Loft condensation

cyber69

cyber69

cyber69

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Loogabarooga
Happy new year all, i'm starting off 2026 with a loft issue with condensation forming on the felt in the form of water beads all over one particular side near the loft hatch. I've put a sensor up there and it's reading 7deg with 83% humidity, not sure if that's really bad but I think the humidity is quite high.

We had replacement facia's and soffits a couple of years ago so i'm thinking maybe they did not put any or enough vents in to keep the air flowing. To try and resolve it, i've seen some plastic spacers that fit inbetween the felt to provide an air gap, anyone had any experience of using these?
 
This can happen pretty easily if people store xmas decorations up in the loft etc. You have high condensation levels in your house (or your loft hatch is just above the bathroom after someone has had a shower) then open the loft hatch for a while to get things down etc. Not to mention you're up there breathing for a while too.

Then you close the hatch and trap all the moisture up there with nowhere to go and it just goes through cycles of condensing and evaporating.

Modern roofs are designed to be air tight where as older houses have wind blowing through them most of the time!

You may just need to put a dehumidifier up there to reduce the moisture then go up and get it quick before you let more moisture up there again. :p

Or ideally, reduce the moisture level in the loft as well as near to the loft hatch then go up and get it.

Edit: You could also have a slight leak letting rain water in as well but most likely it's just condensation from leaving the hatch opened.
 
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This is a good video:


Most mold problems or damp issues are caused by the people living in the house or changing the way the property was designed to naturally breathe etc.

We run a dehumidifier every now and again and have a positive input ventilation system as well because our house has solid walls and has no cavity etc. We use a tumble dryer and only dry very few items on the radiator and during winter I Karcher vac the windows to get the condensation off and stop it cycling back round again.

Opening a window is great providing the humidity outside isn't super high (or it's raining) as you just swap humid air for humid air! Dehumidifiers or aircon units are your best option but they do cost.
 
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Our previous house had had the loft converted and until I got a dehumidifier up there the velux windows would get coated in water in the winter.

A dehumidifier did solve the problem though. The air vents were still there for the rest of the roof space but the conversion had created it's own sealed moisture trap.
 
cyber69 said:
Happy new year all, i'm starting off 2026 with a loft issue with condensation forming on the felt in the form of water beads all over one particular side near the loft hatch. I've put a sensor up there and it's reading 7deg with 83% humidity, not sure if that's really bad but I think the humidity is quite high.

We had replacement facia's and soffits a couple of years ago so i'm thinking maybe they did not put any or enough vents in to keep the air flowing. To try and resolve it, i've seen some plastic spacers that fit inbetween the felt to provide an air gap, anyone had any experience of using these?
Click to expand...

Get a PIV system I fitted on a couple of years ago it's worked well. Didn't fancy cutting hole in the plaster ceiling so I fitted it to the loft hatch.

www.condensationproducts.co.uk

Nuaire Drimaster DRI-ECO-HC PIV

Nuaire Drimaster DRI-ECO-HC PIV
www.condensationproducts.co.uk www.condensationproducts.co.uk
 
hornetstinger said:
Get a PIV system I fitted on a couple of years ago it's worked well. Didn't fancy cutting hole in the plaster ceiling so I fitted it to the loft hatch.

www.condensationproducts.co.uk

Nuaire Drimaster DRI-ECO-HC PIV

Nuaire Drimaster DRI-ECO-HC PIV
www.condensationproducts.co.uk www.condensationproducts.co.uk
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That works for the rest of the house but ONLY if the roof is breathable, or has vents etc. Sealed modern roofs won't work with PIV systems unless they're ducted out. They are a good thing for most houses though if the design is right.
 
We had the cavity wall insulation with the small foam beads and ever since have suffered with condensation upstairs. Have one dehumidifier running in the conservatory and another one running in a bedroom to try and combat the damp.
 
Put something between the laps of the felt to allow air to circulate. I used some pipe insulation cut in half length ways, just needed a few done on each side and it started my issue.
 
Fitted 12 spacers easy enough and wiped down the felt, the condensation seems to be only in one section, near the top 50% of the apex of the roof, near the loft hatch, rest of the loft is pretty dry compared to that section.

Ordered another 12 spacers just incase as I didn't quite have enough.
 
cyber69 said:
Fitted 12 spacers easy enough and wiped down the felt, the condensation seems to be only in one section, near the top 50% of the apex of the roof, near the loft hatch, rest of the loft is pretty dry compared to that section.

Ordered another 12 spacers just incase as I didn't quite have enough.
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Hope it sorts the issue out for you. Definitely keep an eye on it though as you don't want it damaging your roof!

Randomly, just Googled your location as I was thinking you're from some country in Africa to find it's a way of saying Loughborough. :cry:
 
cyber69 said:
Fitted 12 spacers easy enough and wiped down the felt, the condensation seems to be only in one section, near the top 50% of the apex of the roof, near the loft hatch, rest of the loft is pretty dry compared to that section.

Ordered another 12 spacers just incase as I didn't quite have enough.
Click to expand...
I did the same on our old house about 15 years ago & they did the job in cold weather. You're almost always going to have some condensation on felt in cold, still weather as its not breathable like modern membranes. Just make sure you don't lose the little springs down the felt like I did ;)

Edit - you could probably do with looking at the seals around the loft hatch as that's the most likely source of warm air.
 
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Just been up there to fit the rest of the spacers and the loft boards are now dry, the felt has a lot less droplets and seems to still be drying so hopefully the spacers have done job.
 
cyber69 said:
Just been up there to fit the rest of the spacers and the loft boards are now dry, the felt has a lot less droplets and seems to still be drying so hopefully the spacers have done job.
Click to expand...
Do you have bitumen felt? Did the units slot in easily? Which ones did you buy, link?
 
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Thought I'd give this a go too. I don't have any visible condensation but do have black mold growing on some of the felt and consistently high humidity readings. I installed 6 along the worst of it at 20:25 tonight but opening the loft hatch spiked the humidity and it's yet to come back down, hoping to see some improvement overnight.
Screenshot-2026-01-05-at-22-19-23.png
 
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