Navitron Renewable Energy and Sustainability Forum

HEAT PUMPS & Geothermal Energy => Heat Pumps => Topic started by: Bikerzz on March 10, 2019, 06:31:34 PM



Title: System Planning Advice
Post by: Bikerzz on March 10, 2019, 06:31:34 PM
Im busy renovating my 1967 detached property and this summer will be getting a few trades in (Im too busy and not that great at DIY so done the manual labour bits).
It will involve UFH (water) whole of downstairs along with a new kitchen (47m2 worth of kitchen) so have space for a cornered off utility type room where at the moment stand an old oil system boiler.

The plan is to run UFH off this oil burner for another year and replace with a ASHP next year and Solar PV on the roof once we saved up again for another year.  The house has the usual Hot Water Tank upstairs in airing cupboard and 2 cold water tanks in loft.  

The question is once we have a ASHP should the Hot Water Tank be next to where the ASHP will be (Kitchen Outside wall) as I see this on many peoples houses? Or Can it stay upstairs (I know it will need to be replaced with a modern Tank)?
Im hoping to run ASHP with UFH at very low temp (Sub 30c) to keep the COP high and then Solar PV to power ASHP and Immersum in the hot water tank.  

Im asking this now as we are doing kitchen designs and wondering if I should factor in some space for a Tank Downstairs?

Cheers


Title: Re: System Planning Advice
Post by: titan on March 10, 2019, 07:46:24 PM
First thing to do is calculate the heat losses from the building before considering a ASHP. As you say ideally you want to run the system at lowish temperatures this is just not possible if the heat losses are too great. Unless you have managed to get a lot of insulation into your house I think 30 deg flow temperature is unrealistic.


Title: Re: System Planning Advice
Post by: Bikerzz on March 10, 2019, 07:51:51 PM
Oki. We can ignore my comment of 30c.  Im just after advice of what space I need/may need to allocate for tank etc...
The whole house needs plumbing/Wiring and renovating hence going for UFH. Maybe I wont ASHP (Although I think I will), currently house has small rads with a boiler running water at 50-55c (its non adjustable and on its last legs).

I didnt think you could EVER run your UFH hotter than about 35c anyway?
Isnt your comment on ASHP irrelevant if UFH has a limited max temp anyway?


Title: Re: System Planning Advice
Post by: rogeriko on March 10, 2019, 08:56:28 PM
30 degrees is fine for underfloor heating, its just that you need a lot of it. Will an air source heat pump be able to supply in january/february without running continuously and costing a fortune. Insulate Insulate Insulate or you will have enormous electric bills.
Solar PV will not power an ASHP in the winter nor will it heat your DHW so forget about that.
Spend your money on external wall insulation.


Title: Re: System Planning Advice
Post by: gnarly on March 10, 2019, 09:40:57 PM
How many liters of oil do you get through in a year - that would give some idea of the size of heat pump needed.


Title: Re: System Planning Advice
Post by: linesrg on March 11, 2019, 07:07:14 AM
Bikerzz,

As others have suggested you need to calculate your current energy usage/ loss and the situation you will be in when you plan to install a ASHP.  You don't say how much of the work you are planning on having done is insulation related.

In my property the downstairs bathroom has always been the 'controlling' factor and I have always underestimated this space's energy demand. For instance yesterday the GSHP was pushing water out at 38oC as dictated by the bathroom whereas the Shower Room was only seeking 35oC and other rooms less than this.

It is next on the list for 'overhaul'.

Regards

Richard


Title: Re: System Planning Advice
Post by: Bikerzz on March 11, 2019, 07:18:08 AM
We used 2,900KWH a year on Electricity and Approx 1200 Litres of Oil so not terrible really for a 6 bed 240m2 detached house. Although I dont think its ever been above 19c as Im tight!

The insulation is:

Attic - Cold roof (Currently) 200mm in loft of rolled fiber (was only 100mm when moved in and going to 200mm hasnt made any noticeable difference) - Easy to upgrade if needed, although might do a loft conversion and put celotex in roof.

Walls are 50mm cavity which has been insulated, Fiber batts in extension and blown white fluff  in the older part.

Windows are Triple glazed.

