HRV intake and exhaust spacing
tomk358
| Posted in Mechanicals on
I’m installing a Fantech VHR704 into my small, tight superinsulated home. The install manual states that intake and exhaust air ducts to the outside need to be spaced 6′ apart. I’m wondering if it would be possible to install them in a vertical spacing- so the warm exhaust air would exit 6′ above the intake vent. Seems to me that there would be enough air around that you wouldn’t short circuit the system, but I’m wondering if anyone else has any thoughts on this. The main reason I want to do this is because I have very little room to run the 4″ duct in the kitchen soffit.
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Replies
Since you say warm air exhaust, I assume you are in a cold climate, but even so, you probably have some warm months, when the exhaust might be cooler than the outside air, at which point your plan isn't as foolproof.
You can run either intake or exhaust ducts along the way outside the envelope, and in fact that is preferred as they then do not need insulation. Aesthetics might be a concern.
I'm in Portland, Oregon- so in general when it's warm out, the windows will be open. That said, I never realized you could run the ducts outside. Makes sense. So, do they make special ducts that are for exterior use? Or could I use normal galvanized?
I uses thin wall PVC for the exterior ducting outside as you can paint it, it doesn't rust, and it is is easy to work with.
Tom,
1. In general, it never hurts to contact the manufacturer with questions concerning the installation of their products. Fantech's numbers are 800-747-1762 and 941-351-2947.
2. PVC will work, especially for exhaust ducts, but some green builders avoid PVC for fresh air ducts because of off-gassing worries.
Galvanized metal works outside, and last even longer when painted. Galvanizing for fence posts and the like is generally heavier than for interior ducts, so I wouldn't count on it lasting 50 years, but it would be easy to replace when it rusts through. The exhaust duct could have condensation inside, so a galvanized duct on the intake would likely last longer than the exhaust. You could duct the intake with galvanized, and exhaust with PVC, or just duct one of the two. I suppose HDPE drain pipe would be another option to avoid PVC and avoid rust.
I had a nice call with Fantech USA support, he told me 6' vertical spacing instead of horizontal on the exterior supply and exhaust is just fine with them.