Best passive cooling strategies to cater for hot humid days 40-45C without wind?

[4myr]

I am a newbie wrt to building houses. Want to have Thai developer build a house in Tak [one of the hottest provinces] on black soil area [not the granite area] on elevated land.

I cannot stand using AC, therefore I prefer to use none or at most ceiling fans with as much cross ventilation as possible. Sofar I survived living in Chiang mai and Ko Chang without AC.

 

However there are days of 40-45C during the 2-3 hot months of the year whereby there is no wind. What are then the best passive cooling strategies, assuming as much heat reflection and insulation is applied to low thermal mass roof & walls and external shading or roof overhang is applied to windows.

 

From various online sources I have gathered below strategies. 

 

I would like your response, whether they will work or have been succesfully applied in a hot/humid climate like Thailand:

 

1) use the high thermal mass of the colder soil conducted thru the cement/concrete slab. Have a cold floor like granito or tiles. 

2) lower the base floor of some rooms to increase the surface with the cold soil thermal mass [applicable only on elevated land]

3) create cold air inlet thru earthship design principle like air tubes buried under the soil under some slight elevation, with a condensation collection point where the warm outside air is coming into the tube thru a cylindrical chimney post. The tubes are coming inside the house and colder air spread to rooms frequently habited

4) create an air draft in the house thru a long glass trombe wall chimney [see pic] or a simple black solar cylinder chimney, whereby along the chimney surface the air is heated by the sun to create the air draft. 

 

 

[bankruatsteve]

8 minutes ago, 4myr said:

I would like your response, whether they will work or have been succesfully applied in a hot/humid climate like Thailand:

No and No.  Some might claim they have but I would doubt it.

[ourmanflint]

Whichever solution you try, I would say the most important one is keeping your home out of direct sunlight, so option 4 is definitely a no go. I am planning on using shade trees on our plot in Phrae, just to break the effect of having constant sun on the roof.

 

[johng]

Put as many solar panels as possible on the roof to run a few aircons during the "hot times"

[phetphet]

You might also want to consider either tinted, or spectrally selective film installed on windows to reduce solar gain.

 

There was a poster that build a passive house house here with a system where air was drawn through underground pipes to cool using lower temp of soil, then passed over a heat exchange to cool the inside air. I have looked, but can't find the thread.

 

Have a look at this. A long read:   https://ecohousethailand.com

Edited October 7, 2020 by phetphet

[sometimewoodworker]

4 hours ago, phetphet said:

There was a poster that build a passive house house here with a system where air was drawn through underground pipes to cool using lower temp of soil, then passed over a heat exchange to cool the inside air. I have looked, but can't find the thread.

I think you will find that the underground pipe collapsed.

[ourmanflint]

An underground rainwater harvesting cistern, would be a much better heat sink than earth type, plus keep all of your freshwater cool and simplify plumbing immeasurably 

[onebir]

Bamboo mats (like this) make sleeping a lot easier without aircon.

[Laza 45]

What has worked for me is cavity walls.. insulating block on the outside.. conventional concrete on the inside.. verandas shading sunny walls from direct sun.. solar reflective glass in windows.. good ventilation from roof space.. insulation under roofing and above ceiling..  In hot weather I open windows at night to allow the rooms to cool down to night time temperature .. I close them when the day starts to warm up.. stays reasonably cool all day.  If combined with passive systems you have mentioned you should have a comfortable house.. good luck..

[weedywhaoo]

Nummer 3 will not work. First the earth temperature is much higher than the 55 degrees shown in your post.

The most important reason not to use this idea is mold and fungus. Due to condensation in the pipe, it will grow mold and fungus in the pipe. You are then literally poisoning the house with that air. I would never use this concept if you are concerned about health.

[Crossy]

Plants, plants and more plants.

 

When correctly positioned they provide shading so the walls don't heat up excessively, but they also provide natural evaporative cooling when they transpire water from their roots out of the leaves.

 

They look nice too ???? 

 

https://www.osti.gov/servlets/purl/5450077

https://www.bobvila.com/articles/54-quick-tip-your-plants-can-cool-your-house/

https://www.epa.gov/heatislands/using-trees-and-vegetation-reduce-heat-islands

[KarenBravo]

10 hours ago, sometimewoodworker said:

I think you will find that the underground pipe collapsed.

Also an open invitation for snakes and rats.

[bbudd]

Plant shade trees NOW=something fast growing like tagop.

Choose a method of shading the south walls,like bigger eaves or an outer wall,Even shade cloth will help

Be sure theres adequate roof ventilation and attic insulation

A water sprinkler on the roof for those real hot days will reduce inside temp by 5" or more.Helps to wet the walls as well

An evaporator fan cools but adds water vapor-sort of a trade off to my mind

 

These methods got us thru all but 2 days of the last hot season

[steven100]

I would install a couple of rooftop ventilation fans : 

 

 

I would look at a rooftop ducted aircooling system :

 

[sometimewoodworker]

18 minutes ago, KarenBravo said:

10 hours ago, sometimewoodworker said:

I think you will find that the underground pipe collapsed.

