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Thread: Confused by mixed messages for HRV/ERV System

  1. #1
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    Confused Confused by mixed messages for HRV/ERV System

    Hi all! I've been a lurker on these forums for quite some time, so let me say thanks for all the great info everybody has provided as it has helped me along the way!

    I'm a sufferer of allergies, as I now work from home and am always congested, groggy, headache, etc. My first thought was of course a better air filter system. I currently run a Winix air purifier in the bedrooms (my wife and I, and one in the babies room), as well as in my workspace (finished basement). But after reading posts here, it sounds like getting fresh, filtered air is a much better way to rid potential allergens.

    When we had our baby a year or so ago, we stayed in the hospital a few nights, and I had ZERO allergy response. I understand that air is probably sterilized, but I was in heaven for a few days. It was amazing. Despite sleeping very little, I woke up tired but didn't have the typical headache pressure all day.

    I live in the Midwest, in Woodstock, IL in fact. In a 2006 builder-grade home, approx. 2350 sq/ft total with finished basement incl.. We have some hot summer days here, but nothing crazy or for too long at least. More mild/unpredictable weather, with some VERY cold winters as some may be familiar with. Which the winters can be very dry I believe. We have a whole house humidifier which I upgraded to an auto humidistat, as well as a dehumidifier in the basement area. Just upgraded the old thermostat to a Honeywell T10, presumably ready for ventilation programming. Sensors were a fun idea which I added to some rooms.

    So I called 3 local HVAC companies, which all came out to provide quotes. Only one of which I have rec'd a quote so far, still waiting on the other two since early last week. Maybe it's the busy season so I'm being patient.

    My confusion comes in as two of the three companies (mainly one) that came out repeatedly asked me why I wanted air ventilation. What are my reasons? My response was; Allergies, excessive moisture on the windows in the cold winters (bonus as the wife towels them down daily during this time, we need new windows though). Oddly though, they tell me how expensive it is, that I can do a better air filter system (currently have a 1" MERV16, stresses the HVAC I'm told), fresh air port (which will pressurize the house), just run the bathroom fans, etc. Almost as they either don't want to do it, or try to talk me out of it for some reason. Maybe because the trade-off isn't like adding A/C to the house. I won't 'feel' the difference in temp, but am hoping to in allergy response.

    The basement is finished, but there is room to run the outside airflow, some drywall opening up would be required, and I'm ok with that. Run length is above a bedroom, utility room is finished, although not a ton of room for a system, but doable.

    The first company which I have a quote from so far, recommended ERV, as it transfers heat AND moisture, vs. HRV which is only heat. Is that right? This confused me based on research of HRV and ERV.
    Their quote was $XX total for a Lennox ERV5-175-TPD, Lennox HEPA-40 bypass filter box, and Lennox HCC20-28 (which I believe is a filter upgrade from my 1" to a 5"). As well as duct cleaning (returns are nasty) for $XXX. Seemed good for all included I guess? The guy who came out said he has an ERV and runs it 24/7. Assuming he lives locally of course.

    The second company who I don't have a quote from yet didn't seem to know much about it, but is going to quote an HRV.

    The third company was the pushy one (meaning pushing me away from going fresh air ventilation), also is going to quote and recommended HRV.

    I feel that with these systems not being that popular up here, maybe these companies are just not as familiar, or is it me who is the unfamiliar one and simply confused.

    What do you all recommend? HRV or ERV? Anybody experience adding this system and helping allergies?
    Budget is about XXX, so the first company seemed right under budget.

    Appreciate the help in advance! Happy new years!


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  2. #2
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    Slow your roll!
    Hold off on the ventilation until you find out what is really needed. There’s no point in spending the money on abentilator if it’s not going to solve your problem.
    Start with a blower door test to find out how leaky your house is. During the test they should use a thermal imaging camera and do zonal testing to identify the biggest leaks so they can be remedied. infiltration can carry in lots of minute particles from attics, walls, and crawl spaces. Once that is done, focus on filtration.
    Before going wild with filtration, have your HVAC system static pressure measured. High MERV air filters can add a lot of resistance to air flow and most duct systems are too small to begin with. Duct upgrades may be necessary. Then you can look at improved filtration. I like the Aprilaire filters for low resistance and high filtration.
    *********
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    Find contractors with specialized training in combustion analysis, residential system performance, air flow, and duct optimization https://www.myhomecomfort.org/


