Ceiling Insulation For New House Thai Style

[haveaniceday]

Need some advice re roof insulation. We are using 120 X 50 panels, the lightest color we were happy with.

We intend to have a gypsum ceiling, not the 60 x 60 squares hanging form the rafters. I am not sure how the builder intents to support the gypsum panels though to the horizontal beams across the roof.

No the problem, I want to do it on a tight budget as insulation is a subject I am not getting much support on, I presume, no one can see so it is not needed !!!

Under the eves I am getting the panels that have many slits with a wire mesh over it to keep vermin out, this will be on the 4 sides.

It is a simple A frame roof basically, with a little bit of fancy stuff on one end, but essentially just a triangle.

On each end, we will have static horizontal vents on the flat section near the apex.

Now I need advice, the builder wants to put foil under the roof panels, how effective is thin foil ?

Is the foil with 2-5mm of white foam bought as rolls much more effective? The are much more expensive but I imagine would also help with noise form rain as well, maybe, need advice.

Also, would hot air ventilate through the panels, and this air "restricted" with the foil sheeting?

In a old thread, I see Mr Naam speaking very highly of a large electric exhaust fan to ventilate the hot air in the ceiling, by memory during the hot part of the day, arguing that running a fan and lowering the temp up there allot is cheaper than many air cons working their guts out. [ my words, not his ]. This makes sense to me. Does any one have an example of on of these exhaust fans? I could put it on the back side of the house where no one sees it on the flat panel into the ceiling. I presume I would need some supports for it to be mounted on welded to the frame, not an issue at the moment.

Lastly, insulation, laying on the ceiling it self. I presume I will end up with 2-3 inch thick soft strand stuff that you buy in rolls at Global/Home Pro. I see there are some sealed silver bags, that I presume is full of the same stuff. By memory it was much more expensive, is it worth it to have the soft stand stuff sealed in these expensive bags? I should find out how the builder is going to attach the ceiling, if it is hanging, wouldn't be hard to install?

Two use full links from old threads for future reference.

http://www.thaivisa.com/forum/topic/371250-ceiling-insulation/

http://www.thaivisa.com/forum/topic/345779-roof-insulation/

[Naam]

We intend to have a gypsum ceiling, not the 60 x 60 squares hanging form the rafters. I am not sure how the builder intents to support the gypsum panels though to the horizontal beams across the roof.

i don't see any other way than a substructure with squares fixed to the roof structure.

Under the eves I am getting the panels that have many slits with a wire mesh over it to keep vermin out, this will be on the 4 sides.

that's normal.

On each end, we will have static horizontal vents on the flat section near the apex.

no idea what you are talking about.

the builder wants to put foil under the roof panels, how effective is thin foil ?

as effective as a drop in the ocean.

Is the foil with 2-5mm of white foam bought as rolls much more effective? The are much more expensive but I imagine would also help with noise form rain as well, maybe, need advice.

forget about it!

Also, would hot air ventilate through the panels, and this air "restricted" with the foil sheeting?

the answer is no, but even without anything attached the panels should be tight without letting hot air ventilate or rain seep in.

I see Mr Naam speaking very highly of a large electric exhaust fan to ventilate the hot air in the ceiling,

the fan doesn't have to be large but selected according to the area of your roof and (to a lesser extent) the volume of your attic.

by memory during the hot part of the day, arguing that running a fan and lowering the temp up there allot is cheaper than many air cons working their guts out. [ my words, not his ]. This makes sense to me.

correct

Does any one have an example of on of these exhaust fans?

specific roof fans for this purpose and mounted in a horizontal or flat roof exist but are very expensive. if you don't have a hip roof on all sides you can fix a fan in a vertical wall.

I could put it on the back side of the house where no one sees it on the flat panel into the ceiling. I presume I would need some supports for it to be mounted on welded to the frame, not an issue at the moment.

the issue will always be leakage if your builder is not familiar with the installation of a roof-mounted fan.

