Somewhat tangential, but one thing that I've done that helps tremendously keep my cooling bills at bay is to move my toaster oven and induction burner to the patio on super hot days. Cooking...
Somewhat tangential, but one thing that I've done that helps tremendously keep my cooling bills at bay is to move my toaster oven and induction burner to the patio on super hot days. Cooking outside, especially boiling water or baking something, really helps keep my AC from having to work overdrive. Boiling water in particular puts a lot of excess humidity back in the air making it even harder for the AC to keep up.
Edit: And one thing an HVAC guy told me, which I didn't fully believe, but didn't fully disbelieve either...is that it's often better to just pick the temp you want for your AC and leave it there. It helps keep the rest of your stuff at that set temperature, which then lets your furniture and internal walls serve as some of that "thermal battery" to cope better with temperature fluctuations. Messing with the thermostat more than a degree or two doesn't really help things. Especially since humitity control is one of the most important aspects of thermal comfort.
I'd love to see some math about how much it might be worth having your AC cool your house excessively in the hour or so before sunrise and then keep it off for hours, when it would theoretically be less work for your AC to cool the house than in the full sun.
We’ve had some summers when I was working at home that I put up space blankets over the major windows (funny I had a lot of them because I needed props for a talk about...
We’ve had some summers when I was working at home that I put up space blankets over the major windows (funny I had a lot of them because I needed props for a talk about https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4550401/) and would throw open several windows and run fans to bring in as much cool air as I could at night and would close them up right before sunrise.
Another trick I discovered was to set my LED lights to green on the theory that green light has the most illuminating value per watt, I would certainly feel less heat from the lights this way.
I've done the poor version of the space blanket trick, which is foiling windows and/or using external shutters. Foiling windows is also great for making a good nap space for babies, incidentally....
I've done the poor version of the space blanket trick, which is foiling windows and/or using external shutters. Foiling windows is also great for making a good nap space for babies, incidentally.
So much so I'm looking to replace my worthless hunks of decorative plastic on my siding with proper shutters.
Fake shutters confuse me so much. The ones that were on my house would have covered about a quarter of the windows they were attached to if they had been capable of closing.
Fake shutters confuse me so much. The ones that were on my house would have covered about a quarter of the windows they were attached to if they had been capable of closing.
Do you put it up and take it down each day? Or leave it up? If you leave it up, do you not find it a bit grim living in semi-darkness all the time? I've toyed with the idea of trying to use...
Do you put it up and take it down each day? Or leave it up? If you leave it up, do you not find it a bit grim living in semi-darkness all the time? I've toyed with the idea of trying to use cardboard (an insulator, so maybe even multiple layers?) with foil attached to it somehow, to make boards fitted to my windows that I could sort of prop up and take down at will. Of course, you need to sort out a way to get it as close to the glass as possible and some way of looking after the foil, which will tear and nick very easily. I'd be interested to know what you do!
Duct tape is a great idea, if I make "plates" of cardboard-backed foil with duct taped borders, that should be robust enough if I'm careful. I see your point about not being home so much, if it...
Duct tape is a great idea, if I make "plates" of cardboard-backed foil with duct taped borders, that should be robust enough if I'm careful. I see your point about not being home so much, if it wasn't for not wanting to leave my wife to live in troll cave-like darkness, I would just foil everything up and have done with it. Thanks for your thoughts, they were very helpful.
To be pedantic, green doesn't have more "illuminating value", it's just that of the three primary colors of light it's the one you can see with the most detail. Your lights are cooler running...
To be pedantic, green doesn't have more "illuminating value", it's just that of the three primary colors of light it's the one you can see with the most detail.
Your lights are cooler running green not because green is any more efficient than any other color, but because you're using RGB LEDs, which are just Red, Green, and Blue LED's combined in a single package. It's cooler because you're only using 1/3rd the power it were if it were white, which combines all three. You'll likely get better efficiency with white light by using LEDs that output white light directly.
Nope, see https://www.gigahertz-optik.com/en-us/service-and-support/knowledge-base/basics-light-measurement/light-color/spectr-sens-eye/ where it is the “photopic” curve that matters. It’s...
where it is the “photopic” curve that matters. It’s probably more complicated because the efficiency of the actual LED or other light source is various but what matters to me is that I can feel “heat” on my bare skin when I am underneath a light which is mainly the energy of the desired light. I’m sure there is some heat produced in the LED, power supply, etc. Some of that will be radiated but I think a lot of it is lost by conduction, convection, etc. All of the waste heat warms the house but it is the radiant energy (mostly the light in the case of an LED) that makes me feel warmer than the thermostat says.
Note in the cases where I am running my lights green there is still plenty of light coming through my windows so it is not like everything looks green, this is light that is supplementing natural light so if it is imbalanced in color it is not so bad.
