Energy Ideas

Hi Steamy.

 

Having a bit of trouble opening your spreadsheet. 

 

Have tried it in Excel 2024 using the "all files option" Says the file is corrupt. Tried it in Excel 2013 version using the all files option, says it's protected with a password so won't open. 

@Gus Potter

 

Seem to remember that JohnMo had a similar problem, must be Scotch Software.

 

This, it is saved as an .xlsx file.

 

Compare U-Values and ACH.xlsx

Hiya. Can open it a bit in excel 2024, but it is stripping out a lot of info I think? Tried again with an earlier version of excel but most of the cells are not referencing. The charts are blank.

 

From what I can see you have put in a pile of effort into this. It's not a five minute job, it must have taken a huge effort to develop this. 

 

It looks like a good tool. 

 

It may be a "jock" problem at my end" but I doubt it. Ask around and see what others say.. you do know why the animal called the Haggis has it two left legs shorter.. it's so the can run round a hill and still stay level! 

 

 

 

 

15 minutes ago, Gus Potter said:

Can open it a bit in excel 2024

 

Both the ods and xlsx file work fine in LibreOffice calc.

 

Best thing to do is download and install a copy of libre office - https://www.libreoffice.org/

 

But beware, once you start using it instead of Excel, you may never go back 😁

 

Now need to do some interpretation.

38 minutes ago, SimonD said:

But beware, once you start using it instead of Excel, you may never go back 

And that is a big problem I have at my end as a practicing SE. I have written spreadsheets that have stiffness matrices ( the maths can be challenging) for example that I use for analysis of whacky stuff. These are benchmarked and tested against industry standard analysis software. Basically I write these and check, validate and so on. These are then sent to other SE's for checking. It also works the other way when I act as a checking SE. 

 

On a commercial level ( yes I know I'm captured) it make no sense to swap to libre whan I can get excel for a couple of hundred quid. 

 

The excel platform is also very powerfull in the text function / interface.. how it interacts with many cad packages for example. SE use a lot of Greek and other symbols.. we can't be mucking about with these as they are really important in their meaning. 

 

But to cut to the chase. I can see @SteamyTea has put a pile of work into this. Many BH folk will have excel say at work? 

 

So it would be great if @SteamyTea's spread sheet could be converted into something that your average punter can open at ease. 

 

 

 

 

@Gus Potter @SimonD

 

I use Libreoffice Portable https://portableapps.com/apps/office/libreoffice_portable

Can take it anywhere with me.

 

The problem may be that I used REGEX() to split up the array's columns and rows headings, not sure if Excel supports REGEX() (it should as it is a normal function in the IT world).  

 

I did think of one problem and that is when using MVHR, the result should be added to the ACH result as it is, in effect, and extra 'leak'.

 

This part was not a great deal of work.  I may try and make one that separates the 'ground' face of the cuboid and adds in some percentage of window area.

22 hours ago, Gus Potter said:

And that is a big problem I have at my end as a practicing SE. I have written spreadsheets that have stiffness matrices ( the maths can be challenging) for example that I use for analysis of whacky stuff. These are benchmarked and tested against industry standard analysis software. Basically I write these and check, validate and so on. These are then sent to other SE's for checking. It also works the other way when I act as a checking SE. 

 

On a commercial level ( yes I know I'm captured) it make no sense to swap to libre whan I can get excel for a couple of hundred quid. 

 

The excel platform is also very powerfull in the text function / interface.. how it interacts with many cad packages for example. SE use a lot of Greek and other symbols.. we can't be mucking about with these as they are really important in their meaning. 

 

I know the dilemma well. I actually used to work in Microsoft back in the 1990s. I have a dual boot system and spend most of my time on Linux with LibreOffice, but then boot up on Windows and use Excel only when I absolutely have to. It makes life a bit of a pain, but for me it's worth it.

 

16 hours ago, SteamyTea said:

I did think of one problem and that is when using MVHR, the result should be added to the ACH result as it is, in effect, and extra 'leak'.

