Chimney liner options

[Hunterfire]

Hello,

First time post been reading lots of valuable information here.

I recently had my chimney inspected and learned that my 1947 house has an unlined chimney, I learned this is not safe to use. The inspector gave me a cost to repair that was much higher than I was willing to pay. I started looking into a wood insert. (This site has been an invaluable source) and think I have decided on the Lopi Large Flush Wood insert.

I have a few questions,

The chimney is in the middle of the house and seems to have a good draft when I put an incense on the hearth right outside the firebox. I was thinking about going with a 15ft Premium Smooth Wall Chimney Liner or the Smooth Wall Flexible Flue Liner from Rockford chimney supply. Will these liners give me to much draft? Should I go for a corrugated one?

Also I was planning on insulating it with 1/2 inch of insulation. And talked with some installer who said it was not necessary. I don’t think I believe them as when I read NFPA 211 9.5.1.2 it says 1/2 in of insulation drops my clearances to combustion down to 6in, My assumption is the bricks in the current chimney would take up that space. But then I go to 7.2.2.3 and it says it’s up to the manufacturers instructions, which the manufacturer says is UL 1777 listed which is a testing specification and really doesn’t give me clearances, therefore I am back to my assumption of the bricks between the chimney giving me the correct clearances when insulated.

I feel like I am going too far down the code rabbit hole and would appreciate some insight.

Thanks

 

[begreen]

The assumptions are correct. Make sure the chimney is completely clean right down to the smokeshelf before starting with the liner install. And make sure the large insert will fit. This insert puts out a lot of heat. Is the fireplace in an open floorplan area? How many sq ft will be heated?

 

[stoveliker]

Good job with your code research!

Do get wood up so you can burn dry wood next season. Assuming you get fir, putting it up in early spring it should be good to go.

 

[Hunterfire]

The assumptions are correct. Make sure the chimney is completely clean right down to the smokeshelf before starting with the liner install. And make sure the large insert will fit. This insert puts out a lot of heat. Is the fireplace in an open floorplan area? How many sq ft will be heated?

The fireplace is huge 40”x27”x24”deep and I really want a large viewing area. I read the EPA reports and it seems like the lopi large is controllable for 11k Btu/hr to 40btu/hr. The house is 1660sq feet but my heat pump cold air return is luckily right above the fireplace. The heat pump is 30k btu so I think I would be able to make it work, by running the unit on fan mode only.



The room behind the fireplace (red box) has a 1500w space heater that can so so heat up the room so I figured I would be able to absorb that amount of heat, if I didn’t run the stove on a full load.

Do you think it would be to much?

Thanks

 

[stoveliker]

Be careful with a return near the fireplace; sucking air away from a fire is never a good idea. You could end up with a carbon monoxide distribution system...
If it's closer than 10 ft it's against code. I don't know if that's the case here

 

[Hunterfire]

Be careful with a return near the fireplace; sucking air away from a fire is never a good idea. You could end up with a carbon monoxide distribution system...
If it's closer than 10 ft it's against code. I don't know if that's the case here

Thank you for letting me know I had no idea that would be an issue, will look into it.

 

[stoveliker]

Also if ducts go through unconditioned space, it often doesn't work well to spread heat in the home. Ducts often have poor insulation and air sealing.

 

[begreen]

Yes, the heat loss through the ductwork may negate the gains. Looks like the return might be at the limit of the 10 ft requirement. There's nothing you can do about it at this point. An insert might be safer than the open fireplace in this case.

It's a small area. The medium sized Lopi would suffice.

 

[all night moe]

Why is there a cold air return up in the ceiling? Cold air falls, and heat rises in convection.
This looks more like a HO install than a professional HVAC installer. Just like my friend did in his house years ago.

I never thought about the carbon monoxide spreading until @stoveliker pointed this out very recently. My friend's place is within the 10' rule but he is also pulling from a cathedral ceiling. This may negate the 10' rule? Seems like It should not be practiced, period. The OP's pic also looks like the drawn air is from a collection ''alcove?"

 

[Hunterfire]

Why is there a cold air return up in the ceiling? Cold air falls, and heat rises in convection.
This looks more like a HO install than a professional HVAC installer. Just like my friend did in his house years ago.

