Any one done their own Part O modelling?

[Susie]

We have our planning permission but fall under the new regs so for Part O Overheating we have to pass either the simplified model or the dynamic model.

I have created my own spreadsheet and by changing nearly all my windows to opening and to opening inwards to get round the arms reach criteria and a few minor size changes to increase ventilation we have just scraped through as a pass. 
My architect has given me my sketchup file and this weekend I plan to start looking at the Thermal Dynamic modelling TM59 with Part O adjustments using TAS software. 
The simplified model does not take into account the MVHR or the overhang shading so I am hoping by spending a bit of time and money on the software I can keep some of my fixed windows. 
As this is a new reg if any one wants to look at my spreadsheet I have attached it below. I’m a Mac user so if you run into any problems on Microsoft excel let me know and I can amend it. 
Thanks @craigfor your help so far. 
It’s been a steep learning curve to get this far so if I can help any one else on their journey that would be nice. 
So I’m off to start another steep learning curve using the software, just preparing with a big breakfast and lots of coffee. Any tips on the software welcome. 

https://kb.goodhomes.org.uk/wp-content/uploads/2022/07/220720_FHH-Part-O-guidance-Final-LT.pdf#page44
 

https://www.edsl.net/tas-engineering-downloads/

 

Part O Calculations Simplified method.xlsx

[LSB]

OMG - well done, but I'm now worried, haven't even thought about any of this sort of thing yet.

 

[Susie]

Hi @LSB I thought you had already started building. 
if you got building regs in on the old regs then you don’t have to do this. 
 

[LSB]

1 minute ago, Susie said:

Hi @LSB I thought you had already started building. 
if you got building regs in on the old regs then you don’t have to do this. 
 

We had started preparing the site and the underpinning, but the building regs weren't actually signed off so I need to talk to the BCO to find out what he thinks.

We are using a private BCO so not sure if that will make any difference, I gave him some money a while ago, but not before June last year.

He's been out for trenches and foundations and the underpinning, but which regs we need hasn't actually been mentioned.

 

 

[Alan Ambrose]

Well I just read through part O - my first reaction was hilarity .

 

The expectation is that you do this after you've adjusted your windows following your heat loss calcs and before your planning application?

 

"Despite its name, the Simplified Method is not entirely simple".

 

Yeah, well.

[Susie]

Sounds like it was ok to start the build so @LSB probably on the old regs.  
we haven’t submitted the building regs plans yet so are definitely on the new regs  the part o model has to be submitted with the plans. 
yes @Alan Ambrose
Simple is not simple but the dynamic is even harder. 
 

[Alan Ambrose]

Well I think 'O' is badly thought out. 'No benefit from trees or curtains' is dumb'. Our present place was v. hot at times before we planted the garden up and put in some thick curtains. (We didn't design it and its a barn conversion, so lots of the design decisions were made in the 1850s.) It's fine now and the plants we've used love the sunshine.

 

I think my strategy will be to apply for planning with ample glazing and then reduce glazing / add solar mitigation with non-material amendments as necessary. There's no point in doing all the calcs if planning hates the design for other reasons. And planning won't be that bothered if we want to reduce the glazing later. 

[Alan Ambrose]

Well I've been researching this some more and  thought I would post an update:

 

+ The headline is that this looks a significant can of worms for a lot of self-builders unless you have very mass market design sensibilities. Barratt home anyone?

+ This video by Pilkington says (about 1/2 way through) (roughly) 'yeah, if you want Grand Designs, then the Simple Method won't work for you'. https://www.youtube.com/watch?v=NrY7odmPm68

+ I did a rough-and-ready 'Simple' analysis of our current design. If my calcs are correct, then we're way over the limits atm.

+ There's a lot of the 'Simple' procedure which doesn't make a lot of sense to me e.g. why would you want to limit North facing glazing?

+ @Susie - as you have pointed out, there's no allowance in the 'Simple' method for any mitigation like the various forms of shading etc. So the proven Mediterranean methods: outside shutters / awnings / vegetation etc etc etc are totally ignored as are modern methods e.g. Pilkington's low-transmittance SunCool glass.

+ That suggests TM59 modelling may often be necessary, which might be properly expensive if you get someone else to do it.

