I don't want to install a fresh air intake, but do I need one?

I don't really want to install a fresh air intake unless I absolutely need one. I don't think it would be easy to install one into my hearth given the set up, and I have read a lot of mixed things about them. I have a Woodstock Absolute Steel. My house is tight (SIP's). I have a HRV. Anyway, I did what I think is called a smoke test. It was a damp, heavy air day, so that may have impacted the test some. I closed all the windows and exterior doors in the house. I closed the doors to two bedrooms because they have air conditioners in them right now (so the test wasn't perfect maybe). I put the HRV fan on the lowest setting (fan has 5 speeds). I held a lighter at where the air comes into the stove at the back of the stove. When the HRV fan speed was at 1, the flame was neutral and maybe sucked in toward the stove a little. When the HRV fan speed was at 2, the flame seemed to be drawn in a bit more into the stove (not sure why the fan speed would make a difference, I would think the amount of air going out and the amount of air coming in would be the same despite fan speed). Then, I turned on the clothes drier and the flame definitely pushed away from the stove air intake. I tried turning the fan speed on the HRV up to higher settings, but it didn't seem to make a difference. I seemed to have to crack a window open several inches to make a difference. What do you all think?

 

P.S. On the side of the HRV it says that it's always important to assess how the HRV interacts with vented combustion equipment (like woodstoves). My father-in-law calibrated it. He knew just enough to be dangerous. Maybe I should have an HVAC guy come and calibrate it?

 

Does the HRV blow cool air in or warm air out? How tall is your chimney? I suspect that if your chimney is over 15’ or so, you won’t have an issue. Just a guess..

 

Did some research on HRV's. They bring fresh air in to a heat exchanger and exhaust inside air thru the other side of the heat exchanger. If you can run the incoming fan at a faster speed than the exhaust fan, then maybe it would help.
Exhaust fans, dryer and gas/oil fired heaters all need to be accounted for when testing.

 

My chimney is 25 feet tall. The HRV uses the energy from the air exiting the house to warm the air coming into the house. When my father in law balanced the HRV, I'm not sure if he took into consideration the air that would be drawn from the wood stove, and he's gone now, so I can't ask him. You cannot make the fan speed different for the air coming in versus the air going out. When you set the fan speed, it's the same speed for both air going out and air coming in. I think the way you control how much air is coming in versus how much air is going out is by adjusting the bell at the end of the duct. It screws in and out. So if you close it more, less air. If you open it more, more air. One each level of my house there's one duct/bell for fresh air coming into the house and one bell/duct for air being sucked out of the house. Maybe I should just have an HVAC guy come and make sure it's all balanced and in concert with the wood stove.
The smoke test that I did was obviously when the stove was cold, no fire, and when the HRV was running at the lowest fan speed, the flame on the lighter was neutral, sometimes drawn into the stove slightly. I imaging when the stove is running, and the chimney is heated, that would draw more. I just don't know about that competing clothes drier. That definitely caused negative pressure and pushed the flame away from the stove.

 

Sounds like a inexpensive manometer (like a Dwyer Mark II model 25) needs to be used on the stove/chimney...see what the pressures really are...but if this house is tight enough to need an HRV, I'm saying you NEED an OAK for the stove.

 

I won’t charge you a dime for this...

Just crack a window and be done with it. Less money, less headache, and quite adjustable to your needs. No extra thought required.

 

Dunno about your house, but having a window cracked all winter would never fly at my house.

 

Other than the difficulty of routing the outside air pipe, I have yet to hear a good reason not to run outside air for combustion. Lots of benefits and it just makes sense to burn unconditioned air instead of your valuable heated, clean, and humidified air.

 

Cracking a window sounds counter intuitive to me. So where do I find one of these outside air kits to buy. Is someone on here able to help me find one? I’ve looked online and they confuse me. Looks like most of them say they are for pellet stoves.

 

https://friendlyfires.ca/products/outside-air-kit-for-wood-burning-appliances-uzi-aftermarket-kit/

Is this what I need? Would this work?

 

It might work...what does the fresh air connection look like on the AS?
That kit is kinda pricey for what it is...could buy the same parts at HD for much less...

 

The AS has a 4 inch round port on the back to receive a 4 inch, essentially a flexible drier duct. So, you’re saying just go to Home Depot and buy the parts to make up my own kit?

 

Yes. Plumb this thing like a dryer vent except take the flapper out of the little hood thing at the end if you go out the sidewall. All metallic duct or flex. My current one is 4” the whole way into my ventilated crawl space under the house.

Remember, you can’t go up with the intake pipe. It all needs to be below the firebox floor so that it doesn’t become a chimney!

 

What he said...make sure you get the insulation sleeve for it too.

 

Right! I’m going to have a friend contractor drill through my hearth and I to the basement so I don’t mess it up or hit anything important. Then, I can do the rest. It’ll have to have some curves in it and will need to go back up a little to avoid the chimney and floor joists. I’ve read that it’s important to wrap it in insulation so condensation won’t build up.

 

Oops. Didn’t see Brenndatomu’s post til now.

 

Good luck, and I have a suspicion that come the middle of the winter we're going to see a post that says something along the lines of "I'm really happy I went ahead with the OAK."
Great stove by the way from everything I've read.

 

One more question. In the stove manual, it says to use a“4 inch pipe, usually flexible dryer duct” and “for longer runs you can transition to pvc or aluminum pipe”. Isn’t most flexible dryer duct made from aluminum? I would think that you would definitely want to use a duct made from some sort of metal, whether is aluminum or another type of metal.

 

Kind of like with a dryer, if you have a short run the flexible duct is fine, but if you have a longer run you wouldn't want the ducting to sag in a bunch of areas or "roller coaster".
How long is the total run that you're going to install?
Simple me is thinking the less bends and turns the air has to make the better, but perhaps that isn't as much of a concern for the intake.