Author Topic: What did you do to keep your house cool?  (Read 14147 times)

Villanelle

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Re: What did you do to keep your house cool?
« Reply #100 on: July 09, 2019, 01:54:52 PM »
I'm new to a humid, rainy climate.  How on earth does one do it?  I can't leave the windows open at night--not even cracked, because storms pop up suddenly and everything gets drenched.  (Ask me how I know.)  But I'm losing all that cooler night air with my windows shut tight. Am I missing something?  (And yes, we do have frequent, fairly sudden rain storms.  I can open a few windows when we are home and awake because I can shut them quickly and mop up any water on the wood floors that may sneak in before it has time to sit. But once we go to bed, it seems I have to close everything up.

Does your house come with sufficient eaves? My experience is that the rainier parts of the U.S. have low correlation with the windier parts of the U.S., so eaves are generally sufficient to allow for open windows at night without the threat of water intrusion. (Partial source: Growing up in Miami without AC, in which open windows were a necessity.)

No.  We have basically no eaves.  Water definitely comes in when it rains.  We learned that very quickly our second night in the home. 

As it turns out, water also comes in to the basement--6"!!!!--when it rains a lot. 

J Boogie

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Re: What did you do to keep your house cool?
« Reply #101 on: July 10, 2019, 07:58:09 AM »
I'm new to a humid, rainy climate.  How on earth does one do it?  I can't leave the windows open at night--not even cracked, because storms pop up suddenly and everything gets drenched.  (Ask me how I know.)  But I'm losing all that cooler night air with my windows shut tight. Am I missing something?  (And yes, we do have frequent, fairly sudden rain storms.  I can open a few windows when we are home and awake because I can shut them quickly and mop up any water on the wood floors that may sneak in before it has time to sit. But once we go to bed, it seems I have to close everything up.

Does your house come with sufficient eaves? My experience is that the rainier parts of the U.S. have low correlation with the windier parts of the U.S., so eaves are generally sufficient to allow for open windows at night without the threat of water intrusion. (Partial source: Growing up in Miami without AC, in which open windows were a necessity.)

No.  We have basically no eaves.  Water definitely comes in when it rains.  We learned that very quickly our second night in the home. 

As it turns out, water also comes in to the basement--6"!!!!--when it rains a lot.

You can put awnings over the windows you benefit most from keeping open.

If they are double hung windows, you can open them from the top instead and they will be that much less likely to allow water in.

Bonus is that they'll keep heat out too esp. on the west and south side of the house (assuming you're in the northern hemisphere)

GuitarStv

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Re: What did you do to keep your house cool?
« Reply #102 on: July 10, 2019, 08:30:13 AM »
As it turns out, water also comes in to the basement--6"!!!!--when it rains a lot.

What you're referring to as a basement sounds like it may actually be an old well.  :P

Villanelle

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Re: What did you do to keep your house cool?
« Reply #103 on: July 10, 2019, 08:58:35 AM »
As it turns out, water also comes in to the basement--6"!!!!--when it rains a lot.

What you're referring to as a basement sounds like it may actually be an old well.  :P

Or an indoor swimming pool. 

It hasn't been a fun couple of days around here!

GuitarStv

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Re: What did you do to keep your house cool?
« Reply #104 on: July 10, 2019, 08:59:49 AM »
As it turns out, water also comes in to the basement--6"!!!!--when it rains a lot.

What you're referring to as a basement sounds like it may actually be an old well.  :P

Or an indoor swimming pool. 

It hasn't been a fun couple of days around here!

Throw in some pool noodles.  Some people pay a lot of money for what you've got for free!

dougules

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Re: What did you do to keep your house cool?
« Reply #105 on: July 10, 2019, 11:26:28 AM »
Basements are fairly uncommon in this area for that very reason. 

newloginuser

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Re: What did you do to keep your house cool?
« Reply #106 on: August 06, 2019, 01:42:29 PM »
Didn't want to make a new topic for this but hopefully don't mind me piggybacking:

I live in New England where the summer months are generally in the 80's and the nights tend to be in the 60's or sometimes lower. I tend to open the windows when it's in the 70's with about 40% humidity, but once the temperature drops to the 60's or lower, the humidity seems to rise to the 80-90%.

