Eric S

We have an apartment in northern Spain. We rent it out Sept - June and use it ourselves in the summer. Our renters have told us there is a problem with condensation and mildew in the winter. We're wondering if anyone has any suggestions on how to deal with it.

It seems that there is a lot of humidity in the area in winter. The renters have told us that they see condensation on the exterior walls, windows, and ceiling (the apartment is on the top floor). Like what you would see on a bathroom mirrow after taking a shower. This causes mildew to form. While it's easy enough to clean off, but we hate to have our renters deal with that.

My guess is that the wall are not well insulated. So when the warm, humid air touches the colder walls and ceiling, it condenses.

Does anyone know of ways to eliminate the problem? We've had the walls repainted with "anit-mold" paint. But that didn't really seem to help. I suppose another way way would be to add some insulation. Any suggestions on companies who do that sort of thing?

Thanks.
- Eric S.

johnnyone

You need to ensure the property is well ventilated and if necessary put in some form of mechanical ventilation.
If the renters keep all the windows and doors shut this is the likely cause as there is no escape especially if using portable gas heaters in the winter as they produce copious amounts of water.

bobd22

As Johnny says ventilation is the answer. When we first left our house a friend checked and phoned me to say the whole staircase had turned black with mold. It is a typical Spanish village house. I put a vent in upstairs and always leave a window secure but very slightly open on lower floor and all room doors open. This gives good air circulation and in past 7 years never had the problem again.

Eric S

Yes, they are probably keeping all the windows shut. Is there some kind of automatic ventilation we can install, or just tell them to open the windows once in a while?

I wonder about ventilation, though. If there's a lot of humidity outside, as well as inside, would ventilating really help?

Thanks.
- Eric S.

snikpoh

We have a piso that is partially underground. We put in false walls to help insulate and we also put in a good ventilation system (fan in one corner and vents in the others). This was on a timer coming on every hour throughout the day. For obvious reasons, we don't run the fan at night.

This has solved our problem even with Spanish tenants who don't seem to like daylight nor fresh air!

Dxf

Hola

My solution was to buy two dehumidifiers which I run 24X7 from October through April - all the time I need to heat the house

Davexf

Bo S

You know what its like. The room is nice and warm when you go to bed at night then when you wake up in the morning the windows are all condensation.

If the windows can be left slightly open overnight then you will see a big improvement then opened further well rising. The tenants need to be educated and aware that it is their action that is causing the situation. So their co- operation will help remedy the issue for both parties.

currentaffairs

I wouldn't say that the actions of the tenants are causing the situation... Are you really going to leave windows open if the house or flat is frozen cold?? I like the idea of vents and dehumidifiers as others have suggested. This, of course, is relying on the actions of the owner to help remedy the situation.

There are certainly things that the tenants can do to help things along, but overall I think the whole situation needs to be properly looked at by the owner first and foremost.

Bo S

If the property was empty there would be no issue so it can only be the actions of the tenants causing the issue. Anyway, leaving vents open will still let cold air in so leaving windows slightly open will just do the same job. Not much fun sharing your property with several dehumidifiers whirring away 24/7.

Eric S

Thanks all for your suggestions. We do have one dehumidifier there. Maybe we'll get another one. And we'll try to get the tenants to open the windows.

I'll also look into some kind ventilation system. Although I'm not sure how that would work. I'm not sure I want to make holes in the brick walls for the vents.

- Eric S.

Mark604

I've always wondered of these work -

Products

Maur-Ross

Has anybody tried these poducts. How easy to mount and what conditions would they need?

rspltd

Two immediate things spring to mind. They 'collect' air from the outside which is then driven into the inside by the sun. So presumably, since the sun is shining, they are putting more warm air into a room that is already warm??? Secondly it is usually in winter that the problems occur and since it is less likely for there to be sun, then the system won't work. Anyway the 'vent ' is shown at a high level and since warm air rises is it not likely that any warm air in the room will be expelled firstly rather than the cold damp air that is causing the problem???

Dxf

Hola

As I understand about such systems, you take air from low down in the room, put it through the heater where it rises as it is heated and returns to the room at ceiling level.

There are several home made sytems with videos; how efffective they are remains to be seen.

Davexf

Eric S

That looks interesting, but I don't think it would work for us. Ours is an apartment. I don't think we'd be able to mount anything on the side of the building. Even so, I'm not sure if we'd get enough direct sunlight, due to other buildings around us.

We've contacted these guys: Empresa de humedades. Let's see what they have to say.

- Eric S.