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  3. #3
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    Thread Starter
    Quote Originally Posted by kdean1 View Post
    Slow your roll!
    Hold off on the ventilation until you find out what is really needed. There’s no point in spending the money on abentilator if it’s not going to solve your problem.
    Start with a blower door test to find out how leaky your house is. During the test they should use a thermal imaging camera and do zonal testing to identify the biggest leaks so they can be remedied. infiltration can carry in lots of minute particles from attics, walls, and crawl spaces. Once that is done, focus on filtration.
    Before going wild with filtration, have your HVAC system static pressure measured. High MERV air filters can add a lot of resistance to air flow and most duct systems are too small to begin with. Duct upgrades may be necessary. Then you can look at improved filtration. I like the Aprilaire filters for low resistance and high filtration.
    Thanks! Will look into that first. We are thinking to start with a furnace filter upgrade as well to start things off and see if that helps.

  4. #4
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    Welcome Woodstock. My home for many years (S.Jefferson) and maybe a perfect town to live in.
    First I have little experience with HRV's so I'll leave that to the more gifted. I do know with most things "Dilution is the solution" That's the mantra with most problems that deal with pollution. Your home might be polluted causing the allergies. In my case it's the dogs.
    The problem with trying to filter the allergens is the air has to pass through the filter. Most air in a house never makes it to the filter. Almost all return air occurs within a few feet from the filter. This is a hard sell even to people in hvac because it seems all the air should get there. Studies have shown differently.
    Good filtration is still a good idea even if that alone will probably not fully solve your problem. I'm not that sure how efective they are with something that tiny and you'd probably need to run the fan continuously.

    Knowing what your allergic to is a start. Only testing can tell just what the problem is. Before HRV's were around I ran a small duct outside and adjusted with a damper. Today the ERV's & Hrv's make sense to me.
    The why about the condensation on the windows would need to be answered. Are the windows double glazed? What is the source of the moisture? I wonder because so many homes there need humidifiers. I know I did and my home was built in 1918. It's not that winters are dry, it's that when the outside air is heated it becomes dry because warm air can hold more water vapor. I suspect poor windows or a source of humidity that's unusual. If windows are suspected, a cheap temporary fix is the films sold for windows.
    Another question is can your furnace have enough fan power to satisfy the load using a high eff filter. I wouldn't expect much from using a filter the furnace wasn't designed for. I like fresh air.
    Give me a relay with big enough contacts, and I'll run the world!

    You can be anything you want......As long as you don't suck at it.

    If a person wants to create a machine that will be more likely to fail...Make it complicated.

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  5. #5
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    Quote Originally Posted by hvacker View Post
    Welcome Woodstock. My home for many years (S.Jefferson) and maybe a perfect town to live in.
    First I have little experience with HRV's so I'll leave that to the more gifted. I do know with most things "Dilution is the solution" That's the mantra with most problems that deal with pollution. Your home might be polluted causing the allergies. In my case it's the dogs.
    The problem with trying to filter the allergens is the air has to pass through the filter. Most air in a house never makes it to the filter. Almost all return air occurs within a few feet from the filter. This is a hard sell even to people in hvac because it seems all the air should get there. Studies have shown differently.
    Good filtration is still a good idea even if that alone will probably not fully solve your problem. I'm not that sure how efective they are with something that tiny and you'd probably need to run the fan continuously.

    Knowing what your allergic to is a start. Only testing can tell just what the problem is. Before HRV's were around I ran a small duct outside and adjusted with a damper. Today the ERV's & Hrv's make sense to me.
    The why about the condensation on the windows would need to be answered. Are the windows double glazed? What is the source of the moisture? I wonder because so many homes there need humidifiers. I know I did and my home was built in 1918. It's not that winters are dry, it's that when the outside air is heated it becomes dry because warm air can hold more water vapor. I suspect poor windows or a source of humidity that's unusual. If windows are suspected, a cheap temporary fix is the films sold for windows.
    Another question is can your furnace have enough fan power to satisfy the load using a high eff filter. I wouldn't expect much from using a filter the furnace wasn't designed for. I like fresh air.
    Thanks S.Jefferson! We are deciding to wait on the ERV/HRV, as it sounds like we need better air purification. I decided to change EVERY filter in the house including the furnace filter (MERV 13), all 3 air purifiers, vacuum HEPA filter, etc. and we already noticed a difference. I think for me, the key may be replacing the filters more often than not. Instead of trying to save a buck by prolonging their life, I will change them before they get bad.

