Difficult situation with ventilation and damp

mondeoman72 · 26-09-2024 9:36am #1

Apologies but hoping someone may have an idea on this as it's an impossible situation for me.

A bungalow on a hillside. Oil fired central heating. Old single glazed wooden framed windows. No airvents in rooms. Get the idea?

Old lady living there always cold. She goes around in the mornings with a window vac and dries all the condensation from interior of windows.

Black mould recently found and cleaned. Purchased lots of dehumidifier tubs that soak up moisture. They are filling up each month but not ideal. Ideally air vents need to be put in but she would freak due to feeling the cold

Anybody got any suggestions on how to reduce / eliminate the moisture.

Thanks everyone.

10-10-20 · 26-09-2024 10:42am

Apart from the obvious to move to double pane windows and also increase the average temperature of the house - Invest in a dehumidifier with a drain function and leave it on in the most used room at a target point of 50% RH, and leave the bedroom doors open to assist ventilation. Also encourage her to use a dryer on clothes rather than drying indoors.

Those salt tubs might take out a few tens of mills, but if you do the maths on absolute humidity in this example:

Take a 100m2 house with a wall height of 2.4m, so that's 240 cubic meters (m3) in total. It's at a temperature of 20c (standard pressure, etc) and a high relative humidity of 70%. With these values you effectively have 12.7ml of water per cubic meter (m3), which would be a total of 3048ml or 3L of water.

To get this house down from 70% RH to 50% RH (which is 8.65ml per cubic meter) you would need to remove 972ml of water, and keep repeating that as the house draws in more moisture or gains it through cooking/drying/etc. So now you see why the salt tubs are useless.

10-10-20 · 26-09-2024 10:43am

And if you do decide on a dehumidifier then go for a desiccant based one as they operate better in the Irish climate.

Calahonda52 · 26-09-2024 11:04am

You could consider secondary glazing on the big panes.

AS above re the RH math, as its a bungalow a small heat recovery unit in the attic… would need to be carefully calibrated to a very slight positive differential. I did one years ago, can recall the make, it was neat

How much insulation in attic?

hummus_chips · 02-10-2024 8:03pm

Hello, is this thread still looking for responses? So many things I could say :) Dehumidifier very cost effective, we have MHRV system and I am so impressed with it from a humidity point of view, but the main Q here is how much money is available here to do something? Air vents won't necessarily help (at all really), as you're not actively 'moving damper air out of the house and replacing with less damp external air'. Is the bungalow surrounded by trees/shrubbery/not getting much light? Are the curtains closed all day? Is the bungalow cavity block build? Is it exposed or sheltered from prevailing winds?

What's the state of the attic?

My top thoughts would be 1) insulate attic with loft wool, 300mm, do it right. IMPORTANT Use loft trays to allow the attic to breathe:

https://store.sig.ie/products/roofing/eaves-ventilation/klober-loft-vent-tray/

2) seal the wall plates in the attic, google it, basically get some airtight tape and seal any holes at the top of stud walls, anything that allows a draught pass from the ceiling or stud walls into the attic. E.g the holes drilled into the wall plate (top) for electrical wiring, water pipes.

3) Dehumidifiers, prob 2. Leave doors in rooms open across the house. Leave one during the day and two at night time rates if cost is an issue

4) re-seal window/door openings, kill off draughts (this is for heat retention, not humidity.

5) if you can, peel back carpets to subfloor, and airtight tape any holes such as where radiator pipes come through, to minimise drafts

.. I could go on but that should get you started.

Make sure boiler is serviced, make sure there is lagging on pipes from boiler into main house, both directions. Make sure thermostat working well. Block the Chimney with a chimney pillow, no more fires.

I really could go on an on :)