Lastly, insulation, laying on the ceiling it self. I presume I will end up with 2-3 inch thick soft strand stuff that you buy in rolls at Global/Home Pro. I see there are some sealed silver bags, that I presume is full of the same stuff. By memory it was much more expensive, is it worth it to have the soft stand stuff sealed in these expensive bags? I should find out how the builder is going to attach the ceiling, if it is hanging, wouldn't be hard to install?

any insulation is hard to install with the system used to hang gypsum ceilings in Thailand. ideal would be blow-in insulation which unfortunately is not available.

[mrbojangles]

the builder wants to put foil under the roof panels, how effective is thin foil ?

as effective as a drop in the ocean.

If used on it's own as the only insulating material, I would totally agree. However, if you do decide to use it as one of a combination of insulating materials, it should be fitted correctly. I.E. tape the joints together and not just overlap.

At the end of the day, IMO anything that can act as a barrier to reduce heat/cold going into the loft space, must be better than using nothing at all.

[travelmann]

the builder wants to put foil under the roof panels, how effective is thin foil ?

as effective as a drop in the ocean.

If used on it's own as the only insulating material, I would totally agree. However, if you do decide to use it as one of a combination of insulating materials, it should be fitted correctly. I.E. tape the joints together and not just overlap.

At the end of the day, IMO anything that can act as a barrier to reduce heat/cold going into the loft space, must be better than using nothing at all.

best roofs Ive seen are steel coated with foam stuck on the back or spray foam and painted white, cold to the touch in midday sun.....................ok I lie ambient temp ie 30c

bluescope steel asia a division of an OZ co.

[LennyW]

Best to have adequate airflow through your roofspace to avoid any condensation issues, i have heard of a few people having some problems with condensation when they have used the spray foam type insulation.

[katabeachbum]

Insulate the ceilings, vent the roof over ceilings. a proper thai style the roof is to steep for ordinary fans bearings. If not more than 8 meters between vertical walls in roof, vent is fine with 1 sqm in each end. use net to avoid birds

5mm foam works fine, covered with alu on upside. 10mm slightly better, double price pr sqm, so longer ROI. Read the insulation values for product in shop

spray foam is a disaster. humidity remains in steel structure

alu sheets/foil underneath tiles/asbest/steel roof sheets is a waste if ceiling is insulated, and can reduce airflow between roof and ceiling

edit. missd you are using 120x50 asbest, can be purchased foam insulated, used by most gas stations toilets. reduce attick heat at low cost, still insulate ceiling

[kokesaat]

We built our home (14 years ago) with 60x60cm gypsum suspended from the roof rafters. About two years after we had the house built, we had Homemart put in 4" thick (60cm wide) rolls of insulation. It made a world of difference. Then about 10 years after we had the house built, we removed the asbestos/cement tile roof panels (elephant brand, I think) and replaced the roof with a white steel roof that has the foam/foil backing. Between the two, our home is substantially (unscientific, but we have a few years experience with both) cooler and definitely much easier to cool than the way our home was originally built.

[wpcoe]

On each end, we will have static horizontal vents on the flat section near the apex.

no idea what you are talking about.

I think he is talking about "gable vents"

[edit: Hmmm. I just realized he said *horizontal,* so I'm confused now, as well...]

Edited November 22, 2011 by wpcoe

[katabeachbum]

We built our home (14 years ago) with 60x60cm gypsum suspended from the roof rafters. About two years after we had the house built, we had Homemart put in 4" thick (60cm wide) rolls of insulation. It made a world of difference. Then about 10 years after we had the house built, we removed the asbestos/cement tile roof panels (elephant brand, I think) and replaced the roof with a white steel roof that has the foam/foil backing. Between the two, our home is substantially (unscientific, but we have a few years experience with both) cooler and definitely much easier to cool than the way our home was originally built.

