Outside Air intake?

[Black Jaque Janaviac]

When I bought my VC Montpelier I was told by the dealer that there were outside air intakes available. Since the initial price tag was enough for one year, I figured I could buy the air intake kit later.

Well now it's later and my dealer won't get back to me on the matter. And I cannot find a peep on the internet about it.

Does anyone here have a Montpelier with an outside air intake? How does it work? How did you come by it?

 

[cptoneleg]

WWWats Up Doc

 

[nate379]

Get a dryer vent, the kind either plastic or metal, don't matter. They have a 3" pipe like 24" long on it.

Use that to go through the wall, and then get corrugated tubing, 3", connect from vent to stove.

That is all the stove shop here uses... kind of bugged me in a way because it was like $20 worth of materials and they charged me $50 for it.

 

[vvvv]

Get a dryer vent, the kind either plastic or metal, don't matter. They have a 3" pipe like 24" long on it.

Use that to go through the wall, and then get corrugated tubing, 3", connect from vent to stove.

That is all the stove shop here uses... kind of bugged me in a way because it was like $20 worth of materials and they charged me $50 for it.

plastic can burn or melt, manual says no-no + ins. co. wont like & under right conditions stove can backdraft thru OAK

 

[nate379]

That is what stove shop here uses, don't know what you tell you. Metal one would work just the same though.

 

[CountryBoy19]

That is what stove shop here uses, don't know what you tell you. Metal one would work just the same though.

Depending on what your building codes are up there, the shop may be breaking code by using plastic. Even if it's not against code it's a really bad idea... I just wouldn't risk it; there really isn't much difference in price so why would you even think about risking that?

 

[nate379]

No enforced building codes. Would imagine if sparks would could out of that vent it would set the grass outside on fire??

 

[vvvv]

No enforced building codes. Would imagine if sparks would could out of that vent it would set the grass outside on fire??

http://www.woodheat.org/outdoorair/outdoorairmyth.htm

 

[nate379]

I have a "passive air inlet" but it's not enough if the dryer is running and bath fans are on. I have to open a window a bit if I want to open the stove door and not have smoke come in the house.

My boiler works the same, intake and exhaust are both outside.

 

[CountryBoy19]

No enforced building codes. Would imagine if sparks would could out of that vent it would set the grass outside on fire??

http://www.woodheat.org/outdoorair/outdoorairmyth.htm

That is why (even though it's recommend that you don't do it) I recommend terminating an OAK into a well ventilated attic space if possible. Yes, if you get a reverse draft (very, very unlikely if it's terminated into an attic space and you have a proper chimney) you're going to get a lot of smoke in there, but it's in the attic and not in the home. Terminating in the attic space (well ventilated) negates the effects of negative/positive pressures because any pressure on one side is relieved by venting on the other side.

I know that they all have ups and downs; but this is what worked best for me. If I was to run my OAK outside like "they" say, one side of the house would yield a big positive pressure and challenging routing + possibly blockage by drifting snow; the other side would have been a negative pressure + extremely challenging routing plus bad location to have the OAK vent. My attic is ventilated pretty well, so I decided that routing my OAK into the attic would be the best option for negative/positive pressures, and if a reverse draft were to happen, it would simply vent into the attic and not be a problem.

 

[vvvv]

No enforced building codes. Would imagine if sparks would could out of that vent it would set the grass outside on fire??

http://www.woodheat.org/outdoorair/outdoorairmyth.htm

That is why (even though it's recommend that you don't do it) I recommend terminating an OAK into a well ventilated attic space if possible. Yes, if you get a reverse draft (very, very unlikely if it's terminated into an attic space and you have a proper chimney) you're going to get a lot of smoke in there, but it's in the attic and not in the home. Terminating in the attic space (well ventilated) negates the effects of negative/positive pressures because any pressure on one side is relieved by venting on the other side.

