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Root Cellar Vent?

Posted by konrad___far_north 3 (My Page) on
Sun, Aug 8, 10 at 13:37

I'm building a small 8x10x8 foot high root-cellar into a hill, the floor
will be about level to the lower elevation so it can't build up with
water. The door will be in middle front of 10'....kind of a walk out basement.
The idea of how to run fresh air into the cellar is what I have to decide soon.
I'm making forms for concrete walls and want to run two holes through
the walls. It seems most air intake...from what I have been reading
is coming in from front, I have the idea of running pipe from the front to
the side and back of both side, initially fresh air coming in from the back/side's....2- 4"diameter pipe. This would allow several feet of under ground air travel, thus making the air somewhat cooler in summer and warmer in winter....having the pipe slightly uphill, so the air coming in is about 6" off the floor. The exhaust air, one only?.. about 4" diameter in middle of cellar. I haven't checked for pipe material yet, hope something like what they use for homes...toilet vent pipe?
Would this work?.. Any help is appreciated.

Follow-Up Postings:

RE: Root Cellar Vent?

I think I have seen discussions of venting root cellars in the Greenhouses & Garden Structures forum. I'd try there if you don't get a lot of response here.

RE: Root Cellar Vent?

Thank you lipother
Over-there the I can't find anything..and now perhaps this post gets

RE: Root Cellar Vent?

I think you would be better off with the traditional intake low in the front and exhaust high in the back.

I don't think you will get the cooling gains you are hoping for and you run the risk of unseen molds growing in the longer cool damp pipe runs.

The air may be cooled as it runs through the pipe but the surrounding soil/concrete will be warmed by an equal amount. So you lose some of the cooling by the walls as they have been warmed by the heat exchange from the pipe so there is little or no net gain.

If you want more stable temperatures I would go a little deeper. If water is an issue I would put in a drain pipe from a low towards the front floor under the footing and out down the slope.


RE: Root Cellar Vent?

No problem. Also, you could try the Vegetable Gardening forum.

RE: Root Cellar Vent?

Thank you zeuspaul!
Yes, your'e right...also, if something happens to the pipe down the road
it would be a tough fix. I can't go deeper because the floor is already
level with lower ground, the cellar will be insulated...I would think above
frost level only, about 4 feet deep. Dirt on top will be about 4 to six feet.
Will two intake, 4" diam. and one exhaust be OK.?


RE: Root Cellar Vent?

I would think one 3 inch inlet and one 3 inch outlet would be enough. Four inch is more than adequate. Why two inlets? If they are placed on opposite corners on the front side you will get more even air flow.

Four feet of dirt on the roof? That is a lot of weight! What is the roof made of??

I am building something similar but it will double as a fire shelter. Mine is 6.5 wide x 10.5 deep and about 7 ft high. I am digging mine deeper than grade in the front and then digging out the slope to the level of the floor or slightly higher and installing a drain.


RE: Root Cellar Vent?

I was reading intake should be double size then exhaust....I don't know
When you say one 3 inch is adequate...but then when you say placed
on opposite corners? can you when you have only one?

>>Four feet of dirt on the roof? That is a lot of weight! What is the roof made of?? <<

It is concrete

You must me living in a tinder dry climate that a shelter is needed.
Looks like you're going to be busy too!

RE: Root Cellar Vent?

While you're at it, you might consider adding in an exhaust fan, one of those just-in-case thoughts were somewhere down the road you might need to circulate the air more quickly.

RE: Root Cellar Vent?

When you say one 3 inch is adequate...but then when you say placed on opposite corners? can you when you have only one?

I was speculating on why you wanted two intakes.

I don't know much about rooet cellar ventilation. I was thinking in terms of oxygen and survival. It seems root cellar ventilation can involve several issues such as humidity control, temp control and ethylene evacuation.

I would guess the 4 inch vents would better cover your bases with an option to constrict the flow if necessary or fan assist as previously mentioned.

I still don't understand why the intake needs to be larger. In the case of a fan assist exhaust larger intakes would make sense.

