Wednesday, June 29, 2011

Drywalling, Sheetrocking, and Mudding, Oh My.

Our next building phase is the drywall. The drywall creates an interior finishing surface. The drywall creates an additional air barrier, but actually, drywall is both somewhat breathable and vapor permeable.

This video compilation captures the first steps of the drywalling, also known as sheetrocking. "Sheetrock" is actually the trademarked name for the drywall product made by US Gypsum Corp. The word for  trademarked terms that popularly come to take on the generic meaning of the product category that they represent  is "antonomasia" or "synecdoche" (eg.  Kleenex, Xerox, Google, Band-Aid).

Now that they dry walling is complete, we've starting taping and mudding the drywall to create a smooth paint-ready surface.

Saturday, June 18, 2011

ADU Building System Science and Building Program Design Overview

This long and somewhat technical post is intended for those who are interested in building an ADU themselves, or who are interested in building science. There's a 13-minute audio/visual presentation at the end of this post that covers some of the same information in presentation format. 

Building Overview
  • The goal for this project is to design and build personal housing that is financially sustainable. 
  • Projected cost for the design, permit, and construction is $92K, which equals $115/sq ft. 
  • 799 sq ft and its location is very walkable and bikeable.
  • Northwest Energy Star certified through Earth Advantage Institute with a EPS score of <40.
  • Notable design features: staggered stud wall construction, slab-on-grade,  92% efficient tankless water heater for radiant floor and potable water system, heat recovery ventilator, passive solar orientation; space efficient design accented by acid-stained concrete floors, exposed beams, and accent lighting.
Residential Sustainably – Living Small at No Cost

My concept of sustainability includes a financial component. I have explored a variety of low-cost, creative living ideas, and eventually decided on the idea of building an Accessory Dwelling Unit on a single family lot with a pre-existing primary residence. In this model, my financial goal was that the pre-existing house on the lot would pay for itself through rental income. Upon completion, I could live in ADU without paying the monthly mortgage on the main house. With this idea in mind, I purchased a single family home in 2010 with the intention of building an ADU on the property.

Conservatively assuming that the ADU would generate a $1K/month in rental income (if I were not living in it), a $100K investment roughly translates to an 8.3 year investment payback period, with an annual return of 12K after that payback period. Here are some variables that could alter this payback period:

    *         the construction could cost more or less than anticipated (+/- 15%)
    *         the rental income may be more or less than the mortgage payment (+/- 20%)
    *         there could be unforeseen maintenance costs on the primary house

I will not make much profit from the monthly rental income from the primary residence. However, I am confident that the investment will allow me to live at little to no cost for housing after this investment. Additionally, I am confident that the investment will eventually pay for itself and generate surplus income. This accomplishes the initial financial benchmark that I was seeking to achieve for this project.

Accessing tens or hundreds of thousands of dollars is the biggest barrier for those who are seeking to design and build an ADU. If one can surmount that significant financial hurdle, ADU's have a lot of potential payback.

Selecting a House with an Appropriate ADU Site
A critical factor in purchasing a house was the viability for the lot to gracefully host an ADU. The neighborhood was obviously important for many reasons, but so was the micro-neighborhood, and of course, the property and house itself was an important factor. When I found the property in NE Portland, it seemed well suited to the ADU design goals in these three categories.

Neighborhood Livability: The address scores a 71 on, but that doesn’t reflect how very walkable and transit oriented the neighborhood feels; house addresses 5 blocks away in either direction score 8 points higher. From an energy perspective, this urban location allows residents to easily reduce travel related emissions significantly for work downtown, as well as from running regular errands.

Micro-Neighborhood: The micro-neighborhood has a range of architectural styles—the next door neighbor lives in a yurt, and another home is sided with corrugated aluminum. Due to the wide range of architectural styles adjacent to this yard, the ADU is well-suited to this pocket of Portland. The homes in the immediate vicinity are oriented towards the street front side of their lots- in our 50’ x 100’ and 50’ x 50‘ lots, the yards are grouped together.

