Extraction Fan - with a difference

[Bogbrush]

I recall sometime back I read an article on this forum regarding fans in the ceiling cavity to remove hot air. I was talking to a local architect the other day who advised me to rather look at putting an extraction fan in the house wall as opposed to the ceiling. “Turn off the air-conditioner, and put it on for half an hour or so at night and it will bring down the room temperature considerably, bringing relatively cold air in from outside.”

He stated he has bought such a fan before at Home Pro but all the ones I have seen are for pulling air out of a room/toilet rather than bringing air in; reversing the fan doesn’t appear to be a sensible option due to the ascetics of it being mounted back to front. Giving mozzies an entry point is also a concern..

Any suggestions as to make/brand, please?

[bankruatsteve]

I just don't see any practical purpose for extraction fans in a tropical climate.  Some of the large Home places and stores will have huge extraction fans at the top of the building.  They don't do a bit of good IMO.  

[gamb00ler]

3 minutes ago, bankruatsteve said:

I just don't see any practical purpose for extraction fans in a tropical climate.  Some of the large Home places and stores will have huge extraction fans at the top of the building.  They don't do a bit of good IMO.  

Those fans help to suck you in.

[Bogbrush]

My point centres around the fact that in our tropical climate the air at night generally is cooler outside than the captured hot air inside, and a suitable fan could suck cold air in and bring down the temperature without having to use an air-conditioner. 

If however you feel it won’t work then I’ll accept your advice.

[sometimewoodworker]

11 minutes ago, bankruatsteve said:

I just don't see any practical purpose for extraction fans in a tropical climate.  Some of the large Home places and stores will have huge extraction fans at the top of the building.  They don't do a bit of good IMO.  

You haven’t seen the huge wall of numbers of enormous fans, tens of meters high and wide in the DoHome stores? They seem to do a good job.

[KannikaP]

6 minutes ago, sometimewoodworker said:

You haven’t seen the huge wall of numbers of enormous fans, tens of meters high and wide in the DoHome stores? They seem to do a good job.

A ten metre high fan would probably shift my house!   LOL

[KannikaP]

I think the main thing is to create an airflow through the room. I put an extractor fan in my roof space, and then held a coloured smoke generator up to the soffit vents. I could see the air being drawn in, and out via the fan. 

I also fitted two 22 inch whirlybirds in my roof, Bht 23000 fitted. They made no difference at all except to my bank balance

[lopburi3]

17 minutes ago, Bogbrush said:

My point centres around the fact that in our tropical climate the air at night generally is cooler outside than the captured hot air inside, and a suitable fan could suck cold air in and bring down the temperature without having to use an air-conditioner. 

If however you feel it won’t work then I’ll accept your advice.

Unless you are living on a mountain the cooling off is marginal at best - that is why people use air conditioning.  In our home countries such systems do work - but not likely here.  And they work by pulling in air from ground floor and exit air above house (through roof).  Here most of the year you would be creating a wet/hot sauna.  Exhaust fans are used to remove smells.  You seal and remove moisture/lower temp for cooling.  What you can do is install fans to help reduce the amount of cooling required.  And if you want to use wall just use normal extraction fan and open air source on other side or room - but I do not believe you will find it helps to cool much.

[bankruatsteve]

16 minutes ago, sometimewoodworker said:

You haven’t seen the huge wall of numbers of enormous fans, tens of meters high and wide in the DoHome stores? They seem to do a good job.

Actually, Do Home is what first came to mind.  They move the air but I still sweat like a race horse.  At night, just open windows and let natural ventilation take its course.  But, I need my AC in this humidity.

[Muhendis]

There is a fan which can operate in both directions made by Panasonic (FV-25RLT2) however it is more efficient at ventilating than blowing air into a room. As has been said already having a ventilation fan is probably as good as you need because for every cubic metre ventilated to the outside there must be another sucked in.

[tifino]

11 minutes ago, Muhendis said:

There is a fan which can operate in both directions made by Panasonic (FV-25RLT2) however it is more efficient at ventilating than blowing air into a room. As has been said already having a ventilation fan is probably as good as you need because for every cubic metre ventilated to the outside there must be another sucked in.

given all the online advertising which mentions the so called In/Out capabilty - all one needs to do is look closely at the Pitch/shape of the blades, to show it is really only just an Extractor. The inefficiency of running those blades in reverse would be abysmal... 

I wonder how 'loud' the Flaps are when Shutting/Opening too? the noisy slapping of plastic flaps actioning, will wake the geckos!! 

[gamb00ler]

In the tropics I would only use an exhaust fan in an enclosed garage or similar type room that is not normally air-conditioned or occupied.  Even then, I'm not certain that there is that much benefit achievable.  There is an average of about a 13℃ differential from daytime high to night time low.  However if the enclosed space is not shaded there is potentially a larger differential due to daytime solar absorption.   Of course a garage also has typically extra heat from recently operated cars.

[ThailandRyan]

32 minutes ago, KannikaP said:

I think the main thing is to create an airflow through the room. I put an extractor fan in my roof space, and then held a coloured smoke generator up to the soffit vents. I could see the air being drawn in, and out via the fan. 

