Damp and mould in our home

Doozergirl

You need trickle vents.  It's constant background ventilation that you need with mechanical extraction when you specifically create steam.  Periodically smashing the house with freezing cold air by opening the windows just cools the house from the inside as well as the outside and drops the temperature towards the dew point.  It might change the air briefly but it keeps the walls cold - you shut the windows and the house is sealed up again with cold walls.  

Trickle vents in your windows need to be open (or installed!)

Any old fireplaces need to be either opened up or adequately ventilated.

Decent extractors are needed in the bathroom - humidity sensing ones are best as they turn on automatically and only turn off when the humidity has dropped sufficiently.  

  

Always use your cooker hood and ensure that it is extracting to outside, not recirculating. 

This list is what building control requires for any new property and if the house is kept warm, it should be perfectly adequate because the walls are also insulated.    Drying clothes indoors can be an additional pressure, but those are the basics.    Which of those aren't taking place?  

I would definitely query whether your house is adequately insulated, or if it genuinely is and it hasn't slumped in the cavity, then you really aren't heating the house adequately as cold walls are usually needed for condensation to be a problem, but the first thing to sort is proper ventilation.  

theoretica

LunaD said:

theoretica said:

Do you have a hygrometer to measure and record relative humidity and temperature?  It would be useful information to let you know what you are dealing with, and help measure success of any changes.  It would, for instance, help work out if the air is damper upstairs or just condensing more because the walls are cooler.  And they aren't expensive.

No I don’t have one of those. Our dehumidifier tells us the humidity % on the electric panel and the temperature ? Not sure if that’s the same thing. 

It is the same measurements, but one that records the readings or talks to your phone would easily let you see how the readings varied over day and night and small is more convenient to have in different rooms.

coffeehound

LunaD said:

We keep windows closed at night and open slightly during the day until the afternoon then they’re closed. I am putting the heating on more now to see if it helps.

The trouble with constant trickle ventilation is that (in my experience) the interior is always quite chilly.  If the walls etc are always cold, then they will attract condensation.  If the air is always cold then it cannot hold moisture and will therefore deposit it on cold surfaces.  If you try to heat the home at the same time, then it will use a lot of energy, so it's a kind of losing situation.  

By contrast, if the home is sealed most of the time and just ventilated as necessary, the fabric of the building has a chance to warm up, which will avoid condensation.  The air will be warmer and able to hold much more water vapour, and can therefore absorb moisture from all the various sources.  The central heating can run more efficiently without heat being lost straight out of the windows.

If you have a condensing boiler, then reducing the floww temperature dial down to about one-third of maximum will ensure that it runs efficiently.  It might then need to be run for longer, but it should still work out cheaper.  However if you have a hot water tank, this method won't heat it up enough unfortunately, though you might be able to work around that.

coffeehound

Doozergirl said:
Periodically smashing the house with freezing cold air by opening the windows just cools the house from the inside as well as the outside and drops the temperature towards the dew point.  It might change the air briefly but it keeps the walls cold - you shut the windows and the house is sealed up again with cold walls.  

Oops I just directly disagreed with you  I would disagree completely with this point:  a quick air change does so without giving the walls time to cool down.  Air heats up quickly and easily due to low heat capacity so is no great loss.  

However even a small amount of trickle ventilation can drag down the indoor temperature by a lot, especially in windy conditions.

FreeBear

Doozergirl said: I would definitely query whether your house is adequately insulated, or if it genuinely is and it hasn't slumped in the cavity, then you really aren't heating the house adequately as cold walls are usually needed for condensation to be a problem,

It would be worth getting hold of a thermal imaging camera and going round to see if there are any cold spots - Octopus (the energy supplier) loan them out to their customers, but are restricting to those in financial hardship at present. Might be worth checking with your local council as some may have one available. Get those cold spots checked out and deal with them where appropriate.

A damp wall is a cold wall which attracts condensation, leading to further damp. A vicious circle.

Doozergirl

coffeehound said:

LunaD said:

We keep windows closed at night and open slightly during the day until the afternoon then they’re closed. I am putting the heating on more now to see if it helps.

The trouble with constant trickle ventilation is that (in my experience) the interior is always quite chilly.  If the walls etc are always cold, then they will attract condensation.  If the air is always cold then it cannot hold moisture and will therefore deposit it on cold surfaces.  If you try to heat the home at the same time, then it will use a lot of energy, so it's a kind of losing situation.  

By contrast, if the home is sealed most of the time and just ventilated as necessary, the fabric of the building has a chance to warm up, which will avoid condensation.  The air will be warmer and able to hold much more water vapour, and can therefore absorb moisture from all the various sources.  The central heating can run more efficiently without heat being lost straight out of the windows.

You're wrong.   Trickle vents trickle, and you NEED consistent air changes in a house,  not to trap it, which is why opening windows does not work.   We're not supposed to live in sealed boxes.   Old houses breathe constantly through their numerous draughts, newer or refurbished houses need constant background ventilation.  

You don't lose huge amounts of heat through trickle vents, certainly not enough for the house to ever feel cold, which is exactly what happens when you open a window.   

I have mechanical ventilation with heat recovery in our house which is the gold standard, but the minimum standard for building control is the list I wrote in my previous post.  New houses don't have condensation issues precisely because they have the items I've listed.  They don't need to open windows to not have a house full of mould.  

