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Author Topic: MVHR retrofit  (Read 7974 times)
marshman
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« Reply #45 on: March 15, 2017, 08:02:21 AM »

IMHO. I don't see the point in an attenuator on the extract/exhaust side unless you're annoying neighbours.

Nearly correct!  No neighbours to annoy but I could hear the high pitched whistlie of the fan when outside when the fan was on high speed and it annoyed me Smiley It has no effect on the noise in the house.

Roger

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3.15kWpk (15xSharp ND210)/SB3000. & 3.675kWpk (15 x Suntech 245WD)/SB4000TL, 10kW GSHP driving Wirsbo underfloor heating from 1200m ground loops. 10' x 7' solar wall (experimental). Clearview 650 Wood Burning Stove. MHRV - diy retrofit. Triple glazing.
TheFairway
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« Reply #46 on: March 15, 2017, 09:58:04 AM »

Thanks all for valuable feedback.

@Roger
I think my unit is performing similar to yours in current temperatures. It may well be a different matter when temperatures go sub zero for lobg periods of time when I think I may need to put heat on overnight. I used a thermocouple in the airflow, and reading whole units only, it said 18C with occasional 17C. So take that as 17.5C. Room temperature said 20C, which was a fraction above the 19.3C the internal thermometer said. It was 9C outside. This was always a compromise setup as extract rooms are largely unheated uxcept bathroom has towel rail attached to HW (not a great idea by someone but i recently went dual fuel with power from Solar) so even if that 17.5C was really 16C, im happy with that.

As for bedroom 'draft'. Its probably wrong to call it a draft from the mvhr as it doesnt originate from the vent. Its more like the convection movement that you get from a radiator, except cooler air from ceiling falling down instead or warm air rising. You cant actually feel it other than my arms are not so hot at night so dont kick the duvet back so much from my torso - still kick the duvet off around my feet which is within a few feet (laterally) of unit above. The only flow of air you can feel from vent is when you put back of hand within a foot or so of vent right at ceiling level.

I am certain that noise is not travelling through fabric of building. Ive done a bit with acoustics and do appreciate that sound travels in weird ways, but cannot see any path that sound can be travelling through the building other than the pipework. This is backed up by hearing - ear on wall, the only place that mvhr is audible is on the two stud walls (they are seperate walls but loosely joined to each other), nowhere else even on brickwork in same room as Mvhr. The other clue is the very directional nature of the sound - i can orientate myself with eyes closed solely on direction of noise - always points my ears in direction of vent.

@dave

Which brings me to same conclusion as djh. Whilst the duct you mention is not metal, (ive not checked for sure so going on offcuts left), but it appears to be a solid plastic pipe (definately) externally foil insulated. So whilst it looks tight through the ceiling, the plastic pipe is unlikely to be touching although i know it was very close to a joist at that point. I take yiur point on mounting. Didnt see for certain but ventaxia instructions shows a top bar (probably metal) that unit hangs from. At bottom are rubber feet keeping unit off of wall. I have supported these feet with metal washers siliconed to the wall to protect it. I may temporarily try some acoustically insulating feet if i can find them in my man drawer. The wall is 20mm Orbry board, an insulated board that as well as having copious amounts of screws holding it to the frame, is also siliconed to it - its not going to move independently of the frame. I was very wary of the possibility of it drumming, and have some acoustic insulation slab as backup that i coukd stick retrospectively on reverse but dont think its needed and may over time cause more problems than it solves.

I think the solution is indeed replacing the supply pipe from mvhr to distribution box with acoustic pipe. I have not yet put my head up in that loft space to see exactly how its configured but suspect from seeing preliminary pipework, there is a horizontal run of plastic pipe, with an elbow of same material as piple to mvhr on right, then the down pipe. Ideally i would like a 1m long flexible attenuator that may replace downpipe and elbow, but looks like the airflow 500mm version is the one that matches the pipe diameter - ill leave selection of that to the experts.

As an aside, ive got a nice thermal image of the mvhr heat exchanger at work. The purple shows cold from the supply filter before it goes through the heat exchanger. The extract filter is other side (Mirror image) and shows no temperature differential from ambient. I assume that supply does not mass through this filter. Once all is sorted, i will probably lag all pipe a bit neater although unless the bottom of supply pipe causes condensation i dont see this as an issue.



« Last Edit: March 15, 2017, 10:33:14 AM by TheFairway » Logged
djh
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« Reply #47 on: March 15, 2017, 01:28:14 PM »

Ideally i would like a 1m long flexible attenuator that may replace downpipe and elbow, but looks like the airflow 500mm version is the one that matches the pipe diameter

Ubbink have 1 m long ones in a variety of diameters:  http://www.ubbink.co.uk/products/ventilation-ductwork/sound-attenuators/Sound-attenuators.aspx
They're available from Passivhaus Store or Roofing Superstore. I bent my attenuator through 90 at one end. You can get reducers from the likes of Ductstore if you need to match different sized ducts.

