[Oscar]

The attic space above the garage is shared with the rest of the attic space in the rest of the house. The roof sufficiently separates the inside of the house from the attic space above it. It's not a new house, but it's not falling apart either. I understand your points, but IMO they are a worst-case/extreme scenarios. With so much venting around the attic to the outside, I assure you there is no pressurization occurring; ie: the pressure in the attic is no higher than normal atmospheric pressure. To achieve pressurization, one needs a restriction. Again, with so much venting out of the attic to the outside, there can't be any pressurization occuring. In one sentence you say the attic would be pressurized, and in another you say that if too much is sucked out [of the attic] air inside the house would try to get into the attic, which would mean that there would be less pressure in the attic compared to inside the house. Sorry, but I feel both scenarios are pretty far fetched as neither the attic nor the inside of the house are perfectly sealed entities. Again, both extreme scenarios that I feel don't apply in the real world. Thanks for your concern, but this setup has been running like this for a long time now. Dust still falls to the floor and not up towards the A/C vents, as I have to vacuum constantly, lol. Also, it's not like there is constant welding going in the garage.

[tweake]

to have air flow you must have air pressure. no pressure air doesn't move.
having lots of vents just means the pressure is lower.
however the big difference here is when talking houses the pressures are tiny. where talking 1000th of a psi.
but thats all it takes for air to flow through all cracks and gaps in the house. (0.007 psi is actually what they test houses with and thats quite brutal for a house.)

with any fan arrangement attic pressure will be different to inside house pressure, therefore you get air flow from one to another.

[TraditionalToolworks]

tweake,

I think you're off base here. Oscar is transferring some of the welding fumes out of the garage, and even if they're being transferred into the attic, who cares? Nobody is living in the attic of his house, and those fumes can't easily be transferred into his house, the least resistant path is out the vents on the roof.

Ideally it would probably be better if there was a 12" hose connected to the fan which was connected to a gable or roof to just push the exhaust out of the home entirely.

I suspect he would know if those fumes were getting into his house, it would be apparent when you go to another area inside the home.

I think you're making something out of nothing.

[Oscar]

tweake,

I think you're off base here. Oscar is transferring some of the welding fumes out of the garage, and even if they're being transferred into the attic, who cares? Nobody is living in the attic of his house, and those fumes can't easily be transferred into his house, the least resistant path is out the vents on the roof.

Ideally it would probably be better if there was a 12" hose connected to the fan which was connected to a gable or roof to just push the exhaust out of the home entirely.

I suspect he would know if those fumes were getting into his house, it would be apparent when you go to another area inside the home.

I think you're making something out of nothing.

Thank you, I see you get my point.

Tweake, I'm not sure what you're imagining but I assure you that what ever tiny tiny tiny tiny crevices there might be between the attic space and the inside of the house, perhaps around the A/C vents in the ceiling, they are not letting any welding fume particles through, as the whole ceiling (on the attic side) is completely covered in fiberglass insulation. Like TTW said, any and all airflow from my ventilation fan is getting out through the attic fan and 18 vents that are about 14" x 8" around the perimeter of the house on the underside of the soffit.

[tweake]

tweake,
those fumes can't easily be transferred into his house, the least resistant path is out the vents on the roof.

absolutely incorrect.
it does go through all those little gaps as well. the bulk of it will certain go out the fan and vents, but it will go out every exit there is. its not going to ignore the holes in the ceiling and only go out the vents.
thats the main point just trying to get across. just because its plaster ceiling etc does not make it air tight. blowing air into a ceiling does pressurise it enough to blow air into the house (and vice vers with a attic fan)
the saving grace is the insulation which is acting as a filter, and you see the results of that in many homes.

as you say the solution is a hose and vent so it vents directly outside.

