Flooring and Tiling

This is an update on the ADU progress.

First, I shot a quick video of the new electric service being added. The ADU will be separately metered, which is apparently a new City of Portland regulation. Bummer, since it cost me $2,000. But, by adding new service, there is ample power for both units and both units will not experience power outages as frequently.



But, mostly, we've been flooring, tiling, and siding. These three processes are time intensive, but the products are all beautiful in their own right.

The Beginning of the Long Haul

Over the last couple weeks, we've been painting the interior walls like mad and working on the siding. The electrical was installed so now there's ample lights to work at night as well as during the day.

The work that happens after the foundation, framing and drywall, seems to go a lot slower than the first phase. Since my overall project funds are now pretty low, I will be doing more of the work myself. We're gunning for a September 1st move-in date.


This video is a status update of where things are in the project.

Adding Some Color To Our Lives

I thought that I was going to have the house painted by others, but I ended up painting it myself over the weekend. It's taken me about 20 hours so far--I probably have about 4 hours to go still. I've been listening to lots of podcasts and painting late into the evening.

I needed to do the painting before proceeding to the installation of the wood flooring, or staining the concrete, in order to prevent possible paint spill mishaps on finished floors.

The first step after completing the drywall was to prime the walls. After priming, I had pros paint the 20ft high ceilings white with a paint gun.


Once that layer had time to dry, we selected colors for the walls. We made the colors ourselves using whites with an eggshell glean as the base, and adding purples and reds and greens. When I had to buy more white paint, I purchased "mistints" at the paint store (paints that were returned for some reason) which was a less expensive way to buy paint since I wasn't picky about the white base color.

We eventually created a nice palette of colors to use. We chose a purple, green, and a salmon color for most of the surfaces. I am a little bit color blind, so I left the color selection mostly to my girlfriend.



I spent the whole weekend painting and have almost finished. It looks great.

Financing Your ADU

There are two main barriers for homeowners who wish to build an accessory dwelling unit. One barrier is zoning and building codes. In many municipalities, due to existing building, planning, or zoning ordinances, ADUs simply aren’t allowed. 

The other barrier, which is equally formidable to those who live in places that DO allow ADUs, is the capital cost required to build an ADU. Many homeowners are intrigued by the idea of building an ADU, but financing an ADU in real life is daunting. This post is a detailed exploration of costs, funding approaches, and other options that you can consider in order to fund ADU construction. 

As I’ve written about in a previous post, my personal top priority for this project was to create a financially sustainable living situation. I see ADU’s as a very sustainable way to reduce living expenses, and even a way to generate significant income. However, the initial expense was a formidable barrier for me, as it is for everyone. Case in point: I estimate that my project will end up costing about $92K; you can read more about that cost breakdown.

How much does it cost to build a custom ADU?

Design/build cost for new construction ranges between $100-175/sq ft for a small, fully livable dwelling unit. For an 800 sq ft ADU, one should count on spending $80-140K, depending on the style of construction.  

For the purpose of this blog post, let’s say that we plan to build a 400 sq ft ADU. At $100/sq ft, we'd only spend have to spend $40K. However, smaller structures tend to cost more per square foot. For a 400 sq ft ADU, you should count on paying closer to $125-$200 per sq ft (aka. $50K-80K).

This increased cost is due in part to fixed costs. For example, no matter how small the structure that you’re building, you’re probably going to have to pay at least ~$5K just for plumbing, $5K for electrical and $3-5K for a permit. For a 400 sq ft ADU, you man end up spending almost as much on plumbing, electrical, and permit as one would spend designing/building a 2000 sq ft house.  My point is that you'll save money on most of your costs by building smaller, but there is a diminishing return on building smaller in terms of savings. 

Major Design Considerations that Significantly Reduce Design/Build Cost: 

• The cost for pre-fabricated houses is considerably less than custom new construction. Here’s an example of very pretty prefabricated cottages that start at $14K. I don’t know how to permit a prefabricated cottage as an ADU, but this seems to be a viable ADU design option to pursue if you’re on a very tight budget. Also, consider “tiny houses” or trailers if your budget is limited to about $10K.
• You can save big dollars if you build a “detached bedroom” or structure under 200 sq ft that does not require its own plumbing or kitchen. If you are just looking to expand the livable space of your property to build a guestroom or office, you can dramatically reduce your projects costs by simply not constructing an "Accessory Dwelling Unit". In Portland, structures under 200 sq ft don't even need to be permitted. However, such structures also not supposed to have basic building services that do require permits, such electrical, plumbing, or heat. Plenty of people reside in such structures though.
• Obviously, the more labor that you do not pay others to do for you, the lower your total design/build costs will be. I’ll cover this in much more depth below.
• According to one builder and an article that I have read on the matter, the costs for converting an existing garage are approximately the same cost per square foot as new construction (depending on the condition of the foundation and structure). Building an ADU from an interior carve out or bump out from an existing house, basement, or attic, are considerably less expensive than a standalone detached ADU. 
  