+ There's a comparison of a couple of modelling packages here: https://journals.sagepub.com/doi/pdf/10.1177/0143624418792340

+ And I note that one of the two pieces of software mentioned there: EnergyPlus, is free https://energyplus.net/

 

All-in-all quite a complex headache IMO. Designed to protect city flat dwellers who largely have to live with what they've got (and cope with the window opening implications re noise / pollution / security / safety), I question the relevance for self builders who usually have control of their own building and can therefore retrofit (e.g. shutters / awnings etc) later if they find they have a problem. Also, bulk house builders will only have to model a 'sample of homes' (and Part O doesn't give hard criteria for the sample) and therefore they can spread the costs over an entire development, whereas the self-builder will usually need to do a one-off i.e. 100% analysis. Hmm, another little industry and new build tax has been created.

[Susie]

I have a pass on my spreadsheet. 
This is a link for anyone else to the best info and spreadsheet I found. 
I will post mine later. 
https://www.futurehomes.org.uk/avoid-overheating

 

[Susie]

I hope in the future this will come in handy for somebody else. 

The simplified Part O Overheating spreadsheet is as completed by myself and handed in to BCO

If any one needs any help feel free to ask away.

I will update this post with any feedback I receive from BCO.

Part O Simplified Method_FHH-SM-BETA-1.xlsx

[Alan Ambrose]

@Susie - thanks is it possible to add an image of the elevations so we can get an idea of what that % of glazing looks like in practice?

 

TIA, Alan 

[Susie]

1 hour ago, Alan Ambrose said:

@Susie - thanks is it possible to add an image of the elevations so we can get an idea of what that % of glazing looks like in practice?

 

TIA, Alan 

The architect is adding some roof windows, as soon as the drawings are updated I can upload an image. 

[Alan Ambrose]

Ah, thanks I see you have an image in this thread: https://forum.buildhub.org.uk/topic/31617-ideas-wanted-to-pass-part-o-simplified-modelling-or-to-use-dynamic-modelling/#comment-467880

 

FYI another couple of things I couldn't get a clear steer from the 'regs' (in the Part O Guidance) are:

 

+ there doesn't seem to be any sense of angle to the sun in the Simple Method - so roof lights are a bit problematical. Which compass direction are they facing - well often mostly 'up' of course.

+ in a similar vein, if you have roof lights over a 1+ storey void, then do they 'belong' to the ground floor or to the one above?

+ re security - if you live in the countryside, is it considered 'secure' (only for the purposes of these calcs) to sleep with ground floor windows open? Doors? (As far as we're concerned we normally sleep in summer most of the year with ground floor bedroom windows open.)

 

And general observations:

 

+ Part O is all about the problems of solar gain, nowhere does it mention or consider the benefits (economic / climate / amenity) of solar gain.

+ The actual TM59 software mentioned in the Guidance examples is:

 

IES VE 2021 3.1.0 (this is 'send for quote')

TAS software v9.5.2 (£200 p.m.)

 

- it's curious that CIBSE has specified in TM59 some simulation and CFD calcs without specifying (a) exactly what those calcs are, (b) a list of software which is deemed to observe the calcs, (c) a verification method for that software.

 

I see also that DesignBulder software claims to be TM59 compliant and uses the free US-based EnergyPlus for simulation and HVAC. There's some TM59 notes for using it here:

 

https://designbuilder.co.uk/helpv7.0/Content/CIBSETM59.htm

 

 

 

[Susie]

I have a 2 week trial of TAS but probably need a rest. I was going to use it but my architect used sketchup and it won’t import so I will have to draw it up my self not too hard but I’m behind with my work so since I have at least a temporary reprieve in passing the simplified method I’m catching up on work. I might go back to it later. Even if I end up giving the software a go later it should be done in a month so not an expensive option and will take my MVHR into consideration.  Then cancel the software contract. 

For security we are supposed to have bars or grills if a bedroom is on a ground floor. It’s a wait and see what happens game.  I’m also in the country with windows open at night.  They will vent from the top, tilt and turn type. 

