Best ZC EPA Phase II Certified Fireplace that doesn't leak in cold air

[Wxtrendsguy]

About 10 years I had a FPX 44 for 3 years and did the job heating a large great room...great big heater and a bit hungry for fuel, air cooled chimney, combustion air was piped in from outside through u-shaped duct in basement to minimize air infiltration.

Now for the last 5 year in current house we have a Heat n Glo Northstar...again air cooled chimney, combustion air is straight piped into the unit, additionally there is a chimney cooling kit which adds another pipe from the outside and feeds the base of the chimney air layer from the bottom. Works beautifully as designed to keep chimney cool.

So I liked both units very much except for one minor detail...and I am sure you who own them know what it is...

When the fireplace is not in use there may as well be a window open in the house as cold air floods down the chimney air cooled sleeve and leaks out all over the place in the cavity the unit is in and then floods into the house. I don't think I am getting too much leakage from the combustion air as the unit looks more sealed than the FPX ever did.

So yep you guessed it we are building a new house in 2013...smaller 2,500 sq ft, spray foamed building envelope, trying to achieve a house that is very airtight so that it can be heated with a high efficiency heat pump. (yea yea I know they find nat gas in every hole in Pennsylvania but there are still no pipelines bringing it for residential use...so stuck with oil, propane or electric....electric is cheapest)
Still want a wood burner for supplemental heat. Wife is not keen on a woodstove and Masonry Heaters are just too expensive and rather ugly and bulky. So there has got to be a ZC fireplace that meets my needs...with minimal air leakage when not in use...

Any help?

 

[webby3650]

Actually the new FPX fireplace would fit your needs. It has the new Hybrid Technology, so it's cat and secondary tube. It uses insulated 6" Class A chimney, and no longer uses outside air to cool anything. It only uses outside air for combustion, like a woodstove. It's still in production, hopefully it will be available this summer. We saw it at the HPBA show in Orlando a few weeks ago.

 

[daryl]

Check out any unit that uses Class A chimney not air cooled fireplace chimney. Security,( same as Lennox) Kozy Heat,Energy King,RSF just to name a few.

 

[Wxtrendsguy]

That was the path I was thinking about Daryl.

Now how to get the chimney chase sealed and insulated where the pipe goes through the roof. Chase will be on the inside of the house but that penetration through the top of the chase is key to sealing in the air and preventing a huge stack effect...

 

[webby3650]

That was the path I was thinking about Daryl.

Now how to get the chimney chase sealed and insulated where the pipe goes through the roof. Chase will be on the inside of the house but that penetration through the top of the chase is key to sealing in the air and preventing a huge stack effect...

The chase cover isn't the biggest concern really. You need to make a draft stop at ceiling level.

 

[aansorge]

Enerzone 2.5 ZC and its twins....

 

[Wxtrendsguy]

The chase cover isn't the biggest concern really. You need to make a draft stop at ceiling level.

How do you make a draft stop when all the literature seems to always say to leave a 1" or 2" airspace between the pipe and insulation?

I did see something about using silicone caulk between the drywall ceiling and the pipe but again I though it was supposed to have a gap.

Also doesn't the fireplace chimney expand up and down depending on temperature? I'd think that would quickly make the caulking seal ineffective...I know my air cooled chimney would get significantly taller and shorter depending on the fire...

 

[webby3650]

You use a metal firestop from the manufacturer, it maintains the 2" clearance to combustibles.

 

[Wxtrendsguy]

You use a metal firestop from the manufacturer, it maintains the 2" clearance to combustibles.

Understand that but how do you seal the crack between the pipe and the metal firestop. A simple 1/4" gap all the way around lets say an 8" flue leave a hole in the house of approximately 6 sq inches, which is exaggerated by the fact that cold air will be sitting on top of the hole and gravity will allow it to fall pretty quickly though the hole and into the chase around firebox again making everything very cold.

I have seen enough wood stove installs that tell me it has to be possible to put a hole in the roof but still maintain both a weather and airtight seal. But then again I have also seen enough where you can see the water has run down along the pipe indicating there is no seal.

 

[webby3650]

Red silicone works. I don't see that very small crack between the firestop and the pipe being too much of an issue if the chase is insulated and has an insulated draft stop.

 

[Rickb]

I just did this on my new stove install that has class A pipe run in a external chase.

It seals really easily. Then before I add a metal fire stop I will be adding a bunch of roxul. It is fire proof and can rest right next to your chimney pipe and will help act as a air stop.

To be honest I havent added the fire stop or the roxul yet and have noticed no air coming down the chase at all. Of course the top of my chase is caulked with "through roof" sealant.

 

[Wxtrendsguy]

Is there a ZC fireplace that only uses outside combustion air to feed the fire. In other words do all wood burning units use both inside air and then if there is an outside air kit it can pull from there as well but its never really isolated from the inside. I think that is a big cause of the draft because you cannot isolate the outside air into the sealed firebox, instead it feeds into the space around the firebox but that outside steel layer around the firebox is not sealed and the air leaks into the room especially when the house is under negative pressure on the first floor due to the stack effect in a house.
With any luck my new house will have a minimal stack effect. This is going to be fun to figure out.

 

[webby3650]

Is there a ZC fireplace that only uses outside combustion air to feed the fire

Yes, most require an outside duct that is dedicated for combustion air. Like I mentioned above, the new FPX is that way, as well as the Kozy Z-42, Supreme, and the Valcourt/SBI units. Just to name a few. I have installed all of these units in the past and have never heard any complaints about cold air infiltration. Cold air problems usually stem from the builder not properly insulating the chase.

 

[Heatsource]

. Then before I add a metal fire stop I will be adding a bunch of roxul. It is fire proof and can rest right next to your chimney pipe and will help act as a air stop.

.

no, even fireproof insulation should not be up against the pipe!

 

[Wxtrendsguy]

Yes, most require an outside duct that is dedicated for combustion air. Like I mentioned above, the new FPX is that way, as well as the Kozy Z-42, Supreme, and the Valcourt/SBI units. Just to name a few. I have installed all of these units in the past and have never heard any complaints about cold air infiltration. Cold air problems usually stem from the builder not properly insulating the chase.

Hi Webby,

Thanks for the info. Unfortunately when I look at pictures or schematics of those units they tend to be pretty vague on how combustion air is feed into the firebox. I'd love a fireplace where I can isolate from where the unit draws its combustion air from. The North Star I have now seems to do it fairly well but the turn knob rarely stays closed and the damper flops open if there is any negative air pressure in the house even when the unit is off which tells me the overall combustion air intake is not isolated from the house air. Which I guess makes sense when one considers that you can burn the unit with the OAK damper in the closed position. But that darn damper flopping open on its own sometimes just allows cold air to flow into the house when the unit is off. It bit of a PITA.

 

[begreen]

That was the path I was thinking about Daryl.

Now how to get the chimney chase sealed and insulated where the pipe goes through the roof. Chase will be on the inside of the house but that penetration through the top of the chase is key to sealing in the air and preventing a huge stack effect...

Ya don't do that. Take a look at class A roof flashings. They are ventilated. But you can insulate and seal the chase above the firestop to minimize infiltration.