5mm foam rools have same insulation value as 3inches of fiberglass insulation, and its advantage is it can not suck/hold water

[haveaniceday]

Yes, I am putting Gabel Vents like the link above in near the apex of the ends.

Also going to put in a Venting exhaust fan on the back of the house to suck out hot air during the peak of the day.

[Naam]

the builder wants to put foil under the roof panels, how effective is thin foil ?

as effective as a drop in the ocean.

If used on it's own as the only insulating material, I would totally agree. However, if you do decide to use it as one of a combination of insulating materials, it should be fitted correctly. I.E. tape the joints together and not just overlap.

At the end of the day, IMO anything that can act as a barrier to reduce heat/cold going into the loft space, must be better than using nothing at all.

at the end of the day one has to consider that this barrier only delays the heating up of the attic space a teenie weenie little bit. in my [not so] humble opinion each and every Baht construction cost should be spent in a most efficient way and that applies especially to insulation.

moeover, i hesitate to draw anybody's attention to the shortcomings and negative effects of aluminium foil (aluminum for our American and Canadian friends) under any rooftiles because we'd then enter into an area of thermal physics which i hate to dicuss with laymen.

:jap:

[Naam]

Yes, I am putting Gabel Vents like the link above in near the apex of the ends.

Also going to put in a Venting exhaust fan on the back of the house to suck out hot air during the peak of the day.

using a "whole house fan" during the peak heat of the day means you are sucking hot air out of the house and hot air into the house which equals to a zero sum game minus the cost of energy! that kind of exhaust should be used during the coolest time of the day (early morning hours) when the ambient outside temperature is lower than not only the air temperature but also the temperature of floors and walls inside the house.

[JoePai]

Yes, I am putting Gabel Vents like the link above in near the apex of the ends.

Also going to put in a Venting exhaust fan on the back of the house to suck out hot air during the peak of the day.

using a "whole house fan" during the peak heat of the day means you are sucking hot air out of the house and hot air into the house which equals to a zero sum game minus the cost of energy! that kind of exhaust should be used during the coolest time of the day (early morning hours) when the ambient outside temperature is lower than not only the air temperature but also the temperature of floors and walls inside the house.

So are you saying during peak heat, the temperature in the roof space = that of the outside ?

[Naam]

Yes, I am putting Gabel Vents like the link above in near the apex of the ends.

Also going to put in a Venting exhaust fan on the back of the house to suck out hot air during the peak of the day.

using a "whole house fan" during the peak heat of the day means you are sucking hot air out of the house and hot air into the house which equals to a zero sum game minus the cost of energy! that kind of exhaust should be used during the coolest time of the day (early morning hours) when the ambient outside temperature is lower than not only the air temperature but also the temperature of floors and walls inside the house.

So are you saying during peak heat, the temperature in the roof space = that of the outside ?

we have to differentiate between a "whole house fan" which exhausts air from the inside of a house and an "attic fan" which exhausts air from the "roof space". two completely different animals which have completely different tasks. confusing is that the OP is mixing up the two.

the attic fan has to run continously during peak heat hours (12.00 - 17.00hrs) an hour around 20.00hrs and an hour in the early mornings. during peak heat the temperature of an unventilated attic can be more than double the ambient temperature. in my former Florida home i have measured attic temperatures in excess of 80º Celsius not Fahrenheit!

the whole house fan's efficiency is based on running it during the hours with the lowest outside temperature and that is most of the times in the early morning before the sun comes up. apart from this one runs it after heavy downpours which cool down the ambient temperature considerably. disadvantage is drawing a lot of humidity into the house.

in this context there is one more thing worthwhile to mention. advice to those who prefer a continous airconditioned environment and are not fans of cross ventilation:

-do not wait to use airconditioning till peak heat. the capacity of an aircon unit is highly dependant on the ambient temperature the outside unit uses to cool down the condenser coil for heat transfer. the rated capacity of a standard size unit (12,000 bth/h @ 32ºC) can jump to 18,000+ btu/h when the ambient temperature is 25-26º. it is therefore advisable to start cooling down the house as early as possible using the cool hours of the day.

