PHPP for part O

[G and J]

We’ve just submitted our design for building regs approval.   Our BCO has agreed that we can use PHPP to demonstrate that our design won’t overheat and thus is ok with part O.

 

I think PHPP 10 is the latest and will cost me somewhere between £200 and £250.

 

Is this what I need to purchase?    Or do I need other bits too?

[Dan F]

You ideally want to get someone to do PHPP for you, unless you have a lot of time to spend learning how to use it, but I still wouldn't advise this really.

 

- If someone else is doing it for you, you don't need to buy PHPP (they will use their own license), but you will need pay consultant fees of course.
 

- If you are doing it yourself you also want to buy the detailed manual, will need to invest a lot of time and IMO you won't be able to as confident with the outcome vs having someone with experience and PHI certification do it for you.  This is because there are so many details to it, and things that seem minor that it's possible to not fully understand, can have big impacts. (e.g. things like not getting ventilation assumptions correct, or not correctly adding all the fine details of glass spec, glass spacers, window frame size, overhangs, height of trees in your garden etc etc.)
 

[Gone West]

In 2009 I ran our design through the PHPP and the BCO accepted the results instead of an, as designed SAP. It took me months to collect and check all the data until I was happy. IIRC the weather data was problematical. Even though my day job was mathematical modelling.

[Nickfromwales]

It’s very time and detail heavy, and as said if you input things incorrectly, accidentally, then it’s not worth the paper.

+1 to getting it done by someone who’s going to know the pitfalls and get you an accurate outcome.

My 2 cents, but where do you think issues will arise? Are you super insulated, airtight, and lots of glazing? 

[G and J]

2 hours ago, Nickfromwales said:

It’s very time and detail heavy, and as said if you input things incorrectly, accidentally, then it’s not worth the paper.

+1 to getting it done by someone who’s going to know the pitfalls and get you an accurate outcome.

My 2 cents, but where do you think issues will arise? Are you super insulated, airtight, and lots of glazing? 

I think the actual overheating issue is exclusively me, under the collar, when I contemplate the box ticking exercise that really is a sledgehammer nutcracker.  
 

We are aiming at nicely airtight as we will have MVHR, but our insulation levels are modest (for a number of reasons more or less building regs in fact).  Our design has limited amounts of glazing, but it does have a 4m wide patio door at the back.  We can’t use the simplified method, as we can’t claim blow through and the patio doors blow it for one room.  
 

So we are required to do the dynamic method to prove the bleedin obvious, but rules is rules.  
 

Here are the elevations.  In glazing terms it’s not exactly Crystal Palace is it?

[Susie]

I’m not sure why the simplified won’t work. Are you saying some windows are fixed non opening. A big patio door on the east can still be ok.

have you tried the simplified I got ours to work. 

[G and J]

10 hours ago, Susie said:

I’m not sure why the simplified won’t work. Are you saying some windows are fixed non opening. A big patio door on the east can still be ok.

have you tried the simplified I got ours to work. 

After reading your stuff about it we did try doing the future homes spreadsheet.   Now we are doing it very strictly and we could not get the results thing all ok.  We do have some fixed windows, and from memory one of the issues is that the patio doors aren’t in a huge room, so proportionally it appears on the spreadsheet to be too much.

 

However, I’m now scratching my stubble and thinking, ‘ok, maybe I’ll try this again’….

[Alan Ambrose]

Yeah suggest normal calc should work fine for you.

 

>>> Our BCO has agreed that we can use PHPP to demonstrate that our design won’t overheat and thus is ok with part O.

 

Assume that’s not LA BC? Possible to tell us who? BTW walked past your plot the other day, great location.

[G and J]

5 minutes ago, Alan Ambrose said:

Yeah suggest normal calc should work fine for you.

 

>>> Our BCO has agreed that we can use PHPP to demonstrate that our design won’t overheat and thus is ok with part O.

 

Assume that’s not LA BC? Possible to tell us who? BTW walked past your plot the other day, great location.

That’s very kind of you to say.  Behind that little row of houses is a quiet little area of back gardens which I’m hoping will prove a lovely place to be whilst still being in easy walking distance of more cafés than one can shake a loyalty card at.  
 

