Light and heat ...

Heating, insulation, ventilation, VMC, cooling ... short thermal comfort. Insulation, wood energy, heat pumps but also electricity, gas or oil, VMC ... Help in choosing and implementation, problem solving, optimization, tips and tricks ...
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Grelinette
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Light and heat ...




by Grelinette » 30/06/19, 12:07

Hello,

The heat wave of 2019, the one we are experiencing at the moment, more serious than that of 2003, raises awareness of what to expect in a more or less near future. This heat wave also opens our thoughts on our building construction techniques that show that we have not anticipated enough in terms of climate and we must now review many things.

I just heard an analysis of an architect which explains that "the fashion", until today, was to make important entry points for light in buildings: large bay windows, windows open to the roofs (velux), transparent brick walls, etc. , to make the interiors of buildings brighter without having to systematically turn on the lights ...

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More natural light also says heat, and suddenly we compensate for air conditioning on all sides.
However, this is not enough and consumes a lot: we must review the principle, a little like our old in the warm regions that made houses with very thick walls and small windows.

In short, the question is how to get in the light and stop the heat in summer, and let it pass in winter.

For example, the famous Velux are very pleasant skylights in winter become sources of heat unbearable in summer, especially for rooms under roof!

In the same way, traditionally roofing tiles are red, gray, black, not to mention the waterproofness of flat roofs that are often in dark coatings ... The simple fact of laying clear tiles, even white, would allow to lower the interior temperatures almost 10 ° ... But 10 ° are lost in summer we would like to win in winter!

For starters, can you imagine a window (velux, bay window, etc.) that will let in light and stop the heat?

Likewise, which materials can 2 have the opposite qualities of stopping heat in summer and letting it pass in winter?
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Ahmed
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Re: Light and heat ...




by Ahmed » 30/06/19, 13:54

It is easy to answer the first question, since light and heat are two rather distinct things: there are glazings that stop part of the infra-red radiation and let pass the visible spectrum (it is a matter of wavelength ).
The second is more difficult, because cold and hot are only two different things in our perception *, where physical reality only sees a more or less important quantity of heat ... The only selective trick that I see , it is the "cap" which takes into account (in our latitudes) the difference in height of solar radiation, but it is not by the effect of the material ... Perhaps it is then necessary to orient yourself towards a glazing which would be opaque or permeable to IR according to an electrical voltage which would be applied to it or not, on command according to the temperature differences between ext and int or at will ... However, this is the way open to technological outbids which it would be better to guard against.

* Our perceptions work by relative and not absolute appreciations: a hand dipped successively in icy water, then in cold water will judge it hot ...
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Re: Light and heat ...




by A.D. 44 » 30/06/19, 14:13

Hello,

Building a skylight on the principle of the wind tower (Iranian), combining high ventilation and light diffusion.
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Re: Light and heat ...




by to be chafoin » 30/06/19, 16:05

Indeed I was boasted these skylights that exist in the trade (Velux or other ...) without the Persian cooling ventilation system: bubbles and circles of glass (diffuser) attached to the ends of a reflective duct. roof light inwards. I have never seen such an installation and I do not know if it is so effective but it seems to me a priori a good idea.
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https://www.fakro.fr/toiture-produits-s ... e-lumiere/
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Re: Light and heat ...




by A.D. 44 » 30/06/19, 16:53

Re,

It's a proposition ... I do not know if the association (skylights - wind tower) exists or is already proposed ...

The skylight, I see it regularly in the amphitheater of the school of music and dance of our community of communes (without ventilation). It is both effective and enjoyable.

Think of a well of this type with mobile vents to create natural draft and ventilation.
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Ahmed
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Re: Light and heat ...




by Ahmed » 30/06/19, 16:54

It is the same physical principle that is used by the optical needle: a round plastic led light at the bottom of the guide, a central cross allows alignment with the tracing and then this round is replaced by the steel needle .. It is very effective and unstoppable!
http://www.leevalley.com/fr/wood/page.a ... &cat=1,101
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Re: Light and heat ...




by Christophe » 01/07/19, 14:19

Grelinette wrote:In short, the question is how to get in the light and stop the heat in summer, and let it pass in winter.


