Air conditioning raising controversy

[jmecklenborg]

Originally Posted by Camelback

Think about what there wouldn't be without simple things like electricity and cheap fossil fuels used to generate that electricity and grow our food.

We would have a global population of about 500 million to 1 billion and extensively less knowledge as a species.

Humans have barely gotten to this point of comfort and excess in a fraction of a blink of an eye in geologic time. (Refer to the UFO thread).

^Unfortunately, people waste most of their good health and free time watching TV, or more recently, screwing around on their phone keeping tabs on people they barely knew in high school.

[SFBruin]

Not me! I spend it screwing around on this website.

[dchan]

Originally Posted by jmecklenborg

What's insane is that people used to take summer vacations to Michigan or Canada or Highlands, NC to avoid summer heat. Now people...GO FURTHER SOUTH AND SIT IN AIR CONDITIONING.

Yeah, people would go to places further north (like NYC residents to the Catskills) to cool off. I go north during the summer because there's fewer people there, while I go to beaches to walk the boardwalk during the winter.

[dchan]

Our current target is not replacing the energy we use nowadays with "green" energies, but rather reducing the amount of electricity we use. The amount of fossil fuel energy available is enormous and a fairly cheaper than "green" energies, especially for the amount we currently use. IMO, it's a fools errand to attempt a 1:1 replacement with "green" energy".

One way to reduce energy usage is by making our building designs smarter and more energy efficient. A good low-hanging fruit is energy-efficient building design. Building designs have been terrible in terms of energy efficiency since forever, but mainly since the industrial revolution, when HVAC systems started to become invented and developed. With the ability to actively control our indoor environment, we mostly tossed aside thinking about the building envelope as anything other than keeping the rainwater and drafts out. And even for that task, our building envelope designs haven't be good.

If anyone is interested in building design improvements, this is a great website with lots of different resources "building science", including:
- ways to control bulk water and moisture through wall design
- where to put insulation within a wall, depending on climate
- vapor barrier design and usage, and how it can benefit or harm a wall

https://www.buildingscience.com/

Caution: some of the papers can be fairly technical and complicated.

[SFBruin]

Would shrinking the average square footage of a US home result in energy savings?

[Pedestrian]

Originally Posted by SFBruin

Would shrinking the average square footage of a US home result in energy savings?

Sure but better design could save even more. Roofs are a good example. The usual roof in most of the northern hemisphere is a dark color and made of material that absorbs solar energy to some degree though usually that has little effect heating the house because the same houses often have unheated attic space between the roof and the lived-in part of the home.

In hot climates, there are better options (and they are quite common in the US southwest:

. . . white elastomeric roof coatings can provide a solar reflectance over 90% in the first year and 78% after 3 years, and emit 86-87% of absorbed heat energy. While aluminum roof coatings are also highly reflective, they are not considered a “cool roof” coating because they only emit 50% to 60% of the absorbed energy. This means that aluminum roof coating will stay warmer at night, retaining heat, while a white roof coating will radiate much more of its stored heat. For this reason, aluminum will not perform quite as well as a white material with a similar solar reflectance.

While it’s true that a white elastomeric roof coating system is initially more expensive than aluminum coating, it can significantly improve operating costs, reduce utility bills, benefit the surrounding environment and have been proven to actually lengthen the lifespan of roofs… which over time make it the better investment.

https://www.roofers.org/news-informa...nergy-savings/



In this neighborhood in southern AZ, like many such, all the houses use white elastomeric roof coatings and, as mine does also, I can tell you how well they work. On a typical June day when the temperature will ultimately reach 105 degrees F, I usually set my thermostat at 68 degrees F at midnight when I go to bed. The next morning, when I get up, I turn the A/C off. The temperature inside the house usually doesn't get to about 78 (the upper level of my comfort zone) until about 3-4 PM, near the time the temperature outside is hitting that 105 degree mark. Then I turn the A/C back on set at 78 and that's where it sits until bed time.