My windows have had to change two made 200mm more height and 6 roof windows added for ventilation.  Two small windows removed that are replaced with roof windows. 
All additional windows on the North and making that the most glazed facade giving better target %. 
My problem might be different to some as it wasn’t too much glazing but not enough ventilation as some windows were big picture windows. I don’t want them to open as too big, bigger frames needed and another window seal in a very exposed location. 
I feel like most of February has gone by and I have been pondering windows most of the time so need a rest.

The future homes spreadsheet only came out November I think 6 months after the regs changed I guess they know it’s a mess. 
I will post my before and after drawings as soon as I get them but happy to help anyone if I can. 
 

 

 

[Alan Ambrose]

Thanks, some interesting insight. Clever to make the North facade the most glazed. I was surprised that you had to increase the size of the windows, my feeling (I have not done the ventilation calcs yet) was that I would be struggling to keep the glazing I want.

 

The paper I listed above showed a comparison between IES VE and EnergyPlus and the conclusions included "Significant differences were recorded between predictions, with the EnergyPlus models recording a high overheating
risk in seven out of the nine cases, while IES VE predicted a low overheating risk for all models." That suggests to me some TM59 game playing by choosing the package that comes up with the most helpful results? I can't help feeling that Part O is very badly thought out. I'm reading a bunch of stuff on PHPP & TM59 right now.

[cheekmonkey]

I've just failed due to general overglazing % & also most glazed room, something to do with it being open plan & they then sub divide for calcs.... it literally is a BONKERS regulation for the most part. In theory in breach of planning if we remove windows. we don't want to remove windows!

has anyone had any luck trying to use any software to do TM59 model yourself?  I've been estimated something like £1700 to have it done!!! I've got no problem with applying mitigation measures within reason if that's the only way to do it?

[Dave Jones]

On 23/02/2023 at 15:51, Susie said:

I hope in the future this will come in handy for somebody else. 

The simplified Part O Overheating spreadsheet is as completed by myself and handed in to BCO

If any one needs any help feel free to ask away.

I will update this post with any feedback I receive from BCO.

Part O Simplified Method_FHH-SM-BETA-1.xlsx 782.52 kB · 4 downloads

 

wow great work!

 

Any tips to get started on it for a non techie ?

 

Also how does this stack up with mvhr where you  dont want open windows ?

 

thanks

Edited March 9, 2023 by Dave Jones

[Susie]

57 minutes ago, Dave Jones said:

 

wow great work!

 

Any tips to get started on it for a non techie ?

 

Also how does this stack up with mvhr where you  dont want open windows ?

 

thanks

The simplified version does not take into account MVHR at all.  If you don't want to make most of your windows open you will struggle.

It depends on how use to a spreadsheet you are and how big your build is.  Mine was a simple rectangle, not too difficult as im use to spreadsheets.  Does the cost of @cheekmonkey put you off a dynamic model?  I guess it depends on if the cost guarntees we keep remodelling until its a pass or if its £1700 and it either passes or fails and then more £ per hour until it passes.

For me the cost of the dynamic was offset by me doing the simplified model and minor changes to some window sizes and although some windows now open and I would have preferred them to not open the cost of this change is still less than the Dynamic model would have been  and as a bonus I have an opening window.  I changed some windows to velux windows giving me more air flow on the North facade and I will probably have more art work on the wall or whatever looking to the positives.

 

The following is for a non techie it breaks it down into sections if you are ok at allowing for frame sizes start with who you are most likely to choose as window supplier and use their data, enter all rooms one at a time.  I made another table that allows for frame measurements jamb header non opening, jamb header opening, cill non opening etc and then a window opening that table that would reference the frame and input the data into the simplified spreadsheet.  I can not show my calculations as Im a Mac numbers user not Microsoft excel and too much is lost in the conversion.

A basic start for a non techie would be to start with what you think is your most glazed facade and don't worry about frame sizes just treat all windows as the full opening measurement and opening fully inwards top hung, unless it definitely can not be opening. You will need your Gross Internal Area and m² for each room on that facade.  

If that passes or is very close to passing move onto bedrooms one at a time.  On each one if you pass with all opening then try non opening and see if that's a fail or pass.

Then move onto the other facades.

