is it working?

after more than 2 years living in skidmore passivhaus, i’m frequently asked is it working?  let’s take a look at the numbers from the last year:

it’s interesting to compare our actual annual consumption to the predicted consumption per the PHPP model.  this project was modeled in PHPP 2007, and there has been some criticism in the passive house community suggesting that the German default values for electrical consumption built into PHPP are far too low for the US culture.  (PHIUS has gone so far as to radically change the default values for electrical consumption).  given the data on our project, i’m not so sure there is a problem.

occupant behavior of course plays a significant role in energy consumption, and there are a number of conditions to note for this building.  PHPP assumes 4 occupants for a house of this size, when in reality there are only 2 of us (plus 1 dog and 2 cats) which should result in lower overall energy consumption.  with fewer occupants, there will be lower internal gains which presumably would increase slightly the heating demand and heat load.  Because we both work from home much of the week with computers and other devices running all day, it could be assumed that while there are only 2 of us, our consumption includes both home and work and would therefore be higher.  I also should note (somewhat sheepishly) that we have 3 cables boxes that stay on all the time, including one DVR, which draw a steady amount of electricity and generate some heat.  This is all somewhat anecdotal, but it shows the inherent complexity in accurately predicting energy consumption.

an annual summary of our site electricity consumption and site energy production (from our roof mounted 4.32 kW array) shows that we generated 82% of the electricity we consumed.

an annual summary of our site energy consumption (gas and electric) and site energy production shows that we generated 49% of the total energy we consumed.

a monthly summary of our site energy consumption (gas and electric) and site energy production (from our roof mounted 4.32 kW array) shows the large deficit during the winter months as expected.  more efficient equipment for our space heat and hot water would certainly help to offset some of this deficit.  while a larger PV array would get us closer to net zero on an annual basis, it wouldn’t solve this deficit and demonstrates one of the problems with an approach that focuses solely on annual net zero energy.  elrond burrell has written an excellent blog post covering this topic.

a monthly summary of our annual gas and electric bills demonstrates our consistently low monthly utility costs.  our average monthly cost for both gas and electricity over the last year was $36.53.

note that for most of the year we pay our electricity provider the minimum monthly charge even though we are generating more electricity than we are using.  our only gas appliance is our hot water heater, and a significant portion of our small monthly gas bill is for fees and taxes regardless of our consumption.  if we were to change our gas water heater to electric even without a change in energy consumption, our monthly utility cost would be even lower by eliminating the minimum gas charges.

aside from reducing our CO2 emissions and our consistently tiny utility bills, we’re staying extremely comfortable year round – warm in the winter while barely using our heating system, and cool in the summer without any air conditioning.  so the answer is unequivocally yes, it is definitely working.

 

 

form factor and passivhaus

It is well known that compactness is an important aspect of a well designed and cost effective Passivhaus as it has a considerable impact on the overall heat demand.  Having now modeled a number of projects in PHPP (Passive House Planning Package), I decided to do a quick comparison of the ratio of envelope to floor area (known as the form factor) as well as the average R-value of the entire envelope.  Here are a few examples:

Emerson

envelope to treated floor area:  3.8

average R-value:  39.4

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Skidmore

envelope to treated floor area:  3.7

average R-value:  29.7

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18th Ave Residence

envelope to treated floor area: 3.2

average R-value:  24.1

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Haig Haus

envelope to treated floor area:  2.7

average R-value:  25.9

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Ankeny Apts

envelope to treated floor area:  1.5

average R-value:  19.7

 

While there are many variables at play that make each project distinct, it is clear that form factor has a huge impact.  Remember boxy can be beautiful!

 

 

help wanted

In Situ Architecture is looking for some part-time contract help. Excellent rendering and graphics skills a must.  Interest in low energy building and passivhaus is helpful.  If you are interested please email a brief description of yourself with a few examples of your best work.

Info at insituarchitecture dot net

.32ach

we recently performed our final air-tightness test at skidmore passivhaus with a result of .32ach at 50pa.

we are extremely pleased that our clear air-barrier strategy and diligent execution paid off.

here’s a snapshot of our final phpp #’s:

there is no doubt that achieving passive house, particularly in our climate, is fairly easily achievable.  it does require smart design, careful planning, a contractor that understands and pays attention, and a healthy dose of persistence.  if you are ready to build one for yourself, drop us a line at info@insituarchitecture.net.

more pictures and info coming soon.

council crest update

from yesterday:

exterior and interior progress continues.

architecture by bohlin cywinski jackson

construction by don tankersley construction

notes on placing an exposed slab on grade

Here are some quick notes on our Exposed Slab on Grade (placed on top of continuous 15mil vapor retarder and 4″ of eps insulation):

Placing concrete on a continuous vapor retarder definitely ups the degree of difficulty when it comes to finishing and curing the slab.  Water in the slab can only move out the top, meaning the slab can dry unevenly, crack, and even curl.  To compensate we are trying a wet “flood” cure.

We decided to use fiber mesh reinforcing and eliminate the steel reinforcing altogether from slab.  Apparently the fiber can make finishing trickier, but it typically results in strong slab with less cracking and for a bit less cost.

