Problems with a VMC

[vin et fromage]

Hi I am new to the forum and hope someone can throw some light on a problem we are having with a newly installed VMC unit. Moh installed a brand new unit in the loft which we purchased from Leyroy Merlan recently. We watched the video and read the instructions back to back several times. However the plastic tubes which go from the ceiling outlets into the unit are filling with water( quite a lot of water) so we have had to turn it off. There is a correct chimney outlet pipe fitted on the roof ( which in itself cost over 50 euro), We purchased it because of the problems we have with condensation and the cost of getting a trades person in( over 1800euro) moh is usually OK with most things he takes on despite being g 71. However this is baffling us as to why so much water is sitting in what should be extraction pipies for the air from our rooms. Possibilities 1. Water getting in the roof vent and going back through the machine into the pipes 2. Condensation ( loft space is very very cold area) sitting and amassing in pipes. I noted in some brico shops insulated sleeves for the pipes which left me thinking it must be a problem. So anyone got any ideas or had a similar problem. Any help would be greatly appreciated. OH not looking forwards to roof climbing at 71. VMC being an air filtrstion system which changes the air on your rooms and is suppose to help extract the moist air that contributes to condensation.

[lindal1000]

MOH says condensation. The pipes are normally installed under the loft insulation, or the pipes themselves need to be insulated..in his opinion.

[Chancer]

[quote user="vin et fromage"] We purchased it because of the problems we have with condensation and the cost of getting a trades person in( over 1800euro) [/quote]

 

I suspect that the answer may be within what you have not said re the above, could you please expand on it.

[andyh4]

I have to agree with Chancer. Condensation in the pipework suggests either an awful lot of moisture in the air in the house and/or very cold temperatures in the areas where the pipework is installed.

You need to insulate the pipes and probably the VCM itself and probably increase the temperature of the air being extracted to the VCM.

[EuroTrash]

"We purchased it because of the problems we have with condensation"

seems to be answering your own question.

Have you looked into the reasons why you have this problem in the first place? If there is an underlying problem with damp or poor ventilation throughout the house, installing a VMS won't solve it. All it can do is help lessen the symptoms but it sounds as if they are too much for it to cope with.

[Chancer]

It absolutely will cure it or at least minimise it to make the place habitable, my outbuiding flat here in France was black with mould from floor to ceiling (unbelievable it was the kitchen for the hôtel[:-))]) and my timber chalet in the UK which is unoccupied and unheated most of the year was equally uninhabitable, both would have been condemned and demolished by now, VMC's have made both safe to live in although I'm in no hurry to look Inside the gaines!

Editted, you said it would not solve it, just reduce the symptoms, you are right, I read your reply too quickly. The VMC's solved my problems ie. uninhabitable became habitable,  the moisture is still getting in but is removed by the VMC before it can condense Inside, I have no doubt that its condensing in the gaines but dont care until it starts leaking out.

Back to the OP, if the VMC was installed to remove excess humidity from the dwelling then you are right, if the root cause like a leaking gutter or rising damp can be tackled to minimise the problem it should, however the VMC will remove it in most cases but it is no surprise that the water vapeur will recondense in the pipes as soon as they are in a cold area, if it bothers you (it doesnt me) then you should do as Lindal has said.

 

I would never ever have a VMC double flux because they are an absolute nid de microbes as are to a lesser degree uninsulated gaines, current regs although they make U turns all the time call for solid plastic gaines, a trappe de visite and that they should all be cleanable, there was talk of a maintenance contract being obigatory but that has been quietly dropped no doubt because of the danger involved in exposure to the bugs on a regular basis.

[vin et fromage]

Thank you everyone, there is no leaking roof, have put air bricks in all rooms, have 2 extractors in the kitchen one over hob one on wall. In a previous life moh was a heating and ventilation engineer ( qualified) and he is baffled by the ount of water in the outlet hoses. We had some come to estimate the cost of putting polystyrene walls up on the outside of the house, which is a fairly new technique they then apply a blown crepe onto that. But the cost was far too prohibited 32k to encase a our small soys sol. The outside mortar is blown but can't be replaced because its breeze block and Salamanca construction, hence the polystyrene possibility. The air fliw in the house is good, but two main problem areas main bedroom and to some degree kitchen. The reason I adked the question was go see if anyone had fitted a VMC and had a similar problem or knew of someone who had. I am thinking it could be condensate in the loft pipes and will def look at insulating them. When we first came here 13 years ago we haf old ill fitting windows and some loft insulation. We now have double glazed windows and good loft insulation but we seem to have made the problems worse. Our spare bed room doesn't suffer to bad unless someone is usk g it full time, as our son did a few years back. Thanks anyways for all the replies.7

[pip24]

Hi.

Have you thought about buying a dehumidifier ?

Our vmc is good and solved a damp problem. However my daughter had the same problem as you. To make the situation worse the condensation leaked out and ran down a conduit into a light switch !

