Thoughts on the Engineering Industry

A blog covering engineering, technology and business topics

High Performance Energy Saving Design for the Karuna House – Wall System

Passive House Green Home Building Tips: Karuna House Wall Assembly

Hello everyone.  I hope your weekend went well.  Everything is picking up for me again – my day job and school included.  Not in a stressful way though; it feels good to be doing some productive stuff again.  Today, I want share the second part of my series of post describing the design of the Karuna House and the topic this time around will be the wall system.

As stated in the article, the main issues in designing the wall were moisture, heat and air control.  Along with that, this design added the other standard of being able to release moisture once it entered the system as well.  With that in mind, the main goal of the wall design was to create a building envelope that was air tight, water tight, vapor permeable and super insulated.  On the inside of the wall, standard natural lime coating and dry wall were used for interior design purposes.  Beneath that, a stud frame of engineered wood members was built to support the wall structure and was insulated with high density cellulose.   The high density cellulose consisted of recycled newspaper and naturally buffered against moisture which improved the walls durability.  After that, there was the air barrier which prevented air from flowing through the wall and allowed the insulation to perform at a much higher level.  The air barrier was created using plywood coated with vapor permeable liquid applied membrane.  After that level, a frame of Z Joists with foil faced Polyiso Foam was placed over that.  This element was the critical part of the design in regards to performance and durability.  The final element was the rain screen system made out of cedar siding placed 1 inch off of the Polyiso Foam.  Window frames were sealed using Joint Seam Filler and Fast Flash around the window structure.  Details aren’t provided about door frames but it would be a reasonable assumption that they did the same thing there as well.

In my opinion, the design of the wall framing system isn’t as unique as the foundation system.  It has been standard practice for a while to use foam insulation and air barriers.  The same goes for the window sealant process.  However, the attention to detail in what to use and how to apply it is still a good take away for building design in the future.

What is your opinion on the wall frame system?  Is there any improvement they could have made that would have increased energy efficiency?  Thanks for your time and have a good week! 🙂

Source:

Hammer and Hand, “The Karuna House: Wall Assembly”, http://goo.gl/sHU7kv
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