Advice for HRV/ERV on a budget
I am in climate zone 4C and building a fairly efficient home on a really tight budget. I used flashing tape and sealed all seams in my sheathing and will hopefully have a really tight home. The house is two stories, each story just over a 1000 sq ft (2100 sq ft total), and the home is designed so the majority of the living space is upstairs. I was planning on installing a single Panasonic Spot HRV in a central place upstairs, but a mechanical contractor (who was trying to sell me something) has told me that this will not be sufficient. and has recommended a Lifebreath RNC 95. This type of system seems more expensive and more complicated to install (I’m hopefully going to be doing the install).
If I install the spot ERV in the center of the second floor, it would be located in-between my bedrooms and my heat source (mini split head) on that floor. Will this block my heat from the bedrooms?
Will the the Panasonic be sufficient? Would it be better to install two of them and put the second on the first floor?
Does anyone have recommendations for a efficient, reasonably priced, and relatively easy to install ERv/HRV?
Any advise would greatly be appreciated.
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Replies
Kail,
ASHRAE’s residential ventilation standard (Standard 62.2) sets the minimum ventilation rate at 7.5 cfm per occupant plus 3 cfm for every 100 square feet of occupiable floor area. If you want to comply with this standard, you would need 71 cfm for one occupant, 78 cfm for two occupants, 86 cfm for three occupants, or 93 cfm for four occupants.
The Panasonic WhisperComfort ERV has a maximum airflow rate of 40 cfm, which may not be enough, unless you are one of the many people who think that the ASHRAE 62.2 standard requires too high of a ventilation rate. (The Panasonic ERV is a terrible choice for cold climates, because it can't be used when it gets cold outdoors. In Climate Zone 4, that may not be a problem, however.)
Whether a ventilation system is "good enough" depends on your expectations and needs, as well as your lifestyle. It's hard to generalize. If you are worried that the Panasonic unit provides insufficient airflow, it can always be supplemented by a bath exhaust fan on a timer. For more information, see Designing a Good Ventilation System.
Thanks Martin- Do you or anyone else have any recommendations for a unit that is around 80-90 cfm?
Do most units have trunk lines that branches off to rooms for both the return and exhuast? Do only the high-end (super expensive) units come with small plastic tubes for individual home runs?
Thanks for the help.
Kail,
Almost all HRVs and ERVs (except the Panasonic WhisperComfort ERV and the various Lunos models) have 4 ducts -- two ducts connecting the unit to the outdoors, one duct connecting the unit to fresh air registers, and one duct connecting the unit to exhaust air grilles. You can make the ductwork as simple or as complicated as you want by installing tees, wyes, or takeoffs -- one supply register or 5, and one exhaust grille or 4, as you prefer.
A Renewaire ERV costs about $1,000. Renewaire makes three models (EV90, GR90, EV90P) rated at 40 cfm to 110 cfm.
Those small plastic tubes that you describe are part of the Zehnder system. And you are correct to characterize Zehnder equipment as super-expensive.
I installed two of the Panasonic WhisperComfort ERVs. My house needed 80 cfm for adequate ventilation. Unfortunately, testing showed the ERVs were only producing half their rated cfm. I ended up removing one of the Panasonic units (long story there) and installing an UltraAire ventilator/dehumidifier.
The Panasonics were a huge disappointment. As the hold saying goes, you sometimes get what you pay for.
Steve, what was the ducting configuration like? Long or convoluted runs will eat into the CFM. Seems like upsizing to 6" ducts would be relatively cheap and simple insurance.
Steve, do you know what the panasonics were actually producing as far a CFM? I know that there is a internal dip switch that changes them from 20/40 CFM to 10/20 CFM. Is it possible that the dip switches were in the wrong setting? I have friends that put them in and seem happy, but I am reluctant and trying to educate myself.