Can we talk about heat ?

Hallo everyone. I am new here, living in the southwest of France.
I would like to begin a discussion about how to have a cool house
when temperatures arise and stay hot even during the night ?

Cob houses in the desert are great because at night the temperature
goes down, sometimes around 50°F, but a couple of years ago in
Vancouver, it stayed high high for weeks with not much lower temperatures
at night,  and it does so as well here in the south of Europe as well.

So my question is, should I go thermal mass or insulation.

Should I build a classic cob house ? Some people say that when the heat
stays high 24h/24h, the cob house will end up being like an oven !

These same people say that I should in such a case go light on thermal mass,
perhaps only some inside walls, and do the exterior walls of insulated stuff
like clayslip and woodchips ?

I assume that there must be some exeprience about this somewhere.

Have a wonderful day, here in France it is already past bedtime
Raymond

Hey Raymond,

Welcome to Permies!

In climates without big daily temperature swings I like to use materials with higher insulation values like light clay straw/slip straw or straw bale.

I think the big key is to orient your house so the majority of your windows are on the sunward side (south in the northern hemisphere) with smaller windows,  located higher on the wall on the north side of the house and no or well shaded windows on the east and west sides.

Next, shade your walls and windows with a substantial roof overhangs. In a warm climate in the northern hemisphere I don't won't the sun coming through the windows on the south side of my house until November. In your climate September or October might be better. On the subjects of roofs, venting the roof deck or building a double roof is also a really good passive cooling strategy.

Put a lot of thermal mass inside the house in the form of earthen floors and trombe or cob interior walls. It the winter with sun streaming in the windows the mass will absorb heat and in the summer it will hold on to the cool under the shade of the roof.

Earth sheltered is also a really good option with some caveats that we could discuss if you're interested.

In any case I would make a contingency plan for installing an air conditioning system. With a mini split system that involves planning for a place to put indoor evaporator unit and outdoor compressor unit and running wiring for the unit. If you'd don't need it. Fantastic! If you do it won't require any major remodeling.

Dear Aaron.
Thank you so much for explaning all this to me, a newcomer and beginner.
All I have today is what I read and some earth and straw workshops.
In 2025 I hope to beging my house, only 66 years young !

Today I live in a concrete house with hugh windows and bays east west,
the opposite of what you and everyone recommends
However the west wall is shaded by big oak trees and the eat has a veranda so
the sun does not hit the inner walls.

However I took away the ceiling when we moved into the house and I changed the
roof insulation with now 12 inches of wood fiber to protect agains the heat.
The double roof, yes, that is a very good idea, thank you.

The funny thing is that when I read about all these very ecological houses on the net,
during a heat swell, they talk about 79°F.
This is what I have in my home today with 100°F outside this week.
So it seems to me that we cannot do much naturally to improve the temperatures
when the night stays around 70-74°F.

From what I understand, the real heavy beautiful cob is only good for areas
where the night temperatures drop substantially. I also did a rammed earth
workshop but althogh quite easy technically, it is heavy work.

I wonder if I should make my futur houses walls of slipclay and woodchips
20 inches thick to give it the best ? or would that not really do anything agains
the summer heat ?

So you are right from what I also read about your recommendations for est/west,
openings to the south for the winter however, I am not so keen on large overhead
protections because you loose the light into the house during the in between seasons.
I would rather come up with some temporary shading structures for the only 3 months
of the summer here, mid-june to mid-september, and then let all the sun into the house.
The large overhead protections will interfere with sun striking into the house in late
april-may and late september-october.  

Another idea I have is to install for best light inside the house during the off season,
big west and east windows and also big roof windows, VELUX and construct during
the hot season some custom made "double insulation"
to put on top of these windows and roof VELUX because the standard outside VELUX
shade is not efficient enough and also very expensive.

