Heating vs dehumidifying

[StringJunky]

Scenario; A room has a temperature of 10c and high humidity.  We want to increase the comfort of the occupier. Is it generally energetically more economical to bring down the humidity or warm up the room a few degrees to increase comfort? 

Edited November 30, 2023 by StringJunky

[studiot]

12 minutes ago, StringJunky said:

Scenario; A room has a temperature of 10c and high humidity.  We want to increase the comfort of the occupier. Is it generally energetically more economical to bring down the humidity or warm up the room a few degrees to increase comfort? 

That must depend upon why the humidity is as it is.

[StringJunky]

Just now, studiot said:

That must depend upon why the humidity is as it is.

Normal variation in ambient humidity. Any excess is due to human occupation. Let's assume there is no excess stored moisture in the surfaces... nothing is damp as such  in a long-term way..

[TheVat]

13 minutes ago, StringJunky said:

Scenario; A room has a temperature of 10c and high humidity.  We want to increase the comfort of the occupier. Is it generally energetically more economical to bring down the humidity or warm up the room a few degrees to increase comfort? 

I think humid air has two benefits in the cool season, one is comfort for skin and upper respiratory tract, the other is that humider air would have a bit more thermal capacity and reduce the number of heating cycles (I think most systems work more efficiently with longer spaced out cycles).  That's a guess, needs fact checking.  And I'm writing from a locale with distressingly dry winter air, where upping humidity is always desirable.  

[swansont]

2 hours ago, StringJunky said:

Scenario; A room has a temperature of 10c and high humidity.  We want to increase the comfort of the occupier. Is it generally energetically more economical to bring down the humidity or warm up the room a few degrees to increase comfort? 

Depends on what’s comfortable. 

90% relative humidity at 10 C will be 50% at 20 C. There’s about 9g/m^3 water; it takes 4.18 J/g to heat the water. Still, 50% isn’t particularly comfortable.

If you want to reduce the humidity, you will have to condense water out of it. That means cooling it a few degrees and having the water condense, the reheating the air. Condensation takes 2259 J per gram. 

Removing the water takes a lot of energy. 

[studiot]

I last studied comfort zones in environmental engineering in 1973 and have long since thrown all those old notes on the bonfire (to keep warm ?😀)

I'm sure the graphs of comfort zones, plotted on temperature - Humidity charts are on the net nowadays.

 

In the UK the Office, Shops and Railway Premises Act 1963 presribes a minimum work temperature of 16^oC

But 10^oC is rather cold., so I do't remember if this temperature is covered.

 

The current temperature in this home office room of mine is 14^oC and the humidity is 73%.

Since the outside temp was 1^oC last night and has been 3^oC all day, lifting it only 1 or 2 degrees certainly makes it fell better but doesn't really affect the RH meter much.

I'm sure I have seen a more recent stress tesing reasearch, and I think it was from the University of Bristol.

However BigG can only find this from November last year on the BBC

https://www.bbc.co.uk/news/health-63602501

I saw that programme as well.

 

sorry about the rushed spelling.

Edited November 30, 2023 by studiot

[StringJunky]

53 minutes ago, swansont said:

Depends on what’s comfortable. 

90% relative humidity at 10 C will be 50% at 20 C. There’s about 9g/m^3 water; it takes 4.18 J/g to heat the water. Still, 50% isn’t particularly comfortable.

If you want to reduce the humidity, you will have to condense water out of it. That means cooling it a few degrees and having the water condense, the reheating the air. Condensation takes 2259 J per gram. 

Removing the water takes a lot of energy. 

My portable dehumidifier is a desiccant type. The air that comes out is probably 3 or 4c higher in a 15' x 10' space. Consumption is 600w. Would 600w be fairly economical to makew the space what I call autumnal temperature; 14c. I  find it striking that people go through Autumn here with no heating, then come the proper cold, they whack  it up 6c higher or more than they were happy with the prior two months.

Edited November 30, 2023 by StringJunky

[swansont]

6 minutes ago, StringJunky said:

My portable dehumidifier is a desiccant type. The air that comes out is probably 3 or 4c higher in a 15' x 10' space. Consumption is 600w. Would 600w be fairly economical to makew the space what I call autumnal temperature; 14c. I find striking that people go through Autumn here with no heating, then come the proper cold, they whack  it up 6c higher or more than they were happy with the prior two months.

