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Thread: HRV or ERV

  1. #1

    HRV or ERV

    Hello All. I am seeking help on a HRV vs ERV for a whole home remodel. I have gotten recommendations for both...so I am confused and looking for additional insight.

    My particulars
    Location: Prior Lake, MN
    Home: walk out rambler (~1,550 sq ft down and up with 9' ceilings down and 12 ft. up)
    Carbon Units: 3 people
    Equipment installed in 2006:
    - Down: American Standard Comfort R 60,000BTU, Aprilaire 2400 media, Honeywell UV100E, and Aprilaire 600 humidifier (including outside temp control) controlled with a Honeywell Pro 6000.
    - Up: American Standard Comfort R 80,000BTU, Aprilaire 2400 media filter, and Honeywell UV100E controlled with a Honeywell Vision Pro 8000.
    - AC: American Standard 14 SEER 2 1/2 ton with ducting up and down.
    Remodel Changes Occurring Now:
    - basically wood floors throughout
    - Andersen 400 windows
    - closed cell foam on entire shell (6" studs down, 4" up and above the ceiling) with remaining attic getting an additional 38R
    - changing out a standard 50 gallon water heater to a powered direct vent unit
    - 6 burner gas stove top with a 300 CFM vent hood

    My questions:
    1) Do you recommend an HRV or an ERV? Size?
    2) Would you integrate the controls with the Vision Pro 8000 - assuming you can? If not, should I get a new controller?
    3) Do I need make up air given the tightness of the house?
    4) Anything else I should consider to provide a high quality home environment?

    Thank you!
    Mike

  2. #2
    I am surprised that I haven't gotten any responses when I see every other post has gotten several. Should I clarify that I have hired a contractor and I am not a DIYer and never would be for this kind of thing? I have hired a local contractor, Lein Heating, to do my work. He recommended an HRV. But, I have subsequently spoken with two other contractors (introduced to me through a friend who is in the energy efficiency industry) and one recommended an HRV and the other an ERV. I am just trying to learn so I can participate in the decision my contractor makes. I believe there are always different ways to do things and I am the one who has to live with the results so I would like to be an informed customer...that is all.

  3. #3
    Join Date
    Nov 2001
    Location
    East Texas
    Posts
    949
    Around here they simplify the whole deal and just bring in outside air via a duct from a roof vent to the return. I always see a 6 inch duct for this run. With manual damper.

    The size of the A/C unit is sized as if the home is just using wall batts and blown in attic insulation. This way it can still handle the additional outside air load.

    Simple, and it works.

  4. #4
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,319
    usually erv's are for hot climates, hrv's for cold climates.
    there are other options besides these two.

    passive make up air systems
    whole house ventilation systems

    I'm not familiar with cold climate requirements.
    perhaps Teddy bear will have time to reply soon.

    do you know how much fresh air is required?
    ashrae 62.2 ventilation should be consulted.
    hvac company should have information.

    to me, adding fresh air without knowing tightness of the
    house isn't a good thing. foam insulation doesn't always
    seal as tightly as the company promotes it to be.
    I always test the house for air tightness first..then use
    that information to determine how much fresh air is needed.

    can your friend in the efficiency business help you to have
    house tested & ductwork tested? you would be suprised
    at amounts & locations of leakage.

    best of luck.

    PS like the carbon units ..
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  5. #5
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,062
    Quote Originally Posted by MikeMy View Post
    Hello All. I am seeking help on a HRV vs ERV for a whole home remodel. I have gotten recommendations for both...so I am confused and looking for additional insight.