Thank you for the air conditionning recommendation but oh, I don't like it
but you are right, this might be an option when getting older

Perhpaps I should just dig a big underground room in the garden where I can go
and stay when afternoons goes into the 120°F, luckily we are not there yet !

And you are right, the only natural cooling possibility that we have is the
underground but the land is flat where I will build so I think that this is not an option,
otherwise it must be a great option to put parts of the house underground.  
The canadien or provencial well would be another possibility
but it is rather complicated to maintain, and I wonder about humidity coming up
into the house from such a well as this installation gets older,

Thank you so much for your input, this is a great forum.

Best Regards, Raymond

Raymond Liljeros wrote:
Today I live in a concrete house with hugh windows and bays east west,
the opposite of what you and everyone recommends
However the west wall is shaded by big oak trees and the eat has a veranda so
the sun does not hit the inner walls.

Yes, siting can make a big difference. We have a 100+ year old oak tree on the west side of our house that provides really good shade in the afternoon.

Raymond Liljeros wrote:
The funny thing is that when I read about all these very ecological houses on the net,
during a heat swell, they talk about 79°F.
This is what I have in my home today with 100°F outside this week.
So it seems to me that we cannot do much naturally to improve the temperatures
when the night stays around 70-74°F.

Earth sheltering is the only option I know of that can keep a house naturally cool in warmer climates. Generating air flow has limited effectiveness when outside air is hot and humid.

Raymond Liljeros wrote:
From what I understand, the real heavy beautiful cob is only good for areas
where the night temperatures drop substantially. I also did a rammed earth
workshop but althogh quite easy technically, it is heavy work.

In warm climates cob is really useful inside your building envelope. I agree, it is heavy work, that's why I generally tend toward light clay straw/slip straw

Raymond Liljeros wrote:
I wonder if I should make my futur houses walls of slipclay and woodchips
20 inches thick to give it the best ? or would that not really do anything agains
the summer heat ?

I heard it recommended that light clay straw walls not be thicker than 12 inches because it will begin to rot before fully curing. A 20 inch thick clay and woodchip wall would essentially be cob which if well shaded would work tolerably well. I know some professional natural builders who built a cob house near me with 24 inch thick walls and on hot days interior temperatures will still rise into the mid to high 70s. Most heat gain comes via your roof so I would really focus on that.

Raymond Liljeros wrote:
So you are right from what I also read about your recommendations for est/west,
openings to the south for the winter however, I am not so keen on large overhead
protections because you loose the light into the house during the in between seasons.
I would rather come up with some temporary shading structures for the only 3 months
of the summer here, mid-june to mid-september, and then let all the sun into the house.
The large overhead protections will interfere with sun striking into the house in late
april-may and late september-october.  

Here is a discussion we had on Permies about passive solar design I think you'll find useful
https://permies.com/t/174169/Passive-Solar-Design-Roof-Overhang

Raymond Liljeros wrote:
Another idea I have is to install for best light inside the house during the off season,
big west and east windows and also big roof windows, VELUX and construct during
the hot season some custom made "double insulation"
to put on top of these windows and roof VELUX because the standard outside VELUX
shade is not efficient enough and also very expensive.

I think skylights are problematic because they are difficult to weather seal and like you said expensive. East and West facing windows with awnings would work. In our cabin we have long skinny windows mounted just below ceiling height along the whole north and south sides of the house that bring in a fair amount of light.

Raymond Liljeros wrote:
And you are right, the only natural cooling possibility that we have is the
underground but the land is flat where I will build so I think that this is not an option,
otherwise it must be a great option to put parts of the house underground.  
The canadien or provencial well would be another possibility
but it is rather complicated to maintain, and I wonder about humidity coming up
into the house from such a well as this installation gets older,

It's better for drainage and other logistics if you build the house above ground and build up a berm around it. That's how we built our partially earth sheltered cottage.

Raymond Liljeros wrote:
Thank you so much for your input, this is a great forum.

You're welcome. I agree.

