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Ben,
 
I think HRVs definitely save heating energy in a cold climate, though the annual efficiency is likely less than the factory ratings. But, as with any technological "solution", they may have unintended consequences.
 
One study I've seen showed that "pressure-balancing" HRVs don't really create zero pressure. If the intake and exhaust fans move the same CFM of air and the incoming air is much colder than the outgoing air, the incoming air will expand as it warms and thereby result in more CF in than out. This will create a positive pressure in the conditioned space, which - added to whatever stack effect pressure there is above the neutral plane - will exacerbate any leakage of humid air through the thermal envelope.
 
While an exhaust-only system "wastes" heat, it is the only mechanical ventilation system which maintains a negative pressure everywhere within the conditioned space and virtually eliminates air exfiltration into the thermal envelope.
 
So, where the trade-off falls is anybody's guess. But since my bias is toward KISS, and I build very tight but not hermetically-sealed houses, I have used only exhaust-only systems.
 
- Robert
 

--- On Tue, 4/7/09, Ben Graham <[log in to unmask]> wrote:
From: Ben Graham <[log in to unmask]>
Subject: Re: Point vent heat exchangers
To: [log in to unmask], [log in to unmask]
Date: Tuesday, April 7, 2009, 4:44 PM

Robert,
I am not interested in an ERV.  I have not been able to source p.o.u. HRV.
Have you ever tempered incoming air on a HRV, or do you not think they are efficient enough for cold climates?

Ben


On 4/7/09 1:17 PM, "Robert Riversong" <[log in to unmask]> wrote:

Ben, et al:
 
The Panasonic FV-04VE1 seems like a higher-tech version of the old Mitsubishi point-of-use HRV, except the Panasonic is an ERV which exchanges moisture as well.
 
If one of the purposes of an exhaust fan is to evacuate moisture, then it makes no sense to recycle it back in (other than saving the latent heat of the water vapor). Also, like all ERVs, this one is less than ideal in a cold climate.
 
To prevent freeze-up, instead of an electric resistance defroster (which some larger units have), the Panasonic simple closes off the incoming air for a while - making it an exhaust-only fan. So if the purpose is also to keep the indoor pressure balanced, it won't do that in weather below 32 very well and not at all below 20.

--- On Tue, 4/7/09, Ben Graham <[log in to unmask]> wrote:
From: Ben Graham <[log in to unmask]>
Subject: Re: Point vent heat exchangers
To: [log in to unmask]
Date: Tuesday, April 7, 2009, 11:58 AM

Thanks,
Any experience with this one?


On 4/7/09 11:12 AM, "Konrad Scheltema"
<[log in to unmask]>
wrote:

> Panasonic has one in their whisper line
>
> Konrad
>
>
> On Apr 7, 2009, at 10:54 AM, Ben Graham wrote:
>
>> Does anyone know of domestically available point source heat exchange
>> ventilator like the vent-axia from abroad?
>>
>> Ben
>>
>> Those who give up freedom for safety, deserve neither.
>> Benjamin Franklin
>> __________________________________________________________
>>
>> Ben Graham
>> www.naturaldesignbuild.us
>> Natural building/design services/workshops/consulting
>>
>> Integrating Culture and Nature
>> 802.454.1167
>
> Konrad Scheltema
>
> Evergreen Homebuilders LLC
> 121 March Davis Drive
> Guilford, VT 05301
>
> Phone/Fax (802) 246-1600
> Cell   (802)380-6437
> email  [log in to unmask]
> Web  www.evergreen-homebuilders.biz

Those who give up freedom for safety, deserve neither.
Benjamin Franklin
__________________________________________________________

Ben Graham
www.naturaldesignbuild.us
Natural building/design services/workshops/consulting

Integrating Culture and Nature
802.454.1167



Those who give up freedom for safety, deserve neither.
Benjamin Franklin
__________________________________________________________

Ben Graham
www.naturaldesignbuild.us
Natural building/design services/workshops/consulting

Integrating Culture and Nature
802.454.1167