Heat Loss & (mk)

Mike Kraft

I am doing a very small addition.It is a weight and exercise room.The room was a porch so it has 3 outside walls,two doors,glass on all three,R-30 up and R-35 down(exposed,cantalevered).The question I have is when using panels do you design with less infiltration because of the emitters being radiant?I have always gone with IBR defaults and havent been bit.

Also the HO is trying to cram his equipment in this space and I suggested installing the panel/s on the ceiling.He likes it but wants to hang one large panel on the only inside wall.......@ 7' off the floor.I am a bit leary even though we all know a BTU is a BTU.

Thanks,

cheese

hot_rod

another thought

why not go with radiant ceilings? If the room is emcumbered with equipment use the ceiling either as the main heat or supplemental. Might look better than a panel radiat application.

ThermoFin just below the sheetrock would be a powerful system. You can run sheetrock up near 120 F. Much more output than a 82 F floor.

What do the heatloss calcs tell you for loads? Got enough floor to get you there? Heat from top and bottom would be hard to beat. Maybe two stage it with floor then ceiling as second stage.

hot rod

Mike Kraft

Thanks Hot Rod

I dont have enough floor and made the exact suggestions you did.When covering all the options the HO seems to want the panel.I have the same opinion as yours and may still convince him.

cheese

ScottMP

Mike

I have also used the Buderus panels and not been bit using there numbers.

I did'nt find anything in the Buderus Literature that shows a breakdown of what percentage is radiant as compared to convection. After seeing a post a few months ago about how much a cast iron radiator actually "radiant", I would be cautious. I think the radiant output may be optimistic at best. I'll stick to the convection and sell the radiant as a extra benifit.

I like HR's idea. Having the cieling as the 2nd stage is pretty cool. I try and remember that the floor is not the only place for radiant. It tough, it so stuck in my mind that it belongs on the floor.

Scott

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[Deleted User]

Buderus radiant output

I've been told by person s I trust that 60% radaint, 40% convective. I've also seen reports claiming 50/50.

If its on the ceiling it is 100% radiant.

ME

Eric Taylor_27

been investigitin' this

I've been brushing up on my heat transfer a bit and trying to sort this out for myself. What I have found supports 60/40 and 50/50 (rad/conv) depending on ambient conditions and emmitter temp. This is for vertical flat plates ONLY, and I stress FLAT. Those ratios are per unit area though! The panel rad hung on the wall has half of the total area spaced close to the wall. It can still convect because of the gap, but all radiation on that side is absorbed by the wall and never "sees" the room as radiation. So if we assume that the ratio is 50/50 but the back can't radiate into the space then we have 33/66 rad/conv. This isn't the whole answer though because the wall behind the panel gets a little warm from that radiation and does some convecting too (it can't radiate cuz the panel is in the way). If we assume the wall is perfectly insulated and all of the radiant energy it absorbes is returned to the space as convection then we have 25/75 rad/conv. We know some heat gets lost through the wall though, so a good guess for panel rads hung on the wall could be 29/71 or 30/70 for simplicity. Hang that sucker in the center of the room and 50/50 is true, but I doubt that you will get the job!

Tube or collums rads are a whole different animal compared to the panel rad. The panel rad hung in the center of the space can both convect and radiate from 100% of it's surface area. Put it 2" from the wall and 100% of the area can still convect, but only 50% can radiate. Standing iron has the majority of the surface area occluded by other area (the sections only "see" other sections) and can't radiate into the space. All of the area can and does convect though. Figuring out exactly how much area "sees" the space and can therefore radiate is way beyond my capabilities but I'd be very suprised if it were more than 20% with the rad up against a wall. IF I am right, and thats a big if, then about 16.6% of the heat output from standing iron is radiation. Again, the hardest part is figuring out how much surface area "sees" the room.

The clincher is that my textbook refers to cast iron radiators as "convectors" several places.

Eric

Mark A. Custis

Cheese:

How do you think this stuff up?

I have nothing to add to the best minds in the bussiness, EXCEPT, If you or I were lifting weights, working out, moving very large and heavy things against the natural flow of gravity, what would be the comfort setting on our t-stats? I was on a rooftop at 60* & sunney, but cooler by the lake. Frozen solid.

Hi Mike just a pinch,

Mark

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