I'm still learning about this stuff, so bear with me.

I'm trying to better understand the ERV/HRV thing and I have some questions.

Is an ERV/HRV only desirable if my ach is extremely low? Say less than 2.0? Is there any reason not to install one if the ach of the building is a bit higher and already has enough ach?

I've heard it said before that the places for an ERV/HRV is the bathroom and the kitchen because they are likely to produce the most moisture in the building. Do they take the place of an exhaust fan in any case?

Does an ERV/HRV tend to run continuously or does it turn on and off?

Does an ERV/HRV tend to run continuously or does it turn on and off?

Lots of different schemes for running the ventilation. A common one is to have it run every hour for 20 minutes. If you want to get precise about it, you can have it run just enough each hour to get your air changes to the desired level. I think some run continuously at a low volume and have switches installed in the kitchen or bathrooms which will boost the volume up for a set period before it ramps back down. I have an Ultimateair RecoupAerator with humidistats which cause the fan to go to high speed when the humidity is above a certain point (bathrooms).

I've heard it said before that the places for an ERV/HRV is the bathroom and the kitchen

Those are good places for the exhaust inlets. Other ones might be the laundry or a walk-in closet. The supply outlets go well in bedrooms so you have fresh air all night long.

If you have a leaky home, what's the point of an HRV? You might be losing five times as much heat through your leaks, and the fresh air is coming in the same way so what is the point of spending money to recover the heat from a bit more ventilation? Bathroom and kitchen fans already remove moisture and odors

Posted By strategery on 02 Aug 2012 07:19 PM
I'm still learning about this stuff, so bear with me.

I'm trying to better understand the ERV/HRV thing and I have some questions.

Is an ERV/HRV only desirable if my ach is extremely low? Say less than 2.0? Is there any reason not to install one if the ach of the building is a bit higher and already has enough ach?

I've heard it said before that the places for an ERV/HRV is the bathroom and the kitchen because they are likely to produce the most moisture in the building. Do they take the place of an exhaust fan in any case?

Does an ERV/HRV tend to run continuously or does it turn on and off?

Some people bypass having a kitchen exhaust fan with an ERV/HRV. Depends on how much smelly food you plan on cooking.

Did you do a Blower Door Test on your home? What kind of home is it (wood frame, insulation type)?

It's a wood frame house. Insulation is a combination of spray foam, cellulose and fiberglass. It's a pretty tight house.

It's going to get even tighter when I re-side it. I'm going to use some foamboard and either dense pack cellulose or maybe flash and batt with foam and fiberglass.

I had the attic floor sprayed with a layer of foam and the rim joists also hit with foam. Basement walls have foamboard, taped at the seams with some canned foam used to fill in gaps.

Posted By ICFHybrid on 02 Aug 2012 09:08 PM

Lots of different schemes for running the ventilation. A common one is to have it run every hour for 20 minutes. If you want to get precise about it, you can have it run just enough each hour to get your air changes to the desired level. I think some run continuously at a low volume and have switches installed in the kitchen or bathrooms which will boost the volume up for a set period before it ramps back down. I have an Ultimateair RecoupAerator with humidistats which cause the fan to go to high speed when the humidity is above a certain point (bathrooms).

Those are good places for the exhaust inlets. Other ones might be the laundry or a walk-in closet. The supply outlets go well in bedrooms so you have fresh air all night long.

So in your house is it hooked up to a central hvac system? I have a pretty new furnace and ac and I might be re-doing the ductwork soon.

So in your house is it hooked up to a central hvac system?

No - all radiant and minisplits.

We had a forced air furnace and HRV in our last house. We had the basic HRV control, so our options basically were off/run constant on low/run constant on high. We built a very tight house & when I turned the HRV on you could tell within a short time. The air was much fresher & more comfortable, so it ws extremely effective. The downside (and the reason that I would turn it on/off manually instead of leaving it on) was that in the winter it brought the humidity level down to a very uncomfortable level - my little walmart meter hovered around 15% the whole time it was on. When I turned the HRV off it would climb up to around 30-40, depending on whether I was cooking, shower had been going, etc.

We're building again in the next 2 years or so - I'm not sure if an ERV would help this situation or if we're going to need to get an Aprilaire..

Posted By jerkylips on 03 Aug 2012 05:04 PM
We had a forced air furnace and HRV in our last house. We had the basic HRV control, so our options basically were off/run constant on low/run constant on high. We built a very tight house & when I turned the HRV on you could tell within a short time. The air was much fresher & more comfortable, so it ws extremely effective. The downside (and the reason that I would turn it on/off manually instead of leaving it on) was that in the winter it brought the humidity level down to a very uncomfortable level - my little walmart meter hovered around 15% the whole time it was on. When I turned the HRV off it would climb up to around 30-40, depending on whether I was cooking, shower had been going, etc.

We're building again in the next 2 years or so - I'm not sure if an ERV would help this situation or if we're going to need to get an Aprilaire..