Floors are Timber suspended (100mm celotex will go in with UFH)

Block and beam extension done in 1994, no insulation on top of beam - Will be putting 60mm minimum, some will get 100mm in. (Floors on different height currently)

According to the heat loss calculator you once pointed me too (MCS_heat_pump_calculator_v1_8) Heat loss is 14,700 watts for whole house, but that doesnt tie in with how much oil we are using currently (I guess they think the house is always kept at 21c or something daft).  I live in a conservation area so not sure I can get a heat pump (tho this sounds a mad rule, rather than burning oil), so still need to ring council planning.

Another calculator found online (Calculation-tool-for-design-of-low-temperature-domestic-heating-systems---V1.2) shows 10,050 Watts.

Cheers


Title: Re: System Planning Advice
Post by: brackwell on March 11, 2019, 07:58:34 AM
need a reality check perhaps?

1200L of oil is c 12,000 kwh/yr is it not.    This is in itself a reasonable amount for this size of property but where else is that amount of primary energy going to come from? definetly not from solar during the heating season!


Title: Re: System Planning Advice
Post by: biff on March 11, 2019, 09:07:32 AM
 Bikerzz, this is a good thread,
                It is the kind of thread that Navitron excels in. The members have lots of experience in heating and insulating and are glad to share it.
  I was going to suggest that the first thing that you do is install a 4kw ground mount PV array that will start paying for itself immediately. It will lighten the cost of the use of power tools and other extra running costs that crop up while refurbishing houses. But I noted that you live in a conservation area and getting that organised could be a load of hassle and then maybe you don,t have the room for a ground mount. The great thing about PV is that it starts paying back the moment you switch on. There is very little to go wrong and unlike a lot of other things it is good for 25 years so you can plan ahead.
     As for your refurbishment build. Take your pick and work to a plan but Insulate,,insulate and insulate again.
                                                       Biff


Title: Re: System Planning Advice
Post by: titan on March 11, 2019, 09:32:01 AM
Oki. We can ignore my comment of 30c.  Im just after advice of what space I need/may need to allocate for tank etc...
The whole house needs plumbing/Wiring and renovating hence going for UFH. Maybe I wont ASHP (Although I think I will), currently house has small rads with a boiler running water at 50-55c (its non adjustable and on its last legs).

I didnt think you could EVER run your UFH hotter than about 35c anyway?
Isnt your comment on ASHP irrelevant if UFH has a limited max temp anyway?

Depends what size tank you are considering. Something much bigger than standard cylinder to make the use of your PV, unvented means you can get rid of the loft tanks and you get mains pressure hot water. Size of heat pump required will also depend on the floor size and construction, tiles,wood ,carpet etc. You only mention downstairs are you having  other heating elsewhere will it run at the same temperature or will groundfloor UFH heat whole house.


Title: Re: System Planning Advice
Post by: offthegridandy on March 11, 2019, 09:38:58 AM
Hi Bikerzz.

Can't actually answer your question but if it was me I'd plan to put the new water cylinder down stairs close to the heat source/boiler. 2 reasons 1 the losses are less and the plumbing should be easier. 2 Any heat losses in the boiler cupboard/utility area will tend to rise and heat the habitable room above rather than the cold attic over the 1st floor.

As regards the mantra on insulation; all true but having invested in the insulation.  DO spend time very carefully sealing around all air gaps.  Watch out for trades cutting stuff  away to allow for pipe runs etc and ensure that all gaps and cracks are well sealed before closing up and plastering.  You will be amazed at how much heat can be lost through a small gap once the wind gets up and starts forcing its way around the cavity or up under the facias and soffit boards.

EG if you have access at the appropriate time.  Beam and block floors can be sealed by making a sand and cement slurry and brushing it in across the blocks.  The slurry will seal small gaps in the blocks reducing heat loss from below the insulation.  If using rigid foam insulation follow the manufacturers guidance on joint sealing.  Buy the proper foil backed tape and us it carefully on every butt joint.  The tape may seem dear but you are only doing the job once, so do it right.  You'll not get another chance.

Good luck.

Andy


Title: Re: System Planning Advice
Post by: Bikerzz on March 11, 2019, 11:32:02 AM
Thanks people

Yes 12kwh a year in oil does seem a lot, any idea what that would cost in Electricity from a ASHP? At a COP of 3 and 0.15p electricity isnt that only £600?

