Exhausting to a ridge vent / soffit Attic

[Cannabis Critic]

I need to remove water vapor. I'm using a humidistat to control an inline fan. I want to pull humid air into attic space. If fan is in the attic, should I exhaust directly into a large attic that has a ridge vent or run 8in. flex duct to a soffit?

 

[Switcher56]

Exhausting hot humid air into an attic is not advisable, unless it is via a proper fitted vent and piping (flex hosing etc...)

 

[flylowgethigh]

^^ What he said. There is a lot of water being exhausted, and it will invite mold. I added an 8" hooded exterior wall fan up high, and run the tent exhaust out through it.

 

[troutman]

That's the last place you want to send humidity. If the insulation gets damp it's useless.
As mentioned above, you can direct the air with a duct directly outside from there.

 

[Cannabis Critic]

Thank you for advice.

 

[Three Berries]

I exhaust into the attic. But I have plenty of ventilation usually with wind turbines. I did see the last time with a heavy frost on the roof where the heat from the exhaust melted the frost. I need to go up there when it's really cold to see what's going on. I am going to up from 4" to 6" next cycle and may add some ducting in the attic to bring the exhausted air closer to the wind turbine if any frost is building up in the attic. May just take some redirecting of the air flow or piece of ridged insulation under the roof where it hits.

 

[Cannabis Critic]

I exhaust into the attic. But I have plenty of ventilation usually with wind turbines. I did see the last time with a heavy frost on the roof where the heat from the exhaust melted the frost. I need to go up there when it's really cold to see what's going on. I am going to up from 4" to 6" next cycle and may add some ducting in the attic to bring the exhausted air closer to the wind turbine if any frost is building up in the attic. May just take some redirecting of the air flow or piece of ridged insulation under the roof where it hits.

Thank you. Remember to use insulated ducting.

 

[Ready4]

Zero problem with running 8in. flex duct to a ridge vent - you have soffit vents & ridge vent, providing correct attic ventilation.

 

[Cannabis Critic]

Zero problem with running 8in. flex duct to a ridge vent - you have soffit vents & ridge vent, providing correct attic ventilation.

Thank you Ready4. In my case you’re probably correct, but I have good ventilation. I suspect my biggest problem is over thinking this.

 

[Switcher56]

Thank you Ready4. In my case you’re probably correct, but I have good ventilation. I suspect my biggest problem is over thinking this.

The operative word here is exhausting, which is a "positive" pressure, whilst your ridge vent is passive. How much humidity is being discharged into the attic that the "passive" system can't process. All this BS about redirecting with Styrofoam etc... or insulating the roof around the vent, yadi, yada. It is your fiberglass pink that will not insulate as it should. That is why you have the "attic" ventilation you have. It was never designed to have hot humid air go in there. The amount of turbines, length of ridge vents, is all commensurate with the volume of air contained in said attic. Do what ever voodoo you want to do. It's your house! My bathroom exhaust fan, exhausts through the gable end. I had passive vents (and soffits) when I redid my roof, I replaced them with a ridge vent. When I bought the house, the bathroom fan was exhausting is the attic. Bldg inspection brought that up and, there was EVIDENCE, of the malpractice!

 

[Three Berries]

I had a white roof with three turbines for exhausting. This had two gable end and 6 soffit vents. Went to a new dark brown roof and put in a ridge vent, removed the turbines. Big mistake. The attic got so hot the resin in 60 year old pine beaded out and was dropping on the insulation. I had the ridge vent shingled over and put the three turbines back in.

I put up a temp sensor last summer just under one of the turbines, then got a big exhaust fan but set it up to blow in from one gable end, sealing it off so it only sucked outside air. Took all the screens out of the other passive intake vents and replaced with 1/4". Replacing the screens really helped the passive flow. The fan is on a Inkbird temp controller set at 104F on/100F off. I still will get up to 130F in the summer.

 

[Three Berries]

Last week I bumped up my exhaust stack to 6" from 4". It serves a dual purpose as a 4" constant house ventilation and the 6" tent exhaust running at low speeds in the winter. Prior to this I saw the frost melted off over a large area where the vent comes out. It's just a stub that exits at the insulation level.

Originally I planned on running a flex duct under the insulation and up to a turbine but this really cut down on the air flow.

So I got one of those reflective emergency blankets and stapled that to the rafters over the vent. It's nice a it's too wide for three rafters so it drops on the sides about 6" and makes a three sided duct. It runs from behind the vent up to near the ridge.

Today after getting a snow overnight there was no melting. Fan was blowing out 70F/60% air or so. It's going to get down to 0F later this week and I want to go up there and observe. I have not seen any issues with the way it was up there and have been venting to the attic for 8 or 9 years now. I live in Central Illinois so it gets quite cold.

But most of the duct from tent to attic is insulated with reflective bubble wrap. It was easy to do and really quieted down the fan. I use 6" round steel galvanized duct work. Intake is insulated too as this is in a closet of an unheated room but fed house air from the bathroom.