[TraditionalToolworks]

absolutely incorrect.
it does go through all those little gaps as well. the bulk of it will certain go out the fan and vents, but it will go out every exit there is. its not going to ignore the holes in the ceiling and only go out the vents.
thats the main point just trying to get across. just because its plaster ceiling etc does not make it air tight. blowing air into a ceiling does pressurise it enough to blow air into the house (and vice vers with a attic fan)
the saving grace is the insulation which is acting as a filter, and you see the results of that in many homes.

as you say the solution is a hose and vent so it vents directly outside.

tweake,

I'm gonna have to take your word for it. I have no idea what Oscar's house looks like, how the garage is in relation to the house, etc...Oscar showed one pic of a fan in what looked to be drop down stairs into the attic. I have no idea what is up in the attic, what is connected to the fan or what little gaps you're referring to. I'm not sure how you can conclude all of the things you've stated above. I have no idea if he has a plaster ceiling, or how the ducting runs through the attic to the vents in the house, or how much pressure is in his attic or what is pushed into the house...I don't even know if his vents are in the floor or the attic...and more so, you've already got him on a death bed with a respirator on, heading to the hospital in an ambulance.

Oscar, can you put me in the will for that Invertig 400? Seriously, I'd probably be happy with the 221... Heck, I'm happy with my Primeweld!

I know how my house is and how my shop is, that's about it. Seriously, that's what's most important to me and what effects me directly.

[JustTheDad]

In the house I grew up in we had an atic fan that had moving louvers in the ceiling of the house. So it pulled air from the house through the ceiling into the attic, which was then forced out through soffit vents. I've been assuming that the attic fan Oscar has is through the roof, to keep his attic cool, not through the ceiling like in my old home.

If that's the case, then unless he has an awful lot of recessed lighting in his ceiling, the amount of exposure his family is going to get inside the house is so negligible, it's not worth worrying about. Painted drywall is actually a pretty good barrier. They'll probably get more exposure through an open window below one of the soft events somewhere in the house, and think what the volume of dilution there is... .

[Oscar]

Ha! Everybody wants my stuff! Vultures! :Lol: My cemetery plot is triple-wide. I'm taking everything with me!

Justthe dad, youre right about the attic fan, spot-on description. Recessed lighting is minimal; only 3 in the whole house, and there are a normal amount of A/C vents in the ceiling for a ~1500 sqft 3bd/2bath house, which are well hidden in the attic via fiberglass insulation.

Anyhow, I think this side-tracked conversation has gone on long enough. The sweltering heat here (107°F today) had me decide to add some kind of A/C to the garage, so I'll be changing the setup only because of that.

[TraditionalToolworks]

Ha! Everybody wants my stuff! Vultures! :Lol: My cemetery plot is triple-wide. I'm taking everything with me!

Well, that's a bad attitude... I'm gonna leave you one of my mills so you don't have to use that 3-in-1 POS...

Seems, like I mentioned above and tweake agreed, connecting some 12" hose to the fan and attaching it to the gable, you could just blow all the exhaust out the garage entirely. I see them for around $100. You can save $10 w/o bag.

https://www.amazon.com/MOUNTO-Flexible- ... =8-12&th=1

I'll be honest, I don't have any fume extraction other than a fan I can turn out and hope it blows some of it outside the garage.

[Oscar]

Not all homes have gables. So yea, if there was one, trust me I would have used it, and trust that at the time I thought about all other possibilities. The exterior is all brick, so even if there was space to run a duct to vent directly to the outside, it's not an endeavor I would have liked to embark on. In the end, my solution was the most feasible one. Soon I will have A/C in the garage and when that time comes, I will embark on the project of fume filtering within the confines of the garage without drawing in outside air, aka filtration. Luckily I already have the plan in my mind on using that same 12" ventilation fan as part of a large filter/carbon-trap to recirculate the air after being cleaned up, without taking up any floor-space. Once again the attic comes into play!