    I'm working on quotes for a 5" media HVAC filter upgrade, as that should be worth the small amount and allow our system to breath better. I think the MERV13 1" filter is restricting air-flow now. We can't upgrade duct-work without tearing up drywall throughout the basement, so that's the last thing I'd want to do.

    We need all new windows. They are known cheap windows (company went out of business, as usual), and a few of them have split open. Big expense we are saving up for. Any suggestions there would be a appreciated too but that's another topic right!

  6. #6
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    If you are okay with keeping up on filter maintenance I recommend an EAC rather than just a thicker filter they typically have less resistance over a pure media filter so you may not need any extra duct upgrades.

  7. #7
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    Only thing I can suggest is about getting tested for your allergies. I did that once and like I mentioned dogs and certain weeds. I wasn't willing to give up my cats and dogs so like might be said "live with it"
    The super low humidity where I live causes more dust than Ill. A lot more. I don't know how effective an air filter will be with what ever is irritating you. They do little for my problem. Also remember most of the air in a home never makes it to the filter. The model of air flow a few years ago would show a room with big arrows showing the air entering the return with the arrows gradually getting smaller the further away from the return. Modern instruments show in most cases not true. Almost all the air entering the return is within a few feet from the grill. But you have so many you probably have more effective filtration. An air filter won't clean a house and isn't an air purifier, just a dust collector so it might improve things but might not solve them if the allergen is still present..
    I can buy filters with specially treated with charcoal or other attributes but those are for places with serious contaminants like nail salons and acetone.

    A humidity tester (psycrometer), A cheap one, can be bought for a few $. Not super accurate but close. You can then find if you have poor windows or have an unusual source of humidity and the windows are just the canary in the coal mine.
    Good luck keep waiting for the thaw.
    Give me a relay with big enough contacts, and I'll run the world!

    You can be anything you want......As long as you don't suck at it.

    If a person wants to create a machine that will be more likely to fail...Make it complicated.

    USAF 98 Bomb Wing 1960-66 SMW Lu49

  8. #8
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    Having owned an EAC in the past, I’m going to stick with recommending a media filter instead. An EAC requires thorough monthly cleaning to perform as expected. As the plates get dirty the efficiency of an EAC drops, unlike a media filter that increases in efficiency.
    I find most owners of EACs grow tired of the time and effort involved so it gets neglected.
    *********
    https://www.hvac20.com/ High efficiency equipment alone does not provide home comfort and efficiency. HVAC2.0 is a process for finding the real needs of the house and the occupants. Offer the customer a menu of work to address their problems and give them a probability of success.

    Find contractors with specialized training in combustion analysis, residential system performance, air flow, and duct optimization https://www.myhomecomfort.org/


    Site member map HERE!

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  10. #9
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    The 5" X 24" X 24" -Merv 13 filter is a good start. Remember a dirty filter is a better filter than a clean one. I would not change a filter until it showed dirt.
    Sweaty windows during cold outside temperature indicates that you have a fairly air tight home. Monitoring a home with a CO2 meter will tell you how much fresh air is passing through the home. Cost $100 at CO2 meter.com.

    During winter cold, the stack effect and winter wind forces are high, causing more natural ventilation with fresh air. Windows that sweat during normal occupancy tell us this home needs mechanical fresh filtered air during calm winds and mild temperatures. A fresh air change in 4-5 hours is suggested to purge indoor pollutants and renew oxygen. It is also critical to maintain <55%RH throughout the 3 mild seasons of the year. This prevents mold and dust mites, the common allergens in green grass climates.

    Bring a 6" fresh air inlet from outside and connect the fresh air to your whole house dehumidifier return and share the return with a return from the open part of the home. Using a pair duct dampers on the 6" fresh air duct and the retun duct from the open part to get 80-100 cfm of fresh air blended with the house air at the inlet. The dehumidifier supply should go to the a/c supply and basement to cause circulation of the filtered dehumidifier supply throughout the home. Operate the fan when ever the home is occupied. If your dehu does not have merv 11 filter or better, add one at dehu return.
    This gets you clean fresh air throughout with the dehu maintain <55%RH. This the most important issue. Make sure that there no damp spots.
    The ERV/HRV could reduce you operating cost by $100 per year. Make up air will allow your exhaust fans to function better at they exhaust pollutants from the home. The kitchen hood and clothes drier are of the biggest concerns.

