Mould growing on things in new loft

[catlad]

That amount of moisture must be coming from your
house somewhere! Are you sure that is a breathable membrane?

 

[JP_]

No idea about the membrane. I assume it is, how can iI find out?

 

[catlad]

Going to be a bit tricky now, I would move a few roof
tiles and find out what the specification is from the
writing on the membrane.

 

[John D v2.0]

Shouldn't be anywhere near that temperature in the loft, if the humidity is that level and it's that warm there's definitely warm air leaking from your living space. The felt will be very cold as it's not the insulated layer, and even breathable will get wet in extreme situations.
I'd suggest looking for air leaks. If it's mainly closer to the existing loft and the loft spaces are open to each other, especially if the insulation is better in the new area you need to check all ceilings and even air leakage through stud walls into the ceiling void. Any pipe work or cable holes would be a suspect.

 

[JP_]

Shouldn't be anywhere near that temperature in the loft,

It did reach 13.25 degrees today, and the hatch was probably open for about half an hour before that pic. And that was right next to the extractor which was warm. The new loft is def much colder than old.

Ill sese up that extractor gap next and see if that helps.

 

[Keithmac]

Our loft space is freezing cold in winter but bone dry. Wouldn't waste energy warming the loft personally.

 

[JP_]

It is cold up there. I put the insulation back as that made no difference. Most roof felt is wet to touch. I did some Googling and discovered Felt Lap Vents - it seems I am not alone in this problem.
Inspired by that, I put in some makeshift vents using a combination of pipe insulation and offcuts of insulation board cut into wedges. Aim was to make tiles visible in each section to increase ventilation.

There are 2 types of felt membrane in the loft, one is grey and the other black. The grey seems drier. Maybe the black is not breathable.

Also, no signs of ventilation in the eaves - no vents on the underside of the soffits. The soffits are plastic, so surprised vents not in there as standard. Should I get out my drill and put some vents in? Found these soffit vents.

Also, just been reading about ridge vents - as the ridge is covered in ridge tiles and all looks pretty watertight, would it be crazy to cut some ventilation strips in the centre (i.e. where driving rain could never get) to help the moist air escape upwards? It does seem wettest along the ridge.

Will review in a few days, will hopefully have a sunny day soon to help dry out what is there then see if it stays dry.

Building regulations? Is loft ventilation covered by building regs? They did not pick up anything, but I've not had the final sign off yet (just need to put in an internal door) but maybe I could mention this - if it is something that should have been done I should be in my rights to request the builder do it?

 

[JP_]

Right, vent's have possibly made a difference. Added more vents (about 40 now) and got 2 fans blowing up there to try to encourage the air to move.
Temperature is recording as 10 degrees, which is only a little warmer than outside temperature in Essex today.

Eaves are packed with insulation, but there are no vents in the soffits so it makes no difference until some vents put in. I'll get vents put in asap.

Also there was a slight leak from the kitchen extractor ducting where it had not been properly sealed. More tape added, hopefully that will help too. The only source of heat/moisture into the loft space is the kitchen / living room below.

More photos.

Daylight!

Blocked insulation in eaves

Loft and outside weather update

 

[JohnD]

you don't have downlighters/spots?

also known as "holes in the ceiling so warm damp air can rise into the loft?"

 

[JP_]

No, none. Too expensive and a PITA to change the bulbs!

 

[JP_]

the kitchen and hallway ceilings.

 

[JP_]

Just ordered 25 Roofing Felt Lap Vents which will hopefully do a better job.

Fans are drying it out. Hopefully it will stay dry once every overlapping bit of felt is replaced with a vent.

 

[JP_]

Loft still mostly clear of condensation, loft temperature and humidity matching external.

Need a cold night to see what happens....

 

[Leofric]

Why are you doing these modifications to improve ventilation to the roof space yourself ? In answer to your question, yes ,ventilation of the roof space is covered under Building Regulations and the Building Control Officer should ensure it has been carried out by the builder;so you should discuss what has been done with the builder and BCO. Ventilation is required at the eaves, with rafter trays to prevent insulation obstructing the airflow, if the roofing membrane is not breathable .(I think it is also a good idea to fit an air brick in the gable wall.) If it doesn't comply with Building Regs on ventilation the builder should rectify it, you shouldn't need to do any remedial work yourself. Ventilation at the eaves can be by an over fascia type of vent if there is no soffit.
ps I have repeated some points others have already made.
Ridge vents are only required in certain circumstances .
You can view Bldg Regs Approved Documents on The Planning Portal or LABC website to see ventilation requirements, can't go into them all here.

 

[JP_]

Thanks. I did it because it needed doing and i knew it would be weeks by the time the inspector came out and i got the builder back over Christmas. Will call the council next week, assuming they are not working tomorrow.