Setting up / balancing my MVHR

[ProDave]

The BH loan anemometer arrived today.  I could not help having a quick go round to see how things are.

 

Background, the MVHR was set up "by the seat of my pants" when we moved in 18 months ago.  By that I mean I just sent the inlet / exhaust vent restrictors wide open for those with long pipe runs, and closed them down somewhat for vents closer to the MVHR.  It's a radial system.

 

I downloaded the spreadsheet on the anemometer  loan thread and just input my values to that.  My spreadsheet is attached

 

No 1 observation. This is set up for English building regs.  I am in Scotland.  I obviously need to go and look up if there are any differences in required ventilation rates here.  Has anyone on the forum done a version of this spreadsheet modified for Scottish regs?

 

Observation 2:  Kitchen is failing boost extraction rate but other rooms are way over. Some adjusting of the vents should easily sort that out.

 

Observation 3: Whole house trickle rate is way too low.  Like many others on here I want it to run at the slowest rate possible.  I will probably have to increase the trickle fan speed a notch to get this to comply and (cough) reduce it if I am happy to "under ventilate"

 

Observation 4:  My total inlet and total extract rates do not match. Again I am sure adjusting the restrictors will sort that out.

 

And a general observation.  That spreadsheet is WAY WAY more simple than I expected.  I thought I would have to be calculating each room volume and working out a target ventilation rate for each room based on it's volume.

 

The bottom line is what is the building inspector going to expect to demonstrate compliance? is it really as simple as present this spreadsheet with all "pass"?

 

 

Willow_burn_Ventilation.xls

[joe90]

4 minutes ago, ProDave said:

That spreadsheet is WAY WAY more simple than I expected. 

 

Glad to hear that as I am yet to do mine

5 minutes ago, ProDave said:

The bottom line is what is the building inspector going to expect to demonstrate compliance?

 

our BI. Just said “oh you’ve got MVHR so you don’t need room extractors” (I did have a copy of @Jeremy Harris figures to hand with our address on it ?).

[Savage87]

@ProDave How did you get hold of BH anemometer?

 

The spreadsheet that you have attached, does it have actual measured values in it?

 

I had a word with my local Building Control and they said they are not interested in any air flow values, they said, just go ahead and install it..

[PeterW]

2 minutes ago, Savage87 said:

How did you get hold of BH anemometer?

They are in the tool loan section of the forum 

 

https://forum.buildhub.org.uk/topic/3281-on-loan-anemometers-for-testing-and-setting-up-mvhr/

[ProDave]

Make your intention to borrow it on this thread and you will be put on the list

 

 

[Bitpipe]

26 minutes ago, ProDave said:

 

The bottom line is what is the building inspector going to expect to demonstrate compliance? is it really as simple as present this spreadsheet with all "pass"?

 

 

Per my experience, a DIY cert to say all is well

[Gone West]

14 hours ago, ProDave said:

The bottom line is what is the building inspector going to expect to demonstrate compliance?

In my case absolutely nothing.

[ProDave]

1 minute ago, PeterStarck said:

In my case absolutely nothing.

So this exercise is more about me knowing is is correct then.

[Gone West]

3 minutes ago, ProDave said:

So this exercise is more about me knowing is is correct then.

In my case yes. Having dutifully set it up for SAP and produced all the paperwork he wasn't interested. So after it was signed off I reset it all for PH levels.

[ProDave]

55 minutes ago, PeterStarck said:

In my case yes. Having dutifully set it up for SAP and produced all the paperwork he wasn't interested. So after it was signed off I reset it all for PH levels.

Briefly, what are the PH ventilation levels needed for normal trickle and boost?  Like many that is what I will aim for after completion.

 

Back to the immediate building regs compliance.

I have scoured the 2013 Scottish Building regs technical standards manual and it is far from clear.  The only reference to boost extract levels are the normal extract requirements of 60L/sec * for a kitchen, 30L/sec for a utility and 15L/sec for a bathroom.  But these are the normal levels for a simple extract fan and trickle ventilation.  No mention of MVHR

 

* the 60L/s is the requirement if the extract is not through the cooker hood.  If it is via a cooker hood it is only 30L/s

 

All it says about MVHR is refer to BRE Digest 398 which thankfully a simple search finds was available as a free PDF download.  All that says is the trickle ventilation rate should aim for 0.5 Air changes per hour. No mention of boost requirements.

 

So going back to our spreadsheet, if I try and aim for those boost extract rates then my jitchen fails now by a long way.  I can increase the boost fan speed further if I need to.

 

Calculating my house volume at 433m³ so 0.5 ACH comes out at 216.5m³ per hour which is 60L per second for the whole house.  I am well short of that.

