Non-combustible hearth confusion

[CarbonNeutral]

I am buying a Jotul F500. In the manual for floor-covering it says this:

Floor protection under the stove must be constructed of a non-combustible material for protection from radiant heat, sparks, and embers.

Individual sections of floor protection must be mortared together to prevent sparks from falling through to combustible materials. Any carpeting must be removed from under the floor protection.

Then in Appendix A:

Alternate Floor Protection

All floor protection materials must be non-combustible ie. metal, brick, stone, mineral fiber boards). Any combustible material may not be used. The easiest means of determining if a proposed alternate floor material meets requirements listed in this manual is to follow this procedure.... continues with discussion about having an r-value hearth of 0.84

If this was a simple install, then I'd just go with some ceramic board, cement board and tile to make sure I meet the 0.84 value. However, as I'm rear venting the stove, I have very little leeway for raising the stove and still getting the vent under the fireplace lintel/bricks (the stove will not be in the fireplace). Therefore I'd rather go with just cement board and tile. Appendix A is only referenced in alcove situations (not my install).

Therefore I'm thinking I should be fine with just the cement/tiles......

 

[webbie]

You are correct in that it is confusing in the manual. You could read the first instance as allowing anything that was solid.

BUT, I think the .84 applies to a regular installation. This is expressed in the end of the manual under Alternate.....by "alternate" there, I think they mean other than a UL approved premanufacturered stove board.

It is confusing. That manual needs some work. The same page mentions 1.6 for alcoves and another page mentioned a bottom heat shield also for alcoves. All this info should be much clearer and in one place, IMHO.

A thin sheet of Micore would do the job. Maybe you can use one thin sheet of that with cement board to stiffen and then tile, etc.
https://www.hearth.com/econtent/index.php/articles/k_values_what_does_it_all_mean
https://www.hearth.com/econtent/index.php/wiki/Hearth_Design/

 

[firefighterjake]

Hmmm . . . if memory serves me correctly when I installed my Oslo it seemed as though there were no specific R value requirements for a hearth except in alcove installs . . . and at the time the general opinion of others (including Oslo owners) was that ember protection was all that was required . . . but being the anal retentive sort of person that I am I contacted Jotul and they verified that fact -- only alcove installs had a R value requirement, ember protection was fine for all other installs. Of course , that was last year, so perhaps things have changed.

If in doubt, contact your dealer . . . and if they don't know for sure have them contact Jotul to get you an answer.

That said, if possible I would recommend installing a hearth with some R value . . . regardless of what the dealership says . . . adding more R value can give you peace of mind and if you do elect to replace the stove with another one requiring a set R value there is a chance your existing hearth may have enough of a R value to allow a simple replacement without ripping it up and starting fresh.

Craig's link to the hearth design is quite useful for the R value chart.

 

[CarbonNeutral]

I will measure again and see if I can squeeze the 1/2 inch ceramic board in. Otherwise, upon confirmation from the dealer/Jotul I may have to go without it. Thanks for your responses.

 

[DAKSY]

Did you see if they had the short leg kit available in the color you want?
It'll reduce your flue collar height by 2-14"...

 

[CarbonNeutral]

Did you see if they had the short leg kit available in the color you want?
It'll reduce your flue collar height by 2-14"...

I know - you see I'm fussy - I want it all - I want the fire off the ground as much as possible, but also don't want to complicate the flue exit. I will look at them again though.Thanks.

 

[CarbonNeutral]

Actually, DAKSY is entirely correct, reduce by 2.25 inches, ensure I can get the stove under with no problem, and still have room for the 1/2 inch of ceramic board, fire is only 1.75 inches lower. Really, I can deal with this.

Hearth.com comes through again.

 

[begreen]

If you get this stove, don't hesitate to grumble loudly to Jotul about the confusion in the manual. Personally, I would contact them before buying. They have had this confusing hearth R-value issue for years in their manuals. It's time users called them on it and got a straight response that percolates into the documentation.

 

[CarbonNeutral]

If you get this stove, don't hesitate to grumble loudly to Jotul about the confusion in the manual. Personally, I would contact them before buying. They have had this confusing hearth R-value issue for years in their manuals. It's time users called them on it and got a straight response that percolates into the documentation.

I absolutely will - their website does not show any email addresses - anyone have an emails for both sales and marketing?

Literally three words added could clear this up entirely....

 

[begreen]

1-800-797-5912. Be patient, but persistent.