[travelmann]

Insulate the ceilings, vent the roof over ceilings. a proper thai style the roof is to steep for ordinary fans bearings. If not more than 8 meters between vertical walls in roof, vent is fine with 1 sqm in each end. use net to avoid birds

5mm foam works fine, covered with alu on upside. 10mm slightly better, double price pr sqm, so longer ROI. Read the insulation values for product in shop

spray foam is a disaster. humidity remains in steel structure

alu sheets/foil underneath tiles/asbest/steel roof sheets is a waste if ceiling is insulated, and can reduce airflow between roof and ceiling

edit. missd you are using 120x50 asbest, can be purchased foam insulated, used by most gas stations toilets. reduce attick heat at low cost, still insulate ceiling

Please explain the spray foam and humidity problem more, how about open cell foam?

I have seen the stuff in Gas station toilet roofs its a thin foam shiny metal side down "glued" onto the steel roofs, how long will the glue last Ive seen this type of glue (contact adhesive) unstick itslef after a time

Edited November 29, 2011 by travelmann

[haveaniceday]

Yes, I had confused the Whole House fan and Attic fans.

I am using Attic exhaust fans, to help lower the temp up there. I am guessing it must get 45'c inside there, blowing some of that out, can only be a good thing.

Worth noting, I know next to nothing about this subject, so take what I am doing with a grain of salt

[katabeachbum]

Insulate the ceilings, vent the roof over ceilings. a proper thai style the roof is to steep for ordinary fans bearings. If not more than 8 meters between vertical walls in roof, vent is fine with 1 sqm in each end. use net to avoid birds

5mm foam works fine, covered with alu on upside. 10mm slightly better, double price pr sqm, so longer ROI. Read the insulation values for product in shop

spray foam is a disaster. humidity remains in steel structure

alu sheets/foil underneath tiles/asbest/steel roof sheets is a waste if ceiling is insulated, and can reduce airflow between roof and ceiling

edit. missd you are using 120x50 asbest, can be purchased foam insulated, used by most gas stations toilets. reduce attick heat at low cost, still insulate ceiling

Please explain the spray foam and humidity problem more, how about open cell foam?

I have seen the stuff in Gas station toilet roofs its a thin foam shiny metal side down "glued" onto the steel roofs, how long will the glue last Ive seen this type of glue (contact adhesive) unstick itslef after a time

spray foam underneath steel structure, leaks and condense will remain in steelstructure causing rust

never seen the insulation fall off asbest sheets, old Ptt toilets and 7eleven. would assume same lifetime as asbest sheets, 15-20 years

[JoePai]

Yes, I am putting Gabel Vents like the link above in near the apex of the ends.

Also going to put in a Venting exhaust fan on the back of the house to suck out hot air during the peak of the day.

using a "whole house fan" during the peak heat of the day means you are sucking hot air out of the house and hot air into the house which equals to a zero sum game minus the cost of energy! that kind of exhaust should be used during the coolest time of the day (early morning hours) when the ambient outside temperature is lower than not only the air temperature but also the temperature of floors and walls inside the house.

So are you saying during peak heat, the temperature in the roof space = that of the outside ?

we have to differentiate between a "whole house fan" which exhausts air from the inside of a house and an "attic fan" which exhausts air from the "roof space". two completely different animals which have completely different tasks. confusing is that the OP is mixing up the two.

the attic fan has to run continously during peak heat hours (12.00 - 17.00hrs) an hour around 20.00hrs and an hour in the early mornings. during peak heat the temperature of an unventilated attic can be more than double the ambient temperature. in my former Florida home i have measured attic temperatures in excess of 80º Celsius not Fahrenheit!

