vented soffit - blessing or curse?

[Jupiter01]

upon advice from my builder, we had vented soffits installed on our ground floor extension. They have vents all along the 10 metre strip.

I have now put holes (downlights) in the plasterboard on the inside and can feel a strong draft coming through. It's also coming through some parts of the plasterboards as the air is travelling down the cavity.

it seems like a bad idea but I would like you advice? Assuming, I should replace them. Can I do this without removing facsia and guttering?

 

[tomfe]

The soffit vents should vent into the space above your roof insulation not into the warm void above your ceiling.
The draft may just be air movement between the wam room and the slightly cooler void.

 

[Jupiter01]

Thanks for the reply. What you have stated above makes perfect sense for a first floor roof and the loft space but am struggling to translate that to a ground floor situation. Let me elaborate...

As indicated in the picture above, my ground floor has a 1 metre pitched roof and the rest of the lounge has bedrooms above it. The pitched roof has insulation but the part of the ceiling below the bedroom doesn't. Since the vented soffit goes all along the length of this room. The air is spreading through the entire room as it is going through the pitched roof and into the ceiling space below the bedrooms. I hope this makes sense.

 

[Chud]

The downlights are the issue IMO - from what I know they either cannot have insulation over the top of them or they need to be fitted with fire hoods - hence you have a straight line of flow from the soffit vent to the hole in your ceiling.

 

[Jupiter01]

you are right about the line of air flow and incidentally, my downlights are insulation coverable. It still doesn't make sense to me that I have all of this cold air being sucked into my room?

 

[Chud]

you are right about the line of air flow and incidentally, my downlights are insulation coverable. It still doesn't make sense to me that I have all of this cold air being sucked into my room?

if you remove a downlight can you see insulation above it?

 

[Jupiter01]

Technically yes as I have placed sound insulation in this area (pushed up towards floorboards of bedroom). Note there are bedrooms above this part of the lounge. The lounge also extends out to where I have the pitched roof (1 metre) and in this area, there is plenty of loft insulation.

 

[tomfe]

So you are putting holes in the ceiling in the original building not the extension?
There should be no passage of air from the extension roof into the roof void, this is not only for energy performance but wise for fire.

 

[Jupiter01]

My entire lounge is part of the extension. 4 metres of this has bedrooms above it and the extra 1 metre is the pitched roof. I hope this makes sense...
The spot lights are in the lounge but in this pitched roof part (I think I misled you earlier, sorry!). Hence, the air is pouring out of these holes.

 

[tomfe]

If you have no insulation above your ceiling in the pitched roof area then you need some. This is what it should/might be like in first image:

Are you sure you've not moved the insulation out of the way?

 

[Jupiter01]

There is tonnes of insulation n this area. I have celotex in between the rafters (with airflow gap) I have then also placed rockwool but I am still getting lots of air coming through.

Why do I need vented soffits in this situation? Also, I should ahve mentioned that I am using breathable felt.

 

[tomfe]

You should not have an unvented void between your insulation in the rafters and the insulation above your ceiling. You don't need any roof vents if you have breathable membrane/felt as long as it's sutaible.

 

[Jupiter01]

do I need to remove and replace soffit? Is this possible without disturbing the fascia?