There are some solar panels that are installed on light walls of any materials which can produce electricity and the other group consists of pipes and warms up water. Also some clear solar panels which are installed int he window pane.Aside from that, If you are talking about the external walls,they can be light-weighted if you place your thermal mass in the floor. Your wall can be a light glass or a wooden wall with big windows, you still can save the heat in the mass in the ground and have it reflected internally at nights so it does not limit your design regarding the wall material.

But floor thermal mass does not result exactly in the same.. 

Thanks first of all! Thing is.. active solutions are not a possibility in this case. The design needs to be able to achieve habitable and comfortable values relying on passive (bioclimatic) approaches only. (Need to remember that in some cases , solar panels , wind mills or other are not considerable options because of the site location , economy , or others) So the design only concerns the basics “going back to basic” idea

When asking, I meant.. if you design in a hot climate, it is true you can implement a good thermal mass floor ( no insulation and full use of the geothermic part) but I am not sure if one used wooden walls, if it is enough the floor is a good (heavy) construction. I am trying to understand if, apart from making floor a good thermal mass, if it is possible to provide some kind of good result with lightweight solutions. The outside skin and the walls should be easy to disassemble and heavy construction such as brick or block walls are the opposite of easy in terms of destruction and recycle of materials used. If you think about a structure and the walls are a second skin, second layer part form structure, can a light weight wall achieve the same as a heavy weight?

Maybe you should look for construction materials that can absorb more heat(dark colors) and keep the heat for a longer time as they are in nature good thermal materials in less volumes and masses. 

yeah! i was hoping someone would know more than me or have advices on what to read.. haven’t found a lot of information yet , but thanks

You are welcome. If no one else knows about it and you could not find anything in internet, then it is a good thing, means you have an original creative idea which you can develop and register ,have a look at this website

http://www.ideaconnection.com/

I dont' know about insulation, but considere that if you build in heavvy wood you can create lasting carbon magazines that can be sold in the carbon conservation market.

You could search for thermal insulation between two prefab walls - the insulation is typically an air space with some additional fibre wool (syntheric ort natural). However if you are looking for a design that can be used worldwide. in large numbers, it has to be cheap and sustainable to make, which means using local materials as far as possible.  For instance, the most sustainable house in rural india is the old mud hut, that provides excellent thermal insulation - cool in summer, warm in winter. But, for a house with prefab sheets, one can use crop reesidues/bamboo/palm fronds/whatever organic matter locally available in the space between two sheets (outer n inner walls), thereby minimizing costs of transportation of this material. 

Dear Amartya

So you think that even though using lightweight walls of wood , if the gap is filled with those materials, it could achieve an play value? I need to simulate… thing is.. is warmer climates (not arid) such as in Portugal , double brick walls are used with very little insulation (that helps keeping cold out) and air gap.. but brick has high thermal capacity.. the same as adobe in india..

I do know that in Malaysia.. the need for good thermal mass is not the same because day and night temperatures don’t swing so much, bamboo or even (shigeru ban’s paper tubes) can be used… but in hot climates where temperatures do swing a lot from very hot to very cold.. can prefab wooden elements with that gap achieve the same value..?can it be achieved if the wood is denser?

Dear Negin

I am sure I need to find it.. maybe it is because somehow it is not possible.. I am not sure

Dear Franco

Can you explain to a bit further? is that related to thermal mass ,material thermal capacity?

Hi Mafalda, i don't know much about wood. Prefab walls in India are made from concrete. Wooden walls are quite often used in the US which has a range of temperature extremes. Perhaps the best bet would be to start off looking online at sites like http://www.diy-prefab.com/  that have experience in using wood for prefab. 

US also uses a lot of other materials, but i will definitely look at US example! Thanks!

Actually, what about Phase-change materials? That could be an option

You may wish to investigate air-entrained concrete as an insulating material in hollow timber walls.  The material can also be used structurally but only under controlled conditions because of its lightweight properties.

I appreciate the suggestion Stephen! I will look for it

Thing is, concrete cannot be disassembled easily the same way prefab wood solutions can, right? More than insulating, it should be able to act as good thermal mass and still be easily disassembled. I am thinking that maybe a combination of thermal mass in the floor and inside layer of the wall and outside wood, might be a way to deal with it?

mafalda you should look at 'wood wool cement boards'. easily assembled and dissembled, good insulation value, good strength both compression and flexure, I didn't check the heat capacity, but for sure it would be more than wooden boards

Thank you Adil!

