Insulation

[londonthai]

after reading here about the concept I am thinking about re-doing some of the worst rooms in my house at some stage.

Because it's a small teak wood house I am thinking about very light materials, like reflective film or paper. Which one and where should I use? I think they are usually reflective from one side - which side to outside or get them reflective from both sides?

what about my previous question about rock wool boards as a ceiling and as walls?

[astral]

Another idea for roof insulation is a large fan to keep the air moving

through the roof space, and avoid the build up of heat there.

If you look at the roofs of traditional buildings they always have louvres to

promote air flow. This idea is just an extension of that.

The fan could be powered by a solar panel.

[GuestHouse]

after reading here about the concept I am thinking about re-doing some of the worst rooms in my house at some stage.

Because it's a small teak wood house I am thinking about very light materials, like reflective film or paper. Which one and where should I use? I think they are usually reflective from one side - which side to outside or get them reflective from both sides?

what about my previous question about rock wool boards as a ceiling and as walls?

Put the reflective side of the foil towards the heat (away from the living space).

I'm trying to imagine your house construction, but if it is wooden then it already benefits from low thermal mass. You might be better putting insulation in the roof space and shading while not insulating the walls.

[londonthai]

what about white paint on the roof (yes, I know it would lower the temperature under the roof and reduce air flow between the walls) - but at the same time a good white paint can prevent up to 50% heat being absorbed and than passed through ceilings into the rooms.

how is that kind of paint called and where to get it?

[astral]

You can definitely get Roof Tile Paint,

but I am not sure if it comes in white.

[udon]

House building in Darwin, Aus. Same climate as Thailand but with cyclones.

[LoveDaBlues]

I have heard about white colour external walls exposed to sun - what about internal walls? Painting them dark/black would allow the heat to escape out

I don't think so because white color outside reflects the sun while dark color outside absorbs the sun. No sunshine inside.

[Thaddeus]

"......................

One thing that I have always found curious is that the hong nam is the coolest room in the house (not using any aid like a pad lom or air-con of course).... when the power has failed, which has a tendency to happen, especially during a large thunderstorm, we have even slept in there..... has that got anything to do with the size of the small window?

The small window means that very little sunshine will enter the bathroom so this will certainly help to keep it cooler. If your bathroom is always cool, I bet that the sun never shines on its external wall...or if it doe it probably only shines there for a brief time.....is this right?

Chownah

Yes, absolutely right.

And, I think that the wife and daughter throwing cold water over themselves four times a day, at least, will also have an effect.

Hmmmm.... there's a thought, could water be used, not as a form of insulation, but as a heat removal mechanism?

Edited August 29, 2006 by Thaddeus

[chownah]

"......................

One thing that I have always found curious is that the hong nam is the coolest room in the house (not using any aid like a pad lom or air-con of course).... when the power has failed, which has a tendency to happen, especially during a large thunderstorm, we have even slept in there..... has that got anything to do with the size of the small window?

The small window means that very little sunshine will enter the bathroom so this will certainly help to keep it cooler. If your bathroom is always cool, I bet that the sun never shines on its external wall...or if it doe it probably only shines there for a brief time.....is this right?

Chownah

Yes, absolutely right.

And, I think that the wife and daughter throwing cold water over themselves four times a day, at least, will also have an effect.

Hmmmm.... there's a thought, could water be used, not as a form of insulation, but as a heat removal mechanism?

The water splashing no doubt has some effect but I'm not sure how much. My view of why your bathroom stays cool goes like this:

1. There is nothing in the bathroom that makes heat...not TV, usually no lights on, no cooking, no warm bodies sitting for hours, etc. Mostly the bathroom is empty and no heat is being produced there.

2. You have already said that the sun doesn't shine on the bathroom walls so the sun is not acting like a heat source to heat up your bathroom.

1. and 2. combined: There isn't alot of heat going into the bathroom so it is not difficult to keep it cool.....but what makes it cool..............

3. At night cool air circulates through the bathroom cooling the walls and floor which (I assume) are made from cement or cement blocks or brick with mortar....and with render (plaster). This means that your bathroom has a lot of thermal mass...thermal mass is something which can hold alot of heat and usually can hold a lot of heat without changing temperature too much. So...in the morning you've got a bathroom filled with thermal mass that is all cooled down.