I know that they all have ups and downs; but this is what worked best for me. If I was to run my OAK outside like "they" say, one side of the house would yield a big positive pressure and challenging routing + possibly blockage by drifting snow; the other side would have been a negative pressure + extremely challenging routing plus bad location to have the OAK vent. My attic is ventilated pretty well, so I decided that routing my OAK into the attic would be the best option for negative/positive pressures, and if a reverse draft were to happen, it would simply vent into the attic and not be a problem.

proper OAK shold be connected to opposite sides of the house for air inlets.

 

[begreen]

a proper oak should not have more than 15' of piping.

 

[vvvv]

a proper oak should not have more than 15' of piping.

cant the pipe size be increased to go furhter?

 

[begreen]

Y? i've never seen an oak put on the opposite side of a house, especially if it is a long run of pipe. have u? provide docs plz.

 

[vvvv]

Y? i've never seen an oak put on the opposite side of a house, especially if it is a long run of pipe. have u? provide docs plz.

" good observation That could happen not likely though
As explained to me the correct way to install an outside air feed is to y it off
so that it has two outlets to the outside on opposite sides of the home This way when wind hits a home positive pressure is on the windy side and negative pressure on the leeward side. Having to inlet would neutralize the wind effect and prevent the situation you indicated. Then again I have never seen it done this way. Nobody takes the time or thought to address it. It is not code to have two inlets." Elkimmeg 3/30/08

 

[CountryBoy19]

proper OAK shold be connected to opposite sides of the house for air inlets.

See that's just it. One source says this, the other says this.

I was going to have to run about 60' of piping plus several odd bends etc to put it on both sides of the house. By running it into the attic space you are essentially following the same principle but it's even better. With a well ventilated attic you have vents on all sides of the house to equalize the pressure and I only have 8' of pipe with 1 bend in it.

I can actually think of one negative thing about running an OAK to both sides (other than the fact that you'll likely have a really long run). To do a proper hookup to equalize the pressures on each side of the house your ducting needs to run from the stove and then T off to each side. If you do any other method (Y or T 90* off etc) then you still run the risk of having pressure issues. But, with the perfectly oriented tee, on windy days you're going to get a cross-flow through the duct, and that will create a decrease in pressure (Bernoulli's Principle) which still gives you negative pressure and possible reverse draft.

If you vent into the attic space, the pressures are still equalized but because the attic acts as a VERY LARGE duct, the air velocity is negligible therefore you don't get the pressure drop due to Bernoulli's principle.

The benefit of venting into the attic all comes at the risk of getting smoke in there in the event of a reverse draft, and you could possibly end up with fire if it's a really, really bad reverse draft. However, the chances of a reverse draft are minimized as well.

My non-expert opinion? Do it however best works for you, it's better to have it on a positive pressure side of the house than negative, but if you have an attic it can be terminated to more easily, the odds of something bad happening may actually be decreased by terminating it into the attic. I don't think anybody really even knows. There are a lot of thoughts and theories on it (my posts are just thoughts and theories mostly) and even the officials that adopted codes mandating OAKs in some places didn't even understand how they truly worked.

 

[nate379]

Not sure what to tell you but this weekend we had 60-70mph winds and no problems with the fire I had going in the stove. The last time we had wind like this it sucked the attic entrance up into the attic, so I would imagine that wouldn't work well for a OAK!

To run it on the other side of the house I would have needed to tear apart tons of drywall and run about 60ft of pipe and several bends.

If you are worried about a plastic vent melting, how does running it in the attic make sense? I would not want any embers landing on wood or insulation up there!

 

[CountryBoy19]

Not sure what to tell you but this weekend we had 60-70mph winds and no problems with the fire I had going in the stove. The last time we had wind like this it sucked the attic entrance up into the attic, so I would imagine that wouldn't work well for a OAK!

To run it on the other side of the house I would have needed to tear apart tons of drywall and run about 60ft of pipe and several bends.

