Hey guys, i am planning on placing the tubing for my radiant on the midle level of my house. I have two loops of 250' 1/2" pex and a double manifold to install. I have not yet been able to get a load calc for my house, being a computer illiterate and around here there is no one to get advice from for radiant so if i get help its gonna be from y'al. Its a sips house with lots of windows to the south and west with good winter sun. The room is 513sqft one third of which is open to above loft. stairs and cabinets eat up almost 150 sqft so its about 360 of radiant that i plan to pour 1 and 1/2 inch thick. My fear is that thehouse will get hot and the floor will not feel warm. I have considered running the two circuits alternating onr to the other OR running one loop in the kitchen/breakfast nook area and another loop in the living area under the vaulted ceiling area. What i need help mwith is what is a good spacing for a 1 1/2 inch thin slab. How close should i go near big windows that run all the way down to the floor. They are 8 feet high and 6 feet wide. I probably have too much tubing but i can cut down the loops if i need to. Im gonna try to include a picture of the room from the kitchen towards big w indows. Any advice will help very much. Thanks ahead of time for you help. Michael PS My house has a heat pump so the radiant is a suplimental heat/luxury for us. We like going shoeless. javascript:amaf_insertHTML('%3Cimg%20src=/DesktopModules/ActiveForums/viewer.aspx?portalid=0&moduleid=369&attachid=2848%20border=0%20/%3E');amaf_toggleInline(2848,7093,0);

In order for any radiant flooring system to work properly the btus needed must be calculated. The flooring covering will have a huge effect as well. Tubing does not need to be installed under built in cabinets,etc. Tube sizing and spacing are determined from the heat calc.The nice thing about radiant is if your calcs are not quite accurate the system can be tweeked by changing water temperature. Typical spacing is 8" on center. Pex tubing has a minimum bending radius and would be difficult or imposible to attemp a tighter spacing.

Thanks AC, not putting any under the cabinets and we do not plan on any floor covering ecept throw rugs and possibly marmoleum if craking turns out to be bad. I wont be installing till first of next week due to the blazing hot temp. With a thin pour like this should spacing be increased or decreased? Thanks for your response. Michael

The tube spacing is determined by heat load for a particular room, floor covering, medium and design water temperature. The bend radius is determined by the diameter of the PEX specified. All should be specified by the radiant floor heating designer calculated from his heat load.

I have not yet been able to get a load calc for my house, being a computer illiterate and around here there is no one to get advice from for radiant

Some of the mail-order supply houses can give you design assistance by phone and e-mail for a low price. That might be better than doing something you will regret. If your primary aim is warm toes, with a thin slab you need to have tighter, rather than looser spacing to avoid cold areas, particularly if you are concerned about overall heat delivery to an already heated space.

Do let us know how it turns out, whatever the outcome, so we can hear what works and what doesn't.

Funny thing, we have been designing and installing radiant floor heating systems with plastic tubing since the mid-80s and we know what works and what doesn't. People who insist they can't find anyone, who knows anything, about radiant floor heating, are either unwilling to pay for the service or have not looked very hard.

http://www.badgerboilerservice.com/contractor.html

Badger, thanks for the helpful comments. I tried contacting you maybe 6 months ago several times, i believe you were slammed with biz and replied you were a couple of weeks out. I tried calling at a later date and was never able to speak to you. I did recieve an email discussing payment terms but i had not yet even discussed price so i did not follow up. Sorry i was unable to contact you in person, im sure you could have helped. I think you may have missread my post. I have been unable to contact someone LOCALLY for advice. It would be easy to hire someone to do the job. I am building this house personally and have used this site extensively for the entire process from design to materials and techniques. I cannot overstate the amount of free help i have recieved from this forum thanks to you and many other contributors. I think i am going to concentrate the tubing where our feet will be most often, in front of the couch, under the bar stools , in the breakfast nook and in the trafic areas of the kitchen. Im guessing 6" -8" spacing in those areas with 10" to 14" in all others. If we can be alittle warmer in front of the big windows and in the kitchen then the entire house could be much cooler. Any advice relating to this would be much appreciated. thanks again. Michaeljavascript:amaf_insertHTML('%3Cimg%20src=/DesktopModules/ActiveForums/viewer.aspx?portalid=0&moduleid=369&attachid=2851%20border=0%20/%3E');amaf_toggleInline(2851,7093,0);javascript:amaf_insertHTML('%3Cimg%20src=/DesktopModules/ActiveForums/viewer.aspx?portalid=0&moduleid=369&attachid=2852%20border=0%20/%3E');amaf_toggleInline(2852,7093,0);

Thanks for all the usefull adice guys, it is done! Concrete showed up late and HOT. Thank goodness i hired a top notch finishing crew. Towards the end the crete was like wet clay but they got it done.

What kind of a mix are you placing in that image?

My fear is that the house will get hot and the floor will not feel warm

With today's well insulated houses and low floor temps, are some of the comfort advantages of whole house radiant gone? Does it make more sense just to use radiant in a portion of the house (say tiled kitchen and bathrooms)?

The mix is 3500 with super p and a min retarder. You can see in the photo it is Very low slump. We were hoping for 6" but at the end it was just plain tight. We hope to use the concrete as the finished floor with a few throw rugs. So far there is only one very fine crack. I was afraid it would have that parking deck "bounce" feeling but its just the oposite. The floor feeels even sturdier with the aditional weigh. Zero bounce. Feels like a slab on grade.