We've engaged a company called Vantage.   They were recommended by our architect and I have spoken to a couple of the inspectors and they seem good, practical guys to work with.  They’re currently looking at our plans so we’ll see what comes back.  

[Nickfromwales]

22 hours ago, G and J said:

We are aiming at nicely airtight as we will have MVHR, but our insulation levels are modest (for a number of reasons more or less building regs in fact).  Our design has limited amounts of glazing, but it does have a 4m wide patio door at the back.  We can’t use the simplified method, as we can’t claim blow through and the patio doors blow it for one room.

The house doesn’t look overly complex at all. I would simply oversize the MVHR system slightly to allow for effective purge ventilation, and see if that takes any other mitigatory requirements out of the picture in one swoop.

 

I recently chatted with Nicholas Vaisey (CVC Systems, Oxford) for this exact reason, and for options to navigate this. These guys do all of my self-build clients heating / heat pump / hot water and MVHR, design, supply (and install (when I am too busy)) and this methodology provided a simple, practical, cost-effective (and elegant) solution in one box. This was considered in a set of proposals I’ve just done for a mass home builder, where I was drafted in to provide pre-construction M&E / plumbing design specifications for 2 large sites; Part O raised its head and everyone on the project just became disorientated as they weren’t used to dealing with it, clearly, with technical staff seeming utterly clueless tbh and were obvs out of their depth there! Doesn’t bode well for anyone buying one of their sausage-factory ‘boxes’…..

 

If the house is having MVHR anyways then economy of scale says this would be the easiest and cheapest route, eg to slightly over spec at the design level at minimal cost-uplift, adding in an assumption that slab cooling via UFH / ASHP is already possible / being considered? Combatting audibility (at higher airflow rates in the summer) with some extra thought going into the design for the distribution ductwork needs to be factored in, but at that point I would defo rule out a series run setup and go for radial.

 

What is the target airtightness score that you are aiming for? I think AT is more important than insulation as you can have a foot of PIR, but with high infiltration rates, and still see a cold house each winter.

[Susie]

9 hours ago, G and J said:

After reading your stuff about it we did try doing the future homes spreadsheet.   Now we are doing it very strictly and we could not get the results thing all ok.  We do have some fixed windows, and from memory one of the issues is that the patio doors aren’t in a huge room, so proportionally it appears on the spreadsheet to be too much.

 

However, I’m now scratching my stubble and thinking, ‘ok, maybe I’ll try this again’….

It seems ages since I used the spreadsheet now but aren’t the facade directions calculated rather than rooms.  
it looks like you have large (bedroom) windows upstairs do they open? Do they open enough at nighttime? 
if you upload the spreadsheet we can possibly help, a pdf would be ok as that still gives the overall values and how close you are to the figures you need to be within. 

 

 

[MikeSharp01]

On 05/12/2024 at 11:13, Dan F said:

me to spend learning how to use it, but I still wouldn't advise this really.

I did a training course 2 days at BRE was good and more interesting to watch the teams from the developers getting to grips with it. That was back 2018. It is time heavy to use but as I have built I have been keeping it up to date and initial work is showing that it broadly alines with the facts even though we have, so far, not put any heat in it. 

[Dan F]

30 minutes ago, MikeSharp01 said:

I did a training course 2 days at BRE was good and more interesting to watch the teams from the developers getting to grips with it. That was back 2018. It is time heavy to use but as I have built I have been keeping it up to date and initial work is showing that it broadly alines with the facts even though we have, so far, not put any heat in it. 

 

We had a consultant do our initial version, but i actually spent a lot of time learning it (bought the printed manual) and I used this knowledge to update and improve a few things that weren't quite right too.  It's doable, but I know from experiencia how much time investment is required to even try to get it right.  Also, how much of an impact things like exact glass specifciation, ventliation and how tress are modelled have have massive impact and change results fundamentally. 

[MikeSharp01]

39 minutes ago, Dan F said:

tress are modelled have have massive impact and change results fundamentally. 

we got luck there - no trees anywhere near us!

[G and J]

12 hours ago, Nickfromwales said:

The house doesn’t look overly complex at all. I would simply oversize the MVHR system slightly to allow for effective purge ventilation, and see if that takes any other mitigatory requirements out of the picture in one swoop.