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Cheers, Dave
TheFairway
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« Reply #48 on: March 15, 2017, 01:59:53 PM »

Thanks. I was under impression from ubbink that whilst flexible, it was not 'bendable'. So good to hear that you made a 90 degree bend. Cheeses me off, for sake of less than 20 the attenuator was omitted. Tiny as a fraction of the ducting cost.
« Last Edit: March 15, 2017, 02:17:38 PM by TheFairway » Logged
djh
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« Reply #49 on: March 15, 2017, 03:44:34 PM »

BTW, where does the condensation drain come out of your unit? I can't see it in the photo.
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Cheers, Dave
TheFairway
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« Reply #50 on: March 15, 2017, 08:51:19 PM »

The image is slightly from above so doesnt show due to angle. It comes out the bottom at the very back of unit as a short flexible hose with 90 bend, then connects to a plastic pipe running behind the stud wall and down through a non return valve, then outside through the wall on right via the existing washing machine drain. It may accound for the almost unnoticable vibration in the right wall. I can get a sheet of paper between mvhr and wall, at least all bits ive tried so dont think its touching - still closer than i woukd have liked though, but thats my fault as walls are not 100% square    facepalm but still straighter than original brickwork.
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marshman
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« Reply #51 on: March 15, 2017, 09:31:34 PM »

IMHO. I don't see the point in an attenuator on the extract/exhaust side unless you're annoying neighbours.

Nearly correct!  No neighbours to annoy but I could hear the high pitched whistlie of the fan when outside when the fan was on high speed and it annoyed me Smiley It has no effect on the noise in the house.


Roger

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3.15kWpk (15xSharp ND210)/SB3000. & 3.675kWpk (15 x Suntech 245WD)/SB4000TL, 10kW GSHP driving Wirsbo underfloor heating from 1200m ground loops. 10' x 7' solar wall (experimental). Clearview 650 Wood Burning Stove. MHRV - diy retrofit. Triple glazing.
TheFairway
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« Reply #52 on: February 13, 2018, 02:37:12 PM »

Ok, one year less a day since my retrofitted MVHR was installed and comissioned.

So, how has the past year gone and has it achieved the objectives?

Objective:
To reduce/eliminate condensation within the property such as on windows and some internal walls.
Improve quality of air.

Why:
After undertaking various renovations (most significantly replacing an open fireplace with an room sealed WBS), we were suffering severe condensation on some windows, some areas of the house with little passing air (inside fitted cupboard and toilet - ok there was some air passing in the latter Grin ) and a small area of the underside of the roof felt to the point that I was getting concerned about our well being, items within these areas suffering from mould, and the construction of parts of the house.


Concerns:
As this was being retrospectively fitted to a property, relatively well insulated and mostly double glazed, but not built to highest air flow standards, not even modern construction, and some rooms (specifically two of the extract rooms and the utility) had little or no heating, I was concerned that our heating bill would rocket and that we would suffer drafts/cold spots.


What was fitted:
Vent-axia Sentinel Kinetic Plus with humidistat and summer bypass, supply pollen filter, wired remote, a radial system consisting of two Airflow chambers, 75mm (?) Ubbink semi rigid round ducting, 3 extract (kitchen, bathroom, toilet), 7 supply (4 x bedroom/office/spare, 1 x lounge, 1 x dining, 1 x utility). The system is fully balanced, so, except in antifrost mode (supply measured at <= 0C), supply airflow equals extract airflow. During the day, the system runs at building regs flows (IIRC theoretically full air change every 2-3 hours), during the late evening and night, this automatically reduces to about half that.


So...

Well in past year, we have had the slightest (you had to go looking for it) bead of condensation on the two bedroom windows - coincidentally? when outside temp around approx 4C. No evidence of condensation/mould in any of the places of issue, especially fitted wardrobe which was making clothes a bit musty - I must admit that I was surprised to find condensation on the inside of the roof felt above the bathroom prior to fitting (which may have been caused by a fault in the old bathroom extractor/pipe work) and there is no evidence of that now. Bathroom still suffers condensation on window when a shower is had, but this clears much quicker than when using previous bathroom fan and tbh, if we manually triggered boost rather than relying on the humidstat this would probably be minimal. The kitchen is similar when cooking with steaming dishes, but again, clears very quickly and certainly not major condensation on the windows.

99% success.

