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

Malcolm McKelvie replied to Alan Gindt's discussion Minneapolis Blower Door System for sale in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"yes I would pay the delivery fee!"
Saturday
Alan Gindt replied to Alan Gindt's discussion Minneapolis Blower Door System for sale in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"Malcolm, If you want to pay delivery from USA we can talk. Otherwise no thanks."
Saturday
Malcolm McKelvie replied to Alan Gindt's discussion Minneapolis Blower Door System for sale in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"How old is it? I assume it is in good working order? I'm interested in it but the price needs…"
Saturday
William H Nickerson replied to Kim Tanner's discussion Fantastic innovation
"So that's where you use those True Flow plates....."
Friday
Colin Genge updated an event
Thumbnail

Passive House Testing Webinar with Kevin Brennan of the Passive House Academy at Online

September 29, 2015 from 1pm to 2pm
Tests needed to qualify as a passive houseWhy we’re seeing an increase in PH buildingsBest…See More
Friday
Colin Genge updated an event
Thumbnail

DM32 Smart Gauge 101 Webinar at Online

September 22, 2015 from 1pm to 2pm
Webinar Learning Objectives:Gauge settings and operationCalculate results in the gaugeUpdate the…See More
Friday
Colin Genge updated an event
Thumbnail

Blower Door 101 Webinar at Online

September 15, 2015 from 1pm to 2pm
See how easy it is to do your first test. Learn tips to perform your first duct test in only twenty…See More
Friday
Colin Genge updated an event
Thumbnail

Zone Pressure Diagnostics (ZPD) with Bill Eckman of NME$A Webinar at Online

September 10, 2015 from 1pm to 2pm
Benefits and limitations of Zonal Pressure Diagnostics (ZPD).Best practices for accurate…See More
Friday

© 2015   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service