minty

This is perfect, thank you for your post. the info on the fan is particularly useful. I'm more focused now.

Thank you. I understand this post and the way you have described the situation. I like the idea of experiments to make a diagnosis. I will measure the humidity, then reduce it to 50- even if we rent a bigger dehumidifier- then see how long it takes to get back to the original measurement and make a conclusion from there. It would be interesting to repeat this experiment without any dogs or people in the house for a few days and compare results. There is a very small extension added to living space which I have not explored for leaks etc, however I noticed the mould in there is really bad and the nails in the external cladding are rusty on the extension but not on the original chalet building. I will look inside the walls, floor and roof for signs of excessive moisture.

So if I get the humidity down to 50% and Mum and dog go away for a few will it stay at 50% even if outside humidity is higher? Surely the humidity inside depends on the humidity outside . How does she maintain a constant 50%- for example- if humidity outside is 80%?

Hi If I run a dehumidifier constantly until the percentage is reduced to 50 , then get my mum and her dog to move out for a few days and the humidity remains the same then does that prove the high air vapour content is caused by the dog and one person?

So what do we do to make the living conditions healthy and free from damp?

The mouldy damp living conditions are the primary concern. Will this unit solve the problem?

The graph shows that as humidity increases condensation will occur on warmer walls than air with lower humidity which is why there is mould in my mum's house; ventilation and dehumidifiers will reduce the vapour in the air but why is it so high in the first place? How do we find out where it's coming from. Obviously the chalet is wrapped in plastic and there is a dog so is that alone the answer?

Great advice. I look forward to trying this experiment. Thank you

This is positive - thank you. I like Mums Dog but on principal dog do belong outside. I am more than happy to provide a bit more detail to you. Please let me know how I can help you help me get the answer. I understand the principal of the plastic now. I'm still unsure if the insulation needs an air gap on the cold side and whether the lack of one contributes to mums condensation in her living space She has no chimneys and uPVC doors and windows so A2A heating could be good. Is that the same as an air source heat pump.

PIV meaning? There isn't a loft.

Thank you. My mum's space is wrapped in plastic which presumably stops vapour getting out. Why does anyone put the plastic there to start with? There must be a reason. Do I need to take it all out before adding more insulation??? Ventilation can be added using electric fans right? Should insulation have an air gap on the outside? If so why ? And why isn't there a gap now- or is the fibreglass wool layer providing the air gap??

Hi. Thank you for your contribution. I don't know what ST DMNHR DMEV CV2 all means? Do you mean put an electric fan in the living space like the ones that come on automatically in bathrooms?

This is so much appreciated. Thank you. My mum keeps her place warm with a single plug in heater. I've never measured the temperature but probably a bit lower than an average house. The internal air vapour content is what's bothering her predominantly so the ventilation is presumably more important so will find out what a dmvhr is because I have no idea. Extra insulation will save energy but- I assume - also reduce condensation in her living space because the internal walls will be kept above the dew point- have I got this right? Also there are no air gaps at the moment inside the wall- between the external cladding and polystyrene - only a thin layer of fibreglass wool - so does this cause condensation inside the walls and consequently lower the temperature of the internal walls creating condensation in the room also.... Have I got this right? Thank you.