Questions about ambient temperature and freezing pipes

cellophane

as i've mentioned before i'm having contractors do work on the house i bought to get it up to the point where it's livable & move-inable. part of this involved fixing some plumbing and installing central air. while the work is going on i have had the thermostat set around 55 which if you are working isnt terrible. weather has fluxuated quite a bit here from 15 to 60 in the last few weeks.

at what temperature should the thermostat be set at to prevent pipes from freezing? i would think that with the air at 55 it would be fine but that doesn't seem to be the case. thankfully the water has been turned off for a while and the amount of water in the pipes is pretty minimal so rather than bursting there are just some small leaks at the ends of the stub ups. It seems silly to have it set to 70 when no one is there but at the same time pipes breaking would be pretty bad...

the exterior walls are not insulated (on the list of things to have done) and are plaster on lathe / 2x4 / wood siding / aluminum siding (installed over original wood.)

the air system is currently one system in the basement piped to the 1st floor heating everything. the 2nd floor is not installed yet.

Yoyizit

My 'stat goes down to 45 F, minimum, for the stated reason of preventing freezing in some parts of the house.

This setting probably assumes a reasonably insulated house but on cold nights with the 'stat set at 65F the pipes under the kitchen sink may very occasionally freeze if we don't leave the kitchen cabinet doors open.

Finding the 97.5 percentile cold temp for your area on the Internet may prove challenging. It's probably in the 2000 IRC or later versions.

Scuba_Dave

This can depend a lot on where the pipes are located
And if the water isn't in use the it will be more prone to freeze
Stub-ups - cement slab ?

cellophane

pine over 2x10's - the plumbers went through and replaced a lot of old galvanized pipe and corroded cast iron and have not attached new fixtures yet.

the basement is temporarily heated until some concrete is cut to run a supply line (supply is just venting directly into the basement), all the water pipes unfortunately run up exterior walls - which is probably the issue...