[Chancer]

The VMC is doing its job well as they all do, its removing moisture laden air and replacing it with fresh air which at this time of year is likely to be quite moist anyway, the extra humidity in the occupied rooms comes from natural perspiration, washing bathing showering and cooking, if you have any doubts just turn off the VMC and see how much damp and condensation you will then have in the rooms.

 

The moist air being expelled will of course condense in the extractor gaines if they are in an unheated area especially if that loft space is insulated from the rising heat from the rooms below as it should be, if it causes you a problem you have 3 choices.

 

1 Use insulated gaine which I'm not convinced will do a lot other than sell you hope and mpty your pockets.

 

2 Run the loft insulation over the gaines - my preferred option.

 

3 Ignore it and pretend it isn't happening, my current solution.

 

I have done external polystyrene insulation with a blown crepi finish and it cost me approx €3 / m2 Superb looking and durable finish come spring I will be doing the same to the Inside of all my exposed tole bac-acier in the outbuildings to brighten them up, make them warmer, quieter but mainly to stop the drips on days like today.

[vin et fromage]

Thanks Pip24.  We emptied the conduit pipes 2 days ago and got 3/4 mop bucket of water. Its been really cold and freezing outside here in 79 the last few days so I guess its condensation building up in the loft pipes.  This morning a small puddle of water on tiles in hall and drips of water coming from air vent which goes into the loft.  We have turned the electrics off to the machine at the moment until such times as moh can comfortably go up in the loft and lag the conduit.  I thought it may have been water getting into pipers via the roof outlet, but it hasn't rained since the last time we drained the pipes so I guess insulating them may improve things.  We went to the expense of installing one because all things pointed to the fact that it would help, but we have now got another problem to solve. MOH is also going to build some walls using the metal framework and studding with polystyrene backed plaster board to improve the warm air hitting the colder outside walls, which causes the black spores to appear. I have had a dreadful cough for the last 8 years, every winter and the thinking by my doctor is that the condensation on the walls is not helping with this.  So we shall have to see what happens.

Thanks for your contribution.

[vin et fromage]

Thanks Chancer, I think you are probably right with the conduit in the loft, its that cold up there I saw a brass monkey looking for a welder last week. (Sorry northern joke).

The air in the  house felt fresher when we first used it in Sept (after we had installed it) but the huge collection of water in the pipes and having it seep back through the ceiling vents worried us. So I think the next step is to insulate the pipes, seen them in the bricos but they are not cheap. Or we may well wrap insulation round them and secure with string or some such thing. We love where we live but having to wipe black the stuff off walls every couple of weeks every  year is getting to be a pain. Still we are luckier than some we live in France so I suppose if this is all we have to complain about.

Did putting the polystyrene on the outside improve the warmth of your outside walls (inside hte house) if you get my drift. MOH is thinking about building some false walls using the metal studding and polystyrene backed plaster board to improve the outside walls, starting in the master bedroom which is where the main problem seems to be. (We shall have to stop breathing at night I  think). We also noted that around the windows (installed 6 years ago) they didn't fill the cavities between the frame and the brick work, they just put PVC  coving over it to make the finished job look OK. We note in our bedroom that around the window and on the wall gets particularly wet and damp. So before putting up the false wall, we shall fill the gaps with that expanding foam which should help.

[Gluestick]

Rather a complex problem, I fear.

How old is your house? What is it built from?

Unfortunately, traditional French houses had no DPC (Damp Proof Course) and no membrane under the plinth. That said, they enjoy a form of natural conditioning; in theory. Indeed, old Southern Farmhouses, (mas), were constructed from local stone and the mortar used was lime.

Bright sparks renders the exteriors with modern cement. Big Mistake! Cement is impervious to moisture; and thus the building is unable to breathe, the lime mortar dries right out and cracks and the house tends to fall down!  Precisely the same with old Norfolk flint cottages.

Identical problem with Victorian houses where the DPC was made from bits of broken slate roofing tiles. Solution? Whack in a concrete plinth, neatly extending above  the level of the DPC and then wonder way the damp becomes even worse!

VMCs were actually created for modern "Sealed" houses. Part of building regulations in many jurisdictions. Why? Since twin and tripe double glazing, draft-free exterior doors and no older-style ventilation (e.g. wall vents under wooden floors sustained by small brick piers and joists) allowed the underfloor cavity to breathe and stay fresh; same with roof cavities, by using a vent tile.

A super-insulated modern house neatly ignores the core reality of people living in it!

Cook by gas? Fine; where does the air come from to provide oxygen for the combustion process?

People living in houses make moisture: take a shower; boil a kettle; use a coffee machine; live!

Result? Moisture! If you go to bed and place a sheet of polythene over your legs on the top of your duvet (Or sheets, blankets and eiderdown), well, come the morning and the dickies tweeting, your duvet will be soaking wet!

