Passive Solar Gain by the (PHPP) numbers

It has been a long time since my last blog entry.  Mark Porter and the crew of Porter and Sons Construction have been building a beautiful and what will be an ultra energy efficient home.  I'll be posting pictures of my first site visit in near furture posts.  This post will discuss some findings of the energy modeling effort.

The Passive House Standard requires the use of  the Passive House Planning Package (PHPP) an extensive energy and thermal building performance modeling tool.  It has proven very accurate in predicting home energy use and thermal building performance.   In an earlier post, I presented some basic guidelines for good passive solar design.  This post looks at how home orientation has played a key role in reducing the overall energy demand, annual space heating demand, and carbon footprint of this project. 

Our project has very good solar access, no south shading objects, and the long axis of the home is oriented just 10 degrees east of true south.  How much does passive solar gain contribute to the energy balance and carbon savings?   What would the energy demand and carbon footprint cost look like if the project house was rotated 180 degrees placing the current south windows to the north face?   Would the house still meet the stringent Passive House Standard  requirements for annual heat demand, a  90% reduction in heating compared to a code built home?  How would these scenarios change the carbon footprint annually?

A few basic parameters of the current house design.  South windows are properly shaded during the summer.

• 63% of the window area faces south
• 19% of the windows area faces north
• 13% of the window area faces east
• 5% of the window area faces west

Here are the passive solar gains according to PHPP energy modeling for the two scenarios.

Scenario 1. The current house design as built.  

• Passive solar gains account for 11,642 kBTUs/yr of free energy.  This amount of renewable energy migitates roughly 1,740 lbs of carbon annually.   The annual heat demand is 4.56 kBTUs/sqft per yr, which meets the 90% reduction in heating demand required for Passive House Energy Standard.

Scenario 2.  So what do the numbers look like when I spin the house 180 degrees to the north?

• As one might expect, the solar gain contribution drops dramatically to 6,268 kBTUs/yr and the carbon migitation is reduced to 460 lbs annually.  Based on this example, passive solar design saved nearly 4 times the carbon compared to the home that was spun 180 degrees to the north.

This example illustrates that by taking advantage of the sun through properly placed windows you can greatly reduce the energy demand and carbon footprint of your home. 

There's No Place Like Home

When excavation began on June 9th, 2010 a rainbow filled the eastern sky.  It would have been fitting to see Porter and Sons Construction singing "Somewhere Over the Rainbow" and clicking red sequenced work boots while saying "There's No Place Like Home".  But this is Walla Walla, Washington, not Tornado Alley Kansas, and I suspect neither Mark nor Ben Porter can carry a tune like Judy Garland or own red sequenced construction boots for that matter! ;)  Okay everyone, this was my attempt to make a witty remark on my first construction post. If you have been following the blog existingresources.wordpress.com/  documenting the construction of the first Passive House being built in Seattle, WA  you will notice that Linda always creates a witty post title and commentary followed by a more serious discussion of what's happening in the construction process, so I thought I'd borrow from her.  Sorry Linda, if this is a literairy infringment on your creative talent!  Feel free to comment folks that I should keep the project stuff and not poor attempts at being funny! 

SITE CONDITION & DESIGN CONSIDERATION

The property is a 5-acre parcel with unobstructed solar resources to the south, the lot slopes gently to the north with views of the Blue Mountains to the east.  A major design consideration was to take advantage of the sun for daylighting and for winter time passive solar gain through south facing windows.  Passive solar design strategies add no cost and take advantage of a free, clean, and sustainable energy source.  The sun  has been coming up every morning for a long time and will continue to do so long after we are all gone so take advantage of the sun's path in your next project.  A home that is elongated east to west and oriented to true south has the optimal solar benefit.  As you can see in Figure 1, our house is oriented about 10 degrees east of true south.  As general rule, if your home stays within  20 degrees east or west of true south it will receive about 92% of the solar benefit.  We were willing to sacrifice a little on the optimum south orientation in order to gain early morning light and to provide better mountain views to the east.   

Figure 1.  Site Plan

Here are some very general rules of thumb for passive solar design.  Be on the look out for future posts that provide a more indepth discussion of each of these strategies!

