Passive home construction

Any story related to building in the LOS, whether everything turned out hunky dory or not!

Moderators: MGV12, BKKBILL, fredlk

Passive home construction

Postby Ians » Fri May 09, 2008 11:59 am

Hi guys and gal's. I'm currently undertaking a study of building a new home in the Phitsanulok area - extremely hot as well as hot and humid at various times. I am looking into the best construction method / materials for building to give something that is not like an oven during the day and into the night.

I will probably settle on suspended concrete slab, concrete block (the large ones) walls to make use of the insulating effect of the air space, very wide verandahs all-round (typical out-back Australia) high ceilings and lightweight roof material, probably colourbond or similar and insulated with aluminium foil.

To finish off my study, I'm looking for information / comments/ research on ventilating the concrete block walls (outside) to increase the insulating effect by thermal airflow thru. the block cavities.
If anyone has any info they wouldn't mind passing on I would be grateful.
User avatar
Ians
 
Posts: 926
Joined: Thu Apr 24, 2008 11:38 am
Location: Phitsanulok

Postby Nawty » Sat May 10, 2008 4:59 pm

Ventilate the roof space also, get rid of that hot air up there and also a spray on foam product I have found to be very good, also adds strenght to the roof. Bit it is around 300 baht per sqm and sprayed either directly under the roof to an inch thick, or there is the same product but it sits on the ceiling and is around 3 to 4 inches thick but does not harden like the foam sprayed on the roof itself.
User avatar
Nawty
 
Posts: 804
Joined: Mon May 07, 2007 12:23 pm

Postby Ians » Sun May 11, 2008 7:10 pm

Nawty, thanks for the reply. My intention will be to put reflective foil under the roof sheeting, with nothing on the upper face of the ceiling, insulation on the ceiling only retards cooling below the ceiling once the roof space cools after sunset.

My interest is in effective cooling of the single cavity within the concrete blocks by encouraging air flow thru this area --- I haven't dismissed using a two block configured wall with a 3" or 4" cavity which in itself should be an excellent insulator - this is the area for which I am seeking information.
User avatar
Ians
 
Posts: 926
Joined: Thu Apr 24, 2008 11:38 am
Location: Phitsanulok

Postby dozer » Mon May 12, 2008 8:20 pm

To finish off my study, I'm looking for information / comments/ research on ventilating the concrete block walls (outside) to increase the insulating effect by thermal airflow thru. the block cavities.
I've seen many double wall cavity constructed houses, also many with the large concrete blocks, but have never seen such a ventilation system. I can see what you are getting at but think the effort may be counter productive as any ventilation system will let the hot air in and cooler air out. Further, I did a google search to compare the standards overseas with block wall construction, and outside of weep holes which have a different purpose could not find any use of such a ventilation system.

Would be interested in what you find out.
dozer
Site Admin
 
Posts: 1940
Joined: Tue Mar 15, 2005 4:21 pm

Postby Ians » Tue May 13, 2008 9:27 am

Hi Dozer
Thanks for your reply, I take your point re hot air replacing the cooler air in the cavity and could well be valid during the daytime. As I am thinking of venting the cavity into the roof space, this system might have a benefit once the heat of the day has passed and cooler air can pass thru, hopefully to reduce any residual heat within the structure gained during the day. Therefore it might become an exercise of balance- does the night cooling effect exceed any increased heat gain during the day.

Likewise, after an extensive search I cannot find any reference to this approach other than stack ventilation which assumes the air being encouraged to flow thru any structure is cooler than the area being cooled, for example - the highly efficient thermal oven (roof space) now so popular with modern construction in Thailand.

Anything I come across worth reporting I am more than happy to share with all in the forum. I have started to accumulate a vast amount of info and once I sort out the good from the BAD and ridiculous I will list the websites/links etc.
User avatar
Ians
 
Posts: 926
Joined: Thu Apr 24, 2008 11:38 am
Location: Phitsanulok

Postby Nawty » Thu May 15, 2008 8:33 pm

I put these vents into our roof, on the north and south sides so we get a strong flow of hot air out of the roof.
Attachments
IMG_6610.jpg
User avatar
Nawty
 
Posts: 804
Joined: Mon May 07, 2007 12:23 pm

Postby Ians » Thu May 15, 2008 10:19 pm

Thanks Nawty, the vents look good and should serve well to keep the roof space cooler.
User avatar
Ians
 
Posts: 926
Joined: Thu Apr 24, 2008 11:38 am
Location: Phitsanulok

Postby jazzman » Sat May 31, 2008 4:31 pm

In cavity walls - which is the standard UK construction for houses - the ari space is often filled with self-expanding foam which:

- prevents any air circulation, thus reducing the incursion of warm air into the gap.
- vastly increases the insulating properties in much the same way as any foam insualation in any application, including styrofoam coffee cups. Bree (cinder) block also works the same way.

