New boiler and radiators, should we go for underfloor heating?

[LDNRennovation]

The boiler and two tanks we have now need to be removed. We were hoping to replace it with a combi boiler for the hot water, but the fact we need new pipes and radiators makes me wonder - why not underfloor heating instead? Does anyone know more about this subject and what would you recommend?

[nod]

If you can add UFH the d so 

It’s cheaper to run than radiators and much more comfortable 

[marshian]

7 minutes ago, nod said:

It’s cheaper to run than radiators and much more comfortable 

 

I do get the more comfortable element but I'm not sure the cheaper to run is correct - You are replacing the heat loss of a property no matter what heat source is used the cost in energy will be the same - only time you are going to save is if the comfort factor allows you to run lower room temps (hence lower heat loss)

[LDNRennovation]

Thanks so much for your help!

 

There’s probably a fair amount of heat loss as it’s an older bungalow.

So do you run the UFH off the combi boiler or have electric ones. We were going to add solar panels.

[JohnMo]

16 minutes ago, LDNRennovation said:

Thanks so much for your help!

 

There’s probably a fair amount of heat loss as it’s an older bungalow.

So do you run the UFH off the combi boiler or have electric ones. We were going to add solar panels.

Electric UFH, you will be paying a second mortgage, about 4 to 5 times the cost of gas.

 

UFH isn't a small job, are you ok rising the floor. Any possibly getting the floor screed?

 

[nod]

1 hour ago, marshian said:

 

I do get the more comfortable element but I'm not sure the cheaper to run is correct - You are replacing the heat loss of a property no matter what heat source is used the cost in energy will be the same - only time you are going to save is if the comfort factor allows you to run lower room temps (hence lower heat loss)

It would be difficult to asses on our current build Due to the HP

But our previous build smaller than our current at 180m2 GF was really cheap to heat with a gas boiler and we never used the bedrooms radiators 

 

[Iceverge]

3 hours ago, LDNRennovation said:

Does anyone know more about this subject and what would you recommend

 

For any UFH you need lots of insulation in the floor or otherwise too much of the heat will be lost downwards. The more the better but start at 150mm PIR or 200mmEPS. This means digging up the existing ground floor and lots of labour. 

 

For an old leaky house you need high power heat emitters for quick response. Radiators are the easy way to do this. 

If you go for UFH you need to have it in a thin screed and closed spaced pipes. 

 

 

 

 

 

[Roger440]

Yes, insulation under the floor would be nice. But to dig up a perfectly servicable floor to insulate is unlikely to make any economic sense.

 

You could use an overlay system, but that can create knock on issues with the extra floor height.

 

Or, you can hire a machine to grind grooves in the floor and fit the UFH pipes into those. Yes, you will lose heat downwards, but you will be doing that with rads too to a lesser extent. If the floor is uninsulated, then its uninsulated. 

 

I will be cutting grooves. Even as a DIY job, in my small house, if be looking at £5k plus to dig up and insulate the floor and replace the concrete. Ill be dead by the time i see break even on digging up the floor in reduced heating costs.

 

I will say, having done UFH before, its so much better than rads, especially with an unisulated floor as you will always have colder air at floor level.  UFH will dispense with that.

[LDNRennovation]

Sound like a bad idea now I look through the options. We have a slab, no finished flooring. The effort to raise the floor or dig in seems too much I think. Maybe in the bathroom, but yeah, a lot to think about many thanks guys.

[JohnMo]

With a boiler

 

If you are set on a combi, a storage combi would give better hot water performance.

 

Then oversized the radiators so you run a max temperature of 45 or lower. Run either weather compensation or load compensation on a single zone, with simple TRVs on bedroom rads to limit room temp.

 

Ideally complete a room by room heat loss calculation to size radiators, not a plumbers thumb in the air guess.

Edited Thursday at 13:59 by JohnMo

[marshian]

9 minutes ago, LDNRennovation said:

Sound like a bad idea now I look through the options. We have a slab, no finished flooring. The effort to raise the floor or dig in seems too much I think. Maybe in the bathroom, but yeah, a lot to think about many thanks guys.

 

 

have a look at this

 

 

[SteamyTea]

First things first.

Do a heat loss model of your hows.  If you look around our Boffin's Corner, you will find a heat loss spreadsheet.

Once you have filled that in, you can change an element i.e. thermally better windows, more floor insulation, and then start to make decisions.

You can take your time doing this as we are currently heading out of the heatings season.

Learning a bit of school thermodynamics is helpful as well, it makes the terminology understandable.

A very useful thing to do do is to record your energy usage.  If you have Smart Meters this is easy, if not, then you can get meters, or even manually daily reads.

Data is so useful, hard to overstate just how much it helps.

