Super-Insulated Building Envelope

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Author Message David J. Wyatt Senior Member Username: david_j_wyatt_csi_ccs_ccca Post Number: 120 Registered: 07-2005 Posted on Friday, April 10, 2009 - 03:37 pm:    An architect wants me to write an alternate for a super-insulated building envelope, which seems to be generally-accepted terminology for a systems approach to this type of construction. First, the architect understands that this will impose some constraints on his present design and seems not very concerned. Wikipedia provides a brief general description of the work results of such a building system, but it is not sufficient for a complete performance specification. Has anyone out there written such a specification? It seems as though it could be classified in Division 07 or Division 13, with references to Division 03 and 06. This seems as though it could become its own project. The request reminds me of an architect who wanted me to write an alternate to make a project LEED-certified. "But don't spend a lot of time on it," he said. I passively-resisted to the point where he finally dropped the issue. Thanks for any advice you can give. Dave Wyatt Phil Kabza Senior Member Username: phil_kabza Post Number: 383 Registered: 12-2002 Posted on Friday, April 10, 2009 - 06:03 pm:    David, Superinsulated construction emerged in the mid-1970s out of Saskatchewan and New England. The idea was to push envelope insulation levels and air tightness to the point that small, non-conventional heating systems would be adequate for residential use. We worked with R25 walls and R30+ attics, foundation insulation, and continuous vapor barriers and air-to-air heat exchangers for fresh air. The houses worked quite well; their annual fuel bills were insignificant, even in regions with poor solar fractions. Commercial buildings being less skin-load dominated and more internal load (cooling) dominated don't lend themselves to superinsulation, but they do benefit from airtight construction and the elimination of thermal discontinuities such as steel framing exposed to the exterior and the other goodies that design architects love to do. That said, there's little in a "superinsulated" building that wouldn't be addressed in a conventional specification. You might increase insulation levels somewhat, but the thickness of insulation is largely a drawing issue. Some superinsulated house builders in the 70s built double stud wall exteriors; I don't think there was ever a convincing payback for that extreme an insulation level. But added insulation may have an impact on the building sections and the floor plan. The most important thing about superinsulation is care in the installation. We did our own vapor barrier and insulation work because we didn't trust anyone else to do it right. You'd best do a thermal and moisture model of the wall and roof construction to make sure it doesn't rain condensation somewhere in the middle of the wall cavity. HVAC engineer must address building fresh air on the basis of near-zero envelope air infiltration; the HVAC system must be redesigned. And put in a good kitchen exhaust vent if you plan to cook broccoli. Lisa Goodwin Robbins, RA, CCS, LEED ap Senior Member Username: lgoodrob Post Number: 17 Registered: 08-2004 Posted on Monday, April 13, 2009 - 10:39 am:    David, I like your passive-resistance on a previous project. With that type of thinking, ask your Architect to send wall sections and details for the superinsulation. Obviously this isn't just a spec item. The Architect needs to think about where this additional insulation will go and how it will affect the overall envelope construction. And remind the Architect to have a discussion with the HVAC engineer too. Anne Whitacre, FCSI CCS Senior Member Username: awhitacre Post Number: 870 Registered: 07-2002 Posted on Monday, April 13, 2009 - 01:26 pm:    if its possible, and within the budget, you might consider ongoing inspection of the installation. You'll want to see correct application of vapor barriers; fully sealed seams in the insulation; calking properly applied at penetrations (electrical boxes, light fixtures) and insulation under the stud track. I've done "super-sealed" installations for sound reduction, (not thermal reduction) and we've called for ongoing inspection as the assemblies were installed, since once its finished, you can't correct any problems without tearing down the wall. as Phil indicates, its a combination of products and installation technique. pose that idea to your client and see if they are willing to pay for verification of the design -- that should indicate how serious they are about this process. Randy Cox Senior Member Username: randy_cox Post Number: 57 Registered: 04-2004 Posted on Monday, April 13, 2009 - 05:57 pm:    The other thing for the architect and the mechanical engineer to discuss is air infiltration. Most buildings don't have this problem, but super insulated buildings are increasingly air-tight, with resultant low air infiltration rates. If that is the case, someone needs to provide for this infiltration as part