Building a Non-Permitted ADU:

In Portland, you can count on paying between $3-6K for an ADU permit. Nationally, where ADUs are allowed, permit fees will vary greatly by municipal and county jurisdiction. Portland has conventionally required System Development Charges for ADUs, which typically cost about $10K. However, through June 30th, 2013, Portland has waived System Development Charges for ADUs as a regulatory incentive to promote ADUs. You can read the City of Portland’s full stately and elegant policy statement about this issue here (I think it’s a great read, actually).

Read the full ADU system development charge waiver policy here

Non-permitted ADUs are cheaper to build. There are major drawbacks to building without permits,  but I understand why people would choose this option. A single conversation with a city planning officer, who tells you that you can not build where you would like to build, or that you would need to replace what you thought was a perfectly solid foundation in order to build a permit-able ADU, may be enough to spur you to bypass the permitting process altogether. 

In fact, one local study of MLS listing descriptions indicated that only 38% of ADUs in Portland were actually permitted -- most of the ADUs in Portland have not been built to code nor permitted. So, if you choose to go this route, you're not alone. And, where ADU's aren't allowed by code, you may feel that building without permits is the only option available to you. Interestingly, Tiny Houses were born as a smaller dwelling option that exploited a regulatory loophole that allows smaller, accessory houses---as long as they're on wheels.

Financing Options

1) Savings and Liquid Assets

The easiest and best way to finance an ADU is with pre-existing savings, but most of us don’t have $50-200K cash to spare. But, think it over. Maybe you have a retirement savings 401K plan against which you can borrow cash. Others may consider selling stocks other property to generate sufficient capital. And, some people may have family or relatives who are willing to loan you money at a low interest rate. 

Remember that even a 3% interest “family-loan” rate is a better rate that most retirees can reliably get for their retirement savings in this sluggish market, so this investment loan may be more appealing to your endowed elders than you would think.

2) 203(K) Loan

For those who are purchasing a new home, consider wrapping an ADU construction loan into your mortgage. FHA 203(k) loans are intended for people who are buying a home and want to make repairs and renovations to the property.  The program is supposed to help revitalize/rejuvenate the country's existing housing stock.

The rules for 203(k) loan projects that can qualify are a bit vague.  The rules do say that you must rehab an "existing dwelling" but they also say that you can buy a house, raze it and use the program to build a new house as long as you use some of the existing foundation.  So it's not really written with ADU's in mind, but it seems you can get an ADU project to qualify if you have an existing structure like a garage that you're going to "convert".  

Some banks who want to sell these loans have decided to read the FHA rules in a way that makes ADU projects possible, and then they ask an FHA underwriter to review site plans on a case by case basis.  Some loan officers at some banks that will tell you that you can't build an ADU using the 203(k) program.  Some loan officers are  on the opposite side, actively trying to sell the loans to people who want to build ADU's.

203(k) loans take a lot of planning and work up front. The bank tells you that from the day you have an accepted offer on the house, you have 30 days to submit to them all of the paperwork necessary for them to order an appraisal for the whole (house plus ADU) property. That means, in those 30 days, you need to be able to submit a full bid for the construction, down to some fairly detailed items like what  type of flooring, countertops, appliances, paint, windows, doors, etc.  Basically, they want to know everything about the ADU so they can value it accurately.  Once you submit all of the required forms you're required to work with an FHA Consultant, who has FHA forms to fill out with all of the specifications and expected costs on a line item basis), the bank orders the appraisal, and then your loan processing starts and will be complete in another 30 days.  So it's a total 60 day closing period (minimum).  So you need to have a seller that's okay with that time frame.   

This loan could potentially work if you could use part of an existing structure to make an ADU.  So, this low interest federal loan option is great to consider if you are buying a new house, are already eligible for a 203(k) loan (check with your loan officer), and are interesting in converting part of your house or converting your garage to an ADU.

3) Refinancing An Existing House

Refinancing a home to help you finance an ADU may be a good option to consider if you already have substantial equity in an existing house and the payback calculations for an ADU work out in your favor. And, refinancing has fewer strings attached to it than construction loans.

