How to address my humidity issues

WIAWSNB

Aloysius1972 said:

WIAWSNB said:

So, a PIV is effectively a whole-house open window

To an extent, yes. PIV is not extracting any moisture and relies on exterior air being fresher than interior air and less moist for the most part. But, as I understand it, the main difference is that it introduces that air actively so will ‘drive out’ damp interior air to some extent and create fresh air flow which is thought to be helpful vis-a-vis condensation irrespective of humidity level. So it will not do a huge amount to reduce average humidity across the house but it will equalise the levels across the environment to avoid the spiking in cold spots that results in problems. By contrast, windows are a passive approach which are reliant on the balance of the interior and exterior air to introduce changes to the air quality. So helpful to an extent but less reliable overall. At least as far as I understand it…

PIV and an open window both introduce the 'fresher air' from outside.
There is no practical difference in terms of ventilating away moisture, other that the PIV is at a constant - tho' lower - level.
Have you tried my other test yet? Taking the stack outside...

Aloysius1972

That’s the area where the mould was (green spots which I dusted off) rather than a picture of the mould itself. But, yes, the cause for it might be due to the plaster being just a few weeks old. It’s not damp but is a few degrees colder in that spot (measured) than the rest of the plaster, on the other hand, the stack in the other room has the same cold spots and isn’t mouldy despite being window closed/door open. We’ll see.

WIAWSNB

Aloysius1972 said:

That’s the area where the mould was (green spots which I dusted off) rather than a picture of the mould itself. But, yes, the cause for it might be due to the plaster being just a few weeks old. It’s not damp but is a few degrees colder in that spot (measured) than the rest of the plaster, on the other hand, the stack in the other room has the same cold spots and isn’t mouldy despite being window closed/door open. We’ll see.

I wouldn't have expected condensation-mould to have formed there as opposed to other, more obvious, areas such as internal corners, top and bottom. Hence my suspicion. 

ComicGeek

Fresh plaster releases so much moisture as it's drying. You really need the heating on in those rooms - at the moment the outside air is too humid to adequate dry a room, let alone drying the plaster as well. PIV systems also struggle at this time of year.

Put the heating on in the rooms, open the window slightly and leave the door to the hallway open. You are creating so many problems by not heating the rooms at the moment, it doesn't make sense.

WIAWSNB

Nah - just open the windows fully :-)
Doing so will ventilate that excess moisture to the outside.
If you heat that room without ventilating it away outside, that increased level of warm moist air is just going to seek out other cold places in your house to condense out on.
The wider you open the window(s), the better. Internal door shut.
Yes, in this cold weather the plaster will take longer to dry, but ventilate ventilate vent...

twopenny

Was the stack allowed to fully dry off after striping the old off and before it was plastered?

You did strip the old plaster off?

Aloysius1972

twopenny said:

Was the stack allowed to fully dry off after striping the old off and before it was plastered?

You did strip the old plaster off?

Good point and and answer would be no. The single job over 5 days stripped the old plaster back to brick and boarded over a membrane. The old plaster was contaminated from previous water ingress.

Aloysius1972

I see the heat vs ventilation debate still rages! In the end condensation control is surely a balance of temperature (air and surface) control, humidity extraction, ventilation and circulation? Can it really be controlled by one of those in isolation?

Aloysius1972

Looking at my moisture creation, I am realising that the main culprit is probably my partner’s addiction to our heated airer, drying about 4 or 5 loads of washing per week in a largely unventilated room. That seems to create more moisture than our cooking and bathing combined. 

So I am wondering if I should get a tumble dryer instead. The price of the heat pump models seems to have dropped since I last looked 2/3 years ago and would probably pay for itself vs our heated airer across no more than 4 years based on a saving of about 40-50p per load. That is leaving out of the equation the extra cost from addressing condensation consequences or having to heat more due to opening the window in that room to exit the moisture created.

is that logic sound?

shiraz99

Aloysius1972 said:

Looking at my moisture creation, I am realising that the main culprit is probably my partner’s addiction to our heated airer, drying about 4 or 5 loads of washing per week in a largely unventilated room. That seems to create more moisture than our cooking and bathing combined. 

So I am wondering if I should get a tumble dryer instead. The price of the heat pump models seems to have dropped since I last looked 2/3 years ago and would probably pay for itself vs our heated airer across no more than 4 years based on a saving of about 40-50p per load. That is leaving out of the equation the extra cost from addressing condensation consequences or having to heat more due to opening the window in that room to exit the moisture created.

is that logic sound?

Yes, get a heat pump tumble dryer if you can afford one. Those heated airers aren't that great and put a lot of moisture back in the room so I'd only use them in tandem with a dehumidifier. Also, tests have shown that using a standard, non heated airer along with a dehumidifier and desk fan will dry the clothes a lot quicker than a heated airer alone and for not much more money.