Ventilating Gable Walls

[EdTurtle]

Hi, I have some condensation in the loft which has started dripping onto the ceiling below. I have had a recent new dormer roof, and i think the increase in insulation has reduced the ventilation in the rest of the loft. Having said that, I think the previous owners have had problems as they have installed lap vents (I've never noticed a problem - but it may have existed and i just didnt notice). Neighbours have similar problems around here, as most have installed gable vents. I am going to install vents on both gables to see if it alleviates the problem, before going with ventilated ridges/eaves if not. Trouble with venting the eaves is the air will only flow around the sides of the dormer into the loft, so not a lot of width (can provide picture if unclear).

Problem is, I dont have a core drill. Can i just buy a 9inch square vent, drill a load of holes (say 10mm or would 20mm be better - just less holes) through the wall and put the vent over the holes inside and out? This is how the gas vent is done (in the 70s when the baxi boiler was installed). I will be venting both gable walls.

Thanks

 

[phatboy]

That will take you a long time to do, have you enquired as to the cost of hiring a core drill for a half day? Probably worth it, unless you have a day you need to fill!

If you have a cavity wall, you should sleeve the vent so the air flows from outside to inside the roof space and not into/out of the cavity.

 

[EdTurtle]

I had considered a core drill to hire, but it would only be about twenty holes to do, even at a minute per hole its only going to be an hour total time including getting the ladder up. Probably should mention the blocks are thermalite, so easy to drill.

I have cavity insulation, so that would stop the air going into the cavity wouldnt it?

Thanks

 

[pilsbury]

If I’m understanding correctly, you intend to drill lots of little holes and cover that with a louvred vent of sorts? That’s bonkers. I also wouldn’t hire a core drill for that little job. Just draw around the circular vent outlet and drill lots of 10mm holes on that line as close together as you can. The get a hammer and bolster chisel and wack it out. Same on the inside. To get the holes lined up, I just drilled a single centre hole with a 450mm drill bit first so I could line up the inside vent. Easy peasy - got to be 20minutes max.

as said if it’s a cavity wall slip some plastic pipe in linking the 2 vents.

 

[EdTurtle]

That’s bonkers.

Why?

The get a hammer and bolster chisel and wack it out.

I had considered this, but i'm a little bit apprehensive going up on the ladder and whacking the wall with a chisel. Also, worried about not making a 'clean' hole, thermalite tends to split easily and come off in chunks i find.

What about if i were to use a 40mm core drill instead, i have a 40mm drill, and 40mm pipe so I could sleeve that. Would this be big enough do you think?

Thanks

 

[mikeey84]

If they are thermalites you can use a metal blade on a jigsaw and cut the shape out, starting from a pilot hole. This is what I did when I needed to retro fit a square vent.

With thermalites you could probably use a bread knife.

 

[gasbanni]

Can you see where the condensation is occurring ? Surley insulating so you don't get condensation is the best option ?

Ventilation is required true but I'd be trying to find out why the condensation is occurring .....have you checked the extraction in the bathroom ?

 

[EdTurtle]

The condensation is occurring nowhere near the bathroom, and we have a vapour barrier across the whole loft. The trouble is where the roofer has installed new insulation in the dormer (i think) there is now no airflow through the loft except either side of the dormer, which is presumably not enough. Condensation has mostly dried up now, just a drip down the bottom - i'm almost inclined to say the roof is leaking there, hence the increase in condensation overall. He's coming back to look again soon, so i'll monitor it