Radiant floor heating education ?

[eauzonedan]

Just a thought.... When I shot my buried pex run I didn't meet the minimum volume of foam and had them shoot the rim joists almost as an afterthought. One of my best choices. Drilled thru it for a dryer vent and ended up with core of foam. Simply amazing stuff and couldn't tell much difference from rigid foam in sheets. Ended up with 3+ inches and would recommend using plenty of depth. Additional benefit was no more mice or the damn lady bug beetles in the house. Really tightened up infiltration.

 

[Minnesota Marty]

Shoot if my wife's hears that the spray foam helps keep out the lady bugs in the fall.... she is going to be spraying everything. LOL

 

[arbutus]

Webie,

Check the Uponor Complete Design Assistance Manual pdf, page 224 (PDF page 232).
Top chart - Joist Heating, No Plates, 8" On Center

Figure 2 btu/hour for each degree in temperature difference.

Looks like you could get your floors ten or so degrees warmer with just pex and insulation with a water temperature of 170.
You might not have to mix the temperature down or buy plates.

I *assume* the second chart on that page is the thin aluminum double groove if you are interested in going that route and running slightly cooler water temperatures. I don't know if uneven heat stripes would be a factor or not.

 

[webie]

I been trying to look thru lots of this information and hopefully I been getting smarter . I would like to go with plates whos I dont know yet , because I am hopeing to be able to utilize lower water temps. The area that I want to do is an open concept and the other half is sucken living room which I will not be doing . I know The area I want to do will never have anything in other than vinyl .
I am not really sure what or how an outside reset works , also is there advantages or not to keeping the water circulating in the radiant loop at all times verses having it cycle ?
I have an advantage here as I am not dependant on this radiant to be the sole heating , If it is enough in the shoulder seasons thats great otherwise my baseboard does a fine job . I do want the floor to be warmed evenly though not cold here warm there .
Is there advantages or do I need to insulate the joists after I install the radiant or not , are there pros and cons ? I do put some heat in my basement now as I try to keep that in th middle 60's so some heat loss there isnt a big deal and I am thinking the majority of the heat will just stay in the joists bays .

 

[Seasoned Oak]

If im not mistaken most Mfgs suggest a water temp in the low 90s. Iv never heard of water temps in the Mid 100s for radiant floor heat. Not sure what kind of problems it would cause other than hardwood flooring drying and cracking to use a water temp too high. Also iv always read that insulation under the radiant heat is necessary.

 

[velvetfoot]

otherwise my baseboard does a fine job

Do you mind me asking what your basement setup is like? Is it normal high temp?

The stuff that I've been reading seems to indicate that insulation in the bays in desirable.

I have a Tekmar outdoor reset on my oil boiler. The warmer it is outside the lower the boiler supply temperature, within limits. Apparently it saves money. Not positive how this would work with storage and what advantages.

 

[webie]

I heat with a gasification boiler and storage . When boiler is running temps are upto 190 . When I am pulling off of storage I can go all the way down to what is needed so I could be down to 120 . My thoughts right now is just run a three way zone valve as its own zone so the radiant loop runs all the time with its own pump and then use a mixer set at 110 or what ever to mix down my supply temps so when there is a call for heat the valve opens and allows tempered water to enter the radiant loop . My basement is unfinished and the section where this is to be down probably will never be finished .

 

[webie]

How critical are the plates as I am seeing prices all over the board . From what I see I could spend anywhere from 400 to 1600 for plates and if they are all going to be doing the same thing , I can see that there is definately quality issues but if a Chevy is going to get me to where I want to go the same as a Cadilac why spend the money , I am trying to do this on a budget .

 

[velvetfoot]

"Do you mind me asking what your basement setup is like?"

I'm such an idiot, I meant "baseboard" not "basement". Impressive, to me, that you're going down to 120 with baseboard.

 

[Fred61]

I have the chevys and they work fine for me. Not evenly spaced and only confirmed that there was space enough between them to allow for quiet expansion.
They're small sheets of annealed aluminum that are formed on the job. The tubing can be installed without them, or sheets can be installed with any given space between them or they can be installed covering nearly 100 percent of the tube for areas that have a higher heat resistance such as under carpeted floors.
I got them from http://www.radiantcompany.com/. Annealing makes them very quiet which is especially good for my application. My zones cycle a lot due to low heat load.

 

[arbutus]

Better plates are able to transfer more heat from the water in the tube to the subfloor more evenly than worse plates. Take a close look at some of the thin plates - some have a very tight omega shape, some are a tight u, some are a very lazy u. Heavy extruded plates have a lot of aluminum mass that conducts heat internally very well, and gives most even conduction to the underside of the subfloor.

Do you have a heat loss calculation for this area?

Shoulder season warm floors might be iffy - figure 2 btu/hr per square foot per degree temperature difference between the floor and the air. The area is 15 x 30? about 450 sq ft. Let's say you need 4500 btu per hour - 10 btu per hour per square foot can be achieved with a 5 degree temperature difference. If the floors are five degrees warmer than the air temperature, say 75 degrees, they could still feel cool. If you heat the floor to a surface temperature of 80F, and want the room to be 70, that's a ten degree temperature difference or 20 btu per square foot.

I don't have a laser IR thermometer or anything I can get in good contact with the floor or I would try to take some readings on my own floor for you.

 

[webie]

My heat design was done at 140 degrees because I asked for it that way for heating with an older wood boiler . Right now I am at 138 coming out of storage outside temps are 20 degrees and zones are kicking in and out . Honestly now in warmer winter temps I am ok to about 130 and not much less but it better be above zero then . My baseboard is slantfin .

 

[Fred61]

I am forced to live with cooler floors most of the time except for mornings that are zero to 25 below because of the low heat loss of the house. If my floor was a continuous 75 degrees it would be like a sauna in here.