Helpful? 0

ERV or HRV with these humidity numbers? Also best HRV brand?

I have a humidistat sitting in my house the last few years, and have taken notice of the RH%.

I am concerned that an HRV will dry out my house too much. Location is Toronto which has cold winters (down to -18 celcius) and summers up to 30 and 35 celcius humid

With a forced air system with a humidifier installed, we go down to about 16% humidity in the winter on the coldest days. typical is around 20%-24% . In the summer we are at about 50-54% ish.

with these numbers would an HRV make it too dry, or would the numbers typically be affected only slightly?

Really, I don't know how much the enthalpy moisture transfer really makes a big impact typically on these numbers.

Secondly, I have seen the list of many different brands/offereings
http://www.greenbuildingadvisor.com/blogs/dept/musings/hrv-or-erv

DOes anyone have any comments about which brand is the best besides Watts/CFM at a reasonable price?. Does one brand break down alot? leakage.
It is difficult to find a comparison of all of these brands. I don't know which one to buy

Asked by cory b
Posted Sun, 04/13/2014 - 11:30
Edited Sun, 04/13/2014 - 12:35

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10 Answers

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1.
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Cory,
If you are running a humidifier during the winter, I'm guessing that you have a leaky house. Has your house ever been tested with a blower door? If so, do you know the blower door results?

Humidifiers can cause problems, and many building experts warn homeowners not to use them. If your indoor air is very dry during the winter, that's a sign of a leaky house. The best remedy for this problem is to perform air sealing work.

You may well be right that you don't need an HRV. If your house has a very leaky envelope, you may already be getting too much air exchange during the winter.

Answered by Martin Holladay, GBA Advisor
Posted Mon, 04/14/2014 - 08:19

2.
Helpful? 0

no blower door was performed, but the house is leaky due to the age/construction. how leaky? I don't know. I want an HRV due to IAQ issues which is a far greater concern at this point.

So which brand(s) is the best at a reasonable price? Which are not, and what should I be looking for when shopping for an HRV?

Answered by cory b
Posted Mon, 04/14/2014 - 11:56

3.
Helpful? 0

Cory,
In your original question, you wrote, "I am concerned that an HRV will dry out my house too much."

Now you have informed me, "The house is leaky due to the age/construction. How leaky? I don't know."

Well, it would be useful to know. If you have a house that is both leaky and dry, as I wrote earlier, then I'm not sure that you need an HRV.

When it comes to choosing an HRV, there are many factors to consider: the number of cfm you need, the desired efficiency, and your budget. There is no single answer to your question.

To compare the specifications of different brands of HRVs or ERVs, many people use the product directory published by the Home Ventilating Institute.

Answered by Martin Holladay, GBA Advisor
Posted Mon, 04/14/2014 - 13:16
Edited Mon, 04/14/2014 - 13:17.

4.
Helpful? 0

Cory,

Cost to benefit ratio-wise you should look into a blower door test. Your utility company may sponsor a low-cost audit (~$125 here) with a blower door option (sometimes you have to ask or pay an extra $50). You might learn something else from the audit but I wouldn't count on it. The value of energy audits for knowledgeable owners is in the science (blower door test, IR camera work), not in the marginal audit recommendations. Compared to the dramatic cost of retrofitting an HRV, a blower door test is really really cheap. And if your house is really leaky, what good is your HRV going to do? Do the blower door test and then decide whether you need ventilation. If the idea is to filter your ventilation via an HRV, you need to know first that your old house air leakage won't outweigh the HRV. Right??

Keith
DIYer

Answered by Keith H
Posted Mon, 04/14/2014 - 16:35

5.
Helpful? 0

To clarify,
the primary concern for this situation unfortunately is IAQ, not cost, which is a distant second. The reason for the purchase is for IAQ not for any cost savings.
During my renovation, the house has been air sealed well. Not to the Nth degree but pretty decent.

The HVI index is great for efficiency. But i wonder, in terms of IAQ, does it really matter which unit I buy? Are some more reliable than others?

Answered by cory b
Posted Mon, 04/14/2014 - 17:11

6.
Helpful? 0

What is the specific pollutant(s) you are concerned about?

Answered by David Meiland
Posted Mon, 04/14/2014 - 18:18

7.
Helpful? 0

Cory,

I think it might be tough to manage IAQ with an HRV if the house is really leaky because you won't have as much control over where air is entering/exiting you home. The blower door test is part of a process to identify leaks and seal the big ones. After that, you can pick the ERV/HRV from the HVI site that best matches your budget and requirements and effectively manage IAQ.

Answered by Scott Tenney
Posted Tue, 04/15/2014 - 13:05

8.
Helpful? 0

Scott,
You make a very good point about the importance of the importance of air sealing in this scenario. I have improved the air sealing (with canned foam), but without the blower door test, you are right, I don't know by how much. So i am assuming it is still leaky.

The strange part about your point, is that if the house is still very leaky, then whatever IAQ issues are present should be removed with the air leakage, should it not?

I am near the point of having to put the house up for sale if I can't solve what is giving me sore throats. I am in the process of "jar testing".

Answered by cory b
Posted Tue, 04/15/2014 - 14:07
Edited Tue, 04/15/2014 - 14:08.

9.
Helpful? 0

Cory,
My understanding is that if the house is leaky, it can lead to IAQ problems because when you can't control where or how much air enters/exits the home, its tough to control humidity and temperature of the incoming air - which can affect IAQ.

Answered by Scott Tenney
Posted Tue, 04/15/2014 - 16:56

10.
Helpful? 0

Without testing it, how do you know it's sealed pretty well?

If it's sealed "well enough" it'll stay above 30%RH/ @ 20C throughout the winter and you would not be adding moisture to the air. It could very well be that the source of the poor indoor air quality is mold growing on the humidifier, for all we really know.

Or if you are keeping the wintertime air too humid indoors, it could be causing mold growth inside the walls (a common problem with humidifier use in cold climates.) In Toronto it's best to keep the indoor RH under 35% for most of the winter to limit the mold hazard, but 30% or above for comfort and to limit airborne virus transmission between avian or mammalian occupants.

Whatever the parasitic path for air infiltration, introducing ventilation air with HRV air from a known outdoor location would add a dilution factor, but if the infiltration path is what's picking up the irritant it may take quite a bit of dilution. More air sealing, and TESTED air tightness may be called for, in conjunction with a dedicated ventilation system.

Unbalanced or un-sealed duct systems can drive outdoor air infiltration, as well as becoming part of the paths picking up and distributing indoor air pollutants. Duct systems and air handlers need to be sealed too, and return paths need to be provided of sufficient capacity for every supply register.

Answered by Dana Dorsett
Posted Tue, 04/15/2014 - 17:59

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