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: 685

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.

Latest Activity

peter chang replied to Damien Greenfield's discussion Is there is cost saving for you in having a tankless water heater?
"I think it is quite possible the greatest savings will be realized by the lowest volume users. I…"
15 minutes ago
Marie Fuentes is now a member of Home Energy Pros
17 minutes ago
peter chang replied to peter chang's discussion Programmable tstat for electric baseboard?
"Good plan, thanks. That looks pretty much like how I used to program mine (when I had one). Maybe…"
48 minutes ago
Bob Blanchette replied to peter chang's discussion Programmable tstat for electric baseboard?
"Since the sun heats the house to 78f during the day, cutting the power from the time you leave for…"
2 hours ago
peter chang replied to peter chang's discussion Programmable tstat for electric baseboard?
"Yes, in fact I did just that for my kitchen toe-kick heater because the original thermostat was on…"
9 hours ago
Bob Blanchette replied to peter chang's discussion Programmable tstat for electric baseboard?
"Savings depends a LOT on how it's programmed. I've even done a setup with a contactor,…"
16 hours ago
Bob Blanchette replied to Hal Skinner's discussion Any success getting landlords to energy upgrade a single family rental unit?
"Sell utility subsidized services to the tenants. It has to pay back within a year though."
16 hours ago
Tom Mallard replied to Hal Skinner's discussion How much heat energy is lost through the floor of a house?
"Thx, Robert. Being a PNWester where crawl spaces are moist or wet seasonally & some sites never…"
19 hours ago

© 2014   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service