Do These Roof Exhaust Fans Let In The Rain?

[Naam]

Vented soffits were designed as an air intake and not as a method of venting, the idea being that hot air rises and if allowed to escape near the ridge, cooler air will be drawn into the roof void from below, via the vented soffits.

The idea that hot air will vent from the soffits in an otherwise sealed roof is nonsense, especially since the soffits are often lower than upstairs ceiling height, the hot air from the void therefore permeates the upstairs ceiling and makes the bedrooms hot before the hotter air has any chance of partial escape via the soffits - if only hot air didn't rise, it could be a decent solution.

[Tywais]

Vented soffits were designed as an air intake and not as a method of venting, the idea being that hot air rises and if allowed to escape near the ridge, cooler air will be drawn into the roof void from below, via the vented soffits.

The idea that hot air will vent from the soffits in an otherwise sealed roof is nonsense, especially since the soffits are often lower than upstairs ceiling height, the hot air from the void therefore permeates the upstairs ceiling and makes the bedrooms hot before the hotter air has any chance of partial escape via the soffits - if only hot air didn't rise, it could be a decent solution.

That is exactly how it is explained in the link I supplied and makes full sense unless the soffits are mounted upside down on the roof.

[krisb]

They let rain in when the things not sealed on the roof properly.

The amount of rain that would get through the vent bit that spins should be miniscule.

[UKJASE]

ok guys - as OP i have been following this thread closely, and much appreciate all the good ideas from everyone

i am thinking this is the best way to go for our roof on our new build (4 bedroom bungalow, situated in the sticks, usually having a decent breeze)

- ventilated sofits

- silver foil underneath the main steel structure, leaving a 15 cm gap for hot air to vent upwards between foil and monier CPAC tiles

- extractor fans in the ceiling drawing hot air out the house in the evenings, into the roof space

- large vents at both gable ends

- two large fans at either gable end, extracting air from the roof, and blowing it outside

- insect screens over all vents to prevent creepy crawlies entering

- i think we will stay away from the whirlybird type exhaust chimneys, as they may leak, plus look ugly

- we will also stay away from vented ridge tiles, as these may leak on occasion too

what do you guys think of this plan?

PS our intention is not to use the AC, hence the extractor fans in the ceiling

[chiang mai]

That works for me, good luck.

[chiang mai]

One more thought: I'd make the gable end fans thermostatically controlled with the controls inside the house so they can be adjusted and the tempreture sensors located mid point in the roof void.

[Naam]

ok guys - as OP i have been following this thread closely, and much appreciate all the good ideas from everyone

i am thinking this is the best way to go for our roof on our new build (4 bedroom bungalow, situated in the sticks, usually having a decent breeze)

- ventilated sofits

- silver foil underneath the main steel structure, leaving a 15 cm gap for hot air to vent upwards between foil and monier CPAC tiles

- extractor fans in the ceiling drawing hot air out the house in the evenings, into the roof space

- large vents at both gable ends

- two large fans at either gable end, extracting air from the roof, and blowing it outside

- insect screens over all vents to prevent creepy crawlies entering

- i think we will stay away from the whirlybird type exhaust chimneys, as they may leak, plus look ugly

- we will also stay away from vented ridge tiles, as these may leak on occasion too

what do you guys think of this plan?

PS our intention is not to use the AC, hence the extractor fans in the ceiling

i think you'll be sweating a lot.

[UKJASE]

ok guys - as OP i have been following this thread closely, and much appreciate all the good ideas from everyone

i am thinking this is the best way to go for our roof on our new build (4 bedroom bungalow, situated in the sticks, usually having a decent breeze)

- ventilated sofits

- silver foil underneath the main steel structure, leaving a 15 cm gap for hot air to vent upwards between foil and monier CPAC tiles

- extractor fans in the ceiling drawing hot air out the house in the evenings, into the roof space

- large vents at both gable ends

- two large fans at either gable end, extracting air from the roof, and blowing it outside

- insect screens over all vents to prevent creepy crawlies entering

- i think we will stay away from the whirlybird type exhaust chimneys, as they may leak, plus look ugly

- we will also stay away from vented ridge tiles, as these may leak on occasion too

what do you guys think of this plan?

PS our intention is not to use the AC, hence the extractor fans in the ceiling

i think you'll be sweating a lot.

the wife is from issan Naam, as is the step daughter, and i am from tropical middlesbrough. we hardly use the AC in our current house, and i dont think this build we are in now has incorporated half the features as mentioned above

i reckon it will be cool enough for us all throughout the year. we will have a couple of wall fans too, plus some desk and floor fans

maybe 30 mins of AC in the hot season before bed is all we will need

i am not sure what sort of fans we should use in the roof space though, to blow the air out the vents at either end. i was looking at the wall extractor fans, but they would be difficult to fit to the air vents i think

do you think we should use a fan at either end, or is this overkill maybe? the wife doesnt look best impressed with the idea, but unless she has seen someone else doing it in their house in issan, she generally isn't impressed with my ideas anyway

[chiang mai]

My ten cents: if you look around you can find up to 50 inch industrial strength fans that have automatic louvers based on the thermostat settings, not expensive at all, wall extractor fans wont do the trick. OK, I'm done here.

