"Make-Up Air"

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egclassic

egclassic

Feeling the Heat
Jan 1, 2011
261
SW Ohio
I've been doing some winter weatherization around the house recently, caulking around windows and sills, sealing up any penetrations I can find.
I think I've created a "wind Tunnel" of sorts. When the stove (insert) is going full bore, I can feel a draft along the floor from the back of the house, to the stove. I can not pin point the source of air leakage directly, as in I feel it is coming from several places like through electrical outlets (which I have installed those insulators on) and maybe where the walls meet the floor. My house is a brick ranch, approx. 1700 sq. ft., with a full, finished basement built in the late 70's. It has insulation in the walls and I blew in more in the attic last year. Being in the plumbing business, I know that if I seal everything up to well, the stove will need make up air to run. My insert does not have an OAK connector. I thought if I could get some sort of make up air system closer to the stove, it would pull from there versus across the whole house resulting in this draft. I am just not sure how/where to get this make up air. I do not want to open a window, as this seems counter productive in weatherizing a home. Anyone else dealt with this situation and have any ideas?
 
I have a dedicated OAK so the stove is not a problem and I have a HRV that supplies makeup air to the house. Did you also seal up above the neutral pressure plane where warm air is leaking out?

I would run a makeup air duct to the stove and put a damper on it to regulate the amount of air.
 
Are you sure you are not just feeling a convection movement? Rather than fresh air entering?
 
Dakotas Dad said:
Are you sure you are not just feeling a convection movement? Rather than fresh air entering?
Click to expand...

Good point.
But there is definately some moving air, and it seems to be coming from one bedroom more than any of the others.
For a test, I closed all the bedroom and bathroom doors and put towels at the bottoms. I laid on the floor with an incense stick and had the wife open and then close each bedroom door one at a time. Once she opened the back bedroom door, the smoke went horizontal and I could barely see it. This room only has one window and two exterior walls. I even put the plastic window kit on it to see if it changed anything. My windows are "decent" vinyl double pane.
About running a duct to the stove, I can see no way to do this without being an eyesore, let alone getting the wife to approve it! The damper would be a good idea, but I'd probably use a barometric vent for automation.
 
An IR gun will give you lots of valuable information on leaks along with heat on various parts of the stove.
 
egclassic said:
Dakotas Dad said:
Are you sure you are not just feeling a convection movement? Rather than fresh air entering?
Click to expand...

Good point.
But there is definately some moving air, and it seems to be coming from one bedroom more than any of the others.
For a test, I closed all the bedroom and bathroom doors and put towels at the bottoms. I laid on the floor with an incense stick and had the wife open and then close each bedroom door one at a time. Once she opened the back bedroom door, the smoke went horizontal and I could barely see it. This room only has one window and two exterior walls. I even put the plastic window kit on it to see if it changed anything. My windows are "decent" vinyl double pane.
About running a duct to the stove, I can see no way to do this without being an eyesore, let alone getting the wife to approve it! The damper would be a good idea, but I'd probably use a barometric vent for automation.
Click to expand...

Man, the things we do in the name of efficiency. ;-P I'm imagining this whole sequence with you on the floor, incense burning, wife opening doors etc on youtube. I'll bet if we all had videos of the crazy things we've done in the search for more BTU's it would be an hysterical video.
 
WoodpileOCD said:
egclassic said:
Dakotas Dad said:
Are you sure you are not just feeling a convection movement? Rather than fresh air entering?
Click to expand...

Good point.
But there is definately some moving air, and it seems to be coming from one bedroom more than any of the others.
For a test, I closed all the bedroom and bathroom doors and put towels at the bottoms. I laid on the floor with an incense stick and had the wife open and then close each bedroom door one at a time. Once she opened the back bedroom door, the smoke went horizontal and I could barely see it. This room only has one window and two exterior walls. I even put the plastic window kit on it to see if it changed anything. My windows are "decent" vinyl double pane.
About running a duct to the stove, I can see no way to do this without being an eyesore, let alone getting the wife to approve it! The damper would be a good idea, but I'd probably use a barometric vent for automation.
Click to expand...

Man, the things we do in the name of efficiency. ;-P I'm imagining this whole sequence with you on the floor, incense burning, wife opening doors etc on youtube. I'll bet if we all had videos of the crazy things we've done in the search for more BTU's it would be an hysterical video.
Click to expand...

You ain't kiddin' :lol:

As Far as the IR gun, I just haven't gotten around to "aquiring" one from work, but I will soon! ;-P
 
egclassic said:
For a test, I closed all the bedroom and bathroom doors and put towels at the bottoms.
Click to expand...
Repeat the test without the towel and just check for a draft under the door. With the door open, you have the whole room convection thing happening. With it closed, there would only be air infiltration.
 
Norbert Senf does some calculations

From: Norbert Senf
Sent: Monday, September 16, 1996 7:40 PM

The Masonry Heater Association has a website at www.mha-net.org General information on masonry heaters can be found by clicking on "library".

