Exhausting to outside in a basement.. ?

[BigGreenThumb]

If you had a 400cfm exhaust inside of a built closet in a basement exhausting directly outside the house and had a passive intake, could draft from the chimney be pulled and cause the gas boiler spill switch to trip or even worse potentially pull CO into the basement through a backdraft? I may be overthinking here but seems like this could cause a neg pressure in the entire house but I don’t know how much air is enough to cause this.

 

[DailyBlastin]

Hmm i havent run into too many basements with fireplaces so the chimney question is interesting, honestly itll probably be a good thing because youll have fresher air with better c02 quality than you would without the chimney in there... In order to assess the situation better we would need to know the volume of your built closet. I have zero knowledge of how a gas boiler spill switch functions but i cant imagine that moving air would cause any kind of major issues.. i mean fromt he information provided it sounds like the situation is essentially the same as if you opened a window.. air would be passively pulling in due to the fan exhausting the entire room, does the spill switch get tripped when you have a window open? The true effect of negative pressure will be strongest first in the closet, secondly in the room where the closet it, beyond that a 400cfm fan is not strong enough to create the effect in the rest of your house.

 

[DaFreak]

I've been doing it for 4 years now and have had no problem but my chimney vent is covered.

 

[DailyBlastin]

I've been doing it for 4 years now and have had no problem but my chimney vent is covered.

explain further?

 

[DaFreak]

explain further?

I’m not dead

 

[BigGreenThumb]

Hmm i havent run into too many basements with fireplaces so the chimney question is interesting, honestly itll probably be a good thing because youll have fresher air with better c02 quality than you would without the chimney in there... In order to assess the situation better we would need to know the volume of your built closet. I have zero knowledge of how a gas boiler spill switch functions but i cant imagine that moving air would cause any kind of major issues.. i mean fromt he information provided it sounds like the situation is essentially the same as if you opened a window.. air would be passively pulling in due to the fan exhausting the entire room, does the spill switch get tripped when you have a window open? The true effect of negative pressure will be strongest first in the closet, secondly in the room where the closet it, beyond that a 400cfm fan is not strong enough to create the effect in the rest of your house.

No fireplace.. here’s a rough sketch of the layout. Total cubic feet of the area is about 2900 where the room I’ll build inside of there is just around 160-170. I don’t think it’ll be an issue but I like to think everything out before I make moves and start cutting holes and whatnot..

 

[BigGreenThumb]

I’m not dead

Lmao I think what’s he means is the way you’ve explained it so far makes it seem like just simply a chimney cap would prevent this from happening... a chimney cap simple keeps moisture and animals out and has nothing really to do with draft unless it is motorized, especially if you have a negative pressure situation

 

[DaFreak]

House was built in the 60s and there used to be a wood stove in the basement using the same chimney as the boiler. Now the stove is gone and there is a metal cap on it. Doesn't seem air-tight to me and you can see space between it. Like I said, 3 years and I never had a problem. I never even thought about it till this thread but I would assume that is just a lot easier pulling air from the rest of the basement and down through the stairwell.

 

[BigGreenThumb]

The other thing I was (over)thinking was when you exhaust outside, does it condensate like a dryer exhaust would in the cold winter months?

My plan is to blow the exhaust out under a small overhang that is open on 3 sides that I will enclose with lattice.. but would the warm air blowing out here cause any issues with moisture building up underneath or should there be good enough air movement with it being pretty much open on all 3 sides? Made a sketch for reference..

 

[thumper60]

The other thing I was (over)thinking was when you exhaust outside, does it condensate like a dryer exhaust would in the cold winter months?

My plan is to blow the exhaust out under a small overhang that is open on 3 sides that I will enclose with lattice.. but would the warm air blowing out here cause any issues with moisture building up underneath or should there be good enough air movement with it being pretty much open on all 3 sides? Made a sketch for reference..

its the same as a dryer vent. if it gets below freezing it will blow a cloud of steam that will freeze on contact,i get ice buildup on my hood.

 

[BigGreenThumb]

Hmmm... now I’m wondering if I should figure out another way

 

[DaFreak]

You should have no problem. Been doing it for years and the cold never comes back down the line with a positive air-flow going out. Gets in the negative digits where I live

 

[BigGreenThumb]

I’m more concerned that there will be a giant steam cloud constantly blowing out from under my house, might look a little odd. Neighbors may just think I have the cleanest laundry on the block! ‍

 

[natureboygrower]

I think you'll be fine. I dont seem to have a problem with that either. My cab is small but it's a very small run of dryer vent to the outside. Rn its below 20° f and I see no exhaust.
Edit
I have radiant heat which really dries out my grow. Im rarely running above 50% rh in the winter. Thump might be running at a higher rh

 

[DaFreak]

I’m more concerned that there will be a giant steam cloud constantly blowing out from under my house, might look a little odd. Neighbors may just think I have the cleanest laundry on the block! ‍

Doesn't happen. The air from the garden is not like the air from a hot shower. I have never even seen steam from my dryer in the winter to be honest.

 

[thumper60]

Doesn't happen. The air from the garden is not like the air from a hot shower. I have never even seen steam from my dryer in the winter to be honest.

I don't under stand that when its below 10-15 degree i have a cloud of steam coming out of my hood just like my dryer vent. what do you see for low temps?any thing under 20 iam blowing clouds

 

[thumper60]

I’m more concerned that there will be a giant steam cloud constantly blowing out from under my house, might look a little odd. Neighbors may just think I have the cleanest laundry on the block! ‍

how cold does it get there i deal with below freezing for months at a time.

 

[DaFreak]

Same, I have no idea how you could see steam coming from the vent. Anytime a door is opened in winter do you see a cloud of steam coming out?

We see -20s but most of the winter is around 0.

 

[thumper60]

I think you'll be fine. I dont seem to have a problem with that either. My cab is small but it's a very small run of dryer vent to the outside. Rn its below 20° f and I see no exhaust.
Edit
I have radiant heat which really dries out my grow. Im rarely running above 50% rh in the winter. Thump might be running at a higher rh

i run 45-50 rh but iam venting 4 1k hps room runs around 80 in a out building.was putting out lots of steam early this morning but now its almost 20 and no steam.

 

[thumper60]

Same, I have no idea how you could see steam coming from the vent. Anytime a door is opened in winter do you see a cloud of steam coming out?

We see -20s but most of the winter is around 0.

oh ya, hell i steam when it gets real cold.