On a recent quality assurance site inspection I found a situation where pipes froze and burst within an interior wall. Here is the story:
In my experience, I am skeptical that such a complex condition could be anticipated by even the most seasoned home performance contractors, but I wanted to see what the experts think about this. In my judgement the improved air sealing and insulation caused cold air from the un-insualted flat roof to pass through interior wall chases toward the basement because of negative pressure (both furnace and water heater are atmospheric draft).
Addition in back with flat roof
Crawlspace insulation below addition. Water heater is directly to left of frame.
Wall where pipes froze (bathroom is on other side of wall)
Bud finally nailed it, if there is low enough temps and air flow the pipes are toast
As for your the air sealing, insulating, foreseeing it questions - to hard to answer as we don't have all the facts, know the path that this occurred, etc... Shoot it could have been something the HO did after the fact
I may not have read the description carefully enough, but it sounds like the new insulation may have reduced the flow of waste heat from the water heater to the area where the pipes froze.
Thanks for the thoughtful replies!
Bud: Considering that the bulk of air sealing work in this house was done in the basement, it is very likely that the NPP moved as a result. Unfortunately, I wasn't able to perform any diagnostic testing on the house to identify where air may have come into the house - and in any case, the repair of the wall and added ceiling insulation have likely changed the air leakage pathway once again.
Sean: Given the timing I doubt it was something the HO did himself, however it's not 100% out of the question since he is finishing his attic space.
David: It's hard to say if waste heat played a role here since I can't get a good reading on the size of the wall chase that was sealed up.
Are you certain there is no missed chase-electrical or plumbing- that goes to the attic that was missed by the contractor?
The location of a water pipe break can be quite a distance from the point where it freezes. Was it possible to find the location of the freeze? This would be instructive because it would give you the point where the cold air hit the pipe, and therefore make it easy to find the location of the air path. I suspect once the wall was opened the freeze thawed. When the wall was opened, could you feel air movement? Did you have the opportunity to use a blower door on it before it was closed up again? Is the flat roof over the porch intentionally ventilated?? Unintentionally?? Is the house balloon framed? Could you seal the attic at the eave right over the frozen area? What is the indentation in the wall in the third picture - was a second shallow wall added to the inside to allow thickness for a plumbing stack to go up that wall? Is it the same wall jog on the second floor above this one?
I'm a water damage mitigation specialist with Paul Davis Restoration in Madison, Wisconsin. The combination of extreme cold and wind would be enough to cause freezing if air sealing was inadequate at the junction between the addition and the original structure. This type of damage is almost always correlated with extremely low wind chills for us here in Wisconsin.
Three weeks ago I had a project at a restaurant with multiple pipe breaks inside interior walls. They had work done on a large vent hood in the kitchen which caused depressurization of the conditioned space. Cold air was sucked down from the attic through air pathways following electrical or other mechanical openings. Pipes broke inside walls in the middle of the restaurant. The attic was well insulated (= cold) but there were several air bypasses down into wall cavities.