Radiant Heating Issue

Question?

The company I work for installed radiant in floor heating in a 6,500 square foot house in 2005. This winter we are having some issues with heating. We are in the northeast corridor of the United States and our design conditions are 15 degrees outdoor temp. with a 20 mile per hour wind.

The entire system was designed off of Wirsbo ADS without any red flags for secondary heating.

The whole project only requires 66,069 BTU's with a maximum water temp. of 129 degrees. The complete instillation excluding the basement and garage are in a gyp. over pour. Every room in the house is maintaining 72 degrees except the Master Suite (which is located on the northeast side of the house) and a kid’s room (which is also located on the northeast side of the house). These two rooms only seem to be able to maintain approximately 66 degrees. Both rooms have carpeting with an R-value of 3.19 which WAS factored into the software.

The system is powered by a condensing boiler which is set to run @ 160 degrees and it is mixed down with a Wirsbo 101. With full outdoor reset. The side of the house where we are having the problem has a manifold with 4 zones and is zoned with telestats. We do have a 14 degree drop across the tubing in the floor of the master suite.

We are looking for any help in clues in locating our problem.

10 btu/sqft ?????????????????

The 10 +- btu/sqft should have sent a red flag up. It is very rare for a project to have loads this low. My guess would be that the information that was input into the software was inaccurate. Run a new heat loss calculation.

Tim D.

The project does have second stage hydro air which was designed at 160 degrees it just dosen't opperate off of this t-stat.

We reran ADS after the project was completed and rechecked everything and still no red flags! I can send you a copy of the ADS if you have the software.

emmitter area

Did you account for the monstrous insulators that are taking up floor space in the bedrooms??? The mattresses are no heat emitting areas. The king size beds are probable nice and toasty but block heat transfer to the rest of room occupants.

my first time

I did 12" on center my first time, didn't like the floors preformance, luckily the gypcrete wasn't flat enough.

tore it all out and started over, 6" centers, very happy....

luckily it was only a 235 sq ft addition.

most people here seems to agree on tighter spacing.

That's a lot of wall exposure relative to floor area with lots of corners. Did you verify that the actual construction met your design assumptions? Can the software even compensate for those angles? With such low btu/sq.ft calculations I'd almost consider those corners like tube fittings--they may be short but their effective length is much greater...

A 66F bedroom where the common areas are 72F honestly doesn't sound bad to me--in fact some people would prefer such...

With the carpet and assuming that all of the floors have the same supply temperature available, I think I would have tightened the tube spacing regardless of what the software said...

This also sounds like a "hybrid" system of true hydronics and "hydro-air". Are you positive that the hydro-air isn't "hogging" heat? Such is very possible if the occupants are using significant daily setback in the hydro-air zone(s).

I recall Hotrod having some serious experience-related issues regarding a hypothetical design that I posted here with carpet in the master bedroom. Something along the lines of, "The numbers might seem good, but reality is different."

The area with granit was in the same room. It was in front of a fake fire place.

What Mike sez

Patrol the envelope and make sure it got installed right- cracks sealed, insulation properly applied, windows as spec'd or better. Then, as others have pointed out, go back to the calculations and make sure that realistic, correct values were used for the inputs - you DID use the "overall U value" for the windows, and not centre of glass, right? You did pro-rate the wall R values for thermal bridging if and where it exists, right? The infiltration values and vapour barrier values were "assumed" reasonably?

10 Btuh per SF is nice, yes it may seem low to some folks but if a high quality envelope and window system was used, that's pretty reasonable. I've designed a house in the mountains up here with a -20F winter design temp and it maxed out at 6 btuh/SF (Four element krypton filled Visionwall windows and 18" thick walls, etc.- nice when the owner's needs were driven by the needs for stable indoor climate for horribly expensive antique furniture)

Any reasonable way to add panel radiators with TRVs to the high-temp portion of the system? Even if an utter slave, (e.g. under the control of another thermostat and using an existing circulator) it doesn't sound like you need too much heat to "tip the scale". Calculate your deficit and then grossly oversize the panels. In other words don't assume that the supply temp will be that of the high-temp circuit--more like 90F or so... Even then I suspect that the panels won't be particularly large.

