now while the house is stripped, Im happy to spend the money now and get it right, Im not stripping house later on when we might have little ones. I d seem to spend sod all on oil really so maybe I dont need to invest in renewables so much..... although prices will only be going one way for oil and reluctant to put a new oil boiler in when this one goes wrong.  Happy to plan to keep oil boiler and when it goes wrong just swap that for a ASHP, but want all the pipes roughly in now and wiring.

Cheers
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TT
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« Reply #1 on: October 21, 2019, 08:39:35 AM »

i would like to thin a house this size would benefit from a small plant room.

It would enable plumbing and electrical, network cabling, etc, etc. to be altered, repaired, serviced with minimal inconvenience to the rest of the house

 would have manifold s for cold water distribution,, hot water distribution with individual isolating valves and the same for the heating circuit
i  would try and have a cupboard  above the plant room to enable pipes/cable to get into this floor and the loft space- a riser in commercial speak.

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brackwell
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« Reply #2 on: October 21, 2019, 02:19:33 PM »

Good to see a posting with a lot of detail.

So your electricity at c 2700kwh looks quite economical but your oil at c 10,000kwh is the one that you may be able to reduce in view of all your insulation.

 I trust you do not have any open fire chimneys

You oil boiler if original has a pilot light? and not a balanced flue ? and if not then you have a big enough draft to feed it ? - oh dear.

You do not say where you live but obviously that can have considerable bearing on your heating demand. Do you have a EPC

Now is probably the best time to replace your tank particularly if you lived in a hard water area. Take a look at pipe runs to keep them short and maybe put extra more direct runs in 16mm plastic instead of 22mm copper if thats what you have.

I am not sure what your objective is, to be more green. to save money or perhaps both.

I am always uneasy about these mix and match systems because they are designed to different water temps. eg the ASHP likes to, in fact needs to, run at low temps and even perminately on if necassry, whilst the boiler is about running at high temps for rads and hot water.

Whilst the green and money way is to go with a ASHP it would be a brave man who put all his eggs in that one basket and almost certainly would require additional heating in the coldest and particularly damp days when the ASHP ices up. This could be countered by E7/ TOU tariffs.   

I have often wondered how much heating do you require upstairs when heat is alway rising in a house so well insulated. Then of course if you had a near airtight house you could have mechanical ventilation which would definetly even out the temps.

You also need to consider PV and the future of EVs and this leads to TOU tariffs and then this makes the HP more attractive.

Replacing the old boiler when you have removed the downstairs heating seems counter intuative to me.  My gut instinct is to leave it just in case it is needed but then work to not use it.  A house with 4 beds and baths will be fitted with big boiler and big tank much of which will not be necassary in your insulated house.
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Countrypaul
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« Reply #3 on: October 21, 2019, 02:22:47 PM »

Our house is about 225m2 dormer bungalow which we significantly renovated and extended moving in last year. Based on your figures of 500 electricity and 1000L of oil pa, that equates to about 10K kWh of heating from the oil boiler of which 80% might be used the rest lost to things such as the hot exhaust gases etc, so possibly only 8000kWh of heating used.

You don't say how you heat the house currently in terms of is it just upto temperature for getting up and in the evenings, relying on the fat warm up time of radiators, or is is kept warm 24/7? When do you have your heating on, just Oct - Mar or all year round? How do you currently heat you DHW during sumer is it via the oil boiler or electric? What part of the country are you in? What sort of CWI do you have?

How air tight is the house, putting in a B&B ground floor (assuming you are replacing a suspended wooden floor) with insulation and a screed should help with air tightness but make sure you check the edges as I have found a couple of places with droughts at the edge of our screed where cables and pipes come up from below (armoured maisn supply to the CU and 22mm pipes for the hot and cold water). Do you have an MVHR syste or similar?

I went for a thermal store with fitting to support a heat pump, Wood Burning Stove and solar thermal along with immersion heaters (3). We used under 10K kWh for heating over the last 12 months, but have improved things in several respects since. We relied entirely on the immersion heaters (mainly on E7) for that period, but have now implemented an Eddi solar diverter (we have 3.3kWp of PV) sealed several air gaps, implemented zone control on the UFH (B&B floor, 120mm PUR/PIR insulation and 70mm S&C screed throughout the ground floor), added things like curtains/blinds etc. The house is tripple glazed on the north facing windows but double everywhere else.