This is a 30 year home (Im only 31 and plan to live here till I retire), I have 0.75 acre so enough land space but more importantly a roof facing SW which should get me at least a 4kw array on.
Ok, will not be determined to go for ASHP. However I should leave enough space in utility for a thermal store with a Immersun off some PV.  For a 240m2 House how big unvented thermal store should I be looking at ? (4 bath rooms) but no children YET.........

The UFH is a good idea as radiators and plumbing have had it anyway and house needs redecorating and wiring, the Mrs also is happy for tiles around the whole house with only 1 room she would like engineered wood and living room she still wants carpet, but bar that tiles which is great.

I will just keep the oil boiler going as long as it does and when goes bang look into what could be more sensible, and get as much PV on the roof as is reasonable when I can afford.



Title: Re: System Planning Advice
Post by: andrewellis on March 11, 2019, 01:53:17 PM
Whatís the ground like? We had a ground source heat pump out in last year and Iím delighted with it.   We are in Scotland and the ASHP calculations didnít stack up as the COP drops off fast with the lower temperatures. You find most manufacturers wonít even provide the figures. A borehole might get round the whole conservation area issue. It cost more but our brine temperature didnít drop to zero until we hit -10 giving a fantastic cop through the year even on radiators. The best part is if you are staying, the cost of install/capitol all pays back over seven years from the RHI. An ASHP wouldnít do the same.


Title: Re: System Planning Advice
Post by: Bikerzz on March 11, 2019, 01:56:21 PM
Whatís the ground like? We had a ground source heat pump out in last year and Iím delighted with it.   We are in Scotland and the ASHP calculations didnít stack up as the COP drops off fast with the lower temperatures. You find most manufacturers wonít even provide the figures. A borehole might get round the whole conservation area issue. It cost more but our brine temperature didnít drop to zero until we hit -10 giving a fantastic cop through the year even on radiators. The best part is if you are staying, the cost of install/capitol all pays back over seven years from the RHI. An ASHP wouldnít do the same.

Thanks I ruled this out due to cost. Id have to have Bore holes although could have a few. Garden is on a slope not suitable for trenches really as alot if block paved. CV472YF is postcode (Warwickshire)


Title: Re: System Planning Advice
Post by: Countrypaul on March 11, 2019, 02:48:39 PM
Thanks people

Yes 12kwh a year in oil does seem a lot, any idea what that would cost in Electricity from a ASHP? At a COP of 3 and 0.15p electricity isnt that only £600?


12kwh a year would be great for any house, that woudl be 60p /year - unfortunately you mean 12MWh a year, and yes that works out at £600.

Our house is 225m2 and we have a 430L thermal store. Currently heated by immersion only, but will be putting in an ASHP this spring one other things are out the way. We already have 3.3KWp of solar panels, so will also be putting in a diverter to utilise more of the PV generation.  The immersion heaters were put in as a fail safe in case the ASHP were to develop a fault, meant we could keep the house warm all the time, as it worked out we have relised on them this winter. Total house heat load has been well below 4KW (6KW during E7 and 3KW during the day) even during the cold spell at the start of January, that compares with the calculations I had done coming in at just over 8KW (at -3C) so quite a bit better. Ground floor has 125m2 of UFH in a 60mm screed over 120mm celotex, upstairs has UFH for bathrooms only - about 15m2 total fitted from below using spreader plates with 22mm chipboard and then tiles.

Our thermal store in on the first floor for a couple of reasons - but mainly convenience and our plan to put a WBS in the lounge so we could have gravity feed to the TS in case of power failure. We are also in a conservation area and the ASHP will be about 20m from the TS plus 3m lower. The size of the TS was limited by the space available, otherwise I would have gone larger and taller.

If you can, I would keep the oil burner for use in case of emergencies, such as HP break down, very cold weather resulting in the ASHP not coping etc. You might also want to look at air to air heat pumps, I know a few threads on this forum have been about the subject and view them very positively mainly as a supplement that avoids or delays having to put the main heating on.


Title: Re: System Planning Advice
Post by: linesrg on March 11, 2019, 05:44:31 PM
Bikerzz,

Having a system which uses an Immersun which diverts Solar PV to two immersions in a heat store I'm coming around to thinking this isn't the most efficient thing to do.  In fairness others have made this point elsewhere on this forum.

For the sake of argument say you use your Solar PV diverted to heat water then let's say this is an 80% efficient process.  If you take this same amount of energy and use it to charge batteries and you have roughly the same level of efficiency.  This is a simplistic argument so absolute accurate figures aren't essential.

