Hacker News Reader

>For example, we enlarged windows and doors, to the point were, standing behind one that's been cooking in the sun for a couple of hours, you feel the radiant heat a meter away from it.

There are window films that can block most of the light in frequencies which carries the energy and let the light from visible spectrum in, barely dimming the brightness and almost doesn't change the color.

I recently installed such a filter, I'm amazed everyday how the hot bright sun is so tamed once inside the house. Sometimes I open a window to let the full spectrum in just so I can put my feet on the spot of the unfiltered light and then on the filtered one and compare how hot it gets where the sun shines in full power and can barely heat once filtered. It feels like magic, like a winter sun that is bright but doesn't heat. The filter itself heats up like crazy, it even gets too hot to touch but heat transfer by convection doesn't do much.

My grandma lives in an old house built with thick stone walls with tiny windows. It stays naturally cool but I really like large windows. IMHO, the humanity has advanced enough to have large windows and still keep it cool. It's also good for the mood, some people like me really really like the sun and even the heat up to a point.

Mind sending a link to the film you purchased? I have a large hot window I’ve been thinking of doing this to

The particular one I bought is this one: https://dropovercl.s3.amazonaws.com/21fa0b29-7858-4233-b895-...

It doesn't seem to be a real brand, Bauhaus sells it and its made in Taiwan. I'm sure there are similar or better films out there.

proper architectural films with published specs (uv/ir rejection ratios, etc), not sold retail. at least i failed to find them

Generally speaking the surface receives about 1kw/m2. I’d love to see a spectral graph that shows how that kilowatt is distributed. How much visible light can you sneak for a very low amount of that energy?

I don't know the details but it worked out very well for me. It still lets some heating rays in but its much more manageable, some ventilation is enough now.

These photos shows how much the film dims the visible light: https://dropover.cloud/999162

The photo of the wall shows two areas, one area illuminated by the light passing through the filter and another small area illuminated by direct sunlight through the opening.

It's a window in a small room. The window has a top-open position which provides enough ventilation to take away heat that still manages to get in. Previously, this room was getting unbearably hot and now is much better(still hot on days with no wind though).

According to Wikipedia, 43% of the sun's energy at the surface of the earth is visible light (https://en.m.wikipedia.org/wiki/Sunlight#Measurement). So just blocking the other wavelengths would help, but I'm not sure it would be a "night and day" difference, so to speak. Daylight is several orders of magnitude brighter than normal indoor lighting, so I bet you could block 80-90% of visible light, as well, and it would still look really bright out while heating the inside significantly less.

The disadvantage of such filter is that you want to get unfiltered light inside in winter.

It's supposed to help with heating too because it would block(by reflecting or absorbing?) the radiation from inside. I guess I will find out about it in a few months. If it's too dark in the visible spectrum, that can be an issue though.

We have the same in the windows we replaced in our living room. We took the least visible (and hence least IR blocking) option, which reduces transmitted IR with 60%. The coating went up to 90% IIRC though at that point it was a very visible blue. Ours has just a slight blue-green tint.

The difference this summer has been striking. In our bedrooms which are on the second floor, the sun feels hot through the windows. In the living room I can barely feel it.

We're up north so our home is well insulated, hence the summer sun tended to overheat the inside.

It's amazing isn't it? How was the winter with the filters on, if you have been through the winter of course?

Not a full winter, but got most of last (installing living room windows in -15C is interesting). While of course it also reduces sun heat during winter, the sun is low enough during the winter that we only get maybe a couple of hours at best per day of sun. Given that most of the winter is cloudy or overcast to some degree anyway, we didn't notice the little heat we missed due to the IR film.

On the flip side, the glass we replaced was some 20+ year old two layer glass while the new were thick 3 layer stuff. They're vastly better insulating (heat and sound), so that alone was a huge plus compared to the old.

I have heard that if you install these filters on the inside facing pane of glass, the glass can crack as the heat builds up between the inside facing and outside facing panes of glass.

Have you found one that does not do this or do you have any comments about this risk?

Haven't had any problems so far. The film gets very hot, it's inside facing so I've touched it out of curiosity. I don't expect to have issues with it, unless the glass with the film does't have enough space to expand but my windows are European style UPVC so they are quite robust and well made. AFAIK there's an argon gas in the middle, must be well engineered and accounted for expansion.

This would make me nervous. Sure, things are holding up now, but what happens when that heat exceeds design tolerances on the seals? Does the warranty stand up if you have this film installed?

Serious question: could you selectively block invisible light on the way in and *visible• light on the way out? Because that to me would be an awesome window.

I don't think so, because light propagation is symmetric. If light can get in, it can get back out by reversing direction.

However, if you simply don't want to be seen by people looking in from the outside, there are still some options:

If the inside is much darker than the outside, light from inside is overwhelmed by light from outside getting reflected back (the operating principle of "one-way" mirrors).

If the window is covered with a grid that only has small gaps (e.g. window blinds), it's hard to recognize objects on the other side unless your eye is close enough to look through a single gap.

If the glass has a rough surface (i.e. frosted glass), light that makes it through is scattered in different directions, blurring objects that aren't very close to the window.

Various combinations seem possible. (Frosted glass window blinds?)

Good answer. Thanks.

