High humidity; what are we missing?

[Chefwifelife]

We live in stone cottage built in 1903. We have removed all the awful render off the main building and had it re-pointed which has stopped condensation on our bedroom window reveals.

We have also had a PIV system fitted which filters in clean air and pulls out stale air.

We have recently decorated and moved our toddler into the spare room. This is an extension which is about 10 years old. Assuming breeze blocks with render on the outside. We have had a new loft hatch fitted and checked all the insulation in the small loft space and that there are no leaks in the roof.

The window is triple glazed. There is enough space under the door for the PIV system to work properly.

After 2 nights of our son being in there the humidity is up to 87%. The only other thing I can think of is having trickle vents fitted retrospectively in the window.

Does anyone else have any further suggestions or similar experiences?

Thanks in advance.

Is the floor concrete?

Are there any pipes or drains inside the room, in the walls, under the floor, or on the outside?

How is the room ventilated?

Are there boards in the loft space squashing the insulation?

The floor is floorboards with ply on top and then carpet.

There is a new radiator in there which is switched off. No other pipes that I’m aware of.

@PigletJohn I’m wondering whether there isn’t really any ventilation when the door is shut. Do you think a trickle vent could help?

If we were to get someone in I’m not sure what trade- should we expect air to be able to flow up into the loft space? But assuming most rooms don’t even have a loft space.

I’m stumped at what to do.

if you have PV, it can only ventilate the room if the stale air is pshed out. For today, open a window.

I'd expect trickles to help, or you can have a sort of airbrick ventilator with sound-deadening built in.

I grew up in a cottage like this, and we (and all neighbours) run a dehumidifer about 24/7. It just seems to be the nature of thick granite walls in old builds, often with solid concrete floors. I think painting them with emulsion rather than lime didn’t help as it stopped the walls “breathing”, but the end result is dehumidiers (at least whilst awake).

Gah, pressed send too soon - meant to add
And a positive pressure unit.

as you have a boarded floor, look outside to see if there are plenty of airbricks to ventilate the void. Hold a joss-stick or fag against them to confirm airflow.

the ground or concrete under the house will generally be damp so the airbricks ventilate the water vapour out.

PIV is something different

@PigletJohn

PIV is something different

@PigletJohn... ok I have been waiting all day for someone else to comment on that. But is PIV a building term? Because when i read it on mumsnet it definitely isn't used in the building term sense!

I have no idea what it means.

but I gather it steams up the bedroom windows.

@RubaiyatOfAnyone the thing is the extension is new and not made of stone at all 🤔 when we ran a small dehumidifier in there it strangely didn’t collect any water!

@NachoNachoMan we jokingly refer to what you are taking about. It stands for positive input ventilation