Because today is Friday:
The same problem with triple glazing of the windows. It retains heat better but with sun the interior is also not heated up.
The solar heat gains with triple glazing are indeed lower than with double or even single glazing. However, the reduced gains are more than compensated by the saved losses. In summer, it even helps a bit to prevent excessive heating.
With concrete it would stay cooler inside in summer and you might even be able to do without air conditioning
ONLY concrete heats up very quickly in summer and the house would also heat up quickly when exposed to sunshine in summer, because any heat arriving from outside is quickly transferred inside. You can do without air conditioning with intelligent design, regardless of concrete. This includes roof overhangs, window orientation and size, and for planning mistakes there are venetian blinds.
It could well be that in the end the difference when it comes to heating costs is not so big
The difference between NO insulation at all and today’s new build standard is very large, no matter if made of concrete, wood or clay. Today’s standard or the current requirements for ancillary buildings and their energy demand and the theoretical calculation of this may be somewhat exaggerated, but a building made purely of concrete is pointless in every respect.
? Maybe someone here lives in a concrete house without insulation
Without asking each individual, I’d bet that no one does. “Modern” living (warm, without mold and frost on the walls) is not possible in a pure concrete building (above ground). Due to poor thermal protection, the walls inside would be freezing cold, which would cause water to constantly condense out of the air and freeze in winter. You would have to heat enormously to counter that. Additionally, a huge air exchange would have to be ensured to remove moisture and minimize condensation, which again leads to increased heating demand. This is clearly seen in old brick buildings without insulation made of 24cm solid bricks. There you have to ventilate and heat a lot to avoid problems with condensation and mold. To achieve the same thermal protection as the 24cm bricks, pure concrete walls would have to be about 70-80 cm thick—and that would still be rubbish.
That means vapor-permeable
By the way, concrete is a first-class vapor barrier. Nothing is vapor-permeable; after 20cm thickness, almost nothing passes through.
Or are the exposed concrete houses perhaps made of lightweight concrete?
That was already answered. They might have concrete on the outside or inside, but there is always insulation in the middle.