Passive vent to loft

claudio_1987

Hello all, i have small room that one of my kids sleeps in due its size and location humidity level rise to 80% in there when door and windows closed , in warmer months opening the windows is ok winter is the issue and to keep moisture down would adding a passive vent to loft( have plenty of air circulation ) would that be a good idea?

ThisIsWeird

Warm, moist air getting up to the loft space? Not usually considered a good idea as it can cause damage up there are it condenses out in the colder temp - if not fully ventilated away.

There's also a good chance that, depending on the wind direction, you'll be having a draught coming down from the loft at times.

What is the cause of the high humidity level? What are the indicators - condensation on the window panes? Mould in the corners?

You try and tackle the root cause(s) as much as possible, even if it means lining the insides of the external walls with insulation - fairly disruptive, but should be transformative.

After trying to tackle the source, the best way to remove humidity and condensation is to ventilate, even in winter - leave the windows cracked open to ventilation setting overnight. Yes, that will mean a chilly room, but that's why you have high-tog duvets.

Time the heating to come on at whatever time is required in the morn to take the chill off the air, and your child can jump out of bed and fully close the window. Continue to ventilate that room at all other times, with the heating off.

Before bed, have the heating on for a half-hour before retirement and close the window. Just before jumping into bed, heating off, and window open again.

Mistral001

I agree.  It is not a good idea for the reasons given above.  All rooms should have some ventilation.  If the windows have trickle ventilators then open them in winter.  That is what they are there for.  If there are no trickle ventilators open the window very very slightly.  Even if they are open just a few mm it will give enough ventilation.   Alternatively install a vent in an outside wall at high level.  Note if the window does not have a opening at high level but has only one which opens sideways the whole way from top to bottom, that might cause draugths at the bed level, so a high level wall vent might be your best option.

PS you will probably have to have some slight background heat in the bedroom on cold nights. 

Mistral001

Just a thought.  Why not keep the door open?  That would be the simplest solution.

ThisIsWeird

Mistral001 said:

Just a thought.  Why not keep the door open?  That would be the simplest solution.

An open door can exacerbate the problem if the humidity is coming from the warmer house.

Personally, I love the feel of a cold draught on my nose, espec when snugged up under a decent duvet, and wifie has gone to bed at least a half hour before me

There is actually no reason at all for anyone to be too cold at night. If really needed, an overnight leccy blanket will be pennies to run. Just make sure they aren't abused - on the lowest setting, and only if really needed.

I have ours on a digi plug-in timer during coldest winter times, set to come on (and go off) at 'lowest' an hour before bed - just enough to remove the chill, and never on all night.

grumbler

It's worth considering a heat recovery wall fan, but they aren't cheap and require drilling 100-150mm hole in an external wall. I think similar fans are available for a loft - with venting through eaves or roof - is it what's called Positive Input Ventilation?

BUFF

PIV takes (usually colder  as most have a "cold" loft https://kishorninsulations.co.uk/news/what-is-the-difference-between-a-warm-loft-and-a-cold-loft) air from loft & pushes it down into the house.
https://www.homebuilding.co.uk/advice/positive-input-ventilation

claudio_1987

Hello all, thank you for the input from everyone 

For the reason of the moisture be so high is mainly due my daughter sleep in and she hates keep the door open , the window is always slightly open but for some reason on corner and near her bed length can see condensation is almost wet to touch , this the coldest part of the house and the smallest room as well, i ensure no mold was on wall , and treated the walls with new primer and mold resistant paint ,installed and moisture and temperature thermometer i check her room every day and during the day moisture is on high 60s ( no problem here)  when she is asleep i check her before going top work is on mid 80s percent of humidity , this in terraced house and no broken roof tiles , been on loft no moisture at all up there on corner of the roof 

Ramouth

PIV to the hallway, trickle vents in your daughters room and a 5 - 10 mm gap under her door (achieved by planing the bottom of the door) would create a flow of fresh, dry air through the room.  Even with good insulation heat is going into the loft from the house so The air will feel less draughty than an open window, and mixing it with the air in the hallway will further temper it.  This should help with air quality in the whole house as well as mould in your daughters room.

CSI_Yorkshire

Ramouth said:

PIV to the hallway, trickle vents in your daughters room and a 5 - 10 m gap under her door (achieved by planing the bottom of the door) would create a flow of fresh, dry air through the room.  Even with good insulation heat is going into the loft from the house so The air will feel less draughty than an open window, and mixing it with the air in the hallway will further temper it.  This should help with air quality in the whole house as well as mould in your daughters room.

I'm hoping that was "mm" unless you're suggesting some excavation.

Ramouth

CSI_Yorkshire said:

Ramouth said:

PIV to the hallway, trickle vents in your daughters room and a 5 - 10 m gap under her door (achieved by planing the bottom of the door) would create a flow of fresh, dry air through the room.  Even with good insulation heat is going into the loft from the house so The air will feel less draughty than an open window, and mixing it with the air in the hallway will further temper it.  This should help with air quality in the whole house as well as mould in your daughters room.

I'm hoping that was "mm" unless you're suggesting some excavation.

😂 yes I meant mm - I’m just rubbish at typing!