I know high humidity isn't good for a home, but also read 80% humidity in 90 degree weather isn't the same as 80% humidity in 60 degree weather.

Can anyone help with this? Should I just leave the windows open briefly or should I be ok leaving them open in the night if the temperature is in the 60's but humidity is 80-90%?

Boofinator

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Re: What did you do to keep your house cool?
« Reply #107 on: August 06, 2019, 02:36:11 PM »
Didn't want to make a new topic for this but hopefully don't mind me piggybacking:

I live in New England where the summer months are generally in the 80's and the nights tend to be in the 60's or sometimes lower. I tend to open the windows when it's in the 70's with about 40% humidity, but once the temperature drops to the 60's or lower, the humidity seems to rise to the 80-90%.

I know high humidity isn't good for a home, but also read 80% humidity in 90 degree weather isn't the same as 80% humidity in 60 degree weather.

Can anyone help with this? Should I just leave the windows open briefly or should I be ok leaving them open in the night if the temperature is in the 60's but humidity is 80-90%?

Relative humidity is truly a poor metric that somehow got elevated into common parlance. The problem with relative humidity is that it is the percentage of water vapor in the air relative to the amount of water that can be held in the air at that temperature, which wouldn't necessarily be a problem except that the amount of water vapor air can hold is heavily dependent on temperature. As can be seen from the chart on this page (https://www.engineeringtoolbox.com/water-vapor-air-d_854.html), for every 20F increase in temperature, the amount of water the air can hold just about doubles. Put another way, if the temperature drops 20F and the amount of vapor in the air stays constant, your relative humidity will double. Needless to say, relative humidity levels fluctuate significantly on a diurnal basis, and it makes for a ton of unnecessary confusion.

A much better metric to use, that is also widely reported, is dew point. This is the temperature at which water will begin condensing out of the air as dew. This number is independent of temperature and stays constant with the amount of water vapor that is present in the air.

All of that being said, I personally wouldn't worry about the humidity if your outside temperature is in the 60's and you are comfortable with the ambient temperature throughout the day (and if you aren't comfortable, your A/C will take out the water vapor if you decide to run it).

Villanelle

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Re: What did you do to keep your house cool?
« Reply #108 on: August 06, 2019, 03:18:14 PM »
Our master bedroom has an odd little area. It's one small (3-4 inches) step up and is an open, mostly useless area roughly 5x5 with a closet (not walk-in) on either side.  It also has two skylights over it and three skinny windows along the back.  (Old house, many changes and additions, so things are sometimes odd.)  I just installed heavy velvet blackout curtains last night to separate that area from the rest of the room.  They weren't especially cheap.  But this afternoon (day 1 of the curtains) I could feel a significant difference.  With the a/c off upstairs during the day, it's usually very hot in our bedroom by afternoon.  With those curtains closed, the hot air from the skylights and windows stayed inside the curtained off area, so the bedroom didn't heat up nearly as much.  I spent a fair amount on the curtains but think this is going to pay for itself rather quickly.  We run a portable a/c in the bedroom at night (I sleep hot, but don't want to cool the entire level all night since we are the only two people living here).  I'm quite certain it is going to run far less, with a smaller space to cool and a lower starting temp when we turn it on. 

hops

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Re: What did you do to keep your house cool?
« Reply #109 on: August 07, 2019, 07:08:25 AM »
Our energy usage decreased by 6% this summer, despite high temperatures, and the only changes we made were pinning thermal blackout liners to the backs of all our curtains and replacing ancient, flimsy basement windows with glass block.

GuitarStv

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Re: What did you do to keep your house cool?
« Reply #110 on: August 07, 2019, 07:52:13 AM »
Didn't want to make a new topic for this but hopefully don't mind me piggybacking:

I live in New England where the summer months are generally in the 80's and the nights tend to be in the 60's or sometimes lower. I tend to open the windows when it's in the 70's with about 40% humidity, but once the temperature drops to the 60's or lower, the humidity seems to rise to the 80-90%.

I know high humidity isn't good for a home, but also read 80% humidity in 90 degree weather isn't the same as 80% humidity in 60 degree weather.

Can anyone help with this? Should I just leave the windows open briefly or should I be ok leaving them open in the night if the temperature is in the 60's but humidity is 80-90%?

