framing requirements for heat n glo northstar

[iron]

i'm planning to demo my existing fireplace this weekend and frame for the new one which will be installed next wedensday. i want to make sure i have my ducks in a row. i've chatted with my installer and we both think we have these items dialed in, but the installation manual is somewhat unclear on some items.

installation manual is here:
http://downloads.hearthnhome.com/installManuals/480_2360.pdf

1. on page 35, it says noncombustible framing materials must be used above the fireplace to a height of 84" or to the ceiling from the base of the fireplace for all construction materials, framing members, sheeting, and all finish materials. i assume this is only for the mantel and anything that comes off the wall. however, the 84" is confusing because i know it says the combustible mantel should be a minimum of 60" above the base of the fireplace.

my understanding is that this is for materials outside of the fireplace (i.e. protrusions). is this your take? or, for all my studs, headers, etc within my wall chase, do i need to use metal studs?

2. i am planning to elevate the fireplace approximately 5" off the subfloor to achieve a hearth height we're okay with (would like to go higher, but then the wood mantel is way too high as it needs to be 60" clear from the base of the fireplace unit). i have read nothing in the manual that suggests i need to use a non-combustible material for this. i was planning to use some 2x wood material. maybe i'll toss some cement board on top of it for extra piece of mind. any concerns with this or advice on a better way to frame this in?

3. on page 12, in the table, it says that faceplate to sidewall minimum distance is 16". i understand this to be the distance between my fireplace and drywall. we plan to finish the wall with some eldorado stone, full wall height (8ft) and probably 16-18" wider than the sides of the fireplace. since we're using stone, i will be putting in cement board, which i assume will satisfy this requirement. thoughts?

4. the installation manual also discusses insulating the chase. i'm not sure what's up in the chase right now as i don't have it opened up. if it's not insulated, what is your take on whether i should do this or not? see attached photo for the layout of our house. fireplace is going on the main floor by the 3 large windows. the pipe will be SL300 per manufacturer's requirements.

thanks

 

[DAKSY]

or, for all my studs, headers, etc within my wall chase, do i need to use metal studs?

Framing materials ABOVE the unit must be non-combustible. All of the wall up to 84" from the base of the unit must be metal studs & dura rock or hardie backer or something similar.

i was planning to use some 2x wood material. maybe i'll toss some cement board on top of it for extra piece of mind. any concerns with this or advice on a better way to frame this in?

You can build a box out of 2x's with 1/2" cdx on top to support the unit.

on page 12, in the table, it says that faceplate to sidewall minimum distance is 16".

That distance is to the nearest wall which is PERPENDICULAR to the wall the unit is installed in...

the installation manual also discusses insulating the chase

You want the enclosure around the unit to be as airtight as possible. Insulate the framing studs it with Kraft-faced fiberglass of whatever the max R value you can get. Then install 1/2" drywall & seal the seams with caulk or aluminum tape. Run the drywall up about 6 feet & build yourself a deck at that level, leaving an opening for the SL Series venting system. You should install the CAK & seal THAT to the pipe & the top of the unit with aluminum tape. Lay unfaced batts of fiberglass on top of that deck for added warmth, maintaining 2" clearance to the SL. One other thing that isn't noted in the framing instructions is that the chase needs to be a MINIMUM of 6 FEET wide INSIDE. You need this width to be able to install the outside combustion air kit.

Hope this helps. I have installed a dozen of these bad boys & one other thing I can add is that 450 pounds dropped on your fingers makes you say bad words...

 

[iron]

bob,

thanks for the detailed response.

i am very confused on this part:
Framing materials ABOVE the unit must be non-combustible. All of the wall up to 84" from the base of the unit must be metal studs & dura rock or hardie backer or something similar.

the reason is that in the installation manual, this is listed under the category mantel and wall projections (page 35). to me, this suggests that it only applies to things OUTSIDE of the fireplace box area.

for example, page 11: You must comply with all minimum air space clearances to combustibles as specified in Figure 3.2. Do NOT pack required air spaces with insulation or other materials. Framing or finishing material used on the front of, or in front of, the fireplace closer than the minimums listed must be constucted entirely of non-combustible materials (i.e., steel studs, concrete board, etc.).

another example, page 14: Figure 3.3 shows a typical framing (using 2 x 4 lumber) of the fireplace, assuming combustible materials are used. All required clearances to combustibles around the fireplace must be adhered to.

^ on that page 14 example, it clearly shows wood 2x4s immediately above the fireplace with a clearance = 0" per the table on page 12.


will insulating the chase improve the burning performance of the fireplace? i believe the chase is 6ft wide, so i should be okay there. what happens if it's smaller?

