Fresh Ventilation

Brad White_185

A minor point of semantics, Mike- I had a professor years ago who weened me from the habit of calling "outside air" "fresh air", asking, "what is so fresh about it? It is full of pollutants and if it were in a condition to make you more comfortable, why are you inside discussing this?" :)

Now, to your point (if and as I understand it):

Your supply ducting from your HRV is under positive pressure (and that air is presumably outside air to begin with, pre-conditioned by heat transferred from outgoing exhaust.) So I am not sure what benefit there would be to bringing outside air into that duct that is not already present.

Besides, you would need a fan to overcome the HRV outlet pressure which would negate energy from the HRV itself, making it work harder and delivering less air.

Now, if you mean to take the HRV outlet (pre-conditioned OA) to another air handler, that would be ducted into the return duct of whatever might serve your home. Absent that, duct it to a common area to be drawn to fixed points of exhaust.

Did I come close to understanding let alone answering your question? Let me know.

Brad

Mike T., Swampeast MO

Can fresh air be introduced into the fresh air supply ducting from an HRV?

In a shell as tight as, oh let's say your average refrigerator, would this result in net positive ventilation?

Weezbo

Mike, do you mean to by pass the hrv?

they make an ERV for ventilation . maybe it would be easier to install and deal with ...

it is different from a secondary heating /cooling .. in a scorched air system .. it would take "advantage" of outside temp at various parts of the day and evening... ERV's and HRV's don't really do that.

Mike T., Swampeast MO

Brad:

You got it right. The blowers would be fighting one another. So much for that easy idea.

The problem is slight overheat due to solar gain and basic occupancy in moderate weather. "Moderate" for this climate and this house being about 25F. Windows will be used in weather normally considered "moderate".

Natural infiltration, while unmeasured, is extraordinarily low. I'd consider attaching a blower door with lag screws. I must assume below 0.09 ach of natural infiltration with about 32,000 cuft envelope volume.

Is there a way to variably bypass the heat exchange portion of an existing HRV?

Mike T., Swampeast MO

A potential issue is that an atmospheric power vented gas water heater is in use. While reasonable measures have been taken to provide makeup air, the shell is so extremely air-tight and well insulated that it's difficult to determine a reasonable scale for comparison.

jp_2

run it more

couldn't you get the same effect if you run it more, they are only so "Efficient" at transferring heat. so the more you run it, the lower the indoor temp would go.

you could introduce fresh cold air just after the heat transfer box, lowering the new freah air temp. this would not reduce total air flow, just reduce new air temp coming in the rooms. could control an air damper via tstat somewhere in the house.

this is kind of like closely spaced Tee's, what goes in comes out!

Added: guys, no "extra fan" needed.

if what brad say is correct, supply side pressurized, then duct the cold air into the warm "return" air that is going into the heat excharge, this would pre-cool house air, but lowering the houses air exchange rate.

jp_2

no longer air tight

the HRV system should equal out pressures.

even with the HRV unit off, the power vent water heater should draw outside air through the HRV unit. unless the HRV has an air tight damper?

Weezbo

mike, i do not happen to agree with the use of an HRV to deliver

combustion make up air.

that does not "Work" for me.

if you have a power vented Jenn air (Stove/oven) or Power vented heating system, then that ought to be from a dedicated supply source...

Mike T., Swampeast MO

Agree. That's why there's makeup air in the mech room.

Mike T., Swampeast MO

Thanks for reminding me that it's only a paper mach

Rich L.

MU air

How's the make up air coming in Mike, and is it controlled to match combustion?

I've followed the other thread and think it's fascinating.

Rich L.

MU air

How's the make up air coming in Mike, and is it controlled to match combustion?

I've followed the other thread about this house and found it fascinating. Nice job Mike.