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HRV (heat recovery Ventilation), ERV

Discussion in 'The DIY Room' started by bushpilot, Aug 9, 2016.

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  1. bushpilot

    bushpilot

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    I am tightening up our house significantly. Not too hard to do, unfortunately.

    Anyway, I am thinking of adding a HRV or ERV. Does anyone have experience, and can give advice? How to size, installation pointers, brands, HRV vs ERV, etc?

    Do it or not?
     
  2. Viking80

    Viking80

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    I'm sure someone with more relevant knowledge will chime in, but in the mean time:

    We have HRV ("balanced ventilation") in our house. The house is old, so we had to put it in afterwards. Cost a pretty penny, but worth it I think. I kinda feels like sleeping with the windows open, as an example in regards to the bed room. It also circulates heats around the house a bit. Lastly it felt right as out chief carpenter did spend quite a bit of our money to make the house tight.


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  3. yooperdave

    yooperdave

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    Just even adding an fresh air intake would help for a supply of fresh air.

    The HRV would not only supply but also exhaust the air. Can be stand alone or hooked up to your furnace ducting and used with the aid of the furnace blower motor.
     
  4. bushpilot

    bushpilot

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    Furnace? Don't have one of them. I am thinking about a stand-alone HRV.
     
  5. fuelrod

    fuelrod

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    It might be worth having a "blower door test" done to see just how tight you got the house before you spend the bucks. I think that only spray foam insulated or "SIP's" construction is actually tight enough to warrant the expense.
     
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  6. ironpony

    ironpony

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    So let me make sure I understand this, you spent time and money making your house so tight, now you have to spend more money to make it loose again?
     
  7. bobdog2o02

    bobdog2o02

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    Yup, that's it.
     
  8. Minnesota Marty

    Minnesota Marty

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    bushpilot,
    As a general contractor or the last 25+ years here in Minnesota where we have spent considerable money and effort to build and remodel energy efficient house. Having a energy code along with the standard building code, I would tell you this. By doing a blower door test, with thermal imaging, you will be able to determine how successful you were in tightening up your house. The person that does the test will be able to tell you how many air exchanges are happening naturally in the homes without a air to air exchanger system.
    I built my final home two years ago. I ventilate the house with a very good low decibel $200 exhaust fan that I turn on when I feel the air in the house stagnating.
    It is very difficult to tell you that you need a air exchanging system or not without a blower door test. In our area blower door test $300 to $400. The that you don't have a central ducted air furnace does add a twist to the equation.
     
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  9. Viking80

    Viking80

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    Marty; How do you let air in? Windows? How about damp places like bathroom etc. ?


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  10. chris

    chris

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    old school intake-- Duct through wall down inside of wall to a moderate sized box on floor. New duct from box back to ceiling weaving back and forth or several loops across ceiling ( this in a basement) then termination by appliance ( if you have forced air heat- can terminate into cold return) Didn't have those fancy high dollar rigs in the way back. Looping across ceiling( or up and down a wall) allows the incoming air to be tempered somewhat before termination.
     
  11. ivanhoe

    ivanhoe

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    If you have sweaty windows when it's starting to get cold outside is a tell-tell sign. Grab yourself a hygrometer [​IMG] to see the humidity level in the house.
    Healthy indoor air is better for you in the long run. Make sure if you get a air exchanger with the heat recovery module.
     
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  12. bert the turtle

    bert the turtle

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    Make sure the person who installs it knows what he is doing. My system was designed to bring fresh air in to the ends of the house and exhaust it out past the toilets. The goofballs that installed mine first installed it backwards. Then they argued with me about it. Then they switched everything around so it was all going according to the design.

    What they didn't do was manage to balance the recirculated air to the fresh air (critical to proper heat and moisture exchange) so what I have is essentially a blower bringing in outside air. May as well just open the windows. None of the HVAC guys around here seem to know anything about it, so I'm going to have to do it myself this winter.
     
    Last edited: Sep 24, 2016
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  13. Viking80

    Viking80

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    Sorry but lol; they sent air from the toilets through the house and out?


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  14. bert the turtle

    bert the turtle

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    Until I set things straight.
     
  15. bushpilot

    bushpilot

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    :rofl: :lol::rofl: :lol::hair::hair::wacky::wacky::doh: :headbang::headbang:
     
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  16. williaty

    williaty

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    1) Occupant perception of air quality is widely regarded (in the Building Science discipline) as pretty much useless because people pretty much can't sense anything other than smells and humidity and there's a LOT of Indoor Air Quality problems that happen long before you can smell it or feel wet. By exchanging the air on a planned basis, you avoid IAQ problems that can affect long term health but go un-noticed by the occupants.

    2) Yes, you seal the house up and then deliberately make it leak a bit with a HRV/ERV. There's several reasons why this is a good idea. First, this method ensures you know where your incoming air is coming from and how it's getting to your lungs. Much better to pull the incoming air through a planned vent and duct than to pull it in through every little mold, dust, and mouse poop laden crack in your building. Second, natural air leaks let 100% of the energy stored in the air leave the house. So you're constantly paying to raise (or lower) the air temperature from your outside air temp to your inside air temp. A HRV/ERV passes off some of the energy from the incoming air to the leaving air. Good ones move <80% of the energy. So you pay a LOT less to heat/cool your incoming air compared to natural leaks.

    3) The somewhat agreed upon level at which mechanical ventilation becomes necessary is around 5 ACH50. If you haven't had a blower door test to see what your ACH50 is, then you need to do so.

    4) The difference between the HRV and the ERV is humidity. HRV exchanges only heat between the incoming and outgoing air. ERV exchanges heat and humidity between the incoming and outgoing air. In the winter, when you raise the air temp, the relative humidity in the air drops. So constantly bringing new air into the house constantly lowers the relative humidity in the house (which is why stoves without an OAK dry out the house over the winter). The ERV will take some of the humidity that's inside your house and move it over to the incoming air so that you don't get as dry in the winter. You really should consult an expert about whether an ERV or HRV is better for your local climate.
     
  17. Viking80

    Viking80

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    Thanks for that well written and thought out post, Will.


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