You can use a percentage timer control , that is adjustable to run the ERV/HRV anywhere from 1 minute to 60 minutes every hour, this will enable you to reach a happy medium

•Percentage Timer Control with Furnace Interlock •Primary control for RenewAire Residential ERV Models EV70, EV130, EV200 and EV300 when Furnace Interlock is needed and PBL is not used •Requires 24VAC power •Will provide simultaneous furnace blower operation during ERV operation •Runs unit an adjustable amount of time every hour •Constant "on" and "off" capability •Uses six wires for complete connection between ERV and furnace •Can be used to control any

thanks Chris.. I had a thought about upgrading the control, but at that point we were already thinking we may sell so we didn't. Also, here in WI, the air gets really dry in the winter. In our old house (prior to the the one wth the HRV) it was extremely dry with just the furnace running. Granted, that house was older & not nearly as tight, but it made me question if the upgraded controls would be enough to make a difference or if the money would have been better spent on the humidifier.

On the exterior of the home with an ERV/HRV, how big are the intake and exhaust vents?

In scorpion and bug country, how does one prevent bugs from crawling into either vent?

I think it's gonna be 6" or 8" in all the units I ever looked at. My Recoupaerator has 6" duct collars, but an 8" trunk (and vent cap) to the outside was recommended.

I found these Seiho Vent Caps and used them because they look cool. I got Model SFX-N which has the optional insect screen. Make sure you get that when you order.

http://www.seiho.com/product/sfx/sfx.html

Posted By ICFHybrid on 19 Aug 2012 11:55 PM
I think it's gonna be 6" or 8" in all the units I ever looked at. My Recoupaerator has 6" duct collars, but an 8" trunk (and vent cap) to the outside was recommended.

I found these Seiho Vent Caps and used them because they look cool. I got Model SFX-N which has the optional insect screen. Make sure you get that when you order.

http://www.seiho.com/product/sfx/sfx.html

Thanks!

8" + sounds about right. I assume the exhaust and intake vents should be separated by at least 2 feet, right?

The website didn't have any pics of what the bug screen looks like. Do you have a bug screen on yours? I wonder how much airflow the screen cuts down on?

Did you use a Seiho dryer vent?

No, it's called an aluminum vent cap and it looks very similar to the dryer vents, but it has a different model number. I ordered them on three separate occasions and made a mistake once, ordering the dryer vent instead. I ordered some extras, because I wasn't sure about the sizes I'd need, but everyone who saw one wanted to buy them off me, so I ended up with ZERO extras.
The instructions say to separate the vents by a minimum of 6 feet either horizontally or vertically. I located them on different sides of the building so they would be subject to different air conditions for positive mixing.

The insect screen wire is quite light and the holes are fairly big. I don't think it offers any restriction to the airflow.

Posted By ICFHybrid on 20 Aug 2012 01:46 AM

The instructions say to separate the vents by a minimum of 6 feet either horizontally or vertically. I located them on different sides of the building so they would be subject to different air conditions for positive mixing.

The insect screen wire is quite light and the holes are fairly big. I don't think it offers any restriction to the airflow.

I will do the same and separate the vents by putting them on opposite walls.

Do you have a pic of the insect screen? Too big of holes will let in bugs. If you have pics of your ERV/HRV setup, I would love to see them.

I am looking for a dryer vent that closes properly when not in use so it doesn't let out indoor air or let in bugs or critters.

I don't have a picture of the insect screen and neither does Seiho (when I last looked). I will see if I can't get a chance to go up and take a look at it again, but I recall that one of the tradesmen who saw it said it was very well designed to keep out bees (he was a beekeeper). I was worried about the same thing, but I finally decided nothing was as good as a brief seasonal inspection and cleaning, if necessary.

Seiho has the dryer vents in the same line and I think they have energy-saving flappers on them.

I presume you are interested in a picture of the actual HRV interior installation as all the outside images show are.....the Seiho vents.

Posted By ICFHybrid on 20 Aug 2012 10:31 AM


I presume you are interested in a picture of the actual HRV interior installation as all the outside images show are.....the Seiho vents.

Yes, please. The interior system pics is what I am looking for. THANKS

Here it is

Posted By ICFHybrid on 20 Aug 2012 09:44 PM
Here it is

Is that attic within the thermal envelope of the home?

Yup.

I’ve got a couple of questions concerning some research I’ve done and a couple things mentioned in this thread. When reading a book on designing a healthy home it says that good places for intake vents are in a closets and bathrooms. (I saw that mentioned here also.) I also know that many people install ERV/HRVs using existing HVAC duct work. However, I was recently doing some research in the IRC and while I couldn’t find anything on ERV/HRV they did say the return vents were not allowed inside closets and bathrooms! This had me scratching my head and I could only speculate that they were concerned about the moisture (in the bathroom) and maybe high level of bad air in the closets would be circulated around the house. It also made me think that if I wanted to pull nasty and moist air out of those places (besides a direct vent to the outside) that the duct work for the ERV/HRV would have to be a separate system. I would love to hear your thoughts or experience on this?

What are your thoughts on using a separate duct system for the ERV/HRV?

Thanks for the tips on the Seiho vent caps!