If you have a heat pump then let's say it has a COP of 3.0, using the energy stored in the battery you get much more energy back overall then using an Immersun to heat water in a heat store.

Regards

Richard


Title: Re: System Planning Advice
Post by: nowty on March 11, 2019, 07:33:45 PM
Yes 12kwh a year in oil does seem a lot, any idea what that would cost in Electricity from a ASHP? At a COP of 3 and 0.15p electricity isnt that only £600?

A GSHP may give you a COP of 3 in Winter (mine does), but you aint gonna get a COP of 3 with a ASHP in winter when you need the heating the most.


Title: Re: System Planning Advice
Post by: Bikerzz on March 11, 2019, 07:51:13 PM
Thanks people. I have rang council about solar PV and ASHP being allowed in a conservation area and awaiting a call back.
However going back to ASHP and 12MWH, £600 in electric sounds like a bargin, even compared to how cheap oil is at the moment (which can only get worse)
Im very open to suggestions, however none of you have really put me off a ASHP yet, a £1k electricity bill each year maybe less with some solar, sounds fine to me...... Im not going to go throw away the oil boiler until it breaks or oil get stupid expensive again, so dont worry I wont make any hasty decisions.
I will look into Thermal stores and unvented cylinders, however with many sources of heat I guess a TS is more appropriate (and the fact Im not sure living out here on the end of a water main gives me the best water pressure, and Im up a hill)


Title: Re: System Planning Advice
Post by: rogeriko on March 11, 2019, 09:48:28 PM
In the winter dont forget your ASHP will continuously freeze up outside and then it will run full power in reverse to defrost itself. Despite what the manufacturers say you wont get a cop above 2 when its cold and damp outside. If you need 10kw of heat to continuously maintain your temperature thats 5kw of electric 24h per day which will cost 540 pounds per month. Please forget the theory, these are the facts.  (I install heat pumps)


Title: Re: System Planning Advice
Post by: Countrypaul on March 11, 2019, 10:35:26 PM
In the winter dont forget your ASHP will continuously freeze up outside and then it will run full power in reverse to defrost itself. Despite what the manufacturers say you wont get a cop above 2 when its cold and damp outside. If you need 10kw of heat to continuously maintain your temperature thats 5kw of electric 24h per day which will cost 540 pounds per month. Please forget the theory, these are the facts.  (I install heat pumps)

If he would need only £600 per year for direct electric heating, there is no way he will need anything like £540 per month even in January!

Whilst an ASHP might not be the most efficient solution in winter, it is likely to be better than direct electric heating most of the time in this country except perhaps during a very bad spell such as the "Beast from the East" last winter. Relying on an ASHP for most of the time but having the oil boiler available for any really bad spell could be an acceptable compromise. 


Title: Re: System Planning Advice
Post by: Bikerzz on March 12, 2019, 07:26:49 AM
Thanks Roger I understand.

As Paul said - Im my non understanding mind (Im still learning), running a ASHP 90% of the time with water at 20-30c for just UFH must be the most efficient I can get? Then boiler for bad winter spells?

I also have unlimited supply to lithium batteries but that's for another topic.


Title: Re: System Planning Advice
Post by: biff on March 12, 2019, 09:19:59 AM
           "I also Have an unlimited supply of Lithium batteries"
       :o :o :o  I Say ,
                     Biff


Title: Re: System Planning Advice
Post by: Bikerzz on March 12, 2019, 09:27:29 AM
           "I also Have an unlimited supply of Lithium batteries"
       :o :o :o  I Say ,
                     Biff

Not ones I can hand out sadly. Its what I do for a living 12v and 48v automotive dev engineer


Title: Re: System Planning Advice
Post by: gnarly on March 12, 2019, 10:36:05 AM
Is 48v automotive really coming? Itís only been 10+ years!

I would take heed of rogerikoís comments that ASHP specs donít reflect real life amd they switch to full price resistance heating when they going gets tough (and freeze / defrost cycles that donít actually produce much overall heat).  But you have the perfect solution if you are keeping your oil, you just have a control problem where you need to use the ashp when not so cold out, and the oil on the coldest days.


Title: Re: System Planning Advice
Post by: Bikerzz on March 12, 2019, 11:25:49 AM
Cheers.

Sounds like I need a full system expert in..... good luck finding one! (Warwickshire - anyone?)
Im going to be here 30+years so I dont mind if payback is 20 years but I want to do it right and once.

