marshian

Old HG quote system yes - new one no (not yet) it gave me an install cost of £6500 after BUS grant I fully accepted it was a mile out for multiple reasons it doesn’t know 1. what improvements have been done to the in terms of insulation 2. All the rads are now twice the size of originals (which were fed by a non condensing boiler from the 80’s) 3. I’m already running low temp heating (25-35 flow) 4. the house has never had an EPC so it can’t look to that so I didn’t mind the fact it was a mile out

Unless there is a open window the air will take all paths open to it it doesn't need to be much of a leak to cause a dramatic reduction in humidity and as a result condensation

I disagree You don't need trickle vents if you have leaky property - air finds it's own path - past windows - past ceiling roses - anywhere that's not sealed Build Hub "Built it tight - ventilate it right" 100% agree but I'll put £20 on the fact that the OP has a leaky property from an air tightness perspective and a PIV unit will resolve his condensation issues Experience is what you get when you don't want it

Just fit a Positive Input Ventilation (PIV) unit - that’ll solve 99% of your condensation issues

Down side (from a quick look at the specs) whilst it does modulate down to 3.5 kW the min flow temp for CH is 40 Deg (max is 90 Deg) With UFH throughout seems a shame to have to blend the temp down rather than get a boiler that can run at temps low enough for UFH but I'm pretty sure that'll just me me that's concerned about that

I don't agree I've got T22 rads - they replaced T11 rads in a 1980's house - they are the same size as original - just thicker - They are not silly sizes. My WC flow temp starts at 25 deg C and ends at 35 Deg C at -2.5 OAT It's perfectly possible to run UFH flow temps thro rads and still keep a house at temperature

And he has a multitude of suggestions He can pick the bones out of the thread

Couple of times I had to email Octopus because my bill has fallen into limbo land - it ends up in some weird stasis situation and they don't know. Each time it takes about a week. I wouldn't mind betting that's the reason you've only got a bill now

Because at that point he will be missing (hopefully) two x 30 min shower times and rattling around in the house without the need for "unlimited" HW........ Plus lets not forget - not having a tank rules out any PV assist to water heating during summer months if that is later added....... Combis are fine for small houses, apartments and flats - madness IMO in a house with 3 bathrooms and a requirement for multiple showers at the same time

No entrapment there at all - Not Guilty is my plea I don't think there will be 1. A ban on sale of gas boilers or 2. Gas will run out But I do think cost benefits to convert from gas and oil to ASHP will be incentivised by methods other than a grant and price of the fuel is one

I refer the honourable gentleman to my reply to @JohnMo I specifically did not say anything about a ban on gas or it running out The economics of ASHP conversion are currently being bolstered by a £7500 BUS grant (Ignoring the grant harvesting impact) it wouldn't take a lot of movement in gas price or more importantly the standing charge to further drive the move to ASHP's - especially when the BUS grant scheme ends and equipment cost falls

I feel you need to read the first post again My point which I will make again is that if the space is not made for a tank due to a hoofing great combi and no tank - it's going to be much harder at a later date to fit in a tank into a house that wasn't designed to have one. Not disagreeing with you - more than one way to skin the proverbial - but it's a forum which shares different opinions - the discussion of pros and cons - will hopefully lead the OP to a decision that he has to live with preferably happily!! As far as fossil fuels go (and I have recently replaced a gas boiler with a gas boiler) it might not be a ban on fossil fuel boilers it could as easily be the increased cost of fossil fuels as a result of ASHP becoming the norm - the costs of the gas grid would then have to be covered by the remaining gas customers............... This could result in the "economics" of gas driving further conversions to ASHP....... JM2pW

OP ruled out ASHP on his new build - downside of fitting a bloody great big combi is when he does “have to go” to an ASHP he’s then got to find space for tank which was never allowed for in the build makes no sense to me at all to go down a combi route

Wasn't the point being made........................

80 - 20 rule for me If I can get 80% of the benefit for 20% effort I'm comfortable with the compromise I'm not going to put 80% of my effort in to getting the 20% extra - big wins for min effort every time for me I could have fitted 100mm of PIR under my suspended wood floors v 75mm the cost would have been 40% more 75mm PIR U value 0.33 W/m2K 100 mm PIR U Value 0.23 W/m2K When I considered my actual floor losses once I was over 50mm the bang for buck was done. Payback on 75mm was 4 years (Russia helped me out - I was projecting 8 years based on energy cost increases)

And there in a nutshell is the root of their demise................ Enjoy it whilst it lasts How many Energy "Distributors" have gone to the wall in the last 9 years?? The answer according to google is 51 Quite disappointed the answer wasn't 42..........