From what I’ve read, desiccant dehumidifiers are less energy-efficient than refrigerator types.

[StringJunky]

43 minutes ago, swansont said:

From what I’ve read, desiccant dehumidifiers are less energy-efficient than refrigerator types.

Right. I bought it because, apparently, it was the type most suitable for dehumidifying in the lower temperature range; sub 20's. My comfort range is about 12-15c, if the humidity is not too high. Sat down I'll be in a jumper, but if I'm active a t-shirt is fine.

@studiot Thanks for sharing your experience.  Do you think in some circumstances it makes more sense to deal with humidity rather than a low temperature. My thinking is, the heavier the air, the more efficient heat transfer is from skin to the immediate environment, so, making one colder.

4 hours ago, TheVat said:

I think humid air has two benefits in the cool season, one is comfort for skin and upper respiratory tract, the other is that humider air would have a bit more thermal capacity and reduce the number of heating cycles (I think most systems work more efficiently with longer spaced out cycles).  That's a guess, needs fact checking.  And I'm writing from a locale with distressingly dry winter air, where upping humidity is always desirable.  

Do you have a long seasonal transition period of high humidity with low temperatures, where you are, before the humidity plummets?

Edited November 30, 2023 by StringJunky

[John Cuthber]

It's complicated but for most people (unless they are doing a lot of physical work, 10 degrees will be too cold.
And that will be the case regardless of humidity.

If you just heat up the air the relative humidity will fall and that will also add to comfort.
The "wasted" energy from a dehumidifier will warm the room and be beneficial anyway.
But a heater is cheaper to buy.

There are books about this.
https://en.wikipedia.org/wiki/Thermal_comfort

[StringJunky]

9 minutes ago, John Cuthber said:

It's complicated but for most people (unless they are doing a lot of physical work, 10 degrees will be too cold.
And that will be the case regardless of humidity.

If you just heat up the air the relative humidity will fall and that will also add to comfort.
The "wasted" energy from a dehumidifier will warm the room and be beneficial anyway.
But a heater is cheaper to buy.

There are books about this.
https://en.wikipedia.org/wiki/Thermal_comfort

Thanks, JC. 

[studiot]

33 minutes ago, StringJunky said:

Right. I bought it because, apparently, it was the type most suitable for dehumidifying in the lower temperature range; sub 20's. My comfort range is about 12-15c, if the humidity is not too high. Sat down I'll be in a jumper, but if I'm active a t-shirt is fine.

@studiot Thanks for sharing your experience.  Do you think in some circumstances it makes more sense to deal with humidity rather than a low temperature. My thinking is, the heavier the air the more efficient heat transfer is from skin to the immediate environment, so, making one colder.

 

First a fact, then a staw poll of 1  my observations.

 

It is known that the body does not respond directly to the environmental temperatureby feeling hot or cold.

Don't forget that your temperature is regulated quite closely.

The feeling of hot or cold is most closely related to the rate of heat loss (or gain) and therfore theefoort the body has to put in to counteract that to maintain its temperature.

 

Having noted that fact, I have noticed a few things.

In colder times, you do not need to lift the temperature much above ambient to fell warmer and much more comfortable. I to 2 dgrees is enough for this effect.

I agree with your comment.

54 minutes ago, StringJunky said:

I  find it striking that people go through Autumn here with no heating, then come the proper cold, they whack  it up 6c higher or more than they were happy with the prior two months.

My experience is that when the temperature dropped from 20 most people say it's getting sold and bump up the temperature more than the difference.

After a period of acclimatisation they no longer do this until the pattern is repeated at 18, 16, 14, 12 etc, as the ambient steadily falls with the season.

Yet I find lifting from 12 to 14, 14 to 16, 16 -18 easily enough.

 

Secondly I find that people (myself included)  suddenly say it is getting cold on a falling thermometer but are perfectly happy with their preferred temperature (be it 15, 16 , 18 or whatever)  on a rising thermometer.