I never thought about the carbon monoxide spreading until @stoveliker pointed this out very recently. My friend's place is within the 10' rule but he is also pulling from a cathedral ceiling. This may negate the 10' rule? Seems like It should not be practiced, period. The OP's pic also looks like the drawn air is from a collection ''alcove?"

The unit was put in 5 years ago by a professional HVAC installer. The house is slab on grade so that was the best of not ideal options. The ductwork is inside the thermal envelope of the building, as such it works well, it’s pretty frustrating this didn’t come up during the installation.

the house is a small and the medium sized Lopi would definitely suffice. The cost difference between the medium size and larger is negligible, in addition I would like the larger window to see the fire, but not if I would cook out the house. I was thinking about just use it with reduced amount of wood.

Or would I be cooking myself out?

Thanks

 

[stoveliker]

Do have a carbon monoxide detector up there, so that you get warned if there is any CO.

 

[Hunterfire]

The unit was put in 5 years ago by a professional HVAC installer. The house is slab on grade so that was the best of not ideal options. The ductwork is inside the thermal envelope of the building, as such it works well, it’s pretty frustrating this didn’t come up during the installation.

the house is a small and the medium sized Lopi would definitely suffice. The cost difference between the medium size and larger is negligible, in addition I would like the larger window to see the fire, but not if I would cook out the house. I was thinking about just use it with reduced amount of wood.

Thanks

Do have a carbon monoxide detector up there, so that you get warned if there is any CO.

I do have a carbon monoxide detector on the mantle. And after learning about this issue I will mount another one next to the inlet duct.

I’m also thinking i should add one to every bedroom.

I’m thinking about getting the low level CO detectors, although they are expensive, but this is not something I want to mess around with.

 

[stoveliker]

Our code requires detectors on each level and in all hallways in front of bedrooms.
But I don't have ducted air systems, so any CO would first be in the hallway before reaching a bedroom. That's what I have.
I did add two detectors, one near the stove (which is in the basement) and one at a place where any CO would have to travel past if it goes up the stairs to the living floor.

With issues like this, it's indeed better to be too safe than not safe enough, in my view.

I do have the standard detectors, except for the one near the stairs that has a level indicator with memory so I can see what the max level has been.

For the detector near the air return, I would either have a hard wired one, or one of those sealed 10 year versions - you don't want to end up not replacing a battery because your ladder is elsewhere...

 

[all night moe]

The unit was put in 5 years ago by a professional HVAC installer.

So he installed a hot air return.
I've been working on homes for 35 plus years. Not so much HVAC but, I know the components. A cold air return, placed up near the ceiling, is the first I have ever seen, and it's in your house.

Your heating system would be much more efficient if it were returning cool air instead of air that's already been warmed.

 

[stoveliker]

Unless the ducting was initially designed cooling system...?

 

[begreen]

So he installed a hot air return.
I've been working on homes for 35 plus years. Not so much HVAC but, I know the components. A cold air return, placed up near the ceiling, is the first I have ever seen, and it's in your house.

Your heating system would be much more efficient if it were returning cool air instead of air that's already been warmed.

I've seen this fairly frequently, especially with ranch homes on slabs in milder climates. It gets more common with heat pump systems that are doing double duty. More odd to me are the supply ducts in the ceiling. In some places you can feel the layer of cool air sitting about a foot or two above the slab while the room temp is 70.

 

[stoveliker]

We had both ceiling registers and floor registers delivering air in the ducted system in TN. Used both for heating and cooling.

 

[GG Woody]

I think it is a poor language choice to call it a cold air return, although lots of people do. It really is simply a return, sometimes you pull some return from wherever you can, beats a starving air handler or a frozen coil. In any plans, specifications, or shop drawings I've ever seen in the industry it is simply referred to as a return.
No big deal pulling air back to the air handler from up high.
Now if it was in a kitchen, bathroom, or laundry room, I would be more concerned.
It is very common around here to pull exhaust for HRV's from high up on the wall.
In this wood setup it might be ideal that the return is there. It could be a perfect spot to monitor gasses.

 

[EbS-P]

How often did you burn the fireplace? How much do you think you will use the insert? I ask just to offer different models that might be worth looking at.