Improving living conditions in my mum's damp and humid small bungalow

[minty]

My mum wants me to add a layer of insulation around the outside walls of her small bungalow and clad over it to improve her damp and unhealthy living conditions inside. However I want to understand the problem and make sure her idea is the solution.
The existing external cladding is wood with a breathable paint. Inside that is a 20mm layer of fibreglass wool packed tightly against a 30mm layer of polystyrene which is lined with a plastic non breathable sheet. The Internal cladding is wood and there is no air gap between any of these layers. These layers appear dry when I exposed a small area.
The roof is the same with thick bitumous felt on the outside which seems to be sound.
The floor is elevated off the ground with good ventilation underneath but there is no insulation - just a plastic sheet and a layer of underlay under the lino floor.
Inside she has double glazed windows with no vents in the frames. She has one air vent in the wall which is open and an extractor fan in the bathroom not the kitchen.
Her humidity inside is regularly in the 90s, heating is provided by plug in electrical heaters- it's a small space. Basically a cabin. She lives with her dog.
The walls are mouldy and even the curtains and her clothes but there are no signs of leaks.
Even though she keeps a window open most of the time and her dehumidifier running; the high humidity presumably comes from the dog, cooking, etc etc and the plastic sheet inside the walls and lack of ventilation in the window frames prevents it escaping so condenses on the colder walls and floor where the insulation is insufficient- have I got this right?
Is it possible the felt roof let's in moisture even though it's not actually leaking?
If so then an extractor fan in the kitchen and one in the living space is needed plus floor insulation and a bit more roof and wall insulation.
Am I right so far?
If so then my next question is about installing the insulation and whether to start again by ripping down the existing external cladding and replacing the polystyrene OR rip out the internal cladding OR my mum's idea which leave everything as it is and at another layer on top.
If you got this far please comment!
Thank you

[SteamyTea]

What temperature does your mother keep her place at?

 

The relationship between temperature, humidity and mould growth is not linear.

 

Adding external insulation will help in using less energy to keep the temperature higher than the outside air temperature, but in itself, does not change the amount of water vapour in the internal air.  To change that you need to ventilate.

You can get single room mechanical ventilation and heat recovery units (dMVHR) and it may be worth fitting one of these before you try anything else.

 

While you think there may not be any water leaks, you may need to investigate this more i.e. waste water pipes, clothes drying, ground height.

[Andehh]

I would also look at PIV systems, positive air pressure being drawn in from the loft, which is dryer/cooler, which forces out the damp air in the house. Make a big difference quite quickly.

[SteamyTea]

18 minutes ago, Andehh said:

positive air pressure being drawn in from the loft, which is dryer/cooler,

Except when it is hotter and higher humidity.

 

[markc]

Ventilation, ventilation, ventilation, stick a living, breathing, cooking person inside a box wrapped with plastic and you are going to get damp and mould.

[Redbeard]

Agree with ST's dMVHR suggestion, but if you want to go a bit cheaper and forego the HR, decentralised mechanical extract ventilation (dMEV) may be an idea. Some have spoken of it highly on here and I have 3 Greenwood Unity CV2 units waiting to go in.

[joe90]

1 hour ago, markc said:

Ventilation, ventilation, ventilation, stick a living, breathing, cooking person inside a box wrapped with plastic and you are going to get damp and mould.

This is oh so true.

[minty]

On 09/04/2024 at 07:21, SteamyTea said:

What temperature does your mother keep her place at?

 

The relationship between temperature, humidity and mould growth is not linear.

 

Adding external insulation will help in using less energy to keep the temperature higher than the outside air temperature, but in itself, does not change the amount of water vapour in the internal air.  To change that you need to ventilate.

You can get single room mechanical ventilation and heat recovery units (dMVHR) and it may be worth fitting one of these before you try anything else.

 

While you think there may not be any water leaks, you may need to investigate this more i.e. waste water pipes, clothes drying, ground height.

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.

