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A New Norris House: Phase IV

Live-In Evaluation and Monitoring of a design/build effort

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    The Wall Assembly

    newnorrishouse Mar 29 '12 4

    The New Norris House wall assembly utilizes advanced framing techniques and a rainscreen wall construction.  Constructed of Atlantic White Cedar (AWC), the cladding of the house uses natural materials much like those found on the original Norris cottages of the 1930‘s.  Atlantic White Cedar has a natural weather resistance and is a native material to this region.

    In conventional wall design, a single barrier building skin acts as a “all-in-one” layer to keep out rain, retain conditioned air, and to resist the forces of wind & air pressure.  The pressure differential created by a conventional wall design is a major cause of moisture infiltration. A rainscreen, or pressure equalized system, uses 3 layers, a vented exterior cladding, an air space and a moisture barrier.  Initially, water is deflected from the wall construction by the cladding. All moisture remaining is drained vertically and/or evaporated by the movement of air within the air space.

    Specifically in The New Norris House, the batons that create the air space were canted to increase water drainage from behind the AWC cladding.  Also, a bug screen that will prevent the regional dirt dobber from nesting and damaging the wall construction adds a layer of moisture protection during times of precipitation.  The AWC was finished with Cabot’s Bleaching Oil.

    The structural framing of the New Norris House wall assembly was built using 2x6 wood framed walls rather than conventional 2x4 framing methods.  Using 2x6 studs at 24” on-center, this construction method resulted in a 17% reduction in lumber thus a 17% increase in insulation.  Rigid insulation was also added to the exterior of the wood framing, behind the weather barrier, to reduce the effects of thermal bridging.

    If you are interested in learning more about rainscreens in residential construction here are a few links to get you started.

    an article on rainscreens: 
    http://www.residentialarchitect.com/products/screen-shot1.aspx

    and a more detailed report from DOE’s Building America specifically for houses in Mixed Humid Climates:
    http://www.nrel.gov/docs/fy05osti/38448.pdf

     

     
    • 4 Comments

    • archaalto
      Mar 30, 12 10:57 am

      i'm a bit perplexed on why there isn't an additional layer of vertical battens behind the horizontal ones in the rain-screen wall assembly.  wouldn't you need that continuous vertical air space in order for the ventilated facade to evaporate the moisture more effectively?  As it is currently detailed, any moisture that gets behind the vertical cladding might sit directly on the horizontal battens and against the cladding and wall sheathing.  can you offer any additional insight into the variation from a true ventilated facade assembly?  are the battens pressure treated or waterproofed in any way?

      Bl@zer
      Jan 18, 13 11:21 am

      The horizontal battens are canted in order to prevent most of the moisture from pooling on them. The battens are not pressure treated as they are not in a condition where they would be saturated with water such as when a conventional fence post would need to be pressure treated.

      In this rainscreen system the Atlantic White Cedar planks have a reveal to encourage airflow horizontally as well as vertically between the battens. A bug screen was applied to prevent insects and birds from nesting.

       

      Some rainscreen systems that rely on a continuous vertical stack of ventilation usually involves a sealed cladding system with ventilation only at the top and bottom. This is not always necessary with a system such as this one used.

      snook_dude
      Jan 19, 13 8:50 am

      archaalto, I'm thinking the same thing.  I wouldn't be worried about the wood it were completely saturated. It is the in between condition where wood is wet and then dry where it tends  to rot.  I'm also wondering about that insect screen.  What are  you using.  Seems like the vertical joints between butting joints would present a difficult  situation when wanting to make something bug tight. 

      jedisalf
      Aug 12, 13 10:30 am

      Not sure if you'll come back to answer this but, I'm wondering about the steel canopy.

       

      What gauge is it?, and how was fastened to the wall? Just with some screws or any special detail?

       

      And also wonder about the rainscreen, like the previous posters, have you guys had any water issues at all?, Not sure about those "canted" 2x2s.

       

      Thanks.

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About this Blog

The New Norris House is a design/build effort from the University of Tennessee's College of Architecture and Design. Began in 2009, the home was designed and built by UT students in collaboration with Clayton Homes. The built project is now complete and the final phase of the project has begun. A team of 4 people (2 living in the home, and 2 graduate researchers) will rigorously document the experience via qualitative assessments and quantitative measurements, posting results to this blog.

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