99% indoor humidity... what to do?

[Harry Bloomfield]

Will see if turning up the heating can reduce some of the humidity meanwhile. Some articles say that it reduces energy cost to turn on the radiators only when you use the rooms, instead of having it on low settings all the time, but I guess that doesn't help keep the house dry in general.

That is generally false economy, especially with gas central heating. If you heat one room, heat will escape to the rest of the house anyway and it will not make it that much cheaper to run, which is where TRV's come in, so you can set individual temperatures in different rooms. Good insulation and good measures to limit moisture generation inside the house, are the key to low running costs/ a warm home free of moulds.

 

[^woody^]

Thanks a lot Woody. I've read some of your other posts on this topic too and they've been very helpful, esp on humidity vs condensation and mould

Will see if turning up the heating can reduce some of the humidity meanwhile. Some articles say that it reduces energy cost to turn on the radiators only when you use the rooms, instead of having it on low settings all the time, but I guess that doesn't help keep the house dry in general.

The key thing is that some houses are better at dealing with condensation issues than others. This can make dealing with it very difficult or it may never be possible without significant adaptation of the structure or just cranking the heating up to crazy temperatures for long times and paying for that.

At my house for instance the family (not me) did everything wrong in terms of using heating, ventilation, drying washing inside etc, and we never had any mould problems. The lucky thing for us is that the house construction and its orientation meant that the building could deal with all that got thrown at it. In a different house we may have been in trouble.

So that's the problem you face. You have to be mindful about the humidity you will make and using the heating appropriately, and ventilation when necessary. It can be a false economy to try and save on the gas bill, but then pay more for all the curtains, clothes and linen you end up throwing away due to mould.

If the house really cant deal with things, then the help can be in terms of a dehumidifier or two, but if that is the situation you end up in, consider a Positive Pressure Input Fan which can help with hard to manage homes. Lots of posts in the forum, also known as Lofty, but there are several suppliers

 

[daisy12345]

The key thing is that some houses are better at dealing with condensation issues than others. This can make dealing with it very difficult or it may never be possible without significant adaptation of the structure or just cranking the heating up to crazy temperatures for long times and paying for that.

At my house for instance the family (not me) did everything wrong in terms of using heating, ventilation, drying washing inside etc, and we never had any mould problems. The lucky thing for us is that the house construction and its orientation meant that the building could deal with all that got thrown at it. In a different house we may have been in trouble.

So that's the problem you face. You have to be mindful about the humidity you will make and using the heating appropriately, and ventilation when necessary. It can be a false economy to try and save on the gas bill, but then pay more for all the curtains, clothes and linen you end up throwing away due to mould.

If the house really cant deal with things, then the help can be in terms of a dehumidifier or two, but if that is the situation you end up in, consider a Positive Pressure Input Fan which can help with hard to manage homes. Lots of posts in the forum, also known as Lofty, but there are several suppliers

Thanks again Woody. We've only been at the house for a few months so still adapting and figuring out how it performs. Fingers crossed so far haven't seen large-scale mould or condensation issues.

I've look up the PIV too, but as our loft has been converted to a bedroom, I guess that's not an option for us?

 

[^woody^]

Thanks again Woody. We've only been at the house for a few months so still adapting and figuring out how it performs. Fingers crossed so far haven't seen large-scale mould or condensation issues.

I've look up the PIV too, but as our loft has been converted to a bedroom, I guess that's not an option for us?

They do others - Flatmaster or similar is designed for err, flats - or houses without lofts!

 

[Rad1o]

When you hit 100% humidity, the air is saturated. This is tropical or after a rain showers. What you experienced in the morning was saturated and cold air rushing in and cooling down the room air. Cold air can hold less moisture than warm air. If you have 80% humidity inside in a small room and cold, saturated air hits it the the inside air volume "shrinks" and the moisture content rises relatively, leading to precipitation - water down the walls.
High moisure content indoors is usually affected by 3 factors. Moisture production, heating and ventilation.
If you only heat your house to 16 °C, the air cannot carry as much moisture as at 20°C and the humidity reading - relative humidity - will be higher.
If you produce a lot of moisure indoors by breathing - the more people the more moisture -, cooking, washing, drying and if your ceiling joists are still soaked from a water pipe leak you have to deal with a lot of moisture.
A study in a continental european country found that "pulsed" ventilation with a window wide open for a short time leads to better ventilation and air exchange than if you use trickle ventilation, which is no good at all for effective air exchange. Trickle ventilation allows more of the heat to escape than it allows air to exchange and this leads to your walls especially around windows to cool down. The walls, ceiling and furniture act as heat sinks and it takes a lot of heating to get the heat sinks up to temperature again., so it is more cost effective to air with windows wide open for a few minutes.
In the long run you want to insulate the walls, extract kitchen and bathroom steam and reduce other moisture sources.