If I turned my MVHR off right now, the humidity level would rise very quickly and I would have condensation on my incoming water pipe - the only uninsulated thing in the house, within a very short period of time.  Opening the windows wouldn't relieve it.  

LunaD

Doozergirl said:

You need trickle vents.  It's constant background ventilation that you need with mechanical extraction when you specifically create steam.  Periodically smashing the house with freezing cold air by opening the windows just cools the house from the inside as well as the outside and drops the temperature towards the dew point.  It might change the air briefly but it keeps the walls cold - you shut the windows and the house is sealed up again with cold walls.  

Trickle vents in your windows need to be open (or installed!)

Any old fireplaces need to be either opened up or adequately ventilated.

Decent extractors are needed in the bathroom - humidity sensing ones are best as they turn on automatically and only turn off when the humidity has dropped sufficiently.  

  

Always use your cooker hood and ensure that it is extracting to outside, not recirculating. 

This list is what building control requires for any new property and if the house is kept warm, it should be perfectly adequate because the walls are also insulated.    Drying clothes indoors can be an additional pressure, but those are the basics.    Which of those aren't taking place?  

I would definitely query whether your house is adequately insulated, or if it genuinely is and it hasn't slumped in the cavity, then you really aren't heating the house adequately as cold walls are usually needed for condensation to be a problem, but the first thing to sort is proper ventilation.  

Thank you for your great advice. I’ll be showing this to my husband tonight.

Our house is so hot in the spring and summer due to the insulation we had fitted. It boils is even if it’s only 15c outside. In the winter the outer walls so feel colder compared to inside walls, is this not normal?

We are getting a dehumidifier for upstairs as we’ve one we use mostly downstairs. We find that helpful. 

What can I use on the walls to stop the black mould, just basic damp mould paint? It’s so frustrating that every late autumn/ winter this happens. 

LunaD

coffeehound said:

LunaD said:

We keep windows closed at night and open slightly during the day until the afternoon then they’re closed. I am putting the heating on more now to see if it helps.

The trouble with constant trickle ventilation is that (in my experience) the interior is always quite chilly.  If the walls etc are always cold, then they will attract condensation.  If the air is always cold then it cannot hold moisture and will therefore deposit it on cold surfaces.  If you try to heat the home at the same time, then it will use a lot of energy, so it's a kind of losing situation.  

By contrast, if the home is sealed most of the time and just ventilated as necessary, the fabric of the building has a chance to warm up, which will avoid condensation.  The air will be warmer and able to hold much more water vapour, and can therefore absorb moisture from all the various sources.  The central heating can run more efficiently without heat being lost straight out of the windows.

If you have a condensing boiler, then reducing the floww temperature dial down to about one-third of maximum will ensure that it runs efficiently.  It might then need to be run for longer, but it should still work out cheaper.  However if you have a hot water tank, this method won't heat it up enough unfortunately, though you might be able to work around that.

Thank you. So is the answer to keep windows closed all the time? No ventilation? 

LunaD

Doozergirl said:

coffeehound said:

LunaD said:

We keep windows closed at night and open slightly during the day until the afternoon then they’re closed. I am putting the heating on more now to see if it helps.

The trouble with constant trickle ventilation is that (in my experience) the interior is always quite chilly.  If the walls etc are always cold, then they will attract condensation.  If the air is always cold then it cannot hold moisture and will therefore deposit it on cold surfaces.  If you try to heat the home at the same time, then it will use a lot of energy, so it's a kind of losing situation.  

By contrast, if the home is sealed most of the time and just ventilated as necessary, the fabric of the building has a chance to warm up, which will avoid condensation.  The air will be warmer and able to hold much more water vapour, and can therefore absorb moisture from all the various sources.  The central heating can run more efficiently without heat being lost straight out of the windows.

You're wrong.   Trickle vents trickle, and you NEED consistent air changes in a house,  not to trap it, which is why opening windows does not work.   We're not supposed to live in sealed boxes.   Old houses breathe constantly through their numerous draughts, newer or refurbished houses need constant background ventilation.  

You don't lose huge amounts of heat through trickle vents, certainly not enough for the house to ever feel cold, which is exactly what happens when you open a window.   

I have mechanical ventilation with heat recovery in our house which is the gold standard, but the minimum standard for building control is the list I wrote in my previous post.  New houses don't have condensation issues precisely because they have the items I've listed.  They don't need to open windows to not have a house full of mould.  

If I turned my MVHR off right now, the humidity level would rise very quickly and I would have condensation on my incoming water pipe - the only uninsulated thing in the house, within a very short period of time.  Opening the windows wouldn't relieve it.  

Can I ask what is the mechanical ventilation you have in your house? 

LunaD

FreeBear said:

Doozergirl said: I would definitely query whether your house is adequately insulated, or if it genuinely is and it hasn't slumped in the cavity, then you really aren't heating the house adequately as cold walls are usually needed for condensation to be a problem,

It would be worth getting hold of a thermal imaging camera and going round to see if there are any cold spots - Octopus (the energy supplier) loan them out to their customers, but are restricting to those in financial hardship at present. Might be worth checking with your local council as some may have one available. Get those cold spots checked out and deal with them where appropriate.

A damp wall is a cold wall which attracts condensation, leading to further damp. A vicious circle.

Thank you. I’m with OctopusEnergy I’ll look into that. What will it show needs doing if it detects an issue?

so if an outside wall feels cold it’s damp? What could be causing that as all pjs outside walls feel cold in our bedrooms?