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Thread: HRV or ERV?

  1. #14
    Join Date
    Dec 2000
    Location
    Michigan
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    724

    Wink Info on poster

    Nick, if you want to know more about a poster you can click on the icons at the bottom. One will show bio info others may have a web site with links etc.

    Continue your research, click at the bottom of ALL posters and good luck.

    I am off shipping units now that utility bills are UP, but will reply with data to your questions so you can compare the advice.

    One final point, the best home is one that has NO Delta P between inside or outside summer and winter! This home will reduce the possibility for Radon and Mold! I think that perhaps some of the posters must have "positive pressure somewhere"!!!!
    The quality of my performance, sometimes depends on the quality of my audience.
    Imitation (Plagiarism) is the best compliment one can get -- "Open A Window"

    To improve Indoor Air Quality: Control Indoor Air QUANTITY = "I.A.Q.Q."

  2. #15
    Join Date
    Apr 2002
    Posts
    11,808

    Re: Info on poster

    Originally posted by Xavier


    One final point, the best home is one that has NO Delta P between inside or outside summer and winter! This home will reduce the possibility for Radon and Mold! I think that perhaps some of the posters must have "positive pressure somewhere"!!!!
    X , from a functional viewpoint, I see no difference with your product or going to Home Depot and buying two air intake hoods, ducting one to the return air of the furnace and use the second one as a combustion air intake. Ignoring function then, I see three differences. Your product costs more, you only have to cut one hole in the wall, and maybe you have deisgner colours that may look better. Flapper my a$$.

    When the furnace fan runs you are pressurizing the space and when it is off, you are providing a parallel path to the building envelope as the space goes naturally negative. You average the positive and negative cycles and call this neutral?

    Measure some airflows through your device and post them to prove me wrong. No natural stack effect just yet, but I will remind you again in January. I have asked you this on several occassions over the past couple years and it would be so easy to post some numbers if you had them to prove me wrong and make me eat crow, but you never do, because you have no clue as to what your device does.

    If you control pressure, you control the flow of air through the building envelope and you can prevent air from contacting surface cool enough to cause condensation.

    This is a very common practise in commerical, educational and institutional buildings.

    The link below is a long one and is geared towards a hot humid climate, however it would apply to any summer time home where you run air conditioning. You have seen this link before, scroll down and read about pressurization.

    http://www.fsec.ucf.edu/bldg/science/mold/index.htm

    You should market your product in Florida. On a small house add the instruction "Connect one duct (or hose as you call them) to the return air ductwork,and plug the second opening." For larger house "Connect both hoses to the return". One size fits all. What a marketing strategy. Hell if you make them real pretty and drop the price I will distribute them in the Caribbean for you.

    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  3. #16
    Join Date
    Apr 2002
    Posts
    11,808
    Originally posted by nicholasa
    Carnak,

    http://www.aprilair.com/product.asp?...D14F348EB3FF1e

    I am thinking of going with a HRV instead, for winter time use only. It will keep the winter time indoor RH lower than an ERV will ? I am told that You can rot a super tight house out in the winter (from the inside out), if You do not ventalate and keep the RH down.

    Xavier,
    Do You have a link to the damper control with differental pressure sensors ?

    Thanks,
    Nick
    I looked at the unit and it is similar to an HRV, but the core also allows moisture transfer. I am trying to figure out if it has a means of temporarily bypassing the humidity exchange.

    An HRV will work hard the first winter after the house is built, drying out all the moisture from new construction. During the second winter, you will find that it will over dry your home and a means of avoiding this is to run the unit intermittently, via the standard controls, so that it kicks on as RH rises. This will usually give decent IAQ.

    The ERV should allow you the luxury of the constant fresh air, without overdrying the home, and give you the maximum IAQ possible.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  4. #17
    Join Date
    May 2004
    Posts
    58
    Heres another thought on the ERV/HRV debate.
    On the manufactures climate maps (that show where ERV or HRV's should be used, by climate). HRV's are for way up north, but ERV's are recomended for most of the US.

    Now I understand that ERV's would be needed for area's that have a long cooling season, so as not to introduce to much humidity. But if HRV's are drying out houses to much up north, why are they not recomending ERV's up there ?? they would retain 50% of the indoor RH. or is this to wet in a tight house ???

    I am getting a new Bryant unit that works with the infinity controller. but I cant make a decision HRV or ERV.

    Nick

  5. #18
    Join Date
    Apr 2002
    Posts
    11,808
    The HRVs and ERVs go into defrost mode. The HRV will frost up only on the exhaust side, the ERV because it transfers moisture would tend to freeze up on both sides.

    The HRV has a condensate drain while the ERV does not. The drain is for when the core freezes up. Wheel type of ERVs are used in Canada but they are no where near as common as the HRV up there.