 

[DAKSY]

OK. We used metal studs in the wall flush with the front of the unit, but I can see that it is not necessary, according to the installation instructions. When I was installing in the early 2000s, this unit was new to the market & we went the extra step "JUST IN CASE."
The insulated chase does NOT help the unit burn better, but if you don't insulate & seal that envelope around the unit,
you will feel cold air movement (ie drafts) when the Northstar isn't burning. Your chase is actually OUTSIDE of the heated house envelope, so the unit's in the cold. The air convection thru the heat exchanger will reverse directions when the warm air in the room hits the cold metal firebox, & come out of the bottom of the unit as a cold draft.

If you don't have 6 feet within the chase I gets really difficult to install the outside air, unless you use a modified air box that has a low profile. I posted a rough pic of that low profile box in a previous Northstar post, but I haven't looked for it.

 

[iron]

bob,

2 more questions if you don't mind:

1. i am planning to have my installers locate the OAK below the fireplace by approximately 4ft. the reason for this is to eliminate the cold air intrusion that you referred to with the uninsulated chase. do you think this will address that issue since cold air is not going to travel UP the OAK?

2. for our mantel, we plan to use our existing doug fir piece that we really like. we'll keep the 60" clear from bottom of fireplace to bottom of mantel. however, we're thinking that we'd like to use doug fir corbels instead of stone corbels. if these wood corbels are spaced such that they are not directly above the fireplace (i.e. draw lines up from the edge of the fireplace and make sure the corbels are not within the lines), does the 60" clear requirement still apply?

thanks

 

[DAKSY]

bob,

2 more questions if you don't mind:

1. i am planning to have my installers locate the OAK below the fireplace by approximately 4ft. the reason for this is to eliminate the cold air intrusion that you referred to with the uninsulated chase. do you think this will address that issue since cold air is not going to travel UP the OAK?

It may do well in getting the necessary combustion air to the fire, but if you don't insulate the CRAP out of the envelope around & over the firebox, you are gonna be more than a little upset with the cold drafts from the unit itself. I installed here in upstate NY, where we get awfully cold & we tried just about everything to mitigate the effect created by that metal box in an unheated envrionment. Insulation & sealing the drywall with caulk or aluminum tape was the only answer. Do it while you have the chase open. You (& your family) will be glad you did.

2. for our mantel, we plan to use our existing doug fir piece that we really like. we'll keep the 60" clear from bottom of fireplace to bottom of mantel. however, we're thinking that we'd like to use doug fir corbels instead of stone corbels. if these wood corbels are spaced such that they are not directly above the fireplace (i.e. draw lines up from the edge of the fireplace and make sure the corbels are not within the lines), does the 60" clear requirement still apply?

If you are going to use combustible corbeils under the mantle, they cannot be within the outer edges of the non-combustible boards supplied with your Northstar. They can abut the outermost dimension, but they cannot cover any of it.

 

[iron]

ok.

i know with the existing ZC unit that's in the wall, there is little to no draft coming in. i think there's an OAK with that unit, but i'm not sure since i haven't looked too closely.

i'm not sure what the outer edges of the non-combustible boards supplied with your Northstar are. is my attached sketch accurate?

 

[DAKSY]

ok.

i know with the existing ZC unit that's in the wall, there is little to no draft coming in. i think there's an OAK with that unit, but i'm not sure since i haven't looked too closely.

You are missing my point. The OAK is not the concern.
The idea of the insulated airtight space around the METAL unit is
to keep that unit as warm as possible when there is NO FIRE burning.
A cold firebox will allow for warm air to enter the opening at the top - where the warm air is blown out during a burn.
The warm air will become cooled by the box & drop down the back of the unit & exit the INTAKE vents, creating a cold draft.


i'm not sure what the outer edges of the non-combustible boards supplied with your Northstar are. is my attached sketch accurate?

See page 55 of the manual - figure 10-2 for the non-combustible boards.

 

[iron]

my manual (downloaded online from their site) goes only to page 44.

is it this image, from page 15?

 

[DAKSY]

This page...

 

[iron]

thanks bob.

so, comparing my image from page 15 of my manual vs. your excerpt on page 55 of your manual, it seems they are more or less the same. the image on page 15 seems to be more conservative (i.e. farther from the heat) than the page 55 side pieces, so as long as i'm outside of that, i should be good.

 

[DAKSY]

thanks bob.

so, comparing my image from page 15 of my manual vs. your excerpt on page 55 of your manual, it seems they are more or less the same. the image on page 15 seems to be more conservative (i.e. farther from the heat) than the page 55 side pieces, so as long as i'm outside of that, i should be good.

Yessir.

