What if?

Unknown

Interesting point rob.

I'm fascinated by "natural feedback".

The opposite sort of feedback from the one you describe is illustrated in the polar melting trend. As the poles melt the reflective area is diminished and energy absorbing open ocean is exposed, reinforcing feedback, as opposed to a negative feedback.

Is the volume of a space (high ceilings) as important with radiant heat? So much less stratification, do heat any loss programs take this into consideration?

Gene Davis_3

What if it struggles?

I am the GC (not the heating contractor, because we are in the bid stage) for the house with the too tall kitchen that does not have a good way to heat it. Not enough floor output for the underfloor tubing to deliver.

At least not at the design temp of -35F. We may be as much as 6000 Btu/h short.

But here is a thought. The kitchen is equipped with a very expensive little Belgian-made wood stove/oven (see the pic) capable of putting out three or four times the shortage.

Here is the question. What happens most of the time during the winter, when the temps are going to zero or a few below, and no one is there (it is a vacation home)?

And what about if someone is there, and the stove gets used, and the temps drop low?

[Deleted User]

You might be suprised...

Heat loss calculations are not a fine tuned science by any means. I've seen rooms that theoretically should NOT heat, heat just fine..

With that said, kitchens are a completely different beast. They generally have appliances that have a tendency to OVER heat the space. I have seen older kitchens where there was NO heat source in the kitchen, and they work just fine...

Sometimes, we have a tendency to get tied down by perfect numbers. There are a LOT of things that we do not take into consideration, that in a real time sence, make all the difference in the world.

You can figure out what will happen with the heat you have. (Theoretically...)

-35 degree F design conditions, where the heck is this home at? The North Pole?

ME

Gene Davis_3

I'm guessing

Location of the project is Lake Placid, NY. We'll get a few nights each winter with temps down below -35F.

Saranac Lake, NY, is 7 miles down the highway, and at least ten times each winter, shows the lowest winter temp in the lower 48. We are at elevation 2,000 feet here, with the highest peaks of the Adirondacks in sight to the east, and Whiteface mountain to the north, just at the other end of the lake.

Bismarck, ND, has a design winter temp of -30F. Maybe we should be designing for a temp like that, but I am not sure.

ALH_4

Bismarck

You could install a radiant ceiling in addition to the radiant floor.

Bismarck is cold, windy and very dry in the winter. It's a harsh climate where snow blows like sand.

Unknown

a "few nights" of -35 is not a -35 design temperature. at worst you should be using about -15, which is the coldest it gets anywhere near you (at a weather station) 99.6% of the time according to ASHRAE. the house mass allows a "coast" through shorter runs of colder weather, typically.

edit: at 2000 feet, maybe -20 or -25 if you want to be really, really conservative. I did miss the elevation at first though, sorry.

Gene Davis_3

OK, let's get back on topic

I now understand, a few extreme lows don't a 99 percent winter design temp make. We'll still have a prob in this kitchen with its ceiling vaulting from 9'6 over the sink to way up to 24'. Whole lotta air up there.

So, that settled, let's still presume the "underfloor radiator" can only deliver PART of the heat required to handle things when it gets bad, and that we are still a few thou short, with no place to do a radiator for supplement.

We'll ALWAYS have one, or two, or three week-long stretches in the winter when the daytime highs don't get above 10 F, and the nighttime lows dip to 10 below.

As I said, there is that $3500 Belgian wood-fired stove/oven, but to make that do anything for you, you gotta be there, and you gotta feed it wood.

What is the hydronic system doing, struggling with it, during those chilly times?

Unknown

If you're not there, I presume you are not maintaining a 70 degree room temperature, and I believe you won't be as short as you think you are. In any case, you're pretty unlikely to freeze. You could iteratively run the numbers to see where the "temperature balance" falls, but suffice to say, the very act of lowering your room temperature drives more heat through the floor, so beyond the fact that your heat load drops as the room cools down, the floor output rises as well.

So you'll be dumping some amount of heat that is more than the 70 degree room radiant available output number, and less than the heat load of the room at 70 degrees. and you'll achieve a balance point, probably at worst somewhere in the 50's. And if you set back your thermostats to 50, you'll be unlikely to notice a difference if that area is zoned on its own.

For reference at 50 degree room temperature, an 85 degree floor is putting out close to 70 BTUs/sq ft.

eluv8

not enough heat

I was wondering what they are using for countertops. I have seen a couple of neat jobs where they put a loop of tube under the counter and it heated nicely. quick trak and grantite or mud and tile come to mind.

Wayco Wayne_2

I love Saranac lake.............

in the Summer. -35 you must be kidding. Radiant floor plus radiant counter tops. Don't forget the refrig is pumping out heat. It will be influenced by the rooms around it. It won't freeze and if no one's there to feel it and fire up the wood stove you got no worries. I'll be camping near Saranac Lake in a State run campground called Rollin Pond, first week in Aug. Make sure the weathers nice for me please. Sweet! WW

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Unknown

height is generally only in the infiltration calculation and of course in the increased wall/window areas, for radiant calculations anyway.

the natural feedback in radiant is fairly strong, really. Every time your room temp drops a degree, you add 2 BTUs/sq ft and loses 2 when you rise 1. I need to whip up some "modelling" on that in my calculator, I have a feeling it would reduce our zone counts a little.