Cheers


Title: Re: System Planning Advice
Post by: Bikerzz on March 15, 2019, 11:11:19 AM
Is 48v automotive really coming? Itís only been 10+ years!

I would take heed of rogerikoís comments that ASHP specs donít reflect real life amd they switch to full price resistance heating when they going gets tough (and freeze / defrost cycles that donít actually produce much overall heat).  But you have the perfect solution if you are keeping your oil, you just have a control problem where you need to use the ashp when not so cold out, and the oil on the coldest days.

It already is here. You can buy 48v systems on a few vehicles today. MHEVs they call them.

I honestly have no clue what to do about heating the house. A plumber coming next week, see what he says. (I will of course take with a pinch of salt)


Title: Re: System Planning Advice
Post by: Countrypaul on March 15, 2019, 11:28:17 AM
I made the consious decision when renovating to decouple the heat generation from the heat emission within the house. We went with UFH for the heat emission as almost all forms of heating would drive that (Air to Air heat pump excluded, and if you really wan to use night storage heaters they wouldn't either), and by using a thermal store I figured that I could combine multiple heat sources relatively easily and update the heat souce in future should a new technology appear.

I'm not sure that most plumbers would think that way, more likely they want to put a system in without the flexibility you may want in the future.  Even teh heat calculations carried out by the plumber are likely to be very rudimentary and include a large margin to ensure it is warm enough regardless of whether that costs more to operate than is should or not.


Title: Re: System Planning Advice
Post by: Bikerzz on March 15, 2019, 12:09:10 PM
Thank Paul

Basically Im willing to invest in anything that will payback in 20 years, if I plan on living here for 30 years ish.  Yes I have to be slightly flexible as Mrs might add to the size of family and maybe we convert the loft etc....

However starting the major renovations this year and UFH seems a no brainier, its just what pipes should be put in where and what electrics etc.... Do I leave space for a Thermal Store or Unvented cylinder in utility room?  What Size?

I will probably add Solar PV (Id consider thermal but I think PV is the way to go now), and I battery bank is a no brainier really for my position.

If Im putting UFH in on an oil boiler I really need at least a 120L buffer store if I dont go for a larger TS.


Title: Re: System Planning Advice
Post by: DonL on March 15, 2019, 02:17:53 PM
I was just a bit concerned about the negative advice on ASHP's. I have one and my experience has been entirely positive with very low electricity bills.
I recall a report I read a few years back in which they compared actual results for ASHP's and GSHP's. The difference was pretty small but the spread of results on both was enormous. So, in my view, the most important thing is to get the design right with the lowest practical design temperature for your heat emmitters to get the best COP (I replaced conventional radiators with larger units operating at a lower temperature).
The other main source of problems is people operating the system wrongly. To get the best COP and low radiator temperature it needs to be set up so that it runs most of the the time to maintain house temperature with the water temperature varying inversely to the outside temperature. People expect to run it like gas fired central heating and leave it off all day and then turn it on in the evening expecting to get a warm house, and when that doesn't work they turn up the water temperature, the COP drops and the bills go up.
I'd go so far as to say that if the house is unoccupied for a lot of the time I wouldn't choose a heat pump.
So: Insulate
Draft proof
Insulate again
Have a properly sized and designed heat pump
Run it the way it should be run.


Title: Re: System Planning Advice
Post by: Bikerzz on March 15, 2019, 02:27:39 PM
Thanks Don

Im thinking if I could run the the UFH off a ASHP that would be great! Low temp constant, not sure how in winter I could move over to boiler/TS, but might be a simple way.
Run the hot water off Solar PV and boiler in the winter.



Title: Re: System Planning Advice
Post by: gnarly on March 16, 2019, 08:15:43 AM
DonL: do you have an alternative heating source that you also use?  Eg. In Ďbeast from the eastí type conditions.  And do you monitor the ASHP consumption in really cold conditions (do you know if an electric heater is kicking in?)


Title: Re: System Planning Advice
Post by: brackwell on March 16, 2019, 09:18:45 AM
one can have a hybrid heat pump system which uses the FF boiler once the ambient temp drops to say 3C.