[Camelback]

Originally Posted by Pedestrian

In this neighborhood in southern AZ, like many such, all the houses use white elastomeric roof coatings and, as mine does also, I can tell you how well they work. On a typical June day when the temperature will ultimately reach 105 degrees F, I usually set my thermostat at 68 degrees F at midnight when I go to bed. The next morning, when I get up, I turn the A/C off. The temperature inside the house usually doesn't get to about 78 (the upper level of my comfort zone) until about 3-4 PM, near the time the temperature outside is hitting that 105 degree mark. Then I turn the A/C back on set at 78 and that's where it sits until bed time.

Have you found your method to be more or less cost efficient?

I've always been told to not mess with the thermostat too much because keeping it set at a predetermined temperature around the clock is more cost efficient than off/on, off/on, off/on.

I think the thought is that the energy required to cool a warm house by 10 degrees is more than to cool it by 1 degree 10x/day? I guess it depends on the time of day too, energy prices can fluctuate peak vs. off-peak. Most people don't go to bed at 12am - 1am. Most prepare for bed 9pm - 10pm or earlier if they have kids.

[dchan]

Originally Posted by SFBruin

Would shrinking the average square footage of a US home result in energy savings?

Yes and no.

- Yes because there is less interior volume to heat & cool.
- No because smaller houses = larger building envelope area. Energy flows out of a building through its roof, walls, and below ground-level sections. By increasing more single family housing, you also increase the per-capita building envelope area.
- But also yes if you house more people in larger apartment buildings and attached housing (apartment buildings preferred).



Here is an article on Building Science about the topic, where the picture above is from, if anyone is interested:

https://www.buildingscience.com/docu...ape-and-energy

Originally Posted by Pedestrian

Sure but better design could save even more. Roofs are a good example.

Reflective roofing will for-sure help with reducing cooling energy usage. But it only effects climates where cooling predominates (hot and warm-temperate climates).

The better solution is increasing the insulation levels in roofing, preferably to R50+ (imperial units) while also thoroughly air-sealing the entire building envelope. This will help in both hot and cold climates.

For cold climates, heat mostly escapes through the roof rather than the side walls. This is not just because "hot air rises, and cool air sinks". It is also due to the stack effect, in which incoming cool air pushes warmer up, where it escapes through the attic roof and chimney:

Originally Posted by Camelback

I've always been told to not mess with the thermostat too much because keeping it set at a predetermined temperature around the clock is more cost efficient than off/on, off/on, off/on.

I think the thought is that the energy required to cool a warm house by 10 degrees is more than to cool it by 1 degree 10x/day?

The best way to think about it is this:
1. Temperature and heat transfer is mostly a linear relationship that depends on the difference in temperature between indoors and outdoors. Therefore, the difference in temperature in cold climates (70F - 20/30F = 40/50F) tends to be greater than the difference in temperature in hot climates (90-100 F - 70F = 20-30F). So it takes more energy to heat a cold building in the winter than to cool a hot building in the summer.
2. Not all HVAC methods are equal in terms of energy usage.
- Heating typically comes from boilers and furnaces using gas or oil. In some cases, it can come from resistance heating. In other cases, it comes from heat pumps.
- Cooling only comes from A/Cs utilizing the refrigeration cycle.

In terms of energy efficiency, here is a breakdown:
- gas or oil boilers: 70-95% efficient
- resistance heating: 100% efficient
- heat pumps or A/Cs: 200-400+% efficient

As you can see, heat pumps or A/Cs (both utilize the super-efficient refrigeration cycle) are far, far more efficient than other methods of heating. That's why most energy efficiency experts are pushing for electrification of HVAC in the near and far future.

[202_Cyclist]

First, I bought Carrier stock last year because people in cities like Seattle, Portland, and Boise who didn’t previously need air conditioning now need it.

One of the ways to reduce the need for air conditioning is for NIMBYs to get over themselves and allow more housing along the coasts of our cities located next to oceans. Instead of building along the coast of Southern California, where it is 20 - 30 degrees cooler during the summer and you usually get a nice breeze, most of the new housing has been built in the Inland Empire and the Santa Clarita Valley.

