Subject: Insulations levels in a passive solar house

Question:
I’m interested in building a passive solar house using Insulated Concrete Forms (ICF) walls, R-60 ceiling. What’s appropriate for under-slab in total R value?

Answer:
I’ll quickly point out that a passive solar house of the 70′s and 80′s is quite different from a home built to the Passive House Standard [click here for more info on that subject].

Now, back to your question, the answers that I may offer will vary, depending on your goals for the project. If the goal of the project is to meet the Passive
House (PH) standard of efficiency, I recommend that you have a qualified
Passive House Consultant enter the project plans into the appropriate
energy-modeling software.  This is the only way one can ascertain appropriate R-values for the various components within a project.

The super power of the PH approach is that the designer and the builder will know exactly what each specification needs to be, and why.  Cost/benefit
tradeoffs become easy to model, and in the end it can be said with a high
level of confidence how much heat will need to be delivered by the home’s
mechanical system, whether or not the home will overheat in the summer, etc.
There is no prescriptive path that will achieve the PH standard, because
every home represents a differing set of climate conditions, design elements, and site conditions.

Please note there is are very real benefits to hitting the PH standard of
efficiency:  the home can be heated with a source that is equivalent to a
hair dryer, and saving money by not installing typical or higher cost
mechanical systems will free up funds that are better spent on the home’s
thermal envelope.  In a PH, the energy savings will pay for thermal upgrades
in a just a few years.  After the point of breaking even financially, energy
savings will accrue to tens of thousands of dollars over time.  Actually, in some homes, the homebuyer can save money up front when ‘going Passive’ vs. other methods of construction. The trick is to work with qualified designers and builders and to perform Passive House Energy Modeling as part of the process.

Database of Certified Passive House Consultants in the US:
www.passivehouse.us/consultants.php

We particularly enjoy these types of questions, read on for the questions and answers.

[From the client]

“I hope this is not too premature.  We have been looking at kitchen
appliances and plumbing fixtures.  We are starting to figure out what
we want and don’t want and are narrowing our choices down.  Some
technical questions have come up that depending on the answers could
direct us in different directions.”

Q. We prefer cooking with gas and know that gas produces moisture.  How would this affect the air environment of a passive house?

A. Cooking with gas works just fine in a PH.  The act of passing the fresh incoming air across the heat exchanger within our Heat Recovery Ventilation (HRV) system tends to reduce the relative humidity level in the home.  There is a small pipe at the bottom of the HRV that delivers condensation water to a drain.

In some climates, this drying effect is actually a problem, and in those cases we would choose an Energy Recovery Ventilation (ERV) system instead of an HRV.  ERV’s manage humidity in addition to performing the heat exchange function of an HRV.  However, in the pacific northwest, the ambient humidity and the action of the HRV act together to keep the indoor relative humidity at a level that is recommended for humans.  Because enough air to completely fill the house is brought into the home through the HRV every three hours or so, cooking with gas has little impact.

Q.  Cooking with either gas or electric produces lots of heat as well. In a passive house how comfortable will the kitchen be in the summer?

A. In a regular house, when it comes to dealing with cooking heat during the summer months, you can open windows and doors as needed.  That’s what you will do in a passive house as well.  Additionally, you can turn the HRV up to the high setting, using a booster switch that will be installed in your kitchen.  This will bring fresh air into the entire house as needed.

If it is too hot outside to gain some relief by opening windows or running the HRV, you will be no worse off than you would be in any house.  But living in a PH reduces the effect of high outdoor temperatures during those hot afternoons.  In the summer, you can open things up at night and close them up during the day.  Because the home is super-insulated, chances are that your home will be cooler than the house next door is on a summer afternoon.  There will be days when you are enjoying your indoor temps and you don’t want to cook indoors and warm things up.  But in a PH, you will have a better chance of avoiding having this be the case.

Q.  Today we were introduced to the idea of induction cooking stove tops as a way to reduce the problems of moisture and heat. Do you have any thoughts on this?  We are both not drawn to that style of cooking, but thought maybe we should consider it.

