R-Value / Thermal Mass Numbers

Air conditioning, fans, and anything related to keeping it cool, such as insulation. This would include any posts generally discussing how to keep it cool, such as which types of blocks are better insulators.... ideal wall thickness for keeping an A/C house cool, etc.

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R-Value / Thermal Mass Numbers

Postby oil » Fri Apr 18, 2014 11:53 am

i am considering building a eco style builing, and i am planning towards a Earthbag House.
However i am just a computer geek and have not too much knowledge about buildings and such.

So far i read a few books about Earthbag houses however it help me if someone could explain me those numbers a bit more

Image

Naturally i am looking for a building material which keeps the heat out!
however every building heat up after some time, and cools down in the night time.

Cause english is not my native language i sometimes cant grasp the meaning of some words, and translators arent very helpfull as well cause i dont get the meaning of the technical term.

So when i understand the above thing right, its that
Clay block 40 cm can store the most heat for the longest time (thats probably not what i want)

and what they mean with light earth, i know that earth contains clay, i made some test on our land and there we had like 10% - 15% of clay in the soil

anybody has a better / different idea on what this table actually says?
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Re: R-Value / Thermal Mass Numbers

Postby fredlk » Fri Apr 18, 2014 12:30 pm

oil wrote:Naturally i am looking for a building material which keeps the heat out!

Then AAC blocks are the best. They don't heat up and so don't retain any heat at all.
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Re: R-Value / Thermal Mass Numbers

Postby oil » Fri Apr 18, 2014 12:52 pm

fredlk wrote:
oil wrote:Naturally i am looking for a building material which keeps the heat out!

Then AAC blocks are the best. They don't heat up and so don't retain any heat at all.


yepp seem to be the best,
i just read a PDF about those AAC blocks
http%3A%2F%2Fwww.safecrete.com%2Faac%2Fproducts%2Ftechmanual%2Fpdf%2Fthermal.pdf

and it seems their R-Value is 10 for a 8” AAC 32 pcf Wall System,
does anybody know how much a sqm of 20 cm thinck AAC Stones go?
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Re: R-Value / Thermal Mass Numbers

Postby fredlk » Fri Apr 18, 2014 12:58 pm

oil wrote:does anybody know how much a sqm of 20 cm thinck AAC Stones go?

I paid 45 Baht per block of 20cm. x 20cm. x 60 cm. a couple of years back.
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Re: R-Value / Thermal Mass Numbers

Postby oil » Fri Apr 18, 2014 1:19 pm

so one block is roughly 0.12 sqm, so i would roughly need 8 bocks per square meter wall, which would roughly go for 360 THB
thx so far ...

i was just reading on some site dedicated to Heat Protection
(in German Language - http://www.u-wert.net/berechnung-des-hitzeschutzes/)
that a high thermal mass of blocks can be a huge advantage to block out the heat.

Google Translate:
In order to achieve optimum heat protection, a specific combination of insulating and heat-storing layers is necessary. Rule of thumb: heat storage inside, insulation to the outside:

The further inner storage mass is arranged, the higher is the contribution to the heat shield
Therefore, especially the innermost layers should have the highest possible storage capacity, ie have a very high mass
Insulation on the inside does not improve the heat protection in practice
Wood and wood fiber boards offer a high storage capacity. Disposed on the outside as a cover plate, the improvement of the heat protection but 2-3 times lower than on the inside.

Why this is so, lights quickly: Does the hot outside air direct contact with the storage mass, the energy input and thus the heating of the storage mass is particularly high. Due to the thermal decoupling, that is, by a layer of insulation between heat storage and outdoor air, the energy input is significantly reduced in the relevant layers.

... Ventilation during cooler Evening-/Night hours and direct sunlight: The heat input by direct sunlight is about 200 - 1000 times greater than the heat input by a insulated wall. Suitable external shading devices are therefore indispensable. As long as the sun large windows seems unhindered by square meters in the room, the temperature amplitude attenuation does not matter practically.


so when i get that right then termal mass can be a benefit when it comes to getting the heat out? sounds odd thou LOL
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Re: R-Value / Thermal Mass Numbers

Postby fredlk » Fri Apr 18, 2014 1:25 pm

oil wrote:Rule of thumb: heat storage inside, insulation to the outside:

For cold climates yes, for Thailand no. Here you need to keep ALL surfaces from heating up so that no heat is stored and the temperature is kept as low as possible which means the same as the ambient air temperature.
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Re: R-Value / Thermal Mass Numbers

Postby oil » Fri Apr 18, 2014 1:48 pm

makes sense
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Re: R-Value / Thermal Mass Numbers

Postby Andyfteeze » Sun Aug 31, 2014 1:51 am

If there is a contradiction, its because a high thermal mass will retain any ambient heat. Two scenarios where it works for and against.
Concrete slab on 2nd floor exposed to the sun via a big window. The sun heats it up. The sun goes down and the slab radiates heat until it reaches ambient temperature. This happens slowly or quickly depending on size. Bigger is slower.
The sun heats the concrete at a faster rate than the ambient air can hold the temp.,

Concrete poured over the ground on the ground floor. Stays cool all the time because the soil underneath stays a constant temperature around 20degrees. The soil acts as a massive heatsink under the concrete. Cooling the concrete at a faster rate than the ambient air

Any high mass structure exposed to constant high temperature will eventually heatup to ambient air temperature.
The day / night temperature difference here in thailand is small. If the day time heats up faster than night time cool down, the temperature of the mass will fall slowly at night. So slow that when you wake up in the morning the walls may still warm to touch. 32degree heat pressure gradient at day. And maybe -6 degree pressure gradient at night. ( 32* - 26*).
So ram earth or any other high mass structure exposed to the elements really isnt going to make the grade here if you want a well designed eco house , unless the walls are 3 ft thick. A 3ft thick wall is going to be in contact with a large area of ground acting as a heatsink. Thats my thoughts.
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