[202_Cyclist]

Similarly, our apartment in Washington is a couple of blocks from the Anacostia River. It is usually 5 - 10 degrees cooler there than the rest of Washington because of the reduced heat island effect by having the river instead of more built land, as well as the breeze from the river.

[Pedestrian]

Originally Posted by Camelback

Have you found your method to be more or less cost efficient?

I've always been told to not mess with the thermostat too much because keeping it set at a predetermined temperature around the clock is more cost efficient than off/on, off/on, off/on.

I think the thought is that the energy required to cool a warm house by 10 degrees is more than to cool it by 1 degree 10x/day? I guess it depends on the time of day too, energy prices can fluctuate peak vs. off-peak. Most people don't go to bed at 12am - 1am. Most prepare for bed 9pm - 10pm or earlier if they have kids.

That’s the thing—I don’t cool a warm house in the daytime. I usually turn the A/C on set to 78 when that’s the approximate temperature of the house. The point really was that it takes much of the day to warm up to that temperature because the roof radiates so much solar energy. It’s the benefits of a white reflective roof (yes, in a hot climate—but this thread is about air conditioning) I was trying to get across.

Late at night, when there’s obviously no sun, I do turn the thermostat down because I like it cool for sleeping—much cooler than I can be comfortable in the day and evening when I’m up. Theoretically when I get up in the morning I could just set the thermostat at 78 and the A/C likely wouldn’t come on until late afternoon when I turn it on anyway so I doubt turning it off like I do makes much difference.

I have noted when I turn the thermostat down from 78 to 68 at bedtime, it runs for about half an hour before stabilizing at 68. That doesn’t seem excessive.

[dchan]

^ Yes, I highly agree that a reflective roof is a great way to reduce heat within buildings. My point is that many climate zones are mixed, so buildings need to deal with hot and cold weather. For those climates, in addition to using reflective roofing, I advise substantially increasing the roof insulation as well as thorough air-sealing of the entire building.

I would also advise strategic window placement and shading.

Windows invite heat coming in through sunlight. You can control the amount of sunlight through strategic window placement. For now, I am speaking only for the northern hemisphere.
- Typically, north and south-facing windows are preferred.
- North windows won't get much (if any) direct sunlight.
- South windows get a ton of sunlight in the winter for free heat gain. This is because the earth is tilted so that the sun's rays are angled sharply from the south.
- South windows won't get too much sunlight during the summer because the sun is almost directly above.
- East and West windows are not so lucky. They will get tons of direct sun either in the morning or the afternoon. Try to avoid too many East and West windows

By shading the windows using outside shading (and not inside - by the time the sunlight passes through the window, it's already too late), you can substantially cut the amount of internal heat gains through excess sunlight.
- For south windows, you only need to shade through adequate roof overhangs or window overhangs. The summer sun is almost directly overhead, so you only need to block that portion of the sun.
- For East/West windows, you need more direct shading, including:
> Trees and fences
> Awnings
> External window blinds and shutters:




Also, you live in a desert climate, which is far different than most of the U.S. or the world. You may even benefit from a evaporative (AKA - swamp) cooler in your climate rather than air conditioning if you find the air too dry. That is because your climate only really deals with sensible heat (dry bulb temperature). The rest of the country (and much of the world) deals with sensible AND latent heat (wet bulb temperature), with much of our A/Cs and heat pumps trying to control the latent heat's moisture levels more than the sensible heat.

So although your advice is generally fine, your experiences also doesn't reflect what most of the country experiences.

[dchan]

Originally Posted by 202_Cyclist

One of the ways to reduce the need for air conditioning is for NIMBYs to get over themselves and allow more housing along the coasts of our cities located next to oceans. Instead of building along the coast of Southern California, where it is 20 - 30 degrees cooler during the summer and you usually get a nice breeze, most of the new housing has been built in the Inland Empire and the Santa Clarita Valley.