Relative humidity is truly a poor metric that somehow got elevated into common parlance. The problem with relative humidity is that it is the percentage of water vapor in the air relative to the amount of water that can be held in the air at that temperature, which wouldn't necessarily be a problem except that the amount of water vapor air can hold is heavily dependent on temperature. As can be seen from the chart on this page (https://www.engineeringtoolbox.com/water-vapor-air-d_854.html), for every 20F increase in temperature, the amount of water the air can hold just about doubles. Put another way, if the temperature drops 20F and the amount of vapor in the air stays constant, your relative humidity will double. Needless to say, relative humidity levels fluctuate significantly on a diurnal basis, and it makes for a ton of unnecessary confusion.

A much better metric to use, that is also widely reported, is dew point. This is the temperature at which water will begin condensing out of the air as dew. This number is independent of temperature and stays constant with the amount of water vapor that is present in the air.

All of that being said, I personally wouldn't worry about the humidity if your outside temperature is in the 60's and you are comfortable with the ambient temperature throughout the day (and if you aren't comfortable, your A/C will take out the water vapor if you decide to run it).

If dew point is independent of temperature then how come in the fall when outdoor temperatures are between 8 to 15 degrees and the windows/doors to the house are always shut there's never condensation on the windows?  In the winter when temperatures are from -5 to -20 threre's always condensation on the windows.  If anything, the humidity is lower in our house in the winter.

Boofinator

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Re: What did you do to keep your house cool?
« Reply #111 on: August 07, 2019, 08:24:55 AM »
Didn't want to make a new topic for this but hopefully don't mind me piggybacking:

I live in New England where the summer months are generally in the 80's and the nights tend to be in the 60's or sometimes lower. I tend to open the windows when it's in the 70's with about 40% humidity, but once the temperature drops to the 60's or lower, the humidity seems to rise to the 80-90%.

I know high humidity isn't good for a home, but also read 80% humidity in 90 degree weather isn't the same as 80% humidity in 60 degree weather.

Can anyone help with this? Should I just leave the windows open briefly or should I be ok leaving them open in the night if the temperature is in the 60's but humidity is 80-90%?

Relative humidity is truly a poor metric that somehow got elevated into common parlance. The problem with relative humidity is that it is the percentage of water vapor in the air relative to the amount of water that can be held in the air at that temperature, which wouldn't necessarily be a problem except that the amount of water vapor air can hold is heavily dependent on temperature. As can be seen from the chart on this page (https://www.engineeringtoolbox.com/water-vapor-air-d_854.html), for every 20F increase in temperature, the amount of water the air can hold just about doubles. Put another way, if the temperature drops 20F and the amount of vapor in the air stays constant, your relative humidity will double. Needless to say, relative humidity levels fluctuate significantly on a diurnal basis, and it makes for a ton of unnecessary confusion.

A much better metric to use, that is also widely reported, is dew point. This is the temperature at which water will begin condensing out of the air as dew. This number is independent of temperature and stays constant with the amount of water vapor that is present in the air.

All of that being said, I personally wouldn't worry about the humidity if your outside temperature is in the 60's and you are comfortable with the ambient temperature throughout the day (and if you aren't comfortable, your A/C will take out the water vapor if you decide to run it).

If dew point is independent of temperature then how come in the fall when outdoor temperatures are between 8 to 15 degrees and the windows/doors to the house are always shut there's never condensation on the windows?  In the winter when temperatures are from -5 to -20 threre's always condensation on the windows.  If anything, the humidity is lower in our house in the winter.

Here's an example to help illustrate the idea: Let's assume you have enough water vapor inside your house so that the dew point is 0C (this would work out to 3.77 g of water per kilogram of air). Let's also assume negligible insulation from your windows (not an accurate assumption, but gets the point across). If the outside air temperature stays above 0C, the inside air in contact with your windows cannot condensate since it is above the dew point, and the dew point will remain constant. However, if the outside air drops below 0C, the inside air in contact with the windows will drop below the dew point and water vapor must condensate on the windows (and the dew point of that air in contact with the windows must drop as well since the air is losing water vapor). So to answer your question, the humidity is lower in the house in the winter directly as a result of the water vapor in the air forming condensate at cold interfaces (and due to air exchanges with the low humidity outside air).