4) Remodel Construction Loan

Very few banks have taken this step, but according to this article in the Daily Journal of Commerce, at least Washington Federal has made the logical leap to giving out remodel loans for ADU construction. Here’s Washington Federal guidance about their “All in One” loans. 

In general, the difficulty with construction loans is that their rules are more strict, the interest rates are higher, and banks don’t know how to accurately evaluate the value of ADUs yet, so banks are reluctant to give a loan out that assumes a particular dollar value for them.  

5) Live-Work Trade

This next idea is a great option for younger homeowners with relatively little financial capital, and who have talented builder friends. There’s plenty of ways that a live work trade could be structured. If you’re planning on using the ADU as a income generating guest house, you may be able to figure out a fair way to split the costs with relative or friend, making them an business partner in your micro-venture. Here’s one example of a work-trade arrangement: 

Someone I know built a beautiful detached living space in Portland. Simultaneously, he also built a new bathroom and kitchen attached to an existing garage. The detatched bedroom has close, convenient, and private access to both amenities, although it is not physically connected. This detached bedroom structure is approximately 200sq ft, and the materials for the kitchen, bathroom, and detatched structure cost about $15K. He worked with a builder on this project for a year, and rather than paying the builder with cash, the builder had free rent in the bedroom for a three year period, which they valued at $30K. $30K is the amount that he would have paid the builder if he paid the builder with cash instead of free rent for three years. 

This project is about 320sq ft, and cost about $45K (~$140 sq ft). However, because of the live work trade arrangement, and the lack of permit fees beause it isn’t considered an ADU, the whole project only cost him $15K in cash.

This kind of bartering arrangement is wonderful, and indeed, can work out to be very favorably for all parties financially, personally, and professionally. One drawback is that the ADU is not going to generate any income for the homeowner for three years. And, the builder is going to living on their property, which may not be an option for many homeowners. But, if you don’t have access to a lot of capital, a live/work trade option may be the be right option for you.  

As another benefit, since both the homeowner and the builder were very personally invested in how the project came out, the structure came out looking gorgeous.

How to Lower the Design/Build Cost of Your ADU through Time, Labor, and Materials

The amount of work that the homeowner does in designing/building an ADU will vary from none of the work, to all of the work. I suspect that most homeowners who are designing/building a custom ADU are going to want to be at least a little bit involved in the design process, if not the building process. 

Personally, after much debate, I contracted out the majority of the work up to the final stage of construction. Initially, I wanted to do the work myself, but I realized that most of the work beyond my capacity. I could have helped as a laborer if I had more free time, but I could not have constructed the project on my own. However, I will be doing the ‘finish work’, including the hardwood flooring, the kitchen and bathroom, and the painting.

I spent roughly 33% on purely material costs (such as wood, siding, concrete, paint, and appliances) and about 66% purely on labor costs. Labor for new construction in the United States is not simple nor cheap. But, if one had the know-how to do all of this work themself (including electrical and plumbing), and a year of time to put into it, one could have do this job on their own for just the material costs (ie. $30K, as opposed to my projected cost of $92K). 

Furthermore, with enough time and building knowledge, it would be conceivable to source many of the materials that were needed through Craigslist and other building material resellers and design the project partially around those materials. 

For example, I paid $3K for 15 new windows. I think it is possible to acquire 15 wonderful, unused windows for as little as $1000. However, it would be impossible to get a particular kind of window, with say, specific height and widths, or Energy Star specifications. But, if the homeowner is VERY flexible about what materials they use, has ample time to source and collect those building materials, they could cut material costs by possibly 30-50%. It is conceivable that with sufficient time and flexibility, I could have acquired usable building materials for as little as $15-20K (as opposed to $30K, a $10-15K savings). 

The most practical way to source used materials for an ADU would be to collect building materials over time, and design a house using those materials. Some of the building materials would necessarily have to purchased new. For example, if you need to pour a concrete foundation, you would have purchase new concrete. If your project will be inspected, you would need to use many new materials. For example, due to inspections, I need to have new light fixtures with the UL stickers still on them, instead of reusing light fixtures as I had originally planning. And just inexpensive light fixtures, I had to pay nearly $700. 

In summary, if I did all of the work myself, including all of the highly skilled trades of architecture, plumbing, and electrical; and had the patience and determination to build a structure over a very laborious year-long period, I believe it would be conceivable to design and build a comparable structure from mostly salvaged materials for $20K + a working year of my time.  

For me, and the vast majority of the population, this type of DIY scenario is highly unrealistic. But, for an highly skilled homeowner with a year of time at their disposal, this approach may be an option to consider. Given our nation's cultural self-reliant mentality, I am sure that this DIY approach has been used a countless number of times.  