Property:  My primary house facade is only 11ft from the front sidewalk, leaving me with ample depth in the rear yard for a new 27’ length structure. I visited approximately 60 properties in NE Portland before finding this one. Overall, this house and the land purchase was competitive in terms of its current value, and even more valuable in light of its potential future use as a home with great ADU.

Site Selection: The ADU will sit on the north side of the lot. There is a gorgeous 60’ Cherry tree canopy on the south side of the lot, shading the ADU throughout the summer, and allowing light to pass through during the winter months. The extensive canopy provides a wonderful viewshed from the south-facing windows, so the majority of the glazing is oriented South. The ADU will have short eaves to match the trim on the primary house in accordance with Portland’s ADU regulations. In mid-summer, when the sun is above the canopy at noon, the short eaves will cast just enough shadow to block direct exposure through the clerestory windows. Most of the windows will receive dappled sunlight; the canopy will block direct sunlight 80% of the day.

The Building Envelope

The building envelope design goal is to achieve a high performance shell at a low cost. Rather than attempting to achieve Net-zero or LEED or Earth Advantage certifications, which require allocating funds towards particular materials, products, or renewable energy such as solar panels, I am investing proportionally more money into air sealing and insulating the building shell than in other facets of the building design. We’re using best practices for air sealing, adding redundant air barrier systems that are somewhat vapor permeable. Blown-in fiberglass is the insulation type for the 8 ¾” wall and 10 ¾” ceiling cavity.

Wall Assembly (from exterior to interior)
  •     Cedar siding shingles- a naturally water repellant composition.
  •     Rain screen from strips of dimple board, through which the shingles will be nailed.
  •     Weather Protective Barrier- Siga Majvest weather protective wrap and Siga Wigluv tape for the plywood sheathing joints. The Siga wrap and tape are also vapor permeable.
  •     5/8” Plywood sheathing to which the shingles will be nailed.
  •    Staggered studs framing. Selected because it provides a 8 ¾” insulation cavity and has less thermal bridging.
  •     Loose fill blown in fiberglass- R33
  •     Drywall
  •     Paint
Roof, Slab, and Glazing: The roof assembly will be R44 and the slab on grade floor will be R-15. The slab is thermally broken from the foundation walls (using 1” EPS foam) and the gravel (using 3” XPS foam). The windows and French door will be vinyl, with a U-value of 0.30 to comply with Energy Star standards.

Heat Loss Calculation: Earth Advantage conducted an energy use calculation using a RemRate analysis and found that the ADU will use 39.6 Million BTU/year. Based on an assumed performance of 6.5 air changes per hour @ 50 pascals, the Energy Performance Score (EPS) will be 40 (EPS is a simple numeric score that correlates with the Million BTU/year for a given home. The average new Oregon home has an EPS score is 89, so the ADU will use less than half that amount of energy. The ADU will likely beat that 6.5 ACH air sealing benchmark, which will in turn lower the EPS score by several points.

For the heat loss calculation, I assumed that 83% of the wall assembly will be R-33, 17% will be R-6 due to thermal bridging at the corners, door and window jams. The ADU will have 0.15 air ACH under ambient conditions. Because the ADU does not have ducts and will have a heat recovery ventilator (HRV) to balance pressure and moisture, there will be very little air pressure differential to drive air loss through leaks. The HRV will provide 60 cubic feet per minute of fresh air and capture 65% of the heat energy from the air vented.

Since the ADU is going to have tankless water system to heat potable water due to space constraints, we have overlaid that function with providing hot water for the radiant floor system using a heat exchange. We will be using the Navien condensing tankless combination water heater, which is 92% efficient natural gas water heater.

The heater will be situated inside the thermal envelope to eliminate any heat loss leak potential. There will be three radiant zones: one in the concrete slab on the first floor, one in the bedroom in a vacated air space under wood flooring, and one zone in the upstairs bathroom. 

