Radiant Heat in Slab -- HELP!

Tom Newton · 2004-02-04T14:29:30+00:00

Hi Folks -I live in NY where it's cold, and I have a question here that I'm literallyafraid to ask. I have a contractor doing a new kitchen for me and he'salmost done and has 80% of his money. The kitchen is 12'x17' and, unlike therest of the house, sits on a slab extension out back (there's a fullbasement under the main footprint of the house, which is 90 years old, andthis kitchen extension is an appendage off the rear).The extension was actually pre-existing from about ten years ago when theprevious owner put in a laundry room and a few walk in storage rooms there.Anyway, my goal was to have the entire area over the slab gutted (12x17) andmake it our new kitchen, with ceramic tile floors, and have radiant heat.Here's the deal... we're almost done, the contractor put in the radiant heattubing long ago, laid the tile done weeks ago (but never hooked up theheating system to the boiler till now) and has continued to build thekitchen and is almost done with everything.But yesterday, they finally hooked up the radiant heat to the boiler, andthere is bad news. After running it for two hours at 180 degrees the damnfloor is still cold... and the return water is barely luke warm!I'm starting to worry that this whole damn thing has to be jack hammered upand redone -- an unimaginable thing given the amount of time we've beenwithout a kitchen (my wife will not survive this if it's true!).My question is, based on the original requirements I gave, did my contractordo everything right?First, since the new kitchen is on the north end of the house, while radiantheat sounded like a good idea, I warned him profusely that it gets coldthere... and wanted his assurance that the system he installs had plenty ofpower to get this space warm and keep it comfortable at a reasonable cost.These were the steps he took -- 1. The whole heating project was done by him with direction given by his"plumbing and heating guy"2. First, he basically reframed the whole extension (12x17) because it...

Feb 04, 2004 Last reply: 22 years ago 22 Replies

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Doug Pearce 22 years ago

Tom,

Unfortunately this response is not going to be much help for you however for the group, we have solved this problem a few times by insulating the slab under the in-floor radiant heat with one of our multi ceramic insulations. Here is a link to some pictures of one of the projects.

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Granted this is not the optimum application for this technology. See the Note at the bottom of the page!

ie. NOTE : In this particular application the SUNSHIELD 2000 is completely buried in concrete and consequently only 2 of the 4 ceramics will come into play. The 2 reflective ceramics are ineffective in this type of application because the coating is facing direct contact, low temperature, front side conduction. This will reduce the R value equivalency to approximately R10. Additional R value equivalency can be achieved by adding more thickness.

An addition 7 mils DFT will only equal an additional RE3.

Prior to the application on the first project I worked with the Engineering Firm involved and we completed a successful test of this method of insulation using thermocouples buried in the test slab as well as taking top and underslab temperature readings.

Hopefully this information will be helpful to others that are faced with the lack of space constraint.

Best Regards, Doug

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m Ransley 22 years ago

I tried ceramic paint additive and found no r value using an IR thermometer on painted heating ducts. I like to see an INDEPANDANT test of R value. on your product I used 1 " R 7.2 foamboard under my concrete basement floor , that is proven to work. But a perhaps better way would be using a natural product such as pearlite , but something harder

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nicksanspam 22 years ago

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Indeed. Is it April 1 already? :-)

As I recall, soil has a thermal resistance of about R10, so it looks like your 14 mils of miracle stuff adds about R0.0, as anyone knowing some physics might expect from its thickness. You seem extremely confused, if not a serious crook, exceeding HVAC criminal standards by a very large margin.

Best regards,

Nick

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