Combating energy prices

[b0rn2sk8]

I thought the higher the KW rating then the quicker it would get to temperature, however it seems this isn't necessarily efficient.

Sort of but not really and its definitely not efficient. There is only so much heat the boiler can put into the loop based on the amount of water in it, the flow rate, the effectiveness of the heat exchanger and how quickly the rads can get rid of the heat into the house. For a boiler to heat the house at 35kw, you need rads capable of getting rid of 35kw.

If you have a regular routine (e.g. you are out at work for the same 10 hours daily) then you are usually better off using set back temperatures rather than letting the hose cool down fully and then heat back up again because of how efficient the boiler is during its different modes. If its running fill tilt, its considerably less efficient than if its tricking in heat to keep the house at a cooler but above ambient (~16C) temperature and then heating the house up the few degrease to get it back to ~20C.

 

[flea.rider]

I thought the higher the KW rating then the quicker it would get to temperature, however it seems this isn't necessarily efficient.

I'll get a play with it when the weather turns cooler and hopefully reach a happy medium. I might get the rest of my radiators upgraded as this seems to be a precursor to efficiency via running at a more constant lower water temperature.

yep .. more area so to speak releases more heat .. so no need to blast your boiler .. i think my rads are set on 2 of 7 ?
edit just checked 3 of 7

 

[Gammawolf]

Sort of but not really and its definitely not efficient. There is only so much heat the boiler can put into the loop based on the amount of water in it, the flow rate, the effectiveness of the heat exchanger and how quickly the rads can get rid of the heat into the house. For a boiler to heat the house at 35kw, you need rads capable of getting rid of 35kw.

If you have a regular routine (e.g. you are out at work for the same 10 hours daily) then you are usually better off using set back temperatures rather than letting the hose cool down fully and then heat back up again because of how efficient the boiler is during its different modes. If its running fill tilt, its considerably less efficient than if its tricking in heat to keep the house at a cooler but above ambient (~16C) temperature and then heating the house up the few degrease to get it back to ~20C.

Thats what i did last winter. I work from home and we have a 3 year old so we just heated the entire house to 18c 24/7 from November to April. House is a 23 year old, 140sqm so a reasonable size. After taking out hot water use, we ended up using 5900kwh for heating (9500kwh including HW) in the past 12 months.

 

[theone8181]

Thats what i did last winter. I work from home and we have a 3 year old so we just heated the entire house to 18c 24/7 from November to April. House is a 23 year old, 140sqm so a reasonable size. After taking out hot water use, we ended up using 5900kwh for heating (9500kwh including HW) in the past 12 months.

Daft question but how do you know how much how water you've used?

 

[jonneymendoza]

Thats what i did last winter. I work from home and we have a 3 year old so we just heated the entire house to 18c 24/7 from November to April. House is a 23 year old, 140sqm so a reasonable size. After taking out hot water use, we ended up using 5900kwh for heating (9500kwh including HW) in the past 12 months.

Your lucky. 23 year old house so assumed it's very well insulated

 

[Gammawolf]

Daft question but how do you know how much how water you've used?

Our usage is pretty consistant all year round so, in the summer months since the heating is off the base load gas usage is almost exclusively hot water (with a tiny tiny bit for hob). So extrapolated out those are the figures we get for hot water usage.

Your lucky. 23 year old house so assumed it's very well insulated

I wouldn't say "very well insulated" by modern standards, but more "well insulated". It has standard (original) upvc double glazing throughout, cavity insulation via the small white fluffy stuff, and loft insulation thats 200mm (which was compacted to 100m in the central section by a previous owner to board out), our south wall has no windows so we don’t have optimal solar gain either. It probably benefits from less bridging and overall drafts from a house retrofitted with that

 

[theone8181]

Our usage is pretty consistant all year round so, in the summer months since the heating is off the base load gas usage is almost exclusively hot water (with a tiny tiny bit for hob). So extrapolated out those are the figures we get for hot water usage.



I wouldn't say "very well insulated" by modern standards, but more "well insulated". It has standard (original) upvc double glazing throughout, cavity insulation via the small white fluffy stuff, and loft insulation thats 200mm (which was compacted to 100m in the central section by a previous owner to board out), our south wall has no windows so we don’t have optimal solar gain either. It probably benefits from less bridging and overall drafts from a house retrofitted with that

Ahh good thinking. Just checked mine and its around 2500kwh for HW and 7500kwh for CH. Our house is slightly smaller than yours at 120 sq m. Our house is a similar age, built in 96, it is detached not sure if yours is.

 

[SoliD]

After insulating the first floor and it being so successful, i've now had enough time off to start the next phase which is insulating under the floor. First load of insulation turned up today, planning 100mm Celotex in between the joists and a further 100mm (potentially up to 150mm) eps70 underneath. This should do a couple of the downstairs room, and give me practise before moving to the kitchen/diner and doing the same but with the added install of UFH.
First

 

[jpaul]

First load of insulation turned up today, planning 100mm Celotex in between the joists and a further 100mm (potentially up to 150mm) eps70 underneath. This should do a couple of the downstairs room, and give me practise before moving to the kitchen/diner and doing the same but with the added install of UFH.

i didn't understand - you currently have joists, with what insulation, on ground floor then (versus concrete slabs/insulation/screed ) or, is some of that for the upstairs floors & ceilings - it's an 80s build ?