1) Orient your home to face south

2)  Utilize south-facing windows and glass doors to collect solar energy

3)  Locate the main living areas on the south side of the floor plan

4)  Provide for exposed thermal mass to store heat for use when the sun is not out

5)  Provide for natural convection and circulation through open architecture and operable windows and vents

6)  Locate non-living area on the north side and minimize north side building exposure

7)  Provide for a superinsulated and airtight building envelope, while providing whole house energy recovery ventilation

8)  Provide for adequate shading of south windows for summer cooling

What is a Passive House?

Representing today's highest energy efficient standard, a Passive House is a very well-insulated, virtually air-tight building that minimizes energy losses and is primarily heated by passive solar gain, internal gains from people, electrical equipment, and only a very small heating source.  Energy is not wasted in a Passive House.  Ventilation with high efficiency energy recovery provides a constant, balanced fresh air supply that results in an impressive system that supplies superior indoor air quality, thermal comfort, and energy performance. 

Over 10,000 housing units in the last 15 years have been built in Europe to the Passive House Energy Standard resulting in an amazing 90% savings in space conditioning and an overall 75% savings in total energy use. 

Recently, Alex Wilson posted an in depth article at buildinggreen.com that discusses the Passive House standard and approach.  It's a great article if you want to have a closer look at what Passive Houses are all about!   

http://www.buildinggreen.com/auth/article.cfm/2010/3/31/Passive-House-Arrives-in-North-America-Could-It-Revolutionize-the-Way-We-Build/

We have a building permit!

Today, I heard from Porter and Sons Construction that the Walla Walla County Building Department has completed their review of the building plans and have issued the permit to build the project!  Mark Porter indicated that earth work should begin June 9th.  Be on the look out for pictures from the construction site!

Meet the Builder

I'm very happy to introduce Porter and Sons Construction located in Walla Walla, Washington to the building project. I met Mark and Ben Porter for the 1st time in 2006 while consulting on a Passive Solar Home project they built on the adjacent property. I learned from that experience that Mark and Ben Porter were very detailed and meticulous builders, and they are really good folks! Their building skills and personality are ideally suited for the challenges that lie ahead for building a Passive House Project. My clients, Craig and Ursula Volwiler agreed and felt they would be in good hands trusting Porter and Sons Construction in building their new home.

Mark has been my main point man and has been very receptive and eager to learn about Passive House building strategies, high performance envelope assemblies and the Passive House Energy Standard.

We have been spending much of our time determining the best approach for how the house will be built from an ease of construction and construction sequencing approach, while still striving to meet the requirements for a Passive House. Look for future posts that present a look at the construction technologies we are intending to utilize for the project.

Here's a link to their website: http://www.porterandsonsconstruction.com/

South Elevation Rendering and Project Description

I took about a month but we finished conceptual design and are moving through design development. I thought I would share the first rendering of the project and give a more detailed description of the project.

This barn influenced style home is 2,152 square feet with 3 bedrooms, 2.5 bathrooms, and a small loft office. The design echoes the vernacular architecture of farm buildings and vineyards in the region. The home will be optimized for passive solar gain and views of the Blue Mountains. A wrap around covered deck and porch area will create an outdoor living space that connects inside spaces with outdoors. The owners will have a large garden to grow most of their food and have incorporated a root and wine cellar for winter food storage in the detached garage. Reclaimed exposed structural beams and posts will be used to visually divide the large southern open space that occupies the kitchen, dining and living room. The central dining area will reach two stories, and window seat nooks on both sides of a very small wood stove will be a focal point at the south end of the dining area.

The second floor landing/common space features a vaulted ceiling composed of reclaimed tongue and groove pine, provides for mountains views through large southern windows, and visually connects with the dining space at a centrally located handrail.

Welcome to the Passive House Walla Walla blog! The blog will follow the design and construction of a low energy home that is aiming for Passive House Certification. The intent of the blog is to be an open source of information to individuals interested in learning about our approach to designing and constructing a low energy home.

The project is in the initial conceptual design phase with the intent of breaking ground sometime in the spring of 2010.