Good point. I’m looking at an MVHR unit that’s spec’d for about twice our size, though that was done in pursuit of quietness and longevity but clearly it would also help if we did overheat.  Because we’ve had a good few hot nights here in Suffolk over the last few years we are going for an ASHP that also cools, with a deployed Fancoil in the main bedroom and probably plumbing and wiring for fancoils in the other bedrooms too.  We’ll run one zone for UFH and Fancoil to start with and run just above dew point, with the option of ‘valving’ out the Fancoil if needed so we can run really cold without condensed floors.

 

So I’m feeling ok about overheating in reality.  Part O is however different.

 

12 hours ago, Nickfromwales said:

Combatting audibility (at higher airflow rates in the summer) with some extra thought going into the design for the distribution ductwork needs to be factored in, but at that point I would defo rule out a series run setup and go for radial.

Plan is to use 90mm semi rigid (I think it’s the zhender stuff) in a radial system and I’m doubling up vents in a couple of areas.  
 

12 hours ago, Nickfromwales said:

What is the target airtightness score that you are aiming for? I think AT is more important than insulation as you can have a foot of PIR, but with high infiltration rates, and still see a cold house each winter.

I’m hoping to hit less than 0.5 but in truth it’s the thing I’m least confidant of and in the next couple of months I need to learn more towards this.  We have a narrow plot and thus thin walls and my initial disappointment with that has given way to a feeling that airtight makes up for a lot of missing U.  We shall see but one lives in hope.

 

I appreciate the input @Nickfromwales  

[G and J]

15 hours ago, Susie said:

aren’t the facade directions calculated rather than rooms

The spreadsheet uses a clock face type designation for the direct each window is facing and then in a separate box you set which direction the clock face is orientated to.  In our case that bit is easy, our drawing are draw with due north damn near directly upwards.

 

15 hours ago, Susie said:

large (bedroom) windows upstairs do they open? Do they open enough at nighttime

The big one has an oriel and is fixed to avoid needing a balustrade and the small one does fully open.  
 

15 hours ago, Susie said:

if you upload the spreadsheet we can possibly help, a pdf would be ok as that still gives the overall values and how close you are to the figures you need to be within.

Will do, we’ve been messing with it to try and understand how it works and so I’m going to redo it from scratch first.  I’d be chuffed to bits with some help here, so thank you.

[Alan Ambrose]

>>> We can’t use the simplified method, as we can’t claim blow through and the patio doors blow it for one room.  

 

I must have missed than sentence before. I started using PHPP only for Part O, ‘cos standard method doesn’t allow adjustment for low G glass or external blinds. I was able to show that those elements alone would solve any overheating problem easily. So, calculations aside, maybe one or both of those factors would solve any practical overheating problem? Or brise soleil or eaves overhang of course.

[Nickfromwales]

17 hours ago, G and J said:

We have a narrow plot and thus thin walls

Not the end of the world tbf, but I’d install 15mm sound block plasterboard to all the internal faces of the outside walls to combat acoustic pollution/nuisance ‘noise’. PIR does very little to promote a ‘quiet’ house, even with 140/160/180mm of the stuff sound still travels quite unsympathetically (assuming SIPs type construction?).

[G and J]

18 minutes ago, Nickfromwales said:

Not the end of the world tbf, but I’d install 15mm sound block plasterboard to all the internal faces of the outside walls to combat acoustic pollution/nuisance ‘noise’. PIR does very little to promote a ‘quiet’ house, even with 140/160/180mm of the stuff sound still travels quite unsympathetically (assuming SIPs type construction?).

We are planning 140mm stud frame, filled with 140mm Nyrock 032, thence 60mm battens with 60mm Rockwool RW3 inboard of the frame.   Downstairs will have rendered block skin too, upstairs will have 15mm plasterboard  so we hope we will be ok on the noise front.  Fingers crossed, but it's a relatively quiet area. (Woodbridge, where all the wrinklies go to serve their final years, all encouraged by the Guardian's best places to live list it seems!)

[G and J]

So, here it is, my latest attempt (of several) to get this b$£**!!ing spreadsheet to reflect common sense.

