Loft condensation: Possible causes & remedies

Hi everyone, this isn't my usual video subject however I do feel it's important a subject as the phenomenon is quite common in houses old and new especially as the outside temperatures have dropped and the heating goes on.
Last winter (2009) I noticed water dripping onto the loft hatch and collecting on the underside of the roofing felt. After several visits by my insurer approved contractor, they seemed to think it was caused by too much junk and boxes etc in the loft that was affecting air flow across the eaves. This static air mass would then be mixed and warmed by warm moist air from the lower floors. After clearing out the loft the problem disappeared within a few days. However today I happened to look in the loft and condensation has returned - albeit greatly reduced. After careful research and trawling DIY, building and home improvement websites & forums, it seems my loft hatch is allowing warm air to pass up into the loft space. This seems to tie in with the condensation right above the loft hatch area but no where else in the loft. So I'm now either going to replace the hatch with an up to date air-sealed fully insulated type (as found on new builds & eco-homes) or re-seal and fully insulate what's there. Screwfix and many other suppliers sell these units or the materials needed to improve insulation which incidentally should be 270mm thick between joists. If you're boarding out your loft, DON'T compress the insulation - it won't work properly. You have to add wood blocks or legs to a platform so it sits above the insulation. Been told it's better NOT to use loft to store stuff. Many new-builds actually warn of this in the house-info packs.
Anyway, hope you find the video useful. Please feel free to subscribe, comment, rate etc or drop me a line through YT comms channels.
Cheers
Andrew

Category:

Howto & Style

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• Loft condensation
• Loft hatch sealing
• Loft insulation
• Loft-hatch insulation
• TK42138
• Warm air
• DIY
• Roof
• Loft conversions
• How to
• Roofing problems
• Loft and attic problems
• Improve house insulation
• Home improvement
• New-builds
• Older homes
• Home restoration
• House repair & maintenance

[G22PRODUCTIONS]

being a builder i can tell you that the main cause of condensation forming is not so much warm air getting into the loft but poor air circulation in the loft space , make sure that the loft insulation is not blocking any airways and you could also fit soffit vents and tile/slate vents

[TK42138]

@G22PRODUCTIONS

Thanks for the reply & info. Last year the specialist contractors carried out air flow test and they seemed to think the stored stuff was affecting the airflow across the inside of the roof. We saw big reduction after the loft was cleared out. Nothing has been moved or altered in the loft since last year so am assuming the hatch is the reason as eaves and soffit vents are clear. The condensation is quite small area compared to this time last year. Seems to be a popular subject.

[G22PRODUCTIONS]

@TK42138 yes having a clear out would certainly help , also you say that there is recurring damp in a certain spot [i think you said above the hatch ?] and i see in your vid that in places the underfelt is ripped , it would be worth checking to see if you have a damaged or cracked tile in that area above the felt that is allowing water in

[TK42138]

@G22PRODUCTIONS

The builders checked the roof but there was no loose or damaged tiles or ridge tiles. That was the first thing I considered when I phoned the insurers up. I'll give the eaves another inspection from inside the loft just in case some insulation has dislodged or something.

[garryentropy]

the new thinking in germany is to insulate the loft between the spars under the felt and then covering it all some hi tech plastic sheeting hermetically sealing the inside of the roof so no warm air from the house comes into contact with the cold tiles thus eliminating the cause of condensation, its expensive but it works