Passive home construction

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Postby Ians » Mon Jun 09, 2008 7:32 am

" One would probably have to consider whether that residual heat in the walls at the end of the day would seriously contribute to one's nocturnal discomfort ---------"

This is one of the things that I am trying to decide on as the options are:

solid wall
cavity wall
cavity wall with insulation
vented cavity wall

all of which perform differently regarding heat storage/transfer - so the investigation continues with an endless amount of information to read and take in.
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Postby chiangmaiexpat » Mon Jun 09, 2008 9:02 am

I have friends who built houses with double brick (cavity) walls and walls with AAC blocks. Both reported good (noticeable) thermal insulation and they're both happy with their choice. I am going to build double brick walls with air cavity because: (1) it's significantly cheaper, (2) we don't need load bearing walls, (3) we can run pipes and cables through the cavity, and (4) the crew finds it easier to build. The air barrier in the cavity prevents direct heat conduction almost entirely, but it doesn't totally prevent convection. Insulation material in the cavity reduces heat transport by convection, so if installed properly it gives you better thermal insulation.

Cheers, CMX
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Postby Ians » Mon Jun 09, 2008 11:16 am

Here is an interesting link for those interested in house design

http://www.yourhome.gov.au/technical/index.html

As this is for Australia - south of the equator, you need to transpose north for south and south for north whenever referred to.
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Postby jazzman » Mon Jun 09, 2008 3:22 pm

chiangmaiexpat wrote:I have friends who built houses with double brick (cavity) walls and walls with AAC blocks.
- Both reported good (noticeable) thermal insulation and they're both happy with their choice. I am going to build double brick walls with air cavity because:
(1) it's significantly cheaper,
(2) we don't need load bearing walls,
(3) we can run pipes and cables through the cavity, and
(4) the crew finds it easier to build.

- The air barrier in the cavity prevents direct heat conduction almost entirely, but it doesn't totally prevent convection.
- Insulation material in the cavity reduces heat transport by convection, so if installed properly it gives you better thermal insulation.


Cheers, CMX


A brilliant summary. I have taken the liberty of highlighting your comments. You will be interested to know that the standard 40 x 20 x 6 Thai cinderblocks, if faced with 2 cm of render on the outside (weatherside) and on the inside (indoors) will also produce almost the same results. You can fill the gap with self-expanding foam too, or with styrofoam slabs (which should be a tight fit).

The Jazzman house was constructed using only a single layer of cinderblock, rendered both sides. The passive cooling design includes a system of discrete venting in the ceiling, soffit, and roof in which the warm air is removed from the rooms by the very convection currents it creates. The eaves overhang keeps most of the sun off the walls, and the light pastel paint reflects a lot of the heat too.
Now in our second hot season, we have never felt the need for any aircon, other sophisticated ideas, or imported methodology. After returning yesterday from 4 weeks in the bloody cold (12°C), damp UK, he still does not find his Thai home uncomfortably warm at any time. Maybe he is just a tad more adaptable than most; either that, or simply forced by poverty to improvise :wink:

This thread really belongs in this forum:


http://coolthaihouse.com/forum/viewforum.php?f=22

where other readers might benefit from it.
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Postby chiangmaiexpat » Tue Jun 10, 2008 8:34 am

Jazzman,

Thanks for the praise. :D

I am not a great fan of air conditioning either. In our last two homes we haven't used aircon except during the April peak days. In my current home, I don't have aircon in my office. I feel quite comfortable at temperatures between 25 and 30 deg. Celsius. It gets uncomfortable for me when the temperature exceeds 33 deg. Celsius which is rarely the case. Our new home, the one we are building now, is equipped with ceiling fans and lots of windows in every room which will hopefully eliminate the need for air conditioning.

I am not too worried about passive heat gain through the walls. The lion share of solar heat gain is through the roof, and hence, it possibly pays to insulate the roof first. A combination of proper orientation, reflective foil under the tiles, adequate roof ventilation, and a light/reflecting roof tile colour probably does the trick.

Cheers, CMX
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Postby grant » Tue Jun 10, 2008 8:51 am

chiangmaiexpat wrote:Jazzman,

Thanks for the praise. :D

I am not a great fan of air conditioning either. In our last two homes we haven't used aircon except during the April peak days. In my current home, I don't have aircon in my office. I feel quite comfortable at temperatures between 25 and 30 deg. Celsius. It gets uncomfortable for me when the temperature exceeds 33 deg. Celsius which is rarely the case. Our new home, the one we are building now, is equipped with ceiling fans and lots of windows in every room which will hopefully eliminate the need for air conditioning.

I am not too worried about passive heat gain through the walls. The lion share of solar heat gain is through the roof, and hence, it possibly pays to insulate the roof first. A combination of proper orientation, reflective foil under the tiles, adequate roof ventilation, and a light/reflecting roof tile colour probably does the trick.

Cheers, CMX


CMX,

I'm curious to know what temperature your office is normally at between the hours of 1-4 PM without air con. I work with a an Apple Powermac dual processor computer and it's 6 fans begin to blow quite strongly at around 28-29 degrees room temp so I'm forced to turn on the air con when the temp in the room gets to that level (which is nearly every day before noon as I rent a house with no insulation whatsoever).
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Postby chiangmaiexpat » Tue Jun 10, 2008 10:50 am

My office is on the northwest side of the house. Likewise no insulation whatsoever. Temperatures usually don't exceed 30 deg. Celsius. In the winter, it's often 20-25 deg. Celsius (I have a thermometer right at my desk). I was also concerned about overheating my PC, as the machine gets noticeably hot during the day. I have an Intel Quadcore with all four processors constantly at 100% load, since I am running BOINC. However, the machine braved the tropical temperatures quite well so far. Even in April.

Cheers, CMX
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Postby jazzman » Tue Jun 10, 2008 11:56 am

It must be the poverty then - the only thing contributing to the ambient temperature of my office is a four-year-old single-core G4 :wink:
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Postby chiangmaiexpat » Tue Jun 10, 2008 12:38 pm

Never mind. I've been using an even more ancient "coal fired" Pentium IV until December last year.

Cheers, CMX
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Postby grant » Tue Jun 10, 2008 12:39 pm

jazzman wrote:It must be the poverty then - the only thing contributing to the ambient temperature of my office is a four-year-old single-core G4 :wink:


But far more energy efficient . Once those fans start blowing on my G5, the temp in the room begins to heat up noticeably. Heat generation was the main reason Apple switched to an Intel chip from the IBM chip a few years ago. But we are way off topic.
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Postby Jack » Wed Jun 11, 2008 4:33 pm

Ians, I can give you some non-quantitative results from our house. I'm building it with a double concrete block wall with 2" of fiberglass insulation in the void. I have an initial section where part of the inner wall was built but doesn't yet have insulation or render on either surface. Today was a fairly sunny day - the first in a while - and at noon, after the east wall had been in the shade of the eaves for an hour or so, the outside surface of the exterior wall was still very warm to the touch. The void side surface of the exterior wall was somewhat warm. The room side of the inner wall was noticeably cooler than the void side of the exterior wall. I was just using my hand so nothing too exact.

I tried to see if the room side of the inner wall was warmer than the nearest inside room wall and I think I noticed a small difference but I wouldn't swear to it. With the insulation added I'm sure there won't be any difference at all.
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