Huh, TIL. But how bright are your lights to the point where the light would feel warm? I also find it weird to have them on during the day unless it’s in a secluded area like a bathroom or a...
Huh, TIL.
But how bright are your lights to the point where the light would feel warm? I also find it weird to have them on during the day unless it’s in a secluded area like a bathroom or a closet, and even then it’s only momentary.
It’s pretty normal for offices to be lit during the day even if they have windows. I am working in an office right now and had the lights on until I started posting this. When I turned the lights...
It’s pretty normal for offices to be lit during the day even if they have windows. I am working in an office right now and had the lights on until I started posting this. When I turned the lights off I felt it wasn’t bright enough.
My office has two switches to control two banks of fluorescent lights to get three possible brightness levels. If I stick out my bare arm (wearing a short sleeved shirt) I can definitely feel the heat from the lights on my skin.
Depends on a few things: Temperature difference between morning and afternoon: the temperature lift on the air conditioner is lower when it's cool outside which makes it more efficient than when...
I'd love to see some math about how much it might be worth having your AC cool your house excessively in the hour or so before sunrise and then keep it off for hours, when it would theoretically be less work for your AC to cool the house than in the full sun.
Depends on a few things:
Temperature difference between morning and afternoon: the temperature lift on the air conditioner is lower when it's cool outside which makes it more efficient than when it's warm. How much more efficient depends on the temperature difference. As a rule of thumb, it's about 1-2% more efficient per degree F of lift, so about 10-20% more efficient when it's 70 degrees out vs. 80 degrees out.
Humidity: if you try to cool your house below the dewpoint you will spend some energy dehumidifying the air vs. just making it cooler. So your energy spend to get that next deg F down might be more than if it wasn't so humid out.
How insulated your house is: heat is going to infiltrate your house. The bigger the temperature difference is between the inside and outside of your house, the faster heat transfers, in a linear fashion. Insulation will slow the heat transfer, but it's still a linear relationship. So pre-cooling your house to a lower temperature will eventually result in more heat transfer that has to be removed by the AC, compared to keeping it at a higher constant temperature. How insulated your house is affects how long you can ride out the temperature rise. This is what your HVAC guy was referring to when saying to set it to a temperature and leave it there.
Does your utility rate vary: if you are on a variable rate based on time of day, you can capture some cost savings by running your AC when your electricity is cheap vs. when it's expensive. However if you are on a fixed rate then it doesn't make a difference.
Interestingly, if there are solar panels near or on the house, it may be worthwhile to turn the AC on at mid-day, while less efficient, it could help with grid congestion as power flows stay local.
Interestingly, if there are solar panels near or on the house, it may be worthwhile to turn the AC on at mid-day, while less efficient, it could help with grid congestion as power flows stay local.
To the internal battery theory. I read an article about “supercooling” a house at night to cool all the internal structure to something in the 60s when there is a lower outside air temperature...
To the internal battery theory. I read an article about “supercooling” a house at night to cool all the internal structure to something in the 60s when there is a lower outside air temperature making the work easier on the ac. Also seemed that there was a benefit if you off peak energy pricing. I don’t know how the math works out but it’s used that same thermal battery concept in the explanation. I’ll try to find the article and update later.
I mean, that's how it is here...but the days are upwards of 90+ so that 20 swing isn't anything to sneeze at. The beauty of heat pumps. In cooling mode, the efficiency is in no small part a...
I mean, that's how it is here...but the days are upwards of 90+ so that 20 swing isn't anything to sneeze at.
The beauty of heat pumps. In cooling mode, the efficiency is in no small part a byproduct of how quickly the outdoor unit can cool itself. It'll do a better job of that when it's 70 out instead of 90.
The math would change dramatically depending on how well insulated your house is, as well as the kind of weather you are experiencing. This summer has been kind of unusual for the area I live in...
The math would change dramatically depending on how well insulated your house is, as well as the kind of weather you are experiencing.
This summer has been kind of unusual for the area I live in because so far we have somehow been able to avoid using air conditioning at all. How this happened during a historic heat wave, I have no idea. We just close up the curtains, windows, and doors during the day and open them up late afternoon. Fans do the rest of the work.
Is that when it's really hot outside and you're trying to cool the house, or when it's really cold and you're trying to warm it? I've found that this effect goes both ways - i.e. in summer an...
Is that when it's really hot outside and you're trying to cool the house, or when it's really cold and you're trying to warm it?
I've found that this effect goes both ways - i.e. in summer an indoor temperature tends to feel warmer than the same temperature would feel outdoors and vice versa in winter. This is particularly noticeable in the car, even after the interior has had some time to cool down or warm up.
When it's really cold outside I have trouble heating the house. But it's always cooler when it's hot out. The reason: there's a great stonking hole under the house and no insulation under the...