(On a side note, air conditioning sucks water vapor out of the air by lowering the temperature of the air by the coils to a very low temperature prior to blowing it back through the house. So even if somebody sets the thermostat to a temperature above the dew point, the air that is being chilled will be at a much lower temperature and the resulting dew point (aka humidity) in the house will drop accordingly.)

GuitarStv

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Re: What did you do to keep your house cool?
« Reply #112 on: August 07, 2019, 08:35:22 AM »
Didn't want to make a new topic for this but hopefully don't mind me piggybacking:

I live in New England where the summer months are generally in the 80's and the nights tend to be in the 60's or sometimes lower. I tend to open the windows when it's in the 70's with about 40% humidity, but once the temperature drops to the 60's or lower, the humidity seems to rise to the 80-90%.

I know high humidity isn't good for a home, but also read 80% humidity in 90 degree weather isn't the same as 80% humidity in 60 degree weather.

Can anyone help with this? Should I just leave the windows open briefly or should I be ok leaving them open in the night if the temperature is in the 60's but humidity is 80-90%?

Relative humidity is truly a poor metric that somehow got elevated into common parlance. The problem with relative humidity is that it is the percentage of water vapor in the air relative to the amount of water that can be held in the air at that temperature, which wouldn't necessarily be a problem except that the amount of water vapor air can hold is heavily dependent on temperature. As can be seen from the chart on this page (https://www.engineeringtoolbox.com/water-vapor-air-d_854.html), for every 20F increase in temperature, the amount of water the air can hold just about doubles. Put another way, if the temperature drops 20F and the amount of vapor in the air stays constant, your relative humidity will double. Needless to say, relative humidity levels fluctuate significantly on a diurnal basis, and it makes for a ton of unnecessary confusion.

A much better metric to use, that is also widely reported, is dew point. This is the temperature at which water will begin condensing out of the air as dew. This number is independent of temperature and stays constant with the amount of water vapor that is present in the air.

All of that being said, I personally wouldn't worry about the humidity if your outside temperature is in the 60's and you are comfortable with the ambient temperature throughout the day (and if you aren't comfortable, your A/C will take out the water vapor if you decide to run it).

If dew point is independent of temperature then how come in the fall when outdoor temperatures are between 8 to 15 degrees and the windows/doors to the house are always shut there's never condensation on the windows?  In the winter when temperatures are from -5 to -20 threre's always condensation on the windows.  If anything, the humidity is lower in our house in the winter.

Here's an example to help illustrate the idea: Let's assume you have enough water vapor inside your house so that the dew point is 0C (this would work out to 3.77 g of water per kilogram of air). Let's also assume negligible insulation from your windows (not an accurate assumption, but gets the point across). If the outside air temperature stays above 0C, the inside air in contact with your windows cannot condensate since it is above the dew point, and the dew point will remain constant. However, if the outside air drops below 0C, the inside air in contact with the windows will drop below the dew point and water vapor must condensate on the windows (and the dew point of that air in contact with the windows must drop as well since the air is losing water vapor). So to answer your question, the humidity is lower in the house in the winter directly as a result of the water vapor in the air forming condensate at cold interfaces (and due to air exchanges with the low humidity outside air).

(On a side note, air conditioning sucks water vapor out of the air by lowering the temperature of the air by the coils to a very low temperature prior to blowing it back through the house. So even if somebody sets the thermostat to a temperature above the dew point, the air that is being chilled will be at a much lower temperature and the resulting dew point (aka humidity) in the house will drop accordingly.)

I still don't get it.  We keep the indoor temperature at 17 degrees in the winter . . . and get condensation on the windows.  if we increase the temperature indoors to 23 degrees (because guests are staying over or something) the condensation on the windows disappears.  The air exchange should be happening more quickly with the greater temperature difference.  Why does the condensation go away?

I feel like dew point must therefore be temperature dependent.

Boofinator

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Re: What did you do to keep your house cool?
« Reply #113 on: August 07, 2019, 08:55:12 AM »
I still don't get it.  We keep the indoor temperature at 17 degrees in the winter . . . and get condensation on the windows.  if we increase the temperature indoors to 23 degrees (because guests are staying over or something) the condensation on the windows disappears.  The air exchange should be happening more quickly with the greater temperature difference.  Why does the condensation go away?

I feel like dew point must therefore be temperature dependent.