 

[marshian]

1 hour ago, SteamyTea said:

First things first.

Do a heat loss model of your hows.  If you look around our Boffin's Corner, you will find a heat loss spreadsheet.

Once you have filled that in, you can change an element i.e. thermally better windows, more floor insulation, and then start to make decisions.

You can take your time doing this as we are currently heading out of the heatings season.

Learning a bit of school thermodynamics is helpful as well, it makes the terminology understandable

 

 

Definately this ^

 

1 hour ago, SteamyTea said:

A very useful thing to do do is to record your energy usage.  If you have Smart Meters this is easy, if not, then you can get meters, or even manually daily reads.

Data is so useful, hard to overstate just how much it helps.

 

Absolutely - it also helps to correlate energy usage with HDD data - that way you can see if any improvements you make to the insulation of the house or the way you schedule the heating has a positive impact

 

It is however a little bit of a rabbit hole and I'm way down there now

[JohnMo]

9 minutes ago, marshian said:

 

Definately this ^

 

 

Absolutely - it also helps to correlate energy usage with HDD data - that way you can see if any improvements you make to the insulation of the house or the way you schedule the heating has a positive impact

 

It is however a little bit of a rabbit hole and I'm way down there now

But to do this you first need to understand what the boiler does and doesn't do. You can make massive reductions to gas consumption just by running the boiler differently. I more than halved ours with no other changes.

 

Combi they tend to be big (generally massive, compared to heating duty) and sized purely on the basis of hot water. To get them to run well, you need a boiler with good modulation - most are rubbish. The higher the minimum output (at 35 degs) the bigger the water volume you need, so big radiators are good, zones are bad. A simple design is best, but designed well.

 

Your bog standard install will be high flow temperature, small radiators, lots of thermostats. Most boilers short cycle a lot, but knows or cares, they just lay the bills, because gas is pretty cheap.

[SteamyTea]

8 hours ago, marshian said:

It is however a little bit of a rabbit hole and I'm way down there now

Really

I have been digging down for a decade or more.

 

But worth it, considering that I was using 11 MWh.year^-1 when I moved here.

 

 

7 hours ago, JohnMo said:

But to do this you first need to understand what the boiler does and doesn't do

Not everyone has gas.

[marshian]

3 hours ago, SteamyTea said:

Really

I have been digging down for a decade or more.

 

 

 

Decade you say 😉 "Alice is that you"

 

 

Nice to meet someone equally down the rabbit hole

 

[JohnMo]

3 hours ago, SteamyTea said:

Not everyone has gas.

No, true, but discussion is about a gas boiler install, so pretty relevant.

[SteamyTea]

10 minutes ago, marshian said:

Nice to meet someone equally down the rabbit hole

 

Similar sort of savings I have made.

I wish I had started doing it seriously earlier in my life.

[JohnMo]

12 minutes ago, marshian said:

 

Decade you say 😉 "Alice is that you"

 

 

Nice to meet someone equally down the rabbit hole

 

Goes to show a couple of things

 

First if all boilers were installed and setup well, a big dent would be made to CO2 emissions without the need for a wholesale roll out of heat pumps.

 

Second if a fabric first approach was used for all properties would further mitigate emissions.

 

Plumbers need mandatory low temp heating training.

[marshian]

26 minutes ago, JohnMo said:

Goes to show a couple of things

 

First if all boilers were installed and setup well, a big dent would be made to CO2 emissions without the need for a wholesale roll out of heat pumps.

 

Second if a fabric first approach was used for all properties would further mitigate emissions.

 

Plumbers need mandatory low temp heating training.

You are “Preaching to the choir” @JohnMo

[DamonHD]

31 minutes ago, JohnMo said:

Goes to show a couple of things

 

First if all boilers were installed and setup well, a big dent would be made to CO2 emissions without the need for a wholesale roll out of heat pumps.

 

Second if a fabric first approach was used for all properties would further mitigate emissions.

 

Plumbers need mandatory low temp heating training.

I prefer the "understanding first" approach suggested by UCL:

 

https://journal-buildingscities.org/articles/10.5334/bc.388

 

Often putting a heat pump after simple cheap no-regrets fabric improvements will save more carbon.

 

Quote: "The extent of fabric improvement needed will therefore vary across the stock. In some cases, e.g. where apartments are dominant, the role of fabric improvement may be limited. A recent detailed evaluation of a stock of 33,300 homes (85% flats) in London suggested that fabric measures alone would only achieve a 13% cut in gas use, at a cost of GBP31,900 per dwelling ..."  Quote: "The largest additional upstream costs are likely to be in zero-carbon generation to accommodate the peak demand of a widespread shift to heat pumps. In addition, electricity networks in some places will need to be strengthened."  Quote: "Residential buildings are homes: they need to be healthy, comfortable and affordable. ... that points to a high short-term focus on fabric improvement for households on low incomes and in poor housing."  Quote: "... a review finds the optimal stock average energy demand reduction from fabric measures is likely to be 30--50%."