    It takes time to eliminate mold/dust mites allergens from a home.

    These are most critical issues. Calm winds during mild seasons slow natural infiltration down to a fresh air change in +12 hours and allow indoor moisture levels to rise during the damp times of the year. We run across some older homes that are tight enough to cause fresh air issues during mild seasons. After fresh air ventilation, avoid over humidifying the home to the point of window dripping. Moisture also accumulates in the exterior materials of the home and grow mold.


    Keep us post.
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

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  12. #10
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    Your situation is different than mine, but read my thread here anyway:
    https://hvac-talk.com/vbb/showthread...th-musty-smell

    I will just caution you from listening to the 'experts' too much. They tend to just repeat the same tired lines they've been using for years, regardless of any new technology. If they sold cars, they'd be telling you the 1998 Ford F150 is better than the 2020. When they tell you an ERV isn't a good solution, ask them why and ask them to be specific. If they can't be specific then they don't understand what they're talking about. If they are specific, listen carefully and see if the specifics are applicable to you and your situation.

    Again, your situation is different from mine. Adding an ERV solved my 'bad air' issues. But, doing it for an entire house is a bit different and I don't have enough experience to give you good advice on it one way or the other...except to very careful of who you listen to, even on this board

  13. #11
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    Aprilair 5000 filter is a MERV15. Have two in my own home. We had extraordinary forest fires last summer and they kept the air clean running the fan on low continuously. I change media annually.

    Install quality bath fans with short hard pipe ducting and put a hygrostat in the hall to enable their operation in humid situations and use twist timers in the bathrooms for the poo ventilation.

    Bring in a duct to the return air side of the furnace before the filter to replace the air removed by the bath fans.

    This should get you on the way to clean fresh air to alleviate allergies and if need be you can build on this with a whole house dehumidifier. (tight homes do not need added humidity, they need ventilation and de humidification.
    A dying culture invariably exhibits personal rudeness. Bad manners. Lack of consideration for others in minor matters. A loss of politeness, of gentle manners, is more significant than is a riot.
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  14. #12
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    I put in a lot of Aprilaire air filters. Most of my customers can tell a difference but I won’t go as far as to say 100%. To me the design of the Aprilaire media makes a better seal so air has to go through not around.

    HRV will do nothing but complicate your moisture problem. I say this because the HRV does not transfer moisture from one air stream to the other. The result is as it runs in the winter it will be removing moist air and replace it with dry air. In the summer it will take the drier air from your house and replace it with more humid air. Both of these could cause a sizable increase in utility costs.

    ERV will transfer moisture along with the air. This does not mean that it will be the sole device needed to control the humidity in your house. It will work much like the HRV but instead of all the moisture in the airstream being transferred in or out only part will do it does a better job of maintaining the levels you have rather than you having to constantly add or remove.

    There are also YV products that can help with allergies. They work well for some and not at all for others. I have one that I use as a trial. I install it so they can try it for a couple weeks. If they think it helps I put them in a new one, if not I patch a 1” hole and take it to the next place. The experience I have had I don’t think I would buy one with out the trial.

    Hopefully this helps you in your quest for better air.

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  16. #13
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    cfdp,

    You need good filtration to target particles (which includes allergens) and you need outdoor air ventilation to target gases (which includes odors and VOCs). A hospital has both great filtration (HEPA) and great ventilation.

    >For filtration, talk to your three contractors to explore options for higher MERV rated fliters.
    >For ventilation, an ERV would be great, but it's not your only option (exhaust fans and simple outdoor air intake are alternatives). With an ERV, you could turn down your humidifier in the winter (compared to an HRV or simple OA intake) as it will retain much humidity. I'm in Chicago and my experience is that most "normal" HVAC companies don't have the knowledge and experience to install ERVs correctly. No surprise 2 wouldn't even give you quotes.

    I second the recommendation to visit an allergist to know what you're allergic to (mold, dust mites, grass pollen, etc). That can help you better focus on the corrective actions that will have the most benefit.
    Ian Cull, PE, CIH
    Indoor Science
    Chicago, IL

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