What is the cheapest method of dehumidifying a room, long-term?

[luk AJ]

Is mentioned in previous posts IMO only dehumidifier will really work if you want to bring relative moisture down. An airco will extract moisture but because temp. goes down relative humidity will remain the same.

[Tapster]

I'll post when I have some results with the silica gel.

We have a separate workshop building which i want to dehumidify. We don't go in there every day and the ventilation is not that great. There are two aircon units, but I'll see how the silica gel works before resorting to them.

It'll cost me 2000 THB to buy 10kg of silica gel and see how this works in the space. I'll monitor the humidity.

Don't hold your breath..............it'll be a week or three!

Cheers!

[questionsreplies]

There is no cheap good solution, so why not just forget it and use airvon or buy a bungalow instead of a full house?

[speedtripler]

I think industrial chemicals sounds like more hassle than its worth tbh

Buying 25kg bags of powder to put into pots to take moisture from the air and then you have to find some way to see you out the chemical again so you can hopefully reuse it

Seems like a lot of physical activity and extra time unless you enjoy doing that sort of thing

To solve it I installed a modern efficient a/c system and when I'm leaving during the day I leave windows and doors and balcony open etc so natural wind and sunlight blows through the house, this will prevent any excess humidity being around long enough to turn into mould and it doesn't cost a lot either

I have two 18" industrial grade fans that are a bit better than domestic models but on the highest setting its like hearing a helicopter coming in the distance so I only use those on full speed during the day when it's hot and Im cleaning up or listen to music etc

[lopburi3]

To solve it I installed a modern efficient a/c system and when I'm leaving during the day I leave windows and doors and balcony open

Suspect for most readers that would be a plan for disaster - it does occasionally rain here; and winds can often blow that rain into house if windows remain open. Not to mention some peoples material things might attract visitors.

((suspect you have someone in house during this time - but you did not mention it))

[Tapster]

Having just moved from Johannesburg (crime capital of South Africa), there's no way we'd leave our windows open!

Phuket is a security paradise compared with SA but we's be asking for it to leave the windows open.

Anyway, my experiment is nearly ready to begin.

10kg of silica gel has arrived. I'm just waiting for the humidity meter from Lazada, the delivery of which is unusually slow.

I'll post again when things progress.

[Tapster]

You are not the only resident - consider the effects on all.

Exactly!

That's why silica gel is the way forward.

It's very safe anyway and I'll cover the containers in some sort of mesh to stop our cats trying to eat it.

[steven100]

yes, you may have to relocate to a less humid region ...

[Tapster]

Hello everyone!

Apologies for the long delay....two months!

However, a lot has happened, particularly a flood which made humidity issues pale into insignificance!

Anyway, here are my thoughts and findings (in no particular order) regarding dehumidifying a room-sized space in Phuket:

• About humidity and mold growth in general, I did some research both by reading and by using my two electronic humidity meters.
  
  A relative humidity (RH) level of 40-65% is generally considered to be a comfortable and healthy room climate.
  
  Relative humidity levels consistently above 70% are required for mold growth, except possibly in some areas of a room which for a specific reason attract or hold excess moisture. These latter areas may support mold growth when the average RH is below 70%.
  
  RH varies with temperature. In a room where the temperature rises, the RH will fall and when a room becomes colder the RH will rise.............thus, at night there is a good chance of RH levels being high enough to support mold growth, even if the room has been dehumidified during the day. This is worth remembering.
  
  Mold grows better on organic surfaces (cloth, leather, dust) so furniture and material choices can influence its growth.
  
  Porous wall paints/coverings are best as they will allow a moisture "pressure gradient" in the walls and so long as this gradient is in the right direction, it will reduce humidity.
  
  There's a lot of material available on the Internet about these issues. A good overview is available on these links:
  
  http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/relhum.html#c1
  
  http://www.inoutic.de/en/tips-on-window-purchase/ventilation/humidity-and-mould/luftfeuchtigkeit-schimmelpilzbildung.html
  
  http://www.fsec.ucf.edu/en/consumer/buildings/basics/moldgrowth.htm
  
• Any form of desiccant (silica gel, calcium chloride and others https://en.wikipedia.org/wiki/Desiccant)
  is wholly inadequate to dehumidify a room!
  
  The difference between the ability of any desiccant to lower the local RH and the amount of moisture contained in a room is so many orders of magnitude apart that the amount of desiccant necessary to make an appreciable difference is financially and physically impracticable.
  
  My experiments showed that 1kg of colour-changing silica gel, spread thinly in a tray, would be used up in less than 24 hours and would make no difference to the measured RH in the room. The room I used was a very small store room, no more than 4-5 cubic metres. The room was closed with the only ventilation coming from underneath the door.
  