A proper house ventilation system has three primary functions: first, it extracts "Stale" Air and mixes this with a small amount of fresh air: human beings tend to like respiration! second, it extracts excess moisture, to adjust the humidity level to a correct balance between too dry and too damp; third, it extracts heat which otherwise would be wasted. Extraction vents tend to be sited at floor level; incoming treated air tends to arrive at ceiling level. Why this way round? Simply because heat rises: it is a natural phenomenon called Natural Thermo-Cycle. Clearly, one doesn't really want to heat a building and then proceed to dump this - expensive - heat to atmosphere!

You can prove this in a heated room by simply standing on a pair of steps, in Winter and try to breath just under the ceiling!

Now, one of the problems with any sort of heating and damp, is heated air absorbs much greater amounts of humidity (moisture): until it hits a much colder surface (Exterior walls, tiled floors etc) when the effective Dew Point causes condensation. Take a nice hot shower; the mirror tends to mist up and you wish you had windscreen wipers on the damned mirror! Or perhaps a heated mirror glass.

Heat the bathroom and you have simply cased a larger effective heat differential. Extractor fans sited over the shower alleviate this problem; yet, of course, suck out heat, too! The fan inlet tends to be sited high up in the room; nice idea, as you can see the clouds of steam (Water vapour rising. But then, you are also sucking out heat! Which lowers the room fabrics ambient temperature and guess what? Encourages condensation...

From your various descriptions, I would suggest the first thing must be to ensure you have no rising damp; no falling damp. That said, by your latest comments, reference black mould, then you have a serious damp problem, which the best VMC ever made will not cure; only alleviate. Check all gutters and ensure the damp is not caused by faulty gutters, downpipes etc.

Check the roof; what can appear as minor roof leaks, cracked tile. can often flow directly into the wall fabric. had one of these in one of our properties. Hard to find. An Early Edwardian terrace with extra bits stuck on the end and one cracked tile, caused huge amounts of water to flood the wall, over time. In the end, I had to instruct my contractors to hack off all the plaster and redo. Tore what's left of my hair out trying to find this one!

Check the ground level on the exterior walls. Is there, for example, a badly created terrace which is allowing excess damp to migrate into the walls?Any plumbing leaks?

What type of heating are you using?

By the way: windows. Leaving a large unfilled gap created what is called a Thermal Bridge. The best insulation ever is compromised by such a bridge; can be brick, cement, wood or air.

Expanding foam should cure it.

Additionally; the air extraction tubes are taking moisture-laden air at a relative high effective temperature into a cold unheated space and instantly, the Dew Point is breached and the moisture condenses out. Solution: either super-insulate; or better, wind heating wires around the tubes and then insulate over the top. Since the correct place for moisture extraction is inside the VMC box; not the pipes!

[woolybanana]

Phew, Glooey, did you have a drink before, between or after that lot? Good sense though.

[Loiseau]

Not sure if it's relevant/helpful here but, if you have double glazing, you might need some discreet extra ventilation over the windows.

Angela

[mint]

There could be lots of explanations but, for starters, is the outside ground level higher than the inside floor level?

Is the bedroom (the worst room for damp), the furthest room from the kitchen where most heat is generated?

Are you in full- or part-time occupation?

NOT teaching my grandmother to suck eggs, but do you open doors and windows to ensure good ventilation?

As, Loiseau has said, do you have trickle vents on the tops of your double-glazed windows?

You might have rising as well as penetrating damp?  Rising damp doesn't go much more than a metre or so above the floor in normal circumstances.

Do you live in a situation, for example, on a flood plane or an area of high rainfall where damp penetration be it through floor, walls or roof, is more likely?

Yes, I know, more questions than answers apparently but you need to ask questions to arrive at the causes and some are not as obvious as others. Sorry, can't help re your specific VMC questions.  Best to ask a local tradesman who deals with these.

[woolybanana]

Do you open the windows?

[mint]

Do keep up, Wools, I've already asked whether he opens doors and windows to ensure good ventilation!

For part-time occupation, it's essential to air rooms well before locking up.  Haven't we all had a shower, grabbed a cup of coffee and locked up quickly before leaving to catch the ferry?  And all that moist air is locked up inside!

[BJSLIV]

Are there any kinks , or troughs in the extraction pipes. That will encourage the formation of puddles. The pipes are supposed to as straight an incline as possible. The theory is that the water should runs back in tiny quantities before it accumulates enough to be a noticeable problem.

Two thoughts.

1 In which of the pipes is the water collecting?

2 The room with the worst mould, is it kept warm all the time?

[Gluestick]

Neither prior nor post, Wooly.

Suffered similar problems with our place; an area of notorious high water table. So much so that when  neighbours and now friends, built a new house opposite, the relevant department in the Prefecture refused point blank a permit for a cave. Might have been possible if he had been happy to spend a fortune created a complete tanked design.

Whilst the original dwelling was circa 200 years old and constructed from Torchis, which the elderly French gent we purchased from rebuilt completely using double brique perforés terracotta.

Lovely floor tiles throughout, which Mrs G and I love. No membrane though ! [:'(]

No DPC either... [:(]

Thus early on, my first port of call was research, research and research.