As for improvement in air quality. I am sure that air quality has improved, at very least mould will not be floating around and moisture levels largely kept to very comfortable levels. But its not like sitting outside in fresh air, and the odd odur will still linger - that said, my son who sleeps in a bunk bed is much more comfortable as heat buildup at ceiling height is much reduced. In summer, we tried to run without opening windows, and was largely effective, but there is nothing like a nice breeze blowing through the house - but on hot days with still air, the MVHR provides a little respite where conditions that would probably have led to unpleasant still/stale hot air - so whilst the air movement is not noticable unless you put your hand within a few inches of a vent, or close a door almost shut and feel the flow with back of your hand through the gap, there is enough of an air change to reduce the stifling associated with hot still weather. The pollen filter meant that there were no issues that may have been associated with hayfever as would sometimes happen at certain times of year when windows were open.

Difficult to quantify the success with this. Im not disapointed as its performance, but its not the fresh air feeling that some may have you believe.


Concerns.
Well my concerns were largely unfoundered, especially after reading some peoples reports that MVHR's need particularly airtight buildings. Yes, we are well insulated, but certainly not air tight. I keep meter readings, typically on a week by week basis, and whilst I know that the MVHR will have been consuming 17W during night, 28W during the day (often powered by solar PV), its not distinguishable on the electricity bill over and above what would also have been down to lower Solar generation last year - I once calculated it to be roughly 20-30/year extra and I am sure that is in the similar ball park. As for gas heating, an average indistinguisable from last years not taking in to accound weather, and probably a little less as peak weekly reading since MVHR is less than peak non MVHR readings. However, a couple of rooms at certain times of the day feel slightly less warm. I put this down to a number of factors - first the temparature of the incoming air when very cold outside can be 3C or so less than room temperature - largely due to the extract rooms that heat the incoming air may be at 16-17C - this is bound to make the room slightly harder to heat. Second, the airflow movement distributes the warmth around the room and the house. So we have a couple of rooms, largely unused, where the TRV turns the rad on slightly, where previously this was probably not the case. The up side to this is that those rooms are getting a little heat in them. Finally, our boiler is on its way out and its supply pressure has been reduced to minimum by the service guys. This means that the boiler output is reduced, so when its having to run at higher capacity, ie cold and windy outside and everything is heating up from 'cold' at the same time, not all the rads get as hot as I would expect. Putting this in perspective, when temp outside is sub 0, a bedroom unheated between 9:30pm and 5:30am gets at worse mid 16C overnight and typically 17C something where 18C would have been the bedroom temp setpoint on the runup to bedtime.

The unexpected:
I certainly was not expecting to hear the unit at the far end of the house. I was initially concerned that it would cause problems sleeping in summer when on summer boost modes, but it turns out that I am the only person in the house (including the piano tuner) that can hear it, I got use to it, and it doesn't cause problem in the summer. Sometimes, when outside of 80-90% humidity and inside is hovering at 70% I hear the humidity stat boost cut in, but its not a problem. However, can I suggest, for the sake of 60 or so quid, that anyone else having one fitted gets a couple of inline attenuators fitted.
Second, I sleep quite close to a supply vent - its about 18" from foot of bed on my side, and I think I feel the temperature difference of cooler air being supplied. Its not a draft, just that my shoulders (which I typically have outside duvet) are probably a little cooler than they once were. This of course is a bonus in the summer... The vents come supplied with little baffles that can be fitted to block airflow at some angles - so these can stop any drafts,
I was also concerned that the supply to the main bedroom was not capable of reaching the design spec. It looks like the distance of the vent from the main chamber is far enough to reduce the flow - a second supply pipe would have cured this, but the suppliers were 'reluctant' to fit this without extra cost and coming back and convinced me that the flow achieved was adequate. Seems like they were right as condensation in that ropom is all but gone, but its upset the balance a little.
Which is my final say on the matter. Having lived with the unit for a year now, I am convinced that the balance and room size between source and extracts plays a more significant role than air tightness. In my case, I have 7 supply and 3 extract, which means that the extracts are having to work much harder than the supply. So, especially in case of mine, the extract rooms play a significant part in determining the recovered supply temperature, so if you have a large extract room (ie my kitchen) the temperature of that room will be the major factor in what the supply temperatures will be, ie my kitchen temperature at 16/17C or so is probably influencing 60% of the supply temperature. But airflow at 14C from a room supply vent, when its <0C outside, is not the big deal that some may think, especially when the alternative would be a window open to the outisde at <0C.

Finally:
Installation was about 2k more than I felt comfortable with. Much of this was VAT as it was a retrofit. Not cheap, buts its done its job.
Running costs, Gas immeasurable, electricity probably 20-30/year. Plus 2 x filters, one of these pollen, about 45/year.
Maintenance costs - I cleaned the heat exchanger myself.