    My particulars
    Location: Prior Lake, MN
    Home: walk out rambler (~1,550 sq ft down and up with 9' ceilings down and 12 ft. up)
    Carbon Units: 3 people
    Equipment installed in 2006:
    - Down: American Standard Comfort R 60,000BTU, Aprilaire 2400 media, Honeywell UV100E, and Aprilaire 600 humidifier (including outside temp control) controlled with a Honeywell Pro 6000.
    - Up: American Standard Comfort R 80,000BTU, Aprilaire 2400 media filter, and Honeywell UV100E controlled with a Honeywell Vision Pro 8000.
    - AC: American Standard 14 SEER 2 1/2 ton with ducting up and down.
    Remodel Changes Occurring Now:
    - basically wood floors throughout
    - Andersen 400 windows
    - closed cell foam on entire shell (6" studs down, 4" up and above the ceiling) with remaining attic getting an additional 38R
    - changing out a standard 50 gallon water heater to a powered direct vent unit
    - 6 burner gas stove top with a 300 CFM vent hood

    My questions:
    1) Do you recommend an HRV or an ERV? Size?
    2) Would you integrate the controls with the Vision Pro 8000 - assuming you can? If not, should I get a new controller?
    3) Do I need make up air given the tightness of the house?
    4) Anything else I should consider to provide a high quality home environment?

    Thank you!
    Mike
    HRV will be used in your geographical area. Once you determine the air changes per hour as recommended by energy rate La. make sure you ad make up air for your kitchen hood. IMC 505.2 requires make up air when cfm air exhaust is 400> but that is with a normal amount of air infiltration.

  6. #6
    Quote Originally Posted by second opinion View Post
    HRV will be used in your geographical area. Once you determine the air changes per hour as recommended by energy rate La. make sure you ad make up air for your kitchen hood. IMC 505.2 requires make up air when cfm air exhaust is 400> but that is with a normal amount of air infiltration.
    Thanks Timber, Energy Rater LA and second opinion. I think you have confirmed that we need more information, i.e. the blower door test, before making the right decisions. I trust my contractor knows the codes and requirements to calculate the air needs but he wasn't going to do a blower door test. I will have that done before determining next steps on the NRV and make up air, if any. Maybe this says something about the guy I was working with - selected by my general.

  7. #7
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,319
    never assume what the contractor knows.
    you may be his education process.

    who was the guy you were working with that was selected
    by your general? is this the energy efficiency person?
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  8. #8
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,638
    Quote Originally Posted by MikeMy View Post
    I am surprised that I haven't gotten any responses when I see every other post has gotten several. Should I clarify that I have hired a contractor and I am not a DIYer and never would be for this kind of thing? I have hired a local contractor, Lein Heating, to do my work. He recommended an HRV. But, I have subsequently spoken with two other contractors (introduced to me through a friend who is in the energy efficiency industry) and one recommended an HRV and the other an ERV. I am just trying to learn so I can participate in the decision my contractor makes. I believe there are always different ways to do things and I am the one who has to live with the results so I would like to be an informed customer...that is all.
    If you have exhaust devices that need make up air like a clothes drier, wood burner, water heater, fireplace and kitchen exhaust hood, consider that erv/hrvs do not provide makeup for this purpose. I tested a foam insulated house with an ERV in WI. The erv is controlled by a CO2 controller that detects when the home is occupied and not getting enough natural air change to operate the ERV. The ERV was needed <20% of the time. During cold windy weather, most homes get enough fresh to not need the benefits of the erv/hrv. During calm winds and moderate temps, these homes need fresh air when occupied. ERV/hrvs save very little during moderate temps.
    If you have a fireplace, stack chimeney water heater or a wood burner, use makeup fresh air ventilation. If you have no open combustion devices, your choice. Most energy aware users opt for the hrv. Keep in mind that you need mechanical fresh air ventilation most during moderate weather. When the outdoor dew points are +55^F, you need dehumidification in your basement. During days of low/no cooling loads, your entire home need supplemental dehumidification. Whole house dehumidifiers are ideal option with open combustion devices to avoid backdrafting.
    Keep us posted on the systems and the results.
    Regards TB
    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"

  9. #9
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    7,760
    Definitely get a blower door test. It will let you know how well they spray foamers did. If you let them know you are getting a blower door test they will probably make sure and do a better job sealing the building envelope. GC's often don't use the caliber of hvac guys that I would want installing my equipment, some do but most go with a relatively cheap company and cheap equipment. They also oversize equipment a lot of times IMO. Best of luck to you. To answer your original question Hrv is for cooler climates, erv for warmer climates

  10. #10
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Honestly, I've done some math in the past, and at $$$$ installed, the payback is something like 10+ years for a HRV.