Edited April 10 by minty

[minty]

On 09/04/2024 at 09:06, Redbeard said:

Agree with ST's dMVHR suggestion, but if you want to go a bit cheaper and forego the HR, decentralised mechanical extract ventilation (dMEV) may be an idea. Some have spoken of it highly on here and I have 3 Greenwood Unity CV2 units waiting to go in.

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?

[minty]

On 09/04/2024 at 07:54, markc said:

Ventilation, ventilation, ventilation, stick a living, breathing, cooking person inside a box wrapped with plastic and you are going to get damp and mould.

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??

[minty]

On 09/04/2024 at 07:32, Andehh said:

I would also look at PIV systems, positive air pressure being drawn in from the loft, which is dryer/cooler, which forces out the damp air in the house. Make a big difference quite quickly.

PIV meaning?

There isn't a loft. 

[Redbeard]

ST = Buildhub member @SteamyTea

dMVHR. Decentralised mechanical ventilation with heat recovery. Decentralised because he's not talking about 'full monty' MVHR systems which have a central heat exchange unit.

dMEV (decentralised mechanical extract ventilation) involves using specifically-designed fans in wet areas (bathrooms and kitchens) which run permanently at very low wattage (perhaps less than 2 Watts). They also have an over-ride (pull-cord or - my preference - humidistat) which kicks the fan in when things get too steamy. They rely on having open vents (often 'trickle vents in the window frames) in all the 'dry' rooms, so that the extract from the wet rooms causes supply air (from outside and usually more dry) to flow in. It's very simple with no complicated 'control interfaces. CV2 is simply the model number of the 'Greenwood (manufacturer) Unity dMEV fans I have bought. 

 

[Redbeard]

PIV = Positive Input Ventilation, as described by Andehh

[Crofter]

6 minutes ago, minty said:

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??

Plastic should be installed on the warm side of any insulation, to prevent moist air from entering the insulation and condensing as it reaches the cooler outside layers. Especially important in timber frame buildings, but it's always good to keep your insulation dry.

[Redbeard]

19 minutes ago, minty said:

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???

 

The plastic is a Vapour control layer (VCL) which is designed to stop 'interstitial condensation (water vapour condensing out in the insulated wall 'sandwich). Unless you are planning to change completely the 'moisture behaviour' of your Mum's house no, you do not necessarily need to remove it, but if you are adding more insulation internally you might, as you would then install a VCL on the 'warm side' (just behind the plasterboard) of that new insulation.

 

Edit: Was typing while @Crofter typed.

Edited April 10 by Redbeard

[SteamyTea]

Not read all the recent replies, but the members who have replied give sound advice (usually).

 

You could look into fitting an Air to Air Heat Pump (A2AHP).

That was it will be cheaper to heat the place, then ventilate the bollocks out the place, with or without heating recovery.

 

There are a number of different A2AHPs. Some are cheap, others are expensive, and some are fitted inside only with a couple of holes drilled through the walls.

Quite a few people on here have fitted them, and one member has one fitted in his static caravan.

 

The VLC, (vapour control layer) in the UK climate is fitted on the inside, which is why ventilation becomes important.

It is there to protect the building, not the occupants (they should know about ventilation, but many don't, living in an airtight house takes a bit of getting used to).

 

ST also means solar thermal, a technology that is not used much now as PV (photovoltaic) is cheaper and generally more useful.

 

 

I am sure with a bit more detail about your mother's home, we can, collectively, get it warmer, dryer, and cheaper to run.

All without putting the dog in an outside kennel, where it should be.

Edited April 10 by SteamyTea

[Roger440]

As a short term fix, get a couple of de-humidifiers. If you get dessicant ones, they generate a degree of heat too.

 

Eventually, you will get to a sensible number, say 50%. Once there, see how long it takes to start to rise. If its rapid, then you really need to understand why.

 

Several have said ventilate. Thats great, so long as its lower humidity outside than in. To an extent, thats going to depend where it is, but its been pretty much 90% and over here since mid July here (mid wales) apart from a few notable days. Opening the windows to ventilate would make things worse, not better.

 

I suspect, a lack of ventilation management of any sort just sees the humidity climb ever higher.

