How should I install ventilation pipes?

Another question.

The ventilation for our basement cold room will be through the joist above the ceiling which will be insulated.

Won't the pipes get condensation from being exposed to the warmer air in the joist? Should I insulate the pipes too?


And where should the fresh air intake pipe and stale air one be?
I thought the stale, warm air outlet should be near the ceiling as the warm air rises to the top but I read that it should be near the floor because carbon dioxide from vegetables is heavier than air.

Which is right? Thank you.

Hi Julia,
I'm not an expert, but while we wait for them to show up :)... I'll throw out a few thoughts.

Yes to the insulating any pipes going from a cold space to a warm space. Condensation can become a real issue. Probably not so much to the room, but would be prime mold growth area.

One setup I saw had the two pipes coming out of the wall at the same height, but inside, one was only about a foot long near the top and the other had a pipe that came almost to the bottom. If you can get enough of a draft going, I don't think the carbon dioxide build up will be that big of a deal. It doesn't take much air movement to shift things around. Adding a small fan on a timer would also do the same thing.

Yes, insulate those pipes for sure.  I'd spray foam the gap where they pass through the rim joist and then insulate the pipes well into the root cellar.  Where my pipes are uninsulted in the root cellar, they build up an inch of ice/frost.

I suspect that if two pipes enter at the same height and one travels down to the floor, there won't be any draft or chimney effect to move the air.  The air in the vertical pipe is the same temp as the air in the cellar outside the pipe so neither wants to rise or sink.  I think.

Just to clarify, where do you mean this particular insulation will be?

The ventilation for our basement cold room will be through the joist above the ceiling which will be insulated.

Matt McSpadden wrote:Hi Julia,
I'm not an expert, but while we wait for them to show up :)... I'll throw out a few thoughts.

Yes to the insulating any pipes going from a cold space to a warm space. Condensation can become a real issue. Probably not so much to the room, but would be prime mold growth area.

One setup I saw had the two pipes coming out of the wall at the same height, but inside, one was only about a foot long near the top and the other had a pipe that came almost to the bottom. If you can get enough of a draft going, I don't think the carbon dioxide build up will be that big of a deal. It doesn't take much air movement to shift things around. Adding a small fan on a timer would also do the same thing.

Maybe I was thinking too much. I won't worry any carbon dioxide then. After reading what you said, things look less complicated. If I just have one pipe near the bottom and one near the ceiling, I guess the air movement will happen either way.
Thank you, Matt.

Mike Haasl wrote:Yes, insulate those pipes for sure.  I'd spray foam the gap where they pass through the rim joist and then insulate the pipes well into the root cellar.  Where my pipes are uninsulted in the root cellar, they build up an inch of ice/frost.

I suspect that if two pipes enter at the same height and one travels down to the floor, there won't be any draft or chimney effect to move the air.  The air in the vertical pipe is the same temp as the air in the cellar outside the pipe so neither wants to rise or sink.  I think.

Just to clarify, where do you mean this particular insulation will be?

The ventilation for our basement cold room will be through the joist above the ceiling which will be insulated.

Then should I make two separate holes for two pipes each?

I'm thinking of putting pipes in the corner of the cold room. It's NE side of the house. Is this what you asked?

Can you send a photo or a drawing?

Yes, I think you want two pipes, one that just comes into the top of the cellar, another that comes in and runs down to near the floor.  In a perfect world, they'd be in opposite corners of the room.

For the insulation question, where is the general insulation for the house  and basement wall going to be?  I kind of thought you meant it was in the ceiling of the basement which would be unusual for new construction.  Maybe you just meant the rim joist would be insulated?

Mike Haasl wrote:Yes, I think you want two pipes, one that just comes into the top of the cellar, another that comes in and runs down to near the floor.  In a perfect world, they'd be in opposite corners of the room.

For the insulation question, where is the general insulation for the house  and basement wall going to be?  I kind of thought you meant it was in the ceiling of the basement which would be unusual for new construction.  Maybe you just meant the rim joist would be insulated?