In Australia, we have the opposite problem; houses are optimized for hot weather and are often too cold during the winter. Houses such as Queenslanders are designed to let air easily flow through the house and they are built on stilts which creates a cool area underneath the house; some houses even have gaps or holes in the flooring near some of the walls (e.g. for cabling; they don't bother sealing them). They often lack proper wall and floor insulation. Works great during the summer though.

I suspect it's difficult to build houses that are good in all weathers. I think the most adaptable I've seen was in Malta; they have relatively cold winters and sometimes very hot summers. Many apartments are narrow/deep and the areas exposed to the outside have big windows/doors at the front and back (leading to balconies) with one side usually facing the sea breeze. Because they're narrow, they don't have much surface area exposed to the outside which provides great insulation during the winter - For the summer, you keep cool by opening the windows on both sides so the wind flows through the whole apartment. It's also fine in terms of natural light; for modern apartments, the entire external wall may be glass so at least the living room gets plenty of sunlight. Bedrooms are a bit darker but that's usually a good thing; especially since many people like to sleep in on weekends.

In other parts of Europe (e.g. Berlin) they more typically have some apartments facing the outside and others facing an internal courtyard. They don't let the wind flow through and each person has a different experience.

> We've cut down so many trees in the cities and poured so much concrete that some places are radiating heat for hours after sundown, making the night a couple of degrees hotter than it should really be.

This one drives me absolutely bonkers because it's so clearly a CULTURAL CHOICE. Some places (Netherlands, Germany), make an effort to plant trees on streets, and frequent small parks and lawns.

But France doesn't - Paris being the worst. I don't know how Parisians own dogs. I find I have to walk for blocks to find a strip of grass for my pooch to go. Seems like they choose to just eradicate nature everywhere instead.

Japan is like this too inside the cities!

Note: I understand that both have massive beautiful green PARKS. But I'm referring to small patches of nature or grass between those, on neighborhoods, trees on side streets, etc.

> For example, we enlarged windows and doors, to the point were, standing behind one that's been cooking in the sun for a couple of hours, you feel the radiant heat a meter away from it.

Or perhaps get windows with low-emissivity ("low-e") coatings that block certain wavelengths of light:

* https://energyeducation.ca/encyclopedia/E-coating

* https://www.energy.gov/energysaver/window-types-and-technolo...

* https://www.nachi.org/low-e-windows.htm

I’ve lived in Europe (Balkans) and have family there as well. Some of them still don’t have AC but their houses are still pretty cool in the summers because homes there are mostly made with thick clay brick blocks AND they have “roletne” (we have no equivalent in the US, but they are built-in rolling shutters that can completely darken a room), and as long as those are kept closed during the day, the temperature stays tolerable. However, in recent years some have broken down and installed those high-efficiency in-wall units because the temperatures have been higher (at least that is the perception). I literally don’t know anyone over there with central AC and most are surprised to hear that many homes have them in the US.

> we have no equivalent in the US, but they are built-in rolling shutters that can completely darken a room

I'm always amazed the US doesn't have these. It's not exactly "peak" technology (I've had these my whole life) and so freaking useful. Having no AC, they're like the only reason I can keep my apartment cool during the summer. I know it because I didn't have them 2 summers ago and I almost ended up buying an AC. This summer I didn't even use my fan because I could keep my house cool.

Exactly. Deforestation in the Amazon is dwarfed by the end of old forests in Europe. There's almost no fauna and flora in Europe: all destroyed in the name of industrialization and civilization. Recent small-scale reforestation is touted as healing, but one might as well lay a bandaid on an amputated arm.

This might fit the UK or Netherlands, but not overall Europe.

This article provides a fairly in depth coverage: https://www.nature.com/articles/s41598-017-18646-7

Tldr forest coverage peaked 8k years ago, stayed more or less there till Romans, went down some couple dozen percent, paused after the Romans, then was decimated (heh) in the medieval era and modern times before now starting to recover.

I'm not disputing that forest coverage dropped significantly; "There's almost no fauna and flora in Europe" is very untrue though.

Forest resources in the EU expanded significantly over the past 70 years. From 1950 to 2020, there has been an increase in forest area (+37%)

Source: https://efi.int/forestquestions/q15#:~:text=Forest%20resourc....

But is it with monoculture?

Seen some HN comments about that recently.

Maybe, but…presentism? Europe could do what the US has done and declared so much land federally protected that growth is stifled and property rises to a level that prevents the young from buying it. Although that’s a different topic…

The land that is federally protected is generally not exactly sites so as to make for prime housing. Most of it, by area, is in places like northern Alaska.

That’s a problem but it has nothing to do with protected park land. Much of it was driven by racism: white people started leaving cities following civil rights era losses and sprawling out into adjacent suburbs, which were often forced to be low-density to exclude poorer people. That locks in a hefty climate footprint with all of that driving and larger low-efficiency houses.

The loss of forest resources in Europe over the last 10000 years, and in particular the last 5000 years (largely due to human activity) dwarfs any recent gains (1).

(1) https://www.nature.com/articles/s41598-017-18646-7

I came across this post yesterday that describes the issue in the context of Australia well. https://aus.social/@morachbeag/110959467825393289

Europe was deforested long before industrialization.