4. As the sun comes up the outside air gets warmed and some of it enters the bathroom and starts to warm up the thermal mass (walls and floor).....but the large thermal mass in the bathroom can absorb the heat from the warm air quite easily because the air has very low thermal mass and it will take alot of warm air circulating to warm up the bathroom walls and floors only a little bit....and in the process the air gets cooled.

So...that's how I see it. If you want to increase this effect you should insulate the ceiling of the bathroom (if its not insulated already) to keep heat from entering from above.....and you could put a small fan on a timer so that it circulates cool air for a couple of hours just before sunrise when the outside air is the coolest....I think this fan would be cost effective compared to aircon but I have not proof of this...on the other hand just how cool do you need your bathroom to be?...on the other other hand this technique is sometimes used in designing entire houses as a form of energy efficient cooling.....the concept being to shade all the exterior walls maximally and to cool a large thermal mass at night by circulating exterior night air and then keeping things mostly tightly closed in the day (ventilation is necessary however) and control the ventilation so that fresh air is adequate but excess infiltration of hot air is avoided.

Chownah

[eljeque]

I painted my roof white with roof paint. It was expensive but saved a lot in energy bills. The typical orange tiles get very hot.

Why don't you build your house underground? A basement? Or, at least have a basement that you make into your cooling center. Build a cooling center (a giant radiator) underground and have it bring cool air into your home.

[londonthai]

traditional thai style is a house elevated on stilts - often the houses were build over/near the water. They used an idea of a wind moving through the house.

If you dig up a hole under your house it will fill, sooner or later, with water

[suiging]

Thailand is blessed with land by the sea or land in the hills both with natural breeze. If you are going to buy a parcel of land, take natural insulation into account, many people do not. There is a reason why the local lives in " A " and sells you " B " where he farms or grazes cows.

[Nawtilus]

White paint used on roofs is a 'ceramic reflective' paint. Price i got recently here was 220/250b per sqm.

[chownah]

traditional thai style is a house elevated on stilts - often the houses were build over/near the water. They used an idea of a wind moving through the house.

If you dig up a hole under your house it will fill, sooner or later, with water

There is another approach to using earth to keep a house cool....instead of digging a hole you build a hole. If you build a house with its first floor up from the natural drainage and you reinforce the first floor walls enough you can then build an earth embankment around the first floor and in this way create a basement that is above the flooding....this works just like a basement in keeping your house cool....I'm surprised that this style is not even usually considered for houses here in Thailand.

Chownah

[Naam]

"I painted my roof white with roof paint."

it sure helps when the colour of your roof tiles reflect radiation. but there are several other points which should be taken into consideration:

-roof attic (if any) has to be ventilated properly. if not by natural "chimney draft" then a couple of 20 watt electric fans (available in home marts for ~ THB 700) should do the trick. for big homes with a huge attic it takes ½HP or approximately 365 watts to prevent the attic heating up and achieve the more or less the same temperature as the ambience on a sunny day. i did some tests and measured the temperature on the top most point in my attic. result: 69ºC without and 36ºC with forced ventilation. ambient temperatur at latter measurement 32ºC.

-insulation mats backed on both sides with aluminium foil if you have gypsum ceilings. won't help too much on concrete ceilings.

the list is very long but i limited myself to describe "roof" only.

[ilyushin]

"I painted my roof white with roof paint."

it sure helps when the colour of your roof tiles reflect radiation. but there are several other points which should be taken into consideration:

-roof attic (if any) has to be ventilated properly. if not by natural "chimney draft" then a couple of 20 watt electric fans (available in home marts for ~ THB 700) should do the trick. for big homes with a huge attic it takes ½HP or approximately 365 watts to prevent the attic heating up and achieve the more or less the same temperature as the ambience on a sunny day. i did some tests and measured the temperature on the top most point in my attic. result: 69ºC without and 36ºC with forced ventilation. ambient temperatur at latter measurement 32ºC.