 

Ventilation losses are a big problem for the whole industry. Unless you've got the results from a blower or pulse test, it's pretty much guesswork anyway and then you've got just a few options on methodology - you've got SAP based on storey height, location, exposure etc. or BS EN 12831-2017 or CIBSE methods and they usually treat MVHR differently so I'm not sure MVHR would correctly be an extra leak on top of ACH. 

8 hours ago, SimonD said:

Ventilation losses are a big problem for the whole industry. Unless you've got the results from a blower or pulse test, it's pretty much guesswork anyway

Two things arise in my head from this - I may have missed something as I did have some wine last night. Firstly, if it is a big problem why has it not been sorted out - stupid to ask I guess but hey. Secondly, if you do have a blower test result then surely the leakage must add to the MVHR losses and be a calculate fraction assuming the MVHR holds the pressure difference roughly constant. From this it must follow that you can reduce the MVHR setting by the pressure test ACH when you are setting up the MVHR as part of the ventilation strategy. Might this then go some way to explaining why people find that when using MVHR they can back off the flow rate and still be comfortable because all they have done is got to the regulation ACH flow rate including the fabric losses. 

But leakage @50Pa would be much much more than leakage in normal conditions surely?

2 hours ago, MikeSharp01 said:

Firstly, if it is a big problem why has it not been sorted out - stupid to ask I guess but hey.

 

That's a very good question. I simply don't know. In my heat loss calcs I keep on going back to ventilation like a revolving door to find more accurate answers to more accurately calculate ventilation losses, but we know that standardised heat loss calculation methods almost invariably over-estimate ventilation losses. And the industry is set up to lock us in to the proscribed methods. If you deviate from the national figures, you have to be prepared to provide a rationale for the deviation, especially when it comes to retrofit.

 

2 hours ago, MikeSharp01 said:

Secondly, if you do have a blower test result then surely the leakage must add to the MVHR losses and be a calculate fraction assuming the MVHR holds the pressure difference roughly constant. From this it must follow that you can reduce the MVHR setting by the pressure test ACH when you are setting up the MVHR as part of the ventilation strategy. Might this then go some way to explaining why people find that when using MVHR they can back off the flow rate and still be comfortable because all they have done is got to the regulation ACH flow rate including the fabric losses. 

 

So again, this is more complicated the it first seems. Yes, assuming that the MVHR system does not impact pressure, then it would be in addition to infiltration. But from a ventilation heat loss perspective, it would be wrong to assume this simple addition given that, 1 the industry standards tend to over-estimate infiltration ventilation losses anyway, and 2 the effectiveness of the MVHR system. MVHR systems can suffer the same fate as heating systems in that many are over-sized (I know from data that this was definitely the case a while back and I would hope the situation has improved). The question then remains in each individual case as to the flow regime within the heat exchanger. If it is in the transitional or laminar state, then the efficiency of the MVHR is greatly reduced, which obviously impacts the ventilation losses significantly. Now if someone finds that they back off the flow rate after installation, they'll still get the benefit of fresh air, but without all the benefit of heat recovery. Obviously there are systems that deal with this by cutting off flow to parts of the heat exchanger to maintain turbulent flow, but tbh, since I decided to go the natural ventilation direction I haven't followed the MVHR market for about 5-6 years, so don't know the current market situation, but I would cynically doubt that this function has become a standard. Maybe I'm wrong?

 

 

17 minutes ago, dpmiller said:

But leakage @50Pa would be much much more than leakage in normal conditions surely?

 

Yes, but there is a rule of thumb to divide this (q50) by 20 to arrive at a leakage rate under normal conditions.

On 24/02/2026 at 05:06, SteamyTea said:

This part was not a great deal of work.

From what I could see it look like a very useful tool. You are being bashfull! It's not something you knock up and check in an hour or so!

2 minutes ago, Gus Potter said:

not something you knock up and check in an hour or so

Was about 2 hours, over a coffee, but 45 years of studying.

