Which ASHP?

[CalvinHobbes]

Jeez Our builder (a plumber) really has a bad opinion of ashp and says climate here is too damp and to use oil.  I am worried about the electric bills.Anyway I got a quote from suggesting we install a Grant Aerona³ R32   

What do you think of the brand? Oh it's 10kw

Edited April 9 by CalvinHobbes

[nod]

Like most on here I’ve had a Mitsubishi installed via the £7500 grant system 

Most plumbers do have a low opinion of  HPs 
Electricity is three times the price of gas So HPs are likely to be more expensive to run Or about the same in airtight UHH new build 

Someone will be along shortly singing the praises of HPs But you can’t get away from the cost of electricity 

 

 

[Andehh]

We get about 3.5 Cop (350% per unit of Elec, vs 95% per unit of gas) out of our Samsung ASHP, which combined with octopus cosy means we make a large saving vs gas.  We basically heat out house on 16p Elec, which makes it much cheaper then gas.

 

How well Insulated is your house? Are you running UFH or over sized rads?

Edited April 10 by Andehh

[dpmiller]

50 minutes ago, nod said:

Like most on here I’ve had a Mitsubishi installed via the £7500 grant system

you say that, but is it true?

[JohnMo]

49 minutes ago, nod said:

Like most on here I’ve had a Mitsubishi installed

Not sure that is true. I don't have one

 

7 hours ago, CalvinHobbes said:

 Grant Aerona³ R32   

What do you think of the brand? Oh it's 10kw

For your heat demands 10kW is way too big. Nothing wrong with the Grant units though. The 10kW unit puts out 11.1kW at 7 degs, you will most likely only need about 1kW.

 

Get the small one 6kW. 

 

Find a different plumber

 

 

 

 

[SteamyTea]

On 10/04/2024 at 06:30, nod said:

But you can’t get away from the cost of electricity 

You can't get away from the world electrifying either.

On 10/04/2024 at 06:51, Andehh said:

How well Insulated is your house

As a general note, the heat losses for the same building will be the same regardless of the thermal source.

You size your heating system to your building, not the other way around.

[nod]

3 minutes ago, SteamyTea said:

You can't get away from the world electrifying either.

As a general note, the heat losses for the same building will be the same regardless of the thermal source.

You size your heating system to your building, not the other way around.

Our previous build and hopefully this one is very well insulated and cheap to heat via a gas boiler and hopefully the HP will work out the same or a little bit more expensive 

What I don’t understand on here Is people installing UFH in the bedrooms on the upper floors While we have small rads in the bedrooms We have never needed to use them 

A well insulated home shouldn’t need much heating 

[SteamyTea]

3 minutes ago, nod said:

What I don’t understand on here Is people installing UFH in the bedrooms on the upper floors

I don't either (in a well designed new build).

I suspect it goes back to when we started getting natural gas in the late 1960's and early 1970's.  Houses then were pretty badly build and as the gas board was fitting thousands of central heating systems (we managed to fit gas system so I cannot understand why we cannot fit heat pumps at the same rate), a "one design suits most"  approach was taken.

This assumed that all rooms leaked energy at a fairly high rate and the worse that needed doing was fitting a larger radiator.

[Andehh]

11 hours ago, SteamyTea said:

You can't get away from the world electrifying either.

As a general note, the heat losses for the same building will be the same regardless of the thermal source.

You size your heating system to your building, not the other way around.

 

 

I don't disagree, but it's a quick way of warning people away when they answer it's not been Insulated since the 80s and their small radiators are scorching hot.... Just saves them the agro....

[CalvinHobbes]

I know people who have been in a new build passive house in the republic who are thinking of ripping out their ashp because of astronomical electric bills. Yes it's in likely badly but surely the house should be a decent temp without too much heat? 

[JohnMo]

21 minutes ago, CalvinHobbes said:

I know people who have been in a new build passive house in the republic who are thinking of ripping out their ashp because of astronomical electric bills. Yes it's in likely badly but surely the house should be a decent temp without too much heat? 