the whole house fan's efficiency is based on running it during the hours with the lowest outside temperature and that is most of the times in the early morning before the sun comes up. apart from this one runs it after heavy downpours which cool down the ambient temperature considerably. disadvantage is drawing a lot of humidity into the house.

in this context there is one more thing worthwhile to mention. advice to those who prefer a continous airconditioned environment and are not fans of cross ventilation:

-do not wait to use airconditioning till peak heat. the capacity of an aircon unit is highly dependant on the ambient temperature the outside unit uses to cool down the condenser coil for heat transfer. the rated capacity of a standard size unit (12,000 bth/h @ 32ºC) can jump to 18,000+ btu/h when the ambient temperature is 25-26º. it is therefore advisable to start cooling down the house as early as possible using the cool hours of the day.

Thank you for clarifying the point about the Attic fan. Now all I need is to try and find a supplier of a large diameter fan (I have space for one 1m in dia !) but with a slow(ish) speed !

[Naam]

Thank you for clarifying the point about the Attic fan. Now all I need is to try and find a supplier of a large diameter fan (I have space for one 1m in dia !) but with a slow(ish) speed !

if you want to ventilate your attic there is no need for a fan with that diameter. what you need is constant low noise airflow which can be achieved with one or an array of several much smaller fans, individually switchable manually or by timers. fans with this diameter do of course exist, i use a 90cm Ø but as a whole house fan.

there's a company in BKK which specialises in all kinds of direct and belt-driven fans from which i got my roof-mounted attic fan and the whole-house fan. if you need additional assistance don't hesitate to ask in this thread.

[Naam]

my whole-house fan, mounted in a special way (was breaking my head for several days to find a way) as my home has four hip roofs:

[JoePai]

Thank you for clarifying the point about the Attic fan. Now all I need is to try and find a supplier of a large diameter fan (I have space for one 1m in dia !) but with a slow(ish) speed !

if you want to ventilate your attic there is no need for a fan with that diameter. what you need is constant low noise airflow which can be achieved with one or an array of several much smaller fans, individually switchable manually or by timers. fans with this diameter do of course exist, i use a 90cm Ø but as a whole house fan.

there's a company in BKK which specialises in all kinds of direct and belt-driven fans from which i got my roof-mounted attic fan and the whole-house fan. if you need additional assistance don't hesitate to ask in this thread.

Thank you very much for this invaluable information. If you don't mind me asking one more question, for an average 3 bed single level house, what size fan and speed would you suggest ?

[travelmann]

Insulate the ceilings, vent the roof over ceilings. a proper thai style the roof is to steep for ordinary fans bearings. If not more than 8 meters between vertical walls in roof, vent is fine with 1 sqm in each end. use net to avoid birds

5mm foam works fine, covered with alu on upside. 10mm slightly better, double price pr sqm, so longer ROI. Read the insulation values for product in shop

spray foam is a disaster. humidity remains in steel structure

alu sheets/foil underneath tiles/asbest/steel roof sheets is a waste if ceiling is insulated, and can reduce airflow between roof and ceiling

edit. missd you are using 120x50 asbest, can be purchased foam insulated, used by most gas stations toilets. reduce attick heat at low cost, still insulate ceiling

Please explain the spray foam and humidity problem more, how about open cell foam?

I have seen the stuff in Gas station toilet roofs its a thin foam shiny metal side down "glued" onto the steel roofs, how long will the glue last Ive seen this type of glue (contact adhesive) unstick itslef after a time

spray foam underneath steel structure, leaks and condense will remain in steelstructure causing rust

never seen the insulation fall off asbest sheets, old Ptt toilets and 7eleven. would assume same lifetime as asbest sheets, 15-20 years

Hi Ok but there arent massive temp differentials here in the tropics as in northern hemisphere and I am thinking of Clorbond steel roofing with spray foam under it not asbestos and then fibreglass on top of the gypsum board ceilings with the attic space also vented as I do want air con in the rooms.