[TraditionalToolworks]

Not all homes have gables. So yea, if there was one, trust me I would have used it, and trust that at the time I thought about all other possibilities. The exterior is all brick, so even if there was space to run a duct to vent directly to the outside, it's not an endeavor I would have liked to embark on.

This is exactly why I was saying to tweake that I didn't know how anything could be determined by one pic...I hear you loud and clear Oscar, not trying to dictate what you do either, all homes are built differently...

As I build my new shop/home I'm gonna try and get things setup nicely, but it never works out 100% in my experience as plans change, designs need to be changed, etc...

Now you're just making me plain sick talking about AC if your shop...I'll like to say I'll have AC in my new shop, but that's so far down the road I can't even fathom those pieces just yet...other than I will have mostly floor vents and utilize the open ceiling in the basement for running ducting. I don't want anything exposed in the rest of the home, it's all open with timbers. Sprinklers will be difficult enough to conceal.

We've gotten pretty far off base in this thread, but I will end with private instruction is a good idea! Good to see Jonathan pop in here also, he does at least follow the forum occasionally.

[Oscar]

Now you're just making me plain sick talking about AC if your shop...

I'm not planning on having "so much" A/C that I will get to work in 70°F temps, not at all. Just small portable unit like this one in order to recirculate/cool the air down to perhaps 90°F instead of 110°F that it usually is year-round 'round here. Those 20°'s would make all the difference in the world. I like it because unlike other portable A/C's, that one cools the hot-side using outside-air by bringing it in via a separate hose, as opposed to other types that draw outside-air into the room itself because it is already expelling the heated air outside.

In fact, I'm setting up my LG 12k BTU portable A/C right now in the garage to see a worst-case scenario.

[Poland308]

That’s a spotcooler. You need to duct the condenser air outside or all it’s going to do is add heat and pull out a little humidity.

[Oscar]

That’s a spotcooler. You need to duct the condenser air outside or all it’s going to do is add heat and pull out a little humidity.

Yes, I know how it works.

[viktorthepirate]

With tig you won’t get much for sparks, but still a risk. Stick or mig is a different deal, as is any grinding. The nice thing about the fume hoods (not a nice price). Might be able to find a used one. Is that there made to handle even stick welding. We use them when we’re stuck in tight spaces or confined spaces to keep the fumes down.

Agree with Poland, I'd be a bit nervous shooting sparks into my attic. Risk is lower with TIG but still a risk. Stick or MIG I would recommend against that course of action.

You can get spark traps, but that also puts a bit of pressure drop on the fan which will affect performance... sometimes dramatically depending on the fan curve.

[Oscar]

With tig you won’t get much for sparks, but still a risk. Stick or mig is a different deal, as is any grinding. The nice thing about the fume hoods (not a nice price). Might be able to find a used one. Is that there made to handle even stick welding. We use them when we’re stuck in tight spaces or confined spaces to keep the fumes down.

Agree with Poland, I'd be a bit nervous shooting sparks into my attic. Risk is lower with TIG but still a risk. Stick or MIG I would recommend against that course of action.

You can get spark traps, but that also puts a bit of pressure drop on the fan which will affect performance... sometimes dramatically depending on the fan curve.

Don't worry. It's not pulling 2,000,000 CFM, and I don't weld anywhere near it. So no, contrary to what you're seeing in your mind, there are zero sparks being shot up into the attic.

[TraditionalToolworks]

Don't worry. It's not pulling 2,000,000 CFM, and I don't weld anywhere near it. So no, contrary to what you're seeing in your mind, there are zero sparks being shot up into the attic.

Just your typical Internet escalation. You've already caught your house on fire, burned to the ground and lost all your welding equipment.

[Oscar]

Yeap.

[viktorthepirate]

With tig you won’t get much for sparks, but still a risk. Stick or mig is a different deal, as is any grinding. The nice thing about the fume hoods (not a nice price). Might be able to find a used one. Is that there made to handle even stick welding. We use them when we’re stuck in tight spaces or confined spaces to keep the fumes down.