Title: Re: System Planning Advice
Post by: biff on March 16, 2019, 09:23:26 AM
I have been following this thread Bikerzz.
  Most of the members have hands on experience including myself. I found that I needed a base plan. A place from where to start from and form a plan on paper both in the physical sense and time line sense. You need this to run in sync with your family life..You can leave conduit.  Pipes and facilities for additional installs at a later date but the base plan needs to be decided by yourself before you invest a penny.
  So a ruler .pen and pencil. Some A 4 and apt discus sons  will translate to a picture if where you are going. A to scale plan is good. If you work like this then you will not be ripping up work already completed and redoing  it with added unnecessary  expense.  
     I used to love this kind of situation and planning to get everything to come together properly.
  Insulation is the big one. The more you insulate correctly the less heat you have to generate.
       Biff


Title: Re: System Planning Advice
Post by: DonL on March 16, 2019, 02:11:04 PM
DonL: do you have an alternative heating source that you also use?  Eg. In Ďbeast from the eastí type conditions.  And do you monitor the ASHP consumption in really cold conditions (do you know if an electric heater is kicking in?)

I have a log burner in the lounge which is used virtually every evening through the winter and also produces most of the hot water. The ASHP maintains the house at around 18C. The four year average power use for a winter is about 2200kWh. The back up heater has used 13kWh over the 4/5 years since installation. I have no means of measuring COP but it was meeting desired heating circuit water temperatures even during the beast from the east without using the back up resistance elment.


Title: Re: System Planning Advice
Post by: biff on March 16, 2019, 04:19:19 PM
It is difficult to cover everythin but it helps if you write every single idea and good move down in the margins and be sure to date it
 Our system is 2 138vdc immersion with one tank up stairs and one in the hall downstairs.approx 500ltrs between the 2 tanks . These immersion dump everything into the tanks after the house bank has been topped up.
However it cannot have cutouts on the immersion because they also control the wind turbine but I designed the system to fully heat the tanks evenly and completely before heat exchanging any further surplus into the C/H system. This has worked very well for us to date but  it is not perfect. Sometimes we get roasted in the long summer days and we have a choicertain where we can disconnect 2 x 1100 watt strings or leave the windows open. Last year in 2018 we only used 2 strings for June and July. There was also the unnecessary prolonged top end voltage in the bank which causes the cells to fizzle and pop for absolutely  no gain.
  Im not sure if you will learn anything useful from this ramblin it is already becoming as clear as mud.. one thing is very important.  In dull weather like this the solar is still able with the help of the wind turbine to take the bottom lift out of the tanks so that 15 minutes after lighting the stove the rads begin to warm up even on a day like today.
  So we have a system that really does use the water as a bank as well
     Biff


Title: Re: System Planning Advice
Post by: kristen on March 30, 2019, 08:23:16 AM
6 bed 240m2 detached house

I'm figuring that is building-footprint, not floor area over 2 floors? I'm struggling with the maths to get 6 beds in otherwise ... but maybe my bedrooms are "excessively generous" :)

Im busy renovating my 1967 detached property ...

My house is 1960 and pretty much solid concrete. Relative to now, let alone then, its very airtight as a consequence.  It had flat roof (concrete with some insulating stuff mixed in) on top of which previous owner put pitched roof (all the 60's flat roofs leaked ...) and so we now have masses of insulation in the loft too.  Decent cavity, which we filled, modern (but only double glazed) windows.

All of that led to less heat needed Hooray! ... and more damp Boo-Hiss :(

We then retro fitted MVHR (Ducted air, exhaust air passes through heat exchanger and warms incoming air, reducing losses). This is only even the slightest bit worthwhile if the air tightness is very good (otherwise some/most of the air coming in escapes elsewhere, and the exhaust air volume is too low, so the amount of heat that can be recovered is "poor"). That fixed the damp problem and the living conditions are perfect.  We did not replace the aged skirting radiators ... and I have huge regret that we didn't (we suspect asbestos int he concrete floors insulating the old pipes, so didn't go the UFH retro-fit route for that reason).

So, as everyone else has said, plan to insulate and also make it air tight. Also make sure you have no cold bridging. The better you insulate the more dramatic they become, and will lead to condensation and that will lead to damage to materials.

I recommend having an air tightness test done to see where you are. If it is good that test will tell you where the leaks are (they use a smoking joss-stick type thing, and you can see the smoke charging for the tiny gaps :) ) so you will be able to plug them, and if it is rubbish then you will need to prioritise doing something about it.  Otherwise you will basically just be heating outdoors, rather than indoors.

