Try identify the source of this mould?

cormie

Hey folks,
Posting on behalf of a friend who recently moved into a place they bought. The building is from the 70's or earlier I think and there didn't appear to be any major mould spots when they moved in, some dark patches on the bathroom wall, but this has since been insulated and tiled over, but in a very short time, over only a few weeks, the corner of the side and front wall behind the built in wardrobes got completely covered.

They bleached and cleaned it and painted over with mould paint and it seems to have kept it at bay the last 2 or so weeks it's been on. The walls are still cold to touch but not necessarily wet.

There's a vent on the wall as you can see in the attached diagram and also another vent in the room itself. They dry clothes in this room and my suspicion is that the condensation is getting through the wardrobe doors and as soon as it hits the cold wall before it has a chance to get out the vent, it turns to liquid, stays there and grows the mould and because it's behind the wardrobe and not exposed to the heat the rest of the room would be, it doesn't dry out as easy.

They are thinking to close the vent up completely to prevent it happening again, which could work I guess and then the vent between the windows will be the only vent in the room.

They have also been using a condenser dryer downstairs for clothes, as well as regular cooking, showering etc, so there's probably loads of moisture in the house, a not very well insulated house, so I'm thinking it's inevitable for there to be mould issues.


I'm suggesting they use a dehumidifier, for clothes drying and for general moisture control and mould prevention, but they aren't too keen on this for some reason, even though it's better for the clothes than a dryer would be, probably cheaper too and then has the advantage of keeping the moisture in check.

Is closing the vent and switching to a dehumidifier a good idea?

If anyone has any experience in this field and any comments on the above, it would be great to get some feedback.

Calahonda52

Good analysis of the source of the moisture and the issues caused thereby. Its a classic. Its as if you are writing a text book!
Not so certain as to the proposed solutions.
Closing the vent is wrong.
No so sure about the DH as a clothes dryer, much better to capture an dispose of moisture at source, but maybe i don't follow you fully.

Can you confirm the wall construction?
Can you get them to strip off the wall vent and post some pictures of the wall construction?

Its not clear if the wall vent is behind the wardrobes.

How do the know the walls are mouldy behind the wardrobes, are their no backs in them?

Have they the budget for EWI as a solution?

cormie

Thanks a lot for the reply

So just to follow on from the dehumidifier VS dryer, this was a Q&A from another thread on the topic:

Q: Does anyone know, for drying clothes (either just out of the washing machine or just in from getting soaked in the rain, what are the basic advantages and disadvantages of using a dehumidifier instead of a tumble dryer, if any? ?

A: Well a regular vented tumble dryer loses heat out of the building at a high rate.
With a dehumidifier the heat is effectively recycled again and again which greatly improves efficiency.
There are condenser dryers on the market also but they are quite expensive. Using a dehumidifier in a small sealed room is effectively air drying the clothes just with the advantage of a much lower relative humidity.
Also apparently tumble dryers are very hard on clothes & wear them out prematurely.
Finally a dehumidifier is a much lower electrical load so far easier to supply with PV for example if available.

Indeed, a vented dryer without its hose will quickly put a lot of moisture in the room. A condenser tumble dryer gets around that problem by passing the warm moist air through a heat exchanger to condense the moisture into a container. The running cost is a little more than a vented tumble dryer, but has the advantage of not venting air outdoors. A heat pump tumble dryer is basically the guts of a powerful compressor dehumidifier inside the tumble dryer. They are quite expensive to purchase, but have 1/3 to 1/2 the running cost of a condenser tumble dryer.

The drying clothes feature on most machines puts the dehumidifier into continuous operation regardless of the room's humidity. The lower the room's humidity level, the quicker water evaporates from the wet clothes. With desiccant models, they go into high power mode when put into laundry mode or continuous operation. With a manual dehumidifier, you can achieve the same principle by turning the humidistat knob to 'Continuous'.

Some dehumidifiers start a timer when put into laundry mode so that once the timer runs out, the dehumidifier returns back to the original setting or switches off depending on how the manufacturer implemented the feature. This is especially important on desiccant dehumidifiers that otherwise would continue to draw 600-700 watts until the user remembers to switch it back or until the water container fills up.

A compressor dehumidifier would be a lot more efficient at drying clothes as these thrive with high humidity levels and wet laundry quickly raises the room's relative humidity level. The higher the relative humidity, the higher the extraction rate with compressor models, i.e. more water collected per kWh of electricity consumption, whereas desiccant dehumidifiers extract about the same rate no matter how high the humidity level gets. An oscillating desk fan aimed at the clothes air dryer also helps improve the drying rate.

The drying time with a dehumidifier varies a lot depending on the room temperature, dehumidifier capacity and of course the amount of clothes being dried and the effectiveness of the washing machine's spin cycle. With the Trotec 75S (24 litre compressor based dehumidifier), room temperature around 21C, roughly 5kg mixed load of laundry and a small oscillating desk fan blowing across the airer, it takes about 6 hours to fully dry.

That's some snippets of info, but more details from post #147 here:http://www.boards.ie/vbulletin/showthread.php?t=2057300666




The vent isn't your typical plastic one, it's actually a steel vent which seems to have been laid with the existing blockwork, it was cut with an angle grinder in other rooms to make it flush with the wall, but in the wardrobe it hasn't been cut yet and is sticking out at an angle, but it appears to be just cavity blocks from what I can see through the other vents?

The wardrobes are build in and it was basically just floor-ceiling doors and shelves put against the wall of the room, so there's no backing of the wardrobe, when you open the wardrobe, what you're looking at (behind the wardrobe contents) is the wall and this is where the mould was.

I'm not sure EWI is, but guessing external wall insulation? I think one builder advised against this and suggested to always insulate from the inside?

BryanF

Mound in Cupboard is due to reduced air movement and cold surfaces.

External insulation and proper ventilation is the way to go.

Calahonda52

BryanF wrote: »

Mound in Cupboard is due to reduced air movement and cold surfaces.

External insulation and proper ventilation is the way to go.

+1
OP, keep well and good luck

cormie

Thanks for the replies. If EWI isn't affordable at the moment (Any idea of a ball park price for typical 3 bed gaf?), what other options are there?

The other vent is open too, so that's two vents in the room, so I'm not sure how to get the air moving more? I'm thinking dehumidifier until EWI can be afforded?