The colorbond sheet will be continuous with the clips that hold it on NOT bolts so no bolt holes will be cut thru the sheet the chance of any leaks will be almost zero.

[JoePai]

Insulate the ceilings, vent the roof over ceilings. a proper thai style the roof is to steep for ordinary fans bearings. If not more than 8 meters between vertical walls in roof, vent is fine with 1 sqm in each end. use net to avoid birds

5mm foam works fine, covered with alu on upside. 10mm slightly better, double price pr sqm, so longer ROI. Read the insulation values for product in shop

spray foam is a disaster. humidity remains in steel structure

alu sheets/foil underneath tiles/asbest/steel roof sheets is a waste if ceiling is insulated, and can reduce airflow between roof and ceiling

edit. missd you are using 120x50 asbest, can be purchased foam insulated, used by most gas stations toilets. reduce attick heat at low cost, still insulate ceiling

Please explain the spray foam and humidity problem more, how about open cell foam?

I have seen the stuff in Gas station toilet roofs its a thin foam shiny metal side down "glued" onto the steel roofs, how long will the glue last Ive seen this type of glue (contact adhesive) unstick itslef after a time

spray foam underneath steel structure, leaks and condense will remain in steelstructure causing rust

never seen the insulation fall off asbest sheets, old Ptt toilets and 7eleven. would assume same lifetime as asbest sheets, 15-20 years

Hi Ok but there arent massive temp differentials here in the tropics as in northern hemisphere and I am thinking of Clorbond steel roofing with spray foam under it not asbestos and then fibreglass on top of the gypsum board ceilings with the attic space also vented as I do want air con in the rooms.

The colorbond sheet will be continuous with the clips that hold it on NOT bolts so no bolt holes will be cut thru the sheet the chance of any leaks will be almost zero.

Sounds like the perfect roofing solution for Thailand !

[Thighlander]

I would be looking at the foam for insulation. It was 48c last Summer and I had real good luck with my attic fan with 1/8 horsepower motor. The turbines are good, too, but let in a little more noise.

[Naam]

Thank you for clarifying the point about the Attic fan. Now all I need is to try and find a supplier of a large diameter fan (I have space for one 1m in dia !) but with a slow(ish) speed !

if you want to ventilate your attic there is no need for a fan with that diameter. what you need is constant low noise airflow which can be achieved with one or an array of several much smaller fans, individually switchable manually or by timers. fans with this diameter do of course exist, i use a 90cm Ø but as a whole house fan.

there's a company in BKK which specialises in all kinds of direct and belt-driven fans from which i got my roof-mounted attic fan and the whole-house fan. if you need additional assistance don't hesitate to ask in this thread.

Thank you very much for this invaluable information. If you don't mind me asking one more question, for an average 3 bed single level house, what size fan and speed would you suggest ?

this is your lucky day Joe! it's weekend, i am sipping my first glass of port and forgive sinners who ask questions like you

rule of thumb: exchange of air volume twice per hour (three times is better). let's assume your house/attic has a footprint of 200m² and a roof slope of 45º (most slopes are less) we are looking at 300m³ = 600m³/h = 10m³/m (~350 cfm), internationally most small fans are still rated "cfm" (cubic feet per minute). to be on the safe side and shooting from the hip i'd say a fan drawing 180-200 watts (approximately 1/4 HP) should be sufficient assuming you are able to place the fan high up.

[samran]

Thank you for clarifying the point about the Attic fan. Now all I need is to try and find a supplier of a large diameter fan (I have space for one 1m in dia !) but with a slow(ish) speed !

if you want to ventilate your attic there is no need for a fan with that diameter. what you need is constant low noise airflow which can be achieved with one or an array of several much smaller fans, individually switchable manually or by timers. fans with this diameter do of course exist, i use a 90cm Ø but as a whole house fan.

there's a company in BKK which specialises in all kinds of direct and belt-driven fans from which i got my roof-mounted attic fan and the whole-house fan. if you need additional assistance don't hesitate to ask in this thread.

