How to build a DIY timber drying kiln

[Big J]

1) Not really, other than rails.

2) No. I'd stick with lorry backs as they are much cheaper. As well as over £600 in insulation, you have all your time in insulating it.

3) Put rails in. You will need something fairly industrial to push the stack in and out.

4) I wouldn't go to 40ft. Better with two 20ft kilns. Consistent airflow would be very tricky to achieve over that length, and you'd need a lot of rails!

[WilliAm444]

Just wondering if you think this could be done on a smaller scale say 4 cubic meter sized kiln?

[Big J]

I don't see why not. You just need to scale it down considerably.

[donnk]

very interesting.

 

Would a split system air conditioner be a better solution as they will be much more efficient that oil rads ?

 

I would be inclined to glue sheets of celotex all over the sided and roof to insulate it even more.

 

Maybe have an industrial dehumidifier as well, the type jewson hire out to dry flooded homes.

[Big J]

I did have an industrial type dehumidifier (Ebac) which was unreliable.

 

I don't know about the air conditioning system. The reason I like the set up that I have is that it is absolutely reliable. I can go on holiday without worrying that it will fail or damage the timber. The absolute reliability and consistency is worth a slightly higher running cost. That and it costs nothing to set up.

 

I wouldn't bother with the extra insulation. That is only worth while on a closed system, which with the heat vent it is not.

[CDMR]

Thanks for posting this Big J. Just finished building mine based upon these principles. Slight variation in so much as it is in a garage so I effectively built a stud wall box to insulate it with a compartment at one end containing the fan, a cheapo convection heater and the heat recovery unit with the controls on the outside. The three door panels lift out to allow the timber to be stacked. It's completed its sea trials so the first batch of timber will go in this afternoon.

 

[CDMR]

A coupe of pics of the controls. The radial knob controls the fan speed. The thing below is the thermostat for the heater, the light switches control the heat exchange and the big read out is the weather station reporting on what is going on inside.

 

The plant looks a bit better boxed in. The top hole is the fan outlet. The slidey letter box takes in air to the heater, the white grill takes air to the heat exchanger the output of which is fed to the underside of the heater. The dangly wire is the thermistor to control the thermostat.

[donnk]

excuse my ignorance, wouldnt it be easier and cheaper to seal the chamber pretty airtight with plastic and then put a nice big de-humidifier in it as they are very cheap to run. 

[CDMR]

1 hour ago, donnk said:

excuse my ignorance, wouldnt it be easier and cheaper to seal the chamber pretty airtight with plastic and then put a nice big de-humidifier in it as they are very cheap to run. 

From what I understand there are limitations on size for that approach and an increase in the length of time taken to dry larger 'wetter' bits of timber. Hopefully someone more knowledgeable will be able to cite specifics. In terms of sealing, I have siliconed up the gaps and may well paint the interior with egg shell at some point but OSB is pretty vapour impermeable as is.

[Big J]

That looks like a professionally installed kiln CDMR - much more so than mine! 

 

Donnk - in some instances a dehumidifier might be cheaper to run, but I found the difference to be very small on the larger kilns we have. There is also the reliability aspect as dehumidifiers break down a lot unless specifically designed to dry timber. The heat recovery units do recovery a fairly high percentage of the heat, so it's not wasted.