House insulation for hot climates

[Bandersnatch]

I built an off-grid home with no utility bills.

 

I have put what I learnt about insulation for hot climates into a video:

 

 

 

[Donoff]

This is really cool. Did you do this project for fun or because you hoped to have lower utility costs?

[Bandersnatch]

16 minutes ago, Donoff said:

This is really cool. Did you do this project for fun or because you hoped to have lower utility costs?

I wanted to be off-grid and not reliant on PEA

[unheard]

Lots of good info.

The only problem is the huge cost of implementation.

 

I have a question regarding floors.

Why to insulate ground floors in Thailand?

It only makes sense to do in colder climates.

[Bandersnatch]

1 minute ago, unheard said:

Lots of good info.

The only problem is the huge cost of implementation.

 

I have a question regarding floors.

Why to insulate ground floors in Thailand?

It only makes sense to do in colder climates.

If you run aircon the house will be cooler than the outside. Concrete has no insulation value and heat will move into the house to restore equilibrium temperature 

[unheard]

1 minute ago, Bandersnatch said:

If you run aircon the house will be cooler than the outside. Concrete has no insulation value and heat will move into the house to restore equilibrium temperature 

But the ground under the house is not heated.

[Bandersnatch]

5 minutes ago, unheard said:

But the ground under the house is not heated.

The ground beside the house directly heated by the sun will be in the 50s degree Centigrade. “With heat transfer the driving force is temperature difference” - first words of my video. The bigger the temperature difference the quicker the temperature equalization will occur. Earth has a low R value
 

[unheard]

3 minutes ago, Bandersnatch said:

The ground beside the house directly heated by the sun will be in the 50s degree Centigrade.

I disagree and it's a debatable topic unless there's some related research on the subject.

The ground will only be heated outside of the house walls, on their perimeter.

The soil temperature under the floor will come into an equilibrium with the underground soil temperature and remain constant.

The soil temperature stays in the low 20s at few meters of depth.

 

The other option is to have an elevated floor with the space underneath that is ventilated.

There are many houses  in Thailand that's been constructed that way.

The elevated floor comes with an added benefit of having extra protection from flooding.

[Kwasaki]

I like lots of light and windows and open windows for fresh air. 

An 18 BTU cooler unit is not expensive to run when it's sleep time until then airflow and fans and light is what we like. 

 

Shading from overhanging roof areas and insulated ceilings are all that was needed in our case. 

[Bandersnatch]

15 minutes ago, unheard said:

The soil temperature stays in the low 20s at few meters of depth

I agree "soil temperature stays in the low 20s at few meters of depth" a similar R value to concrete of 0.1 per inch

 

16 minutes ago, unheard said:

I disagree and it's a debatable topic unless there's some related research on the subject

Unfortunately you cannot debate the laws of physics but if you want some research I have just been outside to conduct some.

 

Temperature of the ground in full sun:

 

Temperature of the shaded uninsulated foundations:

 

Now the foundations are at 39 degrees the concrete will quickly pass that heat through the rest of the concrete of the house until they reach the insulation layer.

[unheard]

7 minutes ago, Bandersnatch said:

Unfortunately you cannot debate the laws of physics but if you want some research I have just been outside to conduct some.

Thank you for posting the pictures.

But how are they relevant to ground temperatures under the house floor?

Not near or outside the walls, not at the perimeter but directly underneath.

Are laws of physics being debated here?

 

[unheard]

23 minutes ago, Bandersnatch said:

Now the foundations are at 39 degrees the concrete will quickly pass that heat through the rest of the concrete of the house until they reach the insulation layer.

So, concrete has no thermal mass then?

And what happens at night then?

[Kwasaki]

7 minutes ago, unheard said:

Thank you for posting the pictures.

But how are they relevant to ground temperatures under the house floor?

Not near or outside the walls, not at the perimeter but directly underneath.

Are laws of physics being debated here?

 

Laws or not I have a concrete beam layout with concrete slabs foundation with tiles throughout the ground floor area and they are cold to the feet all day. 

[jvs]

Why do you think so many Thais sleep on the floor? Because it is cooler.

One way of keeping the temperature of the ground around the house cool is shade!Trees!

