Loft ventilation through eaves/fascia boards

[Timmyk86]

Hi everyone

I was referred over here from the loft forum as I'm having trouble ventilating my loft space.

I have a Victorian semi-detached house with a slate roof and impermeable plastic undersarking. There's no obvious ventilation for the loft. One side is a brick gable end with the chimney breasts. There are no soffits and there doesn't appear to be any eave vents either. Theres no daylight coming in around the fascia boards.

There is not enough ventilation up there, and there is a fair amount of white mould on the wood. The condensation was terrible over Christmas, it was almost raining on the inside of the undersarking.

I have fitted 10 x Lap vents to try to improve ventilation but noticed that the overlaps in the undersarking are quite large and not all the vents separate the entire overlap - so they probably aren't as effective as I want them to be.

I'd be grateful for some opinions on the best way to ventilate it. I'll probably have it converted in the not too distant future so probably need to take that into account.

Is there a way I can make vents in the fascia boards? Or do I need ridge vents/vent tiles?

Also JohnD mentioned that the wood looks like it might have been wet - any opinions on that would also be great. I'm hoping they look okay to you all!

Thanks in advance
Tim

 

[noseall]

Tile vents top and bottom and plenty of them.

EDIT: just noticed you have slates... Bu££er.

Other than introducing air bricks into the gable end (where possible) your only option is to try and persevere with the lap vents until you can get a roofer to fit cross ventilation via over-fascia vents and ridge vents - but this would involve removing tiles etc.

Is that the back of the fascia I can see in 3rd image?

 

[Timmyk86]

Tile vents top and bottom and plenty of them.

EDIT: just noticed you have slates... Bu££er.

Other than introducing air bricks into the gable end (where possible) your only option is to try and persevere with the lap vents until you can get a roofer to fit cross ventilation via over-fascia vents and ridge vents - but this would involve removing tiles etc.

Is that the back of the fascia I can see in 3rd image?

Thanks for the quick reply!

I could try to put an air brick in the gable end, but that would be just one I think (as there's a point where there's just a single brick. Might not provide much flow. I've ordered some more lapvents to make 20 total.

Yep - 3rd photo is the back of the fascia board. What do you think?

 

[datarebal]

air brick in gable, thru vent slates and up the insulation at ceiling level including the hatch.

if the fascia is not to firmly fixed, then carefully ease it off , cut it down by 40mm and fit over fascia vents, re fit and put the gutter back

 

[Leofric]

Just replied in the other forum before I saw this.

 

[Timmyk86]

air brick in gable, thru vent slates and up the insulation at ceiling level including the hatch.

if the fascia is not to firmly fixed, then carefully ease it off , cut it down by 40mm and fit over fascia vents, re fit and put the gutter back

That's great, thanks. I think over fascia vents would probably be the best option. Sadly probably not something I can do myself though. Any ideas how much that sort of thing would cost to have done professionally?

 

[Leofric]

Before you go too far I would look into how you think your future loft conversion might work.

 

[^woody^]

You need to stop warm air getting up there to condense in the first place, so insulate the ceiling. Otherwise no ventilation will help.

Next, make some timber wedges, or form some polystyrene blocks and place these in the membrane laps to open them up.

 

[Timmyk86]

You need to stop warm air getting up there to condense in the first place, so insulate the ceiling. Otherwise no ventilation will help.

Next, make some timber wedges, or form some polystyrene blocks and place these in the membrane laps to open them up.

Good point. Thanks. I was actually thinking of overboarding the lath and plaster ceilings with insulated plasterboard so that would help. That stuff seems bloody expensive though.

I think the plan initially will be to add a bunch more LapVents and also try to open up the laps at the apex. Over fascia vents would probably be the best permanent option but as Leofric said, that might be something to do when the loft is converted as there will be scaffolding etc up there already.

 

[^woody^]

Over fascia vents would probably be the best permanent option

You wont be able to fit these as they will alter the height of the slates and gutter, and reduce the fascia depth.

If you are having a loft conversion then that will sort the problem out as you will be insulating between the rafters so the problem will be designed out. And that awful plastic membrane should be changed for a breathable type at that time.

 

[Timmyk86]

You wont be able to fit these as they will alter the height of the slates and gutter, and reduce the fascia depth.

If you are having a loft conversion then that will sort the problem out as you will be insulating between the rafters so the problem will be designed out. And that awful plastic membrane should be changed for a breathable type at that time.

What about what datarebal suggested- fascia off, cut 40mm or so off the top edge, re-fit with fascia vents? You don’t think that would work?

Also my understanding is that there still would need to be ventilation between the undersarking and insulation/plasterboard in the loft.

 

[^woody^]

Going by the photo, it looks like you wont be able to fit over-fascia vents without lowering the gutter. Then you need to install what is called rafter roll, to duct air between the membrane and insulation at the eaves.

 

[datarebal]

They will go