Radiant problems, Please HELP.

Rich Lorimer

Munchkin

I just attended a seminar on the Munchkin last week, It's an awesome little boiler, getting to be very popular, that's why the 4-6 week wait. I would seriously consider the "Vision 1" package with it. That adds an outdoor reset control feature to the boiler and can further increase your energy savings.

Good luck, Rich

Wethead7

Munchin good,but take that blanket off the floor.
Removing the carpet will also help. Your contractor has probaly aready said remove the carpet.

The additional heat emitters would not run as much and comfort will increase.

Mike

Duncan_5

*** I DO NOT AGREE!!! ***

Tom, you said above your contractor suggested:

"2)I remove the r13 insulation and place double foil sided buble wrap completly under the floor and tape up all seams and insulate the rim joists. Apparently this is where my installation is failing and the floor temps would go up to 80-85 by doing this. would there be agreement here?"

NO, there would NOT be agreement here. There would be questions here. Let me refine that... There would be agreement with your contractor's analysis of a possible (and likely!) source of failure. There would not be agreement with his solution.

Why not? Because earlier you said: [the existing installation has] "reflective foil underneath tubing then r13 insulation"

Why would you rip out one radiant reflective barrier to replace it with another??? Any gains from one foil over another would be marginal in this respect.

Why would you chuck the R13 insulation? It has proven, effective insulating value.

It's an awful lot of work and expense to tear out existing insulation IF the tubing isn't going to be touched anyway. You already have radiant and conductive insulation in sufficient amounts and qualities. I repeat: it will be significant work and expense for insignificant gains.

However... I suspect your contractor is on to something VERY relevant to your problem, and most likely he hit the nail right on the head (and sank it home with one blow).

That something is cold air leakage and infiltration at the end of each floor joist space, where it contacts the rim joist (the outside wall band) and sill plate. Same goes for warm air exfiltration in those areas.

This leakage will rob a very large portion of the heat you are putting in the joist spaces. A very large amount. Enough to make the difference between comfort and misery, between reasonable heating bills and outrageous heating bills.

I absolutely agree with your heating contractor with respect to infiltration and exfiltration robbing the heat. But I vehemently disagree with any claim that double foil faced reflective bubble wrap with taped seams is significantly more effective than plain foil radiant barrier in combination with R13 fiberglass batts for INSULATING value.

Now... if we agree that infiltration and exfiltration and air movement scrubbing away the heat is the main problem to address -and I think that's a reasonable assumption, if we're rounding up the usual suspects- Then let's isolate and address THAT problem before we go ripping out perfectly good insulation.

Why not simply seal the ends of the joist spaces around the rim with caulking and/or foam to seal the inf/ext leakage? Then insulate the end pockets.

Then if you want to seal the joist spaces to perform as hot-air-trapping plenums, use polyethylene plastic sheeting (also called visqueen) covered with sheetrock? Exposed plastic sheeting in an occupied living space is a fire hazard, and most probably a code violation.

My advice in a nutshell? Leave the good insulation, saving yourself a lot of work and expense. Isolate and address the source of the problem with direction and precision.

Sound reasonable?

I'm not challenging your contractor, and I'm not slamming bubble foil insulation, I'm just trying to help you, and I know what I'm talking about. I've worked with the Minneapolis Blower Door, and I helped in the development of the Colorado Office of Energy Conservation's Low Cost Weatherization project. That was a project based on the Princeton House Doctor approach to weatherization. It involved saving heat by attacking the major leakage areas using low cost materials like caulking, plastic sheeting, backer rod, and foam. It was studied thoroughly and scientifically, and results were quantified. The results were also subjectively impressive, looking at the weatherized home with an infrared camera before and after weatherization.

By the way, I've heard of log homes so leaky the blower door couldn't move enough air to pressurize the house, there were so many leaks. And blower doors move a lot of air at top speed! I recommend a product called "Log Jam" for chinking, it stretches remarkably, I forget how many hundred percent.

Oh.... those so-called "plates" are bogus as far as heat conduction in any usable amount goes, if they're what I think they are. They're nothing more than soft metal flashing. Maybe some radiant reflective value, but I doubt its worth. Ask them if they can show you the heat output numbers with "plates" and without "plates". Not to be confused with heavy extruded plates which increase both area of conduction away from the tubing and conductive heat flux applied to the floor.

Please exuse me if I'm coming on too strong, but like others who have paid their dues, I get frustrated and angry at those who take the money and run. But not at you or anyone trying to help you. Approach your contractor gently with my observations and see if he's receptive. I don't have to tell you: It's your money. Damn, I told you anyway!

Good luck Tom, let us know how it works out, OK?

Tom Towne

Duncan

Thanks for the very informative post. I too question the bubble wrap. I need to ask him about this again. He said that his radiant program does not have a calculation for 7/8 tubing but his estimate is that the floor only has a potential for about 13,000 btu at around 130deg water temps. Can you or anyone else confirm this. Another local contractor feels that 1/2 PEX run 8in OC should be added to the system. The other feels that this bubble wrap will get the floor where it is sopposed to be. Both are in agreement that the origonal set-up of 7/8 16OC would never heat the house to 70deg. Kind of confused. Thanks again.

Duncan_8

Can't confirm.

Tom, my reasoning is simply that 1) You already have enough insulation in place, and 2) Most of the heat loss will be at the band and sill plate.

That your contractor mentioned taping all the seams led me to believe he was trying to seal the joist cavities.

What I may have overlooked is that your installation may be over an unheated crawl space. If that's the case, I would look for some way to button up the underside of the insulation between the bays, since open fiberglass batts aren't impervious to drafts.

Plastic under the joists in a cold space could cause moisture problems in the winter, since moisture from the warm living side will condense when it hits a cold surface.

And by code, most crawl spaces are required to be vented to the outside to avoid moisture problems. In some areas, plastic is laid on the soil of crawl spaces to keep ground moisture from escaping into the crawl space. Mold may then become an issue in such cases, though.

You could temper the entire crawl space (if you have one) by insulating all crawl space outside walls with an appropriate insulation. Some kind of sealing of the fiberglass batts surfaces would still be in order, maybe Tyvek. But flammability is an issue.

I don't advocate staple up because of low output and inefficient heat transfer. As such, I don't have output numbers for staple up systems.

Their reasoning is that their tubing is thin walled and has sufficient surface area to equal heat output of two runs of 1/2" tubing. That would be 8" centers in 16" joist spaces. I don't buy their reasoning. Like I said, ask them to show you the numbers. Unfortunately, I would still be suspicious, unless I was absolutely sure the numbers came from a disinterested, objective third party like an engineering company.

I've turned down doing Radiantec systems, even when I was very hungry for work. Not because I don't work with DIYs or others' materials, but because I didn't want to buy a pig in a poke. I figured if the system wasn't going to work with two runs of 1/2" staple up tubing per bay (I did the math), it SURE wasn't going to work with their system. Plus, when I questioned them about using oxygen permeable tubing with a cast iron boiler, their reply was that cast iron boiler walls are very thick. Unacceptable answer, IMO.

John Siegenthaler may have some software that could give you an answer about single runs of 7/8" tubing output, I don't know.