Exterior finishes

The driveway has been poured (though it's under blankets due to the cool weather), the siding is up, and the gabions are installed: almost there!

Entry view: the door is unveiled at last!

Feels good as an architect to see the building appearing as drawn and imagined. This goes to show how important a good drawing is. And while that's important for the visible design, thorough documentation is even more critical when it comes to airtightness and thermal-bridge-free detailing. 

That plug for our profession out of the way, I'd like to say a few things about the exterior design and finishes.  Having served on Oak Park's Historic Preservation Commission for 5 years, I became more sensitive to the massing, roof overhangs, and window-to-wall ratios typical of late 19thc./early 20thc. architecture: before the time of clean and powerful air conditioning and heating.  Studying Passive Houses, it became apparent that a similar principle was at work: the shape, orientation, and number/placement of windows powerfully affect the energy balance of a building.  This doesn't mean that Passive Houses need to look "traditional", but they do share a continuity of design thought with traditional buildings.  I like that. 

The mass of this house was intended to have a traditional compact rectangular form and gabled roof; siding detailing of the thick walls offered design opportunities. First, we provided overhangs for the old-fashioned reason: they really do protect walls and windows.  On the walls we also provided intermediate trims with drip flashings to get water away from the wall and windows.  We chose LP SmartSide as the siding finish.  Like other siding products (fiber cement), it has a really long finish warranty (LP offers a 50 year transferable warranty!). But unlike fiber cement, it is much stronger, lighter, and impact resistant, and it is made entirely of wood (SFI certified fast-growing lumber specifically for OSB and siding).  Since they pulp the lumber, they use the entire tree, and do not add formaldehyde in the manufacturing process.  SmartSide comes in smooth and rough finishes, so we took the opportunity to break down the mass and create interest by contrasting alternating bands.  The exposures are 11" (rough) and 5" (smooth), which repeat the 16" coursing of the ICF blocks inside the walls. 

The basement windows needed areaways with retaining walls.  Traditionally these are of concrete, but realizing we had a lot of brick left over from the previous house, we decided to use the brick to fill wire baskets (gabions) which could operate as retaining walls merely by virtue of their mass: a simple recycling move that saved money and embodied energy. 

South basement window

Another thing about the gabions: they're a lot nicer to look at from the inside that concrete:

Front basement bedroom window

Dig Right In, eco-landscape firm out of Brookfield, is contracted to provide the landscape design and installation, which is scheduled in the next week or two. 

Pictures, Sept. 26

Here are some updated pictures I took for my presentation at the Passive House Conference last weekend in Denver.  More soon!

front--brick just installed

living/dining space looking east to stair

from stair to west (back of house)

exterior rear of house

You may be wondering why the drywall is blue--it's a new product from Certainteed that captures and sequesters aldehydes and VOCs, so it will contribute even more to the healthy interior.

Most of the Passive House-specific items are installed, and the next few months will focus on finishes and fixtures.  Stay tuned!

Blower door did not suck

There are too many bad jokes to be made about blower doors...I couldn't resist.

This is just a very quick post to announce the our PHIUS+ rater, Andy Scott of Energistics, came to the site this week and performed the preliminary blower door test.  As soon as we turned the fan on we started smelling sewer gas (plumbing is just at rough, so no traps installed.  So we plugged them with rags and fiberglass (not exactly airtight, but kept the stink down and gave us a more accurate reading.  Andy didn't have a "C ring" to be able to get below 300cfm, so Brandon got one from his truck...

...here he is wearing it like a hat...

...and we got the reading: 240cfm, which translates to about 0.38ACH50, well below the 0.6 Passive House threshold, and we will be able to tighten a bit more with the plumbing.  A big congratulations are in order for Brandon and Eric for sealing the windows and doors so well...

tiny crack at the miter--but needs to be there to allow glass to be replaced

great seals on the doors and windows

...as well as the few penetrations through the ceiling.

gaskets were perfect

I'll say it again: this is a great team!

Heating and cooling the Passive House

One of the main qualities of a Passive House building is that the mechanical loads are so reduced that you only need a tiny system for heating and cooling.  Even for this relatively big house, there is no conventional furnace/AC small enough that it wouldn't be way oversized, and therefore short-cycle.

Our heating and cooling is handled with the new stars on the efficiency stage, mini-split (or ductless) heat pumps.  This is a rapidly expanding field that bears little resemblance to the heat pumps of the 1970's and '80's.  Heat pumps exchange heat similarly to the way air conditioners or refrigerators do, but can work in both directions to provide both heating and cooling.  The early units got a bad rap in the 80's for being inefficient at supplying heat below 30F or so, but the new Mitsubishi units we're using supply their full nominal heating output at 5F and continue to operate efficiently down to -13F.  With a SEER rating of 26  and heating Coefficient of Performance over 3, the ductless heat pump is a terrific unit. But they gain even more efficiency from the fact that they can modulate down to run at partial load--so they will run on a very low setting if you just need a little heating or cooling, which is way more efficient than coming on, blowing hard, and shutting off. Another benefit in cooling mode is that the unit can dehumidify continuously, even at low levels of output.  Aside from being a more comfortable way to get your space conditioning, it is also nearly silent.  You literally can't hear these units unless you get your ear right up on top of them.

They have an outdoor unit that looks like a small, upright A/C condenser, and a wall unit with a fan that provides conditioning.  Here's the rough installation of the units:

Master Bedroom

Living Room

Mitsubishi and others also have units that can be ducted, but we didn't want (or need) to get into that.  One of the other qualities of the superinsulated Passive House is that, since the walls lose heat so slowly, you just don't need to duct heat around to provide even temperature in the house.  The ventilation system helps the air circulate, and convection and vapor pressure migration take care of the rest.  Super comfort, Passive style.

