Systems for new PH in Palo Alto - for comment

[Danjoh99]

I know PH retrofits are our priority, but I'm involved in a new
construction PH in Palo Alto now. The project has a tiny budget.
These are the systems we're considering:

1. Envelope. 2x6 OVE framing, possibly panelized and fabricated with
sheathing and cavity insulation offsite (like E-colab's Fairview
house? http://picasaweb.google.com/passivehouses.us/Fairview2House#).
Sheathing layer is the air barrier. No plumbing or electrical in
exterior walls (located instead in furred inner layer; put required
electrical outlets in slab?). Full cavity cellulose insulation.
Exterior XPS rigid insulation if necessary to control R-values and
thermal bridging.

2. Hot water. Solar hot water with Phoenix condensing gas water
heater.

3. Space heat. Several radiators or hydronic baseboards pulling heat
from the water heater. Would rather do a single zone of radiant slab,
say the kitchen-dining-living room, but which is cheaper?

4. Ventilation. Exhaust-only using bath fans and kitchen hood.
Makeup air using trickle vents into principal rooms (behind radiators,
or behind refrigerator, for example). We'd like to make it work
without using an ERV or central ducting (to save money). The heat
loss penalty we face without the ERV is 75 CFM outside air (per 2008
Energy Code) at, say, 30 degF peak load = 3240 BTU/hr. Double this
for periods of boosted exhaust from bathrooms. Also add about 20W
continuous electricity for the exhaust fans during heating hours when
the windows are closed.

5. Ground interface. Slab on grade with ICF (insulated concrete form)
perimeter footing. Slab has rigid insulation underneath and is done
in two pours. Rough pour over insulation, then finish pour toward the
end of construction.

Thanks for any comments. --Dan

[Graham Irwin]

Dan,

I am not sure that retrofits are THE priority (they are a priority).
Studies suggest that much of the built environment is yet to exist: http://www.citymayors.com/development/built_environment_usa.html
In the West, it may up to 80% of the 2030 built environment created
since 2000. Perhaps not in the Bay Area, but in the state. Anyhow, new
construction is relatively easy to get to PH, so it is really an
opportunity lost if not done there.

1) Ecolab build built the Fairview with TJI joists as studs in the
walls to eliminate thermal bridging and provide the necessary depth
for their required insulation. This required two layers of sheathing
(OSB inside, fiberboard outside.) On another PHIUS project in a heavy
wind zone I got to see Simpson hardware (which was much more familiar)
holding down an interior 2x4 framing structure upon which these TJI
"sandwiches" were hung. It was amusing to all there that the interior
structure is what comprises most of our buildings!!! The XPS foam is a
major enhancement to the U value of a 2x6 cellulose wall, you can make
a building work without it in good circumstances, and one work WITH it
in bad circumstances. I am interested in exploring the substitution of
plywood/OSB for foam sheathing, with shear collected in strongwalls,
braces, etc. In many cases, much of the shear which the plywood/OSB
sheathing supplies is not necessary when a building is analyzed.
Ecolab had concerns about cellulose settling as the panels were
shipped to the site for Fairfview II and went with blanketed, blown in
fiberglass. Fairview I was built on site, no factory panelization. I
am finding that in many cases, the cooling load is a bigger concern
than the heating load, but that is determined with PHPP.

2) Good water heater, but expensive. It may be possible if the project
is including PV that the backup heating required for solar isn't a
whole lot, you can also use an air to air hot water heater to cut the
backup heating load in half at least.

3) The financial theory behind PH is that you don't need additional
space heating beyond a hydronic coil in the ventilator ducting. If the
peak heating load is below 10 W/m2, you can do this, and should try
because that's the efficiency payback. Cooling through the ventilator
ducting is about 8 W/m2 max, but I have seen mini-splits used
(Fairview) for cooling. Generally doesn't take much if it is required.

4) I think you'll lose the game with the ventilation plan you suggest.
Not only will you require mechanical ventilation with a house that
even approaches PH airtightness for IAQ, it will be required come
August 1 of this year. Further, your trickle vents will destroy the
air tightness of the shell, and that will raise your heating and
cooling loads DRAMATICALLY and you will never meet PH standard of 0.6
ACH50 (this is the biggest challenge we face here, IMHO). You are
really wasting time and effort with the airsealing and insulating of
the shell if you're going to cut holes in it. The ERV not only
provides high quality comfortable fresh air and is the key to the cost
benefit of PH, the Ultimateair comes with a night cooling feature
(like an economizer) which is a REALLY nice feature in our summers of
cool nights and hot days. The space heating system you propose will
probably cost as much or more than the ERV...