[kannot]

ok guys - as OP i have been following this thread closely, and much appreciate all the good ideas from everyone

i am thinking this is the best way to go for our roof on our new build (4 bedroom bungalow, situated in the sticks, usually having a decent breeze)

- ventilated sofits

- silver foil underneath the main steel structure, leaving a 15 cm gap for hot air to vent upwards between foil and monier CPAC tiles

- extractor fans in the ceiling drawing hot air out the house in the evenings, into the roof space

- large vents at both gable ends

- two large fans at either gable end, extracting air from the roof, and blowing it outside

- insect screens over all vents to prevent creepy crawlies entering

- i think we will stay away from the whirlybird type exhaust chimneys, as they may leak, plus look ugly

- we will also stay away from vented ridge tiles, as these may leak on occasion too

what do you guys think of this plan?

PS our intention is not to use the AC, hence the extractor fans in the ceiling

i think you'll be sweating a lot.

the wife is from issan Naam, as is the step daughter, and i am from tropical middlesbrough. we hardly use the AC in our current house, and i dont think this build we are in now has incorporated half the features as mentioned above

i reckon it will be cool enough for us all throughout the year. we will have a couple of wall fans too, plus some desk and floor fans

maybe 30 mins of AC in the hot season before bed is all we will need

i am not sure what sort of fans we should use in the roof space though, to blow the air out the vents at either end. i was looking at the wall extractor fans, but they would be difficult to fit to the air vents i think

do you think we should use a fan at either end, or is this overkill maybe? the wife doesnt look best impressed with the idea, but unless she has seen someone else doing it in their house in issan, she generally isn't impressed with my ideas anyway

I would also look closely at wall construction to minimize heat, double block walls etc even if just on the sunny side aac aerated blocks 7.5cm

[Naam]

ok guys - as OP i have been following this thread closely, and much appreciate all the good ideas from everyone

i am thinking this is the best way to go for our roof on our new build (4 bedroom bungalow, situated in the sticks, usually having a decent breeze)

- ventilated sofits

- silver foil underneath the main steel structure, leaving a 15 cm gap for hot air to vent upwards between foil and monier CPAC tiles

- extractor fans in the ceiling drawing hot air out the house in the evenings, into the roof space

- large vents at both gable ends

- two large fans at either gable end, extracting air from the roof, and blowing it outside

- insect screens over all vents to prevent creepy crawlies entering

- i think we will stay away from the whirlybird type exhaust chimneys, as they may leak, plus look ugly

- we will also stay away from vented ridge tiles, as these may leak on occasion too

what do you guys think of this plan?

PS our intention is not to use the AC, hence the extractor fans in the ceiling

i think you'll be sweating a lot.

the wife is from issan Naam, as is the step daughter, and i am from tropical middlesbrough. we hardly use the AC in our current house, and i dont think this build we are in now has incorporated half the features as mentioned above

i reckon it will be cool enough for us all throughout the year. we will have a couple of wall fans too, plus some desk and floor fans

maybe 30 mins of AC in the hot season before bed is all we will need

i am not sure what sort of fans we should use in the roof space though, to blow the air out the vents at either end. i was looking at the wall extractor fans, but they would be difficult to fit to the air vents i think

do you think we should use a fan at either end, or is this overkill maybe? the wife doesnt look best impressed with the idea, but unless she has seen someone else doing it in their house in issan, she generally isn't impressed with my ideas anyway

one fan properly placed is enough. capacity according to attic volume and last not least soffit intake area (small intake area = more capacity reqired). what's the attic area and the roof pitch?

p.s. hailing from 'from tropical middlesbrough' is a huge advantage

[UKJASE]

ok guys - as OP i have been following this thread closely, and much appreciate all the good ideas from everyone

i am thinking this is the best way to go for our roof on our new build (4 bedroom bungalow, situated in the sticks, usually having a decent breeze)

- ventilated sofits

- silver foil underneath the main steel structure, leaving a 15 cm gap for hot air to vent upwards between foil and monier CPAC tiles

- extractor fans in the ceiling drawing hot air out the house in the evenings, into the roof space

- large vents at both gable ends

- two large fans at either gable end, extracting air from the roof, and blowing it outside

- insect screens over all vents to prevent creepy crawlies entering

- i think we will stay away from the whirlybird type exhaust chimneys, as they may leak, plus look ugly

- we will also stay away from vented ridge tiles, as these may leak on occasion too

what do you guys think of this plan?