There is a technical paper on outside air supplies for masonry heaters located on our own site at http://mha-net.org/msb/html/papers-n/airreq/cmhc-rep.htm

"Using the "Woodsim" software program developed by CMHC, we simulated the tightest house we could find, with an equivalent leakage area (ELA) of 25 sq.in., and using a typical air consumption for a masonry heater at full burn of 15 litres/sec., it resulted in a house depressurization of 2 pascals. Anything under 5 pascals is considered not worth worrying about. In other words, you don't need outside air for woodstoves or masonry heaters (although it is required by the Canadian building code). A couple of studies done to date also found that outside air supplies directly to the firebox had no effect on whether a fireplace (or stove) would spill combustion products into the house or not. You get spillage when negative pressure in the house (from turning on a Jennair, for example, or opening an upstairs window) is greater than the negative pressure (draft) that the chimney provides to the firebox. Both of these pressures are negative in relation to a reference, namely the ambient pressure outside the house. Bringing the firebox to outside pressure with makeup air doesn't help.

The worst case scenario is when your outside air inlet is located on the leeward side of the house. Whenever the wind blows, there is negative pressure on that side of the house, and there have been reported cases of flow reversals from the firebox into the outside air duct.

Best...Norbert Sen"

The above is an indication of the controversy surrounding this issue. Some believe that an HRV in a tight house is better than a dedicated duct to the fire box or it's immediate vicinity. I think Canada has revised it's code to require this type of duct to be constructed to standards for a chimney. I'm not advocating anything, but you could do some research and maybe save some bucks and have a better solution.

Ehouse
 
This topic is not about an OAK so there's no need to dredge up that old debate.

This topic is about general makeup air for the house and where to duct it to to reduce uncomfortable drafts. On a standard forced air furnace, the makeup air would be ducted to the cold return duct and the furnace would then warm the air. With a HRV, some of the chill is already taken off through the heat transfer so that the cold is less noticable when the furnace is not running.

I am a firm advocate of sealing above the neutral pressure plane to prevent warm air from escaping the building envelope. This is not just for reasons of comfort and energy conservation. Warm air leaving the envelope takes with it humidity which condenses inside the structure causing mold and rot.
 
Correct, this thread is not about an OAK but the principle is the same. I installed an OAK this year, and I notice much less problems with "cold chills" both where the stove is installed and in other rooms. I'm not suggesting that, as I realize that is not an option for the OP. I'm not sure I understand LLigetfa's suggestion, maybe some more clarification? Pulling in outside air through the furnace ductwork would a) be a potential for air infiltration year round, although your damper suggestion greatly reduces this, b) creates a more positive pressure in the house (albeit, perhaps not truly "positive" depending on draft of the chimney) which would actually cause more warm air to leave the envelope through cracks and c) warm the air through the furnace before it goes up the chimney which would be less cost-effective. Also, how often is your furnace running? If it is not running much, I don't know think you would gain a lot with this method. Again, perhaps I misunderstand his suggestion.

I don't think cracking a window in the room with the insert is such a bad thing, but only maybe 1/2"-1". I realize that sounds crazy, but your insert is going to pull that air in from outside. Either from the bedroom you're describing or from the room with the insert. At least with the room with the insert the extra heat will keep the room comfortable. You're bedroom (where you feel the draft now) doesn't have the luxury of having that heat brought in. I would say repeat your test, but this time with a window in the insert room cracked. If your smoke moves the same way, then the draft is probably not from the stove pulling air in. Also, did you attic seal before adding insulation? All the nooks and crannies up there?

One last thought...gotta love the things our wives will help us with in our quest! I told me wife to get me some incense a few days ago and she really thought I was turning into a hippie.
 
Just an idea. Since I have an insert, and they removed the old ash hatch from the fireplace, would it be possible (effective) if I ran a duct from the clean out in the basement through the outside wall (like my dryer vent?)
Logically, it seems that the insert would pull the air up from the bottom, rather than from the other end of the house. Surely I'm missing something here so input is encouraged.
 
kmachn said:
Again, perhaps I misunderstand his suggestion...
Click to expand...
the makeup air connection to the furnace return was not a suggestion but rather a statement of fact regarding standard building practices.

http://www.americanaldes.com/library/ventilation-solutions/installing-hrv/

hrv-installation.png
 
egclassic said:
Just an idea. Since I have an insert, and they removed the old ash hatch from the fireplace, would it be possible (effective) if I ran a duct from the clean out in the basement through the outside wall (like my dryer vent?)
Logically, it seems that the insert would pull the air up from the bottom, rather than from the other end of the house. Surely I'm missing something here so input is encouraged.
Click to expand...
Ja, make use of the existing ash hatch if the air has a route to the room. If the insert is sealed to the hearth and there isn't a block-off plate, the air may want to go up the tile flue.

If the insert is not well sealed to the hearth and there is no block-off plate, running the stove can induce a draft up the tile flue and could be the reason for your cold drafts.
 
What is covering the ash hatch since they took the lid? That right there may be letting plenty of air in.
 
"The worst case scenario is when your outside air inlet is located on the leeward side of the house. Whenever the wind blows, there is negative pressure on that side of the house, and there have been reported cases of flow reversals from the firebox into the outside air duct."