We'll be insulating the walls of the house but I read that the ceiling of a basement cold room should be insulated so I'm going to do that either with Styrofoam or spray foam. Not in the ceiling but on it.

Now I'm getting a clearer picture of the ventilation pipes. One in the NE corner to get cold air and one near the door to release warm air. Thank you!

John C Daley wrote:Can you send a photo or a drawing?

Here it is. Actually the cold room will be in the NE of the house not NW. I edited my previous postings accordingly.

I'm thinking of dividing this room into two, one less cold and the other colder.

Ok, cool, yes you should insulate everywhere the cold room meets the house.  Both walls and the ceiling.  If you subdivide it into two rooms, I'd insulate the cold room and not insulate the cool room.  Squash like it closer to 55 degrees and canned goods don't like the humidity of a true root cellar.  

Your builder might have opinions about putting a vapor barrier around the cold room.  Something to keep the humidity of the house from condensing on the colder surface of the cold room walls.

Mike Haasl wrote:Ok, cool, yes you should insulate everywhere the cold room meets the house.  Both walls and the ceiling.  If you subdivide it into two rooms, I'd insulate the cold room and not insulate the cool room.  Squash like it closer to 55 degrees and canned goods don't like the humidity of a true root cellar.  

Your builder might have opinions about putting a vapor barrier around the cold room.  Something to keep the humidity of the house from condensing on the colder surface of the cold room walls.

Yes, vapor barrier, too. Thank you. I could've forgotten to mention that to my builder. I talked to him today and he understood what I want.

Another question...

If I don't lay out 2 inch thick Styrofoam under the 3.5 inch thick concrete floor like the rest of the basement, then the cold room will have 5.5 inch thick concrete floor. Wouldn't it be too thick to make the cold room more humid and cold? Will the moisture and coldness travel through 5.5 inch thick concrete from the ground?
Should I suggest put down 2 inch thick gravel on the floor instead of insulation and pour concrete on the top of the gravel?

I'd say it depends on your soil.  In my area, builders put plastic under the basement floor to keep water from wicking up into the basement.  So insulation or not, it wouldn't get humid from the soil.

I'd probably just go with the cement and then add humidity to the room if you end up needing it.  Then the house is more "normal" for resale :)

Mike Haasl wrote:I'd say it depends on your soil.  In my area, builders put plastic under the basement floor to keep water from wicking up into the basement.  So insulation or not, it wouldn't get humid from the soil.

I'd probably just go with the cement and then add humidity to the room if you end up needing it.  Then the house is more "normal" for resale :)

Thank you for replying. I think the last part of my posting was confusing. I'll erase that. I wasn't serious about not having concrete floor in the cold room.
What I meant to say was I'm wondering if I should put 2 inch gravel instead of insulation and then pour concrete on the top.
If I don't do that, the concrete on the cold room floor will be 5.5 inch thick instead of 3.5.
I might be thinking too much when either of them is fine.

Two things...

First, if you edit your previous posts, it  makes the thread of the conversation get confusing for people who later read it and wonder what people are talking about

Secondly, you're probably right that the cement thickness doesn't really matter.

If it was a huge space the cost of the extra concrete would add up, but much difference either way on that size space. Let the builder do whichever he wants. There may be some detail with the way they do the vapor barrier and insulation that makes one way easier.  Which means less chances for mistakes. I have heard of guys who had the insulation come loose and FLOAT. That was a DISASTER.

Mike Haasl wrote:Two things...

First, if you edit your previous posts, it  makes the thread of the conversation get confusing for people who later read it and wonder what people are talking about

Secondly, you're probably right that the cement thickness doesn't really matter.

Got it. Thank you.

R Scott wrote:If it was a huge space the cost of the extra concrete would add up, but much difference either way on that size space. Let the builder do whichever he wants. There may be some detail with the way they do the vapor barrier and insulation that makes one way easier.  Which means less chances for mistakes. I have heard of guys who had the insulation come loose and FLOAT. That was a DISASTER.

Yes, 8x8 space wouldn't make much difference in terms of the cost of concrete but floating insulation sounds scary. Hopefully it doesn't happen to my house. I'll ask my builder about it. Thank you.