MVHR newbie.. help needed

[Jeremy Harris]

8 hours ago, Savage87 said:

@JSHarris I hope I understand what you said in your last post. Do the above figures match with what your were saying?

 

 

Not sure why there's the fine detail, TBH.  The number is just 27l/s for both whole house background rate (90m² * 0.3l/s) or 27l/s for the extract rate (13l/s + 8l/s + 6l/s).  Room volumes don't come into it, as the building regs required extract rates are fixed irrespective of the size of those rooms and the whole dwelling ventilation rate is just calculated from net internal floor area, not volume.

 

Volume isn't used, either in the way building regs determines the required ventilation rates or when determining airtightness, as the UK calculation method only uses areas.

 

The PHI (and other countries) use the air change rate to determine leakage during the airtightness test, and to set the MVHR ventilation rate, but that's not how the UK regs are structured (although it's useful I find, to talk about whole house ventilation rate and airtightness in term of volume air change rate for a given condition).

[Gone West]

26 minutes ago, JSHarris said:

The PHI (and other countries) use the air change rate to determine leakage during the airtightness test, and to set the MVHR ventilation rate, but that's not how the UK regs are structured (although it's useful I find, to talk about whole house ventilation rate and airtightness in term of volume air change rate for a given condition).

I initially set my MVHR rates to satisfy building regs. and SAP for the BCO, who incidentally wasn't interested. After the building was signed off I set the system to PH rates because I think it makes far more sense to base the set up on the volume and purpose of each room than overall rates.

[jack]

9 hours ago, JSHarris said:

The Paul unit seemed noisy ... this was noise coming from the case of the unit, not from the ducts or terminals.  

 

Same with the one we saw. I was really surprised, given that when we were looking at MVHR units, Paul was just about the most expensive option.

That said, this was around 6 years ago, and I think the unit we saw had been in place for several years before that. I have no idea how well it had been installed or maintained. I know others who've had Paul units installed who are very happy. @HerbJ is one, from memory.

 

Our Brink is extremely quiet when it's on its standard background setting.

[Jeremy Harris]

6 minutes ago, PeterStarck said:

I initially set my MVHR rates to satisfy building regs. and SAP for the BCO, who incidentally wasn't interested. After the building was signed off I set the system to PH rates because I think it makes far more sense to base the set up on the volume and purpose of each room than overall rates.

 

 

I've done exactly the same, as the house was being over-ventilated at the building regs rates (and our BCO wasn't interested, either!).  I turned the whole system down a bit for the background ventilation rate, and that seems to work very well.  Mind you, there are only two of us in a 130m² house, so that's one reason why the building regs rates were a bit too high in practice, and the main snag with using area to determine ventilation requirements, IMHO.

[Ed Davies]

10 hours ago, Savage87 said:

I would love to get this done now but the house isn't at it's best at the moment. The kitchin is back to brickwork. I also need to get a window replaced.

I will also look into the homemade blower idea.. Thanks!

 

Maybe now's the time to be starting to play with the home made blower. People obsess on the air change rate/leakage when the house is finished but that only measures the overall airtightness achieved at the inner surface. What you actually want is have the airtight layer further out in the construction so that air leakage doesn't bypass any insulation you've added, so you're not effectively living in a plasterboard tent. So if you put a parge coat on the kitchen brickwork to make it airtight it would be worth checking that for leaks before adding insulated plasterboard or whatever.

 

OTOH, some care is needed with vapour control as well. From a purely energy-efficiency point of view it'd be ideal to have a hermetic seal round the outside of the house with all the insulation inside that. Unfortunately, that'd result in a cold surface accessible to the inside air where there'd be condensation and mould.

[joth]

1 hour ago, PeterStarck said:

I initially set my MVHR rates to satisfy building regs. and SAP for the BCO, who incidentally wasn't interested. After the building was signed off I set the system to PH rates because I think it makes far more sense to base the set up on the volume and purpose of each room than overall rates.

 

Good news is UK gov (or the civil service that runs it) is aware of the increasing divergence of building regs ventilation requirements vs low energy best practices. See recommendation 10 (table 1) on pg 18 here. Timeline to address "2019" yeah....

 

29 minutes ago, Ed Davies said:

Maybe now's the time to be starting to play with the home made blower

Does someone have a guide to making this home made blower? Sounds a fun project.  I'm assuming it's really just for diagnosing leaks not making an accurate measurement?

 

Edited October 24, 2019 by joth

[Jeremy Harris]

12 minutes ago, joth said:

Does someone have a guide to making this home made blower? Sounds a fun project.  I'm assuming it's really just for diagnosing leaks not making an accurate measurement?

 

 

Photos of mine:

 

 

 

I used an old car cooling fan, with the motor replaced with a brushless DC one for better speed control.  The motor and speed controller are standard model aircraft parts from China (Hobbyking, I think).  The speed is adjusted using a model aircraft servo tester, fitted with a better knob.  The thing runs from the DC power supply in the photo.

