So I know its cold out 3F or -16C, but this is the first time I noticed our fresh air intake had condensation on the exterior of the plastic. Our last house had a regular flex duct rated at R4. For this house I ordered some fancy R8 flex duct, looks the same but... Anyway it runs about 15 feet from the exterior all to the HRV and about 10 feet of that is above a plastered ceiling.

Every house I have been in up here has condensation on either the fresh air intake for the furnace or HRV, isn't there a better way?

I am concerned because if water is collecting inside the flex duct it could potentially compress the insulation even farther reducing its R value and perpetuating the situation. I am sure I sealed the plastic at the exterior wall and HRV end really well. When we built I toyed with the idea of trying to stuff the flex 6” inside a flex 10 inch, but I couldn’t because of space limitations.

thoughts?

I had the same problem last winter and am at same temp+- and nothing yet.
What I done was put another layer of foiled insulation around the intake and seems to be working.
You might have to limit your air change time to help with the condensation if no room for more insulation.

All the fastening details I have seen for flex duct make a point of fastening both the inner and outer liners. As long as the moisture cannot reach the insulation there should not be any issues.

hummm, I would think leaving the HRV on all the time would reduce the issue? Maybe not?

I agree though, as long as the interior tube and the exterior is intact the insulation should be dry, so maybe it's OK.

It was wet again this am, but then again it was -7F or -21C. The weird part is I didn't see this the last two years.

Air coming in being -20c and conditioned house air being 20c is quit the differential so condensation will be present if both air temps are not completely isolated from each other. The only other option I can think of would be to heat the air coming in to lower the temperature difference. Not having any room for more insulation this might be your only alternative.
Keep us updated on results!

Funny you should mention warming the incoming air. My father suggested putting a 300w heater on the outside of the house against the intake. He said I wouldn't be loosing the heat since it was going in the house anyway and raising the air temp 10-20F would cause the air to become very dry and dry out the intake. He thinks it might be snow that got sucked in the intake during the last storm. I do have a temperature sensor right at the HRV and it is only about 2-3F warmer than the outside temp, so it must be still insulated pretty well.

Snow being sucked in is improbable but not impossible.
Another option instead of the outside 300w heater would be a "in duct heater" which would be in direct connection with the hrv so that when it fires up the heater will come on and warm the air as it comes in.

Remember that the condensate is coming from the moisture in the inside air. Is the house at a higher rel. humidity then previous years? I agree that running the unit more not less would be the answer. An external heater seems to defeat the purpose of HR units. There has been some discussions on HRV in other forums with different opinions on their usefulness in really cold conditions. One thing that might be happening depending on the make of unit, is that it is recycling for approx. 20 minutes of every hour to prevent freeze up. Therefore is it is size just right for your house and not exhausting for 1/3 of the time, it is not moving out enough air therefore your moisture levels are to high. Please let us know what your relative humidity is when it is condensating

The house is at 38% at 70F, the HRV exhaust is from the pool room however which is usually 60% at 85F. The HRV dumps back in to the house, which positive pressures the house and sucks out of the pool room so the pool stays negative to the house so the pool doesn't "leak" back in to the house. I do have two 6" vents from the house to the pool room for letting air back in there.

The HRV works great though, the other morning it was intaking 5F and dumping 65F to the house. When the pool is in use it will be making about a gallon of water in 5 minutes.

I hadn't thought about the defrost cycle, I believe it just shuts off the intake line and only exhausts, I know there are no mechanical dampers, just each fan power control. It has been really windy lately as well. No condensation this am and it was 2F