zero energy home and heat pump sizing.... [RE-wrenches]

[Darryl Thayer]

Hi Geoff
I have done two houses in minnesota that were to be
zero energy.  One is close.  

The smaller is 3400 sq ft conditioned.  The heat
source is 12 kW, and it does heat at -20 F.  The house
is very tight (VERY TIGHT) and it has an aire to air
exchanger.  The windows are H windows.  
The 12 kW is of course equal to about 40 kBTU, and
uses direct resistance heating.  The heat is
distrubuted via infloor PEX tubing and antifreeze.   I
am in a 8000 Degree day region.  

The second house is Larger with 4500 Square feet
living area, and in a 9000 Degree day area and is
heated 15 kW, at a design temperature of -30 F.  This
house is also very tight, uses an Air to Air
exchanger, has infloor heat and heat recovery from
several items.  The windows are low e argon, smaller
triple glazed on north, east and west, with large
double glazed on the south.

Darryl
--- Geoff Greenfield <Geoff at Third-Sun.Com> wrote:

> friends, wrenches, countrymen - lend me your ears
> (and brains!)
> 
> While I DO know that the PV panels go shiny side up,
> I am very short on the
> HVAC knowledge - so please give me some help on this
> one!
> 
> I have a great project in design phase - customer is
> doing new construction
> with the goal of net zero energy home.  I am
> comfortable coming up with a
> load analysis/projection of kwh for everything
> except the HVAC plant.  They
> are looking at either a super efficient heat pump or
> possibly geothermal.
> 
> And of course - we are in conceptual stage and have
> no firm plans...  He is
> planning on super insulating (but also wants plenty
> of windows).  He is
> planning on maxing passive solar design with
> calculated overhangs, thermal
> mass etc. In fact the building envelope etc may be
> somewhat driven by the
> "sweet spot" of HVAC sizing (in other words - we may
> throw in some more
> cellulose insulation to keep from jumping from a 2
> ton unit at efficient
> capacity to the next size up...).
> 
> Our target is 2,600 SF of conditioned space located
> in southern OH - I
> (think) we have an annual requirement for 1134 F
> cooling degree days and
> 4927 F Heating degree days (not days but cumulative
> degrees based on 65
> degree comfort - though the customer is happy to
> wear a sweater when it is
> 20 below and let the temp rise in the summer -
> humidity is the target more
> than temp.
> 
> I know that true sizing/energy use projections
> require plans with window
> sizes, wall R-values etc., but at this stage do any
> of you have any rough
> guidance on an approach to finding the kwh of this
> type of system?
> 
> Thanks in advance!
> 
> For a brighter energy future,
> 
> Geoff Greenfield
> NABCEP Certified Energy Practitioner
> 
> THIRD SUN SOLAR & WIND POWER Ltd.
> 340 West State Street
> Athens, OH 45701
> 
> www.third-sun.com
> (740) 597-3111
> 
> Your free subscription is supported by today's
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