 

I will try later with increased fan speeds and some adjustment of the ducts, but at the moment I feel somewhat in the dark, not really understanding what Scottish building regs actually want, particularly with regard to boost extract rates. This is where I am hoping someone else in  Scotland who has done this might help?

 

 

[Ed Davies]

1 hour ago, ProDave said:

Briefly, what are the PH ventilation levels needed for normal trickle and boost?

 

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11461&page=2#Comment_193433

 

There's some quibbling further down the thread on how the volume is calculated when the ceiling is higher.

 

[ProDave]

Thanks @Ed Davies  That will help later on for setting it up for PH levels.

 

Still no help on BR values.  I tried speaking to the local duty building control officer but he only agreed "yes it is not clear" and has gone away to find out and I am waiting for him to phone back.

[ProDave]

Building control phoned back. Only to say he needs to speak to someone else who won't be available until Monday. So that's my plan to get this wrapped up this weekend gone then.

 

I have had a look at the more recent 2017 Scottish building regs.  For MVHR they still refere to BRE Digest 398.  They do separately mention DMEV (distributed mechanical ventilation) and quote the following

 

Kitchern 6L/s continuous, 13L/s boost

Utility 4L/s continuous, 8L/s boost

Bathroom 3L/s continuous, 6L/s boost.

 

I don't think those apply to mvhr though.

 

There is also reference to CIBSE Guide 2:2001 section 3. I'm off to see if I can find that.

 

I suspect the reason most are not asked for any paperwork, is the fact nobody know what it should comply with.

[Gone West]

2 hours ago, ProDave said:

Briefly, what are the PH ventilation levels needed for normal trickle and boost?  Like many that is what I will aim for after completion.

This is how I set mine up for PH levels.

MVHR Calculation.pdf

[Ed Davies]

I wonder how they'd react if you just set up for PH levels and say so.

 

I've just been bumped up to 2017 regs on my most recent warrant renewal so this thread was a handy reminder to read the 2017 ventilation rules, which don't seem like much of an improvement in clarity over the 2013 lot.

 

The other changes which affect me are the need for a CO₂ monitor (which I have anyway) and the need for robust walls for fitting handrails in the shower room which other discussions on this forum had prompted me to think about, too. So not a hassle really.

[ProDave]

9 minutes ago, PeterStarck said:

This is how I set mine up for PH levels.

MVHR Calculation.pdf 541.2 kB · 2 downloads

Thanks Peter.  Does PHPP only concern itself with the trickle rate and is not bothered by any boost rates?

[ProDave]

4 minutes ago, Ed Davies said:

I wonder how they'd react if you just set up for PH levels and say so.

 

I've just been bumped up to 2017 regs on my most recent warrant renewal so this thread was a handy reminder to read the 2017 ventilation rules, which don't seem like much of an improvement in clarity over the 2013 lot.

 

The other changes which affect me are the need for a CO₂ monitor (which I have anyway) and the need for robust walls for fitting handrails in the shower room which other discussions on this forum had prompted me to think about, too. So not a hassle really.

Why did you get bumped up?  My understanding is as long as you keep renewing you stay on the version of regs when the building warrant was issued.  Next May I will be doing my third, and hopefully last extension.

[ProDave]

I have also just found this old thread on buildhub 

In that thread there is a link from @HerbJ to a spreadsheet for his MVHR comissioning. But no reference to how the target levels were determined (e.g each bedroom has a different design rrate)

 

What is still missing is how, under Scottish building regs do you determine the target flow rates.

 

Ever felt you are banging your head against a brick wall?

 

 

[Ed Davies]

4 minutes ago, ProDave said:

Why did you get bumped up?  My understanding is as long as you keep renewing you stay on the version of regs when the building warrant was issued.

 

I think they can if it's been more than 5 years. Given that it's obvious I won't be finishing soon they took the option. You don't have to retrospectively change anything which has already been installed or would be impractical to change in the design so it's not that onerous.

 

In theory they could have asked me for a new SAP calculation but I'm so far clear of that that they waived it.

[Ed Davies]

12 minutes ago, ProDave said:

I have also just found this old thread on buildhub

 

But everybody on that thread is in England (edit: plus one in Wales).

Edited November 15, 2019 by Ed Davies

[Gone West]

1 hour ago, ProDave said:

Thanks Peter.  Does PHPP only concern itself with the trickle rate and is not bothered by any boost rates?

On my system there are four ventilation levels.

#1 for when the house is unoccupied

#2 normal ventilation

#3 increased ventilation

#4 boost

So I set it up for level 2. The supply and extract motors can be set up independently for all levels. Level 4 is 100%. I set level 3 to be halfway between 2 and 4 and level 1 to be halfway between zero and level 2. I put an entry in my blog about commissioning the MVHR system.

