Question on Dehumidity V ventilation
Discussion
Ok need some advise, going to install a dehumidifer to help with the storage of the car,If you use one of these do you need to ventilate the garage as well. Does it help having both or is there no point. The garage is well insulated and has a false insulated ceiling. The garage is also heated to maintain a low background temperature, I would be using ventilation with heat recovery.
Your comments please
Thanks
Your comments please
Thanks
Ventilating the space by bringing in fresh air will only make the dehumidifier's job more difficult (and increase the heating cost). Introduction of fresh air into a space is only really useful if it's occupied by people.
Having said that, I'm a building services engineer and have no idea if 'stale' air might have a detrimental effect on the car?
What sort of conditions (temp/humidity) are you looking for?
Having said that, I'm a building services engineer and have no idea if 'stale' air might have a detrimental effect on the car?
What sort of conditions (temp/humidity) are you looking for?
Heskey said:
Whilst we're on this...
Driving anywhere, windows steam up a bit... Turn the heating up hot, turn the heating down cold, or sod the heating and open the window - Which is technically the best method for clearing fogged up windows?
I usually open the window and have the heater fan on full blast. Seems to work Driving anywhere, windows steam up a bit... Turn the heating up hot, turn the heating down cold, or sod the heating and open the window - Which is technically the best method for clearing fogged up windows?
Hunidity or what we normally measure, relative humidity, RH, is dependent on the temperature of the air. So if you take cold air with a high RH and warm it up, although the amount of moisture in the air is the same the RH will fall and it will feel dryer and you will remove condensation as the air will be able to absorb more moisture. So the best thing to do is warm the air up as quickly as you can. I haven't got all the calculation to hand, but i have loads of stuff on thermal stress and thermal comfort if anyone is sad enough to be interested 
hiltonig said:
Ok need some advise, going to install a dehumidifer to help with the storage of the car,If you use one of these do you need to ventilate the garage as well. Does it help having both or is there no point. The garage is well insulated and has a false insulated ceiling. The garage is also heated to maintain a low background temperature, I would be using ventilation with heat recovery.
Your comments please
Thanks
If you have ventilation you'll simply be trying to dehumidify the whole of the UK.Your comments please
Thanks
Seal the garage as best you can, run the dehumidifier as required, and all will be well. Stale air won't affect anything, unless you try to live out there.
What is this 'ventilation with heat recovery'?
hiltonig said:
as the garage is heated thought the heat recovery would not chuck all the hot air out. I guess the real question is that the ventilation would remove stale air but since its been dried by the dehumidify is there any problem/ benefit with that ???
If you remove the stale air, you'll be introducing humid air to the garage/car, and that'll need dehumidifying too. So pretty pointless ventilating AND dehumidifying.Unless you know the garage actually has a damp atmosphere, you don't need to dehumidify it. Naked steel will sit in my garage for weeks without rusting, in winter, and that has no heater or anything else in it.
Had a storage shed/garage like this for 6 years now;
Fully Insulate and air seal as best you can, fit dehumidifier plumbed into drain and leave it on. The dehumidifier will take about £150/year to run but will also be like a 100W light bulb left on so it will produce a little heat. Not super fresh air but never stale.
Only issues are;
Newer Dehumidifers only work down 6C or so.. the older and industrial ones must use Re123a or something as they will run down to 0C.
Frost is an issue if not well insulated.. the dehumidifer is a reverse fridge so it tends to run cooler than the room on the chiller. These will freeze up at close to 1-2C but it keeps going.. so mine sit in a square plastic tub so that this then collects it.. and when the temperature next rises it will evapourate and be taken out by the dehumidifier. Some posh ones have built in heat cycle to beat this issue.. I also have one in my workshop to try an keep the rust at bay..
Anyway plain steel cleaned with grinder has only light rust on after 8 years storage like this..
You can get air heat exchange units for sealed houses.. cost £800 really and have about 85-90% efficency but you need one with a DC motor as the AC ones burn too much power.. I came out at about 12 year repayment on a 3.5 bedroom house and suspect it would have broken before that.. fine if you are new build but hard to justify on a retrofit basis. Guess they do small ones for bathrooms but I really would not worry.. add an adjustable low level vent if stale air is your worry.
Fully Insulate and air seal as best you can, fit dehumidifier plumbed into drain and leave it on. The dehumidifier will take about £150/year to run but will also be like a 100W light bulb left on so it will produce a little heat. Not super fresh air but never stale.
Only issues are;
Newer Dehumidifers only work down 6C or so.. the older and industrial ones must use Re123a or something as they will run down to 0C.
Frost is an issue if not well insulated.. the dehumidifer is a reverse fridge so it tends to run cooler than the room on the chiller. These will freeze up at close to 1-2C but it keeps going.. so mine sit in a square plastic tub so that this then collects it.. and when the temperature next rises it will evapourate and be taken out by the dehumidifier. Some posh ones have built in heat cycle to beat this issue.. I also have one in my workshop to try an keep the rust at bay..
Anyway plain steel cleaned with grinder has only light rust on after 8 years storage like this..
You can get air heat exchange units for sealed houses.. cost £800 really and have about 85-90% efficency but you need one with a DC motor as the AC ones burn too much power.. I came out at about 12 year repayment on a 3.5 bedroom house and suspect it would have broken before that.. fine if you are new build but hard to justify on a retrofit basis. Guess they do small ones for bathrooms but I really would not worry.. add an adjustable low level vent if stale air is your worry.
Try these guys - http://www.aircon247.com/p/405095/prem-i-air-xdry-... . The one I've shown there will work in low temps, I've had a couple of units off them and had very good service - ask for Rob.
As others have already intimated, ventilation and dehumidifiers are mutually exclusive. You go one way or the other. Both, however, are better (cheaper) than just heating the air.
If you go the dehumidifier route, you should also look to:
If not, do look at a Carcoon. A good tip is to find a sailing friend (dinghy sailing is fine) to rig up an arrangement of runners, pulleys and ropes, so you can quickly remove the cover and stash it against the wall. Otherwise, look at high air circulation. If it's a marginal problem a bathroom fan with a humidistat might just do the business.
If you go the dehumidifier route, you should also look to:
- Seal the environment, so you keep the dry(er) air in the garage
- Avoid wasting all that good air by regularly opening and closing doors. If you regularly have to open the door (or perhaps the kitchen door to go to the freezer) a dehumidifer is probably not for you.
- Insulate: Dehumidifiers produce a bit of heat, and as explained the warmer air holds a bit more moisture (reducing condensation). So as well as draughtproofing, consider the roof, and perhaps plasterboarding the walls (not a bad idea as you progress to an "ultimate garage"), and maybe some old carpet?
- Minimise the volume of air to be dried. The ultimate is a tent arrangement like the Carcoon (although that uses a different principle, and of course reduces usability), but perhaps you could turn the pitched roof area into a loft. The smaller volume means not only less energy used, but the effect is much faster - very handy if the car goes out for a run in the rain (a Carcoon can clear rainwater in minutes, preventing corrosion getting almost any hold).
If not, do look at a Carcoon. A good tip is to find a sailing friend (dinghy sailing is fine) to rig up an arrangement of runners, pulleys and ropes, so you can quickly remove the cover and stash it against the wall. Otherwise, look at high air circulation. If it's a marginal problem a bathroom fan with a humidistat might just do the business.
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