I had notions of using mostly salvaged construction materials as a mechanism to reduce upstream waste and reduce costs, however this proved to be impractical. While it may have saved some money, it would have taken too much time to find used lumber and other building products. And, I’ve learned that many constructional materials must be new, such as the foam, concrete, nails etc. As a rough guess, pound for pound, this project will be 95% new materials, 5% used. This ratio is disappointing to me, as I would have loved to reuse materials to a greater extent. However, many of the finish materials and fixtures will be salvaged: flooring, railings, sink, tub, doors, and possibly other finish materials such as paints. 

The building mechanics are designed to be relatively simple. The mechanical systems are limited to the water heater, heat recovery ventilator, and the appliances. The new appliances will all be Energy Star certified and several of them will be eligible for substantial rebates from the Oregon Department of Energy. 

Indoor Air Quality

There will not be much ductwork in this ADU except for a couple short duct runs associated with the HRV. The HRV will vent the bathroom, and the gas stove will be direct vented. The HRV will bring in a constant supply of fresh air based on a weekly cycle. Additionally, the open, lofted floor plan will allow me to leverage the stack effect and winds to air condition the ADU through operable windows on East and West sides of the structure. All of the floor and wall surfaces in the house will be hard; there will no carpets to collect dust. We’re using a high-quality weather resistant barrier in additional to cedar shingles, so I don’t anticipate any moldy conditions in the walls.

Quality Control

The ADU will get Energy Star certification through Earth Advantage to help ensure that the builder is using the best available framing, sealing, and insulation practices. The builder must build to Energy Star standards and is contractually obligated to use the ‘Thermal Bypass Checklist’ and relevant ‘Critical Details’ and ‘Tech Tips’ from the Northwest Energy Star website. To help ensure good water protection and air sealing quality, we are using SIGA Majvest weather resistive barrier and Wigluv sheathing tape. We are getting technical drop-in visits from the Energy Trust subcontractor outreach specialist. Earth Advantage will be conducting a blower-door test to check the air pressure and to help identify any sealing gaps.


This ADU project is an attempt to design and build a small, beautiful structure, and develop a zero-cost residential financial model. So far, it has been very successful. The ADU is under construction now and it is looking wonderful. The costs have increased from my initial goal of $100/sq ft to $115/sq ft, but this is still a relatively low cost for the product and building performance that I am expecting to achieve.

My parallel goal for this project is to document and write about the design build process with a strong focus on ADUs, and the nuances associated with their development. This project has sparked a new passion for me, blending my interests of green building, environmental and urban planning, and policy. I hope to use my personal building experience, and green building background, and governmental experience to help other individuals and communities who are seeking to build ADUs, and to help others design better, tighter, and greener.

Here's a slide presentation that covers some of this same information.

Thursday, June 16, 2011

Air Sealing and Insulation - The Week of Weatherization

This week has been all about air sealing and insulation.

In my previous post, I wrote about air sealing and insulating the main house--a drafty and uninsulated house, built in 1906. In the weatherization project, that house wall assembly's R-value increased from R-1 to R-12-- a huge improvement that will dramatically effect the comfort of the house, and decrease the energy bills.

This post is about air sealing and insulating the ADU. It was far easier and cheaper to air seal and insulate the new ADU construction than to weatherization retrofit the 1906 construction. In contrast to the retrofitted R-12 walls, the ADU's walls are now R-33. After much consideration, I decided to use Certainteed blown-in fiberglass insulation. This cost $2,700 for about 1400 sq ft of wall cavity (9" deep), and 900 ft of ceiling cavity (10"deep).

Blown-In Fiberglass Insulation

For those of you who are new to this, R-value is a measure of the heat resistance of a material assembly. You know how metal or glass feel cold when one side is facing cold air? They feel cold because those materials conduct heat very quickly. Conversely, Styrofoam does not conduct heat well, which is shops sometime use Styrofoam cups to contain the heat of hot liquids. The best kind of insulating building product is called closed cell spray foam, but it is 2-3 times more expensive than blown in insulation. It's also super ugly---to me, it looks like alien puke--just look at the picture of it in my main house basement ceiling and you'll see what I mean. But, it's effective as an air sealer and insulation material and it's en vogue. It's very important to air seal and insulate buildings to reduce their energy demand- and there's a number of ways to accomplish this. 

