Keeping condensation out of concrete garage
Discussion
Not so much keeping it out as in there is a water getting in, but if I wanted to keep the relative humidity just high enough to stop water condensing onto objects is there a reasonably priced way of doing this? The garage is a concrete sectional garage, uninsulated, with small air gaps around the door. It's fairly new (5 years ish), so is as good as one of those is going to get. In previous year's I've used a dehumidifier which does work, but is fairly expensive to run and struggles in the cold weather we are having now. I was thinking of putting a heater in, but would it cost a lot to keep the RH low enough so it doesn't condense?
Any suggestions helpful. In temperatures above 7 or 8 degrees the dehumidifier pulls out a lot of water, but a heater maybe better for days like this?
Any suggestions helpful. In temperatures above 7 or 8 degrees the dehumidifier pulls out a lot of water, but a heater maybe better for days like this?
What type of dehumidifier did you use? It really needs to be desiccant one
I use a Meaco DD8L (on recommendation from other PHers), with a direct output into a sink for my high-roof 8.5m x 6m garage with roller-doors. No condensation ever even in the coldest of our weather, and I don’t even run it in the highest setting
I use a Meaco DD8L (on recommendation from other PHers), with a direct output into a sink for my high-roof 8.5m x 6m garage with roller-doors. No condensation ever even in the coldest of our weather, and I don’t even run it in the highest setting
paulwirral said:
Vent it from front to rear
This... I used to use a humidifier but got fed up with having to keep emptying the tank and it was expensive to run 24/7. I thought I would give better ventilation a go so put some soffit vents in the front and back (2 vents each) and put a small fan on a timer at the back to run 12 hours a day at 6 hour intervals (6 on and 6 off), this has worked very well over the last three years and no longer get any condensation also very little cost to run.Either seal it up, insulate the roof and put in a desiccant dehumidifier with an external drain.
OR
Put vents in one end with an extractor fan in the other and keep the air moving.
I've tried both and option 1 works best for me but it is more costly.
The other thing I found useful was to replace metal shelves with plastic ones and get rid of anything which traps the damp which you are hanging onto "just in case it might be handy" like loads of dust sheets, carpet offcuts and so on.
OR
Put vents in one end with an extractor fan in the other and keep the air moving.
I've tried both and option 1 works best for me but it is more costly.
The other thing I found useful was to replace metal shelves with plastic ones and get rid of anything which traps the damp which you are hanging onto "just in case it might be handy" like loads of dust sheets, carpet offcuts and so on.
On mine I set out to stop the damp getting in there in the first place. I used DPM sheet on the walls under a wood frame made from 2 X 2 timber, in between the battens I have kingspan insulation. on the roof I have the same insulation with a breathable roof membrane behind it. Leftover insulation was wedged/attached to the door
I run a Meaco DD8L (mentioned above) 24/7 on the lowest setting
Only time I sometimes get condensation is in the summer when humid air enters the open door and settles on the cool floor
Not sure whether my method was the correct way of doing things (was kind of done in a rush / limited budget at the time) been up 10+ years now and I can confidently store my tools and more importantly my Escort in there
I run a Meaco DD8L (mentioned above) 24/7 on the lowest setting
Only time I sometimes get condensation is in the summer when humid air enters the open door and settles on the cool floor
Not sure whether my method was the correct way of doing things (was kind of done in a rush / limited budget at the time) been up 10+ years now and I can confidently store my tools and more importantly my Escort in there
WyrleyD said:
paulwirral said:
Vent it from front to rear
This... I used to use a humidifier but got fed up with having to keep emptying the tank and it was expensive to run 24/7. I thought I would give better ventilation a go so put some soffit vents in the front and back (2 vents each) and put a small fan on a timer at the back to run 12 hours a day at 6 hour intervals (6 on and 6 off), this has worked very well over the last three years and no longer get any condensation also very little cost to run.Chumley.mouse said:
This, Ventilate it with lots of airflow so the temperature is the same inside and out and you will not get condensation. As said a small fan to keep the air moving when its still outside will help.
Surely this doesn't work, if you get air into the garage and it cools, even if everything else cools with it, you'll get condensation when the air falls below the dew point? Same reason why there is condensation on plants or grass outside when it's damp - there is no lack of ventilation, but simple physics! The only thing airflow can do is help the water evaporate once it warms up or dries out, but while it is saturated and below the dew point, ventilation can't prevent it happening in the first place.
Edited by Condi on Wednesday 7th January 11:45
Vent it. Condensation is caused when warm air cools. Warm air has a greater capacity to hold moisture; when it cools and the moisture content in the air exceeds the capacity when cooled, it condenses. If the airflow is good, the outside and inside air will be in equilibrium, so there will be no colder surfaces for condensation to form on.
Certain dehumidifiers (refrigeration type) do not work well in low temperatures. Heating will stop condensation, but unless it is built tight with good insulation (which a concrete sectional garage isn't), this will be expensive.
Certain dehumidifiers (refrigeration type) do not work well in low temperatures. Heating will stop condensation, but unless it is built tight with good insulation (which a concrete sectional garage isn't), this will be expensive.
Condi said:
Surely this doesn't work, if you get air into the garage and it cools, even if everything else cools with it, you'll get condensation when the air falls below the dew point? Same reason why there is condensation on plants or grass outside when it's damp - there is no lack of ventilation, but simple physics!