 

I'd be chuffed if anyone can identify where I'm going wrong and thus can avoid a dynamic modelling thingy.

20241207 Simplified Part 0 - munged.xlsx

[Susie]

only had a very quick look but a few q’s

bed 1 does it have two windows your calling them north and south but both on clock face 3, so this impacts on the most glazed facade.  You have marked south as being clock face 6 but said the windows are on 3 being east. A quick look at the plan makes me think the clock face is correct just the label misleading to me anyway.  This room will be a problem can the window that opens open inwards and more degrees you need more air flow at night. 

The living/kitchen/dining area sounds like it’s open plan on 3 different clock faces so it should be calculated as if it’s three different rooms see guidance below 

 

can’t follow your window and pane numbering I did mine to match up with the clock face starting at window 1 until all the way round the building giving each one a number 1,2, 3 through to the last window before the first.  BCO probably won’t pay the spreadsheet much more than check it says pass but keeping it so they see 12 windows on building matching up to 12 windows on spreadsheet keeps it simple. Then if one window is split into two panes eg if window 1 has 4 panes that’s shown as window 1 pane 1, window 1 pane 2 etc same for a sliding door or bi fold only a sliding door is one fixed one open .I had a sliding door one side fixed and one side fully open 100%

 

Make any changes if necessary then upload again. 

[ADLIan]

Save yourself a lot of money and use 035 mineral wool within the timber frame. Probably gives the same u-value as 032 product at fraction of the cost (15% timber frame fraction ‘degrades’ thermal performance of this layer).

[G and J]

8 minutes ago, ADLIan said:

Save yourself a lot of money and use 035 mineral wool within the timber frame. Probably gives the same u-value as 032 product at fraction of the cost (15% timber frame fraction ‘degrades’ thermal performance of this layer).

(I know I should start a new thread but I can’t resist replying….)

 

That'll take our wall u value from 0.181 to 0.184 and I think I’m pushing my luck at 0.181 as it is…. but I will price it up.  

[ADLIan]

U-vals are only quoted to 2 decimal places so still 0.18! Even if to 3 places a difference of 0.003 W/m2K is unlikely to impact overall energy assessment

[G and J]

12 minutes ago, Susie said:

bed 1 does it have two windows your calling them north and south but both on clock face 3, so this impacts on the most glazed facade.  You have marked south as being clock face 6 but said the windows are on 3 being east.

Both bed 1 windows face east.  I called them north and south to differentiate them, i.e. the more northerly of the two and the more southerly.  I can see (now) that being confusing.  Sorry.  I do appreciate you taking a look at this you know. 

15 minutes ago, Susie said:

This room will be a problem can the window that opens open inwards and more degrees you need more air flow at night. 

Yep, bed 1 is a furnace (according to part O anyway).  I’ve played with the details of the opening window and that’s I think the greatest ventilation I can get with that window size.  If there are other settings that are better I’d be chuffed to bits.  The oriel window is fixed to avoid extra balcony glass/ironwork/whatever and to get the maximum glazed area to enjoy the view over the in bed morning coffee (it’s a wrinkly thing).  To convert this and a couple of others to opening would probably cost a lot more than paying a consultant to do me dynamic part Oh! and still not pass the simplified method.

 

22 minutes ago, Susie said:

The living/kitchen/dining area sounds like it’s open plan on 3 different clock faces so it should be calculated as if it’s three different rooms see guidance below

I did that on my first pass.  Makes things worse.  Maybe I should try it again in case I mislead myself (one of my key skills, it appears!). 
 

 

25 minutes ago, Susie said:

can’t follow your window and pane numbering

I could not fathom what these numbers were for.  So I took it to mean sequential window numbers in each room.  Might redo these.  
 

27 minutes ago, Susie said:

Make any changes if necessary then upload again. 

Thing is I have tried all sorts with this and I can’t get a pass on simplified method.  That’s even with me claiming cross ventilation which is a bit of a stretch.    That’s why I resigned myself to a choice of wholesale glazing design changes or a dynamic modelling method, and the glazing choice would not make me happy and will cost more.  I wonder if our BCO has looked at our design and said to himself, ‘that’s ok from an overheating point of view’ and that adds to the argument that a PHPP report will be enough evidence.