    Where you are the ERV will be fine, to give you peace of mind, you will want one that can temporarily bypass air when humidity gets too high in winter.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  6. #19
    Join Date
    Oct 2003
    Posts
    45
    I'm a bit late to this thread but I'll provide a bit more info in the event that it is still timely. First, just about all of the HRV's and ERV's distributed in North America are built either by Venmar or Lifebreath. Companies like Bryant, Lennox, Broan, Carrier, etc. just rebadge these manufacturers' boxes. Second, most of the info here is correct, but I feel some explanation is in order.

    I think there is a general assumption that ERV's exchange latent energy on a 1-1 ratio. TB mentioned a 50% exchange ratio. Well with certain ERV's, neither is true. I've seen figures as low as 26%. Most of the variation can be accounted for in the design (wheel vs. counterflow/crossflow core). The very best way to screen products for a specific application is to evaluate the figures posted in the product directory found on hvi.org's site. You'll also see the redundancies with respect to products from various manufacturers vis-a-vis Venmar & Lifebreath. It's quite amusing actually because the spec's are absolutely identical. Not a single variation!

    With respect to nicholasa's application, I agree with Carnak that an ERV would be beneficial, however, I wouldn't recommend a common ERV like the AVS Duo from Venmar because it transfers too much latent energy (if indoor RH during heating season is primary concern). Instead, search the numbers for an ERV that is still fairly efficient with respect to sensible load (apparent sensible effectiveness) but decreases latent recovery % as the temp falls or cfm increases (preferably both). Guess what? There exists such a unit made by Venmar for VanEE called the 2001ERV. Unfortunately, that product is only available in Canada. BUT, look closely through the sheets in that product directory and BINGO you'll find the exact same spec's from a Broan/Nutone ERV200HC. There you go, the exact same product available domestically. I would assume that the Carrier ERV is, in fact, this very same unit, all originating from Venmar. Check the spec's @ hvi.org to confirm. For the best info about this piece, go to VanEE's web site and look at the Gold Series ERV's. This site has the most detailed info available.

    But the real incredible feature with this piece is that it is fully convertible. Simply swap cores and remove a jumper on the circuit board, and you've got the 2001 HRV. Brilliant design. You just can't go wrong with this unit in the U.S. heating climates where a SEVERE moisture problem in the heating months is not apparent. For humid, cooling climates, the latent recovery efficiency probably won't cut it, so one would need to look elsewhere.

    [Edited by goldenear on 10-07-2004 at 07:18 PM]

  7. #20
    Join Date
    Jan 2007
    Posts
    2

    It's been over 2 years - any update?

    Goldenear,

    Not sure if you'll get this, but I would really like to hear how you feel about ERV vs. HRV today. Unfortunately, not much has changed in the ERV/HRV market, but I've seen a few exceptions of advancements.

    I will decide between an ERV/HRV in a newbuild located in Denver, CO. My greatest concern is interior condensation in the winter. I won't run AC in the summer, so there is little benefit of an ERV during "cooling" months.

    Very curious to hear what you like these days.

    Thanks,
    Ben

  8. #21
    Join Date
    Oct 2003
    Posts
    45
    Hey Ben,

    I agree that not much has changed in ERV/HRV over the past few years, and I consider that to be a GOOD thing (except more companies are trying to manufacture their own models - pro's and con's to that one). I'm still using the relabeled VanEE model from Broan and it's excellent. I've considered reinstalling from a volume to a more dedicated install because interlocking it with the furnace fan is definitely more costly over the long run. Plus, people wouldn't complain about the drafts in the winter; but have not done so yet. The one thing I like about my install currently is that fresh air is hitting the furnace media filter before getting into the air envelope of the home. The filter that comes with the unit I have is basically a bug screen, so it does nothing to help my family with their allergy issues. The HEPA units solve this problem.

    I don't know what your typical dew points are in the winter months in Denver, but I'd guess that they're relatively low. During the past week here in WI, we have experienced some of the harshest dry air that I can ever remember (I'm 35). This week, the dew point has averaged something around -15F! Holy #*(%. Talk about miserable. I cannot imagine the pain and suffering people who live in loose homes are feeling right now. Heated to 68-70F, some loose homes with no humidification could be sitting in single digits indoor RH! I think my nose would fall off.

    And if you ran an HRV under these conditions, you'd create a comparable indoor RH because you're not exchanging any moisture content upon air exchange. Even with an ERV, I've had to basically turn it off because the conditions are so extreme and I don't have a humidifier installed - will probably pick one up so the next time this happens, I'll be ready. Even with a very tight home and no exhaust fan use of any kind except intermittent use of a clothes drier, we're still down to ~35% indoor RH!

