Life At Villa Boswell

This has truly been an exciting week @ Villa Boswell. It’s Saturday and our radiant floors are in! That means that insulation can begin and after that, drywall. We’re pretty excited about wrapping this place up in time for Christmas. But, I get ahead of myself. First, here’s the scoop on what goes into radiant floors.

First, you need radiant barrier foil. This is essentially a shiny foil-like barrier that is applied to the surface of the floor before any of the radiant tubing is put down. Shiny side up. It was developed initially by NASA for astronauts’ suits, and it’s a fundamental part of any radiant heating system. You can read more about how radiant foil works by checking out this fact sheet, or by searching on the topic.

After researching radiant barrier foil, I was highly intrigued by this material. Some people ask, "Is it worth it?" In fact, the phrase "is radiant barrier worth it" was a suggested search on Google. Essentially, heat loss or transfer occurs commonly through two means: convection (or air movement), and radiation (or emission). Conventional insulation helps reduce heat transfer via the first means. For radiation, it turns out that anything with a highly reflective metallic surface ends up with a low "emissivity" rating, and that’s a good thing when trying to keep things either warm or cool. Since feeling is believing—I tested out two types of radiant barrier foil, one shinier than the other. I placed small sections of each foil type on top of a piece of thick styrofoam, and put my bare foot on the part of the foam not covered by the foil.  Baseline: fairly cool.  Then, I put my foot on top of the shiny foil, and immediately I noticed that it felt like an electric blanket. Then, I tried the less shiny foil, which initially felt cooler but then warmed up as well. Pretty cool, huh?

Ok, so now the radiant foil was place all over the floor. Essentially, when the radiant tubing heats up the concrete, the foil will keep the heated floor from emitting heat downward into the garage/utility area. All the heat will be reflected upwards.

The next step was to put down the tubing. We used Pex tubing, which is an industry standard for radiant floors. Pex tubing comes in a number of variations, depending upon the particular application. We used the Pex-Al-Pex tubing, which has a central layer of welded aluminum, over which is bonded cross-linked polyethylene.  Of course, putting down the tubing only represents a small part of the overall system, and the actual work involved in putting in the tubing (1 day) was a fraction of the time spent by Chris designing the layout of the tubing and the three radiant zones for the house. Here’s a shot of the tubing already in place in the master bedroom.

 Below, you can see the view to the dressing room and into the latter part of the master floor.  The tubing is stapled to the floor by brackets, and every so often we used metal "z-bar" as the necessary supports for screeding the concrete once it’s pumped onto the floor.  Typically, most radiant heating guides suggest using wood boards for screeding, but they then have to be removed and the vacant area filled with concrete later on.  This way, we could simply leave the metal bar in place once the concrete work was done, saving us an extra step.  This tip thanks to my great mother-in-law Lora, who learned it from a friend.

 If you look closely at the picture above, you’ll notice that there are two colors of paint used to mark the layout of the tubing.  This is because the radiant system is a closed circuit, and each tube is part of a loop system that returns to the zone manifold, pictured below and shown with all the colors of the circuits for the master floor zone. This manifold is located in the master bedroom closet, which is going to be a pretty warm room!  I bet anything Bart hangs out there a lot.

 Well, Ok!  Part 1 of the radiant floor work began and wrapped up in four days.  Now, two things that I hear ALL the time from people when I mention that we’ll have radiant heating:

1. Isn’t it expensive?  Yes, it is.  However, by doing the work ourselves, we saved a tremendous amount of money.  First, although we paid probably $3K just for the initial radiant heating plan, Chris ended up re-doing it beyond recognition of the first plan, taking care of subsequent design modification costs.  Secondly, we also saved a LOT of money and a LOT of time using Pex instead of copper, which is considered the "gold" standard.  However, copper is super expensive because of both material AND labor involved in connecting and sweating all the sections, which must be done perfectly.  With Pex, the tubing can be bent to any shape you want; it’s like a soft metal extruded tube with plastic sheathing.  Hook-up and subsequent pressure inspection passed perfectly.  No joints, no faulty connections to fix later on.  Anyhow, we figured we saved 10-15K this way.
2. Doesn’t it break? What about all those Eichler homes?  Ok, so first, this quote directly from the Eichler Network: "Properly maintained, with regular inspections, your Eichler radiant heat can last for decades. To be honest, it will probably be keeping your house warm far longer than you will be in it!"  Basically, some Eichler radiant systems were put in with steel tubing, which can corrode. My mother-in-law built her house 45 years ago in the Santa Cruz mountains with radiant heat copper tubing.  We just visited the current owners of the house this summer, who reported happily that the radiant heat is working fine.  Bear in mind, the only repair needed within 45 years was after the Loma Prieta earthquake, the epicenter being a few miles from the house.  There was one small leak that was easily repaired. I tried doing a search on radiant heat repair, but basically all I can find is that it should last indefinitely, provided the pressure is properly maintained by the boiler.

This entry was posted on Saturday, September 13th, 2008 at 5:29 pm and is filed under El Granada, Architecture. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.