Roof loft condensation problem, felt lap vents installed, initially effective, condensation returned?

[ks6788]

 

 

I went up to the loft to put a few items away & noticed the roof felts had lots of condensation especially near the top area.

After doing a bit of research online about the subject, condensation in the loft as well as watching some YouTube videos, the advice & cheapest solution is to install some felt lap vents

Purchased 20 felt lap vents, installed them as close to the eaves as possible, also near the highest point, ridge/apex area, every other rafter bay as recommended (5 on the top, 5 on the bottom). Repeated this on the opposite side.

I went up to the loft to check a couple of weeks later & the condensation had almost completely gone, I still remember it was very windy weather, yellow warning, strong wind on & off during that period.

The weather had been very cold, freezing in the last few days, I went up to the loft to check again only to be disappointed to find the roof felts condensation has returned but not as bad as before.

Although the weather has been very cold, there wasn’t much wind, quite still air so I presume the felt lap vents requires a good amount of air flow to work so the stronger the wind the longer the duration the better.

I’m thinking of purchasing another 20 felt lap vents, installed them between the spaces of the eaves & highest point, middle area every other rafter bay, repeat opposite side.

Any Idea by doing this would improve the condensation problem?

What is the idea amount of felt lap vents installed to be the most effective?

Is having too many felt lap vents installed would make it less effective?

 

Is condensation in the loft a very common problem during cold spell, should it eventually clears up on its own with windy/warmer weather?

 

 

 

 

Edited January 12 by ks6788

[Jilly]

Apparently those lap vent things don’t work brilliantly.
Have you got soffit vents? could you add more? Or ask a roofer for advice and add tile vents?
 

Also worth double checking that your bathroom or kitchen extractor fan pipes aren’t leaking into the loft, they’re often flimsy.