Also an open invitation for snakes and rats.

No, as the air would have gone through a heat/humidity transfer unit not into the house so no access for to any wildlife.

[mikesil]

Trees, man, trees.  Large trees with broad, dark green leaves.  Don't let the builder knock any of them down. Build the house under overhanging branches with as much foliage and shade around the house as possible.

 

It's the only method that I have seen work here in the high humidity LOS.  Visiting a friend, I feel a 10 deg drop (estimated) when i walk onto his property. 

[carlyai]

We had success with the Pattaya house installing that spray insulation all through the roof cavity. Long time ago, still cool in the house.

I would built provision for airconditioner, build in the power cables.

3 months is a long time hot and if you need to be cooler, or go berserk then just throw in an aircon unit as power etc already there.

[StevieAus]

1 hour ago, Laza 45 said:

What has worked for me is cavity walls.. insulating block on the outside.. conventional concrete on the inside.. verandas shading sunny walls from direct sun.. solar reflective glass in windows.. good ventilation from roof space.. insulation under roofing and above ceiling..  In hot weather I open windows at night to allow the rooms to cool down to night time temperature .. I close them when the day starts to warm up.. stays reasonably cool all day.  If combined with passive systems you have mentioned you should have a comfortable house.. good luck..

I am no builder but your suggestions seem the most practical I know two people here who have built homes with cavity walls and the difference in temperature is very noticeable wish I  had done the same.

Extracting the heat from the roof makes a big difference we did that in Aus.

Balconies and overhanging eves have  been used on homes in Queensland for years also good.

Finally as others have suggested plant plenty of trees, after nine years we have noticed a big difference keeps the sun off the house.

[hotchilli]

17 hours ago, 4myr said:

However there are days of 40-45C during the 2-3 hot months of the year whereby there is no wind. What are then the best passive cooling strategies, assuming as much heat reflection and insulation is applied to low thermal mass roof & walls and external shading or roof overhang is applied to windows.

Sit in a bucket of iced Chang with a long straw.

[4myr]

thanks for the many responses. To summarize what I've learned and take back:

• cavity walls, I was considering AAC blocks or low tech strawbales as low thermal mass walls
• microclimate - lots of trees [unfortunately have to wait at least few years] and also dehumidifying plants in and around the house
• underground cistern tanks as better thermal mass than soil

Wrt comments on point 3 of my OP:

• I agree there is no proven example yet, although the earthship inventor Michael Reynolds has implemented relatively short lengthed earthtubes in the Philipines, Indonesia and Puerto Rico without quantitative data to prove that it works
• the ecohouse example was afaik a closed system heat exchanger [not passive] and not an airflow earthtube. You can protect collapse of hdpe tubes with concrete drain pipe. Pest, insect and mold control can also be designed, but again no cost/benefit data yet seen - https://www.homeintheearth.com/tech_notes/earth-tubes/earth-tube-concerns/

[Max69xl]

In my opinion, insulation is really important. There are so many houses/buildings with non-existing insulation. The heat builds up during the day, especially on sunny days and it feels like living in an oven. In Thailand people seems to think that insulation is used in colder countries, and is not needed here, big misunderstanding. 

[sometimewoodworker]

3 hours ago, 4myr said:

thanks for the many responses. To summarize what I've learned and take back:

• cavity walls, I was considering AAC blocks or low tech strawbales as low thermal mass walls
• microclimate - lots of trees [unfortunately have to wait at least few years] and also dehumidifying plants in and around the house

Strawbales will provide a great food source/home for all kinds wildlife. AAC will not.

 

There are a wide variety of shade plants, including bamboo, that don’t take years to start proving enough heat protection.

 

Plants (unless electrical powered) do not dehumidify.  

Edited October 8, 2020 by sometimewoodworker

[patman30]

i plan to use same technique (along with others already mentioned above)
my land is on a hill and air inlet pipes will be buried 2-3 meters, running from bottom of the hill to the top
i will also build a small room around the intake pipe and keep this room cool (maybe even include a small ircon)
i would be very interested to see how you progress

[CLW]

Shade, insulation and a dehumidifier should probably do it.

If you cant stand the direct cooling stream of a air condition, I suggest you to look into a square ceiling unit.

Those distribute the cold air much more evenly than the regular wall units.

You might also look into something called wall or ceiling cooling.

This has become known in Europe because you can use a thermal heat pump.

In Thailand you probably attach the compressor of your A/C

[Ireland32]

5 hours ago, Crossy said:

Plants, plants and more plants.

 

When correctly positioned they provide shading so the walls don't heat up excessively, but they also provide natural evaporative cooling when they transpire water from their roots out of the leaves.

 

They look nice too ???? 

 

https://www.osti.gov/servlets/purl/5450077

https://www.bobvila.com/articles/54-quick-tip-your-plants-can-cool-your-house/

https://www.epa.gov/heatislands/using-trees-and-vegetation-reduce-heat-islands

Brings mossies and with dengue and Chikagunda  outta control here 

[zaZa9]

What works in many tropical areas is having the house on stilts. 

The underneath is fully shaded by the house itself , and stays a lot cooler.

