Does "Air" have an "R" value?
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a ventilated air space is "R-1.43 per inch"
however you cannot count that as "R towards floor protection as it would have already been factored in during testing when determining what the R factor of the floor protector would be
however you cannot count that as "R towards floor protection as it would have already been factored in during testing when determining what the R factor of the floor protector would be
So does that mean I can put a 2" lift kit under my 30, and be all good?
ibThat'snothowitworks
So does that mean I can put a 2" lift kit under my 30, and be all good?
ibThat'snothowitworks
uh, no, but if you had a non combustible surface lifted up with a ventilated air space beneath it you could do just that (i wouldnt want to but it would be feasible)
the air space between the stove floor and the floor underneath has no radiant barrier (a surface to capture the radiant heat) so it had such a barrier and the air was circulated under that barrier then the result would be the same as having an actual insulating material under that barrier.
All this being said if a stove is on four pedestal legs and requires an R value of 1.0 (for talking purposes) and you cut the legs down to get the stove to fit a certain application does this mean that the stove could possibly require a different R value now because of the alteration?
Yes, though it's anyone's guess. At the point the stove is no longer working within the UL certification.
BG is correct , any UL listed product only carries the listing if it is not altered, so any modification voids the listing. as for cutting down the legs this puts the firebox closer to the ground and would alter the amount of radiated heat between the box and the floor below it. as for how much , there's really not a "standard formula" one could apply that would be the same for every stove due to differences in design of the stove itself. technically one would have to revert to the NFPA 211 standard in the case of a modified unit in order to meet code at least by "the letter of the law" so to speak.
The funny thing is that at least the 2003 NFPA 211 does not state any r-value for floor protection:
"12.5.1.2 Room Heaters, Fireplace Stoves, Room Heater/
Fireplace Stove Combinations, and Ranges.
12.5.1.2.1
Room heaters, fireplace stoves, room heater/
fireplace stove combinations, or ranges that are set on legs or
pedestals that provide not less than 6 in. (152 mm) of ventilated
open space beneath the fire chamber or base of the appliance
shall be permitted to be placed on floors of combustible con-
struction, provided the following conditions exist:
(1) The floor under the appliance is protected with closely
spaced solid masonry units not less than 2 in. (51 mm) in
thickness.
(2) The top surface of the masonry is covered with sheet
metal not less than 24 gauge [0.024 in. (0.61 mm)].
(3) The floor protection extends not less than 18 in.
(457 mm) beyond the appliance on all sides.
12.5.1.2.2
Room heaters, fireplace stoves, room heater/
fireplace stove combinations, or ranges that are set on legs or
pedestals providing 2 in. to 6 in. (51 mm to 152 mm) of ventilated
open space beneath the fire chamber or base of the appliance
shall be permitted to be placed on floors of combustible con-
struction, provided the following conditions exist:
(1) The floor under the appliance is protected with one course
of hollow masonry units not less than 4 in. (102 mm) in
nominal thickness.
(2) The masonry units are laid with ends unsealed and joints
matched in such a way as to provide free circulation of air
through the core spaces of the masonry.
(3) The top surface of the masonry is covered with sheet
metal not less than 24 gauge [0.024 in. (0.61 mm)]."
And looking at 2.1.(1), a hearth of one layer of bricks with some sheet metal on top would be enough to meet the 13NC or 30NC hearth requirements although it would fall short of the required r-value stated in the manual. Now, I am sure the manual supersedes the NFPA 211 but when someone would cut down the legs and then follows NFPA 211 they would actually need less of an r-value. I am curious what a building inspector would say to that when he/she usually follows NFPA 211 for his/her decisions regarding code compliance.
"12.5.1.2 Room Heaters, Fireplace Stoves, Room Heater/
Fireplace Stove Combinations, and Ranges.
12.5.1.2.1
Room heaters, fireplace stoves, room heater/
fireplace stove combinations, or ranges that are set on legs or
pedestals that provide not less than 6 in. (152 mm) of ventilated
open space beneath the fire chamber or base of the appliance
shall be permitted to be placed on floors of combustible con-
struction, provided the following conditions exist:
(1) The floor under the appliance is protected with closely
spaced solid masonry units not less than 2 in. (51 mm) in
thickness.
(2) The top surface of the masonry is covered with sheet
metal not less than 24 gauge [0.024 in. (0.61 mm)].
(3) The floor protection extends not less than 18 in.
(457 mm) beyond the appliance on all sides.
12.5.1.2.2
Room heaters, fireplace stoves, room heater/
fireplace stove combinations, or ranges that are set on legs or
pedestals providing 2 in. to 6 in. (51 mm to 152 mm) of ventilated
open space beneath the fire chamber or base of the appliance
shall be permitted to be placed on floors of combustible con-
struction, provided the following conditions exist:
(1) The floor under the appliance is protected with one course
of hollow masonry units not less than 4 in. (102 mm) in
nominal thickness.
(2) The masonry units are laid with ends unsealed and joints
matched in such a way as to provide free circulation of air
through the core spaces of the masonry.
(3) The top surface of the masonry is covered with sheet
metal not less than 24 gauge [0.024 in. (0.61 mm)]."
And looking at 2.1.(1), a hearth of one layer of bricks with some sheet metal on top would be enough to meet the 13NC or 30NC hearth requirements although it would fall short of the required r-value stated in the manual. Now, I am sure the manual supersedes the NFPA 211 but when someone would cut down the legs and then follows NFPA 211 they would actually need less of an r-value. I am curious what a building inspector would say to that when he/she usually follows NFPA 211 for his/her decisions regarding code compliance.
from Grisu
And looking at 2.1.(1), a hearth of one layer of bricks with some sheet metal on top would be enough to meet the 13NC or 30NC hearth requirements although it would fall short of the required r-value stated in the manual. Now, I am sure the manual supersedes the NFPA 211 but when someone would cut down the legs and then follows NFPA 211 they would actually need less of an r-value. I am curious what a building inspector would say to that when he/she usually follows NFPA 211 for his/her decisions regarding code compliance.
i looked at my copy (2006 version) and its identical. i see youre point. it would probabaly be hard to reconcile this in my mind as well, of course the additional 36" all around and 18" floor protection all around would have to be followed as well
And looking at 2.1.(1), a hearth of one layer of bricks with some sheet metal on top would be enough to meet the 13NC or 30NC hearth requirements although it would fall short of the required r-value stated in the manual. Now, I am sure the manual supersedes the NFPA 211 but when someone would cut down the legs and then follows NFPA 211 they would actually need less of an r-value. I am curious what a building inspector would say to that when he/she usually follows NFPA 211 for his/her decisions regarding code compliance.
i looked at my copy (2006 version) and its identical. i see youre point. it would probabaly be hard to reconcile this in my mind as well, of course the additional 36" all around and 18" floor protection all around would have to be followed as well
Yes, several of us have over the years. The temp varies with the stove design. If the pedestal or legs are low and there is no ashpan or bottom shield the hearth is going to be noticeably hotter when compared to a stove that has taller legs and an ashpan. Another variant is radiance. Some stove are highly radiant off their sides and others are not. The most radiant stove will have a higher hearth temp. That said it does seem like some stoves have seriously overrated hearth requirements. Not sure why. We just noted a case where the requirement for the medium sized Pleasant Hearth more than doubled over just a couple years for some reason. Model number for the stove is the same so one has to wonder what happened to bring about such a radical increase in the hearth insulation requirement.
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