Closed cell spray foam looks weird, but it does a great job insulating and sealing

Below are three videos that show the air sealing and insulation process that we used. This was a neat process to watch in person--the third video is best one to see the insulation being blown.

Installing cardboard baffles to create a vented roof cavity

Installing netting for insulation

Blowing in insulation in walls and ceiling (aka. BIBs- blown in blanket insulation)

A video of the completed insulation a day later.

Wednesday, June 15, 2011

Oregon Clean Energy Works (Part II)

This week, I went through the Oregon Clean Energy Works (CEWO) program. I've wrote about the Clean Energy Works Oregon program in an earlier post, entitled Only the Worst Need Apply.

In it, I described how the program works. In a nutshell, it's a program that targets older homes in Oregon that are drafty or not well insulated and offers financial perks for homeowners to get their homes energy audited and weatherized. 

I am VERY impressed by the way that this program is funded and run. But, I wanted to reserve judgment on the program overall until I had been through it. Now that I have been through it, I want to give a strong endorsement to the program.

CEWO doles rebates for weatherization work based on how much modeled energy improvement a house undergoes in their program. Since the house had no insulation and leaked like a sieve, making major energy improvements to the house were relatively simple to achieve. The improvements were relatively cheap and resulted in substantial energy reductions. CEWO bases rebates on the level of weatherization improvements, and because my house was so leaky, I'll receive the full CEWO rebates (In the last month, CEWO has lowered the rebate amounts, so the rebates aren't as enticing as they had been.)

My monthly loan repayment for the weatherization work will be $30/month. In my case, since the energy bills are approximately $100/month, my anticipated 30% reduction will amount to $30/month. The loan repayment will be reduced by the same amount that is saved by the energy bills each month. So, essentially, for no upfront cost, my home was weatherized. After the duration of the loan repayment, the loan will be repaid, and the house tenants will benefit from the decreased energy bills forever more. The other advantage to weatherization is comfort; the house already feels less drafty.

For the energy geeks out there, the blower door test after CEWO brought the home's air sealing from 7,731 to 4,476 cubic feet per minute at 50 pascals of air pressure, a reduction in leaks of 3,288 cubic feet per minute, or from 21 ACH to 12.2 ACH at 50 pascals. This is a huge improvement in terms of air sealing. The R-value in the wall assembly went from R-2 to R-11, the roof went from R-15 to R-49, and the basement perimeter rim joist went from R-1 to R-15.

Here's a video of the blower door test:

Sunday, June 12, 2011

Update on ADU Building Progress: Lighting Design and Electrical

Now that the building shell has gone up, the changes made each day are inside the building structure and don't look as significant. Two weeks ago, we did plumbing. This past week, we completed electrical and have started to install the Heat Recovery Ventilator (which I am going to cover in more depth in a future post.) Here is a little information about lighting design and the video below provides a general status update. 

Before beginning the electrical work, I thought through where the lighting should go, and what type of lighting was needed. Here is a diagram of the lighting plan that I put together with my architect and builder for the first floor.

Lighting design should take into account task lighting (eg. under cabinet lighting for cooking), accent lighting (for showcasing pieces of art etc), perimeter lighting (for helping to guide your eyes around a space), and ambient lighting (for general space lighting). Most of the lighting in the ADU is task and accent lighting. I de-emphasized the use of ambient lighting since most the ADU will be completely lit by daylighting during the day, and at night, the more focused task lighting will be better and prettier than ambient lighting. When the house is complete, I'll write a post about the lighting design and show off how it's been designed with the space in mind. 

Lighting plan for first floor

Here's the general update on the various things that are happening in the ADU.

Wednesday, June 8, 2011

Living Compactly

Live in under 400 sq ft./person. Live in a walkable community.