Question:
I am after some insulation for the semi rigid ducting. I think it is 75mm outside diameter. I remember seeing some last year on internet, for iirc 10m length specifically for this type of ducting, but cannot find it again. Can anyone help me find the supplier.
« Last Edit: February 13, 2018, 03:52:05 PM by TheFairway » Logged
ecofriendlier
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« Reply #53 on: May 04, 2018, 07:31:29 PM »

Hi, We're looking at retrofitting our house with an MVHR system. This thread is the most informative I've found so far. We're struggling at the moment to understand how we fit the ducting around the existing joists. We are looking ti use the Zehnder Q600 system. Our architect has some concerns on how we'd be able to run the ducting through the existing joists without affecting much of the ceiling / floor. Is this something you guys have faced while retrofitting? The house is undergoing other renovation too and we are also exploring opportunities to make it more airtight. Its a 2 storey detached house. Any thoughts on this will be much appreciated. Thanks.
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TheFairway
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« Reply #54 on: May 05, 2018, 04:55:31 PM »

My retrofit was in a bungalow so everything was pretty much in roof space except MVHR itself, but even though the semi rigid ducting is quite small diameter, its still far too large contemplating running it through a structural joist. Once you work out where vents will go, normally opposite side of room to the door, you will probably find that you will need to run some ducts through a room - either vertically or horizontally in which case finding a way to box the ducts in will be required.
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TheFairway
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« Reply #55 on: May 05, 2018, 04:59:21 PM »

Still after a source for insulation for the semi rigid ducting. I'm sure last year I saw a 10m long sleeve of insulation at correct diameter for about 35 but cannot find anything remotely similar this year.
« Last Edit: May 05, 2018, 05:01:00 PM by TheFairway » Logged
Countrypaul
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« Reply #56 on: May 06, 2018, 09:58:37 AM »

I saw this whilst looking for some extra bends due to an oversight/change in our pipe run: https://www.airflow.com/Product-Detail/pg%5FSRIG/Semi-Rigid-Ducting/90000010/Insulation-

Not sure if it is what you are looking for or not, it certainly doesn't appear to be a sleeve though.
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snyggapa
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« Reply #57 on: May 06, 2018, 09:19:22 PM »

we have this, haven't fitted it yet:

https://www.bpcventilation.com/25mm-foil-backed-glass-fibre-insulation

assume we just cut it, wrap it and silver tape it - seems simple enough

-Steve
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ecofriendlier
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« Reply #58 on: May 09, 2018, 09:47:17 PM »

My retrofit was in a bungalow so everything was pretty much in roof space except MVHR itself, but even though the semi rigid ducting is quite small diameter, its still far too large contemplating running it through a structural joist. Once you work out where vents will go, normally opposite side of room to the door, you will probably find that you will need to run some ducts through a room - either vertically or horizontally in which case finding a way to box the ducts in will be required.


Thank you. Would you be able to provide me the name of the company that retrofitted the MVHR for you please? Thx.
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TheFairway
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« Reply #59 on: May 10, 2018, 05:14:33 AM »

I wouldn't recommend them. Design and fitting team good but office staff/owners wouldn't fix issues that performed poorly/to design criteria and were downright rude -4 they accidentally cc'd me on an email that perhaps they should not have done.

1 - There were issues with noise - should have specified a couple of 20 noise attenuators at the design stage and not suggesting retrofitting some 400 attenuators that had no guarantee of fix
2 - Some rooms (one in particular) not able to supply the balanced design amount of air - should have supplied dual feed to that outlet - caused by length of run
3 - Some ducting not insulated or not insulated sufficiently - contrary to what office said would be the case - not sure what they would have done with the other ducting had I not bought in another 3 roles of insulation prior to the job being started
4 - Some areas of ceiling were pushed out - suspect that pressure was applied from inside ceiling causing it to 'pop' in a couple of places

and probably a couple of other things that I have long forgotted

The fitters were happy to come back and rectify 1 & 2 (#3 prompted the rude email from the office) but the office basically priced #1 out of the equation and argued that #2 was not an issue even though it did not (by a long shot) meet their design criteria.

After #3, all my emails were blocked and I took the view that life was too short to argue and I would see how it went and sort #3 and #4 myself - hence my question re duct sleeving.

That all said, it works well, was more than I originally budgeted for (mostly cost of 20% VAT that they said I could reduce to 5% if they fitted [kept on banging on about and after Grenfell even more glad I didn't take them up on offer] foam spray to inside of roof - anyone that I spoke to said it was a bad idea) and tbh, once I paid several up front for a survey, felt kind of comitted. Don't regret it, but would never recommend the company involved as they constantly try and upsell and when things don't go as promised they shut down all communication.
« Last Edit: May 10, 2018, 10:35:04 AM by TheFairway » Logged
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