Pockets of mould with MHRV

[Onoff]

2 minutes ago, Sensus said:

Pissing competitions don't interest me.

 

Pissing people off's OK though is it?

 

There's ways of getting your point across. Stating your disinterest in other people's opinions or feelings isn't going to win you any friends on here or have them want to engage with you. 

 

As an aside i personally think a badly maintained MVHR system could be a very serious health hazard. On the for side there are people on here who's chronic health conditions have much improved I believe due to well designed MVHR.

[ProDave]

Play nice gentlemen. The moderators are already discussing this.  Let's concentrate on helping the OP with his problem rather than willy waving please.

[ToughButterCup]

@Sensus, please excuse me.  I'll step out of this thread now.

Apologies to  @phatboy

[Onoff]

@phatboy, was there any sign  of mould before the MVHR?

[phatboy]

Wow it seems I've kicked off quite the debate here!  I appreciate all the advice, so I'll reply!

 

I really appreciate all the replies, and it seems my 'simple issue' may be far from it!

 

5 hours ago, scottishjohn said:

so you have a solid wall -- not 2 walls with a void between them ?

is it hard plastered onto that wall?

I am guessing you fitted mvhr because you had a damp problem before 

 can you see the damp course from outside of house?

how far above the ground are the air bricks -damp course sdhould be below them  and visible --not banked up with soil or anything 

 

 

Yes solid walls, no void.  9" standard blocks laid on their side.

Hard plastered, existing cement parge coat, existing skim, then a re-skim re-done when we moved in.

Yes HMRV was fitted as after all the insulation works were done, some corners and behind the bed still got a bit of mould, but nothing like when the house was uninsulated.

The damp course could be seen until the EWI went up.

Air bricks vary as we are on a sloped plot. Closest is about 2" above ground level, the ground is a paved driveway.  We are also on sand.  Air bricks are DEFINITELY below the DPC.

 

4 hours ago, Sensus said:

 Bluntly, I wouldn't consider that type of property to be suitable for MVHR.

 

Whatever the PassivHaus bunnies will try to tell you, the level of ACH and distribution of air circulation that you can achieve with MVHR is woefully inadequate even for very well insulated, modern properties (though in these the bigger problem is build up of pathogens rather than moisture). Using it in a property of yours' age and construction was never going to be a good idea: you need a LOT more ventilation than it can practicably deliver.

 

 

I hope not, as it's all now in!  The issue I guess with lots of ventilation is the draughts.  I won't question any more on what you said until I've had a chance to read fully the other thread JSHarris has linked.

I was pretty sure the issues we were experiencing were due to air not moving enough, and MHRV seemed a better choice than PIV.

 

4 hours ago, Mr Punter said:

I know you have the light switches in place, but could you try rotating the bed and have it against the internal west wall?

 

Technically yes, but it would pain me hugely, and the wardrobes would need to go against the north wall, probably making things worse!

 

 

4 hours ago, JSHarris said:

On balance I'd say that a house with MVHR, even if the airtightness isn't to PHI levels, is likely to have better air quality than one without.  MVHR isn't going to fix problems caused by internal surfaces dropping below the local dew point through, especially if they happen to be located in a ventilation dead space.  Something like the small fan and timer I knocked up might be a solution for such a problem, if it isn't practical to improve the insulation in that area.

 

Re-assuring to know you fixed the same type of issue in the way I proposed.

 

3 hours ago, Declan52 said:

Could you open the ceiling vent up a bit more to try to increase the flow rate a bit more.

 

I could, however I don't want to over-ventilate and get a cold shoulder at night.  It may be something to trial!

 

4 hours ago, Mr Punter said:

Where do you dry the laundry?

 

Usually in the tumble dryer, which has an extract vent almost directly above.  Sometimes it's done around the house, but the experience of others seems to be that with HMRV that's OK?!

 

3 hours ago, ProDave said:

Back to the OP.  You mention "moisture from the shower"  Do you just have the 1 bathroom, or are you saying there is an en-suite shower in this bedroom?