A. Some of our PH owners selected the induction cooktops.  They are pretty neat!  If you are attracted to the low energy use, fast cooking times, and the fact that the surface of the cooktop does not really get hot, an induction cooktop may be for you.

Some of our PH owners cook with gas. They have reported no issues specific to this approach.  So, don’t avoid gas cooking if that’s what your prefer.

Q.  When we were at Albert Lee in Tacoma we discussed the concept of recirculating vent hoods like you showed us in the two houses we viewed with you.  The salesman there gave us the low down on them and seem to be not as efficient at removing the heat, moisture, smells, grease as a regular vent hood that exhausts to the outside.  We have concerns about this technology and would like to understand better how the heat exchanger is going to take care of the recirculated air from such a vent hood?

A. I think it’s generally true that a recirculating range hood will not be as effective as one that is vented to the outside of the home.  But when you have an HRV in your home, this is not a problem.  The range hood is there to collect heavy steam and the grease that is in the air right above the cooktop.  The HRV deals with everything else – minor cooking smells, moderate increase in humidity, etc.

It’s important to remember that the HRV is is moving a lot of fresh air into the entire home, and that this approach works well.  Here is an analogy: If you have a pool in the yard that is full of water that is never cleaned, you will be really picky about keeping impurities out of the water.  But if the pool has a stream running into and out of it all the time, the flow of water from the stream will keep the water in the pool clean, even if impurities are introduced occasionally.  I hope this analogy applies for you!

Q.  Like wise we are still concerned about the amount of moisture released by showers and cooking and how this will be evacuated from the house.

A. We will install booster switches in the kitchen and the bathrooms that you can use to turn the ventilation system up to the high setting.

Summary:

Current ventilation code requires fans that are rated to remove 50 cubic feet per minute be installed in bathrooms.  In actual practice, most fans in bathrooms today don’t move the amount of air that they are rated for.  But we turn on those fans and they do the job if they are not too crummy!  The typical owner of a regular home never knows how much air is being moved by the exhaust fan.

When you buy a PH from The Artisans Group, after the home is completed, Randy and an experienced Engineer will show up to test the ventilation system.  We spend two hours, and use specialized equipment, to measure air flow at various flow settings on the HRV (low, medium, high, etc.)  We check the air flow at every single ventilation register in the home, and take the time to adjust the system until it is offering air flow rates that are consistent with our design goals for the home. After you are in the home, if something goes awry, or you don’t see the results that you want when you are cooking or showering, we will want to know about it!  We will come back and adjust things until everything is groovy.

[editors note] We received an email from a reader who made some noteworthy observations regarding the efficiency ratings of gas vs. induction cooking~40% to 85-95% respectfully. Also worth mentioning is gas is not a renewable resource. Good points!

The balance of the day held juicy discussions about how to manage moisture in a PH, the systems from water to air handling, details on energy modeling,  building efficiency trends, PH initiatives, and current projects show and tell. Artisans Group was there to present and answer questions on two of our current Passive House projects (North and The Jewel Box). Following the conference, we hosted a small tour through the homes for attendees.

There are around 300 or so Certified Passive House Consultants in the U.S., a growing number, but not too many yet. These events are a critical playground for many of us to get together and compare notes, and share successes and failures, there is no question the Passive House movement is moving… at a fast rate! It’s very affirming to be in a room with so many great people with capable minds focusing on a common goal and be willing to work together toward the success for the greater global community.

Being a pioneer is not always smooth or easy, but this dedicated group is the real thing. We’re glad to be part of it.

[Reader Question]

My husband and I are considering building/remodeling a home in the next three years. The idea of a passive house appeals to us strongly. As we think about the future, we’re wondering whether a custom passive house is a realistic choice for our family.

Right now, our ideal would be a home around 1800-2300 square feet in the Seattle area. Our budget by then will be in the range of $500-600K for land and construction. Our question is whether we are out of our league, hoping to build a house of that size on that kind of budget.