The difference between a dryer vent and your proposed duct to the ash hatch is that the dryer is an exhaust which is induced, while your duct is a neutral passageway and can allow air flow in either direction even though the intent is an intake. Sure, if the stove is drawing well you'll get the desired flow, but if the fire is low, or draft is weak and negative pressure builds outside ( see above) you could smoke yourself out or pull your fire right out the tail end!

Ehouse
 
Huh? Here you go again debating a dedicated OAK. Again, this topic is not about an OAK. It is about makeup air to the room. I wish you would read what is posted.
 
LLigetfa, You seem to be getting increasingly annoyed over this, but I don't understand your objections. egclassic is definitly talking about ducting outside air to the stove, specifically, from the outside wall to the ash hatch via the basement cleanout. This is the situation I'm addressing. He is also repeating his request for suggestions and input, so I'll be happy to shut up if he says my input is irrelevant. What about it egclassic?

Ehouse
 
Ehouse said:
LLigetfa, You seem to be getting increasingly annoyed over this, but I don't understand your objections.
Click to expand...
Yes, I am getting annoyed because you keep raising points that pertain only to a dedicated OAK when this is not at all about that. Why do you insist on derailing this topic to discuss possible OAK issues?

How would a makeup air vent that is not direct coupled to the stove cause a reversal like what a dedicated OAK might under a worst case hypothetical situation?
 
Ehouse said:
LLigetfa, You seem to be getting increasingly annoyed over this, but I don't understand your objections. egclassic is definitly talking about ducting outside air to the stove, specifically, from the outside wall to the ash hatch via the basement cleanout. This is the situation I'm addressing. He is also repeating his request for suggestions and input, so I'll be happy to shut up if he says my input is irrelevant. What about it egclassic?

Ehouse
Click to expand...

I am open to all suggestions. I was merely hoping that if I could supply the insert with combustion air some where closer to the stove itself then it would not be as apt to "pull" cold air in from assorted leaky spots all over the house creating this "drafty" feeling.
As far as a dedicated OAK, my stove does not have this type of connection on it as I know some do. But either an OAK or just make up air, to me, seems to perform the same function, supply combustion air.

Hog,
The stove itself is sitting on top of the ash hatch, about 1-2" gap between the bottom of the stove and the hatch. Clean out door is in the much cooler basement. I am going to try and leave the clean out door open for awhile to see if it helps. Even though its not sealed tight, being closed creates more resistance.
 
Ehouse said:
egclassic is definitly talking about ducting outside air to the stove...
Click to expand...
No, not coupled to the stove, just to the area near the stove, which is not the same. The ash cleanout is not part of the stove but rather part of the original fireplace into which the stove is placed.
 
egclassic said:
I was merely hoping that if I could supply the insert with combustion air some where closer to the stove itself then it would not be as apt to "pull" cold air in from assorted leaky spots all over the house creating this "drafty" feeling...
Click to expand...
Are you sure that the draft you feel is entirely due to combustion air consumption and not air being sucked up the tile flue?

It could also be that the hotter air the stove produces is leaking out of the structure at a faster rate.
 
Coupled or uncoupled, the duct will still accomodate air flow in either direction so if you go that route you might want to put in a flap that only allows the air to flow one way, as well as a damper. Another safety consideration is to not place the intake near any fuel tanks or driveways where fumes or exhaust can be pulled into the house. This would include the basement clean out if you have oil tanks, gas lines, paints or other volatiles stored there. Run a bead of painters caulk top and bottom on the baseboards in the bedroom and it might help with the draft. Ehouse
 
LLigetfa said:
egclassic said:
I was merely hoping that if I could supply the insert with combustion air some where closer to the stove itself then it would not be as apt to "pull" cold air in from assorted leaky spots all over the house creating this "drafty" feeling...
Click to expand...
Are you sure that the draft you feel is entirely due to combustion air consumption and not air being sucked up the tile flue?

It could also be that the hotter air the stove produces is leaking out of the structure at a faster rate.
Click to expand...

If I leave the back bedroom door closed, I feel no draft. Once I open it, I immediately feel a draft. Of course, with the door closed, the room gets very cold but it is an unused room. I realize that all that cold air is going to be drawn to the heat (cold seeks heat or is it the other way around?) Right now I am letting the room get warmed up and see if as the temps rise, the draft goes away. Its weird because I did not have this issue last year. This particular room has always been colder than the other bedrooms. When my youngest daughter lived here, she always complained about it being cold in there. I just blew it off because like a typical teenager, she ran around the house in shorts and tees all the time, but she's been gone for 4 years now.
 
Hotter air is lighter and so more buoyant and as a result will want to rise. As it rises, the cold heavy air will rush in to take its place.

The reason I suggested the closed door test was that would reduce convection as a source or the draft. If air infiltrates under the door, that suggests outside air may be flowing through that room and seeking a route under the door.

I have a two storey house with the wood stove on the main floor which is open concept. The heat naturally rises up the stairwell and conversely, the cold air from upstairs rolls down the stairs. It is quite noticeable and does not indicate that I have outside air infiltrating from upstairs. The upper floor after all, is above the neutral pressure plane so air would exit, not infiltrate through any opening in the building envelope.
 
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