 

One thing that strikes me is you have 5 fresh air points but only 2 stale air extract points.  I would try adding an extra stale air extraction point to bedroom one at the opposite corner to the existing fresh air point. 

 

Yes just the 1 bathroom, we dream of an en-suite!

 

There are 3 extract points: Bathroom, kitchen and utility room.  It would be tough to add another now... the loft has been insulated and floored over.  The mould does form very close to the supply valve though, near floor level.

 

50 minutes ago, Onoff said:

@phatboy, was there any sign  of mould before the MVHR?

 

Yes there were, that's pretty much why I installed the system.  The moisture was always worse in this room, but all rooms experienced mould in the top corner where 2 outside walls met.  And behind furniture close to the wall, even with it all spaced off 2" with timbers.

 

As suggested by @ProDave, I do already have an IR thermometer, used for sick children.  It does have a surface monitor setting which I used extensively last year  Right now, the north wall in that room is showing 1.5degree Celsius cooler than all other walls (roughly).  I'll gather more stats tomorrow evening, even better if it's a cooler day.

 

Thanks again all.

Tim

[Declan52]

3 minutes ago, phatboy said:

 

I could, however I don't want to over-ventilate and get a cold shoulder at night.  It may be something to trial!

 

 

By opening the vent more you will be allowing more fresh air in which will hopefully push out the damp air via any leakage in the room. 

But as you say you can only open it so much before you will feel it in your bed. 

[Onoff]

So in your wall buildup you don't have actual vcl? Your relying on the parge coat for air tightness?

[phatboy]

11 minutes ago, Declan52 said:

By opening the vent more you will be allowing more fresh air in which will hopefully push out the damp air via any leakage in the room. 

But as you say you can only open it so much before you will feel it in your bed. 

 

Worth a shot I suppose! I'll soon be told if it's a problem.

 

2 minutes ago, Onoff said:

So in your wall buildup you don't have actual vcl? Your relying on the parge coat for air tightness?

 

No actual VCL correct.  I never did an air tightness test before commencing, intended to run the supply side of the system higher in order to compensate for any leaks.  I've made damned sure the windows and doors are well fitted though.

 

I knew I was never going to get to a passive house level with this place, to be honest at the beginning I didn't even know about it, I just knew black mould up to chest height on all of the north and east side was not on!

[Jeremy Harris]

There's a consultation at the moment going on for the Future Homes Standard.  As a part of that there is a paper on ventilation, that highlights some failings in air quality in houses built in the last decade or so: https://www.gov.uk/government/publications/ventilation-and-indoor-air-quality-in-new-homes

 

It's worth a read, as it supports the views I've expressed here before that trickle ventilators don't seem to work well in practice, and that many MVHR systems are badly installed/set up/balanced.  We've seen examples on the forum recently of a ventilation system that aren't working properly, as well as one installed in a new build a decade ago that had clearly never worked from the day it was commissioned.

 

 

 

 

[phatboy]

8 minutes ago, JSHarris said:

There's a consultation at the moment going on for the Future Homes Standard.  As a part of that there is a paper on ventilation, that highlights some failings in air quality in houses built in the last decade or so: https://www.gov.uk/government/publications/ventilation-and-indoor-air-quality-in-new-homes

 

It's worth a read, as it supports the views I've expressed here before that trickle ventilators don't seem to work well in practice, and that many MVHR systems are badly installed/set up/balanced.  We've seen examples on the forum recently of a ventilation system that aren't working properly, as well as one installed in a new build a decade ago that had clearly never worked from the day it was commissioned.

 

That's a lotta reading!!  I will have a look properly tomorrow.

 

I'd like to think my system is well installed - I took a lot of time over it, as it was to be for my own benefit / enjoyment.  As you have probably seen elsewhere I had considerable issues with the balancing but I think that's resolved now, I'll be re-measuring everything this week sometime to confirm.