More generally, what recommended reading would you suggest for people in our position, considering building in the somewhat-near future? Books, blogs or magazines about design, architecture, or green building? Any suggestions would be welcome.

Thank you for your time.

[Reply from Randy Foster, president | The Artisans Group]
Thanks so much for contacting us.  The brief answer to questions about the cost of a Passive House (PH) is that I think it is quite feasible to build a PH within the budget that you have described.  Of course, the big variable will be the cost of land.

The cost of a PH is not really that much higher than any other custom home.  The PH approach is based in spending money on the home’s thermal envelope (windows, insulation, doors, etc), and not spending money on heating and other energy-related systems that can be really expensive in other green approaches.  The cost increases and the savings largely cancel each other out.

The idea that I’m trying to highlight is that PH is a cost-conscious way to design and build a home.  I did not arrive at building Passive Houses through my sensibilities as an environmentalist. Though, this method is good for the environment and for society as well, which are huge bonuses.  But my earliest attraction to the paradigm is rooted in managing financial risk by limiting exposure to rising energy prices.  PH is fiscally smart.

So… I can get off of the soap box now and offer some price ranges for Passive Houses that we are currently designing and/or building:

• $150/sf for a really cool semi-modern-styled home, 1,100 sf, with modest selections of roofing, siding, flooring, cabinets, etc.

• $170/sf for an “elegant farmhouse”, 1,700 sf, with an attached garage and carport.

• $210/sf for a waterfront modern home, 1,500 square feet, with selections that are more exciting, from a design point of view.

Each of these examples illustrates a home that is perhaps a bit smaller than the home I understand you are considering.  That’s good news!  Creating a super-energy-efficient home tends to be easier and more cost-effective as the size of the home increases.

There is a tremendous amount of high quality information available on PH. Specifically, there are a couple of excellent books that will give you a solid understanding of the method itself and which feature PH projects around the country:

•Homes for a Changing Climate Passive Houses in the U.S. by Katrin Klingenberg, Mike Kernagis, Mary James

•Recreating the American Home: The Passive House Approach by Mary James

Thank you for your interest!

As I sit here winding up the week, getting ready to head over to the Methow Valley for a few days of holiday fun with friends, it occurs to me that it’s been a really good year.

These past couple years have been a time of tricky dichotomies and social change, new awareness, synergies and letting go, studded with complex challenges and rich opportunities.  That’s a colorful brew that has made for some very interesting times.  Strangely, I feel better for it in many ways, and I know I’m not alone.

It may be fair to say that, as a company, we’ve learned more in the past two years than in the previous 13 years combined. Adversity is a candid instructor, and yet, here we are enjoying our work more than ever. How could that be? I suppose one shouldn’t question a ‘win’.

We are absolutely grateful to be on the planet at a time and place which allows us to participate in effecting positive change and to enjoy collaboration with other like-minded people. It’s an ideal time to be alive.

I read this wonderful excerpt recently from Bill Stumpf’s book, The Ice Palace That Melted Away: Restoring Civility and Other Lost Virtues to Everyday Life. I find there is a certain simple and universally accessible luxury and truth in his words. Civility costs nothing to proffer and is priceless in its viral capacity for lightening hearts and bringing joy.

I wish you all personal peace and prosperity for all the coming years! Zeta

[Excerpt}

“Civility is something extra– the added measure of grace– in the way we shape human behavior through objects and custom…” “Civility is comfort, hidden goodness, social lubricant, personal worth, helping others, play- civility is the joy we take in our human achievements and the compassion we show toward our all-too-human faults. Civility can be extended by technology and can be obliterated by it. Civility is toleration, understanding. It is the integration of differences, not the heightening of them.”