These principles are the ethical drivers that have informed my personal interest in ADUs. Making these two personal lifestyle choices will very likely decrease one's environmental impact significantly (without much concerted effort for the individual to be more 'green' or 'less consumptive').

My conclusions are based on findings that closely correlate personal energy and consumption impacts to residential locational and housing size.What follows in this post are selected infographics and text that help explain these recommendations.

For US residents that generally believe in climate change trends, and therefor understand the importance of reducing individual energy consumption, it is also important to understand that we owe it to the rest of the world to reduce our individual carbon impact. I am suggesting here, that living compactly is the easiest and probably the most substantial way that most of us can reduce our individual carbon, energy, and BTU footprint.

Tons of carbon dioxide emitted per capita in the US and globally

I'll clarify my opening prescription- living in under 400 sq ft. is an arbitrary residential square foot benchmark, not a numeric prescription. My intention is to convey that the smaller the residential footprint per person, the less the environmental impact. I've provided background data about living in smaller spaces in an earlier post. This post will focus more on residential location choices.

You can find more wonderful infographics that originate from the same report in my earlier post entitled Common Forms of Living Smaller. You can also watch a 1.5 hour Oregon DEQ presentation about the Residential Buildings: An Evaluation of Waste Prevention Practices Using Lifecycle Analysis report on EPA's website.

This quantitative analysis of residential construction types shows that in terms of residential housing types, housing size is the most significant variable in terms of ecosystem quality, human health, and energy consumption.

Urban Density

Urban density is an important factor to sustaining a vibrant urban, walkable community. The urban density in US cities is an average of 2,900 people/mile. Portland's average urban density is 3,507 people/sq mile. By comparison, New York city is 23,705 people/sq mile and Pheonix is 2,342 people/sq mile (based on 1990 Census data). My neighborhood has a density of 4,241 persons/sq mile, or 14 people per acre.

When a sufficient level of residential density is overlaid other critical aspects of urbanity, such as mixed zoning districts that include employment opportunities, readily accessible park networks, a variety of housing and transportation options, a region will significantly reduce its energy demand per capita.

Oregon had the foresight to create an urban growth boundary in 1977. This 30 year old policy, has resulted in a range of benefits that are becoming increasingly evident to urban planners and residents alike. The proactive, multi-jurisdicational, planning modality, appropriately reflects and manages the region's transportation, housing, and employment demands.

Portland's viable transportation alternatives and vibrant neighborhoods are a testament to the success of the urban growth boundary. A range of other unique urban planning policies and natural assets have helped make Portland walkable and community focused. While most, if not every, city in the US has seen a growth in total vehicle miles traveled from 1996-2008, averaging growth of 9% over that period, Portland's total vehicle miles traveled from 1996-2008 has dropped by 12%.

The following screen shots were taken from a presentation by Peter Calthorpe, Calthorpe Associates.


Contrary to a popular assumption that transit is the most viable alternative to driving, using the following graphic, Peter Calthorpe explains that transit should be conceived as a third tier support mechanism for walking and biking. In the western, industrialized cities in Europe, transit is not the dominant form of transportation, nor is driving. The dominant form of transportation is actually walking and biking.

Cities have to focus first on making places that are walkable. Transit should be perceived as a way of extending the walk/bike domain. To accomplish this end, cities need to provide more mixed use, high density housing choices in a range of prices within given neighborhoods.

Hidden Personal Costs of Living in Sprawl

However, even if no active policy choices are made to adopt and adapt cities for future livability, the market will nonetheless steer builders, architects, developers, in this direction. The demand for exurban, large lot housing is going to slowly decline over this generation, and large lot exurban properties will be increasingly labeled as a liability.

Here's a couple personas (Dave and Karen) that exemplify common lifestyle differences between Dave, a resident in a single family detached house in a "conventional suburban development", compared to a Karen,  who lives in a multi-family building in a "transit oriented development", and the respective amount of energy (BTUs) that they use as a result of their transportation choices.

This data is based on a report called "Location Efficiency and Housing Type - Boiling it Down to BTUs," that was funded by the US EPA. This presentation from which these graphics were extracted is available on this website.