If your attic entrance got sucked up by the winds then you certainly don't have a properly ventilated attic. Your attic should allow free movement of air in all directions but not allow actual gusts of wind inside the space. Don't know what to tell you about that. Also, I never said that you would have problems with an OAK outside of the house, just that you're less likely to have problems if you terminate it into a properly ventilated attic space.

If you are worried about a plastic vent melting, how does running it in the attic make sense? I would not want any embers landing on wood or insulation up there!

plastic pipe 3" from the stove is a LOT different than hot smoke rising 8' vertically through metal pipe and terminating in the attic.

If you ever have a reverse draft:
#1, Plastic pipe will melt and start leaking smoke/gasses into the living quarters
#2, The number of hot embers and the temperature of flames will be magnitudes larger 3" from the stove than they will be 8' from the stove. Your plastic pipe just melted exposing the wall/floor to all these hot embers and gasses.
#3, Fiberlass insulation isn't really "flammable" it takes a lot of heat to get it just to smolder, if you get that kind of heat back through your OAK you have other problems to worry about.
#4, given proper "termination" in the attic, the hazards of a fire catching from embers expelled up through the OAK are minimized. My oak terminates into a sheet metal box. For there to be a hazard from embers catching the attic on fire there would have to be one heck of a fire back-feeding through the OAK to force embers 8' feet through a screen into a sheet metal box then down through another screen and up out of the box. If you have a reverse draft bad enough for that to be a problem then the plastic pipe was a ball of fire about 30 minutes ago.

 

[begreen]

The intent of the OAK is to solve a problem that lack other practical solutions. If the problem doesn't exist, could be money is better spent elsewhere? I don't ever remember a poster needing an oak plumbed to the opposite side of the house, though I might have missed it. However, I could see locating the opening around the corner if there is a problem with prevailing winds.

 

[nate379]

With the entrance sucking up, too much air running across the ridge vent I think... or the entrance is in my garage, so maybe wind blowing in there. My neighbor had it happen to his place as well.

Plastic Pipe?? My pipe is all metal, the actual vent cover is plastic.... the part that would have the flapper on the dryer install.

 

[dstover]

OAK must go to opposite side of the house? I'm not sure what this means.

My stove draws air through a metal duct from the crawl space below the stove. A possible solution for houses with crawl spaces rather than basements or slab construction.

 

[Black Jaque Janaviac]

Hmmm. I wonder what all this means when you have a fireplace insert, such as the Montpelier installed in a masonry fireplace?

I'm thinking maybe I could just pop out the outside air intake panel, and seal the surround panel with RTV caulk. The masonry fireplace has a old ash clean out that I could leave open.

I'm not sure what to make of the WoodHeat.com link. The drawings of depicting wind arrows going down the flue don't seem right. I've always understood that wind traveling across a horizontal-plane opening would HELP the draft. Is that Venturi's or Bernouli's principal?

But the idea that the 25 cfm draft is a mere pettence compared to the usual air loss due to windows and doors is a strong argument - if it's believable.

If I pop out the air intake panel on my Montpelier what can I expect to see behind the pop-out panel?

 

[CountryBoy19]

I'm not sure what to make of the WoodHeat.com link. The drawings of depicting wind arrows going down the flue don't seem right. I've always understood that wind traveling across a horizontal-plane opening would HELP the draft. Is that Venturi's or Bernouli's principal?

That would be Bernoulli's; but there are other forces to consider. What you see depicted in that picture is the OAK is on the downwind side of the house where you'll have a large negative pressure (also a result of Bernoulli's principle). This large negative pressures in the OAK is greater than the negative pressure across the top of the flue. That will mean that the draft reverses and flows down the flue and out through the OAK.

I am not saying that it will happen; just saying what is depicted in the picture. The actual likelihood of something similar happening depends greatly on the location of your OAK, the direction and speed of the wind, height of your flue, and all of the surroundings that affect the wind.