If your passing or close then you have to start thinking about frame sizes and how each window will ideally open or not start with the windows that you don't want to compromise on then adjust the others either bigger for more ventilation or smaller if you have too much glazing.  Each time you change something check which is your most glazed facade because if you start of with the most glazed on the West and harder % targets to meet adding windows to the North or East may change things and give you easier % targets to meet.

I would be happy to look at your spreadsheet once started sometimes its just a case of another pair of eyes spotting a simple change.

 

Before Part O Calculations

After Part O Calulations

 

 

[cheekmonkey]

thanks @Susie i'm waiting on a call next week to dig into it all a bit more. it seems basically we remove glazing using simple model (we're 4.2% over target on overall glazing) & we'd have to argue the open plan room bit as if they break it down as i've been told they do we'd never ever pass (it means we're like 50% over), or we have to suck up the modelling costs & as you say understand how likely we can achieve a pass with some mitigation like shading etc.  I expect just taking into account the MVHR system might mean we pass but i dont know how it's calculated yet.

another very silly BR rule. if it's hot we open the 10 meters of sliding door & the velux in the roof to cool it down!! madness

[Alan Ambrose]

@cheekmonkey - is your 'failure' pre or post-planning sign-off?

 

And, I agree that Part O simple method is nonsense as e.g. it doesn't 'allow' mitigation. Clearly, mitigation options in a London flat are generally limited (that 'use case' seems to be the whole driver for Part O), but for suburban or rural houses it's no problem at all. Even after-the-fact once the thing is built.

 

There now seems to be 4 or more ways of calculating solar gain (Part O simple / TM39 / PHPP / Part L Criterion 3 etc) and I wonder whether anyone has done a comparison?

[Canski]

I can't get my head round all of this at the moment so will be outsourcing it. I have had my basic SAP calcs done but have had a quote for Simplified method £ 200 and Dynamic thermal modelling at £900. Plus VAT Hope this helps.

Edited March 13, 2023 by Canski

[Alan Ambrose]

The cost sounds not unreasonable to me. Simplified Method is simple-ish (say, an hour or so) once you have the window / door / room sizes. Do your quotes allow for iterations - it's likely that if you're over the limits, that you'll want to do a bunch of what-if calcs? So, if that's cost per iteration not so useful, if it's cost to get to a workable detail design, that's much better.

 

Does 'dynamic thermal modelling' handle solar gain and shading? Who's the supplier, a bunch of us would be interested I'm sure?

 

I think the various simulation packages (as opposed to 'Simple Method') may come up with quite different results, so it's possible some people will want to do 'simulation shopping' to get the most favourable results.

 

 

Edited March 13, 2023 by Alan Ambrose

[Furnace]

The iteration of even the Simplified model could end up being expensive. Similar to @Susie, my design failed at the first attempt. It then becomes a process of tinkering with sizes and openings to get a pass. It can be a challenge since reducing glazed area to meet the 'Total Glazing area for home' limit of 15% of Gross Internal Area also affects the 'Removal of excess heat' requirement to have opening apertures. Chasing your tail.
Like Susie, I found that I needed to make more windows openers, and some internally opening to overcome the restriction that outward openers are limited by 'the handle must be within 650mm of the internal face of the wall' rule. That rule impacts the effective aperture, whereas an inward opener benefits from the whole aperture.
I'm having brise soleils and MVHR on my passive house build, but the Simplified model allows no benefit for either. Fortunately, I didn't need to compromise on much to get a pass, but it may still cost money as openers are more expensive than fixed panes. I'm waiting to find out of the LPA will accept PHPP for Part O.

[Alan Ambrose]

>>> The iteration of even the Simplified model could end up being expensive.

 

Do that one your self and you can play as much as you like. A one-page spreadsheet.

 

>>> I'm waiting to find out of the LPA will accept PHPP for Part O.

 

That would be a major win.

 

 

[Furnace]

7 minutes ago, Alan Ambrose said:

Do that one your self and you can play as much as you like. A one-page spreadsheet.

Yup, as long as you're comfortable doing it (like Susie and I were). But for those like @Canskiwho wish to outsource, it's worth nailing down what the quote covers since it's quite possible that multiple iterations are required.

 

10 minutes ago, Alan Ambrose said:

>>> I'm waiting to find out of the LPA will accept PHPP for Part O.

 

That would be a major win.

I'll let you know....