Controlling damp and mould - to vent or not to vent?

[Johnny Allround]

Hi Gste, one way to get the boys on here to debate long and hard is to mention, damp, mould and ventilation. I see your in Lancashire you might want to speak to these people see attached. Hope this helps.

 

[Harry Bloomfield]

The extractor wasn't working when we moved in so I replaced it like-for-like with a 4" Manrose low-voltage unit - does that sound adequate or do you have recommendations for anything better?

Not adequate, it needs to be bigger and its position should be opposite where air can enter, so dry air is drawn through the entire room. You also need to ensure it runs during a shower or bath, plus continues to run for some time after - a PIR plus timer included control would take care of that.

If you don't have any open fires or gas burning appliances, you can brick up all of the vents.

How do you dry washing?

 

[^woody^]

Thankfully the kitchen is unaffected as we have a vented extractor hood and always have the window open when cooking or boiling the kettle.

Room temperature has improved due to the double glazing but the two rooms that are mainly affected - the lounge and bedroom - have heating problems. In the lounge we've blocked the radiator with a huge sofa which can't help and need to rearrange the furniture. The bedroom is very cold due to a single radiator that's too small, we're getting this replaced with a double with a smart TRV to keep the room at a higher temp and hoping this will improve things. We're also repainting and I plan to add both anti-mould and insulating additives to the paint. Where we've painted one wall with this combo it's been unaffected for the past year which is positive...

You might need to modify your thinking a little.

You can't think of the rooms in isolation, but must consider the flat as a whole. You say the kitchen is "unaffected" and has a fan and has the window open, but the kitchen (and bathroom) are a major source of the moisture that ends up on the walls as condensation in the other rooms. Unless you keep all doors shut all the time, and use fans before and after cooking, and everytime you boil the kettle, or run the hot taps, then moisture is going to get out the kitchen and bathrooms to other rooms.

Likewise for cold rooms. A different temperature and humidity in one room will affect other rooms as air moves.

And whilst having double glazing may well make the rooms warmer, it also makes them more air-tight, reduces draughts (ie air movement) and most of all, it does not make any moisture in the air magically disappear. Moisture (excessive moisture) that was there before the double glazing is still going to be their afterwards, and all that hapens is that it finds the next cold surface in the room - which will be the walls.

All the measure you are talking about - increasing heating, smart TRV's, anti-mould paint do nothing for the actual humidity levels and dew points (surface temperatures at which air condenses). And unless you actually deal with the moisture in the air, you need to be careful that you dont just shift the problem around the flat to the next cold surface that the damp air finds.