Sunday, December 15, 2013

Low and High Voltage CAN go in the Same Box

All our lights are low-voltage.  I looked for boxes for the switches, but I was surprised to find the plastic LV boxes were expensive, and in my view, not that great.  I searched for a steel box and found one!  It is the Hubble product pictured below, the price is reasonable, (less than the LV mud-ring boxes) and the divider is removable (additional $1 for the divider), so the box can accommodate both regular household voltage and low voltage in the same double-gang box.  We used double-gang boxes for all our switches and plugs in the house - (almost all).  Most will have a CAT6 cable and an 18g. cable in the LV side, plus whatever goes on in the household current side.  From these, we can eliminate power adapters in the house by providing LV direct from the plug, and we also can use any 12V devices, and have DC lamps (so DC power direct to LED COB lamps).  DC-DC boost or buck pucks are available online now for about $5, so you can get almost any voltage you want by placing it in the box (we are supplying 28V), and it would remain within the electrical code rules as long the voltage remains below class 2 wiring limits.  In addition, every plug location becomes a data/voice/LV/automation/sensing/instrumentation node as well, without adding additional boxes all over the place.  So we can have things like motion sensing that controls things far away from the box, microphones, speakers, bluetooth, wifi, fire sensing, temperature, humidity, etc.
In many of the switch locations, there is no household current component, so the whole 2-gang box is for LV.

There are virtually no octagonal boxes in our project - Just one, actually in the utility room because I wanted to have a different source of lighting while the LV lighting system was being worked on.
You can see the LV wires come from above the plywood - they were incorporated into the acoustic floor assy above.  This could be done with 115V also, but you would likely need for it to be in conduit depending on the acoustic floor thickness.

Exterior Cladding is Finally Going Up

The exterior cladding is finally coming together, but its hard to photograph due to scaffolding, and the difficulty of getting a good camera angle.
We've made so many changes to the project it is no longer funny, so I've figured out now that one way to avoid changes is to build it fast!  Everyone seems very unwilling to change things once the money is spent and the construction complete.  Sadly, that is not our current situation!

Here's a rendering of what we are doing:

I offered to go up there and paint the roof white (because we both felt we chose the wrong colour shingles for it), but she's not keen on the white idea, so the brownish mistake will remain.  I find the house pleasing, though it is simple.

And here's a pic of the cladding going up:

Removable Basement Floors and Interior or Exterior Insulation Placement

A basic decision that one faces early in the design of a super-insulated building is the strategic choice of interior/exterior insulation placement and thermal mass.  This a strategic decision because it has far-reaching implications and ripple effects.  Think of the building as a shell on all sides, including the parts in the ground.  If we are designing an airtight envelope without thermal bridging, then we want to avoid having some of the insulation inside, and some on the outside - it can be done, but this frequently leads to thermal bridges and sealing problems.  For example, if we have insulation under the footings, (this being outside the structure of the shell), but then we want to have insulation inside the basement walls, how to connect the insulation under the footings to the insulation inside the basement?  The problem is there because in general, insulation materials are weak and soft, while structural materials are hard, but conduct heat.  To simplify the design and construction greatly, and improve the effectiveness of the insulation system, work to have all the insulation either outside the shell, or inside the structural shell.  Cross-overs are to be avoided.  In our case, we decided to place all the insulation inside the shell, and forego the thermal mass benefits - I believe thermal mass benefits are less well proven than insulation benefits, and that 'thermal' mass can be achieved without 'mass' (for ex. by the use of water - a very thermally massive material without much mass, that can be moved around).  
SO, here are more photos of our basement floors - they are above all of our interior insulation (about R55, or 15" of Roxul) above our basement concrete slab.  As posted earlier, they are removable, and they are a common material - regular construction lumber 2x12.  which means we can remove and replace pieces, but we can also remove and look underneath.  We're currently pretty happy with these floors, and the system feels very solid to walk on - as if the floors were resting directly on concrete.  It turns out the wood has shrunken a little in the 2 months since we installed it - but only the pieces that were wetter.  those nice planks in the 2nd photo have not shrunken at all.
Some astute observers have commented that the floors will allow moist interior air to go into the spaces below the slabs.  What will happen to this moist air when it reaches the cold concrete some 17" below?  Well, we have Tyvek under the floor boards in one area to prevent this bulk movement of air, but most of the floor is left without any kind of air barrier.  Since it is removable, we can make a correction if this turns out to be an issue, but I have a feeling the issue is fairly minor for a couple of reasons.  If we think of regular basements, many have no insulation under the concrete floors, and they are perhaps a bit damp on muggy, hot summer days, but often this problem is short lived in the Toronto climate.  In our case, there is a floor assembly blocking the bulk movement of air to some degree, and in addition, the space beneath our floors may be warm for much of the summer due to our under-floor (sub-slab) heat storage strategy.  This raises the temperature of the basement concrete slab right when the chances of hot moist air condensing on it may be highest, which should reduce that whole issue quite a bit.

However, as there could be a small concern, we did place some sensors at the bottom of the floor insulation, in three locations.  The photo below shows a small pump with tubing, a water level sensor, and a temp/humidity sensor in the background.  The sensors are inexpensive devices for Arduino, and cost about $5 each.  The pump was from Princess auto and was about $20.  We had some problems with our basement floor pour - there was not enough slope in some areas, and during the big Toronto flood in July 2013, we noticed a little water in three locations on the floor, and so marked these spots and placed these little pumps to transfer the water to the sump pit.
Later on, as the systems become live, we will be able to report the fluctuations in temperature and humidity at the bottom of our basement floor assemblies.
We will also probably place sub-slab soil temperature sensors as well, one day...