Market Trends Towards Urban Revitalization

Solely allowing the free market to guide urbanization trends means that the urbanism trend will not be coordinated and managed as well as it could be, and will cause financial hardship for many homeowners and municipal governments.

Graphic from a report called Growing Cooler

Embracing Infill Housing Programs

ADU's are one of many programs that cities should actively adopt in order to to increase housing options in areas where there is sufficient housing demand. Currently, many communities do not allow ADUs. Moving forward, urban communities that are seeking to actively embrace an environmental ethic should seek to:
  • Expand the range of allowable housing options and areas in which they may be built
  • Revise policies that make these housing types impractical
  • Consider ways to reduce the reliance on variances and expand "as of right" development opportunities
Recommendations from

In the US, I think that we owe it to the rest of the world to reduce our energy consumption footprint. In the US, living compactly is a contrarian choice, but the dominant habitat that we observe and experience in the US when driving from one place to another is neither healthy for us nor sustainable.

But, individuals can make an active decision to live in a smaller space at home, to live more compactly within their community, and enjoy the financial and lifestyle freedom that these choices provide. Indeed, there are social and health benefits to living smaller, but perhaps the most compelling reason is the decreased transportation and decreased housing costs associated with this passively virtuous choice.

Monday, June 6, 2011

Rough Plumbing

Last week, the plumbers did the rough plumbing for the ADU. There wasn't too much progress to point out each day, but overall, it's interesting to see and understand how the plumbing actually works. The videos below are my attempt to show and explain how the ADU's plumbing works. But, here's a quick overview of some of the significant aspects of the plumbing design.

PEX tubing is used to convey potable water to and through the ADU from the street water main. The water is about 50 degrees when it reaches Portland  from the Bull Rull Watershed in the northwest foothills of Mt. Hood. The ADU's water main immediately splits when it gets to the ADU, sending one PEX tube directly to the tankless water heater (which hasn't yet been installed) to be heated. From there, one hot and one cold PEX tube is then directed to each of the main hot/cold water fixtures (sink, shower).

I've put all the fixtures (bathroom, sinks, etc) on the east side the house to minimize the amount of energy needed to pressurize and convey the potable water around the ADU. Since the house is going to be heated by hydronic, radiant floor heating, the plumbers are taking on the role an HVAC contractor would normally play in most American homes. It's interesting to note that most houses in other countries are not heated by forced air--that's an American thing. Anyhow, minimizing the number of subcontractors involved in the house conditioning gives me a little more executive control over the integrated home mechanical design and saves me and the builder some of the administrative hassle and cost of dealing with so many different sub contractors in the building process.

The sewer drain slopes toward the existing sewer in the main house through the gravel beneath the slab at a slope of 1/4" per foot. Once it joins up with the sewer drain on the main house, it is funneled out to the city sewer in the street.  Finding an appropriate place to position and slope a large sewer pipe was a little more challenging due the smaller size of this structure. Sinks and toilets each have an air gap to keep any sewage odor from coming up from the sewer through those fixtures and into the house. You've probably seen the J-shaped air gaps (or traps) beneath your sinks. In order to properly drain those same pipes then, the air pressure must be equalized on either side of the waste water (or the liquid would be stuck like water in straw that you've capped with your thumb). So, each plumbing fixture has a vent to allow the sewer run to properly pressurize to allow the waste water to drain. The vents that you'll see in the video look like sewer pipes, but they're smaller.

You may have noticed the ends of these vents in your roof in in the form of 'roof jacks'. Usually, there's a roof jack for each water fixture. When designing an airtight structure however, it's a best practice to minimize the number of exterior sheathing penetrations (holes in the exterior walls and roof). So, I asked my plumber to combine all of the vents inside the house to create only one roof jack for the whole structure, instead of four roof jacks.

Ok. On to the videos. Here's an overview of the plumbing.

The two radiant loops on the 2nd floor

The roofing and skylight windows were put up in two days.

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