I simplified my earlier analysis by using the assumption of "negligible insulation at the windows". In reality, all windows have some insulation, so that the air temperature at the interface of the window is some fraction of the way between the air temperature inside the house and the air temperature outside the house. Let's use 50%, and assume the outside temperature is 5C. So when your house is 17C, the temperature at the air-window interface is 11C, whereas if the indoor temperature is 23C, the temperature at the air-window interface will be 14C. A 3C delta is roughly equivalent to 25% more water vapor that could be held in the air, which must have been enough to not form condensate.

By definition, dew point is the air temperature at which water will condensate given the amount of water in the air. It is only dependent on the amount of water vapor in the air, and nothing else.

ETA: That last statement isn't true. Dew point is also a function of pressure.
« Last Edit: August 07, 2019, 09:00:37 AM by Boofinator »

newloginuser

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Re: What did you do to keep your house cool?
« Reply #114 on: August 07, 2019, 09:12:20 AM »
Thank you @Boofinator for that description. That may have been the most helpful bit of information I read so far on this issue although I also am still a bit confused.

Not to over simplify, but it sounds like as long as the dew point is similar from outside to inside and condensation won't form on the windows, then I should be ok to leave them open and not worry about too much moisture coming inside the home?

Boofinator

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Re: What did you do to keep your house cool?
« Reply #115 on: August 07, 2019, 10:16:57 AM »
Thank you @Boofinator for that description. That may have been the most helpful bit of information I read so far on this issue although I also am still a bit confused.

Not to over simplify, but it sounds like as long as the dew point is similar from outside to inside and condensation won't form on the windows, then I should be ok to leave them open and not worry about too much moisture coming inside the home?

Yes, you are correct: if the dew point is the same inside and out, then you need not worry at all about moisture coming in. Things get a little tricky during the summer months if the outside dew point is higher than the inside dew point. Not to get too nerdy here, but scientists and engineers separate heat into two categories: sensible and latent. Sensible heat relates to the heat required to change the temperature, and latent heat relates to heat that changes some property other than the temperature (for example, humidity). So in the case where the outside air is cooler but with a higher dew point, opening the windows would release sensible heat but introduce latent heat (heat that would have to be removed by the A/C unit when it condensates the water and lowers the humidity). In this case, you would want to make sure the enthalpy of the outside air is less than the enthalpy of the inside air. The easiest way to do this is through a psychrometric chart. Using this example, https://www.wikihow.com/images/thumb/e/ec/Read-a-Psychrometric-Chart-Step-6.jpg/aid10153214-v4-728px-Read-a-Psychrometric-Chart-Step-6.jpg, observe the diagonal lines for constant enthalpy, the horizontal lines for dew point, and the vertical lines for temperature. If the outside air has more enthalpy than the inside air for the given temperature and dew point, opening the windows would be counterproductive.

Boofinator

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Re: What did you do to keep your house cool?
« Reply #116 on: August 12, 2019, 12:15:44 PM »
Thank you @Boofinator for that description. That may have been the most helpful bit of information I read so far on this issue although I also am still a bit confused.

Not to over simplify, but it sounds like as long as the dew point is similar from outside to inside and condensation won't form on the windows, then I should be ok to leave them open and not worry about too much moisture coming inside the home?

Yes, you are correct: if the dew point is the same inside and out, then you need not worry at all about moisture coming in. Things get a little tricky during the summer months if the outside dew point is higher than the inside dew point. Not to get too nerdy here, but scientists and engineers separate heat into two categories: sensible and latent. Sensible heat relates to the heat required to change the temperature, and latent heat relates to heat that changes some property other than the temperature (for example, humidity). So in the case where the outside air is cooler but with a higher dew point, opening the windows would release sensible heat but introduce latent heat (heat that would have to be removed by the A/C unit when it condensates the water and lowers the humidity). In this case, you would want to make sure the enthalpy of the outside air is less than the enthalpy of the inside air. The easiest way to do this is through a psychrometric chart. Using this example, https://www.wikihow.com/images/thumb/e/ec/Read-a-Psychrometric-Chart-Step-6.jpg/aid10153214-v4-728px-Read-a-Psychrometric-Chart-Step-6.jpg, observe the diagonal lines for constant enthalpy, the horizontal lines for dew point, and the vertical lines for temperature. If the outside air has more enthalpy than the inside air for the given temperature and dew point, opening the windows would be counterproductive.