-insulation mats backed on both sides with aluminium foil if you have gypsum ceilings. won't help too much on concrete ceilings.

the list is very long but i limited myself to describe "roof" only.

A+ on your homework! Great tests and results.

[chownah]

.

-insulation mats backed on both sides with aluminium foil if you have gypsum ceilings. won't help too much on concrete ceilings.

I don't see any reason why insulation mats wouldn't work just fine for concrete ceilings. Any foil must have an air space between it and the ceiling surface or between it and the roof tiles for it to function properly. If you laid foil faced insulation mats directly on any ceiling then the foil face against the ceiling will loose most if not all of its insulative effect....but the matt itself should do just fine and the foil facing above should work fine too.

Chownah

[chownah]

Let's compare a 5mm cement board ceiling without insulation with a 5mm cement board ceiling with a couple of inches of foam or fiber insulation. I'm familiar with US R-values and know that the cement board has a US R-value of about 0.30 and the couple of inches of foam or fibre will have a US R-value of about 6.0.

Let's convert these US R-values to metric R-values....that means we must divide them by 6 (actually it is 5.7 but 6 is close enough)....then we get that the cement board has a metric R-value of 0.05 and the 2 inches of foam or fibre has a metric R-value of 1.0.

Next we can convert these R-values into U-values since this will tell us how many watts will move through one square metre of ceiling....to convert R-values to U-values you invert them...this means to divide the R-value INTO 1.0. So...for the cement board 1.0/0.05 = 20 and for the foam or fibre insulation 1.0/1.0 = 1.0......so the metric U-value for the cement board is 20 which means for every degree C difference between the inside and outside temperatures you will get 20 watts of heat entering the room.......and for the insulation you will get 1 watt of heat entering the room for every degree C difference between the inside and outside temperature.

So...let's look at a well ventilated attic which will have approximately the same temperature at the top surface of the ceiling as it is outside....let's say 35 deg C......and lets say that you keep the inside aircon set at a comfortable 25 deg C. This means that the difference in temperature between the inside and outside is 10 deg C so one square metre of unsinsulated ceiling willhave 10 x 20 = 200 watts of heat entering and a 3m x 4m = 12 sq. m room will have 2,400 watts of heat entering so a 4,800 watt air con unit would have to work 30 minutes every hour to expell this heat. Under the same conditions the insulated ceiling would have 1 x 10 = 10 watts per square metre entering the room and for the 12 sq. m room you would have 120 watts entering the room and the same 4,800 watt air conditioner would only have to work 1.5 minutes every hour to expell this heat.

Now let's compare an attic with less efficient ventilation....let's say that the attic temperature at the upper surface of the ceiling is 45 deg C.....then the difference in temperature between the inside and outside is 20 deg C and the uninsulated ceiling will have 20 x 20 = 400 watts per square metre of heat entering and the 12 sq. m room would have 4,800 watts of heat entering.....so the 4,800 watt air con unit would have to work constantly to expell the heat entering throught the ceiling to maintain the 25 deg C temp inside!!!!!!!!!! On the other hand the insulated ceiling would have 1 x 20 = 20 watts per square metre entering and for the 12 sq. m room there would be 20 x 12 = 240 watts entering so the aircon would have to work 3 minutes every hour to expel this amount of heat.

I believe that these calculations are correct....if anyone sees a problem with them please let me know.

As you can see, a couple of inches of foam or fibre can make a big difference on how hard your aircon must work. I want to stress that this analysis is only approximate but you can see that the improvement from the insulation is very very large so any slight variation due to slight differences in materials or thickness will not invalidate the conclusion. Also please note that I am only analysing the ceiling and I am not analysing the walls or floors or doors or windows so this is not meant to indicate how to size your air con unit but it is only meant as a simplified example to help see how much insulation in a ceiling can help in reducing your cooling load.

Chownah

[chownah]

I hope that the technical stuff doesn't cause complete befuddlement. Many times doing calculations puts people off but I presented that stuff here in the hopes it might help people see more clearly how effective their efforts to insulate their homes might be. If you do not understand what I have written don't be shy about asking questions...I can guarantee you that many people who read it came away scratching their heads....not just you. If I can answer your questions (or someone else here can) then you stand to benefit not only from a better understanding but also from a more comfortable home.