Pro tip, don't buy 30ga steel

 

[Three Berries]

Well we had some real cold. Got down below 0F and the wind was down under 10 mph so I went up there to look. Not good. Frost on everything on the underside of the roof. I have a 2 speed pusher fan that .I put in this summer to blow air into the attic. I used it on low speed to blow for two days and went back up. Much better but still some frost.

So the tent is up against an outside wall. Wouldn't take much to pop a hole and vent outside. Though the plume of constant condensation in the winter will look out of place. I could go stright up with what I have and through the roof, it's only another foot or so.

 

[f-e]

If you own the house, consider a soffit vent above the bathroom window. Many bathroom extract kits go via the loft to the soffit, so a vent over the bathroom window leaves nobody guessing what it is. Even the thermal image camera won't think it looks odd.

Duct in lofts can fill with water if not insulated. It then sags between beams and eventually starts to drip, if it doesn't fill so much the air can't get through.

I have had no issue with smaller grows venting into lofts. I have not tried with anything meaningful though. If I were to do so, I would get some galvo and start building an nft tube system up there, to purposely get some condensation in my tubes and drain it. A big dehumidifier. I suspect a single straight run would be very effective. A du-hu core is only an inch. A circulation fan would complete the package. No excess moisture or hot spots. Then you could go to town, insulating the roof, but only from the gutters to a height of 3 foot. Picture the thermal image. You have a loft conversion.

 

[Three Berries]

Ha no too much work. The flower tent is on the backside of the bathroom so if I poked outside the wall it would be right next to the bathroom. Really low pitch and 4 foot overhang on the soffit. So getting to there from above is near impossible. It would exit the wall about 7 foot off the ground.

Might have to turn the tent around though as the exhaust port is right next to the wall now, no room for the fan and plumbing.. Pretty sure that's possible with this tent as the zipper opens both sides.

This is the tent I got for the closet. 2'x4'x6'high

https://www.acinfinity.com/hydroponi...-48-x-24-x-72/

It would be nice to recover the heat going out.

 

[Three Berries]

I put in new furnace last summer. Down sized form an oil furnace to propane. The oil furnace stack is really too large for the gas furnace, and it needs repaired. It's a 6" ID triple wall chimney around 10" OD. So I'm thinking of putting in a new 4" smaller chimney for the gas furnace and using the 6" stack for a through the roof vent outlet.

For the time being though I have the attic fan on when under 35F. The deluxe version of this fan has a humidity control on it but most people disabled it. Don't think it would be much good as the humidity gets so high around here at night in the summer.

 

[Three Berries]

My flowering is done so thankfully I can turn off the humidification on the exhaust going through the flower tent. Though I still have some exhaust running for whole house ventilation going to the attic.

So I took the fan out and flipped it so it's vertical on the outside of the tent with a 90 on the end. This comes out right at a foot from the ceiling so going through the wall outside will be really easy and a short run. But I want to continue to exhaust to the attic in the non winter months.. Not hard to flip it either way.

It was a mess in the attic. With the really cold temps ( -18F was the coldest) and me adding water to the air really built up the ice. Turning on a fan up there bringing in outside air helped somewhat. But also dispersed the frost to all areas of the attic roof underside.

I put another 8" of insulation up there the last couple of weeks and had to make a retention pond out of a tarp to collect the ice melting. It looked like stalactites and stalagmites at one time.

So from personal experience don't do this in the winter.

 

[Cannabis Critic]

Thank you. Remember to use insulated ducting.

Three Berries…I am glad you caught the problem quickly without serious damages. I’ve seen how quickly ducts can fill with water.

If you use a piece of straight insulated duct that’s smooth on inside surface; would that be enough to use year round?

I would also calculate how much heat you are losing from your exhaust. Is it worth the trouble and expense to reclaim your exhaust heat? Good luck to you.

 

[Three Berries]

Three Berries…I am glad you caught the problem quickly without serious damages. I’ve seen how quickly ducts can fill with water.

If you use a piece of straight insulated duct that’s smooth on inside surface; would that be enough to use year round?

I would also calculate how much heat you are losing from your exhaust. Is it worth the trouble and expense to reclaim your exhaust heat? Good luck to you.

I thought about that and bought some duct but it's too far of a run. About 15 ft. I'm afraid it would lose all heat even if insulated. And getting the right slope would be difficult without rigid duct. Be talking about a hundred bucks or so. Difficult area to work in too. I thought too about going straight up with a chimney but not really wanting to cut a hole in the roof. And still have all that vertical pipe that more than likely will have some water condensing.

I really should time my grows better so I'm not needed to run flower at this time of the year.

 

[Cannabis Critic]

I really should time my grows better so I'm not needed to run flower at this time of the year.

I have the opposite problem; my summers are hot and humid. It’s hard to keep things cool/dry enough.