I recently calculated the cost and benefits of fitting an 8kW ASHP. Based on a COP of 3 (since we would not use it during the warmer part of the year I don't think relying on the manufacturers cop of 4 is valid and even 3 might be overly optimistic) and found that the payback assuming perfect running would be between 9 and 13 years compared to immersion heaters! Should anything go wrong with the ASHP that could easily extend by several years and given that it has lots of electronics inside I think it is fair to assume it is likely to fail at some point before that initial payback period is up. We have decided to postpone the ASHP and see what happens this winter and if our calculations still seem valid.

I would have preferred a plant room but have ended up with things split between the TS on the first floor (along with the pumps) and the CU, MVHR unit, ground floor UFH manifold, internal stop cocks for the water in the utility room and the comms rack in the study.

The amount of insulation you have sounds quite minimal compared to todays standard (again you do not mention what sort of insulation is in the loft), for comparison we have generally 150m of PIR/PUR in the roof (most are SIPS) with some having more. The walls generally have between 150 - 170mm of PUR (though one had 100 of PUR and 50 of XPS, and one has 70m of PUR and 50mm of rockwool). The whole first floor, roof and some ground floor walls are SIPS based and I spent a lot of time and effort taping all the joints holes etc. to ensure a good level of air tightness.

In you position I would look at the insulation levels (forum mantra Insulate, insulate, then insulate) the air tightness (but if you make it too airtight without an MVHR system beware) and then see if you can pass another year and determine how much heating you then need. Put pipes in place for an ASHP, oil boiler, WBS etc. if you can as that is trivial compared to the upheaval afterwards. Measure the energy used for the following 12 months and then analyse the costs and benefits of the various heating alternatives.



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todthedog
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« Reply #4 on: October 21, 2019, 03:14:26 PM »

Always look to improve insulation we have increased the loft to 400mm.

We are 2 adults and use an electric shower already installed.  We are looking at an inline instant heater for kitchen and shower basins no lag in pipes and no tank at all.
Doing my sums.
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biff
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« Reply #5 on: October 21, 2019, 03:51:19 PM »

A plant room like TT described it,  is the way to go.
Yet sometimes the building does not suit such a plant room because of either the extra distance for the pipework or shortage of space.
  Complete ground and first floor plans would need to be drawn up, leaving you with the ability to superimpose the first floor over the ground floor.
 Then pen and A4 and a good calculator. Ideally , putting all the manifold in the Plant room enables you to see at a glance the differences in performance and should future tweaking be needed,  ( ie  fitting zone time controlled zone valves or even a bigger thermal store) it can all be done in the plant room with the minimum of fuss and disturb
      Biff
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Bikerzz
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« Reply #6 on: October 21, 2019, 04:36:13 PM »

So a plant room is a non starter. However I will have a utility room where the manifold and a cylinder could go.
Boiler is 83% efficient the man guessed when serviced last year. He has a device that tests it.
I have no open chimneys.
I live in Midlands (Warwickshire) CV47
My objective is to save money in the long term.
Heating only on October - March.
No MVHR system.
Loft insulation not planning on increasing as if do loft conversion I will go to warm roof.
I have fitted triple glazing and some floor insulation (with UFH) so I will insulate where I can. I also will be getting thick curtains for the french doors at back of house.

From what I can gather...... take out the Hot water tank upstairs and go for unvented cylinder next to UFH manifold downstairs in utility. But everything else just wire and plumb best I can for and maybe just Loads of Solar PV if figures stack up with 2 x 3kw Immersuns next year?

Clearly spend money on the loft conversion and get some celtex in it when I do the loft conversion. But bar external wall insulation which will never be worth it. I will be going round and sealing up any airgaps I can during the work.
TBH I didnt think 1000L of oil a year was that bad tbh.
« Last Edit: October 21, 2019, 07:01:07 PM by Bikerzz » Logged

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Countrypaul
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« Reply #7 on: October 21, 2019, 05:10:09 PM »

Loads of solar PV will help you, but remember that during winter when you need heating the most there is likely to be very little produced by the PV. PV should certainly help with the shoulder months, but  not much in the coldest period.