The two statements seem to be a contradiction. Don't need need much heat and astronomical to run a heat pump?

 

Basics are if your house needs 3kW at the design day, you need 24 x 3 is 72kWh. Via a panel heater at 30p per unit is £21 per per day. If you design day is -7 and you need 35 water flow, your CoP will be 2.8, so about £7.80.  Most other times both will.becway cheaper. Heat pump are either on all the time at a low rate or batch charging at an elevated temperature but only if yiu use a time of use tariff.

[joe90]

35 minutes ago, CalvinHobbes said:

been in a new build passive house

 

35 minutes ago, CalvinHobbes said:

ripping out their ashp because of astronomical electric bills.

Those two contradict one another. If it were a passive house heating should be minimal whatever the source OR the ASHP has not been designed properly or installed properly.

[SteamyTea]

8 hours ago, CalvinHobbes said:

I know people who have been in a new build passive house in the republic who are thinking of ripping out their ashp because of astronomical electric bills. Yes it's in likely badly but surely the house should be a decent temp without too much heat? 

They may be using a lot of DHW.

Or leaving windows open because they like fresh air.

 

Ask them what their bills are when they have gas fitted.

Edited April 12 by SteamyTea

[nod]

On 11/04/2024 at 07:17, SteamyTea said:

I don't either (in a well designed new build).

I suspect it goes back to when we started getting natural gas in the late 1960's and early 1970's.  Houses then were pretty badly build and as the gas board was fitting thousands of central heating systems (we managed to fit gas system so I cannot understand why we cannot fit heat pumps at the same rate), a "one design suits most"  approach was taken.

This assumed that all rooms leaked energy at a fairly high rate and the worse that needed doing was fitting a larger radiator.

Back in 2008 We did the plastering and rendering on a local site of 110 homes There was very little work about So I was glad to be asked to complete the first ten Just to see how sales went As the country and housing sales where on there arse 

It was the very first time I came across HPs Due to low running costs They sold like hotcakes All 110 complete in 18 months The owner told me that by the time he had received the grant it working out similar to fitting a gas boiler 

I’m sure why the same incentive isn’t offered or taken up now 

Just to add our installer has service contacts for 53 All still running fine 

[Iceverge]

On 11/04/2024 at 20:17, CalvinHobbes said:

I know people who have been in a new build passive house in the republic who are thinking of ripping out their ashp because of astronomical electric bills.

 

Passive or "Passive".

 

About 2 years ago, at a stag party, I was looking forward to an in depth chat about thermal bridging with and airtightness details with a man who introduced himself as a passive house self builder. 

 

Imagine my dismay when I learned he had double glazing,  hadn't done an airtightness test, had no idea what insulation levels were at. Turned out his living room was almost unliveable with all the glazing for most of the year. Too hot or too cold.   

[nod]

1 hour ago, Iceverge said:

 

Passive or "Passive".

 

About 2 years ago, at a stag party, I was looking forward to an in depth chat about thermal bridging with and airtightness details with a man who introduced himself as a passive house self builder. 

 

Imagine my dismay when I learned he had double glazing,  hadn't done an airtightness test, had no idea what insulation levels were at. Turned out his living room was almost unliveable with all the glazing for most of the year. Too hot or too cold.   

Passive and high bills seams to be a bit of a contradiction 

[ADLIan]

15 hours ago, nod said:

Back in 2008 We did the plastering and rendering on a local site of 110 homes There was very little work about So I was glad to be asked to complete the first ten Just to see how sales went As the country and housing sales where on there arse 

It was the very first time I came across HPs Due to low running costs They sold like hotcakes All 110 complete in 18 months The owner told me that by the time he had received the grant it working out similar to fitting a gas boiler 

I’m sure why the same incentive isn’t offered or taken up now 

Just to add our installer has service contacts for 53 All still running fine 

 

Back in the early 2000s (cannot remember exact dates) there was a loophole in the Building Regs that allowed the efficiency of heat pumps to meet the CO2 emission standards whilst allowing cr*p levels of insulation and airtightness perhaps as bad as the backstop values. Heard of developers using this method and dread to think what bills the house owners were left with. The additional costs, compared to gas heating, was very obvious in the EPCs.