Here's an article about "Re-Creation" house renovation project that a friend of mine built using 90% salvaged materials. As a point of reference, the mostly-used material expenses for this 640 sq ft project amounted to ~$20,500.

Calculating Payback on the ADU Capital Investment 

In my case, to fund the project, I borrowed money from my future self by borrowing against my retirement savings via my 401K. I calculated that the benefit of living mortgage-free after this project made it worth the trade-off of using my retirement funds.  

Generally speaking, financial advisers would not recommend taking money out of a retirement account. While I am paying my future back over the next 15 years, this retirement money is not going to invested in the market. It's an open question as to whether the value of real estate in Portland will increase at quicker rate than the a 401K (which mirrors the S+P 500), but the ADU investment has other financial paybacks that seem more reliable to me the S+P 500.

Upon completion of construction, I will be relatively cash poor and relatively equity rich. The primary house on the property is going to 'cash flow' as soon as I move into the ADU. This means that I anticipate that the rental income from the main house will fully cover the cost of the mortgage, interest, and taxes on the total property. If this assumption is accurate, though I won't have much money left in my bank account, I'll be in a position of relative financial freedom in the sense that I will not have to pay monthly living expenses. 

In terms of resale value, my Realtor described it to me this way. If I spent $100k on my project and assume a conservative number of $50k increased property value, the property would need to earn $50,000 before I'd break even. Conservatively assuming I rented out the ADU at $1000/month, it would take 4.2 yrs to "break-even" on the project. 

I'm guessing that, in reality, the ADU will add $100K to the assessed value of the property. If I resold the property (house and ADU) immediately upon completion this fall, I would not make much profit from this venture. However, if I were to hold onto the ADU for 10 years as a $1000/month rental property, it would generate $120,000 in rental income. The longer that I hold onto the property, the better it will work for me financially.

Personally, I don't intend to sell the property anytime soon, so at $1000/month, the payback period for $92K is 7.6 years. After 7.6 years, the investment will have paid itself back. Since I will be living in the ADU, this equation isn't actually this simple. But, for the purpose of this blog post, we can safely say that the investment pays for itself in 7.6 years or less and then generates income thereafter.

Conclusion 

To me, ADUs represent a very compelling financing investment for homeowners. But, they aren’t possible for many homeowners due to the cost barrier. There’s many factors to consider if you’re starting to get intrigued about the idea of building an ADU, but I’ll suggest that the most important factor to consider is whether/how the ADU will work out for you as a financial sustainable investment, and whether you can figure out some creative financial mechanism to overcome their formidable up front costs. Hopefully, if you're toying with the idea of building an ADU, one of the ideas listed in this blog post will help you overcome that first capital hurdle.

Cedar Shingle Siding

In Portland, one component of the ADU regulation is that the siding, roof pitch, and eave style, must match that of the main house. In my case, the main house has an 'imitation-cedar-shingle' asbestos siding with a 10 3/4" reveal (the height between each course of shingles).

While the City did not want me to put asbestos siding on my house, they did still require that the reveal on the ADU match the main house. Since the main house siding was "imitation cedar shingles", we chose to use real cedar shingles on the ADU. The picture here shows the new cedar shingles with a 10 3/4" reveal to match the reveal on the main house. 

Here's a video of the shingle pallets arriving from a local lumber manufacturer. The shingles are Western Red Cedar shingles from Washington state.



This next video shows the Vortex rain screen and the cedar shingle sealing process.

The Vortex which will cover our Siga wrap, and will allow rain to drain down the side of the house in case the rain gets behind the siding.

We purchased "green" shingles, meaning that they were milled recently. I bought these shingles because they were 1/3rd the cost of kiln-dried and pre-primed lumber. Because the wood is freshly cut however, there is a greater chance that when the shingles sit in direct sunlight for too long, they will start to bow and or turn grey quickly. In order to abate this process, we added a wood sealant called Penofin.



This is a video of the first shingle going into place and an explanation of the double course of shingles that we're using.



By the end of the day, we finished installing a small patch of siding on the west side of the ADU. We started shingling on the west side, the side with the least foot traffic, to perfect the process before we wrap the rest of the ADU.

It is fairly common to paint cedar shingles but I have no intention of doing that. I am thrilled with how the first section of siding looks. I also look forward to years of color and texture variance that will unfold and emerge over time due to UV exposure, rain, and age.

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.

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 WalkScore.com, 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. 

Materials

 

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.

Summary

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.

Building an Accessory Dwelling Unit In Portland from Kol Peterson