Upon further reflection, my above statement holds true given a single exchange of air between inside and outside with perfect insulation, but if you consider a thermal mass component some interesting things are going on. In this case, the air inside the house quickly reaches the outside ambient dew point (humidity), but due to thermal mass of the materials inside the house, the air will continue pulling energy from inside due to the temperature difference for many hours after the windows open. The effect of this would be two-fold (both owing to thermal mass contributions): 1) on the downside, the temperature inside will remain elevated from the outside temperature, thereby in the short-term (the dynamic phase) the room will get hotter (sensible heat decreases much slower than latent heat increases); 2) on the upside, the energy will be continually decreasing due to the thermal mass, so that at steady-state equilibrium the total enthalpy of the air inside the house with equal that of outside, but the total energy (to include that lost from the thermal mass) will be much much lower, thereby saving a lot of energy.

So in summary, if there was a situation where the enthalpy inside and outside were equal with the outside being cooled but more humid, opening the doors would save you energy while at the same time making you much hotter at the beginning due to the different time constants associated with the latent and sensible heat changes.

v8rx7guy

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Re: What did you do to keep your house cool?
« Reply #117 on: August 12, 2019, 12:45:54 PM »
We just installed Gila Brand Tint to our west-facing sliding glass door.  We chose the 70% blockage tint as we would still like some light to come in during the winter.  So far, so good... installation was tedious, but there's a lot of forgiveness built into the product.  Love the look and it has cut down on a lot of heat entering our home.
« Last Edit: August 12, 2019, 12:49:40 PM by v8rx7guy »

BTDretire

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Re: What did you do to keep your house cool?
« Reply #118 on: August 14, 2019, 09:00:42 AM »
We do not have AC.  We are FIREd so have someone at home most days - this is our strategy:

Open all windows at night as long as the temperature outside is cooler than inside.

Keep all shades pulled on the E and S sides of the house in the morning

Open windows on the N and W sides of the house. 

Turn on fans (ceiling fans are worth considering if you don't have them) to circulate cooler air throughout the house as long as outside air temp is cooler than inside.

Close windows as outdoor temp crosses indoor temp.

Pull shades on W side of house.
When I lived in Michigan, our home had a fan mounted in the ceiling, that sucked air from the home and pushed it into the attic. At night we would turn that fan on and open a window in the bedroom a few inches. This created a breeze into the window and across our bed. It drew in the cool night air, it was great!
 The fan was in the hallway, kind of central in the home, so it would work in any room.

El_Mariachi

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Re: What did you do to keep your house cool?
« Reply #119 on: August 26, 2019, 10:20:18 AM »
Our house has the attic stairs about 3ft from the return register for the HVAC

during the summer the attic stairs door is hot to the touch, so I made a box out of polyiso sheet and put weather stripping on the bottom and made a sealing flange on the stairs, so it fits over the stairs

now the attic stairs door is cool and I have noticed our HVAC runs a lot less during the summer

Another thing is sealing all the doors

I have been really considering having a company come and do that spray inwall foam to the sunny sides of our house

Also been thinking about adding sheets of foil faced polyiso in between the rafters to build up the R value

ChpBstrd

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Re: What did you do to keep your house cool?
« Reply #120 on: August 26, 2019, 11:08:21 AM »
Anyone else looking into solar powered AC / heat pump units? I would be happy to skip the cost and depreciation of batteries because if you need AC its usually because the sun is shining. More cheap panels would make up for a lack of expensive batteries. An auxiliary unit could prevent the central AC from kicking on as often and maybe save a couple hundred per summer.

The point where I lack understanding is how to wire it so that it only turns on the AC when there is sufficient wattage available.

Example:

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F143349564722

robartsd

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Re: What did you do to keep your house cool?
« Reply #121 on: August 29, 2019, 10:31:10 AM »
Anyone else looking into solar powered AC / heat pump units? I would be happy to skip the cost and depreciation of batteries because if you need AC its usually because the sun is shining. More cheap panels would make up for a lack of expensive batteries. An auxiliary unit could prevent the central AC from kicking on as often and maybe save a couple hundred per summer.

