Frozen Pipes on Interior Wall

On a recent quality assurance site inspection I found a situation where pipes froze and burst within an interior wall. Here is the story:

  • The homeowners have been in the home for 14 years. The home is located in Grand Rapids, Michigan.
  • They contracted to insulate exterior walls, rim joist, & crawl space & perform air sealing in November, 2012. Blower door testing revealed a 25% air leakage reduction. 
  • They witnessed water damage after a long cold spell in January on an interior wall between a small addition space and the main house. The home's water heater sits directly below the area where the water damage happened - it is atmospherically vented. The addition is built on top of a shallow crawl space that was spray foamed. 
  • They added insulation to the small flat roof section at time of repairs for water damage. They did not think to contact their initial insulation contractor in regard to the water damage.

My questions

  1. Has anyone else seen water damage from frozen pipes on interior walls as a result of insulation/air sealing.
  2. Is there any way that the initial contractor could have potentially foreseen this situation.

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).

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Addition in back with flat roof

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Crawlspace insulation below addition. Water heater is directly to left of frame.

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Wall where pipes froze (bathroom is on other side of wall)

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Replies

  • Hi Nick,

    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.  

  • 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?

      Good luck

  • 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.

     Thanks again,

    -Nick

  • 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.

  • The total stack effect pressures are a function of height and temperature differential so insulating and air sealing does not change the starting point. However, our work can shift the NPP and result in an increase in pressure across a leakage area that previously wasn't quite bad enough to freeze that pipe.

    Example would be a hole near the NPP which would see little air flow. Air seal the lower portions of that home and the NPP will shift upwards attempting to increase the lower air flow and decrease the upper so the "in" and "out" will again match.

    I've seen pipes 6' inside a home freeze because they were in a path of cold air flowing in, so pipes don't need to be on exterior walls to freeze, just isolated from the heat and exposed to a source of cold and, adding insulation can have this result.

    I agree, difficult to predict however, our training is lax in the area of passive air flow and a good understanding of stack effect and the NPP might have predicted/prevented this problem.

    I would need to see more to form a good opinion, but I would doubt that the basement could be that negative so as to pull cold air as described. If it were that negative the atmospheric appliances would have been venting into the house.

    Bud
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