I hope you are using a LOT of properly spaced rebar in the concrete roof. That's a major load and the roof has to be designed as a beam. Standard floor slab designs won't work. Or are you using an arch??

You must me living in a tinder dry climate that a shelter is needed

Most of the time it is beautiful here. However we have experienced a couple of major fire storms in the last decade. When the winds shift and come off the desert the consequences to dry brush can be rather dramatic.. First I built a water resevoir with a fire pump, hydrants and external water spray system which took me about two years. Now the shelter/root cellar or perhaps shelter/wine cellar:)


RE: Root Cellar Vent?

David, good idea, can't have a fan because I have no power.
Yes, I would think two pipe is better...just encase.
The roof has 6 angled ribs inside for support ...picture later, that's why
I make it higher inside...close to 9 feet, this way I don't bump into the
support beams very easily. This year it was the wrong year to do this project, have more rain this summer then we had the last 10 years. I have to keep bailing out water...even with a tarp over it I can't keep the water out.
Not sure...should I go with a heavy steel pipe for vent, [have some free on hand]... instead plastic, I think it will last almost for ever...plastic will deteriorate over time. I know, steel and cold temperature don't work together very well.....your thoughts please.


RE: Root Cellar Vent?

PVC has a long useful life if it is not exposed to sunlight. Depending on how it is used it may outlast steel.

I am not familiar with problems with steel and cold.

I would be inclined to go with steel out the roof with a rain cap and a screen.

The intakes may have more issues. Steel sounds good because it is free and you could always run 3 inch PVC through it later if the steel didn't work out. Three inch PVC elec conduit is UV protected and is cheap.

I would think you would want to control access to rodents and insects through the vents. Also some way to control the air flow.

I am going to use a two inch iron pipe out the roof with a pair of nineties to keep out the rain. For the intake I am going to use an adjustable air vent/louver low in the door (rectangular air conditioning or heating duct vent).

Just a thought. If you had two or three two inch threaded pipes out the roof you could thread a cap on one or two to increase or decrease air flow.

You might consider a spare electric conduit through the concrete for possible future small solar panel which could run a 5 or 10 watt ventilation fan.


RE: Root Cellar Vent?

Thank you Zeuspaul...some good hints!
I'm afraid that steel pipe intake could plug up with ice sooner then
plastic in the winter? You're right...I could run something else through.

Your nineties sounds good, perhaps not as efficient as straight out
but I'm sure it will work. I was thinking for battery rechargeable down
the road for light or small van, I was thinking to feed wire through the
roof vent...just small wires, could run through the bug netting.

I would think the amount of air flow you can achieve by a adjustable intake should be sufficient, your duct flow vent might work good, or build some kind of a wooden box with horizontal slide/wood with a hole in it and secure position with a pin or whatever so it stay's secure.

You can also restrict the flow on the exhaust from the inside of cellar
by shoving something inside the pipe.

RE: Root Cellar Vent?

I'm reading your thread with jealous interest.
One suggestion -- I remember that the Nebraska root cellars/tornado shelters of my youth had a vaned thing on the end of the outlet tube, When the wind blew it would turn the vaned ball and pull air up out of the cellar. I've seen larger, but similar things on roofs to help ventilate the attics. I'm sure the smaller ones still exist, perhaps at a farm store.

RE: Root Cellar Vent?

Thank you!.. and for stepping in!

That's a very good point...I see them around here on roofs too, to get out the hot air fast from the attic, helpes
cooling the house.
I'm wondering....can you actually have too much ventilation in a little root cellar?
We definitely don't need this when we have snow and ice.
In summer I'm thinking of pulling too much warm and dry air in,...we are usually very dry all year round. I will have a hard time
bringing the humidity up without a fan.

RE: Root Cellar Vent?

There seem to be a whole bunch of 'solar powered ventilation fan' out there - try a google on the word string.

RE: Root Cellar Vent?

Thank you David!
Here is a link to the build, I'm not done yet, ..hopefully next year, the extension [walk in] will be the worst part.

Here is a link that might be useful: Build a root cellar into the side of a hill

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