 

[dpmiller]

Odd that the Scottish regs are still so woolly whilst in NI they were very specific about MVHR even in 2012- which is the latest regs...

 

just in case it's ony use:

http://www.buildingcontrol-ni.com/assets/pdf/TechnicalBookletK2012.pdf

[HerbJ]

2 hours ago, ProDave said:

In that thread there is a link from @HerbJ to a spreadsheet for his MVHR comissioning. But no reference to how the target levels were determined (e.g each bedroom has a different design rate)

 

I can assist by providing the Volumetric Design Calculations that were produced for my MVHR systems. These were produced using two different approaches for the design target levels for each room - the DIN standards and also the BR Part F Requirements. The reason the bedrooms have different flow rates is basically because they are different volumes... Note, my house is located in England

 

@Bitpipeand I went through the same brain twisting being experienced by    @ProDave and I produced this note to rationalise my thoughts at the time.  I hope it helps you ( note, the figures quoted were early in our design process and sizes changed during development of the build and the Helios Tool is an online app for calculating design volumes according to the DIN standards) ....

 

I have been contemplating our MVHR designs and it is very clear that both designs are completely dominated by the BR Part F requirements for whole house ventilation. Table 5.1 (b). - for Eastcroft  = 364m3/hr and for your house 372 m3/hr ( depending on your measured GIFA). Anyway it seems to me, and to others, that though we will have demonstrate that our systems can meet this requirement for BR , we would never operate the system at this level and the system would be set up for something completely different. Unfortunately, it is this system sizing that most of the less experienced retailers focus on when they sell their systems and thisn drives a requirement for these systems to be sized and operated at this level. I am fairly sure that where Zehnder are coming from by insisting that Eastcroft requires two Comfotair CA550 units, so that they run quietly at a much lower operating point they will never see again after the BC have approved the installation.

I have also come to realise that though the DIN designs managed to produce from the Helios Tool are correct,  for what I entered but  I have probably entered some rooms that may not require individual extract/supply air and this has potentially oversized the system, though DIN does seem to be able to take into account the practicalities of operating systems at various levels - Moisture Protection, Reduced, Nominal and Intense ventilation

So, realisng my lack of MVHR experience,  I have trying to found some practical and sensible technical approach to sizing MVHR systems and even tried to get a copy of  the DIN standard (no joy, it costs 140 euros).  Finally, I came across a recent  Passivhaus document that was actually highlighted on ebuild only within the last week. I attach a pdf version of the Chapter 5 which provide practical and passivhaus  approach to sizing MVHR systems

see http://www.ebuild.co.uk/topic/16037-how-to-build-a-passivhaus/page__pid__121081#entry121081

So, I have quickly used this simplified and practical approach to re- look at both Eastcroft and your house.

For your house, if we just take the quoted extract rates for your kitchen, Ensuite bath, two family bathrooms, utility room and cloakroom this gives a Extract Requirement of 240m3/hr.  Then for supply, I reckon you have  nine habitable spaces at 30m3/hr = 270m3/hr. In any case, your house will only have 4 occupants and this should also be taken into account. So, taking the Standard (or nominal setting as per DIN) as 0.3 ACH  = 0.3*853m3 ( the volume of your house from Helios) = 255.9m3/hr and the Boost Rate = 1.3* 255.9 = 332.6 mm3/hr.  So these "passivhaus" recommendations are not too dissimilar to the Helios Fan supported airflow volumes, according to DIN,  on page 4.

In Part F the boost rates for extract volumes are for  kitchen =48.83m3/hr, cloakroom/toilet = 21.6m3/hr and  bathrooms = 28.8m3/hr. so the passivhaus recommendations are all higher except for the cloakroom /toilet which was 20mmm3/hr  This starts to provide a little more confidence about sizing of our MVHR systems, rather than to start and finish at Part F Requirements .





 

 

38167 HRV Volumetric Design 2015-4.pdf How_to_build_a_Passivhaus_Chapters_5_to_9(3).pdf

Edited November 15, 2019 by HerbJ

[ProDave]

Yes sorry @HerbJ , because your design was done by PaulScotland I put 2 and 2 together and made 5 and assumed it was to Scottish regs.

 

If I get time I will try and balance my system and set it up to comply with the English regs, and then see how far out that is when I eventually find out what Scottish regs demand.

[Mally]

4 hours ago, HerbJ said:

DIN standards

@HerbJ Does your reference to DIN Standards refer to  "Deutsches Institut für Normung" - "German institute for standardisation"?