[Greenbuilding] One more question on AC

Gennaro Brooks-Church - Eco Brooklyn info at ecobrooklyn.com
Tue Jul 9 15:37:12 MDT 2013


Congrats on the PH job Alan!


Gennaro Brooks-Church
Director, Eco Brooklyn Inc.
Cell: 1 347 244 3016 USA
www.EcoBrooklyn.com
22 2nd St; Brooklyn, NY 11231


On Tue, Jul 9, 2013 at 5:31 PM, Alan Abrams <alan at abramsdesignbuild.com>wrote:

> on my current passive house project (pre-certified in May; permit issued
> today!) I opted for separate distribution systems for ventilation and for
> heating and ac.  there were too many unique conditions throughout the house
> (different floor levels; different solar exposures and shading conditions;
> different functions, such as cooking, bathing, laundering, etc) to rely on
> a gently puff of ventilation air to heat, cool, and dehumidify--while still
> exhausting stale air and bringing in fresh air in appropriate volumes
> throughout a complex floor plan.  Conversely, if the ducts are sized for
> max loads, then it would be optimistic to try to push properly metered
> ventilation air through that system while the heat pump was not running.
>  Thus dual ducting.
>
> the heating and air will be an inline Fujitsu, about 18KBtu capacity.
>  It's oversized for the calculated loads, but only to push enough volume to
> handle dehumidification and prevent hot spots.  One concern is overheating
> in shoulder months, when the leaf cover is gone and the sun is lower than
> the overhangs--which are tuned for summer shading and max winter
> gain--IOW's we anticipate days where some cooling may be required in the
> afternoon, and heating is required later at night.
>
> at a ton and a half, it raises the question of why not just go with a 2
> ton Carrier Infinity, with almost twice the fan capacity--but still able to
> wind down to maybe 3KBtu.  But we decided to do a fine tuned duct system,
> reducing the trunk at each tap, with sweeping takeoffs and boots, to reduce
> friction where-ever possible.
>
> this all is counter to the passive house legend--that when you hit some
> sweet spot of insulation, you only need a small scale ventilation air
> distribution system to distribute heat and cooling--thus justifying the
> premium for the 9 inches of insulation under the slab--but I think that
> dealing with our latent loads dispels that myth.
>
> -AA
>
>
>
> On Tue, Jul 9, 2013 at 4:55 PM, Gennaro Brooks-Church - Eco Brooklyn <
> info at ecobrooklyn.com> wrote:
>
>> Combing ERV/HRV and cooling is a huge question. Does anyone have
>> experience with a new system where you can plan for the ductwork? In that
>> can could you install large ducts and run the ERV and some sort of cooler
>> in the same ducts? In that case I think it may be better to find some
>> inline cooling system instead of jerryrigging a minisplit to work inline?
>>
>> Gennaro Brooks-Church
>> Director, Eco Brooklyn Inc.
>> Cell: 1 347 244 3016 USA
>> www.EcoBrooklyn.com
>> 22 2nd St; Brooklyn, NY 11231
>>
>>
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