help with heat calcs

[Mike_scotland]

Just now, ProDave said:

Gas will be going up as well in April, quite likely in % terms more than electricity.  Apparently we will know the new cap figure tomorrow.

what Insulation do you have in your place Dave?

[ProDave]

6 minutes ago, Mike_scotland said:

what Insulation do you have in your place Dave?

Pretty much everywhere, walls, floor and roof, 300mm of either Frametherm 35 or Wood Fibre on the outside of the walls and roof.  Typical U values of all surfaces 0.14, triple glazed Rationel windows typical Uw 0.9  Air tightness as tested 1.4 (I was hoping for better but the tester nearly wet himself at how good it was)  As built EPC with all actual values A94.  No vents anywhere, mvhr ventilation and one room sealed stove.  Under floor heating downstairs, UFH in bathrooms only upstairs, no heating in bedrooms. 1 1/2 storey 150 square metres total.

 

EPC over estimated energy usage by more than 3 times.  Jeremy's simple heat loss spreadsheet gave a very very much more accurate estimate and came close to the real heating load figures. 

 

From Jeremy's spreadsheet, total heat loss when +20 inside and -10 outside was about 2.5kW.  A 5kW ASHP heats the house and DHW nicely.

[Mike_scotland]

Just now, ProDave said:

Pretty much everywhere, walls, floor and roof, 300mm of either Frametherm 35 or Wood Fibre on the outside of the walls and roof.  Typical U values of all surfaces 0.14, triple glazed Rationel windows typical Uw 0.9  Air tightness as tested 1.4 (I was hoping for better but the tester nearly wet himself at how good it was)  As built EPC with all actual values A94.  No vents anywhere, mvhr ventilation and one room sealed stove.  Under floor heating downstairs, UFH in bathrooms only upstairs, no heating in bedrooms. 1 1/2 storey 150 square metres total.

 

EPC over estimated energy usage by more than 3 times.  Jeremy's simple heat loss spreadsheet gave a very very much more accurate estimate and came close to the real heating load figures.

WOW nice! i have triple glazed windows also not sure the u value yet, is Jeremys calculator easy enough to put in your details and get a rough usage?

[TW9]

42 minutes ago, SteamyTea said:

Or 600 quid if on gas.

They are letting us know tomorrow morning what the new rates are, and how they are going to subsidise the increases.

 

It's not £600. It's 25,000 kWh of gas (actually more because gas boilers aren't 100% efficient) which is well over £2,000 at current prices.

[SteamyTea]

18 minutes ago, TW9 said:

It's not £600. It's 25,000 kWh of gas (actually more because gas boilers aren't 100% efficient) which is well over £2,000 at current prices.

Whoops, missed a 1 at the beginning out.  I hate typing on my phone.

[JohnMo]

BER say DHW allowance for calculating should be 4kWh per day for 2.4 people.  So there is a big over estimate on DHW, unless you have bedding for about 10 people.

 

Did the people doing the heating calculation have the wall, floor and roof build up?  Also did they have your postcode for allocating degree days for the heating calculation?

[Mike_scotland]

18 minutes ago, JohnMo said:

BER say DHW allowance for calculating should be 4kWh per day for 2.4 people.  So there is a big over estimate on DHW, unless you have bedding for about 10 people.

 

Did the people doing the heating calculation have the wall, floor and roof build up?  Also did they have your postcode for allocating degree days for the heating calculation?

I assume so as my builder sorting it. Its a 4 bedroom 220m2 roughly. Just me my wife and 1 kid

[Mike_scotland]

Are all heat pumps the same? Output is output? 

[SteamyTea]

31 minutes ago, Mike_scotland said:

Are all heat pumps the same? Output is output? 

They are if the CoP, Temperatures and outputs are identical.

 

So basically no.  They all perform slightly differently at different temperatures.

And to make matter worse they have different controllers with different terminology.

 

Not wanting to teach my grandmother how to suck eggs, do you know the basics of how an ASHP works and what parameters change?

[Iceverge]

On 02/02/2022 at 16:57, Mike_scotland said:

hey were aiming for the standard 5 but were hoping for better it hasnt been carried out yet... 

i hope thats what you meant m8? 

 

 

What stage of the build are you at? 

 

 

[Mike_scotland]

1 hour ago, SteamyTea said:

They are if the CoP, Temperatures and outputs are identical.

 

So basically no.  They all perform slightly differently at different temperatures.