 

[iron]

i just got done demoing the existing ZC fireplace. pain in the butt!

anyway, i see if have two existing 6" vents in the wall in the attached picture. do i need both of these for the OAK? or, will one suffice and can i abandon the other one? any thoughts on the best way to abandon the one? seems like i would want to cut it flush and seal with some spray foam to prevent outside air from hitting the drywall and insulation i plan to install tomorrow.

also, if i use one of these existing ducts for the OAK, which should it be?

lastly, will i have cold air intrusion with the OAK above my fireplace elevation?

thanks

 

[DAKSY]

Use the one on the right if you can.
That's the side that the OAK attaches to the Northstar.
How wide is the inside of that old chase?
Like I said, 6 FEET is the ideal opening it, regardless of what the manual says.
As far as repairing the rear hole, remove ALL of the ducting & the hood.
Make a plywood plug for the sheathing & attach to a cross brace.
You might want to add some plastic sheet to seal it against the elements,
inside & out. Matching the vinyl siding might be the tough part.
It will have fade from the sunlight.

 

[iron]

there's 6ft in the chase. however, the position of the new unit will be offset within the chase given the framing in the living room. there's another fireplace downstairs and the flue runs up just out of site. planning to demo that today. i'm not going to worry too much about the outside siding. it's hardiplank, and very shaded. no one sees that side of the house so i'll just leave the vent in there.

 

[iron]

now that i look more closely at my chase, i really don't want to go the drywall option if i can help it. there are a lot of pieces of x-bracing i would need to remove and reinstall, and of course, space is tight in there.

would it be acceptable to simply insulate and put in a 6mil vapor barrier? or would that cause issues?

 

[iron]

bob,

last question. thanks again for all your help. you can ignore my last ?s about drywall vs poly. i am drywalling it.

i see the fireplace comes with an override switch and speed control for the fan. i'm not sure if this is provided with the unit, or just something you get after the fact. anyway, i was wondering if it would be possible to operate both the override and fan speed control using something like this:
http://www.homedepot.com/p/Lutron-T...3-Way-Eco-Dimmer-White-TG-603PGH-WH/100663449

i'd much rather have a single switch in the wall if possible. thanks so much for your help!

 

[wantolearn]

Iron,
We are constructing a new house and are finalizing on buying the Northstar for our fireplace. Since you recently installed this unit, I have some follow-up questions for you:.
- Are you happy with this unit? anything you don't like?
- I am trying to understand the framing requirements and like you am confused about the framing vs. the mantel requirements (your bullet 1 in post above). Did you end up using lumber or metal studs for the framing of your entire chase.
- What about your raised hearth? what material did you use?
- could you share photos of your finished FP?

Will appreciate your response,
cmg

 

[iron]

here you go:
https://www.hearth.com/talk/threads...t-n-glo-northstar-fireplace-with-pics.149631/

the only thing i do not like is the black spots on the glass when the fire's burning low and slow. could be poor wood for me, but others have also had this issue. there are some rivets that pass through the air wash zone on the glass, so you get some vortex shedding issues there. i need to call heat n glo to discuss this with them (it's been a to-do thing in my email for a few weeks).

for framing, see the pic below.

when you figure out what height you want the fireplace (based on your desired hearth height), you build a platform to sit on your subfloor. i had mistakenly framed in the entire opening minus the spot for the fireplace, but that limited access to work behind the wall. so, i ripped out the studs above the fireplace, and the installers put in the fireplace and all the vent. when they were done, i framed the opening closed and drywalled. the mason did a scratch coat and and then rocked over it, full height of the wall (8ft)

i think the full height looks nice. it does, however, seem to heat up the roof a little bit, so in a cold climate, this could be an issue with ice dams (but i'm not sure on this). i know when it's cold and clear here and the roof is all frosted over, there'll be one spot right where the masonry touches the ceiling that the roof will be frost-free and melted.

for the mantel, i did 60" from the base of the fireplace. i think i set the fireplace on a 4.5" deep base, so that put us at 64.5" to the base of the mantel. initially, we thought it might be too high, but it looks fine. based on the heat the fireplace puts out, i wouldn't want it any closer! one piece of caution i would add here: if your mantel materials are not bone dry, they will shrink after you use your fireplace. i made new corbels for ours using a 6x12 doug fir beam. the mantel itself was reused from the previous fireplace. the mantel didn't shrink, but the corbels have probably 1/4" of contraction and have warped a bit about the rings. no one will notice this but me, but just a heads up. i will need to grout the lines where the gap has formed eventually.

let me know if you have any other ?s.

 

[wantolearn]

Thank you for a prompt reply. I did find your post with photos soon after I asked the question. Very helpful post to us newbies. I am sure I will have more questions as we embark on it soon.

 

[mminor]

CMG - did you decide on and purchase the Northstar? How is your installation going?

Thanks,
Matt

 

[wantolearn]

Matt, not yet. Still getting quotes. We have very few dealers around here and so they have somewhat of a monopoly. So still working on finalizing.