Which heating and hot water solution(s) in 2024?

[MrPotts]

2 minutes ago, Iceverge said:

 

What about thermal comfort and noise. 

Again this is just what I have read but increased thermal comfort and reduced noise level do not justify the increased cost.

Edited May 2 by MrPotts

[JohnMo]

1 hour ago, joe90 said:

I was told by my plumber who signed off my tank not, it must be visible to be “venting”, was he wrong?

An approved detail

 

 

TN 10321 - Condensate drainage and unvented hot water systems FD.pdf

[JohnMo]

14 minutes ago, MrPotts said:

From what I have read the additional cost doesn’t justify triple glazing over double glazing.

I read all that when designing our house. Then looked at calculations for inside surface temperature - triple glazed was something like 1 to 2 degrees below room temperature, while double was nearer 10. Passivhaus specify triple glazed not just because of heat loss, (in fact they are not really required for heat loss at all) but are required for the comfort criteria.

 

 

[sharpener]

That Hep2O is the one I have got. The back pressure is IMO unacceptable, I have now got it at the bottom of a vertical drop of >2m of 22mm Cu pipe and it still backs up to the tundish. When I have had it apart it all appears clean and undamaged. I test the relief valve at least twice a year when I reset the timers in the a/c, as upthread I have otherwise stopped worrying.

 

Edited May 2 by sharpener

[JohnMo]

12 minutes ago, MrPotts said:

reduced noise level do not justify the increased cost.

Depends on circumstances and house layout, plus size of windows.

 

We have one wall of glass 6m tall and 7m wide. Biggest heat loss of the whole house is that wall. Halving the heat loss was money well spent (1.4 compared to 0.7 U valve), plus at -7 I can quite happily sit right next to glass without discomfort.

[Iceverge]

4 hours ago, MrPotts said:

Again this is just what I have read but increased thermal comfort and reduced noise level do not justify the increased cost.

 

What kind of increased created costs have you been quoted? 

 

Often the uplift from 2g to 3g is bundled in with a different frame of much higher specs too so be wary of comparing apples to apples. 

 

My neighbour paid a premium of €800 for 3G over 2G in their house of 220m2. Same good performance frames, just different glazing units. 

 

 

[SteamyTea]

8 hours ago, JohnMo said:

However for the same size of cylinder an unvented cylinder delivers way more usable water

I have heard/read this many times.

I accept that a secondary heat exchanger has a temperature drop across it, it could not deliver power otherwise.

Bur just as an energy store I cannot see how there is a difference.

SHC x Mass X delta T minus standing losses should work out the same.

[JohnMo]

4 hours ago, SteamyTea said:

I have heard/read this many times.

I accept that a secondary heat exchanger has a temperature drop across it, it could not deliver power otherwise.

Bur just as an energy store I cannot see how there is a difference.

SHC x Mass X delta T minus standing losses should work out the same.

On an UVC the thermocline rises up the cylinder as hot water is consumed. The hot water coming out when nearly depleted is still usable as hot water.

 

On a thermal store the thermocline will operate in the same way, climbing up the cylinder, but leaving more and more of the coil in warm to cold water.  So not getting the heat transfer. A plate pack helps as you get more useable hot water.

 

The other issue can be, you may have to heat the thermal store via coil or plate exchanger also, as with a lot of boilers, nearly all heat pump needs a closed pressurised system to work with. This just makes less usable stored heat as now you operate via two heat exchangers.

Edited May 2 by Nickfromwales
typo

[JamesPa]

40 minutes ago, SteamyTea said:

SHC x Mass X delta T minus standing losses should work out the same.

In addition to (or possibly another way of looking at) what @JohnMo says you can't usefully extract all the stored energy from a thermal store because, once all of it is below the desired output temp, the remaining energy can't be transferred to the outgoing stream (unless of course you were to fit a small water to water heat pump).  Effectively useful deltat is less, unless the thermal store is very hot.

Edited May 2 by JamesPa

[SteamyTea]

23 minutes ago, JohnMo said:

On a thermal store the thermocline will operate in the same way, climbing up the cylinder, but leaving more and more of the coil in warm to cold water

That makes sense, never thought of it that way.

Nice seeing the word 'thermocline' instead of 'stratification', which is a very rare phenomenon in fluids.

11 minutes ago, JamesPa said:

once it's all of it is below the desired output temp, the remaining energy can't be transferred to the outgoing stream

Yes.

True will all storage, Evan a flat battery will have some voltage in it.

12 minutes ago, JamesPa said:

unless of course you were to fit a small water to water heat pump

Often thought that more use of small W2WHPs could be made.

Get a lot of energy turning water ice to liquid water.

[Nickfromwales]

9 hours ago, Iceverge said:

 

The best bang for your buck in terms of energy saving + comfort is.

 

1. Airtighness 

2. MVHR

3. Triple glazing 

 

Have you considered higher quality uPVC 3g windows. Something like Veka 82 or Kommerling 88 or Gealan S7000.  They're both the cheaper and better performing than almost any aluminium or timber window. 

 

I'm going to pull a figure out of thin air here of a heating demand of 40kWh/m²/annum and a peak heating load of 20W/m². Say you're 200m² then that's 4kW. A 5 to 8kW heat pump would work well. 

 

My recommendation is a monoblock ASHP with single zone UFH on the ground floor only in 1 zone and a 300l UVC. Electric UFH just under the tiles in all bathrooms including those already with wet UFH. Maybe @Nickfromwales can disagree. 

Nope, bang on the money, if points 1,2 & 3 are addressed. I only go to individual zones on a single floor when it's a large dwelling and the effects of solar gain are notable. One certified PH I did was 20oC in the East side of the open plan living space in the morning, whilst the master bed on the West was at 14oC, ergo it needed zones to balance this out (with just a smidge of targeted auxiliary heating).