When it's really cold outside I have trouble heating the house. But it's always cooler when it's hot out. The reason: there's a great stonking hole under the house and no insulation under the floor. Basically natural air conditioning you can't switch off.
It's a good article to make the wide public aware, but it isn't anything new in the field of building physics. The science of comfort, based on things like PMV or Fanger has long included the...
It's a good article to make the wide public aware, but it isn't anything new in the field of building physics. The science of comfort, based on things like PMV or Fanger has long included the radiant heat (in both summer and winter), but also air flow (which increases with most airco units) and humidity.
A rough estimate is that the temperature you feel equals the average of the sensible temperature (the temperature on the thermostat) and the temperature equivalent of the radiant heat (i.e. the weighted average temperature of all surfaces).
This is particularly interesting in winter months, where in poorly insulated houses, the wall temperatures are lower than in well insulated houses. To reach the same comfort level (for the same person), the thermostat in the well insulated house can therefore be set lower. Insulating not only reduced the heat loss, it also lowers the indoor temperature, gaining additional heat loss reduction.
It goes even further with large low temperature heat distribution systems such as floor heating. They increase the average radiant heat, reducing the thermostat set point even further.
Somewhat tangential, but one thing that I've done that helps tremendously keep my cooling bills at bay is to move my toaster oven and induction burner to the patio on super hot days. Cooking outside, especially boiling water or baking something, really helps keep my AC from having to work overdrive. Boiling water in particular puts a lot of excess humidity back in the air making it even harder for the AC to keep up.
Edit: And one thing an HVAC guy told me, which I didn't fully believe, but didn't fully disbelieve either...is that it's often better to just pick the temp you want for your AC and leave it there. It helps keep the rest of your stuff at that set temperature, which then lets your furniture and internal walls serve as some of that "thermal battery" to cope better with temperature fluctuations. Messing with the thermostat more than a degree or two doesn't really help things. Especially since humitity control is one of the most important aspects of thermal comfort.
I'd love to see some math about how much it might be worth having your AC cool your house excessively in the hour or so before sunrise and then keep it off for hours, when it would theoretically be less work for your AC to cool the house than in the full sun.
We’ve had some summers when I was working at home that I put up space blankets over the major windows (funny I had a lot of them because I needed props for a talk about https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4550401/) and would throw open several windows and run fans to bring in as much cool air as I could at night and would close them up right before sunrise.
Another trick I discovered was to set my LED lights to green on the theory that green light has the most illuminating value per watt, I would certainly feel less heat from the lights this way.
I've done the poor version of the space blanket trick, which is foiling windows and/or using external shutters. Foiling windows is also great for making a good nap space for babies, incidentally.
So much so I'm looking to replace my worthless hunks of decorative plastic on my siding with proper shutters.
Fake shutters confuse me so much. The ones that were on my house would have covered about a quarter of the windows they were attached to if they had been capable of closing.
They make me irrationally angry at their non-functionality :|
Do you put it up and take it down each day? Or leave it up? If you leave it up, do you not find it a bit grim living in semi-darkness all the time? I've toyed with the idea of trying to use cardboard (an insulator, so maybe even multiple layers?) with foil attached to it somehow, to make boards fitted to my windows that I could sort of prop up and take down at will. Of course, you need to sort out a way to get it as close to the glass as possible and some way of looking after the foil, which will tear and nick very easily. I'd be interested to know what you do!
Duct tape is a great idea, if I make "plates" of cardboard-backed foil with duct taped borders, that should be robust enough if I'm careful. I see your point about not being home so much, if it wasn't for not wanting to leave my wife to live in troll cave-like darkness, I would just foil everything up and have done with it. Thanks for your thoughts, they were very helpful.
The space blankets are probably cheaper than the foil but they are not as reflective.
Probably, but I already had foil in the house. Welcome to poverty math. :)
To be pedantic, green doesn't have more "illuminating value", it's just that of the three primary colors of light it's the one you can see with the most detail.
Your lights are cooler running green not because green is any more efficient than any other color, but because you're using RGB LEDs, which are just Red, Green, and Blue LED's combined in a single package. It's cooler because you're only using 1/3rd the power it were if it were white, which combines all three. You'll likely get better efficiency with white light by using LEDs that output white light directly.
Nope, see
https://www.gigahertz-optik.com/en-us/service-and-support/knowledge-base/basics-light-measurement/light-color/spectr-sens-eye/
where it is the “photopic” curve that matters. It’s probably more complicated because the efficiency of the actual LED or other light source is various but what matters to me is that I can feel “heat” on my bare skin when I am underneath a light which is mainly the energy of the desired light. I’m sure there is some heat produced in the LED, power supply, etc. Some of that will be radiated but I think a lot of it is lost by conduction, convection, etc. All of the waste heat warms the house but it is the radiant energy (mostly the light in the case of an LED) that makes me feel warmer than the thermostat says.