This is consistent with the fact that heat loss determines our 'temperature' sense.

I also think that raising the temperature 1  to 2 degress must lower the humidity a bit, even if it does not always show on my insensitive meter.

Hopefully this is of some help

[TheVat]

2 hours ago, StringJunky said:

Do you have a long seasonal transition period of high humidity with low temperatures, where you are, before the humidity plummets?

It's semiarid here, near the Wyoming border, so it's never all that humid and, going by the hygrometer I've got on the piano, the transition is fairly gradual.  It's 18 C atm, in that room, and 22% humidity.  So raising that would be a plus.  Some here opt for humidification built into their furnace.  Though, as pointed out, that can increase perceived chill.   

I think Americans overheat their homes and buildings, by European/UK standards.  The numbers people are giving here as norms would strike many of my compatriots as on the chilly side.  

 

[mistermack]

I always thought that a humid atmosphere feels warmer because perspiration evaporates a bit slower. 

[StringJunky]

1 hour ago, TheVat said:

It's semiarid here, near the Wyoming border, so it's never all that humid and, going by the hygrometer I've got on the piano, the transition is fairly gradual.  It's 18 C atm, in that room, and 22% humidity.  So raising that would be a plus.  Some here opt for humidification built into their furnace.  Though, as pointed out, that can increase perceived chill.   

I think Americans overheat their homes and buildings, by European/UK standards.  The numbers people are giving here as norms would strike many of my compatriots as on the chilly side.  

 

Yeah, 22% would dry out my throat and dry out more my already dry skin. In this country, mould is quite ubiquitous when people warm their houses and don't ventilate regularly. I can't think of many people that have air-con like you seem to have your side.

Edited December 1, 2023 by StringJunky

[TheVat]

13 hours ago, mistermack said:

I always thought that a humid atmosphere feels warmer because perspiration evaporates a bit slower. 

That seems true for when it's hot.  But it seems like humidity also heightens chill when temps are below a comfortable room temp.  I notice this visiting children in another state where it's far more humid.  10 C there feels colder than 10 C does here.  And in summer 30 feels hotter there than it does here.  

[iNow]

Water transfers heat against our bodies far more efficiently and intensely than air.  Your body temp will plummet getting into a bathtub with 80F water, but will be perfectly warm in 80F air. 

[StringJunky]

31 minutes ago, TheVat said:

That seems true for when it's hot.  But it seems like humidity also heightens chill when temps are below a comfortable room temp.  I notice this visiting children in another state where it's far more humid.  10 C there feels colder than 10 C does here.  And in summer 30 feels hotter there than it does here.  

Walk from a clear area into a mist, you feel the heat draining off you. A sustained period of low temps condenses the air from a previously warmer period; temperatures are always in transition and the atmospheric ensemble plays catch up.

Edited December 1, 2023 by StringJunky

[John Cuthber]

28 minutes ago, StringJunky said:

Walk from a clear area into a mist, you feel the heat draining off you.

Possibly because the reason why that area is misty is because it is cold.
Why else would there be mist there, but not elsewhere?

 

55 minutes ago, iNow said:

Water transfers heat against our bodies far more efficiently and intensely than air. 

Because it's over a thousand times denser.


Water vapour has a higher heat capacity than air, but a lower thermal conductivity.

If it's cold enough that you are not sweating (significantly) then the rate of evaporation is irrelevant to heat transfer. At 10C that probably applies.

It's well known that "other people's houses" feel colder for the same temperature- simply because you learn to avoid the drafts in your own house.

 

[StringJunky]

4 minutes ago, John Cuthber said:

Possibly because the reason why that area is misty is because it is cold.
Why else would there be mist there, but not elsewhere?

But what happens when the cold is sustained; it precipitates out and you are left with dry air. Dry-cold air is subjectively warmer than wet-cold air.

Edited December 1, 2023 by StringJunky

[John Cuthber]

2 hours ago, StringJunky said:

. Dry-cold air is subjectively warmer than wet-cold air.

