ERV Installation

Thanks for the scoop Martin. Our system has the return duct (filter plenum) pretty close to the inlet on the air handler. The installation manual recommends to tap in to the return at least 10 feet from the air handler. Our geometry won't allow that so it went where it would fit. They are coming back next week to "balance" the unit since they left the flow meters at the shop yesterday during the install. It will be interesting to see if the system will balance properly with and without the air handler running.

You don't need to run the air handler in order to distribute air from the ERV--the ERV will push the air into the ductwork and it will find its way into the house, as well as out of the house if there is any duct leakage to outdoors.

The issue I would be concerned about is pressures in the ERV when the air handler is running. There is a significant negative pressure in the air handler ductwork on the return side of the fan, so it may suck extra air through the ERV, reducing the efficiency of the ERV quite a bit. Is there no way you can simply pipe the supply air from the ERV directly into the house, preferably into the bedrooms?

I'll report back after we try and balance the system next week ...

Adding extra duct work is possible just allot of trouble. If the system can't be balanced we will add dedicated supply ducts.

Just curious, how do they propose to balance? Does your unit have ports to measure pressure drop using a manometer, or are they actually proposing to measure airflow somehow?

If they can measure actual airflow with the air handler on versus off, that would be interesting. Please keep us posted.

They have flow collars that attach to the ducts. The ERV has adjustable dampers.

I just installed the Panasonic ERV in my attic bath. I keep the door open when bathroom is not in use so that fresh air can be introduced throughout the attic. When I run the vent hood or dryer on the main floor it will create negative pressure bringing in air from the basement via stack effect. Will the ERV balance out the pressure by bringing in more fresh air? I just close cell sprayed my rafters and dense packed my main floor with cellulose so the house is a lot tighter.

Well .. not sure. I'm no expert. Maybe some of the experts on here know. Wish I could help.

Michael, hard to say exactly what will happen in your house without doing some simple testing, but I would expect some of the makeup air for the range hood and dryer to come in through the attic ERV, and I would expect some to come through other openings in the shell. Do you have any combustion appliances in the house, fireplaces, woodstoves, etc? If your house is "a lot tighter" then I think you probably need to evaluate the ventilation needs and combustion safety. It doesn't seem likely to me that a spot ERV in the attic can serve the whole house.

Thanks for you feedback David, I plan on adding another spot ERV in the basement and also insulate to air seal the whole house. I was just curious if the makeup air would pull through the fresh air intakes of the spot ERV at a higher clip then the exhaust when my vent hood and/or dryer are running. Air sealing the whole house would limit the amount of air coming in from the shell.

I have a fireplace insert. The other concern is the oil furnace in the basement. Last thing I want is the bad gases to be sucked up into the living space so eventually plan on separating out the mechanical room from the living space in the basement and giving it it's own access to air with a dedicated vent.

Am trying to balance energy efficiency with an equal or greater focus on a healthy home for the family.

Thanks.