Ventilation for the Passive House

One of the qualities of a Passive House is that the construction is nearly airtight., so to allow the house to "breathe" we use an energy-recovery-ventilator (or heat-recovery ventilator).  Yes, houses need to "breathe", or more accurately, people inside houses need fresh air, but the problems with leaky construction are at least threefold: 1.) you don't know if the leaks are getting fresh air where you need it (like in the bedrooms), 2.) as it leaks in, the air picks up contaminants and can cause condensation, mold, and deterioration of the structure; and 3.) you don't know the rate of "leaking", so combustion gases, moisture, etc. may not be getting cleared out of your house.  My analogy is that we want the beast to breathe through its nostrils, not through gaps in its skin.

Like all Passive Houses, ours has a balanced ventilation system (same amount of supply and exhaust) that runs continuously. It has an extremely efficient fan, and recaptures about 85% of the outgoing heat, so it is a low-energy way of providing great indoor quality.  The system extracts air from the kitchen, bathrooms, laundry, basically any place that makes moisture and odors, and supplies fresh air to bedrooms and other living spaces.  Imagine getting fresh air continuously as you sleep...you wake more refreshed, having been breathing air that was cleaned of pollen and molds by the (MERV 7/8) filter. 

Zehnder, beginning of installation

Our system is a Zehnder ComfoAir 550. Zehnder not only has great heat recovery technology, but they have also developed a suite of products that make sizing, installation, and commissioning (getting air flow right) a breeze.  The small flexible ducts clip into supply and exhaust manifolds, and into supply and return diffusers, which have fittings to adjust flow rates.

Zehnder with ductwork connected to supply and exhaust manifolds

 These ducts are flexible and fit in a standard 2x4 cavity, so are quite easy to work into the construction site (though I recommend a riser for ducts running from the manifolds to another floor).  One reason each diffuser is individually ducted is that precise airflow can be guaranteed at each location. Commissioning consists of testing each diffuser at the end of installation and adjusting the unit's fans and the diffusers themselves to ensure design flow rates.  Once set, it typically doesn't take maintenance to maintain the flow rates; all that needs to be done is occasional cleaning of the filters.  Clean, fresh, healthy air, 24/7.

Passive House window installation in ICF

We learned a lot about windows...hence this post to pass it on.
First, we priced a number of European windows that would work for our demands: we needed glass at about U=.09, frames at about U=.15, solar heat gain coefficient of .5, and insulating spacers.  We learned that the UPVC windows (Intus, Unilux Isostar, Zola) fit the bill at the lowest price.  Great prices, actually, as in, competitive with good US wood/clad windows (I recently heard around $34/s.f. for UPVC units).  Our clients preferred aluminum clad wood, though, and we wound up choosing Zola's Thermo line. Their performance was great, and their price beat the competition easily. They're made in Poland with German Roto hardware. Florian Speier, the architect who founded Zola, helped develop the THERM protocol for determining installation thermal bridge values, so he's a good resource to the Passive House Consultant as well. By the way, I'm not going to name "the competition" here, because the pricing we got might not be indicative of where their products stand today, or with other project specifics, and I don't want to prejudice anyone unfairly.

A few logistical items to note:
- Shipping from Europe didn't allow for an exact delivery date: plan for flexibility.
- The shipping container was packed excellently for safe travel of the windows, but not for jobsite storage (the windows weren't individually crated).

Inside the crate

- You typically have to pay to hold a shipping container on site, so either unload the windows to a safe location (for us not easy on the small job site) or install them right away.
- These are beautiful, finished, furniture-like pieces of equipment, so they need protection for the duration of construction.
- Powder-coated Zola screens were expensive--we're going to have them made locally instead.

For installation we had two options: screw through the jambs into the bucks, or use metal clips that slotted into the jambs.  Since we had solid concrete behind the jambs, and didn't have close enough tolerance on all the shim spaces, we chose to use the clips.

Clip is just below green tape, which is covering buck anchor

That meant we had another blip to deal with in our airtight layer, but by this time we were so Siga-happy we didn't worry about it.  As you can see, we used the Siga Corvum to tape the jamb to the buck (Corvum is pre-folded with two peel-away strips on the back, made for corner air sealing), and the Wigluv to cover the clip-blips.

Air sealed window. Note: interior overinsulation will cover tape.

Initially we were concerned about the airtightness strategy at the windows, but having done it, it's actually pretty easy and entirely visible and accessible, making it easy to fix if there are any weak points.

The weathertightness on the outside was handled with more traditional flexible flashing. Here's Brandon Weiss, the GC, explaining how that was done:

 And here's an exterior view, with a window awaiting the overinsulation on which to tape off the flexible sill flashing:

Exterior: west family room window

Man, I should offer CEU credits for this blog post!  Hope it's helpful to those out there detailing.  Your comments are welcome...this is a learning experience for us.

Interior renderings

Here is some eye candy. It's fun to think of these while standing in the house now (with 10 tradesmen working hard all around).  You'll see a number of light coves--we're using T5 fluorescent strip lights, which are extremely efficient; plus the indirect uplight effect is very nice.  The stairs, paneling, cabinetry, and stained trim is birch. The light fixtures in the dining and kitchen are going to change--we put in simple George Nelson fixtures for a start, but will likely do something more decorative over the dining table.

Living room looking east to dining and stair, kitchen at left

From dining looking northwest toward kitchen

The stair!

Master bath

The bath sconces are George Kovacs fixtures, clean and inexpensive (Lumens.com). We wound up changing the light over the tub to a 4" recessed (for code/moisture reasons) but generally are avoiding recessed lights to leave room for ventilation ducts and avoid the more expensive 4" cans.  We have about 6" between the finish ceiling and the plywood airtight layer, so conventional cans are not an option.

I promise, the window post will be next!