That's debatable at best.
https://www.cbc.ca/news/canada/edmonton/the-science-says-there-s-no-difference-between-a-dry-or-a-wet-cold-sorry-1.6268564

[TheVat]

2 hours ago, John Cuthber said:

That's debatable at best.
https://www.cbc.ca/news/canada/edmonton/the-science-says-there-s-no-difference-between-a-dry-or-a-wet-cold-sorry-1.6268564

For many that's counterintuitive.  But it makes sense, where the amount of water in the air, in absolute terms, is so small.  I suspect some of that folk belief about cold relates to the situations like walking through a heavy mist or drizzle where cold moisture is reaching your skin in larger quantities and drawing more heat from it.   And you are then, as the article notes, not getting any warming from direct sun, adding even more chill.  

[mistermack]

12 minutes ago, TheVat said:

situations like walking through a heavy mist or drizzle where cold moisture is reaching your skin in larger quantities and drawing more heat from it. 

I think it might be more of a mental thing. I've noticed that the tiniest draught, nowhere near enough to affect my temperature, immediately makes me feel the cold, so changes in humidity might have a similar out-of-proportion effect. 

I use humidity to make my place more comfortable. The kitchen opens up to my tv room, and I just leave a huge pot on the gas ring simmering as low as it can go. If I don't do that, I find I need to turn the heat up a bit. That's at comfortable room temperature, of about 22 dec c on my digital wall clock. So for me, at that temp, raising humidity does make me feel warmer. In a cold room, judging by the study posted, it would probably have little or no effect, and just cause condensation. 

[StringJunky]

I found some numbers from a heating firm on most comfortable humidity levels at given temperatures.

For an outdoor temperature over 50˚F, indoor humidity levels shouldn’t exceed 50%
With an outdoor temperature over 20˚F, indoor humidity levels shouldn’t exceed 40%
Outdoor temperature between 10˚F and 20˚F, indoor humidity levels shouldn’t exceed 35%
For an outdoor temperature between 0˚F and 10˚F, indoor humidity levels shouldn’t exceed 30%
Outdoor temperature between -10˚F and 0˚F, indoor humidity levels shouldn’t exceed 25%
With an outdoor temperature between -20˚F and -10˚F, indoor humidity levels shouldn’t exceed 20%
Outdoor temperature at -20˚F or lower, indoor humidity levels shouldn’t exceed 15%

https://lauryheating.com/ideal-home-humidity/

[studiot]

9 hours ago, StringJunky said:

I found some numbers from a heating firm on most comfortable humidity levels at given temperatures.

For an outdoor temperature over 50˚F, indoor humidity levels shouldn’t exceed 50%
With an outdoor temperature over 20˚F, indoor humidity levels shouldn’t exceed 40%
Outdoor temperature between 10˚F and 20˚F, indoor humidity levels shouldn’t exceed 35%
For an outdoor temperature between 0˚F and 10˚F, indoor humidity levels shouldn’t exceed 30%
Outdoor temperature between -10˚F and 0˚F, indoor humidity levels shouldn’t exceed 25%
With an outdoor temperature between -20˚F and -10˚F, indoor humidity levels shouldn’t exceed 20%
Outdoor temperature at -20˚F or lower, indoor humidity levels shouldn’t exceed 15%

https://lauryheating.com/ideal-home-humidity/

If you google comfort zone you will get bogged down in psychobabble.

But comfort zone is also the correct term in environmental engeering.

 

here is the way to find the charts from google.

 

https://www.google.co.uk/search?q=human+comfort+temperature+and+humidity&sca_esv=587264773&ei=HhZrZae3LryshbIP29OHwAU&oq=temperature+humidity+comfort+zone+chart&gs_lp=Egxnd3Mtd2l6LXNlcnAiJ3RlbXBlcmF0dXJlIGh1bWlkaXR5IGNvbWZvcnQgem9uZSBjaGFydCoCCAAyChAAGEcY1gQYsAMyChAAGEcY1gQYsAMyChAAGEcY1gQYsAMyChAAGEcY1gQYsAMyChAAGEcY1gQYsAMyChAAGEcY1gQYsAMyChAAGEcY1gQYsAMyChAAGEcY1gQYsANIw1JQAFgAcAF4AZABAJgBAKABAKoBALgBAcgBAOIDBBgAIEGIBgGQBgg&sclient=gws-wiz-serp