 

It's massively too powerful for testing a passive house, but was fine for finding air leaks in our old, 1980's, house.  The bit of MDF was cut to be a tight fit into an open bedroom window.

[Ed Davies]

6 minutes ago, joth said:

I'm assuming it's really just for diagnosing leaks not making an accurate measurement?

 

Yes, that's right. It won't be calibrated so there's little you can say about the actual air change rate but it'll show up leaks and, depending on how you use it, may give you an idea of relative changes in leakage.

 

Here's a thread on the subject from the other place. Sadly, the pictures seem to have disappeared: http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7396

[SteamyTea]

A blower, a proper one, would be a useful bit of kit to lend out. How much does one cost second hand?

Could join the MVHR kit.

Edited October 24, 2019 by SteamyTea

[HerbJ]

On 24/10/2019 at 08:44, jack said:

I know others who've had Paul units installed who are very happy. @HerbJ is one, from memory.

 

 

Yes, I installed a Paul Novus 450 in 2016 and it has been operating successfully and quietly since  it was commissioned in October 2016. I routinely change the filters.

 

It is installed in a reasonably Plant Room , which is accessed from the garage and is adjacent to the downstairs cloakroom and pantry/utility room.  The MVHR unit is mounted on feet, directly to the floor (passive foundation) and not attached to the TF structure, so no vibration induced noise..  I ensured that good sound insulation was  installed on walls and ceiling. When in the Plant Room, the  MVHR unit is relative quiet in normal operation  but the noise increases on  boost, but not enough to be uncomfortable when working in the room ( cleaning golf clubs as I was on Monday). Outside the Plant Room, in the garage or house, it is completely silent, though  if you have really good sensitive hearing you might just hear a very low noise on boost, when you are in the cloakroom.  The MVHR unit has flexible silencers to connect to the steel ducting, which goes to the two plenums in the room above ( see plenum). I have also wrapped both the flexible silencers and the insulated extract duct (from the MVHR to the outside extract grill) with a layer of aluminium foil faced ductwrap insulation, which made a noticeable reduction to sound level on boost.

 

 

The Plant Room is located  immediately, below the Guest Bedroom and there has never been a  noise problem. In fact, the inlet and extract plenums are installed in a service cupboard in the guest Bedroom and they are completely silent. The plenums are connected by steel ducting and a large silencer before the inlet plenum and a flexible silencer on the outlet from the extract silencer.

 

All the inlet and extract vents in each room are reasonably silent  except for a slight increase in noise on the extract in the Family Bathroom when on Boost.

 

 

 

Edited October 25, 2019 by HerbJ

[Pocster]

Yet to turn on my Vent Axia SX advanced.

All installed apart from electrics and the condensation drain.

Mine is in a bedroom!! - as it was the only place available.

Be very interesting to judge it's noise in normal mode and boost..

[Savage87]

Sorry it's taking so long to reply, I have done some careful considerations and we will be going ahead with the MVHR unit. I'm still considering the Domus HRXE to other unit. The unit should work at 75% performance on boost and this will satisfy BRegs. Once BC has been round I will turn it down to 50% and that will be sufficient based on the calculations that I done. as suggested by @PeterStarck

 

I have calculated the air flow/velocity through the duct and hopefully the system will be near silent at the valves.

 

In regards to the blower door test, I will definitely get one done but I think now isn't the right time for it. I have watched a lot of videos on how to look for possible leaks and how to fix the them. There will be a lot of work involved, but I'm confident that I can do it

 

Just to clarify a question that I had previously. The presssure loss in Pa on the performance graphs of the units is about the pressure in the whole system. Each component in the system(ducts, bends, silencer, etc) depending on air velocity creates resitance. This all ads up and it gives you the total pressure loss, so the more air resistance in your system, the more pressure loss you have and the harder the fans have to work to supply the air flow required.

 

@joth when looking at how noisy units are you can't really make a good assesment based on the sound performance charts alone because they are all different. I think it's better when you take into account other peoples view and personal experience.

 

Ducting system that I'm leaning towards is Airflow Pro 75mm round semirigid. What do you guys think ?

 

@pocster What are your thoughts about your system/unit?

 

@Jeremy Harris I love what you done with the homemade blower. How did you calculate ACH and pressure difference?

 

 

[Jeremy Harris]

3 minutes ago, Savage87 said:

@Jeremy Harris I love what you done with the homemade blower. How did you calculate ACH and pressure difference?

 

 

The simple answer is that I didn't! 

 

I made that unit up when I was trying to improve the airtightness of our old house, so I used it to de-pressurise the house and then went around looking for air leaks (there were dozens, all over the place).  It worked pretty well, as the bigger air leaks could be found by just holding your hand around likely places and many of the medium sized leaks made a great deal of noise.  Some of the more serious medium sized leaks were around every ceiling to wall junction (it was a bungalow).  There were no obvious cracks, but the plasterboard ceiling leaked air where it met the wet plastered walls everywhere.  I spent ages going around with acrylic filler trying to seal all these joints up. 