I also fitted two 22 inch whirlybirds in my roof, Bht 23000 fitted. They made no difference at all except to my bank balance

Whole house fan works in the states, but they wont work here unless you live in the north where it gets cooler at night.  On top of that who wants the darned PM 2.5 cruddy air being pulled into the house.

[JetsetBkk]

3 hours ago, lopburi3 said:

Unless you are living on a mountain the cooling off is marginal at best - that is why people use air conditioning.  In our home countries such systems do work - but not likely here.  And they work by pulling in air from ground floor and exit air above house (through roof).  Here most of the year you would be creating a wet/hot sauna.  Exhaust fans are used to remove smells.  You seal and remove moisture/lower temp for cooling.  What you can do is install fans to help reduce the amount of cooling required.  And if you want to use wall just use normal extraction fan and open air source on other side or room - but I do not believe you will find it helps to cool much.

I live in Phuket and not near a mountain. I have fitted an extractor fan in one bathroom against the bug screen of the window. It keeps the humidity down and cools the room. At this time of year, when the house is at 89F and the air outside is at 85F, there is not much cooling, but the humidity is reduced. But at other times of the year I can feel the cool air flowing down from the window where the extractor is pushing out the hot humid air.

I also have two identical fans mounted against the bug screens of the kitchen windows to remove heat from the oven and smell.

For some reason, the forum does not allow me to upload a picture.

 

[lopburi3]

18 minutes ago, JetsetBkk said:

It keeps the humidity down and cools the room.

Only because you added hot humidity with a shower.  It is not going to lower humidity in normal rooms, or the temp, below current outside temp.  But as not noted airflow will give the sensation of coolness even when the temp is the same.

[Pogust]

I rented a house with a wall vent fan in bedroom a few years ago. It does cool down a little during night. Of course not like A/C but in some situations it can reduce temp enough so you don't need A/C. It all depends on the local situation. I had a mosquito screen in window and fan in wall beside it. Turned fan on at sunset when temps drop and room was cool enough at bedtime. This was during winter Rayong area, in April it would probably not be enough.

 

[Daffy D]

Just a thought:-

If you fit a bathroom extractor fan be sure to have a louver panel door to allow air in for the fan to extract or it won't work efficiently and suck up air from the drains 

 

 

 

[Muhendis]

2 minutes ago, Daffy D said:

Just a thought:-

If you fit a bathroom extractor fan be sure to have a louver panel door to allow air in for the fan to extract or it won't work efficiently and suck up air from the drains 

 

 

 

Air won't be sucked in from the drains because all drains in Thailand have a water trap..........Don't they? 

[Daffy D]

1 minute ago, Muhendis said:

Air won't be sucked in from the drains because all drains in Thailand have a water trap..........Don't they? 

If you have been reading posts on here long enough you will have realized that in many ways Thailand is different from the rest of the known universe. 

Amongst other things Thailand has special electricity not found anywhere else and the idea of drain traps is a silly Farang notion totally unnecessary here in Thailand.

????

[JetsetBkk]

1 hour ago, Muhendis said:

Air won't be sucked in from the drains because all drains in Thailand have a water trap..........Don't they? 

Good one! ???? 

My bathroom sometimes used to stink of septic tank smell until I cleaned the drain outlets that have a small water trap built into them.

[JetsetBkk]

2 hours ago, Pogust said:

I rented a house with a wall vent fan in bedroom a few years ago. It does cool down a little during night. Of course not like A/C but in some situations it can reduce temp enough so you don't need A/C. It all depends on the local situation. I had a mosquito screen in window and fan in wall beside it. Turned fan on at sunset when temps drop and room was cool enough at bedtime. This was during winter Rayong area, in April it would probably not be enough.

I did a test. I put a thermometer against the window next to the extractor fan. 4 hours later the temperature was 87F. I switched on the extractor and had my shower. The temperature had dropped to 84F

But the fan made no difference this morning - 86F before and after showering - probably because the outside air temp was rising.

[ballpoint]

I use a large diesel powered one that I got off an old Massey Ferguson.  It's an ex-tractor fan.

(Perfect for blowing the tumble weed around while I get my coat).

[Muhendis]

8 hours ago, Daffy D said:

Amongst other things Thailand has special electricity not found anywhere else and the idea of drain traps is a silly Farang notion totally unnecessary here in Thailand.

So true.

[Bogbrush]

As the OP, I would like to thank everyone who commented, presented ideas and related experiences. It is refreshing to get away from the sink hole that the general forum ferments in, and it is pleasant and gratifying to meet members who are more than willing to share their successes and disappointments in this small but particular field of internal cooling. Luckily the conversation didn’t shift to the benefits of roof cavity extraction which I believe is far more complicated and intricate.

Once again thanks for the sincerity of your replies and the openness of your failures. I feel my future in S Phuket will be driven by an overhead fan, a 16”” remote wall swinger pitched high in a corner, supplemented by a few short blasts at 1700, 1900 and 2100hrs on the trusty aircon.

To the king across the ocean..????

 

[tweedledee2]

Thai Watsadu sells industrial fan units that can be mounted in a wall or window. The motor can be wired to turn the fan in either direction.