5 degree slope for vents and extractor fans

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Simmo0020

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• 17 Feb 2016

• #1

Hi I am planning on installing some vents in bedrooms and a bathroom fan to help deal with condensation issues.

The installation instructions state that the pipe must slope downwards 5 degrees to stop any condensation coming back in to the vent/fan.

If drilling the hole with a core drill bit what is the best way to do this, I ask because I have seen warnings that state not to drill at any angle with a core drill.

 

Madrab

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• 18 Feb 2016

• #2

Lean a small level along the top of the drill and have the bubble just off level towards you. Easiest way to cut the angle is start the corer level to the wall, cut in a couple of mill, then apply the angle, use a variable speed and slowly cut in another few mill till it frees up, then up to speed and just keep the drill at that same angle till through.

 

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Doggit

• 18 Feb 2016

• #3

5 degrees is a nominal figure, and all you need is a bit of a slope so that any steam that condenses in the vent tubing runs outwards, rather than back in to the bathroom. You start the coreing process by drilling your pilot drill through the wall to the outside, then put your lead drill in the centre of the core bit, and that'll follow the pilot hole. When you start drilling the pilot hole, get someone to visually check that you've got a slight downward tilt to the drill, and that should get you started nicely. When you start coreing, you'll just be biting in to the top of the circle for about a minute, till you're cutting in evenly all round.

Next time you'll judge the downwards angle on your own, and be fine.

 

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Simmo0020

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• 18 Feb 2016

• #4

Thanks Gents.

I think I can manage that.

The bathroom has an airbrick opening which appears to lend itself well to using as a ducting point for the wall fan and allow me to pack out the front to provide a downward slope. I've decided to install a warm air dehumidifier unit instead of a normal fan.

I plan to fill the space around the ducting with expanding foam, can anyone forsee any issues with this plan?

 

Madrab

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• 18 Feb 2016

• #5

As long as the brick hasn't been installed for anything else, specific ventilation etc, then no real reason not to use the space.

 

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Simmo0020

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• 18 Feb 2016

• #6

No it's just a cut out for the airbrick which no longer be required.

I feel that expanding foam will be most convenient method to fill the unused space around it?

 

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Doggit

• 19 Feb 2016

• #7

Basically a good plan, but you might be better off using adhesive foam instead. You're going to get a lot of vibration from the fan, and the expanding foam may let it vibrate more than the adhesive one. Oh, and don't forget to cement the outside; foam isn't UV stable, and will discolour.