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House cooling doesn't really need A/C most of the time. Most countries in Europe and North America (exceptions are mostly Mediterranean countries) aren't even u

House cooling doesn't really need A/C most of the time. Most countries in Europe and North America (exceptions are mostly Mediterranean countries) aren't even using blinds that prevent sunrays from reaching the glass of the windows. People are living in greenhouses, not houses, and the ridiculous part is that they are not even in there most of the time during the day, so the light is unused and the heat accumulates so much that you get home to an unbearable 30C/80F temperature. If the heat was kept out of the house properly during the day, you could just keep the house cool enough by opening the windows during the night, without any A/C at all.

KingMachiavelli 5y ago
Most people do use blinds to keep the sun out but they are on the inside of the glass. Blinds on the inside of the glass are sufficient since we are only talking about blocking/reflecting infrared heat. In the US at least, modern windows in the last 20 years can have an inferred reflective coating meaning you don't need blinds at all. The big issue is humidity. Attic fans work great in low humidity places but by their nature they pull in exterior air. If it's 70F but very humid, then you will not have a great time opening windows even at night. The scenarios in which you don't need AC also work really well with AC; the efficiency (COPR) of a heat pump depends on the temperature difference that you pump heat across. If the exterior temperature is lower at night then the heat pump is going to have great efficiency anyway. Also AC has to condense water (cooler air holds less water), letting in (humid) air at night only to run AC during the day is not as efficient as looks. I big part of people saving money on cooling when using an attic fan or opening windows is they are probably also just letting the interior reach a higher temperature. To keep this somewhat on topic, in is more efficient for heat pumps to cool a room than to cool individual people/things inside that room typically because when you are cooling the room you are moving the heat to the outside of an insulated area.
- bonzini 5y ago
  > Most people do use blinds to keep the sun out but they are on the inside of the glass. That's exactly my point, in Southern Europe blinds are on the outside of the glass, not inside. Reflective coating and insulating double glass is good but not the same as they're not 100% efficient (with outside blinds, they absorb the heat and insulating glass is very good at keeping conduction at bay). I can come home in the evening and barely notice the difference in temperature from when I left (25C-26C in the morning, 26C-27.5C in the evening, so about 1.5C difference); that's even with 33-36C highs outside. By 5PM it's possible to open blinds because I don't get direct sunlight anymore (my house faces South and East and has other buildings towards west), and I open the windows from 10PM till dawn at 5-6AM.
  - KingMachiavelli 5y ago
    Blinds on the outside... How does that work? How do the blinds not get destroyed by the wind?
    - stolsvik 5y ago
      They are rigid, typically of some metal.

KingMachiavelli 5y ago

Most people do use blinds to keep the sun out but they are on the inside of the glass. Blinds on the inside of the glass are sufficient since we are only talking about blocking/reflecting infrared heat. In the US at least, modern windows in the last 20 years can have an inferred reflective coating meaning you don't need blinds at all. The big issue is humidity. Attic fans work great in low humidity places but by their nature they pull in exterior air. If it's 70F but very humid, then you will not have a great time opening windows even at night. The scenarios in which you don't need AC also work really well with AC; the efficiency (COPR) of a heat pump depends on the temperature difference that you pump heat across. If the exterior temperature is lower at night then the heat pump is going to have great efficiency anyway. Also AC has to condense water (cooler air holds less water), letting in (humid) air at night only to run AC during the day is not as efficient as looks. I big part of people saving money on cooling when using an attic fan or opening windows is they are probably also just letting the interior reach a higher temperature. To keep this somewhat on topic, in is more efficient for heat pumps to cool a room than to cool individual people/things inside that room typically because when you are cooling the room you are moving the heat to the outside of an insulated area.

bonzini 5y ago
> Most people do use blinds to keep the sun out but they are on the inside of the glass. That's exactly my point, in Southern Europe blinds are on the outside of the glass, not inside. Reflective coating and insulating double glass is good but not the same as they're not 100% efficient (with outside blinds, they absorb the heat and insulating glass is very good at keeping conduction at bay). I can come home in the evening and barely notice the difference in temperature from when I left (25C-26C in the morning, 26C-27.5C in the evening, so about 1.5C difference); that's even with 33-36C highs outside. By 5PM it's possible to open blinds because I don't get direct sunlight anymore (my house faces South and East and has other buildings towards west), and I open the windows from 10PM till dawn at 5-6AM.
- KingMachiavelli 5y ago
  Blinds on the outside... How does that work? How do the blinds not get destroyed by the wind?
  - stolsvik 5y ago
    They are rigid, typically of some metal.