Radiant slab walk in basment

Unknown

CC with good flow balancing is pretty hard to go wrong with, for sure.

Normally I wouldn't do separate zones in open areas, but sometimes, on larger slabs such as this, it's warranted.

Bernie Riddle_2

Entrance doors

I have a 1500sq ft radiant slab that is 1 zone with 5 300 ft loops of 1/2 pex. It is all above ground and the front right corner has two entrance doors and the concrete is exposed to the outside underneath and on the edges. The slab temps around the entrances are always in the 50s compared to the rest of the slab. The very first loop runs right past both the doors. Would it be advantageous to try and run higher temps in this loop? Thinking maybe if this area was drawing alot of temp out of the slab maybe it should be kept warmer then the rest?

I guess what needs to be done is the ground under and around each entrance should be dug up and some sort of insulation applied but I would not know what....

Anyone ever deal with something like this?

Unknown

is the cold area on its own loop?

are you sure that loop is getting flow?

Barry_6

Dan H has a great book called, interestingly enough, Hydronic Radiant Heating. On page 100 he discusses slab insulation. There is a tremendous loss from the heated slab down into the earth and especially at the perimeter of the slab. That's because the greater the temperature differential the greater the movement of heat from hot to cold. Dan suggests using 2" polystyrene around the perimeter from the top of the slab to below the frost line. I've had good results using tongue and groove extruded polystyrene (slightly higher R value). You need to apply some mechanical and ultraviolet protection to the exposed areas. I used fiberglass matting with a trowel-on pre-mixed epoxy compound (don't recall the name or brand - someone else may be able to help)

Bernie Riddle_2

The entire slab is one zone and the first loop runs right past both entrances Rob. I posted a pic of the layout. I shut off the other 4 loops last night and run 115 degree water through it for a couple hours and got that area up to 74 in spots but there were still cold spots in it. Its definately circulating. This morning I did try restricting the flow of the inner loops to get more hot water through that cold loop and it seemed to help.

I guess maybe you could remove that loop and put it on its own zone with a higher temp to compensate or something....I dont know....I know the whole concept of a radiant slab with a wall thermostat seems counter productive to me. Between the call for heat the slab has too much time to cool down and I loose alot of heat in that area from what I can tell.

I need a constant circualtion setup that monitors slab temp or return temps and keeps the floor constant IMO.

Unknown

Balance

DC,

Keep the flow greater in the loop toward the outside and reduce the flows on the consecutice loops.

YOu should find that in time, if you take the time to balnce correctly, you will have an even temp on the slab.

STeve

Bernie Riddle_2

Can the taco RMB-1 mixing block

Be used for constant circualtion?

I would get the outdoor reset, and the ability to mix according to the return water temps right?

Mark Biro

You CAN retrofit edge insulation around slab

You can retrofit insulation around a slab. It DOES take time. (Doh!) I have done it... pick a nice day... days, actually, and do a bit at a time. say 8 feet, the length of a sheet of extruded (pink, blue...) foam.

My attitude was that ANYTHING (any depth) is better than the current nothing. So You might aim for 16 inches, or 1/3 the width of a sheet. Eager beaver? Aim for 2 feet. :-)

Tip: find or buy a trenching shovel, with the narrowest and longest blade you can find: move as little dirt as possible (say a 4 inch wide blade), and save your back.

Darrell

If you're really into fiddleing with your floor and can control the supply temp manually try lowering the temp five degrees or so...a little is a lot in a floor...the lower supply temp will force the zone to be active longer, (kind of a chinsy way to get near constant circualtion), and even out the heat distribution. This is a straw to be grasped at, and getting right down to sqeak as they say. Said another way, the floor heating system is room thermostat driven...the stat will call until it gets satisfied, and a lower supply temp takes longer to change the room temp and satisfy the stat.

Even at a lower supply temp, the floor temp that your feet feels will be the same...'cuz that is the surface temp required to heat the space. Ideally, you want to supply the lowest possible temp to heat the space comfortably.

But, do plan to insulate the perimeter.

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Darrell

If you're really into fiddleing with your floor and can control the supply temp manually try lowering the temp five degrees or so...a little is a lot in a floor...the lower supply temp will force the zone to be active longer, (kind of a chinsy way to get near constant circualtion), and even out the heat distribution. This is a straw to be grasped at, and getting right down to sqeak as they say. Said another way, the floor heating system is room thermostat driven...the stat will call until it gets satisfied, and a lower supply temp takes longer to change the room temp and satisfy the stat.

Even at a lower supply temp, the floor temp that your feet feels will be the same...'cuz that is the surface temp required to heat the space. Ideally, you want to supply the lowest possible temp to heat the space comfortably.

But, do plan to insulate the perimeter.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"