ERV Inspection, Fixes, and Home Ventilation Advice from a High Mountain Crawlspace 

Low hanging fruit: Do a simple rework of the duct of the HRV a) Rotate the HRV unit on its axis to minimize the angle bend totals of each run (ex 90 x 12 = 1080 deg). b) Assuming that the unit has a flow capacity of over 150cfm, transition immediately to 8” on the runs that are longer than 40 ft, otherwise stay with 6”. c) It is ok to use one 90 at the unit if needed, otherwise it is better to simply use properly tensioned oversized (8”) flex duct bends which eliminate vibration transfer to the structure on all four runs and virtually eliminate condensation inside the ducts running in the unconditioned space in the winter months. d) I would totally install a low cost Corsi-Rosenthal filter or two with large MERV13 panels running on slow 24-7 or triggered when the ventilator runs if there is no forced air and media filter running 20min/hr throughout the house (1000+ cfm). The need for filtered air at some velocity (>200fpm) is why I am not a big fan of stand-alone installations of ventilators.

Nice real life example of what a knowledge and experience means. We built our house in Pa in 2001 and have hydronic heat which I love but NO central A/C or duct work or air movement at all. (Except one window A/C unit) We also have a wood burner. The only reason we have had little issues is we have ceiling fans and open windows regularly when we can, and have a dehumidifier and I’m sensitive to humidity or lack of. We do suffer with a dry house in the winter. I would never recommend this set up to anyone that doesn’t know to monitor their air “quality” but it works for us and is a low tech solution. That being said on our second home we are working on we are also going with hydronic but thanks to your channel we have a lot more tech going in to monitor air “quality”

Thanks for sharing.

A stand-alone HEPA filter would help a lot here.

Hey man! Love your channel and am using it to become informed in designing the hvac for my new house. Is there a good indoor air quality measuring station that you recommend?

I assume you also removed/propped open that intake vent flap before you got your last co2 reading

How are you coming along on those fire resistant vent covers I asked you about a month ago? Matt Risinger just did a podcast where he mentioned using Seiho vents and American Aldes vents, both of which are made from metal. As we get into fire season in North America I hope you'll have a video out soon on hoe to protect building penetrations from embers and flame contact.

So what would be the best ventilator type for a cool moist climate, such as the Pacific NW? Most of the time we would need a dehumidifier regardless of the time of year.

I am building a hose in the mountains of Vermont. Going for Radiant in floor heat. Question is should I do full duct work for ERV? Or AC? Or should I go with ductless minisplits in the 4 bedrooms? What is the best option when heating with radiant?

I'm building a building for my wife's dog sitting business. Being in Central/South Texas we have humidity most of the year. Add dogs to the mix, air quality gets fun. Add to that, a very, very sealed building (closed cell foam). I'm going with a mini split (very poor filtration and de-hum), but adding an ERV, De-Hum and a AirIQ stand alone air purifier. I might not need the de-hum, but I would rather have it and not need it, than .. well, you know. I might be able to add it later... but it sure is easier before drywall goes up.

Shouldn't the pipes be insulated, at least on the house exhaust and house return? Given that this is outside of the envelope? Or is the crawlspace sufficiently warm compared to the outside that insulation isn't a must? Given all those 90s, it might make sense to address that problem first even if it should be insulated. And sealing would be between removing some 90s and insulating. If the inside of the house is humid, condensation could be happening in the duct itself without insulation. But, I have never lived in a dry environment.

Did you find out how his radon removal system is blocked?

Man that was a lot of bugs flying around for that to be a "sealed" crawlspace.

Why are they putting HRV cabinets in a literal crawl space ? So much wrong with that install.

I love it spend a ton of extra money and seal up your house so you can buy more mechanicals you havv be e to eventually replace, troubleshoot, and have the annoying sounds and air movement yeeeseeaAAAA sign me up