Challenging "design."

SpeyFitter

Many of us who do design have some kind of manual or a various formulas we follow to complete our methodology and design our system. Some may be following siggy's book to a tee, some may use some other manual. But I'm curious if you guys challenge your heat loss & your radiant design. I guess the best way would be in your own home.

For example, a buddy installed some staple up radiant in his house with a Buderus GB142 boiler. Everyone says you need insanely high temps to do staple up (he has heat transfer plates with R-14 below the pipe but it is heated basement below). He has about 2 1/4" of wood (3 layers of plywood plus hardwood) above his staple up plus some rubber sound insulation in between there. So he's got some good R-value in his floor. And yet he has his boiler set at 110 degrees max temp with and outdoor reset sensor. He says he's never really had any problems with it heating the house. Sure his basement has radiant heat. But his basement is a cement slab with radiant in it, with a few layers of plywood and then either hardwood, or tile (with some schluter Ditra under the tile). The entire system is operating under the same temperature regime (110) with  with one t-stat on the bottom floor, and one t-stat on the top floor both set to 70 degrees.

Do we really need high temps for these staple up with plates applications? Have you tried challenging your designs? Are there variables we do not account for? Do designs ever work out the way they are supposed to?

Mark Eatherton

That is not true "staple up" in my opinion...

Using plates significantly lowers the operating temperature because it keeps the heat transfer in the conductive mode, the KING of heat transfer.



Had he used true "staple up" or "suspended tube", I assure you he WOULD need a lot higher temperature of operation in order to deliver comfort.



Neither of these systems are really new, and have been proven to work, provided that you do the math first. These system do have a limit as to what they can deliver BTU/Sq Ft/Hr, but they do typically require a higher operating temperature than the conductive (tube in concrete with low R covering) alternatives.



The heat loss of the home also has a lot to do with the degree of comfort. If he has an older home with a loss factor per sq. ft. greater than 30, and he had used real staple up, he'd have a hard time hitting the numbers at design condition.



Just because the heat source is below the floor doesn't mean that it is staple up.



I've seen staple down jobs poured in gyp crete that didn't work very well. The floors were covered with thick pad and carpet. It all comes back to design, and planting the seeds of change in the consumers mind early, and getting control of the floor coverings being placed on top of OUR heating systems.



Don't let the consumer tell YOU what THEY are going to put on the floor. You have to tell them what they are allowed to place over the top of YOUR heating system if you are to guarantee its performance.



Turning operating temperatures up can only overcome so much resistance value....



Oh yeah, and there IS a difference in the performance of heat transmission plates. Light aluminum flashing materials do not work as well as a good extruded plate. Aluminum is aluminum, but not all plates are equal.



ME