The only thing airflow can do is help the water evaporate once it warms up or dries out, but while it is saturated and below the dew point, ventilation can't prevent it happening in the first place.
Dew forms outside because the mass of ground remains cold, and the air hitting it has now been warmed.The only thing airflow can do is help the water evaporate once it warms up or dries out, but while it is saturated and below the dew point, ventilation can't prevent it happening in the first place.
Edited by Condi on Wednesday 7th January 11:45
Lofts and other building cavities are ventilated to stop condensation.
Ganglandboss said:
Lofts and other building cavities are ventilated to stop condensation.
The outside world has perfect ventilation, yet condensation can still form on almost anything, including cars and windows. In other words ventilation alone inside a garage will not stop condensation forming on cold surfaces.It's not so simple!
I have a lean-to which is more ventilated than a breezy thing, I get vast amounts of condensation on anything metal in there, and on the underside of the roof, when certain weather conditions are met.
That is typically when the shack has cooled overnight and warmer damp air blows in.
I also have a metal shed which I've controlled the condensation in by insulating the roof and damp proofing the floor. There is still some condensation at times, but it forms on the metal door and drips outside the shed and not on my valuable junk.
Some places the local weather conditions are against you, a dehumidifer is good most of the time, but when it's too cold, heating is a good answer.
Just keeping the shed a few degrees above outdoors tips the balance. Insulation helps a lot.
I'm also involved with boats where these problems are much debated.
One thing i've learned from that is to have zero tolerance of rain leaks or any other water ingress.
Also frequently visiting and removing any water and cleaning any dirt or mould helps.
Open it up whenever you get a dry day. That helps lose moisture from wood and other materials.
A mate has a load of stuff in a container, he's getting by with those chemical moisture absorbers which can be got for a pound or so each in quantity on ebay or amazon.
HTH.
I have a lean-to which is more ventilated than a breezy thing, I get vast amounts of condensation on anything metal in there, and on the underside of the roof, when certain weather conditions are met.
That is typically when the shack has cooled overnight and warmer damp air blows in.
I also have a metal shed which I've controlled the condensation in by insulating the roof and damp proofing the floor. There is still some condensation at times, but it forms on the metal door and drips outside the shed and not on my valuable junk.
Some places the local weather conditions are against you, a dehumidifer is good most of the time, but when it's too cold, heating is a good answer.
Just keeping the shed a few degrees above outdoors tips the balance. Insulation helps a lot.
I'm also involved with boats where these problems are much debated.
One thing i've learned from that is to have zero tolerance of rain leaks or any other water ingress.
Also frequently visiting and removing any water and cleaning any dirt or mould helps.
Open it up whenever you get a dry day. That helps lose moisture from wood and other materials.
A mate has a load of stuff in a container, he's getting by with those chemical moisture absorbers which can be got for a pound or so each in quantity on ebay or amazon.
HTH.
RicksAlfas said:
insulate the roof
This is critical whether you seal the building up or make sure that it's well ventilated. Concrete garages usually have a corrugated cement (with or without asbestos) roof or a corrugated sheet steel roof; both of these options tend to have condensation forming on the inside. Insulate the roof to prevent this and then either seal the garage and run a dehumidifer or make sure that it has good ventilation; I choose the latter and it has always worked fine in a number of garages but some swear by a dehumidifier.Ganglandboss said:
Vent it. Condensation is caused when warm air cools. Warm air has a greater capacity to hold moisture; when it cools and the moisture content in the air exceeds the capacity when cooled, it condenses. If the airflow is good, the outside and inside air will be in equilibrium, so there will be no colder surfaces for condensation to form on.
I'm just pondering this: I'm not sure that it's about keeping the inside and outside 'at equilibrium', but ensuring that the temperature of the surfaces inside doesn't drop below the dew point of the air. Options are:i) heat everything: in particular, this ensures that the air temperature never falls below its own dew point - ridiculously expensive and if the building isn't sealed, you'll have a never-ending supply of cold air to heat
ii) reduce the moisture in the air (i.e., dehumidifier) - this lowers the dew point
iii) change the air (ventilation) - I think this works because if the outside temperature is falling, then (by conduction/radiation through poorly insulated walls/ceiling) the temperature of all the surfaces inside will fall. If you have the same air hanging around while this happens, then there is nothing to stop the temperature of surfaces falling below the dew point of the air. However, if you replace that air with fresh cold air from outside (which is likely to be colder than your inside surfaces) and which, by definition will be above its own dew point (unless it is actually fog!), then you can maintain a margin between the surface temperatures and the dew point of the air you're bringing in.
This all works (and is the principle of the German fresh-air-open-windows-temporarily thing) because air has a relatively low heat capacity (compared with all the solid objects inside), so bringing in the cold air itself doesn't have a significant effect on the temperature of everything else inside.
In the other direction (when things are warming up) you can get condensation because air you're bringing in is warmer than the internal air + surfaces, and the surfaces are below the dew point of the new warm air. But this should be temporary because (unless the outside air is very humid) as everything warms up, there is plenty of 'capacity' in the warm air to hold more moisture, so the condensation will evaporate.
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