Yes there is some striping with cheap aluminum heat spreaders, but it's only annoying to the princess with the pea. The noise only occurs when starting up cold- with a dialed-in mod-con it should run nearly continuously. Staple-up without the heat spreaders the striping is more pronounced, but still way better than struggling to keep the room up to temperature without cranking the water temp to 180F.

Have you done the heat load calculations for the house, room by room, zone by zone? If not there's no way to know whether 120F water in a suspended tube would keep you warm.

The U-factor of R13 walls with only 2" of closed cell foam is a lot lossier than with a full-fill 2x4 fiberglass or open cell foam, due to the fact that the framing fraction losses are nearly double. It's the same R13 for the ~75% of wall area that is cavity, but the 25% bridged by framing drops to about R2.5 instead of R4.2, which is why you'd be better off with 3.5" of open cell foam than 2" of closed cell foam. The 2" closed cell foam is dramatic step DOWN in "whole wall R" performance, and even a full cavity fill of closed cell foam improves the whole-wall numbers by less than R2.

With typical sheathing & siding options a 3.5" / R13 open cell solution ends up about R10.37 whole-wall (all in, including the R value of the sheathing, siding wall board, interior & exterior air films).

With the same options a 2"/R13 closed cell solution comes in at R8.03, a ~20% reduction in performance.

An unrealistic 3.5"/R23 closed cell solution comes in at R12.66, but you can't trim closed cell foam flush with the stud edges. A 3.25"/R21 is more realistic, and that comes in at R11.89 whole-wall. You can buy that much performance for far less money with 3/8" XPS siding underlayment installed under your wallboard.

For IRC 2015 code on unvented roofs you have to do a bit of interpolation. Code minimum is R49 total, but for unvented roofs it needs a minimum of R15 of that to be above the roof deck, or closed cell foam under the roof deck, with the fiber snugged right up to the foam. See Table R806.5:

http://codes.iccsafe.org/app/book/content/2015-I-Codes/2015%20IRC%20HTML/Chapter%208.html

For walls it's similar. See R702.7.1:

http://codes.iccsafe.org/app/book/content/2015-I-Codes/2015%20IRC%20HTML/Chapter%207.html

With most types of siding you'll need to go with the MemBrain on the interior, which behaves as a Class-II vapor retarder when the sheathing is cold enough to take on wintertime moisture, but becomes vapor open when it warms up, releasing it's moisture burden.

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As a follow-up I've moved forward in some areas and took some advice from your above posts- thank you.

1. Had the closed cell foam installed and the "great room" is able to maintain 65' inside temp (without any baseboard in the room or radiant) while outside is low 41's. 3" +/- ceiling and 2" +/- walls.

2. Looked into LoopCAD in depth and updated my floor plan with windows, doors and proper insulation values. I also added the actual design layout of my radiant tubes.

3. Purchased "Omega" shaped radiant heat plates from an eBay vendor. They are thin, but the cost difference was huge (Uponor $1.8k vs. $400). I plan to install them next weekend - probably with a puematic staple gun. My plan is to run R-19 Fiberglass bat's under the plates in the joist bays.

4. Changed my control strategy after speaking with an Uponor engineer. They strongly recommended moving away from the constant circulation system and using Taco Zone controls, thermostats with slab sensors and zone control actuators. The pricing isn't bad and this is what I was thinking to begin with.

Before all the below images take up the rest of this post I have two questions:

1. Basement heating issues: My basement seems to require 9k BTU/hr and I am trying to maintain a low water temp throughout the house. Choices:
1.A. Synergy Baseboards offer ~320 BTU's per foot at 4 GPM & 120' water, but the one price source I found seemed to indicate they were very expensive and I will need 27' of baseboard...
1.B. Install PEX tubing and create a radiant wall on the lower 4' of the room. LoopCAD doesn't have an option for this so I don't know how much Pex is required or the BTU/HR output.
1.C. Find some type of hidden cash and have the basement slab broken up, foam installed, pex tube, concrete pour. (I don't have the funds I think).
1.D. Alternative heating solutions? I'm open to anything.
1.E. I plan to follow the above advice for the garage and basement with foam boards and fiberglass so I will seal this space up as best as possible. It is also half below grade so it has that going for it and I'm not sure what my downward losses will be on the now staple-up/thin transfer plate Pex & R19 below it.

2. Pump sizing and recommendations? I tried to follow Taco's document "TD10" and calculated I need a pump that flows 1.3 gpm for my radiant system. LoopCAD tells me the total flow of the manifold is 2.34 gpm. I'm a little confused here.

3. By changing from constant circulation to zones and floor sensors will I have a lot of noise from the heat transfer plates? If so anything I should do to prevent this?















NOTE: After reading TD10 I now know I should be using 5/8" PEX due to min/max flow ratings of the tube. I think 3/4's minimum flow is 2.3 gpm which would be all circuits running.

If your basement is 1/2 above grade, then most of its load will track the load of the first floor and can be provided by back loss from the overhead plates. How much back loss there is is under your control (with the amount of insulation).

1) Pump sizing and recommendations? I tried to follow Taco's document "TD10" and calculated I need a pump that flows 1.3 gpm for my radiant system. LoopCAD tells me the total flow of the manifold is 2.34 gpm. I'm a little confused here.

Assuming the LoopCAD design was done correctly, that should be required total flow rate. If you elect to use a fixed speed pump, you need to find one that places the required total flow rate near the center of the pump performance curve (i.e., the GPM versus Head curve). This is typically the BEP (Best Efficiency Point) of the pump. The other albeit more expensive alternative would be to use a variable speed pump that utilizes a smart controller. The combination of variable speed ECM (Electrically Communicated Motors) and smart controller enables these pumps to be significantly more efficient than their cheaper fixed speed relatives. Both Grundfos and Taco sell these pumps.

2) By changing from constant circulation to zones and floor sensors will I have a lot of noise from the heat transfer plates? If so anything I should do to prevent this?

Plate systems often make noise anytime they see a change in temperature. It’s called oil canning and some people find it more annoying than others. So whether it will be objectionable to you depends on your temperature swings and your personally sensitivity. I don’t think it would be any worse than a hot air furnace cycling on and off.

Posted By sailawayrb on 23 Nov 2016 11:02 AM
The other albeit more expensive alternative would be to use a variable speed pump that utilizes a smart controller. The combination of variable speed ECM (Electrically Communicated Motors) and smart controller enables these pumps to be significantly more efficient than their cheaper fixed speed relatives. Both Grundfos and Taco sell these pumps.

Thanks for the advice!

I ended up going with a Grundfos Alpha.

If anyone was reading this looking to purchase equipment WestSide Wholesale has a black friday coupon you can use for multiple orders. $50 off of $500+ order. Split mine up and saved myself a few bucks. Plus no sales tax.