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Energy retrofit gone wrong

BobHr | Posted in General Questions on

I was at a home on an unrelated issue today. In conversation he told me about some problems he is having after new insulation and air sealing.

The home is a split level. The front door is about 4 feet above the driveway/ garage level. This main level has the kitchen, Living and family rooms. The bedrooms and bathrooms are above the garage so about 4 feet above the main level.

In the last year he had a new furnace installed and the return vents in the basement were sealed. The insualtion was removed. Owens Corning spray caulking was applied for air sealing and fiberglass blown in. In the garage any seams along the perimiter were sealed. In the basement a bead of caulk was run where the sill plate and concrete meet. The rim joist has not been sealed or insulated as owner will do it himself. New vinyl replacement windows

What started our conversation was his complaint of a lot of dirt coming from several ducts in 2 bedrooms. Oh the duct work was cleaned, The owner had sealed the duct boots to the floor.

The home was built in 1972. The builder installed soffit vents but the flow was block to the attic. Effectively no venting. This was opened up and the rush of air blew a lot of dust in to the house and attic. He links a lot of the problems to this. Ridge vents were installed but some how he claimed that it was causing a down draft in the attic and they were replaced with turbines. Now he contends they can smell something in the house when it is not windy.

When the furnace blower is turned on you can noticeably increase air flow by opening a window. This is just in the bedrooms.

The attics between the main floor and bedrooms are connected. The attics are accessed from a sidewall hatch in a bedroom.

The main floor ceilings are flat. The family room has 4×4 rough cut decorative beams. The owner has reported he gets a smell in this location too. He knows the drywall is not sealed at joints above the beams. He has started sealing from inside with caulk along the edges of the beams and notes an improvements.

Prior to the work a full audit was done with blower door, infrared etc. The auditor was out when the attic was being sealed.

The basement is unfinished. All duct work was visually in good condition. The basement ducts are in no way connected to the outside. Condensing furnace and electric water heater. Old flue in place but capped in the basement.

One last thing. The mechanical chase running up the sidewall of the garage had been open but it has been sealed at least at the basement ceiling level.

What are you thoughts as to what needs to be done. What is the cause of low HVAC flow to bedrooms with window closed? What can he smell something from the attic when the wind isn’t blowing. Any other thoughts and comments welcome.

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  1. Natur Haus | | #1

    I have been told by a ventilation industry expert that if the cubic inch ventilation is larger on the ridge than it is at the eave/soffit, then you can get reverse flow. The chimney effect at hand, large in, small out naturally works. My thought is that the continuous ridge venting was too much NFVA for the 70's "every once in a while" eave vent blocking, usually at 4' O.C. The new turbines are back to not being enough, they should have increased eave venting rather than decreasing ridge venting. Other than that, I think that trying to tighten old houses, while maintaining pressure equalization and effective tightness is a TALL ORDER, and I think most contractors are chasing the money instead of learning building science and understanding buildings. JMHO.

  2. Natur Haus | | #2

    Is the heat pump/AC in the attic?

  3. Natur Haus | | #3

    The window closure/ low pressure is due to the homes pressure not being equalized.

  4. GBA Editor
    Martin Holladay | | #4

    It's time to call in a home performance contractor. The home needs a Duct Blaster test to see if the duct systems are leaky; this will allow the ducts to be sealed and the supply and return systems to be balanced. It's likely that the ducts are leaky and the systems aren't balanced.

    It's also likely that the home's thermal envelope still has leaks; it sounds like the attic is partially connected to the home. Solving that problem requires more blower-door-directed air sealing.

    Locating and sealing leaks in old duct systems and old homes is tricky -- it often takes several visits (and sometimes near heroic efforts) to solve problems like the ones you describe.

  5. davidmeiland | | #5

    If I got involved in that, the homeowner would have to surrender his scope of work to me. Steps taken would be blower door guided air sealing, duct blaster test and duct sealing, improvements to room pressures when blower is running (undercut doors, jumper ducts, possibly more return registers, a once-over on all the insulation details and review of the attic venting details. Pretty normal stuff.

  6. BobHr | | #6


    Each of the bedrooms have returns. From the basement I could see 4 panned in returns for the main floor dumping into the trunk line. Then there would be 3 for the bedrooms. Bedroom doors were open too.

    My thoughts are that he has a supply leak in the ducts that run between the garage and the bedrooms above. Thus when when the blower is running air is being pumped out of the house and the system is starved for air. When the window is opened the air handler gets the air it needs.

    I also think the turbine roof vents are depressurizing the attic. Obvisouly there is an air leak in the family room ceiling that didnt get fixed.

    The trunk lines serving the bedrooms go up through a chase in the wall between the garage and the house. If this was not sealed at the top then the bedroom floor/garage cieling is connected to the attic thus influenced by the turbines.

  7. BobHr | | #7

    I should add about the soffit vents. The new soffit vents are vinyl. They have recessed slot/holes spaced in rows about 4 inches apart.

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