Hi Everyone - I am in the early stages of designing my forever home in Southeastern Wisconsin. It will be a two story traditional design with about 3300 sq ft on the upper two floors plus a 1600 sq ft walkout basement. I will be doing ICF walls and have always dreamed about doing hydronic floor heating. I'm a newb, so I have some questions I was hoping you could help with... 1.) I plan on laying the PEX right into the basement slab, but I am struggling on what to do for the upper two floors. If I do a staple-down method and then fill with gypcrete, do I need to do any special preparation/reinforcement of the subfloor to be able to handle the weight of the gypcrete? 2.) I've also briefly looked at Warmboard-S as a subfloor option, but this seems quite expensive and I wonder how the rough carpenters will respond to installing a material they're unfamiliar with. I also like gypcrete because it seems like it would provide a more "sturdy" floor base as well as offer sound deadening between floors. Is that correct? 3.) Is gypcrete commonly seen on the second floor, or is a staple-up method recommended there? Or maybe I should just do forced air on the second floor since I will already have the ducts run for central air conditioning? 4.) My great room will have 20 foot ceilings (no loft); I assume this won't be a problem for radiant, correct? Ideally, I'd like to have radiant on all three floors, but I also need to consider cost and complexity. Since my walls will be ICF, I wonder if radiant is overkill. But I've heard it is one of the most luxurious things you can do in a new build, so I don't want to regret not doing it. I just need to wrap my mind around the most cost effective way of doing it. Finally, if there are any contractors in the Southeastern Wisconsin area, I'd definitely be interested in a quote! Sorry for the long post, and I appreciate any insight you guys might be able to offer!

1) You should consider consulting a licensed structural professional engineer in your State to determine acceptable floor loads for your design. Usually, gypcrete will be acceptable in most designs.

2) Warmboard is crazy expense (i.e., similar to plate systems), but Warmboard is a much more efficient hydronic radiant emitter than a plate system emitter because the PEX surface contact area and thermal heat transfer is far superior. Normal slab and thin slab (e.g., gypcrete) are the best hydronic emitters in terms of efficiency…even better than Warmboard because they provide even better PEX surface contact area...which means they can heat the living space with the lowest supply temp possible. Below floor PEX hydronic radiant emitters are the worst, by a lot, and are best avoided unless you are doing a remodel and absolutely feel the need to have hydronic radiant floor heating.

3) Yes, gypcrete is commonly used wherever a normal concrete slab (e.g., a 4-5” thick concrete reinforced slab) is not used. But even a normal concrete slab can be used for upper level floors with some applied engineering.

4) Hydronic radiant floor heating keeps the heat where the people are located. It doesn’t put hot air where it isn’t needed and waste energy in the process. So hydronic radiant floor heating is the best heating method for high ceiling living spaces. However, hydronic radiant heated floors in energy efficient buildings (i.e., buildings that are well-insulated and well-sealed at current code levels or in excess of current code levels) will not feel warm. But these floors will not feel cold either. Often, only a floor surface temp of 71 or 72F is needed to keep the living space at 70F. And many people find that a living space temp of 68F is very comfortable as the heat is close to where the people are. Comfort is largely a function of the mean radiated surface temp of your surroundings and not so much the actual air temp. This is why you can be outside at 10F next to a fire radiating heat and feel perfectly comfortable.

Mini splits are an efficient way to cool and heat too. And if you require AC, mini splits may make more economical sense. But for heating, nothing is more comfortable than hydronic radiant floor heating…no noise, no air drafts, no noticeable cold/hot living space spots/cycles and just very comfortable.

Sailawayrb, great info....I just want to add a bit.

On our last house I have the floor truss company add in the weight for an inch and half of straight concrete to the design. It didn't change anything in our case. Concrete weighs 18.75 lbs for a square foot at an inch and a half. Most floors have to be designed to handle 40 pounds per square foot of dead weight. And also concrete is supporting (that is why bridges are made of concrete and not asphalt). May first house I just did it and also didn't have a problem. Not saying you shouldn't let them know and have them add it into the calculation.

As a reference Cellulose which is 3 times the weight of fiberglass is 3 lbs per cubic foot. R60 cellulose is 17 inches thick so comes out to 4.25 lbs per sqft. So a 3000 sqft house can have 12,750 pounds of cellulose in the attic....hmmm....I put fiber glass in mine at 1/3rd of that weight...

Thanks Newbostonconst. As I said, gypcrete is usually acceptable in most designs, but I would not give blanket approval and I would strongly recommend getting engineering approval before proceeding. Also, while reinforced concrete can be constructed to be self-supporting (the rebar provides the required tensile strength which concrete lacks), I don't believe that is the case for non-reinforced thin-slab gypcrete, which I believe just reduces your dead load capacity...and hopefully not to the point of floor failure.

This is an old post but wanted to find out which company did you finally go with? I am also building an ICF home with unfinished basement, 1st floor insuldeck with concrete and 2nd fl wood truss.