# Dew point (calculation, store, and use in next condition/automation)

Hello,

In yet implemented device in HA - with value of temperature and humidity - I want to store and work with the dew point.

Dew point formula
Tdp =(243.04 × [ln(RH/100) + ( (17.625×T) / (243.04+T) )]) / (17.625 - [ln(RH/100) + ( (17.625×T) / (243.04+T) )])

where
Tdp is Dew Point Temperature (°C)
RH is the relative humidity (%)
T is the temperature (°C)

How can be such dew point function added to HA and how can be possible:
A. store graph of dew point (calculated by formula),
B. Use calculated dew point in next condition or automation (without again usage of long dew point formula), please?

Thanks.
Any suggestion?

add repository: `https://github.com/dolezsa/thermal_comfort`

Thank you, but it showed info, not valid add on - screenshot attached.

Found, I was in wrong integration.
Now working.
Thanks once again.

1 Like

Hi there,
I was wondering what the use case was for dew point here?
I’m trying to figure out a smart way to turn on the extraction fan in my basement to control humidity but not sure if dew point is important there.

Yes, dew point can be interesting sometimes. If you have some cool surfaces, like cooling water systems or air-conditioners without a condensate water pump.

Example:

A cooling water pipeline in an machine room normally runs on 7 degree Celsius. If it is not insulated, and the dew point is higher than that, like 13 degrees, water will condensate on the surface of the piping.
That is an unwanted situation.

So in some environments it is common to set the temperature of the cooling system just above the dew point to maintain dry piping on the surface.

Example 2:

I have a summer house in another country, which is empty in the winter months.
I always maintain a inside temperature a bit higher, that the dew point, to avoid water condensation on the walls in the house, which can be disastrous.