Outside Air Kit - Ducting Length

[PHD12]

I found lots of great information in several older threads, but wasn't able to locate a discussion of my particular issue. I can understand the arguments against an OAK, but believe it to be the best option in our case.

We're building a new house, which will be fairly tight (Energy Star Certified, ERV, aggressive air sealing) and we have designed a central location for a freestanding wood stove. We have chosen a Lopi Endeavor based on efficiency, design and local availability. Unfortunately, their techinical guidance calls for a maximum duct length of 15-feet for an OAK. Our run will be in the neighborhood of 19-feet.

The hearth is centrally located in a room with a half-vaulted ceiling, so there will be about 15-feet of straight 6" flue in the conditioned space before it exits near the peak of the roof. The outdoor air would leave the bottom of the stove, straight down through the 18" tall raised hearth and through the floor into the truss cavity, one 90-degree bend then about 17-feet to an outside wall. The intake is under a covered porch and on the north side of the house. This is our shortest distance to an exterior wall.

Does anyone have any experience with a fresh air intake of that length? Or any advice? We break ground in a couple weeks. Thanks in advance.

 

[begreen]

Sounds like good planning. A centrally located stove and chimney in the house envelope are a good start. To reduce air resistance I would go up a size to 5" for the 19' run and 90 deg elbow, then transition to 4" to go up to the stove.

One glitch in the plan is the cathedral ceiling. Heat is going to want to pocket near the peak. For sure you will need ceiling fans to help circulate this warm air but in some designs even this doesn't work great.

 

[PHD12]

I was thinking that upsizing the duct might be worth a shot. Thanks!

We will have 2 ceiling fans in that area and are hopeful that it will help to some degree. The ERV may help to distribute the heat somewhat as well.

Anyone else have any experience with a longer duct run of this sort?

 

[Oldman47]

By upsizing you reduce turbulence in the OAK piping and get laminar flow for most of that distance. That should put you in good shape for decent air flow.

 

[Highbeam]

We have chosen a Lopi Endeavor based on efficiency, design and local availability.

So what makes you think a Lopi is particularly efficient? It is certainly an expensive non-cat. With new construction and your apparent attention to detail I would expect your home to be well sealed and insulated. The Lopi non-cat will not have a low fire setting like some of the other options.

 

[PHD12]

By upsizing you reduce turbulence in the OAK piping and get laminar flow for most of that distance. That should put you in good shape for decent air flow.

Thanks. This will primarily be a supplementary heating source, except during power outages and we won't have to worry about range hoods, dryers and the ERV during those times. So I feel a little better now about our setup.

 

[PHD12]

So what makes you think a Lopi is particularly efficient? It is certainly an expensive non-cat. With new construction and your apparent attention to detail I would expect your home to be well sealed and insulated. The Lopi non-cat will not have a low fire setting like some of the other options.

We were specifically shopping for a non-cat. And one of the design features we wanted was the step-top, so that limited our pool of candidates. And our 3 closest dealers all carry Lopi products. Plus, the Endeavor is already under 2.0 grams per hour, which future-proofs it to an extent against unpredictable new regulations.

Thanks all for the feedback.

 

[begreen]

Sounds like a good choice. The Endeavor is a well made non-cat stove with a fire-brick baffle instead of baffle board and a flue bypass for easy starts. The stove runs well on partial loads of fuel and is simple to run. At 1.9 gms/hr it is quite an efficient and clean burner. And it provides a nice fire view with a clean glass.