Chownah

[rijb]

You can, but be careful as I have seen many applications where the application of insulation and building methods is patched together wrongly – If you are designing a house you should consider how the insulation works as a ‘system’ rather than individual elements.

Example: Double wall insulation.

In a cold climate, this works by providing a barrier to the heat loss from within the building (heat is traveling outwards). Air is trapped in the inner space, to help prevent heat flow from inside to outside.

However, this basic idea can be improved on. The main problem with the basic design is air will still move in the gap, stripping heat from the inner core as it does so.

Keep in mind the temperature difference can be extremely high. Perhaps 23Deg C inside the building, with air in the core near freezing (air entering from air vents can be well below freezing), so this ‘heat stripping can be considerable’.

The improvement is to add foam or insulating rock wool to trap the air, reduce it’s movement and prevent that stripping motion.

So in a cold climate, zero air movement is a good thing.

Now consider a hot climate.

The outer surface is getting heated by direct sunlight, there is also an ambient air temperature, in Thailand the ambient air temperature is usually between 26DegC and 32DegC, just a little above what most of us find comfortable.

The outer wall temperature can easily reach 70DecC in direct sunlight (depending on wall color) – Witness burned feet on pure white (normally reflective) sand.

Now here’s a problem. The outer wall has a thermal mass, once hot it will stay hot until it radiates it’s heat to its surrounding. If you trap air in an insulating layer between the outer layer and the inner layer, you will allow that to heat up and pass the heat into the inner core. (Even if the inner core is insulated, the heat is going inwards, perhaps slowed by the insulation, ie Q-Block, but it is nevertheless going inwards).

Note here the inner insulation Qblock is only reducing the rate of heat flow, it is not stopping it.

To reduce this inward flow of heat you can do one of three things, you can reduce the amount of heat stored in the outer wall, or you can reduce the amount of heat passing across the air gap.

Reducing the heat stored in the outer wall can be done in several different ways.

Use lower thermal mass materials (wood cladding being an example) This has the effect that as soon as the sun goes off the wall it rapidly cools to the ambient air temperature. I’m sure we’ve all walked past a wall that is still radiating heat well into the late evening (that is a high thermal mass wall and not what you want on a house in a hot climate).

Color is important, painting your outer walls white will reflect heat rather than allowing heat to be absorbed.

Growing plants, creepers and trees to throw a shade on walls exposed to the sun reduces heat up take. Adding a screen near a wall does the same thing.

And then, making best use of the wall’s air gap, you can encourage airflow between the walls. Remember, the wall might reach 70DegC but the ambient air temperature is very likely to be lower than 32DegC.

To increase airflow, simply add vents at the bottom of the wall and allow the gap of the wall to continue right into the loft space. Then add a vent (or two) to the loft space and close up as many gaps into the loft as possible (especially under the eves).

Now as the roof heats up, hot air rises in the loft space and moves out through the vents, as it does so it draws cold air in through the vents at the bottom of the walls.

This air movement will strip heat from the outer walls and allow it to flow up through the roof vents.

Ideally you would use all these components together to create a system of insulation and cooling. But don’t forget to add bug screens to all the vents!!!

Why Insulation Systems and not Components?

You now have to give some thought as to how to insulate your loft. If, as is popular with Farang builds in Thailand, you add reflective insulation under your roof tiles, you are reducing the heat into the loft space and removing the driving force that is sucking air through the wall space.

So if you are using this wall space draught method, don’t insulate under your tiles, but do add loft insulation mats above your ceiling (I suggest at least 4inches of rock wool with a reflective surface underneath.

Of course if you are not using the cavity walls and air movement to cool the building then the reflective insulation under the tiles is not going to cause a problem with the insulation design of the house. And is a cheap effective way of keeping the roof space cooler. Though I would still add vents and loft matting.

My wife and I are going to build another house in Chiang Rai. I've been combing all the old posts for ideas. We like your 'hot climate insulation system'. Do you have any new tips, tricks, or traps since your OP? Thank You.