    So I'd say better go with the ERV. You'll lose some of the recovery efficiency in winter compared to an HRV, but you'll be more comfortable, esp if running continuously. Of course, you could always go the HRV route combined with a humidifier if heating expense was super high. If you picked up the same model I have, you could actually buy the HRV core and swap cores whenever you wanted to convert the machine. But if heat recovery is THAT much of an issue ($$$), then it'd be better to get a unit with a very large core to increase efficiency (probably wouldn't be convertible, so you'd have to install the humidifier as well).

    Regarding summer use, if you ventilate with open windows, then yeah, not much need to go mechanical. But as soon as you close up that house, then there's a huge benefit in terms of IAQ to run the system.

    Hope this helps...

  9. #22
    Join Date
    Apr 2003
    Posts
    248
    I live near Toronto, Canada and have the Van-EE Gold 1001 ERV. It actually was an HRV model when I bought it, but I since bought the ERV core and converted it over.

    I found the HRV brought in too much humidity in the summer. So much so, that I just turned it off for the summer. By the next summer, I had installed the ERV core. Big difference. I can now run the ERV year round and humidity levels are in check. I still have to use dehumidifiers in the basement of course, but they cycle on and off instead of running constantly when I had the HRV core.

    So in the end I found the ERV to be more suitable.

  10. #23
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    6,643
    Quote Originally Posted by goldenear View Post
    Hey Ben,

    And if you ran an HRV under these conditions, you'd create a comparable indoor RH because you're not exchanging any moisture content upon air exchange. Even with an ERV, I've had to basically turn it off because the conditions are so extreme and I don't have a humidifier installed - will probably pick one up so the next time this happens, I'll be ready. Even with a very tight home and no exhaust fan use of any kind except intermittent use of a clothes drier, we're still down to ~35% indoor RH!

    Hope this helps...
    Good post! One point you are illistrating is the lack of the need for mechanical venilation during cold dry weather. If no mechanical ventilation is required during the only time heat energy is saved, what is the benefit? Clothes driers, kitchen hoods, water heaters, and bath fans need make-up air to function. Balance flow ventilation ERV/HRVs takeout as much air as they bring in, therefore no help. Homes need more fresh air during the neutral weather. They need make-up air for other exhaust devices to function. Homes need supplemental dehumidification during times of low/no cooling load conditions to avoid biological growth. To me, most homes are better served by a ventilating dehumidifier. HRV/ERVs are a must for extremely tight homes in cold climates with high cost electric heat, and high ventilation needs. We sell both. TB

  11. #24
    Join Date
    Apr 2002
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    The ventilation is needed in the coldest weather in the tight homes, otherwise you end up window condensation.

    If the home is dry in the coldest weather and actually needs a humidifier, it does not need ventilation, the infiltration is plenty

    Supplemental dehumidification in the summer can be a neccessity in some homes or band aid repairs in others.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  12. #25
    Join Date
    Oct 2003
    Posts
    45
    Well dry is a relative term, right? For me personally, the past couple of weeks have brought the coldest, driest air that I can ever remember. This has been a brutal beginning to February, so much so that I'm thinking of moving, lol. In order for my house to avoid condensation on the windows right now, I'd have to maintain an indoor RH of probably <20%. That's great for the house but horrible for us humans.

    Ask any otolaryngologist about indoor RH during the heating months and they're going to tell you to definitely keep it above 30%, preferably no lower than 40%. So there's a conflict between the building scientists and the medical professionals. Some people can get away with temporary bouts of extremely low indoor RH. Others like me who have really bad vasomotor rhinitis, which seems to triggered by large swings in RH, temp, and barometric pressure, or those who have a house full of occupants with viral and bacterial upper respiratory infections, have little choice but to say to heck with the wooden casement windows - let 'em rot in winter, I'll fix 'em in the spring.

    Windows really are the weak link in the building envelope, assuming everything else is properly sealed and insulated. Unfortunately, if you don't build, then you're stuck with whatever came with the house (usually inadequate even in new construction) and that will ultimately determine your indoor RH if you're absolutely committed to maintaining a condensate free interior.

  13. #26
    Join Date
    Oct 2003
    Posts
    45
    Quote Originally Posted by teddy bear View Post
    Good post! One point you are illistrating is the lack of the need for mechanical venilation during cold dry weather. If no mechanical ventilation is required during the only time heat energy is saved, what is the benefit?
    I agree, but here in southeast WI, the past stretch of 10-20 days has been an extreme and definitely not the norm for the 6-7 months of the heating season (Oct-Mar/Apr). So you've got, at the most, one month out of let's say avg. of 6.5 months that there's no ROI on an HRV (ERV is beneficial the remainder of the yr in this climate, esp with a family affected by seasonal allergies, so opening windows is not advised).

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