[Jeremy Harris]

11 hours ago, phatboy said:

 

That's a lotta reading!!  I will have a look properly tomorrow.

 

I'd like to think my system is well installed - I took a lot of time over it, as it was to be for my own benefit / enjoyment.  As you have probably seen elsewhere I had considerable issues with the balancing but I think that's resolved now, I'll be re-measuring everything this week sometime to confirm.

 

 

The key points in that report are that poor ventilation caused by, amongst other things, badly installed/commissioned/used mechanical ventilation has contributed to high humidity levels (especially in bedrooms) and the occurrence of mould on walls.

 

We are still going up a learning curve when it comes to ventilation in mass built homes, I think.  From the time that man first built shelters, up until around 20 to 30 years ago, dwellings had pretty good ventilation, courtesy of fires.  A fireplace and chimney is an excellent and powerful ventilation method.  It wastes a lot of heat, but it does shift a great deal of air.

 

Once we shifted to building houses without fireplaces, improving airtightness and relying on central heating, we lost a key means of ventilation.  We've been creating building regulations to try and make up for that loss of "natural" ventilation, but the evidence seems to be that those ventilation systems may not be working well in practice.  There seems to be a fair bit of evidence that building inspectors haven't been properly checking that mechanical ventilation systems comply with the regs.  This doesn't surprise me, mine wasn't the slightest bit interested in the commissioning report I produced, and others here have reported much the same thing.

 

I'm sure your system is working as well as it should, as you spent a lot of time getting it adjusted and commissioned so that it complied with the requirements in Part F.  I suspect the wall is just getting a bit too cool, and the vagaries of air flow around the room, and behind the bed, are conspiring to cause the problem you're having.

[Onoff]

If that wall is "cold" couldn't you just redo in insulated pb? You'd need some back box extenders for the electrics. Probably not what you want to hear as a suggestion...

Edited October 14, 2019 by Onoff
Spelling

[Ed Davies]

How about running de-humidifier in the room for a few hours a day? It'll drop the relative humidity and provide some heating, a bit more than the amount of electrical energy it uses as there's also heat released from the water it condenses.

 

Some friends had a rural house in the north of Scotland which relied on convection to get heat from the wood burners downstairs to the upstairs bedrooms. Not surprisingly, the upstairs was pretty chilly and suffered from mould. I suggested a dehumidifier which solved the mould problem and warmed the bedrooms up a bit. Since then they've bought a larger but similar construction house, which at least does have radiators upstairs, and now have 3 scattered around.

[scottishjohn]

 

did they fit a vapour barrier before fitting EWI

I would get a moisture test meter to start with and  make sure  its not coming from walls

 ,pretty sure its a combination of a very cold if not damp wall and lack of ventilation 

 

as suggested redoing the inside of exterior walls  with 50mm- 75mm insulated plasterboard will make a huger difference  and easy to fit with dot+dab ( stick it to exsisting wall with occasional screws 

Edited October 14, 2019 by scottishjohn

[Ferdinand]

One option not mentioned is to put a traditional tubular loft or airing cupboard heater behind your bed. About £25.

 

Say 40W or 80W and could presumably go on a timer.

 

https://www.screwfix.com/p/dimplex-ecot2ft-wall-mounted-tubular-heater-80w/1796F

 

https://www.screwfix.com/p/dimplex-ecot1ft-wall-mounted-tubular-heater-40w/3951f

 

May be just the right amount to rebalance things, and raise the temp of that wall. 