On Saturday, Randy presented his PH payback modeling spreadsheet at one of the sessions; he had tremendous feedback from the audience. The spreadsheet allows a PH consultant to easily represent the payback period to upgrade to a PH from a typical home. Because the math involved in conveying this information is otherwise complex and off-putting, Randy rendered it into a graphical representation that is easy to appreciate by all parties. This is especially great for the homeowner because it helps them to make informed decisions about choosing PH; when they see the payback is often under 10 years and their monthly utility bill is down by 75% or more, PH sells itself. And that makes our jobs so much easier! [click here to read an earlier post about this spreadsheet]

Another highlight of the conference was  to listen to  two legendary powerhouse physicists,  Amory Lovins, green energy guru and Dr. Wolfgang Feist, founder of PH,  share the podium to convey their thoughts and insights on Passive House and the future.

With the numbers of PH consultants on the rise (15 in 2008 to 200 this year), there are many PH projects in the works nationally, which were the subject of many presentations. We were particularly impressed with the Habitat  for Humanity prefab PH projects on the east coast. The idea of affordable and deeply energy efficient has been theoretical until now. Very exciting times in the building industry.

We toured several PH projects in the Portland area on the last day of the conference. That was a wonderful opportunity to see the different assemblies designers are coming up with. Because Passive House is not prescriptive, the ‘roads to get there’ are varied. We saw traditionally designed homes to modern, we even toured a remodeled home, quite impressive!

I must say, after three days with all these fine folks, it was the best conference I’ve ever attended. The information was timely, critical and stimulating, at the end of the three days, I was exhausted and super-charged by the people involved and the subject matter. There is an interesting and distinct willingness of PH industry folks to share their knowledge freely about lessons learned.  The personality of the PH movement feels very healthy and cooperative, everyone seems to work and play well together despite the perception of ‘competition’; I’ve heard people comment several times, “there’s plenty for everyone”. This open source approach creates a strong sense of team-work, a very compelling and inviting way to propel a revolutionary movement forward!

Lastly and most importantly, a warm thank you to the hard-working folks at PHIUS who created this opportunity for all of us.

Passive House Homeowners

PH Living Room

Amory Lovins

Dr. Wolfgang Feist-Founder of PH

Portland PH-under construction

PH Modern Kitchen

Suppertime PH fun!

Passive House: Isn’t it a bit of overkill? James Jenkins, Certified PH Consultant responds

And if that weren’t enough, we won Judge’s Choice for the Home with the BEST Green Features…. and if THAT weren’t enough, we had two other homes on the tour that we designed, and they won BEST in Show and BEST Curb Appeal.

We sure appreciate OMB for hosting this event and creating this wonderful opportunity for the building industry in Olympia!

Best Green Features

Best in Show- Design by The Artisans Group

Best Curb Appeal- Design by The Artisans Group

Close up – Larsen Truss wall section prior to tilting into place. Note thermal break between studs.

Thanks to a recent reader comment, we’ve taken the time to address the question (one we often get) about structural insulated panels (SIP) and why we don’t use them.  Read on if you are curious.

Comment from reader:
From the photo it appears that you’re not using structural insulated panels (SIP) on this project.  Can you tell me what design you’re using?  Thanks.

Reply from Tessa Smith, Certified Passive House Consultant | The Artisans Group

Great question! We chose not to use SIPs on our Certified Passive House for several poignant reasons. We found on the North project that we could achieve better energy performance for less cost with a Larsen Truss wall assembly.  A Larsen Truss is essentially a double 2×4 wall with plywood gussets at three locations that make the outer wall cantilever off of the interior core, which is load bearing and lateral.  This also simplified our floating slab assembly, because we can’t have any thermal bridging in a Certified Passive House, we needed to wrap our foundation in insulation at least 6 inches deep for performance reasons.  A SIP could not be used in this instance, they are not strong enough to cantilever one of their skins off of bearing, and a continuous bottom plate would be an unacceptable thermal bridge.  The Larsen truss bears on our edge of concrete and then cantilevers over the continuous foam beautifully.  SIPs are very costly, and tend to get cut up at every lateral strap location and plumbing or electrical junction.