Agree with Poland, I'd be a bit nervous shooting sparks into my attic. Risk is lower with TIG but still a risk. Stick or MIG I would recommend against that course of action.

You can get spark traps, but that also puts a bit of pressure drop on the fan which will affect performance... sometimes dramatically depending on the fan curve.

Don't worry. It's not pulling 2,000,000 CFM, and I don't weld anywhere near it. So no, contrary to what you're seeing in your mind, there are zero sparks being shot up into the attic.

Happy to hear it

And of course your building already burned down lol

[JustTheDad]

I know we did many things wrong lol
We didn't clean the mill scale at all.
We melted a big hole the first time Eli tried to tack it.

But hey, for a first try on .06 steel tubing, it's not horrible. We're making a grooming table for a couple of 15 lb dogs, and this is going to be the arm. I think it will hold up to them.

The first try is the side we melted a hole in, maybe 3/16", mostly on one side. He patched it.
The second try is the other side. There's still a bit more to do, and we'll go over it with his teacher next week, but hey, it's a start.

[cj737]

to have air flow you must have air pressure. no pressure air doesn't move.
having lots of vents just means the pressure is lower.
however the big difference here is when talking houses the pressures are tiny. where talking 1000th of a psi.
but thats all it takes for air to flow through all cracks and gaps in the house. (0.007 psi is actually what they test houses with and thats quite brutal for a house.)

with any fan arrangement attic pressure will be different to inside house pressure, therefore you get air flow from one to another.

Tweake, you are dead right. The ventilation installed from soffit to ridge is based upon the volume of air drawn and exhausted by the roof system. Changing that by introducing a 2300CFM ventilator from the garage will absolutely force air into the home.

Oscar, I assure you, your attic is not vapor sealed to the degree you believe it to be. Now, whether the welding fumes are going to cause health or safety concerns, I think that is very remote. But, from a building science perspective, you have altered an engineered system without modifying to suit the change. That’s presuming a competent Mechanical Engineer designed the system (roof ventilation) to begin with and the builder of the home you own constructed it with any care... not terribly likely.

If you wish to confirm any of this, have a blower door test performed on your home. That will demonstrate exactly how badly your home leaks air, from every possible gap, even the ceiling. During said test, attic air will absolutely be drawn into the home. I’ll wager you large stacks of Benjamin’s on it.

And the batt insulation sitting on your ceiling in the attic is vapor permeable. So no air barrier there either. Unless you’ve had the ceiling, soffits, ridge and underside sheathing sprayed with close cell foam, your roof and attic are doing exactly what they’re designed to: leak air.

Apologies, Dad for the sidebar. I think anyone contemplating welding fume extraction needs to understand the venting into an attic is not an appropriate choice.

An attic fan works against you in general. It over-pressurized the attic, forces that hot, humid air into the home, and pulls conditioned cooler air out. They’re an absolutely myth and retarded system for cooling a house. You might as well open a window on the back wall, one on the front, and blow your AC conditioned air straight out the front of the house. Because that’s EXACTLY what you’re doing.

I return you now to your regularly schedule program already in progress

[TraditionalToolworks]

I know we did many things wrong lol
We didn't clean the mill scale at all.
We melted a big hole the first time Eli tried to tack it.

Move faster! Too slow, what amps?

Tube is easy to blow holes in, it’ll give you some experience filling the holes.

[Oscar]

cj737,

duly noted.

Justthedad,

For shame not cleaning millscale off! F — ! I assure you that weld would have been 10x better if you had. Not bad though. Definitely seen and done worse.

[JustTheDad]

We were figuring out the bandsaw and totally spaced on the mill scale.
Oops lol

[Superiorwelding]

Wow, this one went off topic fast, lol. Came back to see what the OP had said and we are talking attic fans and burning housed down. I needed a laugh for the night. Thank you for that.
-Jonathan