Will radiant staple up crack my tiles?
myriad
| Posted in Energy, Heating & Insulation on
We are just in the process of finishing our basement, and I have radiant in my basement slab and DW wants it stapled up under the kitchen floor. We primarily use FAG for heating, so the staple up would just be there to warm the floor.
Here’s the question: when I laid the ceramic tiles in the kitchen, I used 3/8″ plywood glued & screwed down onto the 3/4″ TG plywood subfloor and then the tiles thinsetted on top. My heating guy (know-it-all type) said that if I put radiant tubes underneath, I would cause the plywood SF to lift up and crack the tiles. Is this bull$hit or not? I mean it sounds feasible I guess, but I obviously wouldn’t want that to happen!
Edited 2/1/2005 2:46 pm ET by myriad
Replies
This is a really great question, never come across such a situation...but I'll give it a bump for ya.
Justin Fink
FHB Editorial
Use conduit clips screwed to subfloor instead of shooting or hand nailing big staples.
Bear
It is my understanding that the heating installer was asserting that the heat from the tubes would move the ply and therefore the tile, not that fastening the tubes would do so..But also a valid concern.
By the way, I seriously doubt that the tile would crack.
What the HECK was I thinking?
Edited 2/1/2005 4:43 pm ET by Heck
Yeah, sorry I guess I wasn't clear enough. The heating installer meant the heat would heave the floor, not the stapling thing.
The objective would be to use as low as fluid temperature as required to provide floor warming (75 deg F to 80 deg F surface temps.). To achieve this use a high grade aluminum heat transfer plate and close tube spacing 6” to 8” o.c. (Stay with the same brand of pipe and plate).
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Have the radiant designer use a nominal 5 deg F as his/her delta T in calculating flow rates which is obtained by this formula: (I posted it just for your info...a competent designer would use this day in and day out.)
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<!----><!----><!---->US<!----><!----> gpm = (Heat Loss, Btu/hr) / (60 min/hr * df, lbs/ft3* cf, Btu/lb * deg F * delta T, deg F) , df = fluid density, cf = specific heat
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This will allow for thermal consistencies in the assembly.
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Fluid and surface controls are important so have the contractor install a dual sensor (floor and room) thermostat made specifically for this application and set the maximum floor temp to a nominal 78 deg F. (brand names include tekmar, OJ, Danfoss, Wirsbo). As far as fluid temp. controls...both Wirsbo and Danfoss have some very slick preassembled systems for floor warming...your contractor can get these from the wholesalers.
Obviously if you started the floor system up when the building was already warm there would be less temperature differential between the fluid in the pipes and the floor surface temperature. For added security, one could ramp the fluid temperatures up slowly a few degree per hour until operating temperatures are reached. As long as the house was warm and the fluid temps kept below a nominal 100 to 110 deg F the floor assembly will have very little thermal expansion stresses…so long as proper tile installation methods were followed and a construction grade adhesive (PL400 or better) was used … there is little chance of being affected by such low temperatures. (notice I didn’t say zero chance)
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Keep in mind, depending on your location and architecture it’s possible to have greater thermal expansion from direct sunlight on the floor surface in the summer time than what might be experienced by heating the floors in the winter.
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See the following additional posts for installation <!---->info<!---->rmation:<!----> <!---->
radiant heat insulation Jan-31 <!---->10:23 am<!---->
Spraying icynene on staple up radiant Jan-27 <!---->1:46 pm<!---->
That's my two cents....
<!----> <!---->RBean
http://www.healthyheating.com
http://www.healthyheating.com/blog
Great post, RB.
What the HECK was I thinking?
When I saw the thread title, my first thought was:
"Only if the staples hit the tile".
.
Sorry, not really helpful.
Funny, but not helpful.
Sounds like BS to me. Bruce Hoadley's book Understanding Wood says that the coefficient of thermal expansion for wood in the radial plane (which is how rotary cut plywood veneers are cut) is in the neighborhood of 20 microinches per inch per degree F. If my calculations are correct, that translates to 3/4" plywood changing thickness by less than 1/1000th of an inch over a temperature swing of 50F.
More wood movement from moisture changes rather than temperature changes... The heat could cause the ply to dry out more, but that probably happens in the winter anyway.
Billy