[Molaroid]

My shed is a substantial 8' x 10' one. I insulated it with 50mm Jablite and lined it with 4mm ply. It stays cool in the summer, much more pleasant to work in than my old one.

In the winter I use an 800w oil-filled radiator on it's frost-free setting. This keeps the damp out no bother without costing the earth to run. Easy to up the heat for a bit if I'm working in there, but with the insulation even having the lights on in there helps keep it warm.

A dehumidifier IMHO is only really necessary if damp is a real problem, and then only until the place is dried out and the source of the damp isolated and cured. Definitely not a long-term thing.

Glen.

My shed is 47' x 13', so whatever heating I use it is going to cost a bomb. I am in the middle of a DIY solar heater to help but realise electrickery or another form fuel will be needed.

I think EvilC has a point about natural retention of water in the building materials, so just going to try different methods and see what works.

 

[madmike01uk]

I've got condensation issues in my concrete section garage, I'm looking at ordering one of these http://www.dry-it-out.com/DD822-Graphite-dehumidifier I've spoken to them and they said running it 24/7 should cost around £10 p/m. I've also seen RH plots and it can keep humidity at a really good constant when set at 60%.

 

[evilC]

It is very unlikely that you would get a consistent RH in a concrete section garage. The fundamental problem is that the garage will be draughtly and the 'U' value (thermal conductivity) of the concrete panels will be low that means the condensation will occur on the face of the concrete naturally. All you are doing with the dehumidifier in a garage is trying to dehumidify the world. In fact rather than using a dehumidifier you would be better providing a good ventilation system. You could seal the whole garage, add insulation and then dehumidify if you wanted to but that would be an expensive exercise.

 

[madmike01uk]

It is very unlikely that you would get a consistent RH in a concrete section garage. The fundamental problem is that the garage will be draughtly and the 'U' value (thermal conductivity) of the concrete panels will be low that means the condensation will occur on the face of the concrete naturally. All you are doing with the dehumidifier in a garage is trying to dehumidify the world. In fact rather than using a dehumidifier you would be better providing a good ventilation system. You could seal the whole garage, add insulation and then dehumidify if you wanted to but that would be an expensive exercise.

Even with good ventilation you will still be at around 85% RH. The garage is not that drafty and I've seen logs of this humidifier in a similar application (not by the distributor I add). The RH stayed within 5% of 60% at all times except for a power cut where by it shot up to 90% in a very short period.

 

[Molaroid]

I've got condensation issues in my concrete section garage, I'm looking at ordering one of these http://www.dry-it-out.com/DD822-Graphite-dehumidifier I've spoken to them and they said running it 24/7 should cost around £10 p/m. I've also seen RH plots and it can keep humidity at a really good constant when set at 60%.

How does that work, even at basic £0.10 pkW gives you 134 watt hours per hour in a given month, based on the device you link to, it is rated at a maximum of 620W, you would have to assume that the ultra quiet mode is nearly a fifth of it's actual power capacity - which means a fifth of its ability to do the job!

 

[evilC]

Even with good ventilation you will still be at around 85% RH. The garage is not that drafty and I've seen logs of this humidifier in a similar application (not by the distributor I add). The RH stayed within 5% of 60% at all times except for a power cut where by it shot up to 90% in a very short period.

The internal RH will be a function of the amount of moisture in the air and the air temperature. For the RH to be @ 85% internally then its got to be raining i.e 100% RH outside assuming inside is slightly warmer than outside.
If the RH stayed at 60%+/-5% then I doubt that it was actually switched on!
During winter it is quite feasible for the external RH to get down to 30% so the inside of the garage will be even less.

 

[madmike01uk]

How does that work, even at basic £0.10 pkW gives you 134 watt hours per hour in a given month, based on the device you link to, it is rated at a maximum of 620W, you would have to assume that the ultra quiet mode is nearly a fifth of it's actual power capacity - which means a fifth of its ability to do the job!

It cuts in and out and doesn't run all the time

 

[madmike01uk]

The internal RH will be a function of the amount of moisture in the air and the air temperature. For the RH to be @ 85% internally then its got to be raining i.e 100% RH outside assuming inside is slightly warmer than outside.
If the RH stayed at 60%+/-5% then I doubt that it was actually switched on!
During winter it is quite feasible for the external RH to get down to 30% so the inside of the garage will be even less.

http://www.dry-it-out.com/car-storage-faq here is a nice link on humidity in garage applications.

and here is a nice plot from someone that installed one in an observatory

http://stargazerslounge.com/member-...om/member-equipment-reviews/127448-ela-dd822-rotary-desiccant-dehumidifier.html

 

[evilC]

http://www.dry-it-out.com/car-storage-faq here is a nice link on humidity in garage applications.

and here is a nice plot from someone that installed one in an observatory

http://stargazerslounge.com/member-...om/member-equipment-reviews/127448-ela-dd822-rotary-desiccant-dehumidifier.html

The info on applications to garages presupposes that the garage is reasonably airtight and therefore the internal environment is relatively stable. Moving a car in or out over a short time span won't change the internal conditions much so it can be tolerated. But what you have probably is a leaky (air) concrete garage where the internal environment will be close to the external environment and any dehumidifier will battling against the odds.

The observatory example is not relevant to your situation as it appears to be a heated part of a house aand therefore reasonably saeled. Besides the test period is only over about 24hrs in the middle of winter at the beginning of this year. I would be interested to know what the weather conditions were to give an external RH of 60%? If I recall it was very cold and dry so the RH ought to have been very low.

Sorry to be so negative but you are expecting a miracle cure without understanding or rectifying the basics.

 

[Molaroid]

Quick update, bought a desiccant dehumidifier and have had it running for several days (intermittently). It's a 10L/day unit which cost around £150 and it works a treat.

Two things I picked up on, compressor dehumidifiers need a small window of temperature and RH to achieve their stated litre draw, whilst desiccant will work to quite low temperatures and overtake compressor units quite quickly comparative to litre draw.

I have got my RH down from 97% to an average of 62% in the few short days is has been runnng. I also installed two 320W tube heaters to stop frost which has worked a treat and heated up the entire shed around 8' plus. Whilst this doesn't sound much, for a shed, its positvely tropical.

Conclusion? If anyone is reading this as they did a search and have similar questions, get a desiccant with a minimum of 3/4 litre draw and/or drain tube, go for 7/10L or more and make sure it has some form of control. Oh and fit some basic heating.

 

[metric_thumbs]

I run a dehumidifier in my garage. Taking all of evilC's points as a good area to consider, I will say my garage is old and thus dry, I have made an attempt at stopping draughts except for one air brick and I also keep it above 4 degrees C temp. Dew point and all that

It appears to work very well. Also if I bring the car back and garage it damp the amount of water that is pulled out is amazing, say 1 litre from a car with a few rain drops on it. This is not the air, as after the first litre it goes down to a stable amount.

Get one is my recommendation.