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Old 09-15-16, 09:32 AM   #21
stevehull
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Wizard,

Here is the logical behind my apparent illogical statement . . .

For a floor to feel like it is "heated", the floor must be about 80 F at a minimum. This temperature cancels out the conductive cold perception of a bare, no carpet floor (such as concrete, or ceramic tile/plank).

Conduction plays a large role in cool/warmth perception. For example, if you put your hand on a steel plate that is 85 F, the steel plate will "feel" cold. Your hand on a similar temp piece of wood will not "feel" cold. Same temperature - different perception of temperatures.

If we do this thermal floor, we will embed PEX pipe in two inches of concrete (on top of foam boards) and then put down a hard flooring material over that (ceramic planks or laminate). Ceramic has a lot of conduction, so even an 80 F floor will feel "coolish" to bare feet - but FAR better than a 65 F floor!

Laminate is not as great a heat conductor as ceramic (or concrete) so it "feels" a bit warmer, but not as warm as a true wood floor. I have had wood floors in the past and I am so tired of getting them refurnished every couple years. We have big dogs and, in spite of multiple coats of hard polyurethane, you can still soon see the wear marks in the pattern of where the dogs come in and out. The last flooring company "guaranteed" their finish for ten years - it lasted three. Turns out, they guarantee the material, not the labor. Tired of all the dust the sanding causes.

Make no mistake, a wood floor is beautiful. Just tired of the upkeep.

Does my logic on "warmth" reveal itself now?

Steve

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Old 09-15-16, 09:52 AM   #22
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I work in commercial HVAC. We had a job were the engineer spec's the in floor heat built with 6 inches of sand between the insulation and concrete. So it was 2 inch foam, re-mesh, pex, 6 inches of sand, 4 inches of concrete.

Because sand is a poor conductor of heat, the heat from the pex rose through the sand and little was conducted down to the insulation.

I like that design.
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Old 09-15-16, 09:57 AM   #23
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OK, so with a fairly even split between forced air and radiant in heating mode, you should be able to use the waste water from an air handler coil to heat your bathroom floors. This would alleviate a lot of the design concerns you have. Regardless, with a smaller than usual heat load, you won't need a huge slab to hold the BTUS.
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Old 09-15-16, 01:20 PM   #24
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Steve - I think the dogs will scratch up the laminate also. It might take them longer, but ...

You sound like a well informed individual, so I guess I really can not question your 80+F statement for a "warm floor", but that still sounds quite high.

If you don't want the thermal mass, why are you putting in concrete ? I assume you are going to use a light weight, self leveling type of concrete. With that type of product, you only need it thick enough to cover the PEX so it would be closer to 1".

If this is on top of a wood framed subfloor, you should double check the framing underneath and check the subfloor for level. The self-leveling stuff really works, but if you have low spots it will be very thick and will take longer to cure. High spot are worse, because more product has to be add to the whole area.
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Old 09-15-16, 02:10 PM   #25
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all right steve, lets take this from another angle. What is your energy budget? Do you want to eventually go net-zero? It seems to me that is going to be the decision point. If net zero is more important to you than warm floors, then the warm floors are probably a waste of money. same with going extreme energy efficiency...

That said you don't have to go gonzo with insulation and if you have clerestory windows you can use those to control some extra stack driven exfiltration to deal with overheating issues from a well air sealed house. you are just going to pay an energy penalty for that.
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Old 09-18-16, 04:40 PM   #26
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It is claimed that "Luxury" vinyl is pet friendly. It has low conductivity compared with other hard surfaces, so it might feel a little less cold if you decide to go without sub-floor heat. Still cold compared to carpet though.

Do you clip your dogs' nails? That might solve one of your problems. We never did but the wear of one dog was negligible by comparison with 9 kids.

Have you considered radiant ceilings? They can heat the floor by radiation and are also good with a low-conductivity floor covering. For a new build it seems to be worth consideration. This is theory only: I'd make up metal suspended heating panels rather than try to drive the heat through a conventional ceiling, which should allow a lower water temperature.

Radiant ceilings can also be very effective for cooling, but only if the internal humidity is kept low, or you would get condensation on the ceiling.
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Old 09-18-16, 06:02 PM   #27
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We do clip the dog's nails - the problem is the very hard and sharp grained quartzite sand in the local Oklahoma soils. The dogs go out and get it on their paws and then track it in - even though we have thick lawns and pastures everywhere. They dig . . . Doesn't help that they are big dogs as well.