Grow some tall shrubbery on the edges of the slab  and hose the plants   occasionally  and briefly on very hot days.... on the hottest , sleep down there as well , with a fan on you.

You also double your floor space with a house on stilts  , have a great place to dry laundry in the Wet , and  a spot to tinker with things that need fixing. Tall trees on the  blocks boundary ( say 10 metres from the house ) in line with the rising and setting sun also help.

We added a stainless kitchen ( all portable stuff )  and fridge , and I pretty much now live 'downstairs'.

The only a/c upstairs is in the bedroom , which is used to pre-cool the room if needed and we have to use it.

 

[natway09]

It is not possible to actually reduce the humidity of the ambient air without some sort of dehumidifier.

In saying that, shade trees, air movement will make you feel "cooler" can reduce the actual temperature in the house a few degrees

compared to one without shade or ceiling insulation. High ceilings help,

Check your night temperatures & humidity say at 3am. If significantly different then this is the time to mechanically ventilate your hose 

then close all windows & doors before starts to "warm up", although it is difficult not to open doors during the day unless you are a hermit 

A de humidifier in the house during the day can again reduce the humidity which will make you feel cooler.

We have an aircon in the lounge/kitchen where  in the very hot times (6 weeks a year) run at 28d during the day.

This dehumidifies hundreds of litres of water but not too cold (compressor runs about 18 minutes an hour after the first hour.

Cost to run, approx 200 Bht a wreek, & never used more than 10 weeks a year

 

[4myr]

https://www.sciencedirect.com/science/article/abs/pii/S0378778813003976

First quantitative study on earthtube in Thailand I found. COP results seems not so bad.

 

Differences with house settings:

• greenhouse with added solar heat vs house setting with human bodies exhibiting at least 100W per person and electrical equipment like TV and fans
• horizontal tube vs tube with slight elevation to drain the condensation at ambient air entry point 

 

[ourmanflint]

5 hours ago, 4myr said:

thanks for the many responses. To summarize what I've learned and take back:

• cavity walls, I was considering AAC blocks or low tech strawbales as low thermal mass walls
• microclimate - lots of trees [unfortunately have to wait at least few years] and also dehumidifying plants in and around the house
• underground cistern tanks as better thermal mass than soil

Wrt comments on point 3 of my OP:

• I agree there is no proven example yet, although the earthship inventor Michael Reynolds has implemented relatively short lengthed earthtubes in the Philipines, Indonesia and Puerto Rico without quantitative data to prove that it works
• the ecohouse example was afaik a closed system heat exchanger [not passive] and not an airflow earthtube. You can protect collapse of hdpe tubes with concrete drain pipe. Pest, insect and mold control can also be designed, but again no cost/benefit data yet seen - https://www.homeintheearth.com/tech_notes/earth-tubes/earth-tube-concerns/

I am planning to put our cistern underneath and supporting our decking on north side of our house out of the sun, so doesn't need to be completely underground, foundations won't be more than a metre underground. If you do go the full underground cistern route, would be very interested to see how stable the temperature is over a season

[Our Man in the Tropics]

1_

"Recommended” Colors for the EXTERNAL Surfaces [ Walls, & Roof ] so as to “reduce” the Rate of Absorption of Heat from “Sun”, & “reflecting Surfaces in external Environment” [ source Sunlight Radiation ] :

1st Choicest ; White

2nd Choicest ; Red

3rd Choicest ; Orange

4th Choicest ; Yellow

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

2_

"Recommended” Colors for 2 number [ viz. Walls, & Ceiling(s) ] of the 3 “ultimate” INTERNAL Surfaces* so as to “reduce” the Rate of Radiation of Heat from “Sun”, & “reflecting Surfaces in EXTERNAL Environment” [ source Sunlight Radiation ]

1st Choicest ; White

2nd Choicest ; Red

3rd Choicest ; Orange

4th Choicest ; Yellow

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

3_

"Recommended” Colors for 1 number [ viz. Ground Floor ] of the 3 “ultimate” INTERNAL Surfaces* so as to :

3_1_

“reduce” the Rate of Radiation of Heat from “Sun”, & “reflecting Surfaces in external Environment” [ source Sunlight Radiation ] through Openings & Transparent Panels

AND

3_2_

“increase” the Rate of Absorption into Heat-Sink [ Earth or Rock or Concrete ] of Heat from the Air that is within Building

 

Any of the Colors NOT at extreme ends of Color Spectrum :

Yellow

Green

Blue

 

I, myself, would think that Pale-Blues or Pale-Greens or Pale-Yellows would be optimum vis-a-vis Heat Reduction & Agreeableness for Living

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

*The “ultimate” INTERNAL Surfaces – being 3 in number – are :

Walls

Ceilings

Ground Floor

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

4_

And,- the hardest [ as opposed to most matt ] surface in Insulation Products is seemingly NOT available in White ;

Rather,- Silver only.

Therefore,- fIt :

4_1_

Double-sided "Silver" Foil Insulation directly under Roof

4_2_

Double-sided "Silver" Foil Insulation directly above Uppermost Floor Level Ceiling