[Savage87]

Did you eventualy get a proper test done?

[ProDave]

I did a "Blue Peter Method" DIY air test a while back 

 

 

[Pocster]

17 minutes ago, Savage87 said:

Sorry it's taking so long to reply, I have done some careful considerations and we will be going ahead with the MVHR unit. I'm still considering the Domus HRXE to other unit. The unit should work at 75% performance on boost and this will satisfy BRegs. Once BC has been round I will turn it down to 50% and that will be sufficient based on the calculations that I done. as suggested by @PeterStarck

 

I have calculated the air flow/velocity through the duct and hopefully the system will be near silent at the valves.

 

In regards to the blower door test, I will definitely get one done but I think now isn't the right time for it. I have watched a lot of videos on how to look for possible leaks and how to fix the them. There will be a lot of work involved, but I'm confident that I can do it

 

Just to clarify a question that I had previously. The presssure loss in Pa on the performance graphs of the units is about the pressure in the whole system. Each component in the system(ducts, bends, silencer, etc) depending on air velocity creates resitance. This all ads up and it gives you the total pressure loss, so the more air resistance in your system, the more pressure loss you have and the harder the fans have to work to supply the air flow required.

 

@joth when looking at how noisy units are you can't really make a good assesment based on the sound performance charts alone because they are all different. I think it's better when you take into account other peoples view and personal experience.

 

Ducting system that I'm leaning towards is Airflow Pro 75mm round semirigid. What do you guys think ?

 

@pocster What are your thoughts about your system/unit?

 

@Jeremy Harris I love what you done with the homemade blower. How did you calculate ACH and pressure difference?

 

 

Hey !

 

Yet to turn mine on ! . Tbh even if I did I have no windows or doors - so unlikely to be effective ?. It’s all coming though ; just slowly .............

[Savage87]

sounds good, keep us updated! ?

[Jeremy Harris]

11 minutes ago, Savage87 said:

Did you eventualy get a proper test done?

 

 

Not on the old house, no, as it was pretty clear that the air leakage performance, even after I'd spent days trying to improve it, was not great, and there didn't seem to be much point in paying for a test.  The new house had an air test, which gave a reasonable result, under the PassivHaus limit, which was our target.

[Savage87]

I need to fit roof terminals for extract and supply ducts.

My roof has 2 sides, one towards north and one towards south. This is a mid terrace house.

North side is to the front of the house, facing a busy main road, so it's cooler and more polluted.

South side is facing the back garden and gets hotter.

I live in the MK postcode.

I think winds tend to blow from the west. If this is true, do I have to put the supply pipe towards the west and extract towards the east?

I don't know what would be best?

 

Also, I was looking at the different types of semi rigid ducts on BPC's website. I would like to get the best one I can, but I don't want to spend anymore than I have if there is no real added benefit.

So, what did you guys have installed? standard, anti static or anti static and anti bacterial / basic, standard or premium?

[Oz07]

Everywhere I've read says inlet and exhaust on same elevation 

[Savage87]

On 07/11/2019 at 19:30, Savage87 said:

I need to fit roof terminals for extract and supply ducts.

My roof has 2 sides, one towards north and one towards south. This is a mid terrace house.

North side is to the front of the house, facing a busy main road, so it's cooler and more polluted.

South side is facing the back garden and gets hotter.

I live in the MK postcode.

I think winds tend to blow from the west. If this is true, do I have to put the supply pipe towards the west and extract towards the east?

I don't know what would be best?

 

Also, I was looking at the different types of semi rigid ducts on BPC's website. I would like to get the best one I can, but I don't want to spend anymore than I have if there is no real added benefit.

So, what did you guys have installed? standard, anti static or anti static and anti bacterial / basic, standard or premium?

 

@Oz07thanks!

bump, does anyone else have more to add?

Edited November 9, 2019 by Savage87

[PeterW]

Do not split the extract and intake onto separate elevations. You will struggle to balance them - MVHR does not have a very powerful fan so may struggle to overcome the difference in a strong breeze. 

[Savage87]

1 minute ago, PeterW said:

Do not split the extract and intake onto separate elevations. You will struggle to balance them - MVHR does not have a very powerful fan so may struggle to overcome the difference in a strong breeze. 

 

as @Oz07 said, thanks @PeterW

I'm clear on the elevation. I'm not clear on south/north positioning and intake/outlet position based on my geographical location.

[PeterW]

South would be preferable as you will be forever cleaning filters otherwise. 

[joe90]

2 hours ago, PeterW said:

South would be preferable as you will be forever cleaning filters otherwise. 

 

Why?, mine is in the North side and filters are quite clean after a year!.