A local friend, with similar size dogs and problem, uses commercial laminate and apparently this is a hard surface compared to wood floor finishes. No wear at all despite they have more dogs than we have, You are also correct that the so called luxury vinyl tile will work.

Wife really likes the newer ceramic planks - some of which look like wood - and those are also very hard. But that surface has high conductivity and can "feel" cold if not heated to high 70's to 80 F. Then problem of overheating air.

I have seen radiant walls and ceilings - in Europe. Floors make sense as was planning a thin concrete slab floor anyway.

In one home that I have visited (in a slightly colder winter than here) observes that the IR effect of a conditioned floor (72-73 F) is such that you can lower air temp to mid 60's F without feeling cold. I would agree as I never felt cold in that house. Talked to them this weekend and they agree that an air temp of 72 would "feel" way too hot in the winter. I hadn't realized that the air thermostat was set to mid 60's in that house.

In winters, we have very dry air and wife will complain that house "feels cold" unless the air thermostat is 73. This is largely due to the dry air. We do run a humidifier, as many people in Oklahoma do.

Got into trouble a few years ago when I "adjusted/tweaked " thermostat display to read 72 F when in reality it was set to 70 F. Wife brought home a temperature gauge and discovered that house was actually 70 F. So she then made me set the damn thermostat at 74 F. All my work/tweaking for nothing . . .

Has anyone used radiant flooring and then felt the need to lower the air temp to mid 60's F or so?


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Old 09-18-16, 11:39 PM   #28
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Hi Steve,

The benefits that you mention for radiant floors apply at least equally for ceilings. You say that the floor option makes sense as you were going to a concrete floor anyway. Since you are worried about having too much thermal mass, it would seem far more logical to eliminate the expensive, heavy concrete floor and go with the ceiling option, which has effectively no thermal mass, if you use a suspended metal radiator surface.

All solid, hard floors will feel colder than an air-containing material like carpet or cork, unless they are heated. Vinyl and wood are about 6 times lower in thermal conductivity than concrete or tiles however, I'm not sure if the difference would be noticeable. If you had ceiling radiant though, the very top surface of the flooring would heat up much more quickly with a low-conductivity material than the tiles would and this could become significant? Do you know anyone with a vinyl or wood bathroom floor who has heat lamps for bathroom heat to see how ceiling radiant would work?
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Old 09-18-16, 11:39 PM   #29
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Quote:
Originally Posted by stevehull View Post
Got into trouble a few years ago when I "adjusted/tweaked " thermostat display to read 72 F when in reality it was set to 70 F. Wife brought home a temperature gauge and discovered that house was actually 70 F. So she then made me set the damn thermostat at 74 F. All my work/tweaking for nothing . . .
Steve
Now that is funny!
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Old 09-19-16, 08:09 AM   #30
stevehull
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Quote:
Originally Posted by Snail View Post
Hi Steve,

The benefits that you mention for radiant floors apply at least equally for ceilings. You say that the floor option makes sense as you were going to a concrete floor anyway. Since you are worried about having too much thermal mass, it would seem far more logical to eliminate the expensive, heavy concrete floor and go with the ceiling option, which has effectively no thermal mass, if you use a suspended metal radiator surface.
Misunderstanding (of me explaining my situation). Thermal mass is good - up to a point. The key is to match the time lag/storage with the climate it is being placed in as well as the energy costs.

A heated four inch (10 cm) floor, throughout the home, may be simply too much mass for the climate here in Oklahoma. The problem is that we have a mild winter associated with a large rise in daily temperatures from nightime lows. In a colder climate, this mass volume could be perfect.

For compromise, a two inch floor might allow the right amount of heat storage without the long lag. If the time constant for heat loss is long, then you can end up releasing heat in the middle of the next daytime (overdamped).

Too short a time constant and the house temperature goes up and down (underdamped). Much like an impulse to a car shock absorber, the dampening must be correct.

I am running some models now, but it "looks" like two inches is about right for my mild winters and significant daily temperature rise (20-30 degrees F).

This article talks about time dependent thermal dampening concept . . .

Thermal Mass - Energy Efficiency of Concrete


Steve

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