i did a similar designe year before last....

except that the space that juts out, is all glass and is a dining room.

over a cif stand up "crawl" space. i put it on a separate zone and the kitchen on another. the kitchen sorta over extends into the area with a dish washer that turns L by that first window. I backwards L walk trough is tile as is the dining room. i had wanted to add a panel rad ,,,your going to probably best off with one . use your heat gun IF to locate the tubing and chip away at it until you can just drill the two holes...re do your heat loss and add the emitter where it can radiate like mad and get the best convection current...turn the temps back to where you had them..and dial the temp down in the panel emitter so you get the lowest temp fluid zooming through it...

honestly , i hedged my bet by running out two lines (Under the floor)despite the objection to having it under a dining room window...

i stuffed two pieces of 3/4" through the floor before the pour... that way i can glide the 1/2" thru there in a flash..they havent complained this year..or last.. well over 50 below last year..

radiant

shouldn't the load calculations be set to 0 degrees for the northeast at 25 btu's/sq ft

Limiting factor of radiant floors

Mark I have to ask why people don't use radiant ceilings in the potential problem areas, where floor coverings, and furniture decrease output? You never know how much furniture or how floor coverings may change after the original installation.

Bedrooms in particular can rob some floor area output with beds, and furniture. Usually because the floor space to furniture area ratio is rather small in most homes. A 300 sq.ft. bedroom could lose 1/3 of its output to furniture, plus carpeting of r3

This to me is the beauty of ceiling radiant, more effective output area with less chance of being restricted.
Usually the restricted areas are under kitchen/ dinning tables, desks.

One other thing is why limit yourself to 1' spacings? other than being cheaper it really limits your potential output,and once put in you are bound to it. Easier to decrease supply temps than increase from a efficiency stand point.


I'm just a student so I'm only looking for answers through asking questions. So I'm not saying everyone is doing things wrong. I'm just looking at things from a different perspective.


Gordy

Kal

Sorry Kal, I don't buy the cold feet with ceiling radiant. I have both floor, and ceiling radiant.
When it comes to hardwood or tile in kitchens, baths solariums, I agree floor radiant there is no better way to go. When in carpeted areas you don't get cold feet with ceiling radiant.

Covective currents will chill ya no matter the heat source though, and I will agree window treatments are a cheap r value to keep high glass areas at bay.

Gordy

work

The install looks good. Nice and neat.

Massachusetts

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When you

calculated the R value for the carpet, did you account for the padding? and did they use the same stuff they told you they were using? or did they decide on the upgrade at the past minute because it is their master bedroom...

a few thoughts

RC

I grew up with radiant ceilings. It rocked.

Blower door

Infiltrometer Blower door and an infared camera I have the blower door but not the camera . My guess is infiltration is high in that room,but I'm not counting out other comments made here.

Point is this there is NO and I mean NO such thing as anaccurate heat loss without a blower door period. If you don't know the infiltration than you don't know the heat loss.

Case in point I own a 1900Sqft shed dormer cape circa 1992 .
My client owns a 1900sqft cape circa 1992.

my cape has 7.8ACH per day,my clients has 23!!!!!ACH per day yet a heatloss on both homes would be the same without this info. however the real heatloses and heating costs are vastly different.

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Tubing layout approach

Looking at the photo of the tubing layout which is a nice job by the way. I will assume that the wall to the right is an interior wall.

Would it have not been a better approach to serpentine the tubing in the opposite direction to allow more of the supply end of the loop to bear the heatloss of the bay configuration?

This would also have allowed you to tighten tube centers at the bay, and space greater toward the interior. Stop that loop at the jog in the wall, then pick up the exterior wall to left with seperate loop as is, only tightening centers at the exterior wall, and increase spacing to the middle of room.

For give my crude etch a sketch. I know this does not help now, but your problem is also help in dealing with future installs to avoid these issues. Maybe the greater minds than I will have differing opinions.

Gordy