Ready to pour the floor

The last week since my last post we've worked really hard to get ready to pour our basement floor.  Not many pictures but some really interesting stuff and a lot of money out the door.

Last week our GeoStar Mechanical finished drilling the loop for our geothermal system and brought the main lines into the basement. Our flatwork contractor wanted that done before he finished compacting.  The drilling process is actually quite interesting.  The shape of the bit allows them to essentially drive it fairly accurately to a given end point.   They have a locator that operates something like a stud sensor so they can follow the tip.  When they were describing it to me my programmer's brain was picturing a little robot with a drill head on it but the mechanism is actually much simpler.  The tip is shaped something like a duck bill, flat and angled in one direction.  So when it moves forward it will go in the direction the point is facing.  To make it go straight they simply start it spinning.  The tip is connected to a steel pipe that can bend to a certain extent over long distances.  When the tip comes out of the ground, they simply attach some pressure cuffs to it(think Chinese finger puzzles) and pull the tip back, thus pulling the pipes for the ground loop back through the hole and up to the drilling rig.  With this mechanism they were able to drill all 6 loops in less than 8 hours through ground that we probably couldn't have gotten excavation equipment into anyway.

So why not just use traditional excavation and slinky coils?  There are a few reasons we decided against that.  First, the horizontal boring allows us to put the pipe down 10' or more.  The deeper the pipe the more consistent the temperature of the ground and thus the better they can calculate the loads required to heat a house.  If you do a geothermal loop wrong it's a pretty big mess and you won't get sufficient performance.  I think anyone would be pretty disappointed to spend $30k on a heating and cooling system that didn't heat and cool the house.  So depth was one reason.

Jamie from Geostar Mechanical drilling the ground loop.

Another reason is the ground composition.  We have what could be politely referred to as some pretty soft ground.  In the spring we won't be able to drive a lawn mower in there and a 4 wheel ATV may even have difficulty.  In a drier summer the surface is usually fairly dry but still soft.  This summer the ground just dried out the standing water before they started drilling.  Bottom line, if you take excavation equipment in there its likely you'll get stuck at least once.  Along with that is the fact that the trench would be full of water almost as soon as you start digging.  The fact that the excavator wouldn't be able to see the bottom means he wouldn't be able to get it smooth enough to prevent the kinds of uneven-ness that could cause the lines to break and create a huge mess.  Can you imagine total failure of your system because the pipes broke as they were being covered up?

But the wetness that causes the problems is the very reason I wanted to put the loop out there.  You get the best of both worlds between a closed pond loop and a ground loop.  The greater the conductivity of the ground, the greater the ability to both heat and cool.  I have heard great things about the kinds of efficiency you get out of geothermal, I am excited to see how mine performs given the choices we made so far.

The next thing we did this week was lay radiant floor.  Never done it before and I have to say that it was harder than I thought it would be.  It wasn't terribly physical in nature, and maybe I made it harder than it should be, but I put a lot of thought into how to lay out the pipes and a) I miscalculated the square ft and b) I blew the layout anyway. 

Side note... and this bit me both in materials both for insulation and radiant floor, when you buy materials make sure you calculate the sq ft on inside dimensions for the area you are actually going to do something with.  I had outside dimensions on my print and figured, "eh, how different could it be."  This is why I did very poorly in math.  Think about it, 8" walls on both sides is 16" multiplied by the length of the wall and you start getting some fairly significant dimensions if your walls are long.  By the time you over-order to make sure you have enough materials you end up with more than you can use.  It's alright, we can still use it, but now we're going to have radiant flooring in the kitchen and main bathrooms too.  I would be a lot more disappointed but I got a great deal on the materials going through Geostar so I'm not so horribly disappointed.

Our first try we failed our inspection but it's not really fair to say it's our fault.  My dad who's 80 years old and can still work way harder than I can... who worked tirelessly with me all day until about 10pm on Sunday and late into the night on Monday getting all the pipes connected to the manifold... who worked on it by himself while I had to go to work the last couple days was unable to get the system sealed up.  For those who don't know how this works, the system has to be able to hold air pressure in order to pass inspection.  Our system kept leaking air and he was unable to figure out where it was coming from.  He thought he had it sealed up but when the inspector came all the dials were at 0.  The problem is, he can barely hear and turns off his hearing aids because they whir in his ears whenever he bends over.  It just so happens that the pressure release valve in the test gauge was loose when it came from the factory(think the pin inside a tire stem) so it was leaking air.  Well, leaking is a bit of an understatement.  With his hearing aids off he couldn't hear the air gushing from the valve and thus it didn't hold any air for the inspector to see.  Fail.  So this morning I stopped down to the site before work and we got that all fixed up and, 24 hours(and $45 in penalties later), we passed our inspection and are now ready to pour. 

Special thanks to the crew from Hunt & Nieboer Concrete for prepping the surface and laying the slab insulation.  They should be out here pouring our floor by the end of this week or early next week.  Once the floor is down, it's time to backfill and then we finally get to the framing.