We set about bringing the old house up to passive house standard and decided it was impossible ...

Where did we get to?  We built a Passive House extension and prioritised living in that end. It has kitchen / snug, and master bedroom above, so is all Wifee and I need in winter and we drop the thermostat for main house (unless we have guests staying). Extension has increased house size by 30%, and even allowing for some heat in the extension we have reduced our Winter fuel by 50% (combination of lower temperature, MVHR, more roof insulation and also insulation around window reveals to prevent cold-bringing).

Would I do it again?  Nope, absolutely not. I would either knock-down-rebuild or build on a green field site (or, poor third choice, move out and gut the place to do a proper job). I knew nothing about Passive House 5 years ago when we started, I absolutely would not consider living in a house that wasn't now. We haven't had a winter cough or cold in those 5 years (known benefit), and it is SO comfortable.  Don't believe people who tell you its like living in a plastic bag, the MVHR pumps a huge amount of air through, and that air gets everywhere - so no damp spots in a poorly ventilated corner etc. - people who come here remark on the air quality in the house. We've never had a cooking smell persist or travel into adjacent rooms.

Couple of points that have come up on here before:

In response to Folk saying "I'm going to insulate as best I can" the replies have been "Yeah, I have done that. Several times now. Just do it the once"

And in response to "I'm tight, I keep it at 19C" or "I'm Eco, it must have zero energy" (I was the second) I would say "Be comfortable". I have friends in Passive Houses that just put on an extra sweater in winter. I've changed my stance, what;s the point of that? Plan to be comfortable. We keep the kitchen/snug at 22C in winter. It takes SO little energy (reminder that we are using only 50% of previous energy and house is 30% bigger) it is easy to do. You are 30-something, but if you are staying for 30 years, maybe more, you won't want to be living at 19C then ... and doing so will take a toll on your health.

UFH / heatpump: Consider reversible heat-pump to put cold water through UFH in summer. That's back to "comfort" again, and not cooking in the house and having trouble sleeping in the heat etc. etc. Last summer heatwave highest temperature was a few miles from here, so a good test of Passive House. The Max indoor temperature we hit was 25C, but that's too hot to sit still in, and we have to night-vent to achieve - which is fine, but little-by-little the temperature of the internal fabric of the house crept up day by day over the several weeks heat wave.  You can't night-vent when you are away, and it lets the flys / moths in etc. Would have been much easier to cool the UFH, and we of course there is unlimited PV during a heatwave of course :)

I will look into Thermal stores and unvented cylinders, however with many sources of heat I guess a TS is more appropriate (and the fact Im not sure living out here on the end of a water main gives me the best water pressure, and Im up a hill)

I have huge thermal store (5,000 L). It has multiple heat inputs (Log batch boiler, Solar Thermal, and 2x18kW immersion if everything else breaks!); I could add Heatpump (except that I need HOT water for radiators in old part of house).

It ups the capital outlay, and increases the flexibility.  I could, for example, have an oil boiler speced to produce kW for worse day in the year but running 24/7 at that time, rather than sized for "now heat the house from freezing to comfortable in 30 minutes". The Thermal Store buffering would get me the "heat house quickly" and would also allow the boiler to run in condensing mode pretty much all its running hours.

If mains pressure low you can add a "buffer" pressure vessel if you want to have direct feed DHW. Its nice to have the hot water at same pressure as cold (mains). No tanks in the loft is nice (hot water is potable, no dead rats falling into the tanks etc.). The Continent doesn't do open-vented (AFAIK).

My DHW (mains feed) is pre-heated through TS, so I am not heating DHW from very cold mains temperature. The central heating and UFH is drawn off the TS. The UFH is direct, the old (open vented) Rads are through a heat exchanger (wasn't confident they would convert to pressurised without something blowing ...) so basically just a small heat exchanger box exactly where the oil boiler used to be, no other changes to CH circuit

The swimming pool is heated direct by (separate) Solar Thermal, but can also be heated from Thermal Store - if I have excess heat to dump in summer, or I want the pool hot early in the season.

yes, lots of flexibility, but quite a lot of capital cost too, and plenty of plumbing complexity

But you have the perfect solution if you are keeping your oil, you just have a control problem where you need to use the ashp when not so cold out, and the oil on the coldest days.

