This week the big excitement was finally pouring the concrete for the downstairs floor!

The guys from Atlantic concrete with the truck and the pump

The concrete being pumped into the living room area

The guys hard at work

Floating the final finish

The final product setting up

After much back and forth, we decided we’d use wet “stamped” grooves for our crack control joints rather than having them cut with a saw afterwards.  The saw cuts would be a little less conspicuous, but they wouldn’t go all the way to the wall (the problem with round saw blades…).  The choice of wet grooves means the control joints are rather large, but we’ve seen places that have grouted the joints, and gotten beautiful contrasting lines.  In about 2-3 weeks after the concrete has had a chance to fully set up, it will be acid stained and sealed, and should be mirror finish.

If you’re going to be on a concrete slab anyway, concrete flooring is about the lowest energy flooring you could use, as you aren’t adding anything but sealer.  It is still pretty good if you already have a plywood sub- floor (like on a second story) as, per square meter, it has about the same embodied energy as hardwood… but there may be other considerations I haven’t thought of for second story concrete floors.

If you want to put something else on top of your concrete or plywood sub-floor, the energy adds up:

stone tile 3 kWh/m^2 (+4 kWh/m^s mortar bed)

3/4″ thick solid hardwood flooring 8 kWh/m^2

3/4″ thick concrete floor 9 kWh/m^2

engineered wood flooring  28 kWh/m^2

plywood underlayment 28 kWh/m^2

ceramic tile  30 kWh/m^2 (+4 kWh/m^2 mortar bed)

carpet (synthetic, including pad) 181 kWh/m^2

Wow! carpet…

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The PEX tubing for the hydronic heat being installed. Next week, the concrete floor will be poured, and this tubing will be embedded inside

In our current two-story townhouse, we always struggled with balancing the internal temperature throughout the house.  During the winter we were always trying to close off the forced air vents in the upstairs bedrooms (as we all like to sleep in cool bedrooms without super heated desert dry air blowing down on us).  Short of taping the ducts closed, however, we were never very successful at keeping the hot air from blowing into the bedrooms, so we hired some HVAC contractors and had them split the heating and cooling into two separate upstairs and a downstairs zones with separate thermostats and separate ducting.  What a wonderful difference this made!  After a few years of living with the two zones, we have discovered that not only do we never turn the heat on upstairs during any season, but that even if we only heat the downstairs, we often *still* have the bedroom windows open to keep them cool enough to sleep at night.  Yes, warm air rises.

"Warmly Yours" electric heating mat being embedded in Natalie's bathroom floor

I suppose if we were smart, we’d put the bedrooms all downstairs, and the living spaces upstairs, but maybe in the next house we build (ha ha).

For this house, we decided that given the large central stairwell, and the extremely open upstairs floorplan, we would only put hydronic heat in the downstairs concrete floors, and count on the HRV (Heat Recovery Ventilation) system to keep the air circulated during the winter when it is cold enough to shut the house up tight.

The only heating upstairs we are putting in are electric warming mats embedded underneath the stone bathroom floors. Because the bathrooms are the farthest from the stairwell, and also we tend to like the bathroom a bit warmer than the bedrooms, we decided we should heat these.  (Not to mention that cold stone floors are quite unpleasant under bare feet! )

The energy we will use for two heated floor bathrooms if we heat the floors for two hours in the morning, and two hours at night is about 1 kWh per day.  We have the same type of floor warmer in our current bathroom on a similar schedule with a programmable thermostat and we have found that we use it from October through May (8 months of the year – interestingly more of the year than we use the central heat).  Assuming we do the same thing with our two upstairs bathrooms in the new house, this puts the bathroom floor heating in the 250 kWh per year range which is about 1/100th of my estimate of the space heating requirements of the old house, and about 1/15th of my (hopefully) generous estimate of what the space heating requirements will be for the new house.

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The cellulose being blown in

Feeding the hopper

After the radiant barrier was all installed, it was time to put in the wetpack cellulose insulation.  At 86 MJ/m^3 , it is a much lower embodied energy insulation than either fiberglass bat (336 MJ/m^3) or the polyurethane insulation (2160 MJ/m^3).  While it is not quite as high a performance an insulation as the polyurethane, we are installing it in 6″ thick walls which means we’ll have plenty of insulation with its R value of 3.7 and its nice ability to fill in all the small spaces around wires, pipes and electrical boxes.

Blowing it in is a messy job with one guy spraying the cellulose mixed with water, binders and a fire retardant into the cavity, and another guy sucking up the excess to be run through the mixer machine and blown in again.

Down at the truck is the machine that powers all of this with another guy busy dumping in more cellulose mix into the big hopper feeding the blower hose.

When the cavity is finally filled, it is leveled off and left to dry.  In thin areas, the cellulose is blown in behind a mesh to keep it in place.

In one place in the house you can see the three major types of insulation we are using – cellulose, straw bale and foam insulation all meeting up in one spot.

Where three types of insulation meet

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