Subfloor Climate control

Hi I tried to find any thread that might be similar and couldn’t immediately which was surprising. So hopefully I have just failed to search enough…

Has anyone used Home Assistant to model and control fans to keep the crawlspace ventilated without adding moisture on hot days? I believe this requires you to monitor soil moisture, humidity, temperature, dew point of outside and inside air and pick the right times to move the different air masses in and out of the house. This could be improved if i was to take advantage of air pressure and outside wind speed.

To give you an idea the subfloor is most often over 70% and the floor has cupped in some places. So i want to fix that before i fix the flooring.

Or i could just run the fans all day and all night…

I have switched to Home Assistant from a DIY ESP8266 based approach to solving my subfloor humidity in my raised-wooden floor double-brick house.

Thanks to poor house design in the 1920’s there was insufficient natural vents which was fixed until the free air movement was largely obstructed by subfloor air con ducting throughout.

Anyone else doing this at all?

I am using dew point temperature calculations from the below to calculate the differential in outside air and subfloor air to make a decision to switch on the subfloor fans, once the relative humidity is higher than a maximum allowed (eg. 60%) and the air con is not cooling the house, and to switch off the fans otherwise.

In doing that I am trying to avoid making the problem worse, creating condensation under the wood floors, etc which could happen for multiple reasons eg: subfloor humidity is:

  • fine or high but outside air humidity is worse
  • high on a hot day but the air con is running
  • etc

I haven’t seen this mentioned in other threads here, but I hear you. Ventilation is essential for a subfloor. In NZ there are rules, but of course older houses are often a problem.

So short answer, I haven’t seen any other threads, but if you know how to work out when the fan should be on, HA can do it.

Thanks @nickrout

I have come some way since my original post, and absolutely agree HA can do it. Its probably now more for me a case of how many other tasks do i give the RPI and how much do I want to complicate it. Seems like the “productionising” is something to think about after having a few power failures and failed HA updates. eg a separate test environment. But its probably a small price to pay for having the whole rest of the world helping me build a simple fan control app, which enrich the quality of the solution.

I think now my focus is on the decision algorithm for fan control. Really interested if anyone else has a raised floor double brick house and needing to do/has done the same thing.

#ventilation #subfloor #crawlspace #humidity