If you seal all the air gaps and have no mechanical ventilation you will have problems with condensation and mould. Do your windows have trickle vents - if not you will seriously have to consider how to ventilate.

1000L of oil per year is not bad at all in my opinion, as said earlier that is about 8000kWh of heating at 80% efficeincy - so roughly what you currently use.

If you go the ASHP way you may be able to get RHI payments to help with the cost, however they only pay on the heat output by the ASHP not the energy input, so an ASHP witha COP of 3 will only be paid for the 2 units of heat generated from the air and not the one from electricity. In your case that would likely be on about 5000kWh pa so about 500. I found that the cost of an ASHP from an MCS registered installer claiming RHI was about 10K more than a non MCS/RHI installation for a similar situation to yourself so you can see how long it would take to recover the difference and RHI is only paid for 7 years IIRC. Make sure you get your own figures though, as things may have change and I could have made a mistake (or several) in my calculations.

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Bikerzz
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« Reply #8 on: October 21, 2019, 06:52:05 PM »

Thanks
Maybe I just size PV for summer.... maybe I will have a electric car....... things will change!
So would you plumb manifold straight to boiler or use Unvented cylinder as a buffer? That means longer burns for boiler, more hot water for Mrs and can supplement it slightly with immersun PV.
Again this will depend on sizing for unvented cylinder, but I think plumbing to cylinder is sensible.

I dont have trickle vents but Im not sure Im that air tight or ever will get there! I have a cat flap (ok its a pair and through a porch so not that bad), but Im certainly not at risk of being air tight anytime soon!
« Last Edit: October 21, 2019, 06:59:48 PM by Bikerzz » Logged

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offthegridandy
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« Reply #9 on: October 21, 2019, 08:33:03 PM »

As I hope to have an ASHP and some solar thermal to play with shortly I've been looking into tanks and heat stores and with apologies to the hosts have been looking at the Gledhill stainless steel open vented thermal store. It will run the UFH directly from the heat store and will need a small header tank just higher than the rads. It can have energy input from conventional boiler plus ASHP and solar and wood burner.  Instant DHW is supplied at mains pressure via a heat exchanger and 2 X electric immersions can be fitted.  About 1200 I think. I'm still doing research myself but think it looks a very interesting concept.

If your house is well insulated I'd wait to see how much you need the upstairs radiators once the UFH is up and running.  Ours have been disconnected for the last 2 years and we don't miss them. I'd put the thermal store down stairs and connect the UFH and then fit blank plugs and wait and see.

I think you'd need to do some proper calculations before deciding to try without a conventional boiler but new oil balanced flue boilers are supposed to be the dogs danglies.   It would be nice if an ASHP with a COP of 3 could do the business with PV back up.  Being off grid myself I always have to watch the total power available but on mains it may be the most efficient route.

By the way, as stated by others your bills are pretty reasonable I'd think at present.

Re internal ventilation, I suggest you look into PSV passive stack ventilation.  This methods removes warm moist air from kitchen and bathrooms and using a venturi outlet fitted in the roof ridge allows the moist air out.  Once the zone has dropped to correct relative humidity the room vent closes and no heat is lost, We have PSV through out the house and its brilliant and uses no electric  either.

Cheers.

Andy

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TT
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« Reply #10 on: October 22, 2019, 08:09:00 AM »

Any thought of a wood burner with a water boiler?
This can be linked to provide water heating into the thermal store.
Add PV or solar thermal too and you are covered.
Some  towel radiators with electric elements so when heating is off, PV is heating towel rads.


Oil or ASHP too and that's heating covered also factor in electric wet heating if the load is reduced, no maintenance cost to factor, ie annual servicing etc.

I have wood burners, gas combi, shower off the combi and one electric, PV some cleverly placed ducts for future installations too!
Just gives options.

Insulate as others have said makes a big difference to the heating load.
I'm insulating my upstairs loo, with no heating on( getting new radiators installed) a recent dropped ceiling filled with insulation has increased room temp dramatically.