For a colorbond roof, Nawty's solution with foam is very effective.
jazzman
 
Posts: 2161
Joined: Wed Dec 06, 2006 9:11 pm
Location: Thailand

Postby Ians » Mon Jun 02, 2008 2:17 pm

Jazzman, thanks for the comment - the self expanding foam in a cold climate is a great idea, however, my thoughts on its use in Thailand is negative. Sure it keeps some of the heat out during the day but transversely it then retains heat during the night - a time when you need to reduce any heat stored within the house itself and walls to the cooler (relative) outside temperature.
User avatar
Ians
 
Posts: 926
Joined: Thu Apr 24, 2008 11:38 am
Location: Phitsanulok

Postby Nawty » Mon Jun 02, 2008 4:37 pm

I would not be putting it in wall cavities, but roof is fine and then combine it with ventilation.

I will have to climb up and feel my roof under the foam after a few hours of sunset and see what the temp is.
User avatar
Nawty
 
Posts: 804
Joined: Mon May 07, 2007 12:23 pm

Postby Ians » Tue Jun 03, 2008 7:49 am

Please note - in my previous post I should have used inversely not transversely - maybe the brain needs some ventilation.
User avatar
Ians
 
Posts: 926
Joined: Thu Apr 24, 2008 11:38 am
Location: Phitsanulok

Postby thaifly » Tue Jun 03, 2008 12:16 pm

Ians wrote:Please note - in my previous post I should have used inversely not transversely - maybe the brain needs some ventilation.
GIDDAY IANS its the thaifly from mae rim...got a good giggle with your BRAIN VENTILATION quote ... the thaifly needs the same at times...but generally heinkens do the trick.....its a very airy gidday to all ITS THE THAIFLY FROM MAE RIM
thaifly
 
Posts: 825
Joined: Thu Mar 15, 2007 8:29 pm
Location: mae rim...chiang mai

Postby jazzman » Sun Jun 08, 2008 9:09 am

Ians wrote:Jazzman, thanks for the comment - the self expanding foam in a cold climate is a great idea, however, my thoughts on its use in Thailand is negative. Sure it keeps some of the heat out during the day but transversely it then retains heat during the night - a time when you need to reduce any heat stored within the house itself and walls to the cooler (relative) outside temperature.


Insulating material works with the same effect for both cold and heat; if installed correctly, the need to exhaust any accumulated heat at night will prove superfluous.
An extractor fan in the bedroom, would however do this in a few seconds if need be.
jazzman
 
Posts: 2161
Joined: Wed Dec 06, 2006 9:11 pm
Location: Thailand

Postby Ians » Sun Jun 08, 2008 3:38 pm

Jassman - still have to disagree with you on the insulation within any wall cavities in a high temperature environment ie, Thailand. During the night when the "outside" temperature has reduced any latent heat in the inner wall of a cavity construction would be insulated by the foam, therefore to cool this wall it becomes necesary for the heat to be passed into the "room" before it can be vented to the outside either by natural ventilation or an extractor fan - this I guess is Ok but I would prefer to have natural ventilation within the cavity which I am now looking into ie, take in "cooler" air at the bottom of the cavity and vent it at the top - this could be into the roof space to utilise the roof venting system.

Of course you comments are most welcome and considered as this is how we expand our knowledge.
User avatar
Ians
 
Posts: 926
Joined: Thu Apr 24, 2008 11:38 am
Location: Phitsanulok

Postby jazzman » Sun Jun 08, 2008 10:43 pm

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 and thus whether any measures are worth the design time and constructional expense. Of course, if budget is not an issue, the results of the experiment would be most welcome.
jazzman
 
Posts: 2161
Joined: Wed Dec 06, 2006 9:11 pm
Location: Thailand

Next

Return to Your Building Story

Who is online

Users browsing this forum: Bing [Bot] and 1 guest