Another reason we have yet to use SIPs on one of our 12 Certified Passive House projects, is its intrinsic HIGH embodied energy.  We try to use as little foam as possible, foam processing and energy consumption in the manufacturing process is not a pretty thing, not for human health and not for the environment.  In our project we have air tight construction, paired with an open diffusion wall (a wall that can last over 200 years) with dense pack cellulose or fiberglass, both of which have extremely reduced carbon footprints and cost in comparison to SIPs.  Also we don’t expose OSB to the weather side, an element of longevity in my opinion.  There are many cases where SIPs don’t last the test of time on there outer skins.  In our more recent Certified Passive Houses, we have gotten away from any foam at all, which is very exciting!

At one time, SIPs were a good upgrade to achieve a more energy efficient home, albeit expensive and not accessible for many people.  It’s possible there are acceptable uses for them still but, I  have yet to find an opportunity where I couldn’t get better performance for less cost and embodied energy on a project.  The PHPP modeling software gives us the opportunity to model homes with an accuracy that can’t be touched with ANY other modeling tools available on the market, the kind of information it yields allows us to run iterations and see curves of return on investment with material choice and very subtle design tweaks (the kind that can’t just be rule of thumb).  With that, we’ve determined our current construction method to be the most cost-effective, highest performing approach with the least environmental impacts. It just can’t be beat so far.

I recently caught up with DT North to interview him about his experience so far in building the second Passive House in Washington State:

Describe the home project you are involved with at this time.

We are building a 2300 square foot house in the Northeast Olympia neighborhood, it’s currently in framing stage. The house is being designed as a Certified Passive House and Built Green Level 5. The house will be twice the size of our current home and use 15% of the energy. It is a 3 bedroom 2 1/2 bath with understated, modern styling. The exterior design was inspired partly by the classic farmhouse shape and  the interior  was inspired by great rooms you see in city lofts where the kitchen, dining room and living room are all connected. The vaulted ceiling is 17 feet at it’s peak; the great room will be naturally daylighted by large southern exposed dual-purpose windows. There is an ‘away room’ off the great room that will be used as a family room and transformed into a guest room when needed. We thought it was more useful to have a room like this instead of a 4th bedroom that would not be used 90% of the time. The master suite is on the main level and has a good sized bathroom which is a barrier-free; as we age, the house will function well for us–even if we become disabled.  There are two bedrooms upstairs for the kids and they have their own bathroom. The home will have tons of built in storage.

The home is being built on our current property. We are fortunate to have purchased a double lot in 1999. We love the neighborhood but have outgrown our current house. We have a 15 year old boy and a 9 year old girl and our current home, at 1200 square feet with poor use of space, motivated us to upgrade. We looked at remodeling and at purchasing a larger home. The two problems that came up were that we could not find anything in our neighborhood that suited our needs. When considering remodeling, we were told that we may find issues with the current home that presented some problems: the house was built in 1929 and poorly remodeled twice in the last 40 years. We even looked at purchasing a lot and building but found that permitting and new construction costs were prohibitive.

You and your wife are early adopters with this building standard, prior to building a Passive House, was ultra energy-efficiency and sustainable design at the top of your ‘must have’ list?

It is certainly the case that whether purchasing a car, a home or any appliance that uses energy, we consider efficiency and sustainability. It has simply been within our paradigm since we were quite young.

You have two children, are they interested in this really cool new house?

They are always interested in “the new”. They are going to have a lot more room in the new house but are pretty accustomed to Kim and I being intentional and conscious in our purchases and lifestyle.

Did you know about Passive House prior to coming to The Artisans Group?

No, Tessa Smith, the designer was the first to raise our awareness. Over the years, Kim and I have looked at home building methods such as geodesic domes, earth houses, structural insulated panels (SIP), straw- bale, etc. But none of the other methods had a quantitative performance-based design built into them.

Has The Artisans Group been a good choice for designing and building your new Passive House?

No question. The quality, creativity, expertise and service have been second to none. We had tried to build a home a year ago and the deal went south after we learned that our needs weren’t being met. Artisans was empathetic about our prior experience and since working with them we have been extremely happy.