[Jane W]

On 02/05/2024 at 12:20, MrPotts said:

From what I have read the additional cost doesn’t justify triple glazing over double glazing.

I agree. I have actually had a quote that is cheaper than the rest for triple, also significantly cheaper for double glazing. But when talking to the sales people about airtightness and thermal bridging they seemed a bit dismissive so wondering about their fitters also being dismissive about the important detailing...🤔

[Jane W]

Thank you, that setup is of interest. Have you any thoughts on a diversion to heat the supply air in the mvhr, similar to Denby Dale. I know it was used to reduce short cycling there but presumably it could also work with an ashp. I wonder how effective that would be?

[JohnMo]

12 minutes ago, Jane W said:

thoughts on a diversion to heat the supply air in the mvhr, similar to Denby Dale

You have to be careful anything more than 10W/m2 at passivhaus airflow rates as the air starts to smell of burning apparently. Assume 200m2 house that's about 2kW. A better way is decent amount of screed and you can easily dump at a rate of 6kW in to the same floor area. Adding control to manage the air flow heating is just another layer of complexity. 

 

Thick screed, heat source, 3 port valve, UFH manifold with no actuators. Thermostat to start heat source.  If you need over temp protection a pipe stat to remove heat source permissive or close a two port valve (or both ideally)

[Jenki]

On 02/05/2024 at 11:13, joe90 said:

I was told by my plumber who signed off my tank not, it must be visible to be “venting”, was he wrong?

 

you need to be able to see either the Tun dish, or the discharge point. you don't need to see both to be compliant.

[Nickfromwales]

18 minutes ago, Jenki said:

 

you need to be able to see either the Tun dish, or the discharge point. you don't need to see both to be compliant.

Yup. 👍. 

[Nickfromwales]

1 hour ago, Jane W said:

Thank you, that setup is of interest. Have you any thoughts on a diversion to heat the supply air in the mvhr, similar to Denby Dale. I know it was used to reduce short cycling there but presumably it could also work with an ashp. I wonder how effective that would be?

Diversion of excess solar?
 

So, if you need heating, it’ll not be a sunny day, ergo most if not all of anything you produce from an average sized array will be sucked up by the house base loads and possibly a bit of DHW    

Solar > space heating = no dice. 

[Nickfromwales]

55 minutes ago, JohnMo said:

You have to be careful anything more than 10W/m2 at passivhaus airflow rates as the air starts to smell of burning apparently.

This is interesting, as I sit by a 1kW fan heater when at my desk in my office (big uninsulated shed with a desk one end where I hide from wife & kids) and there is no such smell of ‘burning’, just it’s horribly targeted crude heating when it’s pointed at my feet / legs and left to ‘rise’. 
 

Strangely, in ductwork it does seem to be an issue, but maybe that’s because the airflow rate is tiny with MVHR where my little fan blower is going at a decent rate of knots. 🤷‍♂️. 

 

FWIW, I wouldn’t dream of electrically heating airflow into a domestic residence, just horrible, plus the MVHR outlets are typically up high (and heat rises) so is counter to ‘the laws of physics’. 

[Nickfromwales]

1 hour ago, Jane W said:

I agree. I have actually had a quote that is cheaper than the rest for triple, also significantly cheaper for double glazing. But when talking to the sales people about airtightness and thermal bridging they seemed a bit dismissive so wondering about their fitters also being dismissive about the important detailing...🤔

Double glazing is basic level stuff, and not really any kind of standard to look up to. They’re not often well detailed, airtight, plus longevity of mechanisms and seals is a big concern. 
 

Fitters can be good or bad, and when I had my front door and windows renewed, by my good friend, he looked blankly as I fully filled the sides / cavities with airtight closed-cell foam. He told me it was pointless, I said just keep fitting the windows and uncle Nick will make it all good. 😊.

 

Discussing thermal bridging with these types of folk will often fail to get you more than a blank stare.

[JohnMo]

4 minutes ago, Nickfromwales said:

He told me it was pointless, I said just keep fitting the windows

Makes you wonder, they would install single glazed given half a chance, and still leave a big gap and make it look pretty with a big dollop of silicone or a bit of trim.

[Nickfromwales]

44 minutes ago, JohnMo said:

Makes you wonder, they would install single glazed given half a chance, and still leave a big gap and make it look pretty with a big dollop of silicone or a bit of trim.

Yup. Sad, but true, as they’re just not told by any governing body that there’s a different way.

Pretty terrible in 2024 tbf. 

[SteamyTea]

1 hour ago, Nickfromwales said:

wouldn’t dream of electrically heating airflow into a domestic residence

Works ok with storage heaters, the air exits at about 85⁰C from mine.

[G and J]

1 hour ago, Nickfromwales said:

Diversion of excess solar?
 

So, if you need heating, it’ll not be a sunny day, ergo most if not all of anything you produce from an average sized array will be sucked up by the house base loads and possibly a bit of DHW    

Solar > space heating = no dice. 

I guess I’m thinking of our own situation but if there is an ASHP why not use that to efficiently use Solar PV to do free UFH and/or DHW? (Or isn’t it that simple?)

[Gone West]

2 hours ago, JohnMo said:

You have to be careful anything more than 10W/m2 at passivhaus airflow rates as the air starts to smell of burning apparently.

IIRC, the smell of burning is caused by a duct air temperature of more than 50C, which burns the dust in the duct and causes the smell. I think our EASHP kept the air around 40C.

[severnside]

I would recommend ducted or split A2A heating with Direct UVC. Almost instant heating, very efficient and room level control. It would provide cooling in summer as well.

we are pleased with ours