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Pipes freezing in bathroom. how to insulate

Our house has the master bathroom cantilevered over the edge of the house. the underside of that cantilever is covered with soffit material. I've had trouble with the pipes freezing once before, so i went up under the cantilever to see how the pipes were insulated. I found this:
There was prob r-38 or greater insulation in bats laying on top of the soffit. other than that, the floor joists that run front to back of the house were uninsulated, therefore, cold air was running down the middle of the house (which explains why my bathroom floor is freezing), and the cpvc pipes were bare and uninsulated.

I have considered cutting plywood panels to fix in between the joists to block airflow, and caulking and insulating. I also want to use pipe insulation on any pipes that are exposed. Do you all think this enough, or should i, in essence, stuff that hole area with insulation?

Re: Pipes freezing in bathroom. how to insulate

The misconception about insulation is it can prevent pipes from freezing if they are insulated either with pipe insulation or surrounded by batt insulation.
The fact is insulation only slows down the rate at which the pipes will freeze if they are exposed to freezing conditions. The thicker the insulation, the longer it will take the pipe to freeze. Batt insulation separating the cold from the pipe is worthless.
If you cannot create a conditioned space where the pipes are that will not freeze, your best option is self regulating heat trace. There are issues to contend with - powering it for one. And access to it in the future if it's in a finished area. This might not sound good in your case, but from experience I have found the commercial grade heat trace to be very reliable.
If you go this route, definitely insulate the pipe after heat tracing.

Re: Pipes freezing in bathroom. how to insulate

The space will never be conditioned. I think the space is fairly insulated, bc last winter we never had a problem with the pipes freezing. It just happened that this year on 2 separate occasions we had teens and 20s for a few days. It was then that they froze. I was hoping that by possibly doing a double layer of insulation that i could slow the freeze enough that hte weather would likely go above freezing and thaw them out. I have considered the heater but the issues that you brought up are the same ones that i have considered.

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