The point where I lack understanding is how to wire it so that it only turns on the AC when there is sufficient wattage available.

Example:

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F143349564722
Biggest problem with this plan is that the A/C compressor needs a lot of power on startup, then moves to a lower power level while running. If you size the solar to be able to start the system up, you'll have a lot of wasted capacity (still might be cheaper than mixing in a battery though). If you did add a battery to assist with startup, a lithium chemistry is likely best - doesn't mind extended periods of low charge, can absorb/release energy quickly relative to capacity/size.

ChpBstrd

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Re: What did you do to keep your house cool?
« Reply #122 on: August 29, 2019, 11:40:14 AM »
Anyone else looking into solar powered AC / heat pump units? I would be happy to skip the cost and depreciation of batteries because if you need AC its usually because the sun is shining. More cheap panels would make up for a lack of expensive batteries. An auxiliary unit could prevent the central AC from kicking on as often and maybe save a couple hundred per summer.

The point where I lack understanding is how to wire it so that it only turns on the AC when there is sufficient wattage available.

Example:

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F143349564722
Biggest problem with this plan is that the A/C compressor needs a lot of power on startup, then moves to a lower power level while running. If you size the solar to be able to start the system up, you'll have a lot of wasted capacity (still might be cheaper than mixing in a battery though). If you did add a battery to assist with startup, a lithium chemistry is likely best - doesn't mind extended periods of low charge, can absorb/release energy quickly relative to capacity/size.

Ive thought about this too. The price of panels is falling faster than the price of batteries, so having more panel capacity than needed is at some point more economical than having a steadily-deteriorating battery.

middo

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Re: What did you do to keep your house cool?
« Reply #123 on: August 29, 2019, 02:17:26 PM »
Anyone else looking into solar powered AC / heat pump units? I would be happy to skip the cost and depreciation of batteries because if you need AC it’s usually because the sun is shining. More cheap panels would make up for a lack of expensive batteries. An auxiliary unit could prevent the central AC from kicking on as often and maybe save a couple hundred per summer.

The point where I lack understanding is how to wire it so that it only turns on the AC when there is sufficient wattage available.

Example:

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F143349564722
Biggest problem with this plan is that the A/C compressor needs a lot of power on startup, then moves to a lower power level while running. If you size the solar to be able to start the system up, you'll have a lot of wasted capacity (still might be cheaper than mixing in a battery though). If you did add a battery to assist with startup, a lithium chemistry is likely best - doesn't mind extended periods of low charge, can absorb/release energy quickly relative to capacity/size.

I’ve thought about this too. The price of panels is falling faster than the price of batteries, so having more panel capacity than needed is at some point more economical than having a steadily-deteriorating battery.

There are other solutions to this using capacitors.  It was all the rage to build your own "mini-maximiser" in renewable energy / small hold farming circles a while ago.  I'll see if I can find any links.

Here is one that may give you an idea of what is possible:

http://www.voltscommissar.net/minimax/minimax.htm
« Last Edit: August 29, 2019, 06:08:21 PM by middo »

GuitarStv

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Re: What did you do to keep your house cool?
« Reply #124 on: August 30, 2019, 07:07:43 AM »
Yay!  We appear to have reached the glorious time of year where it cools off and humidity isn't too high at night so we can leave the windows open.

ChpBstrd

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Re: What did you do to keep your house cool?
« Reply #125 on: August 30, 2019, 10:52:47 AM »
Anyone else looking into solar powered AC / heat pump units? I would be happy to skip the cost and depreciation of batteries because if you need AC its usually because the sun is shining. More cheap panels would make up for a lack of expensive batteries. An auxiliary unit could prevent the central AC from kicking on as often and maybe save a couple hundred per summer.

The point where I lack understanding is how to wire it so that it only turns on the AC when there is sufficient wattage available.

Example:

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F143349564722
Biggest problem with this plan is that the A/C compressor needs a lot of power on startup, then moves to a lower power level while running. If you size the solar to be able to start the system up, you'll have a lot of wasted capacity (still might be cheaper than mixing in a battery though). If you did add a battery to assist with startup, a lithium chemistry is likely best - doesn't mind extended periods of low charge, can absorb/release energy quickly relative to capacity/size.

Ive thought about this too. The price of panels is falling faster than the price of batteries, so having more panel capacity than needed is at some point more economical than having a steadily-deteriorating battery.