    For only a little more than the price of a dedicated HRV, you could install a ventilating dehumidifer upstairs and upgrade to a Visionpro IAQ up there, then just install a 6" fresh air make-up on a damper for the downstairs and consider adding a relay to open fresh air damper and cycle the blower when the kitchen hood is running.

    This is just what I would install in my home... especially if it was well insulated and tighter. Its' actually on my future to-do list, but I have a few other expenses ahead of it first.

  11. #11
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,319
    what we have done sucessfully in the past decade or so, (after determining
    amount of fresh air needed) is this:
    12x12 filter back grill on exterior. usually located in soffit,
    porch or patio ceiling..depending on orientation & height.
    access needs to be easy as filter will require changing.
    duct (6" usually again dependent upon amount of cfm needed)
    barometric damper (like the skuttle 216) set to required cfm
    duct to return side of hvac.
    all mastic sealed of course.
    fresh air is cleaned, measured and dehumidified before entering house.
    cost less than half of erv, don't know about hrv.
    no mechanical parts to worry about, no operating expense.
    barometric damper has a weighted arm that adjusts to different
    damper settings.

    of course this is putting the cart before the horse if you
    don't know what cfm is required.

    there are several ways to add fresh air.
    some more affordable and cost effective than others.

    I've seen erv's installed badly on several ocassions. the above
    install is fairly straightforward and can be done by hvac company
    with a minimum of screw ups. in my experience.

    best of luck.

    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  12. #12
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,638
    Just a few throughts about your selection of equipment.
    ASHRAE suggest fresh air as follows.
    7 cfm per design occupant, 3 bdrm = 4 X 7 = 28 cfm
    1 cfm per sqft. of space, 1,500 + 750 basement = 25 cfm
    Call it 60 cfm when occupied. This is an air change in 6 hours.
    Your average winter temp is ?? if 15^F, heating to 68^F with 80% eff. furnace is <20 therms of ng.
    An HRV will save 50-60% or ?? No more than 20 therms per year.
    Add the fact you are dealing with make up air for your clothes drier, power exhaust water heater, or kitchen hood.
    If there is no possibility of backdrafting anything, maybe make-up air is not important.
    Regardless, there is low payback on HRV.
    A whole house ventilating dehumidifier would provide 60 cfm of filtered fresh make-up air ventilation when the home is occupied. In addition, the home would have humidity control when the outdoor dew points are +55^F and the a/c is not running enough.
    You will need dehumidification with an HRV.

    I tried to explain this to a friend building a foam home and here is what happened.
    He bought an ERV and a VS speed a/c for fresh air and humidity control on the recommendation of his contractor and general info.
    He was unable to maintain <50%RH during the three mild seasons of the year. We added a 70 pint whole house dehumidifier and it all works. He added CO2 controller to operate fresh air when needed in March. The ERV operated <19% of the total time during April. We are collecting data. During the mild temps and calm winds the fresh the ERV operates when occupied which is about 55% of the time. The ERV has a very long payback. The home operates with a negative pressure whenever any exhaust device operates, but there are no chimineys in the home.
    Personally, I would only suggest ERV/HRVs is you have electric restance heat, an unusal need for large amounts of fresh air 24/7, or you wanted a home with all of gadgets. I am sure everyone living in MN thinks a HRV is good. In the old days, I sold many HRVs.
    Today the basics are a whole house ventilating dehumidifier with a good a/c, bath fans, and all sealed power exhaust appliances. Either an occupancy timer or CO2 controlled fresh air ventilation tied into the a/c ducts with emphisis on the basement. In the middle of winter, seldom is fresh air ventilation needed.
    Regards TB
    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"

  13. #13
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,319
    so even in cold climates whole house dehumidifiers are used?

    I read a lot about cold climates and humidifiers..which is why
    in my first post I left it at whole house ventilation systems.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

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