Part 3: Low Voltage Power Boxes
I live in a bit colder of a climate (49° N), so I’ve been a bit worried about heating in the winter time. Through my research, I’ve found that there is a huge correlation between airflow and moisture control through the walls. Some of the research even said that you could go with less insulation if the building is well sealed. So I’ve decided to air seal the building as well as I can.
A large part of air sealing is using air sealed electrical boxes. These boxes have flanges on them to help attach the vapor sheeting that will go over the insulation. I purchased some for the AC electrical system (see Part -1: Electrical for an overview of my electrical system design). While I could use them for the DC electrical system, they were $3 at the time of purchase which was a bit too steep to get for the entire DC system. As my system is similar to The Tiny Nest electrical system, I looked into using the same vapor boots that were used in their build. However, since The Tiny Nest is based in Canada and the local building codes are different than in my area, none of the construction stores in my area carried them. I found them online, but the price was even more than the AC vapor boxes and came in boxes of 100. So, like most things that I think are too expensive to buy, I decided to manufacture my own.
I did a bunch of research into manufacturing techniques for plastic boxes. Adam Savage has a great video on finding a small thermoforming machine that dental offices use that he uses for small prop making. I designed and 3D printed a couple of forms to use, and went about some experimentation.
It ended up that really hot plastic being formed around 3D printed parts melts the 3D printed parts. I used some aluminum tape and taped a piece of cardboard to the top of the 3D puck to keep the heat a bit more separated. This seemed to work pretty well. I made about forty of these for both the LED can lights and all of the DC power boxes in the walls (mostly for LED strip lighting). I trimmed up the excess plastic and was ready to install.
The power boxes were a bit more brittle than I was hoping on install. When I cut a hole to pass the wiring through, the hole tore out and it defeated the entire purpose of building this boxes: vapor tight barrier between the inside and the outside. However, I tried some duct putty that I had purchased for passing wiring to the exterior for the mini split unit and the tankless water heater and that seemed to help prevent or lessen the tear out. There’s not a ton of room in the boxes, but it’ll be enough to install any of the LED strip lighting wiring or the “dumb” switches that I’ll be using here and there.