What was the project development process like? Was/Is there much of a learning curve for you?

We started with talking with Tessa about our life style, values and design elements that we liked using magazines, books and internet sites. Tessa used that information along with the parameters such as budget, building in the space on our current lot to come up with the design. We provided Tessa with feedback on the design and made some minor tweaks. She adjusted and we had two more iterations of the basic design. We got a “ball-park” figure on a cost that we could live with. This included a couple of options. After we selected our ball park options we started to work on energy modeling through Passive House Institutes complex software system. Randy Foster and Tessa met with us during this process in order to further tweak the design to meet the performance criteria. Simultaneously, we began work with Diane Gassman to make selections such as cabinets, lighting, fixtures etc.

We fortunately did not have much of a learning curve on the basics as we had been through the whole process a year prior with another builder. The team at The Artisans Group was great at helping us through the process and asking for feedback on how the process was serving us. Julie Buzzo, the drafter, let us “play” with the computer rendering. We were able to see inside the house and look at rooms from different angles in the computer program. It was like walking through a virtual house. Diane was a wealth of knowledge in identifying vendors. When we tried to find those “hard to find” items, she gave us contacts all the way from Olympia to Bellevue and Portland. The vendors she referred us to had the products in stock so we could see them first hand. Tessa was always there to give feedback on how any particular selection would fit with the style and design element (there is was a learning curve here as Kim and I have never been into interior design). You can really get bogged down by the shear volume and minutia in making selections. Tessa and Diane were great at helping us see the forest through the trees. Randy was there to meet, discuss and advise on the more pedestrian, yet crucial issues involving cost implications and impact on the energy consumption. For example, Randy was instrumental in pre-wiring the house for installation of solar panels down the road.

How has it been living on a construction site?

I really thought it was going to be more difficult than it has been. One of the benefits of living at the site is you get to see the progress daily. The only drawback has been the space that the construction takes up. The new house is being built on our driveway and we no longer have access to our garage. The dirt from excavation is being stored on the side of our house. This will be used to back fill around the house once it is completed. We have temporary stairs to our porch that we use until construction is done. The crew arrives anywhere from 7:00 a.m to 8:00 a.m. and stay until the end of the day. We have a separate entry for our cars that was cut through the existing hedges. Mark Dixon, the lead carpenter has been great at explaining the construction process. About once a week, I spend a few minutes talking to him about the progress and next steps.

We know Passive House is the most sensible way to achieve net-zero, particularly in our region, do you think you’ll pursue solar electricity for your new home?

We hope to install a system that will feedback power into the grid. I learned just this week that there currently is no Washington State sales tax for solar power systems. There is a 30% federal tax credit. And, if we buy Washington State built products, the power company will buy any energy we feed into the system at 6 times the rate we pay them for energy. We currently pay 8.5 cents for a kilowatt hour for the first 600 kilowatt hours per month. Any energy we feed back into the system, they will pay us 54 cents per kilowatt hour up to $5000 per year. Our house is expected to use 4000 kilowatt hours per year. If we buy a system that produces 8000 kilowatts, we will be an energy producer. We will be able to pay it off in 3 to 6 years (depending on energy price increases) and have no direct energy costs.

You’ve been a very engaged participant in every aspect of development, has this been fun for you?

It has been a lot of work. But that is the cost of living intentional and conscientious. This is the biggest purchase we will likely ever make and will likely only do it once. I wouldn’t have it any other way. It has been a great journey so far.

You’re creating history with this seminal project, it will be the second Certified Passive House in WA state, how does that feel?

I’m not sure how to answer that question. I leave it up to others to determine whether we are creating history.

We feel fortunate to have this opportunity available to us. One year ago we did not know about this option. It just so happens that we are the first in the area. I think if there were many PassiveHouses in the area we would have selected this option. There are obviously some risks to being leading edge but given the information available through the Passive House Institute and existing Passive House owners across the county show that the design works. The certification process is rigorous and we are confident that it will work.

Thanks so much DT!