If we believe that climate change is happening and is mostly irreversible, then I don't think that's a great idea (at least the way we typically build it - cheap and fast). Go figure, right? Building housing near the coasts where it's less hot to reduce cooling demand in order to help reduce climate change. But climate change makes the ocean levels rise and swallow up that same housing. It's like a snake eating itself.

It's the same for building near rivers. They tend to flood after heavy rains. Traditionally, the wealthier people built their homes up the hill, while the poorer lived in lowlands.

I do think you have a point. In addition to implementing modern passive measures that we've developed through building science, we should also consider traditional cooling methods through older building designs that worked well and using the environment for our benefit.

[urban_encounter]

Originally Posted by SIGSEGV

While air conditioning is certainly nice, I don't understand why people set the temperatures so low. It doesn't need to be fucking freezing to be comfortable.

I have two luxuries in life that I’m unwilling to compromise; my cool apartment and my twice daily shower. Those are non negotiable. I will give up my car first.

[ocman]

So many issues could be solve if developers built homes the way they used to with real material instead of ticky tacky stuff that will last only 50 years.

[dchan]

Originally Posted by ocman

So many issues could be solve if developers built homes the way they used to with real material instead of ticky tacky stuff that will last only 50 years.

I think that's a big part of the problem. Developers want to build cheap and fast, and they basically use the same wall designs that we've been using for the past 70 years, with maybe some extra insulation in the cavities and a more modern vapor barrier.

To build a good house or building, constructors need to understand the following:

1. Good wall design should be based on each specific climate. Besides temperature differences, there is also humidity differences. Temperature and humidity will dictate which way the humidity will be driven towards in a wall.
(see bullet point 5).
2. Make all parts of the building envelope as airtight as possible
3. Add lots of insulation to the roof, where heat loss is typically the greatest for buildings.
4. Use reflective exterior materials to help reduce cooling demand
5. Good vapor barrier design. Vapor actually doesn't contribute that much to interior moisture levels. The vast majority of excess indoor humidity is due to leaky walls around gaps, holes, and transitions (wall-to-door, wall-to-window, etc.). HOWEVER, good vapor barrier design is needed because impermeable vapor barriers can trap moisture within wall cavities, leading to mold growth. The local seasonal climate will dictate which direction vapor will be driven towards (exterior-to-interior vs interior-to-exterior).
6. For exterior walls, it is much preferred to use continuous exterior insulation rather than cavity insulation.
7. Reduce and mitigate all thermal bridges, which act as a thermal conductor between inside and outside. In a well-insulated building, thermal bridges act as both a bridge to transmit heat through as well as a potential condensation point (which can result in mold growth).

[Stan31]

The problem isn't with AC but with source of energy generation. We just need to build more solar and wind power plants instead of manufacturing ways that ultimately make people less comfortable (less AC use, smaller apartments, etc)

I'm blasting AC non-stop in NYC and always have, it's an extreme environment in the summer and no one would live here without the use of air conditioning. In the olden days, rich people would desert NYC in the summer and poor people/slaves had no choice but to remain and suffer.

[dchan]

Originally Posted by Stan31

The problem isn't with AC but with source of energy generation. We just need to build more solar and wind power plants instead of manufacturing ways that ultimately make people less comfortable (less AC use, smaller apartments, etc)

I'm blasting AC non-stop in NYC and always have, it's an extreme environment in the summer and no one would live here without the use of air conditioning. In the olden days, rich people would desert NYC in the summer and poor people/slaves had no choice but to remain and suffer.

Not quite right. ACs may be fairly efficient machines, but they use too much electricity because the vast majority of buildings are leaky, don't have enough insulation, and are badly built in general. The solution to the problem is to improve existing and new buildings so that they use less energy for heating and cooling.

Your solution is to maintain our current levels of consumption while replacing fossil fuel energy with "green" energy. That doesn't really work. Generating this "green" energy on a 1:1 basis to replace fossil fuels also requires a massive amount of natural and man-made resources, creating a whole new set of problems. Think reduce, and not just replace and recycle.