 

The above is what i did, the house was humid, mainly as not inhabited for 10 years. It took 6 months of running 2 de-humidifiers to get to the point, where it now sits at 50% and requires, maybe a couple of ours a week of one de-humidifier to keep it there.

[SteamyTea]

31 minutes ago, Roger440 said:

Several have said ventilate. Thats great, so long as its lower humidity outside than in.

?

 

 

When it comes to condensation, the absolute humidity (the grams of water in a kg of air) can become important.

[minty]

3 hours ago, SteamyTea said:

Not read all the recent replies, but the members who have replied give sound advice (usually).

 

You could look into fitting an Air to Air Heat Pump (A2AHP).

That was it will be cheaper to heat the place, then ventilate the bollocks out the place, with or without heating recovery.

 

There are a number of different A2AHPs. Some are cheap, others are expensive, and some are fitted inside only with a couple of holes drilled through the walls.

Quite a few people on here have fitted them, and one member has one fitted in his static caravan.

 

The VLC, (vapour control layer) in the UK climate is fitted on the inside, which is why ventilation becomes important.

It is there to protect the building, not the occupants (they should know about ventilation, but many don't, living in an airtight house takes a bit of getting used to).

 

ST also means solar thermal, a technology that is not used much now as PV (photovoltaic) is cheaper and generally more useful.

 

 

I am sure with a bit more detail about your mother's home, we can, collectively, get it warmer, dryer, and cheaper to run.

All without putting the dog in an outside kennel, where it should be.

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.

 

[minty]

1 hour ago, Roger440 said:

As a short term fix, get a couple of de-humidifiers. If you get dessicant ones, they generate a degree of heat too.

 

Eventually, you will get to a sensible number, say 50%. Once there, see how long it takes to start to rise. If its rapid, then you really need to understand why.

 

Several have said ventilate. Thats great, so long as its lower humidity outside than in. To an extent, thats going to depend where it is, but its been pretty much 90% and over here since mid July here (mid wales) apart from a few notable days. Opening the windows to ventilate would make things worse, not better.

 

I suspect, a lack of ventilation management of any sort just sees the humidity climb ever higher.

 

The above is what i did, the house was humid, mainly as not inhabited for 10 years. It took 6 months of running 2 de-humidifiers to get to the point, where it now sits at 50% and requires, maybe a couple of ours a week of one de-humidifier to keep it there.

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

[joe90]

16 minutes ago, minty said:

I like Mums Dog but on principal dog do belong outside.

Don’t listen to @SteamyTea he is allergic to cats and dogs, I have a dog indoors (and have done fir may years) with no humidity problems. 
 

 

18 minutes ago, minty said:

A2A heating could be good. Is that the same as an air source heat pump.

No, and ASHP produces hot/warm water for use in underfloor heating or radiators, and an air to air heat pump produces warm air (like a fan heater) to blow into the house/room, they also can blow cool air like an  air conditioner.

[Roger440]

1 hour ago, SteamyTea said:

?

 

 

When it comes to condensation, the absolute humidity (the grams of water in a kg of air) can become important.

 

Indeed.

 

But the problem here is simple, so keeping it simple.

[Iceverge]

10 minutes ago, Roger440 said:

 

Indeed.

 

But the problem here is simple, so keeping it simple.

 

 

I think I improved that marginally. 

[Iceverge]

On 09/04/2024 at 07:05, minty said:

Even though she keeps a window open most of the time

 

Probably not enough, 

 

You need 2x windows open to get a decent cross flow. The trouble is then that the house gets cold and they get closed. 

 

On 09/04/2024 at 07:05, minty said:

and her dehumidifier running

 

 

This needs to be on 24/7 a max power. 

 

On 09/04/2024 at 07:05, minty said:

an extractor fan in the bathroom

 

Take this out and replace with one of these. 

 

 

As mentioned above, it runs continuously and ramps up when the humidity does. and sucks out all the damp air. Costs about 1/20th of what a dehumidifier does to run. 

 

[Jilly]

Meaco dehumidifiers are very good.