I have politely asked @Nickfromwales To do a quick clean up and move non relevant conversation that related to my boiler set up to my Viessmann Journey thread

I was under the mistaken belief that oil fired boiler heating was the cheapest of the fossil fuels? I’ve always assumed the downsides were storage, higher cost of oil boilers and paying up front for the oil (compared to paying after usage for gas) clearly I was wrong?

I'm A OK with all that.............. Doesn't change the need to use math.................

It's OK - don't worry - mistakes I've made a plenty You know the nice thing about making a mistake is you learn................... Observation skills are paramount - math is everything Oh and to keep @SteamyTea away from the conversation don't mention thermal mass and above all don't get units wrong - PS if this seems like a dig at ST it's not - we all need the voice on our shoulder pointing out the error

I think you have a miss-understanding of DHWP....... I think this is partly due to the word "priority" in the description DHWP is about maximising CH run times at low flow temps, accepting a loss of efficiency when doing HW - the priority is getting it done promptly - ie don't muck about trying to go low and slow - hit the HW with higher flow temps - stir the tank up with higher temp differentials and get it done I'm definitely in the camp of not trying to re-heat a stratified HW tank when HW is being demanded (ie showering) that's a recipe for getting lynched by my partner....... Lets say the evening shower time - tank was heated to 50 deg at 7.30am - we've had two showers and taken ~50 Litres out - tank is stratified into 48 deg C for top 50 litres and 20 (ish) deg for the remaining 60 Litres - I try to recharge the cyl and the first thing that happens is the first bit of heat that the coil gets starts a mixing process - top of the tank that was 48 deg drops rapidly to mid 30's OK Gas boiler not ASHP - maybe with ASHP the process would be much more gentle and less stiring the pot...............

Absolutely this ^ before I had DHWP and WC for CH - I was heating the water the previous evening because I was managing the flow temps for CH manually - it worked from an energy usage in CH but having a tank sitting there overnight meant standing losses were much larger and a 117 litres of water didn't manage 4 showers a day Right now with DHWP - water is heated at 7 to 7.30 am based on a schedule for showers at 8am - typically recharged from mid 20's to low 50's - by 11pm same day tank temp no longer will support another two showers at a comfortable temp (up to 11pm it's fine) energy usage is typically 4 kWh to 5 kWh for a recharge Like @JohnMo when I was starting out with DHWP I set the schedule to allow HW cyl re-charge whenever the tank stat triggered a re-heat. Absolute bloody waste of energy - it massively increased the standing losses and increased energy used for HW by 50% for no real benefit. From memory it recharged 4 times in a day - each time taking the tank back up to 50 deg C - some of those losses were due to heating up the primary circuit and firing up the boiler but it didn't work for me. Most economical way for me is heat the water I need to the temp that covers the for the whole day in one hit but I'm sure if my HW usage was different and not fixed other ways may work better.

If I did that to my other half I’d be dead - HW re-charge is done well outside of any shower reqts

Yes comfortable - being 5’ 13” in my socks helps with stuff lije that

I think to bring this thread back round to topic and thickness of screed - to me it’s just making your “heat emitter” aka radiator as big as possible with the ability to soak up temp changes in the environment around us whilst treading lightly with it’s energy consumption. As @JohnMo stated so well you need to optimise whatever heating process you use to cover your needs based on heat loss, occupancy, HW needs and cost - there isn’t a one size fits all - careful thought, some maths, and considered purchases as far as kit/rads, UFH, heat source and HW storage (volume and method of recharge) is required and we all have a duty of care to the planet and it environment to do as little damage as we can - maybe even leave it in a better shape that it was when we arrived on this earth with de-carbonisation. I look around the estate I live on only 67 houses (mix of 3 and 4 beds) and see plumes from every flue first thing in the morning and early evening - so much energy wasted that could be harnessed/recovered with low temp heating. multiply that out on every housing estate in the country and our emissions and energy consumption would drop. oil and gas companies wouldn’t like it much but there is little they could do about it except cut their cloth accordingly………. I’ll get of my soap box and get back to painting fences on what has turned out to be a very nice afternoon