The type and location of joints is always a question – we even considered for awhile not using them and letting the slab crack more randomly (it will crack).  In the end we decided to use a tooled joint (in this case made with a custom tool from another project) and to place them strategically under walls so they are barely visible.  Tooled joints can be made almost immediately before cracking can happen whereas sawcuts have to wait until slab is firm enough to handle the saw, and potentially after random cracks have already occurred.  Saw cuts also have a risk of spalling, but when they are executed properly they certainly look best.

After knocking around options for curing the slab, we decided to go old school and use a wet flood method.  The idea is to cure the slab slowly and evenly by keeping it wet and cool, allowing it to gain as much strength as possible before subjecting it to the stresses that occur when it dries out.  The slab edge formwork was already above the top of the slab, so it was relatively easy to keep the slab underwater.  It uses a fair amount of water as there are minor breaches in the perimeter formwork dam, but it eliminates the use of expensive chemical curing compounds.

So far we have kept the slab wet for 5 days (flooded most of the time) and we’re still babysitting it.  It’s time to get set up for the last small concrete pour (a plinth for the stair which doubles as a landing), so the wet curing will come to an end. Only time will tell what the result will be, and we’ll never know if our methods were better or worse.

breaking ground on skidmore (passive) house

After many many months (years really) of scheming and planning, we finally broke ground on our new house.  A lot has happened since our last look at the project in passivhaus progression.  It took us a bit of time to get our house ready for sale, but we eventually sold it, found a great house to rent complete with chickens, moved, and are getting settled in our temporary digs.

First up was getting our delinquent and non-responsive tenant out of the house.  We got our first (and hopefully last) taste of the eviction process.  A few checks and a couple of weeks later we took possession and had a close up look at the sorry state of the house.  Next we removed some of the existing trees.  A few were unhealthy, a few were in or too close to the footprint, and a couple were creating massive shade.  While we struggled with this decision and upset at least one neighbor, in the end we decided it was best in the long run to remove the largest Oak in the backyard.  It was sad to see it come down but the lot has been transformed back into a sunny paradise and we hope over the next decade to develop a well designed and much more beautiful landscape.

While the first bank we approached about construction financing had favorable rates and seemed easy to work with, the process quickly turned sour as they began to question first the green roof, then the single ply membrane, separate structures, and finally the lack of a garage.  In the end it became apparent that they didn’t get it and it was time to try another route.  At the same time, we decided that the separate structures created some domestic challenges in addition to lowering the value of the property in the eyes of the bank, so we quickly redesigned the house to incorporate the space between the buildings as interior living space.  Although it adds more square footage and cost, it does make for a better surface to floor area ratio and had a favorable impact on our PHPP calculations.  We then approached a local bank with our revised design complete with green roof, no garage, and modern aesthetic, and it was basically smooth sailing right up to the loan closing.  Aside from their annoying tagline, so far I have nothing but good things to say about my experience with my local bank.

The permit process went a little more smoothly.  After responding to a simple structural checksheet, answering some questions from the plans examiner about the Passive House specific details, filing a required Operations and Maintenance agreement for the ecoroof with the County, and smoothing out some internal confusion at the city about an existing cesspool tank and drywell, we got our new building permit as well as demolition permits for the existing house and garage.  Next up was testing for Asbestos; the demolition contractor was required to have paperwork certifying that the debris was free from Asbestos.  Somewhat to my surprise, Asbestos was found in a number of unusual places including window glazing, caulking at the roof penetrations, and drywall compound.  Another check and about a week later the Asbestos was abated and demolition could finally begin.

Here’s a quick progression of what’s happened over the last 2 months:

Trees are cut and asbestos abatement in progress.

House and garage are gone!

Old tanks are decommissioned and building area is stripped.

Building pad is prepped with compacted gravel.

Footings are formed, EPS placed and moisture barrier taped.

Concrete is placed in footings.

Gravel backfill is placed and compacted underslab.

Underslab EPS insulation is getting set on sand bed.

Now that we’ve started, there’s much to talk about.  Some possible ideas:

– A better way to build an insulated slab on grade?

– PHPP calculations and optimization of systems

– PH certification:  PHIUS+ vs PHA

– Passive House Windows

There are many people to thank for their help (directly and indirectly) in getting us to this point.  Here are just a few:

– Aaron and Mike at Brute Force Collective

– Dan Whitmore at Blackbird Builders

– Florian at Zola European Windows

– Don Tankersley Construction

– John Russell (Concrete) Construction

– Matt at Zehnder

– Skylar at Hammer and Hand

– Ryan at Earth Advantage

All for now.  Check back soon.

Jeff

www.insituarchitecture.net

forest lane residence

we recently whipped up a design proposal for a new residence in the northwest hills of portland.  we had a great time with it but unfortunately it looks like this one will be staying on the shelf.  let us know if you want to take it for a spin.

www.insituarchitecture.net

testing

last week i successfully passed part 1 of the Certified Passive House Consultant exam, and in the next few weeks i’ll be wrapping up the take home design portion. with a little luck in the new year i will be a Certified Passive House Consultant!

process of (de)construction

over the past year, i’ve had the pleasure of teaming up with one of portland’s finest residential contractors, don tankersley construction.  although i’m working outside of my usual role as architect/designer, this has been an equally challenging and rewarding experience and one that will certainly inform my own architectural work.  one of our most recent projects to start is an extensive remodel of a residence located in the southwest hills of portland.  the remodel has been designed by bohlin cywinski jackson architecture of seattle.

check back frequently for updates as construction progresses.