Timber frame monitoring

[leucothea]

I built a little setup that lets me monitor the temperature and humidity at the end of long Ethernet cables. I used DHT22 sensors plus and Arduino Uno for readout.

I’m thinking to fix these sensors and cables in a couple places in air gaps inside my timber frame before it’s rendered over.

My thought is to monitor the humidity as the timbers dry out completely and catch any increases in humidity arising from unanticipated water ingress.

However, I’m wondering whether I will be able to collect any actionable information, given that air humidity is not the same as wood humidity. What kind of humidities would be healthy in enclosed environments like this?

Has anyone else tried something similar?

I’ve also considered making a proper wood humidity sensor, which doesn’t seem that difficult. But with this I would only be making measurements of individual bits of wood rather than sampling the general environment.

 

[Toby Newell]

I built a little setup that lets me monitor the temperature and humidity at the end of long Ethernet cables. I used DHT22 sensors plus and Arduino Uno for readout.

I’m thinking to fix these sensors and cables in a couple places in air gaps inside my timber frame before it’s rendered over.

My thought is to monitor the humidity as the timbers dry out completely and catch any increases in humidity arising from unanticipated water ingress.

However, I’m wondering whether I will be able to collect any actionable information, given that air humidity is not the same as wood humidity. What kind of humidities would be healthy in enclosed environments like this?

Has anyone else tried something similar?

I’ve also considered making a proper wood humidity sensor, which doesn’t seem that difficult. But with this I would only be making measurements of individual bits of wood rather than sampling the general environment.

View attachment 13692

Clever idea. Not sure about specific accuracy, with a capacitive sensor you are measuring the humidity at the sensor, depending upon the position it could be a condensation point and could give false readings. If not it might work as a relative measurement device. The top devices use an RF method.

For accurate readings on wood you normally use a hygrometer hood so that the RH in the air can equalise with the MC in the wood.

 

[paulc]

I have several DHT22 type devices monitoring humidity & temperature. Out of the box, accuracy is not particularly good, and they need calibrating first. In use, you need the air to be circulating around the sensor or you risk getting false readings. Inside a cavity, I wouldn't imagine air circulation would be very high.
Reliability is another issue to consider - I've only had one DHT22 fail, and that was down to a rodent chewing through the cable. Fortunately, easily repaired/replaced. Got some thermocouples embedded in a wall that appear to have failed. Replacing them is going to be a destructive task that will have to wait for another day.

Personally, I'd use a couple of resistive sensors embedded in the timbers most at risk of getting damp. Plenty of simple circuits available, or you could go complex (wheatstone bridge plus opamp).