[Iceverge]

Like lots of low energy builders I got completely bogged down by deciding on a heating system for our passive house. 

 

In the end I said "stuff this" to all the salesmen and opted for no heating. 

 

We use an electric resistive rad. I put some pull string patio heater style heaters in two bathrooms and a fan heater in the other for a bit of post shower comfort. 

 

I have no regrets about not opting for a full central heating system. 

 

However electric UFH just under the tiles would be nice in the bathrooms for little cost. 

 

I should really have made more provision for "just in case" but I had lost patience with the confusion and cowboy prices.

 

That means:

 

UFH pipes, Pipes for radiators, UFH resistive wires, a duct for an ASHP, a wall duct for A2A, A fused spur for a storage heater.

 

Do one or two of these and then pour every other penny into the fabric and airtighess. When the house settles in 2 years you'll be able to make an economical and effective decision. We're putting in an A2A to cut the electric bills a bit. 

 

 

 

 

[joe90]

Well I went ASHP due to lack of mains gas and seeing oil being fazed out, although well insulated not quite up to passive standards and the fact I found a cheap EBay heat pump and basically copied Jeremy’s instal. Electric towel rads for the bathrooms. At least the UFH loops were there for any other kind of heating In The future. I would have added solar panels had I stayed there (dont ask!,!)

[MikeSharp01]

18 minutes ago, joe90 said:

had I stayed there (dont ask!,!)

We are all sorry for your loss Joe

[joe90]

21 minutes ago, MikeSharp01 said:

We are all sorry for your loss Joe

Aw thanks, life’s better now thanks in my little Forest cottage STRESS FREE!!,!

[ProDave]

2 hours ago, Iceverge said:

Like lots of low energy builders I got completely bogged down by deciding on a heating system for our passive house. 

 

It is not difficult.  I put all the details of my house into Jeremy's heat loss spreadsheet, and it told me at +20 inside and -10 outside my house needed a little over 2kW of heat input.  That was not exactly difficult therefore to specify a 5kW ASHP, about the smallest generally available.  And it is working fine.

 

Before actually buying the ASHP I ran a convector heater for a week, plotting inside and outside temperature and that confirmed the heat loss was in line with the calculations.

[Iceverge]

8 hours ago, joe90 said:

Well I went ASHP due to lack of mains gas and seeing oil being fazed out, although well insulated not quite up to passive standards and the fact I found a cheap EBay heat pump and basically copied Jeremy’s instal. Electric towel rads for the bathrooms. At least the UFH loops were there for any other kind of heating In The future. I would have added solar panels had I stayed there (dont ask!,!)

 

This post says a tremendous amount. 

 

Passive standard gives fairly random number. The complete purist who wants only to heat their house to exactly 20⁰ with a MVHR  post heater doesn't exist in reality. Most of us are happier a little colder or warmer in reality. Passivhaus ignores this. 

 

Copying someone else who has done all the hard work and arrived at the best solution is a trait that should be applauded. It's a great use of brain power. 

 

Cheap ASHPs make perfect sense. 

 

A low cost insurance of UFH pipes for the "just in case" is well worth it.

 

Also despite best planning and hopes life changes sometimes. It's only a house in the end, don't worry too much about it. 

[ProDave]

The other "trust the theory" thing, is from the experience of others, I believed my house would be well insulated enough not to need any heating upstairs.  So I didn't for any in the bedrooms.  Instead I fitted an electric point on the wall of each bedroom for a panel heater if they proved to be too cold.  I have never needed to fit those panel heaters and the points for them remain unused.

[JohnMo]

Our last house was originally built in 1830, some insulation improving done but not much. It was a heat sieve, we never had bedrooms heated, our bedroom window was open 360 days a year, a few very cold nights closed.