There are other solutions to this using capacitors.  It was all the rage to build your own "mini-maximiser" in renewable energy / small hold farming circles a while ago.  I'll see if I can find any links.

Here is one that may give you an idea of what is possible:

http://www.voltscommissar.net/minimax/minimax.htm

Great link. Probably best for me to start by buying an old electrical engineering 101 textbook off eBay! This is a lot more complicated than house wiring.

WhiteTrashCash

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Re: What did you do to keep your house cool?
« Reply #126 on: August 30, 2019, 11:01:22 AM »
The last couple days have been amazing outside, so I have had the AC off and the windows open. It's glorious. I also discovered that Carrier finally updated their smartphone app so now at last I can remotely control my HVAC as they had promised when I bought the system. Hooray!

Boofinator

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Re: What did you do to keep your house cool?
« Reply #127 on: August 30, 2019, 03:26:23 PM »
An amusing, tangentially-related observation: Somehow I got on this "Nextdoor" group, where people gripe and moan about all sorts of shit. The latest was a conspiracy by the energy company to overcharge customers. Dozens must have chimed in agreement, because they couldn't ever remember having $400 or $500 energy bills before. I resisted posting that my bill was about 10% of theirs, for fear I'd have an angry mob with torches and pitchforks at my door later that night.

peterjane2727

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Re: What did you do to keep your house cool?
« Reply #128 on: February 01, 2020, 04:05:10 AM »
things to help keep the house cool:

1. Keep the blinds finished to keep off direct daylight.

2. Mop the floors with virus water.

3. Put a major can of ice before a fan and let the air blow over it.

4. can also use any dehumidifier which is best suited some are there https://www.amardeepchair.com/   

4. During the evening, open a window toward one side of the house, and another where you need to be coolest. Put a fan in the far window so it hauls the warm let some circulation into. In the first part of the day, or when it begins getting warm, close the windows to keep the sight-seeing out.

That was helpful, thanks a lot.

Sun Hat

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Re: What did you do to keep your house cool?
« Reply #129 on: February 13, 2020, 08:22:29 AM »
I added attic and wall insulation a couple of years ago to reduce my winter heating bill and have been quite happy with how it insulates from the summer heat as well. A light exterior wall colour also helps (it has less of an impact in the winter because the sun's rays are weaker and at a higher angle).

I'll second (or third) the recommendation for cellular shades - I have them on my south-facing windows and they make a huge difference. I have insulated drapes on my north facing bedroom window and it does wonders to keep the winter cold out, so I'd wager that they'd work to keep heat out of sunnier windows too.

In the summer, I also run the furnace fan even when the AC isn't on, because it circulates the cool basement air throughout the house.

GuitarStv

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Re: What did you do to keep your house cool?
« Reply #130 on: February 13, 2020, 09:37:25 AM »
We use remarkably little energy to cool the house at this time of year.

Sun Hat

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Re: What did you do to keep your house cool?
« Reply #131 on: February 13, 2020, 09:47:09 AM »
We use remarkably little energy to cool the house at this time of year.

Smartypants.

lutorm

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Re: What did you do to keep your house cool?
« Reply #132 on: February 13, 2020, 10:41:24 AM »
I didn't read through this whole thread now, but I think the correct strategy for "keeping your house cool" depends a lot on what kind of climate you live in. A strategy that's effective in Tucson is probably not going to work as well in Hawaii, and vice versa.

Here in Hawaii, I think there are two magic ingredients to keeping your house cool: Lots of airflow, and attic insulation. If your house is exposed to the trade winds and you are able to open up windows so you get cross flow through the house, you're going to be set. Insulating the attic (or adding PV!) to prevent the roof from radiating heat into the living space is the only other thing that you might need. Sun shining in through the windows, or even heating the sides of the house, is basically not an issue because the Sun is always very high in the sky and all houses here have 3,4, or even 5' eaves because of all the rain.

Now, if your house is sheltered from the trades, it will likely get miserably hot. The other viable strategy then is to seal yourself in and use AC, but that will be very expensive given power is $0.35/kWh.

This strategy works because while the Sun is strong here, the winds are always a pleasant temperature since they are regulated by all the water around. It's not going to work in an inland situation where the surrounding land heats up during the day.