  
• In conclusion, I've been using our air conditioners on "dry" setting to reduce RH and it has been very successful and hasn't significantly added to our electricity bill.
  
  Also, ceiling fans help to move air, helping the aircon to dehumidify all the air in a room and, where aircon isn't being used, the fans create air movement, therefore promote evaporation of surface moisture and help to stop mold developing.
  
  Of course, some people will prefer simply to leave all the windows open and this may be effective where there's a breeze, however it won't reduce the RH to below the outdoor RH so I've chosen not to follow that route.
  
  I'm sure there are some other factors that I've not covered but I think that these are the main concerns in RH/mold growth in rooms.
  
  
  
  

[blackcab]

I never understood the adversion to using the air-con. I live in a 1250 sq. foot house (sorry, I can't be bothered to convert that to sq. meter), and I run two a/c units 24x7. The cost is about 2000 baht per month, which is not that bad. My place stays dry, I stay dry, and I'm happy.

116 sqm.

[trogers]

Buy a 5kg bag of cheap broken rice. Spread the rice on 1-inch thick trays and place them where outside air flows in.

Change the rice once a week...

You can also recycle the damp rice by drying under the sun.

Edited October 8, 2015 by trogers

[Tapster]

Buy a 5kg bag of cheap broken rice. Spread the rice on 1-inch thick trays and place them where outside air flows in.

Change the rice once a week...

You can also recycle the damp rice by drying under the sun.

According to my results, you might as well not bother with rice to reduce humidity.

Dedicated desiccants make no difference to the humidity in a room so rice hasn't got a chance.

It's science! I've done the measurements.

[trogers]

Buy a 5kg bag of cheap broken rice. Spread the rice on 1-inch thick trays and place them where outside air flows in.

Change the rice once a week...

You can also recycle the damp rice by drying under the sun.

According to my results, you might as well not bother with rice to reduce humidity.

Dedicated desiccants make no difference to the humidity in a room so rice hasn't got a chance.

It's science! I've done the measurements.

Why does placing rice in salt shakers prevent salt from getting moist and lumpy?

[lopburi3]

Because it is a confined container without airflow. Just as it works in a cake tin or a bag/box of something - it does not work where new moister is available in any measurable amount.

[trogers]

Because it is a confined container without airflow. Just as it works in a cake tin or a bag/box of something - it does not work where new moister is available in any measurable amount.

So it may work in an enclosed room with enough rice trays and a ceiling fan turned on for a week or so...

[KittenKong]

I run my air-con all day every day, apart from a month or two in Dec-Feb when the humidity drops.

I do this mostly to reduce humidity, and also to keep the temperature around 27-28 degrees.

I manage to keep my entire condo entirely mould-free and my monthly electricity bill is generally around 1500B.

[trogers]

I run my air-con all day every day, apart from a month or two in Dec-Feb when the humidity drops.

I do this mostly to reduce humidity, and also to keep the temperature around 27-28 degrees.

I manage to keep my entire condo entirely mould-free and my monthly electricity bill is generally around 1500B.

And the floor size of the air-con space is...

[Naam]

I run my air-con all day every day, apart from a month or two in Dec-Feb when the humidity drops.

I do this mostly to reduce humidity, and also to keep the temperature around 27-28 degrees.

I manage to keep my entire condo entirely mould-free and my monthly electricity bill is generally around 1500B.

And the floor size of the air-con space is...

my guess = 32-36m²

[1BADDAT]

Because it is a confined container without airflow. Just as it works in a cake tin or a bag/box of something - it does not work where new moister is available in any measurable amount.

So it may work in an enclosed room with enough rice trays and a ceiling fan turned on for a week or so...

it may work if you put 1 meter of rice covering the entire floor and make sure to keep it rotated. Does this seem like a practical solution? Why not do the obvious and just use the air conditioner which the OP finally concluded was the best option?

Do you live your entire life this way? Gasoline is expensive....I think I will push my motorbike to the market...lol

[KittenKong]

I run my air-con all day every day, apart from a month or two in Dec-Feb when the humidity drops.

I do this mostly to reduce humidity, and also to keep the temperature around 27-28 degrees.

I manage to keep my entire condo entirely mould-free and my monthly electricity bill is generally around 1500B.

And the floor size of the air-con space is...

Just over 60sqm. It's a large studio with one 24kw inverter air-con which only runs on the lowest fan setting. I also have two ceiling fans running constantly on the lowest setting.

[Craig krup]

There's a very quick calculation that will tell you that using something absorbent for a room is about as likely to work as bailing out the Titanic with a teaspoon. If we're talking about 17g per cubic meter then 90 cubic meters has (I think) a liter and a half of water in it, so with air change you're pis**** in the wind.