Too many people from other countries come live here and forget where they are when they build a house.

It is all walls and nothing is letting the cool breeze in.

It takes awhile before you can change that mindset.

 

[unheard]

8 minutes ago, Kwasaki said:

Laws or not I have a concrete beam layout with concrete slabs foundation with tiles throughout the ground floor area and they are cold to the feet all day. 

That would probably be the very common experience with concrete floors all throughout Thailand.

[Kwasaki]

15 minutes ago, unheard said:

So, concrete has no thermal mass then?

And what happens at night then?

Yes. 

It gets cooler.

[Kwasaki]

2 minutes ago, unheard said:

That would probably be the very common experience with concrete floors all throughout Thailand.

Yes for many years a solid concrete slab is not what I wanted. 

[Bandersnatch]

21 minutes ago, unheard said:

Thank you for posting the pictures.

But how are they relevant to ground temperatures under the house floor?

Not near or outside the walls, not at the perimeter but directly underneath.

Are laws of physics being debated here?

 

Trying again ….

 

R-value is a measure of how a material resists the conductive flow of heat. Concrete has an R-value of 0.1 meaning that heat easily passes through it. It will be heated from the edges and cooled from above when you switch on the air con. 

[Bandersnatch]

29 minutes ago, unheard said:

So, concrete has no thermal mass then?

And what happens at night then?

The fact that concrete easily absorbs heat means it has a lot of thermal mass - did you not hear what I said dark colored concrete roof tiles in Thailand? 

[unheard]

5 minutes ago, Bandersnatch said:

The fact that concrete easily absorbs heat means it has a lot of thermal mass - did you not hear what I said dark colored concrete roof tiles in Thailand? 

If it easily absorbs heat then it would be equally easy for it to loose the same amount of heat at night.

Yes, the same way as in the case of roofing concrete tiles.

But you're comparing two incomparable things.

The concrete slab vs tiles, which have minuscule thermal mass.

The concrete slab has enormous thermal mass in comparison, is not exposed to sunlight and is not heated by outside air.

The only heat input it might get is on its perimeter which is negligible in comparison to the amount of heat absorbed by roofing tiles.

Edited December 7, 2022 by unheard

[Bandersnatch]

5 minutes ago, unheard said:

If it easily absorbs heat then it would be equally easy for it to loose the same amount of heat at night.

Agreed some of that heat will pass into the house 

[unheard]

5 minutes ago, Bandersnatch said:

Agreed some of that heat will pass into the house 

And most of it will be re-radiated back into the atmosphere.

[phetphet]

OP.

Looking  back now. Is there anything that you wish you had done differently? Or changed?

Any modifications that you plan to do?

 

I do recall your underground air pipe collapsed through weight of soil. Did you haver to fix it?

[Bandersnatch]

12 minutes ago, phetphet said:

OP.

Looking  back now. Is there anything that you wish you had done differently? Or changed?

Any modifications that you plan to do?

 

I do recall your underground air pipe collapsed through weight of soil. Did you haver to fix it?

I did an inexpensive geothermal experiment using PE pipe as it was impossible to source genuine geothermal pipe in Thailand. As you said it wasn’t successful.
 

I am still looking at Geothermal and think the way to go is either a closed or open loop groundwater system combined with a heat pump. Water has a far higher thermal conductivity than air (0.6 vs 0.025 Watts per m Kelvin) So it is far more efficient at moving cold into a warm house or heat into a cold house.  Easy enough to drill a bore hole down to the water table. I have 3 solar well pumps and have tested the temperature of the water at 30m and it is a steady 19°C all year round.
 

 

[sometimewoodworker]

4 hours ago, Bandersnatch said:

I agree "soil temperature stays in the low 20s at few meters of depth" a similar R value to concrete of 0.1 per inch

 

Unfortunately you cannot debate the laws of physics but if you want some research I have just been outside to conduct some.

 

Temperature of the ground in full sun:

 

Temperature of the shaded uninsulated foundations:

 

Now the foundations are at 39 degrees the concrete will quickly pass that heat through the rest of the concrete of the house until they reach the insulation layer.

Your 2 pictures are rather less than accurately captioned, are they not?

 

you are not actually measuring the ground in full sun, but a concrete slab in full sun.