PS our intention is not to use the AC, hence the extractor fans in the ceiling

i think you'll be sweating a lot.

the wife is from issan Naam, as is the step daughter, and i am from tropical middlesbrough. we hardly use the AC in our current house, and i dont think this build we are in now has incorporated half the features as mentioned above

i reckon it will be cool enough for us all throughout the year. we will have a couple of wall fans too, plus some desk and floor fans

maybe 30 mins of AC in the hot season before bed is all we will need

i am not sure what sort of fans we should use in the roof space though, to blow the air out the vents at either end. i was looking at the wall extractor fans, but they would be difficult to fit to the air vents i think

do you think we should use a fan at either end, or is this overkill maybe? the wife doesnt look best impressed with the idea, but unless she has seen someone else doing it in their house in issan, she generally isn't impressed with my ideas anyway

one fan properly placed is enough. capacity according to attic volume and last not least soffit intake area (small intake area = more capacity reqired). what's the attic area and the roof pitch?

p.s. hailing from 'from tropical middlesbrough' is a huge advantage

The roof pitch is 30 degrees Naam, and the attic area must be in the region of 350m2. we have bought 100 Soffit boards with quite large intake holes, which will run along both entire long sides of the roof

so you think one fan will be enough? do you think a large industrial fan, as suggested above, will do the job, maybe hang it from one of the roof supports and have it blowing towards the gable end vent? the only problem i see with a large fan like this is it will disrupt the hot air that has gathered at the top of the roof space, and will likely mix it up with all the cooler air down below.

maybe a more directional fan could be used, that will extract air from the pocket of hot air at the top of the roof space, and blow it out the vents, without disrupting the other air that has gathered there ?

[Naam]

The roof pitch is 30 degrees Naam, and the attic area must be in the region of 350m2. we have bought 100 Soffit boards with quite large intake holes, which will run along both entire long sides of the roof

so you think one fan will be enough? do you think a large industrial fan, as suggested above, will do the job, maybe hang it from one of the roof supports and have it blowing towards the gable end vent? the only problem i see with a large fan like this is it will disrupt the hot air that has gathered at the top of the roof space, and will likely mix it up with all the cooler air down below.

maybe a more directional fan could be used, that will extract air from the pocket of hot air at the top of the roof space, and blow it out the vents, without disrupting the other air that has gathered there ?

forget about any clowneries such as "hanging and blowing towards..." or "ducts" or "more directional fan"!

this is what you need mounted directly on the vent. cost approximately 2,300-2,800 Baht. add a simple timer ~300 Baht and you are set.

p.s. you are lucky to have gables (a breeze to install a vent as opposed to a home with a 4-side hip roof).

Edited July 12, 2014 by Naam

[UKJASE]

The roof pitch is 30 degrees Naam, and the attic area must be in the region of 350m2. we have bought 100 Soffit boards with quite large intake holes, which will run along both entire long sides of the roof

so you think one fan will be enough? do you think a large industrial fan, as suggested above, will do the job, maybe hang it from one of the roof supports and have it blowing towards the gable end vent? the only problem i see with a large fan like this is it will disrupt the hot air that has gathered at the top of the roof space, and will likely mix it up with all the cooler air down below.

maybe a more directional fan could be used, that will extract air from the pocket of hot air at the top of the roof space, and blow it out the vents, without disrupting the other air that has gathered there ?

forget about any clowneries such as "hanging and blowing towards..." or "ducts" or "more directional fan"!

this is what you need mounted directly on the vent. cost approximately 2,300-2,800 Baht. add a simple timer ~300 Baht and you are set.

p.s. you are lucky to have gables (a breeze to install a vent as opposed to a home with a 4-side hip roof).

fan.JPG

thanks Naam man - that fan looks like what i had in mind. i was going to use as large an extractor fan i could find, the type that are designed for bathroom spaces, but that one looks more industrial sized. will i find this in thai watsadu and the like, or will i have to go to a smaller independent place?

[chiang mai]

You'll need to go to a small independent shop, I've done the rounds of all the major building supply stores here in Chiang Mai (Global House, and the like) and they have nothing that's even close, presumably it's the same in Hua Hin - a small independent shop nearby had a range of them however.

[Naam]

thanks Naam man - that fan looks like what i had in mind. i was going to use as large an extractor fan i could find, the type that are designed for bathroom spaces, but that one looks more industrial sized. will i find this in thai watsadu and the like, or will i have to go to a smaller independent place?

the types used for bathrooms (25-40W) do not possess the efficiency to ventilate an attic with a footprint of 350m² properly. i admit that i went i bit overboard with my suggestion of 250W, but it's neither overkill nor wasted energy because you can adjust the run times according to the ambient temperatures, respectively sun radiation. i'm going even further and claim the fan is for free because you can save on the useless aluminium foil which does not prevent but only slows down the temperature built-up in your attic.

here in Pattaya i know at least three shops which sell these fans in several different sizes from 100W to 350W. if they are not available in your area a small shop will order one for you.