 

Everso simple:

Quote

• Thermostat Control
• 1 Heat Setting
• 1 Year Guarantee
• 80W
• No Timer Function
• Non-Programmable
• Wall-Mounted
• Even Heat Distribution Across Heater Body
• Discreet Mounting Brackets
• Reversible Left or Right Hand Cable Entry

 

F

 

 

 

Edited October 14, 2019 by Ferdinand

[Jeremy Harris]

+1 to @Ferdinand's suggestion.  I fitted one of these in the airing cupboard at our old house, after the hot cylinder had been removed when we changed to a combi boiler.  I also have one in our water treatment shed, on a frost thermostat, just to protect things from freezing.  One would easily hide away behind the bed, and if run from a time switch wouldn't cost much to run.  At a guess I would think the 40 W model might well be enough, as all that is needed is a small temperature increase, plus a bit of air movement from convection.  I suspect that the air movement from convection might be just as useful as the warming effect on the wall.

[Ferdinand]

7 minutes ago, JSHarris said:

+1 to @Ferdinand's suggestion.  I fitted one of these in the airing cupboard at our old house, after the hot cylinder had been removed when we changed to a combi boiler.  I also have one in our water treatment shed, on a frost thermostat, just to protect things from freezing.  One would easily hide away behind the bed, and if run from a time switch wouldn't cost much to run.  At a guess I would think the 40 W model might well be enough, as all that is needed is a small temperature increase, plus a bit of air movement from convection.  I suspect that the air movement from convection might be just as useful as the warming effect on the wall.

 

I did not mention it specifically but it comes with a thermostat.

 

We used to have a single wire version of one of these that was about  5 feet long behind a run of wardrobes at the old stone farmhouse.

[Cpd]

6 minutes ago, JSHarris said:

+1 to @Ferdinand's suggestion.  I fitted one of these in the airing cupboard at our old house, after the hot cylinder had been removed when we changed to a combi boiler.  I also have one in our water treatment shed, on a frost thermostat, just to protect things from freezing.  One would easily hide away behind the bed, and if run from a time switch wouldn't cost much to run.  At a guess I would think the 40 W model might well be enough, as all that is needed is a small temperature increase, plus a bit of air movement from convection.  I suspect that the air movement from convection might be just as useful as the warming effect on the wall.

also did this in a bathroom before fitting an extractor fan as the windows were always shut...... sorted out the problem until the fan was fitted. I have also allowed space and an electric socket  for one to be fitted in my water treatment plant / cupboard as it’s outside. 

[Cpd]

Out of interest @JSHarris what frost protection unit did you use, the heater I have has no thermostat. 

[Jeremy Harris]

7 minutes ago, Cpd said:

Out of interest @JSHarris what frost protection unit did you use, the heater I have has no thermostat. 

 

 

One of these from Screwfix: https://www.screwfix.com/p/drayton-rts3-24003sx-frost-thermostat/9578r

 

I have it set to come on at about 5°C, the mid-point on the dial.  I'm pretty sure it's never come on, though, as the temperature in the shed doesn't seem to drop below about 8°C, even in cold weather.  That's probably because it's fairly well insulated, plus there are two 300 litre pressure vessels in there filled with water at around 8°C or 9°C.  There's a lot of heat stored in the pressure vessels and the filtration tanks, plus there's usually a fair throughput of water, so the shed doesn't normally have much time to cool down.

[phatboy]

Sorry for the terribly slow reply.... family life happened and nothing else got done!

 

Since starting this thread we no longer have pets in the house, and so the bedroom door now remains open when we are home (Someone is here most days).  This seems to have cured the issues during the recent cold spell, so the issue seems to have been that the room just inadequately heated - it has a 800w panel heater that's always on and is set to keep the room at about 18 degrees.

 

Last year, before the MHRV was fitted, we did run a dehumidifier for 2 hours each morning and that kept things mostly under control, except for the corners.

 

Thanks for all the replies, much appreciated.

 

Tim

[JFDIY]

So is there also insufficient air movement to the rest of the house, do you have a 10mm gap under the door?

[phatboy]

1 hour ago, JFDIY said:

So is there also insufficient air movement to the rest of the house, do you have a 10mm gap under the door?

 

I don't know really, there is the required 10mm under the doors.  The room has a supply valve, so heat isn't likely to be sent into the room from the rest f the house when the door is closed?