Eli,<div><br></div><div>Your analysis seem correct for your climate. If there is no active source of moisture removal an ERV would only delay the inevitable equalization of humidity between the external and the internal.</div>
<div><br></div><div>However, an ERV will ventilate and help to preserve higher humidity in an air-tight house during cold, dry winters when there are internal sources of moisture generation, i.e moisture from occupants and plants, as well as regular house hold activities such as cooking, and bathing. An ERV probably isn't sufficient on its own to preserve the humidity but it can help.</div>
<div><br></div><div>---- Steve (KZ6LSD)<br>
<br><br><div class="gmail_quote">On Tue, Oct 26, 2010 at 8:42 PM, elitalking <span dir="ltr"><<a href="mailto:elitalking@rockbridge.net">elitalking@rockbridge.net</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Nobody has endorsed my conclusion. This list is my best access to knowledgeable nuance analysis.<br>
<br>
<br>
<br>
If there is not another process to condense the vapor out of the air such as air conditioner, dehumidifier, or desiccants, then there is no benefit to latent heat transfer of ERV.<br>
<br>
<br>
<br>
I am wanting to live without ac or heat pump refrigerant evaporative condensing cycle equipment. They sometimes leak their refrigerant. They also require replacing every 15 years+-. Also, if the company goes out of business, service can become an issue. They also consume electricity with all those issues.<br>
<br>
<br>
<br>
Last summer here in the mountains of Western Virginia; we lived without the use of our heat pump. It was the hottest summer we have experienced. For the most part night time flushing keeps our interior comfortably cooler than outside during the day. After completing the new ceiling thermal barrier before starting on walls, I read 103F outside, 78.7F inside on the floor below the roof. That was the highest outside temperature I have ever read in this location, although, the interior air was humid. My assertion is that the amount of vapor in #/unit volume on a fair weather day (no precipitation) is relatively constant. Only the relative humidity changes with the temperature. The interior daytime air has a higher relative humidity during the day only because air temp is lower. As John Straub says, "ERVs do not dehumidify."<br>
<br>
<br>
<br>
Therefore, if no process has been employed to dry the air out, the ERV will not do so either. The disadvantage of ERV is that there is some air leakage from the latent transfer mechanism that reduces the effectiveness of heat transfer mechanism.<br>
<br>
<br>
<br>
I grew up in Central Florida before air conditioners were common. Last summer, most the time I was able to stay comfortable without our heat pump. During the worst days, light clothing and personal fan was able to achieve comfort. However, the times where that was needed were relatively brief. The days where the low was in the 70's were the worst. They daytime low was more a factor during night time flushing than the daytime high when the house was closed up.<br>
<br>
<br>
<br>
I make the contention that living without compression-expansion refrigerant is a more healthy sustainable lifestyle. So the only reason I can come up with for installing an ERV instead of HRV is because I might change my mind and go for dehumidification. A small high efficiency mini-split could easily do the job.<br>
<br>
<br>
<br>
I am intrigued by the possibility of using desiccants for dehumidification in a tight house. This might provide the alternative to compression-expansion refrigerant equipment. Preserving that possibility might be a reason to install ERV instead of HRV.<br>
<br>
<br>
<br>
Eli<br>
<br>
<br>
----- Original Message ----- From: "elitalking" <<a href="mailto:elitalking@rockbridge.net" target="_blank">elitalking@rockbridge.net</a>><br>
To: <<a href="mailto:john@buildingscience.com" target="_blank">john@buildingscience.com</a>>; <<a href="mailto:greenbuilding-bounces@lists.bioenergylists.org" target="_blank">greenbuilding-bounces@lists.bioenergylists.org</a>>; "John O'Brien" <<a href="mailto:john@boardom.ca" target="_blank">john@boardom.ca</a>><br>
Cc: <<a href="mailto:satjiwan@alumni.brandeis.edu" target="_blank">satjiwan@alumni.brandeis.edu</a>>; "listserv Green Building new" <<a href="mailto:greenbuilding@lists.bioenergylists.org" target="_blank">greenbuilding@lists.bioenergylists.org</a>><br>
Sent: Monday, October 25, 2010 9:48 PM<br>
Subject: Re: [Greenbuilding] ERV strategy<br>
<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
----- Original Message ----- From: "John Straube"<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Short answer again.<br>
ERVs do not dehumidify. The reduce the load on the dehumidifier when and only when it is lower RH indoors than a outdoors.<br>
</blockquote>
<br>
Yes. Then if there is not another process to condense the vapor out of the air such as air conditioner, dehumidifier, or desicants, then there is no benifit to latent heat transfer. However, when you mechanically dry the interior air, the ERV will preserve the value of that dehumidification. Right? Strategies of night flushing cooler high relative humidity at night does not qualify.<br>
<br>
Eli<br>
<br>
<br>
_______________________________________________<br>
Greenbuilding mailing list<br>
to Send a Message to the list, use the email address<br>
<a href="mailto:Greenbuilding@bioenergylists.org" target="_blank">Greenbuilding@bioenergylists.org</a><br>
<br>
to UNSUBSCRIBE or Change your List Settings use the web page<br>
<a href="http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org" target="_blank">http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org</a><br>
<br>
<br>
<br>
</blockquote>
<br>
<br>
<br>
_______________________________________________<br>
Greenbuilding mailing list<br>
to Send a Message to the list, use the email address<br>
<a href="mailto:Greenbuilding@bioenergylists.org" target="_blank">Greenbuilding@bioenergylists.org</a><br>
<br>
to UNSUBSCRIBE or Change your List Settings use the web page<br>
<a href="http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org" target="_blank">http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org</a><br>
</blockquote></div><br></div>