Tenants blocking vents causing black mould

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Tadaima

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Last year our tenants complained about black mould on the walls. We immediately contacted a plumber to find the source of the damp. He said it was because the tenants had blocked the vents and were using a dryer daily. He told us to tell the tenants to use the dryer properly (they were not emptying the water), use the fan above the cooker, unblock the vents and open windows occasionally. The mould keeps returning. We got a second professional opinion which agreed with the plumber. The tenants refuse to take responsibility and say the house is affecting their health. They have been given notice according to RTB guidelines. Any advice on how to deal with this in the meantime?
 
Assuming you want this issue dealt with once and for all, answering the following q's in as much detail as possible will help to identify a permanent solution.
1. Is the black mould appearance seasonal? (i.e is it more pronounced during the heating season, for instance)
2. Where is it appearing and is there a "pattern"
3. What age and type of property?
4. How long have you had the property and has this been an issue from the start or just the current tenants?
 
Micks'r said:
Assuming you want this issue dealt with once and for all, answering the following q's in as much detail as possible will help to identify a permanent solution.
1. Is the black mould appearance seasonal? (i.e is it more pronounced during the heating season, for instance)
2. Where is it appearing and is there a "pattern"
3. What age and type of property?
4. How long have you had the property and has this been an issue from the start or just the current tenants?
Click to expand...
Thanks Micks'r:
1. All year.
2. The Kitchen - all walls.....for past 2 years. The hall, stairs and landing in small patches in recent months.
3. 70 years old. Has double glazing and oil fired central heating.
4. 10 years. This issue was not in the house before with previous owner occupiers (20 years) or tenants (1 year). The house lay empty for 2 years previously without heat on and there was no mould during that period.
 
* 3. To add.......it is an ex local authority end of terrace house with a conservatory off the kitchen.......added 30 years ago. The original back door separates the kitchen from it.
 
Have pictures of the interior before and after of previous tenants and of the property with the current tenant. Expect them to raise a dispute with RTB and even a doctor's report. I would advise them they are damaging your property and will be liable for repairs. You haven't a hope of getting that from them, the best you hope is to retain the deposit, assuming they actually get out.
 
Assuming the house is a 2 storey and depending on the layout, I would advise to install a low noise long life continually running simple mechanical extract ventilation (MEV) system in the attic space (extracting from the main bathroom ceiling and out through a roof vent). This will "override" your tenants (current & future) inaction in airing the house properly. Remember that any house, no matter how well built or otherwise, will develop a damp / mould problem if the right conditions are allowed by the occupants (and often due more to unawareness than malice).
All the above is predicated on there being no active leaks in the property.
 
What are the costs of a MEV and what are the running costs. For an average 3 bed semi say 1200 sq ft
 
I am not involved in installation but I'm sure install costs vary quite a bit depending on, for instance, availability of fused spur, attic layout, number or wet rooms to be evacuated etc, but I would expect a non complicated install to cost somewhere in the 800 to 1200 ballpark. Annually nett running cost would be negligible (or even negative!) as you would also expect to get savings on heating costs as the house structure and insulation (if present) will be dryer and thus significantly more insulating.
 
In a house with no previous mould, to cause this much mould, the tenants would have to causing sauna like conditions.
Would a MEV be able to cope with that.

The issue I would have is you'll probably find everything is bing damaged, soft furnishing, timber, plaster, electronics.
 
Running a portable dehumidifier in the impacted rooms could be a solution. It has worked for me in the past.

You could buy the tenants one, but they would have to diligently use it and empty it.
 
I have seen a simple thing like changing from an open fire to a stove causing significant issues so I don't agree with your comment re "sauna like conditions". There are many variables at play in all houses with occupant behaviour being one of the dominant variables. What an MEV system will buy you is it will give you continuous consistent ventilation regardless of who occupies the dwelling resulting in a dryer internal environment.
 
NoRegretsCoyote said:
Running a portable dehumidifier in the impacted rooms could be a solution. It has worked for me in the past.

You could buy the tenants one, but they would have to diligently use it and empty it.
Click to expand...
Yes, this should work on a temporary basis and perhaps this is the type of solution the OP is looking for.
Where the OP is looking to future proof, I doubt running a de-humidifier longterm would be suitable though.
 
Micks'r said:
I have seen a simple thing like changing from an open fire to a stove causing significant issues so I don't agree with your comment re "sauna like conditions"
Click to expand...

I agree. A house we bought had mould when we moved in (previously tenants). We removed it and and none more emerged when we lived there, but I was diligent about ventilation.
 
another alternative is positive input ventilation (PIV) which pulls fresh air into the attic and pumps it into the house (https://smartheat.ie/product/drimaster/ - not an endorsement, site just came up on Google). I'm pretty careful about ventilation and we have a dehumidifier in the room where we dry clothes, but we still get mould in some rooms, considering PIV as an option as I've seen it recommended in a number of places.
 
shweeney said:
another alternative is positive input ventilation (PIV) which pulls fresh air into the attic and pumps it into the house (https://smartheat.ie/product/drimaster/ - not an endorsement, site just came up on Google). I'm pretty careful about ventilation and we have a dehumidifier in the room where we dry clothes, but we still get mould in some rooms, considering PIV as an option as I've seen it recommended in a number of places.
Click to expand...
True, PIV is another option.
With MEV, you are drawing dry air in through the structure and therefore they is near zero risk of interstitial condensation occurring somewhere within the structure.
The issue I have with PIV is that you are effectively pumping warm moist air out through a cold structure which, imo, is never a good idea for obvious reasons.
 
I assume that they have a extractor on the cooker hob, and that they do not dry clothes in the house
 
Thank you for all your most informative replies. I will look into both MEV and PIV options. MEV seems to be what we are looking for. Páid.....yes it is like "breaking a window then complaining about the draught." I do suspect the tenants will use the mould against us even though we have got tradesmen to point out to them that it is the way they are living. When we have gone over for repairs......it is indeed like steam room conditions when they cook. They will not open doors or windows or use the cooker fan. Strangely they rarely put on the heating as they complain of the cost yet have the dryer on all the time....which costs a fortune in electricity. I know it is their business how they live, but they have damaged our house well beyond normal wear and tear with their lifestyle. (When this house is sold I will never rent again. I'm 24 years renting to others but recent legislation changes make it impossible).
 
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