5) Work on trying to eliminate thermal bridges as much as possible -
hard at the foundation in earthquake/termite land.

I am happy to offer additional advice, should you not already regret
asking me! ;-)

Good luck,
Graham Irwin
AIBD, CPBD, CGBP
Remodel Guidance
415-258-4501

Residential Design • Plans & Permits • Green Building • Period
Homes

[George J. Nesbitt]

Evaluating the project in the PHPP should guide any choices you
consider, upfront.
Since you have a tiny budget, Keep it Simple.


1. Envelope. exterior structural sheathing, framing & insulation,
interior air barrier (sheetrock), service cavity framing, plumbing &
electrical (no insulation), sheetrock.
Is this a 1 or 2 story structure?
If you use exterior insulation 2x4 framing may be fine, but you need
to be careful in your choice of open or closed cell foam (rigid
rockwool would be a good choice). Placing vapor barriers in walls
either has to be avoided, or placed properly.
Keep the mechanicals out of the slab if at all possible.

2. Phoenix, excelent water heater, but expensive, I will be installing
my first solar phoenix in the coming months. There are less expensive
high efficiency water heaters. Solar Hot water is a great thing, and
depending on stroage and use, with the low heat requirement of a
passive house, you will get a higher percentage of winter
contribution.

3. If you already have a slab, is it that much more to add tubing? But
I would say you don't need it, and considering the low heat need, it's
not a great match, plus radiant slabs don't work well when trying to
use them with direct passive gain. Think integrate with ventilation
system.

4. I agree with Graham on all counts. You need a heat recovery
ventilator, otherwise you are doubling your heat load! A fully ducted
system is need, Lifebreath make a HRV hydronic air handler, as does
Nuair (both canadian). The difficulty is the low heat load. I am still
not sure the best equipment to use to set this up. A minisplit heat
pump with the HRV/ERV is another posibility.

5. Not a big fan of slabs, and very critical that they are fully
insulated. Consider a pier and gradebeam foundation. Do you need the
slab to be structural? I have seen a structural slab with insulation
above, and than a top slab. Its not the sand that's the problem, it's
where you place the vapor barrier.

Without seeing the actual project, consulting, and running the PHPP,
we can only still talk about things in a general way based on
principles.

On Jan 9, 2:27 pm, Danjoh99 <danjo...@gmail.com> wrote:
> I know PH retrofits are our priority, but I'm involved in a new
> construction PH in Palo Alto now.  The project has a tiny budget.
> These are the systems we're considering:
>
> 1. Envelope. 2x6 OVE framing, possibly panelized and fabricated with
> sheathing and cavity insulation offsite (like E-colab's Fairview

> house?http://picasaweb.google.com/passivehouses.us/Fairview2House#).

[Dan Johnson]

Response to Babette, who wrote:
====
Dan,
Could you describe how the house will be used?
Who are the occupants?
How much are they occupying the house? home office?
Purpose of the renovation? and size?
Goals for the energy measures
Budget?
Thanks, Babette
I think it helps to understand a context...
====
Ahh, an architect is in the group! This new house in Palo Alto is for
a husband and wife with two small children. It's new construction,
about 2200 s.f., two stories, in place of a 1920 house that will be
torn down. Construction budget is $750k. They are both busy
professionals, but they envision a home surrounded by fruit trees and
chickens with their laundry hanging in the breeze. They'll occupy the
house as a family (including an elder in-law suite) as the kids grow
up until they go off to college in 15 years, including an office
niche, but not a full home office. The house is to be net-zero-site
energy, and meet the PassivHaus standard. Building by PH principles
may be the only way we can achieve net zero energy on the small
budget. It's a challenging project in every aspect.

I hope that helps for context. --Dan

[George J. Nesbitt]

Thanks for the context, but what about the site it self? Shaded, large or small, trees, surrounding buildings, topography, etc......

And what about that great old 1920's house?