[JohnMo]

3 minutes ago, DamonHD said:

I prefer the "understanding first" approach suggested by UCL:

 

https://journal-buildingscities.org/articles/10.5334/bc.388

 

Often putting a heat pump after simple cheap no-regrets fabric improvements will save more carbon.

 

Quote: "The extent of fabric improvement needed will therefore vary across the stock. In some cases, e.g. where apartments are dominant, the role of fabric improvement may be limited. A recent detailed evaluation of a stock of 33,300 homes (85% flats) in London suggested that fabric measures alone would only achieve a 13% cut in gas use, at a cost of GBP31,900 per dwelling ..."  Quote: "The largest additional upstream costs are likely to be in zero-carbon generation to accommodate the peak demand of a widespread shift to heat pumps. In addition, electricity networks in some places will need to be strengthened."  Quote: "Residential buildings are homes: they need to be healthy, comfortable and affordable. ... that points to a high short-term focus on fabric improvement for households on low incomes and in poor housing."  Quote: "... a review finds the optimal stock average energy demand reduction from fabric measures is likely to be 30--50%."

But my first point is you could probably knock down the CO2 emissions by a big margin just by getting the boiler to run effectively and well within the condensation range.

 

@marshian I assume the fabric improvements started in 2010, to drop gas consumption, but the biggest change was good boiler running a low temps in an 

 

So fabric improvements about 30% gas savings.

New boiler low temperature install a further 40% saving after fabric improvements.

Total saving overall start to finish 65%

[marshian]

5 minutes ago, JohnMo said:

@marshian I assume the fabric improvements started in 2010, to drop gas consumption, but the biggest change was good boiler running a low temps in an

 

Actually before that - the data doesn't show a two storey extension we threw up on the back of the house increasing the footprint and increasing the number of external walls on two large rooms

 

It was built to building regs at the time so I expect a small increase in energy usage but I got a surprise it went up a lot

 

That set me on the path of improvements to fabric and optimisation of boiler (eventually replacing a boiler which was no longer well matched to the house heat loss and cycled like crazy)

 

5 minutes ago, JohnMo said:

@marshian So fabric improvements about 30% gas savings.

New boiler low temperature install a further 40% saving after fabric improvements.

Total saving overall start to finish 65%

 

I'm pretty sure it's 80/20 (fabric/boiler) - energy usage has actually gone up for 2025 (prob 10%)

 

I'm heating 24/7 with WC for CH and DHWP (previous to this I was heating to a schedule)

 

Room temps are higher than when I was heating to a schedule - comfort factor is much better

 

I'm now in the final stages of increasing loft insulation from 70mm to 370 mm (long story not for this thread) so I hope that next winter the benefits will show up in a reduction of energy usage

 

[DamonHD]

I absolutely agree about getting condensing boilers to actually condense.

 

Anyone who wants to take up my rad stickers idea (now that DESNZ and Ogfem might be a little more receptive than when shown last time, under the previous government) and run with it is very welcome - I simply do not seem to have time.

 

https://www.earth.org.uk/OperationTuneup/

 

~GBP1 per household raw cost, everything done by the householders, I have 2nd/3rd round prototypes sitting on my desk still.

[marshian]

2 hours ago, DamonHD said:

I absolutely agree about getting condensing boilers to actually condense.

 

Anyone who wants to take up my rad stickers idea (now that DESNZ and Ogfem might be a little more receptive than when shown last time, under the previous government) and run with it is very welcome - I simply do not seem to have time.

 

https://www.earth.org.uk/OperationTuneup/

 

~GBP1 per household raw cost, everything done by the householders, I have 2nd/3rd round prototypes sitting on my desk still.

 

I really like this idea - however when I was fine tuning my radiator flow rates I stuck matt black insulation tape on them so I could get a more accurate reading from the IR thermometer - Mrs Alien was not happy with "the look" so they didn't stay on there long - apparently they lost adhesion and she picked them off the floor and put them in the bin and I wasn't to do it again

 

 

The description

 

"Who is this for?
These instructions are for ONLY if you:
● Have a gas condensing combi boiler.
● Do NOT have a hot water tank.
● Have no one ill or very young or very old in your home.
● Are willing to help us with an experiment to help save gas."

 

Needs a bit of an update - they would also be suitable for any boiler set up with DHWP (with a HW Tank) and Weather compensated CH flow temps