My local plumber hates the idea of multiple heat sources onto a heating circuit (that's not the same as a TS of course). For example, he is very against having ASHP for cold water in UFH in the summer, and TS for heat in the winter.

OTOH both my heating engineer and passive house consultant have no problem with it ...

Sounds like I need a full system expert in..... good luck finding one! (Warwickshire - anyone?)
The passive house consultant I used is in Milton Keynes, I expect he would travel to Warwickshire. He is not cheap, but his advice would most definitely tell you what you could achieve (building improvements vs. energy cost for the lifetime of your occupancy) ... personally I like huge amounts of data before making decisions, but I'm not "everyone"

Quote
I want to do it right and once.

I'm an old codger.  That is definitely the right approach ... the money I have spent achieving that in my lifetime made me wince, at the time. All my mates went "Ha!Ha!Ha! Look at him he's off on one again" ... and, thankfully!, followed a few years later by "I wish I had done that"

I'm not sure that most plumbers would think that way, more likely they want to put a system in without the flexibility you may want in the future.  Even teh heat calculations carried out by the plumber are likely to be very rudimentary and include a large margin to ensure it is warm enough regardless of whether that costs more to operate than is should or not.

Mine have been a disaster.  The plumber employed by builder did heat calculations which were ridiculous for a Passive House. He said he used standard calculations, based on the u-values the Passive House guy calculated, and I have no doubt that he did that correctly. He installed seeming very big radiators in bedrooms upstairs, based on his calculations. We didn't use them, not once, in the first winter so we took them out and got all that wall space back ...

As said earlier, my local Plumber doesn't want to install second-source of (cooling) on UFH so I'm going to have to find someone who will.

I've had the cost of Heating Engineer (I mean a proper, qualified, engineer :) ) as well as Passive House consultant to get to where I am now ... but the house is lovely, and SO comfortable all year round. And healthy :)

(Id consider thermal but I think PV is the way to go now)
I have Solar Thermal for DHW/TS and separately for Pool. Both of them have required plumber visit almost annually when air gets in.  not everyone has had problems, but I would not do it again.  I agree, PV + Heatpump, although for HOT water a Heatpump is not great.  Boosting DHW with tubular immersion on pipe might be acceptable if in practice achieving decent DHW temperature is hard (we have very long pipe runs so starting at 60C isn't much COP <sorry!>)

[UFH] needs to be set up so that it runs most of the the time to maintain house temperature with the water temperature varying inversely to the outside temperature. People expect to run it like gas fired central heating and leave it off all day and then turn it on in the evening expecting to get a warm house, and when that doesn't work they turn up the water temperature, the COP drops and the bills go up.
I'd go so far as to say that if the house is unoccupied for a lot of the time I wouldn't choose a heat pump.

Very important point on house occupancy.  UFH needs to be on long hours each day, response time is very slow, if you aren't there all that time it will seem nuts.

But ... if you insulation is good maybe it won't matter and won't bother you.

If we go away for 24 hours, turn everything off, in mid winter, my Passive House bit loses 1C per day. A 3 bed passive house has a heat requirement of something like 1kW in the depths of winter.

So if you can get heat loss down to "nothing" the UFH approach may not matter, even if you are out at work during the day.

Run the hot water off Solar PV
As said I would skip Solar Thermal if doing it again ... but getting water up to 60C+ with heatpump is not ideal.

With Solar Thermal you can heat DHW tank (I do) but then what when that is hot?  I divert the heat to my Thermal Store - which is huge, because designed for Winter heat, and I can then shift that "free" heat into swimming pool ...

The need for a plan to use up excess Solar Thermal is one of its problems. But if you've always wanted a swimming pool don't let me stop you :) ... but PV + Heatpump much better for pool - no shortage of Sun during the swimming season, and if you want to heat the pool early/late in the season you can just use the Grid. But with Solar Thermal you would need "a second heat source" :(

If you read this far well done!

I highly recommend "The Passivhaus Handbook - A practical guide to constructing and retrofitting buildings for ultra-low energy performance.". It is written suitable for both laymen and engineers and will tell you everything you need to know about why Passive House works, and what compromises you make if you only do THIS or THAT.  Also about managing a project of this type (Will the builders forget to do X? Will they pull the wool over your eyes on Y? that type of thing)


Title: Re: System Planning Advice
Post by: Bikerzz on April 04, 2019, 11:18:42 AM
Thank you

Ive just ordered that book.