[Stan31]

Originally Posted by dchan

Not quite right. ACs may be fairly efficient machines, but they use too much electricity because the vast majority of buildings are leaky, don't have enough insulation, and are badly built in general. The solution to the problem is to improve existing and new buildings so that they use less energy for heating and cooling.

Your solution is to maintain our current levels of consumption while replacing fossil fuel energy with "green" energy. That doesn't really work. Generating this "green" energy on a 1:1 basis to replace fossil fuels also requires a massive amount of natural and man-made resources, creating a whole new set of problems. Think reduce, and not just replace and recycle.

Yes, my building, despite being relatively new (2007), is highly energy inefficient, I think it got a 'D' by the city inspections. However, I don't have any research to support this, I doubt that 100 F temperature and extreme humidity can be reduced to a comfortable 68 F and dry without blasting AC.

There's probably a way to reduce it, requiring a massive reconstruction of the whole city, which I'm technically for, especially as a 'rule' for all new constructions, to make them more energy efficient, but we'll still only be mitigating our energy needs a little, while boosting our power generation capacity is the only solution for now.

Even if my building became 10% more energy efficient, I'll still be blasting AC off to maintain the 68 F indoor temperature and a comfortable dry air.

Are there even solutions to remove humidity without the use of electricity to any meaningful extent?

[dchan]

Originally Posted by Stan31

Yes, my building, despite being relatively new (2007), is highly energy inefficient, I think it got a 'D' by the city inspections. However, I don't have any research to support this, I doubt that 100 F temperature and extreme humidity can be reduced to a comfortable 68 F and dry without blasting AC.

There's probably a way to reduce it, requiring a massive reconstruction of the whole city, which I'm technically for, especially as a 'rule' for all new constructions, to make them more energy efficient, but we'll still only be mitigating our energy needs a little, while boosting our power generation capacity is the only solution for now.

Even if my building became 10% more energy efficient, I'll still be blasting AC off to maintain the 68 F indoor temperature and a comfortable dry air.

Are there even solutions to remove humidity without the use of electricity to any meaningful extent?

Yup, I've seen plenty of new glass buildings around the city with a D rating. BTW, those swampy conditions occur at 80-90F, not 100F, around the NYC area climate zone. We're not that bad yet.

The best way to reduce humidity is to plug up all holes in the facade. In other words, air-sealing. Most of the moisture comes through the air leaks, which carries warm humid air inside:



Of course, this by itself isn't enough in humid climates. Therefore, we need ACs. But we need to size the AC correctly (as Pedestrian mentioned several times on this thread) to properly deal with humid air. Moisture is only removed from the air if the AC coils remain cold (via condensation). If the AC coils don't stay cold, there is no moisture removed from the air. "Oversized" ACs, or ones with excessive design BTUs/KWs for the room size, cool a room way too fast to properly dehumidify the air. Therefore, while smaller "properly sized" ACs will cool a room more slowly, they will also dehumidify the air better in the process.

With that said, certain climates (such as the Southeast US) are way too humid. Even properly-sized ACs may not be enough to dehumidify the air adequately. In this case, you need to supplement an AC with a dehumidifier (see my other posts on this thread, #119 & 132, for more information). A dehumidifier is basically a AC with the fan reversed. It has cold coils to dehumidify the air, but then it blows the cold dried air on the hot condenser coils and compressor to warm the air. Warm dry air is better for dehumidification because warm air can hold more moisture than cool air.

So to answer your questions more succinctly:
- properly air-seal your outside walls, roofs, windows, outside doors, and around other exterior wall items. This will drastically cut down on the amount of moisture leaking into your building.
- there will still be humid air to deal with. Use a properly-sized AC to remove the moisture. For larger rooms, I recommend keeping the AC fans speed on low and using a separate fan to move the cool fan around the room.
- if an AC isn't good enough to dry to air, supplement it with a dehumidifier.