Need to maintain high rH (90%) in basement closet
#1
06-06-04, 05:48 PM
Need to maintain high rH (90%) in basement closet
I am turning a small closet, roughly 4'wide x 8' long x 6' high into a small scale oyster mushroom farm. I will be exchanging the air inside the closet 5 times an hour. A 15 cfm fan will do this, and it will be kept positively pressurized. I also need to maintain 90%rH inside the closet. At one point this closet leaked water, but it was sealed on a single side with Drylok and the leak stop. I finished sealing the walls with the dry lok. I need to install a vapor barrier now. I know that the outside wall will experience temperature variation and thus condensation at high humidities. So I will leave an air plenum between the vapor barrier and the outside concrete wall. But, should I leave an air plenum between the inside concrete walls and the vapor barrier? If so, how much?
#2
06-06-04, 08:14 PM
Super Moderator
MushroomGrower,
The space between the wall and vapor barrier should be insulated, preferrably with moisture resistant styrofoam.
You will also have to install a vapor barrier completely surrounding this room because at 90% rh with the rest of the house at say 30%, you will have a tough time keeping the moisture in.
If you are going to positively pressurize this room you may not be able to do it with a simple fan unless you are talking about a small commercial one.
Also, I'm curious as to what you will humidify the room with.
You are going to have to pump a lot of moisture in there with that air change.
Interesting project you have as I maintain a museum hvac system. In a sub zero climate we keep the interior at 50% rh and a perimeter air system at 25 % and it's a constant battle.
The space between the wall and vapor barrier should be insulated, preferrably with moisture resistant styrofoam.
You will also have to install a vapor barrier completely surrounding this room because at 90% rh with the rest of the house at say 30%, you will have a tough time keeping the moisture in.
If you are going to positively pressurize this room you may not be able to do it with a simple fan unless you are talking about a small commercial one.
Also, I'm curious as to what you will humidify the room with.
You are going to have to pump a lot of moisture in there with that air change.
Interesting project you have as I maintain a museum hvac system. In a sub zero climate we keep the interior at 50% rh and a perimeter air system at 25 % and it's a constant battle.
#3
06-06-04, 09:38 PM
In Wisconsin on the lake, the average rH in June is around 60%-70%, in winter it is around 25%. I don't think I'll need to put much moisture in the air to get up to 90%
I was going to start with 6mil visqueen on the floor, but covering up a foot of the walls. I will try to get all four walls out of one piece of visqueen, overlapping the floor by a foot. The floor/wall overlap will be sealed with silicon. I will do the cieling the same way. I'd like to make the door airtight, but I don't think I can. There aren't any windows in the room that open, so exhaust may just be through the door by positive pressure. Its not my favorite option to exhaust into the basement whole but, getting the exhaust outside is a bit complicated.
I am going to start with a small ultrasonic humidifier, I actually expect it to be powerful enough. Stick a PVC into the humid air exhaust of the humidifer And a foot above the hummer a small PC fan will recapture room air and push the humid fog up into a mixing box on the cieling. The intake fan pushes air into the mixing box and then is distributed in a PVC network on the cieling. It creates a descending fog. If I have to fill the humidifier take too often, then I will convert to a garden fogger inside of a 5 gallon bucket.
I may be renting out more space soon, depending on the success of this little project. I went to Home Depot today and spent some time staring at those Honeywell Whole House humidifiers. I wonder if those could keep an area 10' x 20' at 90%rH. Since they hook up to a water supply it would be almost be turnkey.
I was going to start with 6mil visqueen on the floor, but covering up a foot of the walls. I will try to get all four walls out of one piece of visqueen, overlapping the floor by a foot. The floor/wall overlap will be sealed with silicon. I will do the cieling the same way. I'd like to make the door airtight, but I don't think I can. There aren't any windows in the room that open, so exhaust may just be through the door by positive pressure. Its not my favorite option to exhaust into the basement whole but, getting the exhaust outside is a bit complicated.
I am going to start with a small ultrasonic humidifier, I actually expect it to be powerful enough. Stick a PVC into the humid air exhaust of the humidifer And a foot above the hummer a small PC fan will recapture room air and push the humid fog up into a mixing box on the cieling. The intake fan pushes air into the mixing box and then is distributed in a PVC network on the cieling. It creates a descending fog. If I have to fill the humidifier take too often, then I will convert to a garden fogger inside of a 5 gallon bucket.
I may be renting out more space soon, depending on the success of this little project. I went to Home Depot today and spent some time staring at those Honeywell Whole House humidifiers. I wonder if those could keep an area 10' x 20' at 90%rH. Since they hook up to a water supply it would be almost be turnkey.
#4
06-07-04, 05:42 AM
Super Moderator
You may have to recalculate your humidity needs.
MushroomGrower,
If you have the air change you will require to grow mushrooms, your humidity needs will be greater than you expect.
You must understand that relative humidity is only that, relative.
It is the amount of moisture, as a percentage that the air can hold at a given temperature.
So, at 0 degF in the winter the amount the air will hold in grains/gal is WAY less than at 70 degF in the summer.
This means that in the winter time you will have to pump in a lot more moisture than a home humidifier can deliver.
Unless you want to trash the house, if you vent 15 cfm of 90%rh air into your home in the winter you will create a pool of water under your windows, no matter how good they are.
Here is a calculator you can download to see how much moisture is in the air at a given temp.
You can enter the dry bulb or normal temp and put in a humidity percentage and it will give you the actual amount of moisture in the air.
I have tried ver 1.3.3, it works good and comes with an uninstaller.
http://www.parkssoft.com/ezair.html
If you have the air change you will require to grow mushrooms, your humidity needs will be greater than you expect.
You must understand that relative humidity is only that, relative.
It is the amount of moisture, as a percentage that the air can hold at a given temperature.
So, at 0 degF in the winter the amount the air will hold in grains/gal is WAY less than at 70 degF in the summer.
This means that in the winter time you will have to pump in a lot more moisture than a home humidifier can deliver.
Unless you want to trash the house, if you vent 15 cfm of 90%rh air into your home in the winter you will create a pool of water under your windows, no matter how good they are.
Here is a calculator you can download to see how much moisture is in the air at a given temp.
You can enter the dry bulb or normal temp and put in a humidity percentage and it will give you the actual amount of moisture in the air.
I have tried ver 1.3.3, it works good and comes with an uninstaller.
http://www.parkssoft.com/ezair.html
#5
06-08-04, 01:57 PM
Dont know if it it would work for you there . But working with drying rooms for big clay pots. Would have to start off at about 95%rH. We would just use oil burner nozzle on a water line. Might look into some of the good humidifiers that they have to go on a furnace. That put out the water. .
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