 

Nor you measuring the  shaded uninsulated foundations, but the shaded but still connected concrete slab.

 

the way to mitigate this is do not have a concrete slab that is in full sun, this makes the measurements rather less beneficial to your argument but better for not having heat gain.

 

our house has one side that has sun up to about 10am and a parking area that gets full sun throughout the day but only for about 2 metres at the end of a 7 metre length, so there could be a small conductivity heat gain but it is insignificantly small.

 

Our floor is raised so is some heat gain from the air but not that much.

 

FWIW. any one who has a concrete slab (often walkway) that gets full sun has a night storage heater to keep them warmer during the night. British night storage heaters are large blocks of concrete heated by nighttime electricity. The reverse happens in Thailand (without the electricity input but with the benefit of the solar nuclear input) ???? 

[Bandersnatch]

31 minutes ago, sometimewoodworker said:

Your 2 pictures are rather less than accurately captioned, are they not?

 

you are not actually measuring the ground in full sun, but a concrete slab in full sun.

I am not sure how you know better than I do where my slab starts and finishes! The first photo has no concrete underneath, just dirt. 

 

 

 

45 minutes ago, sometimewoodworker said:

Nor you measuring the  shaded uninsulated foundations, but the shaded but still connected concrete slab.

In the second photograph this is what I was measuring  - doesn't look like a slab to me, but if you want to call it a slab, I will let it slide 

 

 

 

47 minutes ago, sometimewoodworker said:

any one who has a concrete slab (often walkway) that gets full sun has a night storage heater to keep them warmer during the night. British night storage heaters are large blocks of concrete heated by nighttime electricity. The reverse happens in Thailand (without the electricity input but with the benefit of the solar nuclear input)

This I agree with 

 

 

[sometimewoodworker]

1 hour ago, Bandersnatch said:

2 hours ago, sometimewoodworker said:

 

I am not sure how you know better than I do where my slab starts and finishes! The first photo has no concrete underneath, just dirt. 

Then your pictures are giving a completely false impression as they both show what the vast majority would classify as concrete 

 

1 hour ago, Bandersnatch said:

In the second photograph this is what I was measuring  - doesn't look like a slab to me, but if you want to call it a slab, I will let it slide 

I certainly would not class the foundation as a slab either.

 

The majority of people do have a concrete walkway around the outside that they connect to the foundation (slab or beams), I am not convinced that concrete is as good a thermal conductor as you suggest, it certainly could be but then why do night storage heaters take so long to both heat and cool? 
 

Concrete is an excellent heat store but probably not anything nearly as good at gaining one releasing the heat

 

However earth is generally a poor conductor of heat so while the outer ring beams maybe at 39 degrees it’s unlikely that the temperature is uniform

 

 

Edited December 7, 2022 by sometimewoodworker

[Bandersnatch]

10 hours ago, sometimewoodworker said:

I am not convinced that concrete is as good a thermal conductor as you suggest

 

10 hours ago, sometimewoodworker said:

earth is generally a poor conductor of heat

 

 

Both dirt and concrete have very poor insulative properties which means that they are good conductors of heat compared to something like foam which has an R value of 7  - that is why they serve hot coffee in foam cups

 

If you have any further questions please ask Google

[sometimewoodworker]

24 minutes ago, Bandersnatch said:

Both dirt and concrete have very poor insulative properties which means that they are good conductors of heat compared to something like foam

That something is better than another doesn’t prove that the first is bad.

You contend that soil is a poor insulator but do it by a graphic that is totally irrelevant as it’s about soil pressing against foundations.

If soil were as good a conductor as you suggest (it clearly cannot be as your own measurements conclusively provided proof of) then shade wouldn’t do anything much to stop heat transfer.

 

Your own measurements show a 20 degree differential within a few centimetres.

naturally there is insulation that is vastly better but your own logic and observations would suggest that earth is not as a good a transmitter of heat as you suggest.

[Kwasaki]

It's a good discussion if you are about build. 

Too late i found out about many things about build in hot climates, a 'U' shape build with the opening facing North with areas of high ceilings and open areas within the 'U' shape design. 

 

I not about to knock down what I have now being retired from building. ????????