1 hour ago, SteamyTea said:

Was about 2 hours, over a coffee, but 45 years of studying.

I'm very impressed from what I could see. It took you two hours!.. well you are sharp as a tack. No way could I have churned that out in two hours.. even the small bit I can see. 

 

You're probably a bit like me.. as an SE / desinger I spend most of my time thinking and how I'm going to communicate the information so everyone can understand it, lots of folk are reluctant to pay for that. I know I have to produce structural calculations.. which after a while are not that envigorating when doing day to day stuff. I like maths but up to a point and get excited when I have to design whacky stuff. You are more adapt and nimble at high level maths than I. 

 

Far all. The idea is that you do the thinking, plan out how you are going to set up the calculation pack do the supporting drawings, bite the bullet and just get on with it. Then you have to check your sums and design philosophy is still valid. 

 

Is there any way you can make it idiot proof at my end so I can open it in excel? 

 

The reason for me pressing is this.

 

When I joined BH it was as a result of a prompt. At the time Jeremy Harris (JH) was someone that floated my boat, he popped up again a while back but then went back into retirement. His thermal loss spreadsheet must have been used by many thousands of folk. Life has moved on but your spreadsheet has, from what I can see has potential. It's something that I would want to interrogate, see where the limits are, the best way to use it. 

 

I design insulated raft slabs for example, done it for years. But I can see there is potential for tweaking the perimeter insulation to extend down towards the foundation. This can make a big difference if the site conditions are ameniable.

 

The actual type of soil under an insulated slab and around the underbuilding can have a huge impact as does the mobility of any ground water. @saveasteading is probably the best exponent of this practical art on BH as he has actually built hundreds if not more.

 

At the end of the day the key to designing for self builders is to keep it as simple as possible, even if everything is not prefect. This allows for example a local builder with limited knwoledge, who does not have access to specialist trades to compete for and have a chance of delivering what you are paying for. 

 

@SteamyTeaYour absolutely right to highlight the form factor for example.. that is one bit I could see. I tried to track you formulae but the references are not familiar to me. But in the round my feeling is that you are introducing the next generation spreadsheet. call it Jeremy mark two? 

 

 

 

 

5 hours ago, Gus Potter said:

and how I'm going to communicate the information so everyone can understand it,

That is the hard bit.

5 hours ago, Gus Potter said:

I tried to track you formulae but the references are not familiar to me

That is because I was being a bit flash to work around the charting limits in LibreOffice.  I would recommend downloading the portable version as it does not install itself on a PC, just runs from a memory stick.

 

5 hours ago, Gus Potter said:

I design insulated raft slabs for example, done it for years. But I can see there is potential for tweaking the perimeter insulation to extend down towards the foundation. This can make a big difference if the site conditions are ameniable.

 

The actual type of soil under an insulated slab and around the underbuilding can have a huge impact as does the mobility of any ground water

I have some data about ground temperatures that I am looking at, so may be able to make some sense from it.

In the colder regions of America they sometimes extend insulation out from the foundations, or create a skirt of insulation deeper than the foundations.

 

I think this is for frost heave, but it should also make the temeperature under the slab more stable.

 

Could GSHP pipes be layed under the raft at the same time to take advantage of this, or would removing heat under the slab cause other issues?

3 minutes ago, sgt_woulds said:

Could GSHP pipes be layed under the raft at the same time to take advantage of this, or would removing heat under the slab cause other issues?

 

GSHP at this depth is actually solar thermal rather than geothermal so the ground used for extraction of heat requires annual restoration by the sun otherwise it does not recover for the next heating season and why the ground array sizing is so important.

13 minutes ago, sgt_woulds said:

Could GSHP pipes be layed under the raft at the same time to take advantage of this, or would removing heat under the slab cause other issues?

Area is small for use as a heat source,  it's expensive, in summer house over heat would charge ground, but only if you had no insulation. Big risk of freeze if you strip too much heat. So no.