Uh I think we invented the blind (Venetian, adjustable) there is already a good time ... and blinds (not adjustable) are designed in the same way: reject the summer heat ... at the price of a drilled drop in brightness ...

We can not keep 100% of the summer light without the heat (except yes maybe with the skylights: but a part of the IR will necessarily pass and ... they are quite expensive) ...

So we would have to find a material that filters the IR by letting the light through ... filter UV we know how to do easily (simple glass) but the IR is apparently more complicated! This nevertheless exists in professional photography but at what height filtration and for high prices just for the opening of a goal ...

In more modern than the blinds, one could think of windows self polarizing chromatic photo (like sunglasses) but here too, at what price? And some of the light would be absorbed.

I just saw that there are films to stick for polycarbonate: https://www.luminis-films.com/films-pou ... _technique

Description for Polycarbonate Sun Protection Film - POLY-200x

This solar film for polycarbonate is specially designed to solve the problems of protection against heat, glare and UV on synthetic glazing. Thanks to its composition, this anti-heat film has the capacity to reject 89% of solar energy and assures you a pleasant temperature all the year round.

(...)

The outdoor installation of this heat-resistant film increases the efficiency of the film because it filters the solar radiation before it enters the glazing. The application of this type of adhesive on your polycarbonates allows to save energy by having much less use of air conditioning. In addition, it is also a durable solution to improve the visual comfort of the occupants. By reducing the intensity of the sun, this anti-heat film limits the glare of 84% by letting some of the natural light through. Finally, it filters 99% UV responsible for discoloration and premature aging of the skin.

It is a complete solution that protects individuals from the harmful effects of the sun on the well-being, health and efficiency of individuals while maintaining the pleasant properties of the glazing such as brightness and transparency to the outside. The installation of solar film on polycarbonate is particularly appreciated in the workshops and the professional premises made up of plexi, polycarbonate windows or other synthetic glazing. Indeed, it allows to maintain good working conditions thanks to a controlled temperature all year long.

(...)

Durability: 5 to 8 years for vertical application in Central Europe.


Uh I did not know that the UV bleached the skin ... it's not the opposite? : Cheesy:

It is clear that most of the light does not pass, it is not linear but not far. Indeed, according to the technical sheet:
POLY-200x.pdf
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We have: 89% of the thermal energy absorbed for 84% of the visible light absorbed (16% transmitted) ...

And it's not given to the m2 ... and not so good life ...

Other filter models here: https://www.luminis-films.com/films-pou ... ti-chaleur
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Re: Light and heat ...




by Christophe » 01/07/19, 14:23

Ahmed wrote:It is easy to answer the first question, since light and heat are two rather distinct things: there are glazings that stop part of the infra-red radiation and let pass the visible spectrum (it is a matter of wavelength ).


Yes they are glazing low emissivity, except that, generally (in the individual housing at least, on the skyscraper is less on), they are mounted in the other direction: to keep the IR inside the l 'winter... : Cheesy:

So I do not think the answer is so obvious ... but it all depends on the drop in brightness that we want to support ... today most people want everything for nothing: the benefits without the disadvantages ... It gets pretty painful ...
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Re: Light and heat ...




by Christophe » 01/07/19, 14:31

If not in skylights modern version, there is optical fiber ... see how it absorbs IR ... but I doubt that the price is affordable to illuminate an average room ...
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Re: Light and heat ...




by Christophe » 01/07/19, 14:40

Grelinette wrote:Similarly, which materials can 2 have the opposite qualities of stopping heat in summer and letting it through in winter? [/ B]


There must be a change of ownership in the material, since physically it is contradictory ...

An LCD glazing regulated on the temperature ...

A material that would opiate with temperature (it's usually the opposite but it must exist) ...

Chromatic photo glazing ...

The chromatic photo glazing seems to me a good compromise: it's passive and mastered for years on glasses but I have no idea of ​​the price per m2?

ps: the glass bricks that you watch should be banned for mounting on an exterior wall ... they are thermal crap at all levels ... and what is ugly ... they have almost not evolved since 50 years? (100 ???)
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