And to make matter worse they have different controllers with different terminology.

 

Not wanting to teach my grandmother how to suck eggs, do you know the basics of how an ASHP works and what parameters change?

 

[Mike_scotland]

43 minutes ago, Iceverge said:

 

 

What stage of the build are you at? 

 

 

Plastering just finished

[SteamyTea]

@Mike_scotland

There was no response, just my quote.

[Iceverge]

29 minutes ago, Mike_scotland said:

Plastering just finished

Internally?

 

Even so it's not too late to have a remedial go at some extra airtightness. Make a DIY blowerdoor. Plenty of examples of you search on here. 

 

Get some silicon and go room by room and spend a day sealing leaks. It will help tremendously. 

[Iceverge]

32 minutes ago, Mike_scotland said:

Plastering just finished

Internally?

 

Even so it's not too late to have a remedial go at some extra airtightness. Make a DIY blowerdoor. Plenty of examples of you search on here. 

 

Get some silicon and go room by room and spend a day sealing leaks. It will help tremendously. 

[ReedRichards]

It's such a pity that you are new build and cannot get RHI.  Not just for the money but because you are obliged to use an MCS accredited installer who is obliged to perform detailed heat loss calculations that tell you not only what the heat loss from your house will be but how much heat every room needs.  You are stuck with a builder who may or may not be making his calculations with the same degree of rigour.

[SteamyTea]

@Mike_scotland

Ask your builder for the room by room heat loss calculations.

[Mike_scotland]

1 hour ago, ReedRichards said:

It's such a pity that you are new build and cannot get RHI.  Not just for the money but because you are obliged to use an MCS accredited installer who is obliged to perform detailed heat loss calculations that tell you not only what the heat loss from your house will be but how much heat every room needs.  You are stuck with a builder who may or may not be making his calculations with the same degree of rigour.

He is mcs regiatered. I will get rhi.... hes the builder as i call him the owner of the company but he is a heating engineer to trade.

[ReedRichards]

An MCS registered installer should have some software that will perform the heat loss calculations.  In due course you should get a full report of the results, not just a summary.  If the right information is input then the conclusions should be broadly correct.  However some factors such as solar gain or wind chill are not taken into account.

[SteamyTea]

7 hours ago, ReedRichards said:

An MCS registered installer should have some software that will perform the heat loss calculations.

https://mcscertified.com/mcs-launch-new-improved-heat-pump-calculator/

 

 

[Mike_scotland]

8 hours ago, ReedRichards said:

An MCS registered installer should have some software that will perform the heat loss calculations.  In due course you should get a full report of the results, not just a summary.  If the right information is input then the conclusions should be broadly correct.  However some factors such as solar gain or wind chill are not taken into account.

Yeah i was just wondering if grant was a good make.

[ReedRichards]

5 minutes ago, Mike_scotland said:

Yeah i was just wondering if grant was a good make.

But not on this thread, you posted that question elsewhere.

[Nickfromwales]

1 hour ago, Mike_scotland said:

Yeah i was just wondering if grant was a good make.

I've been fitting their oil boilers for decades, never had a single failure. Very robust bits of kit. Am currently looking into their hybrid LPG and oil ASHP's for some clients builds which 'aren't quite there' in terms of airtightness / thermal detailing etc.

[ReedRichards]

Grant suggested I get a hybrid but then helped me to establish that it wasn't necessary.  These days you need to be able to adjust the choice between oil boiler mode and heat pump mode according to the relative prices of oil and electricity.  

[Nickfromwales]

9 minutes ago, ReedRichards said:

Grant suggested I get a hybrid but then helped me to establish that it wasn't necessary.  These days you need to be able to adjust the choice between oil boiler mode and heat pump mode according to the relative prices of oil and electricity.  

The controls / weather comp / when the oil or gas kicks in etc is one of the main topics I wish to discuss with their Tech Support guys, ( when I get 5 mins spare!!  ). Hoping for a degree of synergy on that front. In terms of when the hybrid kicks in, that will be nothing to do with prices of energy? That will be decided for you eg when the house is cold and the HP cannot get the house temp up so the burner will kick in to supplement / take over. Cost will be what whatever they will be, as you will simply need it to do whatever it needs to do, whenever it needs to do it, in order to maintain the desired internal room temps. You won't really be able to able to strategize that much tbh, so probably important to oversize the HP to make sure it does as much as it can before burning any fuel.