« Last Edit: October 22, 2019, 08:14:17 AM by TT » Logged
brackwell
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« Reply #11 on: October 22, 2019, 09:24:10 AM »

People often quote boiler efficencies of 80+ %.  However Energy Saving Trust did a test of modern condensing gas boilers of both combi and system boilers but the report is now achived.

However the efficiences quoted are for boilers which are fully up to working temp and therefore do not include stop/start losses but nevertheless do represent a boiler that is on for a long time as in a true CH use with the hot water heated simultaneously.   They do not apply out of the CH season or for short periods of operation.

During the non CH periods (which are increasing due to better insulation) and used for HW only then the results paint a different picture.  For a combi boiler run for a significant time eg shower/bath but not hand washing for eg. the efficiency can get to 50% but for a system boiler the efficiency is around 33%  (these are measured by energy in v energy out). 

Therefore in energy saving terms it is advisable to have another heating DHW system and this is where the PV diversion and instantaneous systems come into their own.  I believe the best system for HW is PV with the back up of a inline leccy heater for the days the pv does not quite get there.

Ken
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Bikerzz
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« Reply #12 on: October 22, 2019, 10:37:24 AM »

I have a chimney that was blocked up years ago and been plaster boarded and plastered over, I could open it up. I grew up in the country with a wood burner doing water and heating (living nearly off grid). However now with my lifestyle, it is hassle, a mess, no free wood really (a few here and there) combined with having a chimney isnt great for insulation meant I wasnt planning on having one.
« Last Edit: October 22, 2019, 10:47:33 AM by Bikerzz » Logged

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Countrypaul
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« Reply #13 on: October 22, 2019, 11:44:51 AM »

Thanks
Maybe I just size PV for summer.... maybe I will have a electric car....... things will change!
So would you plumb manifold straight to boiler or use Unvented cylinder as a buffer? That means longer burns for boiler, more hot water for Mrs and can supplement it slightly with immersun PV.
Again this will depend on sizing for unvented cylinder, but I think plumbing to cylinder is sensible.

I dont have trickle vents but Im not sure Im that air tight or ever will get there! I have a cat flap (ok its a pair and through a porch so not that bad), but Im certainly not at risk of being air tight anytime soon!

If you are going to put PV in, then go for the biggest you can fit/are allowed/can afford - the extra cost for the additional PV is small compared to the setup costs of scaffolding etc. If you get PV done the same time as a loft conversion you might save some of those costs depending on how things are done.

IF you do have a loft conversion and that is done properly it should be very airtight in which casse you will need to think carefully about the ventillation. It might be worth you getting a couple of humidy meters - they only cost about 2 ea from ebay and give relative humidity and temperature. Worth checking each room out before you start any changes so you know what effect the changes have. Our last house we upgraded the windows loft insulation, air tightness etc. but  found we then started to get mould in places especially on the walls (solid with no insulation - so always cold though) and not helped by going from 1 occupant working full time and away on business 180 night a year to 4 occupants at home most of the time.

I would plumb any system into a thermal store or buffer tank as your heat requirement is already quite low so the UFH may not require much heat so could cause short cycling of a HP or boiler reducing efficiency significantly. You will always have the problem of supplying UFH and rads from the same source but fitting larger radiators and running at lower temperature would help - but you may need to increase you pipework size especially if they have used microbore to plumb them.

Is you boiler within the house thermal envelope, if so then resiidual heat in the boiler will contribute to the house heating, if not then you could well be leven less efficient. The efficiency the engineer quoted will be purely the boiler and as Ken has highlighted, that can be much much higher than overall efficiency.
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Bikerzz
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« Reply #14 on: October 22, 2019, 12:24:37 PM »

So Thermal Store with a couple of immersions and a boiler loop, rather than a unvented cylinder? I do lots of reading around Unvented Vs Thermal store and I still dont see much difference bar unvented is mains water pressure and TS meaning I will need pumps, but a Unvented I might need a pump anyway depending on pressure (I guess I might being a large ish house)
I presume largest thermal store I can easily fit? Which is going to be about 400L in my utility room.

I will stick as much PV as I can on my S/E and S/W roof
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