Hello energy pros.

I need your combined wisdom before I proceed to help a client of mine address what appears to be mold growth and draftiness after I completed attic air sealing and other miscellaneous measures on her home.

The HO owns a split level in Northern VA. She, her husband, and three children have lived in this house for three years.

The house has existing exterior wall insulation, and some attic insulation. No rim joist air sealing or insulation and no foundation wall insulation. 

We sealed the entire attic above the two-story section of their split level (above the bedrooms), and replaced the existing blown-in fiberglass. We also insulated a section of exterior wall in their laundry room that was driving discomfort in their house with closed-cell spray foam. Finally, we insulated the floor between the 1st and 2nd story (between bedrooms) for sound attenuation purposes.

About one month after completing the work the HO e-mailed me to say that surface mold had begun to form on the exterior wall of the 1st story bedroom that we insulated the ceiling above and adjacent to the wall we spray foamed. This is the main concern at this point.

Before I run over there later this week and try to determine what is going on, I'd like to tap the knowledge that you all bring to the table.

My sense is that there is cold air rushing into this exterior wall through the rim joists in the basement. The cold air is mixing with warm conditioned air that is leaking into the walls through outlets and baseboards, and the air sealing of the top plates is keeping the air in the walls, but also allowing cold air to mix with warm, introducing condensation within the wall.

The HO also mentioned condensation on some of the glazing. One final detail I want to mention is that they have a gas insert in the 2-story section of the house (on the 1st floor).

Any ideas on what may be taking place, or tips on how best to proceed? 

Thanks in advance!

Views: 708

Reply to This

Replies to This Discussion

Thanks Kevin.

You leave me with a lot to consider.

I will likely need to follow-up on the matter.

Good point on the gas insert. Those do put out a lot of moisture.

 

The condensation on the windows is a clear indicator that humdity in the house is high enough to expect moisture accumulation on cold walls.

 

The question is whether the cause is a damp fall or a source in the house.

 

In my experience, DC houses that are weatherized don't typically have summertime humidity problems. AIr sealing sharply reduces the added humidity from infiltrating humid air. Since many projects don't improve wall insulation or glazing, AC loads don't go down all that much and dehumidification is adequate. In many cases the reduced humid infiltration seems to more than offset the lost dehumidification of lower runtime. In my experience anway.

Patrick, what is ACH50? ACHnat?

Where is the dryer vent located? Has it been moved or damaged during work? Was it inspected? Is the hose full of lint?

RSS

Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy,) and brought to you in partnership with Home Energy magazine.  Home Energy Pros is sponsored by the Better Buildings Residential Network.

Latest Activity

Hannah Finch posted a blog post

Want to Lead a Breakout Session at RaterFest! 2015?

We are adding something new to RaterFest! this year... attendee led breakout sessions on Saturday…See More
9 hours ago
Rod Fox replied to Rod Fox's discussion Does calcification affect electric water heater aquastat temperature sensor performance?
"We're in climate zone 5 (near Santa Fe, NM) where it's dry as a bone. Gonna head to that…"
10 hours ago
Bud Poll replied to Rod Fox's discussion Does calcification affect electric water heater aquastat temperature sensor performance?
"The two 4500 watt elements will never operate simultaneously.  It will be one or the…"
11 hours ago
Rod Fox replied to Rod Fox's discussion Does calcification affect electric water heater aquastat temperature sensor performance?
"Correction to this last posting... This model only operates one element at a time, not two in…"
11 hours ago
Rod Fox replied to Rod Fox's discussion Does calcification affect electric water heater aquastat temperature sensor performance?
"Agreed. Incidentally, I just called tech support at Bradford White (and actually spoke to a…"
11 hours ago
Hans Joachim Preiss replied to Rod Fox's discussion Does calcification affect electric water heater aquastat temperature sensor performance?
"Rod, Because the tank is not overheating, the behavior is either normal for this tank or there is a…"
11 hours ago
Rod Fox replied to Rod Fox's discussion Does calcification affect electric water heater aquastat temperature sensor performance?
"Hey thanks Hans. I didn't know about the benefit of the heatpump units having the elements…"
11 hours ago
Rod Fox replied to Rod Fox's discussion Does calcification affect electric water heater aquastat temperature sensor performance?
"I'm not sure if the tank was flushed at the time of element replacement. I would have hoped…"
11 hours ago

© 2015   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service