Thank you Aaron for all this information, so kind.

The discussion about passiv solar design if very interesting.
It is all about negociation of what you essentially seek for.
I guess you cannot have the cake and eat it on the same time !

Skinny windows mounted just below ceiling height along the whole north and south sides of the house
that is a great idea. In our house today I installed with a very courageous mason a window just below
my roof on the south side. 2 triangles and yes, during the winter season it is amazing how much light
and also warmth when sunny, this window lets through.

Your earth sheltered house is a very good idea but after showing it to my wife,
hmmm, she says I would have to find someone else to live with in such a house
but this is obviously a very good idea. Perhaps I can find a land up in the
Pyrénées and buld a tiny house like this and go there when it is to hot
I actually have a friend who is looking into this option.

Another a bit crazy idea I have had, I like experimenting

is to create a wall heating system and then during the winter  season
I could let the plastic water tube run about 100 yards inside a freezer ?

I wonder how that would come out ?
I am sure someone somewhere tried it already.

is topic can be very large.
It is well covered in many topics.
I suggest you get an A4 note book and note down the  ideas you like.
Double roof is great I have detailed them under safari rooves.
iN THE MIDDLE EAST BUILDINGS HAVE SHDED WALLs, wind towers and ponds from which moisture can flow into the house when humidity is low.
Most of these are detailed in this site in separate topics.

I can't really offer anything as I haven't done any work like this.  I'd think your concerns about roof overhang shading too much could be alleviated with use of retractable awnings over the windows so they provide shade in the hottest part of the year and let sun in the other seasons.

I had an aunt and uncle in Dax, not too far away from you.  They've both passed on and I haven't met most of my cousins (the youngest came to visit in Canada one year and the eldest had emigrated to Canada, but I never met him and I'm not sure if he's still here or not).

Good luck with your project.

As you search for options that will work, I want to mention a couple of my favorite vines.  Passionflower and hops.  These die to the ground when winter comes.  They are perfect for summer shade and winter sun.  A plus to shade from a vine over a solid structure, or shade cloth (which some folk still chose despite it being a petroleum product, or maybe there is a natural fiber alternative?) is that leaves transpire, and that is a cooling process.  Leaves also allow breezes to pass through.

A perennial that dies to the ground seems ideal to me because the branches don’t remain through the winter.

A person might have to search for other options in different climates but these both grow well in temperate climates.  

In the fall when the vines ho dormant, you can just take the leafy stemmy mass and use it for mulch or chicken bedding or goat fodder or something else entirely.  It is a good idea to figure out what you might want to do with it, and keep that in mind as the season progresses and let that guide your choices what you use to support and guide the vine’s growth.

I guess one drawback would be if you also need wind protection in winter.

A second post for a second idea.  I just heard of this recently, the use of phase change materials in passive cooling.

Of course the building industry will come up with proprietary and expensive options but for permies in climates with lower humidity there’s moisture.

When a material changes phase (solid liquid gas) it absorbs or releases heat energy.  The article I read was suggesting adobe (probably true of cob, earthen plasters , rammed earth, compressed earth blocks, probably not sealed earth floors).

What was presented was the idea that in the night and morning when the temperatures drop, the humidity rises (more water vapor in the air).  The water vapor is absorbed by the earthen materials, and changes phase from gas to liquid, releasing its latent heat.  As the day heats up, the humidity in the air decreases.  The moisture in the earthen materials evaporates, absorbing atmospheric heat energy as it changes from liquid back to gas.

I had never thought or heard of this before.  I never considered the water moving back and forth, in and out of earthen materials, or that it would be changing from liquid to gas as it did so.  I can see that if all this is true, it will allow lots of experimentation and successes for permies.  One question I have is whether it could be useful in a humid climate where humidity doesn’t fluctuate with the daily temperature cycles…. But I am puzzling whether a dehumidifier could function as a cooling device, and so on.