Thank you very much for this invaluable information. If you don't mind me asking one more question, for an average 3 bed single level house, what size fan and speed would you suggest ?

this is your lucky day Joe! it's weekend, i am sipping my first glass of port and forgive sinners who ask questions like you

rule of thumb: exchange of air volume twice per hour (three times is better). let's assume your house/attic has a footprint of 200m² and a roof slope of 45º (most slopes are less) we are looking at 300m³ = 600m³/h = 10m³/m (~350 cfm), internationally most small fans are still rated "cfm" (cubic feet per minute). to be on the safe side and shooting from the hip i'd say a fan drawing 180-200 watts (approximately 1/4 HP) should be sufficient assuming you are able to place the fan high up.

How does that change though if that fan is travelling from the east at 25km/h and a train which is travelling from the opposite direction is travelling at 30km/h with a incline grade of 1.5 degrees?

Sorry, couldn't help myself. 555

[katabeachbum]

Hi Ok but there arent massive temp differentials here in the tropics as in northern hemisphere and I am thinking of Clorbond steel roofing with spray foam under it not asbestos and then fibreglass on top of the gypsum board ceilings with the attic space also vented as I do want air con in the rooms.

The colorbond sheet will be continuous with the clips that hold it on NOT bolts so no bolt holes will be cut thru the sheet the chance of any leaks will be almost zero.

well, here close to the beach, watertanks in stainless steel dont last 5 years, so a steel roof would be my last choice

[Naam]

How does that change though if that fan is travelling from the east at 25km/h and a train which is travelling from the opposite direction is travelling at 30km/h with a incline grade of 1.5 degrees?

Sorry, couldn't help myself. 555

the change is highly dependent on the average price of Chang in a radius of 1.79 kilometers, i.e. if Chang is served for less than 50 Baht/bottle the attic fan will use 0.33 megapixels less electric energy per 100 linear meters as the crow flies. should some bars in the vicinity exist which charge in excess of 100 Baht/bottle (because their coyote dancers are stark nekkid when dancing) the fan will use additional 71 kilobytes per 100m³ exhausted hot air.

it is therefore highly suggested that -based on the afore-mentioned factors- a survey is conducted and a feasibility study made in order to select the appropriate attic fan.

[JoePai]

Thank you for clarifying the point about the Attic fan. Now all I need is to try and find a supplier of a large diameter fan (I have space for one 1m in dia !) but with a slow(ish) speed !

if you want to ventilate your attic there is no need for a fan with that diameter. what you need is constant low noise airflow which can be achieved with one or an array of several much smaller fans, individually switchable manually or by timers. fans with this diameter do of course exist, i use a 90cm Ø but as a whole house fan.

there's a company in BKK which specialises in all kinds of direct and belt-driven fans from which i got my roof-mounted attic fan and the whole-house fan. if you need additional assistance don't hesitate to ask in this thread.

Thank you very much for this invaluable information. If you don't mind me asking one more question, for an average 3 bed single level house, what size fan and speed would you suggest ?

this is your lucky day Joe! it's weekend, i am sipping my first glass of port and forgive sinners who ask questions like you

rule of thumb: exchange of air volume twice per hour (three times is better). let's assume your house/attic has a footprint of 200m² and a roof slope of 45º (most slopes are less) we are looking at 300m³ = 600m³/h = 10m³/m (~350 cfm), internationally most small fans are still rated "cfm" (cubic feet per minute). to be on the safe side and shooting from the hip i'd say a fan drawing 180-200 watts (approximately 1/4 HP) should be sufficient assuming you are able to place the fan high up.

From a humble sinner - thank you :jap:

[Naam]

Joe,

if you need additional assistance give me some specific information such as one (or more) sketch(es). a picture says more than a thousand words!

by the way, my consulting fees are affordable. for every 20 hours i am putting in a simple "thank you" will suffice.