 

[SoliD]

Currently have a suspended timber floor, so 4inch deep joists at 400mm gaps, I then have about 40cm below this in the void below the house, so i'll be able to add more insulation under the joists. It's house built in 1969, so basic cavity downstairs.

 

[jpaul]

OK - I had recalled the pictures you'd put up for upper storey wall internal cladding ...
Have you consulted with neighbours/experts then on the best practice for joists to ensure they have sufficient ventilation/vapour barriers .. sounds similar to what dlockers had documented in his thread though.

 

[-Ad-]

Currently have a suspended timber floor, so 4inch deep joists at 400mm gaps, I then have about 40cm below this in the void below the house, so i'll be able to add more insulation under the joists. It's house built in 1969, so basic cavity downstairs.

Stop wasting money that will never achieve ROI

100mm of Celotex between your ground floor joists is plenty. Focus on sorting ventilation leaks around windows, doors, skirtings etc as that'll have a much larger effect than OTT extra UF insulation.

 

[SoliD]

Stop wasting money that will never achieve ROI

100mm of Celotex between your ground floor joists is plenty. Focus on sorting ventilation leaks around windows, doors, skirtings etc as that'll have a much larger effect than OTT extra UF insulation.

Not so much about ROI, but additional comfort, the polystyrene is a pittance compared to Celotex anyway, be less than £250quid to add the extra 100mm and figure if everything is up I may as well do it in one hit, but the extra will be necessary for UFH and minimising heat lost downwards and i'd rather make sure I get it right just with insulation before I go about chucking screed into the mix. Floor will be sealed fully and have done all I can to resolve draughts and leaks. I'm about 400quid better off like for like just from the upstairs 50mm celotex.

OK - I had recalled the pictures you'd put up for upper storey wall internal cladding ...
Have you consulted with neighbours/experts then on the best practice for joists to ensure they have sufficient ventilation/vapour barriers .. sounds similar to what dlockers had documented in his thread though.

Enough information out there to ensure i'm doing it right, basically as long as the joists have room to breathe which they will from below and then the vapour barrier will be the celotex, taped and sealed across the tops of the joists.

 

[dlockers]

Not so much about ROI, but additional comfort, the polystyrene is a pittance compared to Celotex anyway, be less than £250quid to add the extra 100mm and figure if everything is up I may as well do it in one hit, but the extra will be necessary for UFH and minimising heat lost downwards and i'd rather make sure I get it right just with insulation before I go about chucking screed into the mix. Floor will be sealed fully and have done all I can to resolve draughts and leaks. I'm about 400quid better off like for like just from the upstairs 50mm celotex.


Enough information out there to ensure i'm doing it right, basically as long as the joists have room to breathe which they will from below and then the vapour barrier will be the celotex, taped and sealed across the tops of the joists.

You say get it right but there is no single professional body recommending 100mm of PIR and 100mm of polystyrene afaik

 

[SoliD]

Need 90mm of PIR to get a u value of 0.25 for modern building regs iirc, and even that will just leach heat with UFH. EPS does such a similar job to PIR just without the foil and for extra space, hence it's ideal for adding underfloor if you have the space. Just look at how u value requirements have increased over the years, this will be the same for underfloor, I know as I'm retrofitting it's not required, but for the price uplift of adding EPS whilst I've gone to the trouble of getting all the floorboards up I may as well add it and as I say it's not necessarily required for the lounge and hallway, but in the kitchen/dining where i'll be adding UFH, the more you can get the better so I want to make sure what I'm doing is right and any mistakes I make can be corrected long before I start adding in the complexity of the UFH.

 

[-Ad-]

Heat will "leach" as you say it, through metres of insulation if there's a temperature differential.

Also, if you have an air space below the suspended timber floor, you want the joists to have access to airflow. Sealing them up in a load of polymer insulation is not best practise.

Ideally you'd use a breathable insulation between the joists and a vapour permeable membrane.

But as you're doing UFH, then just putting in joists depth Celotex and sitting the pipes on that would work also, albeit not best practise.

Another thing to consider is, how are you controlling the UFH and are you on a gas boiler or heating pump? Ideally, with either of those, you should remove UFH zones and allow the system to work on weather compensation according to the heat loss of the rooms/house as a whole and size the emitters (UFH/rads) appropriately.

 

[Bug One]

Got my first bill through since switching gas to Octopus tracker tariff.

This time last year I paid £125 for gas and £113 for electric - with solar, an EV and a diesel car (spending about £250 a month in diesel).

This year, with IOG and tracker, I paid £53 for gas and £94 for electric - with solar + battery, and both cars being EVs - doing the same amount of driving.