of the building design. Some windows can be ordered with a trickle vent, Panasonic makes a passive vent that allows outside air into the building in controlled locations, or the mech engineers can design something. It sounds crazy to deliberately create holes in a super insulated building, but fresh air is essential. Jo Drummond Senior Member Username: jo_drummond_fcsi Post Number: 30 Registered: 06-2007 Posted on Wednesday, April 15, 2009 - 01:26 pm:    My house is well insulated, very tight and sound infiltration-resistant. Double glazed Pella windows. The other day, I opened an interior door and another interior door which was "pushed to" against the strike, 25 feet and 2 corners away, closed. I have to air the house out frequently to provide fresh air. As Randy mentioned, fresh air is essential. Ron Beard CCS Senior Member Username: rm_beard_ccs Post Number: 301 Registered: 10-2002 Posted on Wednesday, April 15, 2009 - 01:41 pm:    How to tell when your house is really air-tight: .....when you open the front door real fast and the toilet flushes. John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1039 Registered: 03-2002 Posted on Wednesday, April 15, 2009 - 03:01 pm:    Ron, That only works when the front door swings in. Otherwise, well .... Steven Bruneel, AIA, CSI-CDT, LEED-AP Senior Member Username: redseca2 Post Number: 172 Registered: 12-2006 Posted on Wednesday, April 15, 2009 - 05:39 pm:    Quote from Ron B: How to tell when your house is really air-tight: .....when you open the front door real fast and the toilet flushes. I confess to being part of a black-ops team (project team) trying to get an occupancy permit for a large national historic landmark hotel restoration many years ago. One outstanding item was the force needed to open the massive cast bronze entry doors that were part of the "historic fabric of the structure". With the best new hinges in the world we couldn't get under the 15-pound ADA force limit. The problem was pressure differentials (along with 3000 pound door leafs). After repeated failures, for the final test, the city inspector hooked his force meter (fish scale) to the door to try one last time. When he started to pull, one of the GC's men keyed his walkie-talkie and workmen stationed around the perimeter of the building (one square city block)at the other entrances immediately opened their doors. The inspector opened the testdoor, looked puzzled for a moment as he checked the scale, then smiled and told that we had passed. Lisa Goodwin Robbins, RA, CCS, LEED ap Senior Member Username: lgoodrob Post Number: 18 Registered: 08-2004 Posted on Thursday, April 16, 2009 - 09:06 am:    I love that story! Wayne Yancey Senior Member Username: wayne_yancey Post Number: 193 Registered: 01-2008 Posted on Thursday, April 16, 2009 - 01:33 pm:    Check out this article by Josesph W. Lstiburek, Ph.D http://www.buildingscience.com/documents/insights/bsi-018-westford-house?full_view=1 Lynn Javoroski CSI CCS LEEDŽ AP SCIP Affiliate Senior Member Username: lynn_javoroski Post Number: 864 Registered: 07-2002 Posted on Thursday, April 16, 2009 - 03:05 pm:    What I appreciated about the story is the use of the fish scale. Back in the 90's when I was doing ADA surveys, that's what we used to record all sorts of forces required, from door opening to toilet flushing. We thought we were so clever to have thought to use a fish scale...(tricked out with a shoe lace for when the handle needed to have a loop). Jonathan Miller, FCSI, SCIP Intermediate Member Username: jmma_specs Post Number: 4 Registered: 04-2009 Posted on Sunday, April 26, 2009 - 10:22 am:    When one thermally encloses and significantly reduces air-filtration in the envelope... one should remember to think of it as placing a plastic bag tightly over your head. One needs a fresh-air source and a method of removing the pollutants trapped in the bag with you. The only items missing from this super-insulated envelope discussion are: - Addressing the heat/cooling exchange needed between exhaust air and the filtered fresh-air supply. - Directly exhausting heat sources like ovens, stoves, hot-water pipes, etc. and capturing/storing/reusing the heat when needed. - Providing ducted/piped make-up air to all combustion sources like fireplaces, wood-stoves, furnaces, and appliances with pilot lights. - Capturing/controlling moisture from point sources like showers, baths, clothes dryers, and cooking to prevent interior humidity supersaturation. Not addressing these items can result in mold, bacterial blooms, build-up of material off-gassing chemicals and dust (with mites)... each of which stresses the inhabitants immune system making them susceptible to illness... sick building syndrome. Well... there is more complexity to this depending on the design but the benefits to a super-insulated & air-tight envelope are significant when done correctly.... and potentially harmful when not done right. Hmmmm.... Perhaps there IS value to competent professional expertise after all ! Now if only someone would pay professionals well to do the complex but right thing.... and the contractors build it correctly.