Note in the cases where I am running my lights green there is still plenty of light coming through my windows so it is not like everything looks green, this is light that is supplementing natural light so if it is imbalanced in color it is not so bad.
Huh, TIL.
But how bright are your lights to the point where the light would feel warm? I also find it weird to have them on during the day unless it’s in a secluded area like a bathroom or a closet, and even then it’s only momentary.
It’s pretty normal for offices to be lit during the day even if they have windows. I am working in an office right now and had the lights on until I started posting this. When I turned the lights off I felt it wasn’t bright enough.
My office has two switches to control two banks of fluorescent lights to get three possible brightness levels. If I stick out my bare arm (wearing a short sleeved shirt) I can definitely feel the heat from the lights on my skin.
Depends on a few things:
Temperature difference between morning and afternoon: the temperature lift on the air conditioner is lower when it's cool outside which makes it more efficient than when it's warm. How much more efficient depends on the temperature difference. As a rule of thumb, it's about 1-2% more efficient per degree F of lift, so about 10-20% more efficient when it's 70 degrees out vs. 80 degrees out.
Humidity: if you try to cool your house below the dewpoint you will spend some energy dehumidifying the air vs. just making it cooler. So your energy spend to get that next deg F down might be more than if it wasn't so humid out.
How insulated your house is: heat is going to infiltrate your house. The bigger the temperature difference is between the inside and outside of your house, the faster heat transfers, in a linear fashion. Insulation will slow the heat transfer, but it's still a linear relationship. So pre-cooling your house to a lower temperature will eventually result in more heat transfer that has to be removed by the AC, compared to keeping it at a higher constant temperature. How insulated your house is affects how long you can ride out the temperature rise. This is what your HVAC guy was referring to when saying to set it to a temperature and leave it there.
Does your utility rate vary: if you are on a variable rate based on time of day, you can capture some cost savings by running your AC when your electricity is cheap vs. when it's expensive. However if you are on a fixed rate then it doesn't make a difference.
Interestingly, if there are solar panels near or on the house, it may be worthwhile to turn the AC on at mid-day, while less efficient, it could help with grid congestion as power flows stay local.
To the internal battery theory. I read an article about “supercooling” a house at night to cool all the internal structure to something in the 60s when there is a lower outside air temperature making the work easier on the ac. Also seemed that there was a benefit if you off peak energy pricing. I don’t know how the math works out but it’s used that same thermal battery concept in the explanation. I’ll try to find the article and update later.
Alec from Technology Connections is doing exactly that and he has shared his experience in one of his video
Cries in not getting below 70° (21° C) overnight.
I mean, that's how it is here...but the days are upwards of 90+ so that 20 swing isn't anything to sneeze at.
The beauty of heat pumps. In cooling mode, the efficiency is in no small part a byproduct of how quickly the outdoor unit can cool itself. It'll do a better job of that when it's 70 out instead of 90.
The math would change dramatically depending on how well insulated your house is, as well as the kind of weather you are experiencing.
This summer has been kind of unusual for the area I live in because so far we have somehow been able to avoid using air conditioning at all. How this happened during a historic heat wave, I have no idea. We just close up the curtains, windows, and doors during the day and open them up late afternoon. Fans do the rest of the work.
Oh I know. But if someone does the math for themselves it's easier for me to grok, but also makes for some great reading.
Warmer? Mine has always felt colder.
Is that when it's really hot outside and you're trying to cool the house, or when it's really cold and you're trying to warm it?
I've found that this effect goes both ways - i.e. in summer an indoor temperature tends to feel warmer than the same temperature would feel outdoors and vice versa in winter. This is particularly noticeable in the car, even after the interior has had some time to cool down or warm up.
When it's really cold outside I have trouble heating the house. But it's always cooler when it's hot out. The reason: there's a great stonking hole under the house and no insulation under the floor. Basically natural air conditioning you can't switch off.
It's a good article to make the wide public aware, but it isn't anything new in the field of building physics. The science of comfort, based on things like PMV or Fanger has long included the radiant heat (in both summer and winter), but also air flow (which increases with most airco units) and humidity.
A rough estimate is that the temperature you feel equals the average of the sensible temperature (the temperature on the thermostat) and the temperature equivalent of the radiant heat (i.e. the weighted average temperature of all surfaces).
This is particularly interesting in winter months, where in poorly insulated houses, the wall temperatures are lower than in well insulated houses. To reach the same comfort level (for the same person), the thermostat in the well insulated house can therefore be set lower. Insulating not only reduced the heat loss, it also lowers the indoor temperature, gaining additional heat loss reduction.
It goes even further with large low temperature heat distribution systems such as floor heating. They increase the average radiant heat, reducing the thermostat set point even further.