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do I have damp?


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I was wondering if I can have a bit of advice here.


I bought 6 thermpro hygrometers (simple ones, temperature and humidity only), one in each bedroom, bathroom, living room and extension.


the house is a 1950s ex-council property with brick/brick cavity walls, porous mortar (lime?) and in good condition overall. the house has double glazed windows, which never condensate in between panels, so I trust they're in good condition. there is also cavity insulation in the form of polystyrene beads, they're dry. no damp patches anywhere, no leaks, no musty smell.


however, if the windows are closed, humidity registers just above 60% in more or less every room. the new extension (brick/breeze block, 100mm insulated cavity, triple glazing bifold + skylights) is usually a bit higher, around 65%.


if I open the windows it does go below 50%, does that mean I have a ventilation issue? in the winter, there is condensation on the inside of the windows, mainly after showering, washing, drying, cooking etc.


I'm thinking to invest in a vent axia PIV, would that help?

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only the extension has trickle vents (3 x 40cm above bifolds, always open), the remaining windows don't. in spring/summer/early autumn, we keep the top bit of the windows ajar at all times. in the winter, we ventilate every day, mornings and evenings. I was only asking about damp because I would expect the readings to be much lower, around 45-50% when we're not cooking etc.


60% is on the high side and any activity that produces a lot of damp (boiling water, long, hot showers) increase it to above 80% in the bathroom. it does go down quickly when I open the window.


I'm also inquiring about the PIV system because in the winter, there is definitely condensation on the windows. it's not extremely bad, a quick wipe solves it, but if I can get rid of that by having fresher, cleaner, less damp air in the house, £300 is a really good investment.

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3 minutes ago, johnhenstock83 said:

I was only asking about damp because I would expect the readings to be much lower, around 45-50% when we're not cooking etc.

When the temperature outside is roughly the same as inside, the relative humidity RH which is what these meter measure is going to be similar to outside. Today the outside humidity where I live is below 65% here; on a damper day or early morning when the dew is evaporating it's 75%+. We're keeping inside at a lower humidity by not opening the windows.


Keep an eye on them this winter. When it's near freezing outside, that's when you expect the humidity to be in the 30-50% range indoors.

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  • 2 months later...

update: it is now cold, 4-5 degrees during the day, 0/-1 at night. without opening the windows and without any extraction is the kitchen, the humidity in the entire house is around 50%, so it must be ok. if I had a PIV or better ventilation (e.g. extractor duct instead of recirculating), I'm sure I could achieve below 40%.


turns out there's no damp at all, the house just breathes and adopts the exterior relative humidity in the summer.


turns out the "wisdom" that humidity in a house should be much lower than outside doesn't apply to houses built to breathe through walls/mortar.


thanks all!

Edited by johnhenstock83
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