I will check that also! Maybe if combined with brick, it can assure the thermal mass and the easy assembling /disassembling part

Depending upon the situation you could go down the route of mass produced panels made of 2 X 4 studs covered with OSB and some form of foiled backed rigid insulation in between the studs. The practice has been used extensively in the USA and the UK, the difference is the UK market require further protection from the damp wet conditions. For Saudi Arabia the solar radiation will breaks down the insulation, the OSB can be impregnated with some form of fire protection so I can't see why additives can't be changed to add protection from radiant and solar heat.  The simpler the solution the more cost effective it will be and all of the materials used are virtual 100% recyclable, the issue would be more of overcoming the cultural ideologies were brick and concrete is strong and last a life time and timber is only a temporary solution. 

You are of course right, ..timber is temporary, but in a way, in this case it is supposed to be. The main core should be rigid, durable, fixed and long lasting while the “outside” or second skin - the considered wood layer- is intended to be replaceable , assembled and disassembled easily and temporary (at least a lot more temporary than other heavy construction solutions such as brick) 

would brick+ wood outside be a better alternative than brick + brick.. in terms of allowing a good thermal mass and a replaceable layer? . Saudi Arabia should depend on little or no insulation, isn’t that right? as far as my simulations in Bsim, insulation bigger than 5cm wouldn’t be so good, once it wouldn’t allow the heat to go out, being too tight for the climate.. but an air gap could work in between brick and wood.. 

it is common sense that hot dry requires good thermal mass due to temperature swings.. but wood is not the preferable material for outside. A solution is to have thermal mass for the floor.. but what is the best solutions for walls?  and of course… if wood or prefabricated solution were to be used, then there is of course always the matter about cultural heritage and social sustainability not being followed . Using prefabricated wood elements for the outside skin would allow mass production and cheaper , faster production and replacement, but 1:is it the best solution to be used to achieve this? 2. is brick + wood wall construction allow the inside to achieve values that would be comfortable (indoors) ? is traditional construction answered in any way?

Would , textile - redrawing inspiration form Moroccan tents , Bedouins tent or other- and also from experiments such as the one from Walter Unterrainer’s Single-Family House in Feldkirch, work in a hot context for the outside skin? Not really only as a tent but as a cladding material? 

Thermal mass in floor/roof if lightweight or medium weight walls. A building is a system and needs to be designed as such. You can reduce daytime peak internal temperatures by providing thermal mass, and if you can cool the mass at night that's even better. And/or you can shade the building to prevent it gaining heat in the first place, and/or provide evaporative cooling if daytime humidity is low enough. There is plenty of design advise on all this.You should check your solution works by carrying out computer thermal modelling, preferable dynamic thermal simulation. Also beware of choosing detailed solutions (e.g. phase change materials) before understanding the whole system: climate, microclimate, building, occupants needs.

Mafalda, you may wish to investigate air entrained concrete that is engineered to be manufactured and delivered in units, a technique pioneered in Sweden in the 1980s.  These units range in size from modular blocks to panels of standard (usually 100mm) thickness and are assembled with adhesive rather than cement mortar. They have good acoustical properties and better thermal mass than airspace or batts.  But they may have to be imported specially for some locations.

on Friday i heard of Western Australian high-rise residential contractors using reconstituted engineered polyurethane panels as fire, thermal and sound insulation but i have not yet researched this relatively new (to us here in Perth) material.

Simon, I have done many simulations concerning temperature, co2 levels, daylight , relative humidity… in Bsim.. 

I know it is a system and for that reason openings, shading, color, materials and others, need to be taken in consideration, but of course if you isolate the role of the envelope (since it is one of the most important parts) then its when I am trying to get the best solutions and balance for sustainable and feasible values

Stephen , I will definitely consider that option also! PCM are a little in the beginning and the material available is not completely conclusive, but I find it an interesting approach , if not to use, at least to reflect upon

Thank you

I guess light weight insulation material that has higher U value will consequently be more influential by the external condition and not necessarily a good thing--perhaps overheating in the day time then rapidly cools down at night. 

Dear Mafalda,

Lightweight building envelope doesn't reppresent the best solution in hot climate.

Nevertheless you can work with other strategies in order to prevent overheating and the indoor swinging temperature:

- Design shading systems

- Adoption of ventilated façade

- Control the natural ventilation and nocturnal free cooling

- Store the energy in other indoor components (floor, ceiling, furniture)

- Adoption of PCM (phase change materials) to store a large amount of energy

I hope that this short list of suggestions could help you in your work.

Precast glass fiber reinforced concrete (GFRC) is going to be about the best material that's reasonably economical. It's more expensive than regular concrete but significantly stronger, thus enabling thinner panels for the same strength.

Mafalda Melo Oliveira ...... Good question..

Based on the structural design... Yes Its can.. but the applicability of achieving that is the important issue...

Please share me the best answer might you trust...

Regards…