Tuesday, July 10, 2012

Dry Radiant Heat

Rob & I have gone back and forth several times on whether or not we were going to use radiant heat through the whole house.  We wanted to, but were worried about the cost.  If we'd had Visionary include radiant heating in our quote we figure it would have added at least 20 grand to the total.  It may have even cost more than that by the time they re-engineered the house to support the layer of gypcrete that they would have put down over the tubing on the main floor.

First we thought we'd just use radiant in the basement and forced air on the main floor.  Then we got to the point where we decided to run baseboards to heat the the main floor.  I was a little leery of keeping the great room warm with the large expanse of floor, minimal walls, a large sliding door to the deck and plenty of windows, but was reassured that it would be fine.

In the meantime, Rob and I kept talking about it, asking questions and researching online.  When it was almost time to order everything we FINALLY made our final decision to run PEX through the joists under the subfloor.  Once that decision was made then we had several more decisions to consider.  How were we going to "hang" or support the tubing?  How were we going to keep the nails from the hardwood floor installation from going through the tubes?  How were we going to insulate between floors? 

The guys at Peterson Plumbing were invaluable as they offered advice and answered all of our questions.  They suggested using heat transfer plates in conjunction with the tubing and flatly stated that the foil bubble layer was basically a waste of money. 

Ray did a heat loss calc for us and Rob started planning the loops for each of the zones.  This was a lot more complicated than what we did in the basement floor; designing and installing required a lot more attention to detail and flexibility when adjustments needed to be made.

The heat transfer plates are made out of aluminum so they are excellent conductors of heat and allow the heat to transfer to the subfloor above, (this is the ideal - heating the floor above by conduction and convection).  In ideal situations the plates are stapled directly to the subfloor but because we are having hardwood installed in our great room our builder asked us to fasten the heat transfer plates to the top "I" part of the joist.  This put the tube about an inch below the subfloor. 

Justin suggested running an extra loop or two under the shower for an extra toasty floor in the winter and avoiding the joist where the dryer vent runs out of the house, but #1 - I forgot to review my notes before we actually started doing the installation and #2 - that would have made a complicated situation even trickier.  But we probably could have managed to avoid the dryer vent if we'd thought about it ahead of time.  (I can't remember why we were supposed to do that though - was it to keep that spot in the floor from getting extra hot?  was it to keep the vent hose from getting too warm?  I didn't right down the reason why in my notes, and am afraid it's too late to do anything about it at this point.)

It took the framers a little longer than expected to finish up so we weren't able to get started until Thursday night.  Rob and I started out by measuring and marking the locations of the rooms upstairs and the areas where we didn't need to run any tubing (the stairs, the pantry, under the cabinets and in closets).  It took a little while to get used to thinking upside down as we marked the ceiling above us.  Then we tried walking the loops from the mechanical room, out and back again.  It was both a help and a hindrance to have the joists to work with. 

Thanks to our amazing helpers we were able to finish up in three (long) days.  Granddad and Mark and Emily helped us out on Friday, Karen and Steven helped us Saturday and Granddad and Grandma came over after their shift at the temple and helped (I wish I'd gotten a picture of Grandma up on the ladder!), on Monday, Mark and Emily came and helped us get finished up.  Grandma also helped by keeping Noah so his mom and dad could come work.  And it was HARD work.  We needed 1" holes drilled in the joists for the PEX to run through.  We needed the total linear feet of tubing pulled off the coil and fed through the holes in the joists.  We needed to have the heat transfer plates stapled to the joists.  AND this was all done overhead while standing on ladders.  Rob looked into renting scaffolding but the lowest available was 5' and that would have put the men too high so we used ladders.

We revamped the process several times as we worked through the house.  The first loop we measured and drilled the holes, ran the tube and stapled the plates.  Doing it this way allowed us to be precise, but it was slow and there was quite a bit of time where Emily & I had nothing to do.  So while Rob, Mark and Dad were working their way throught the second loop Emily & I realized that we could help get a little bet ahead and started to mark the spots where we would need to drill through the joists.  We also marked out where each loop should start and begin and added a couple of arrows here and there to signify which way the loops needed to run.  Then, the person with the drill followed us and then we got the tubing up.  Rob realized it would be a more efficient use of our time to run all the tubing and then staple up the plates.

It was quite a team effort to get the tubing up.  Mark likened it to lacing a shoe.  We'd have one person managing the tubing at the uncoiler, one or two people managing the tubing in the yard or in the house (depending on where we were working), and someone managing where the tube was running through the joists.  Then we had to approximate the correct amount of tubing to run down each joist and back again.  We also had to keep track of where the tubing went in and out through the walls.  Amazingly, we only wrapped the PEX around a stud one time. 

We did have to revamp a couple of loops, but overall Rob's plan worked pretty well. 
We were so grateful to family who came to help.  Rob and I COULD have done this by ourselves but it would have taken so much longer.  Thanks to Steven, Granddad, Grandma, Karen, and Mark and Emily.  Bryce & Laurie brought over a nice tall ladder and let us borrow their air compressor and pneumatic stapler, which ended up being a lifesaver for us. 

Green paint represents walls between rooms upstairs.Red paint indicates areas that we didn't need to heat.  The pink numbers tell us where to stop and end each loop.  Rob thinks I had way too much fun spray painting the house.  Emily and I did "tag" it in a couple of spots and he was not amused.

The straight tubes are supply and return lines for kitchen loops.  An advantage of drilling through the joists is that it holds the tube up and at the height we need.
Depending on where we started running the tubing, some of it "hung" in between the joists and some of it fell to the floor.  The family room looked a bit like a bowl of spaghetti at one point.

Once all the tubing was in place we went back through and stapled up the plates.  Then we worked together to lift and place the tubing, adjusting for tension and length as needed.  At one point we had three ladders standing next to each other spaced two joists apart.  Rob, Emily and Mark stapled up four (or six?) plates and handed off the stapler to the next person, then they would move their ladder to the front of the line and get ready for the next hand off.  It was a pretty effective way of getting a lot done quickly. 

It would have gone much more quickly if we'd been able to staple directly to the sub floor.  We actually did that in three or four places where the corners were just a little too tight.  When we told Justin we did that he asked us to mark the area on the subfloor above it. 

This picture shows the transfer plates stapled to the top of the joists and one (cut in half) stapled right to the subfloor.
These guys worked so hard.  I was uber impressed with Rob.  He manhandled every inch of tubing that went up, sometimes two or three times.  He pulled and pushed it through the holes in the joists, he coaxed it around tight corners and just kept going.

Doesn't this make your neck sore just looking at them?
A finished loop!

Rob went back after he dropped me off at the airport and built a box to control the chaos of the tubes coming into the mechanical room. Isn't he clever?

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