Chart absolute humidity in air

Migrated from:

The relative humidity thrashes around as the temperature fluctuates. Could you have an option to display absolute humidity (water weight in air)? (EDIT: Dew Point would be a good measure of this, thanks @daintytomato)

Water Vapor in Air shows 70 degrees 70%rh = 75 degrees 60%rh = 80 degrees 50%rh

By looking at absolute water vapor, you could tell if you are humidifying your house by opening your house during a cool night.

daintytomato commented on Jul 18, 2019

I second this. An alternative metric that could provide this information would be dewpoints. It’d be awesome if you could view the outside and inside dewpoints temperatures. If the dewpoint outside is lower, then you know you won’t be adding humidity to your house when you open your windows.

A benefit to using dewpoint as a metric would be that you could get an idea of whether stuff is going to condense in your house (or the cooler rooms of your house) based on the temps in those rooms and the dewpoint temp. It also has the same units as temperature and could easily be plotted on the same graphs (vs. absolute humidity of 0.005 lbs water vapor per lb air).

It would be awesome if this could be added!

ghfields commented on Jul 18, 2019

I agree. Dew point is a much more known metric to describe absolute humidity.

In Celsius (±1%):
Dew Point=Temperature - ((100-Relative Humidity)/5)

Or you could get even more accurate with another found on Dew point - Wikipedia

ziebelje commented on Jul 22, 2019

Hey guys, thanks for the great feedback. Let me do a little reading to make sure I have a proper understanding of all this. At a glance it doesn’t sound too bad and I’ve had a bit of other feedback about humidity so this is something I’d like to improve. Stay tuned!

ziebelje commented on Jul 25, 2019

Dew point is present in the weather data provided by ecobee (originally provided by DarkSky). It is not available historically.

  1. I have no idea if dew point is measured or calculated.
  2. I can calculate dew point historically with temperature and RH (Dew Point Calculator - Find The Dew Point)

Charting absolute humidity would be nice for colder climates. When you’re heating and the outside air temperature is below freezing there’s very little water in the air even if it is saturated and at 100% RH. Any air infiltration means you can have saturated outside air leaking in and lowering your home’s humidity.

I’m probably going to lose some folks using the heathen metric system but just to give you an idea:

Comfy setpoint for at home in winter is 22C (72F) and 30% RH = 5g water per kg air

Outdoor temp is 0C (32F) and air is saturated at 100% RH = 4g water per kg air

Even saturated air at 0C will lower your home’s humidity if it gets in and it gets worse as the temp drops.

Outdoor temp was -35C (-31F) this week and 60% RH = .24g water per kg air. When you heat that air to 22C it has an RH of 1.7%.

Graphing absolute humidity would help show why your humidifier is running even though the RH outside is high. It’s also a good metric to see how airtight your house is as well insulated doesn’t necessarily mean “tight”. It’d be interesting to graph how fast your home is leaking air by watching how fast the absolute humidity drops/rises to the outside level.