My most-recent customer, May 2017, wanted storage space in a truss attic, where the home has no basement, and half of the garage is converted to needed living space.
Photos are drawn from a corresponding Google Photos album .
This home had the usual drywall plunker 18" OSB-skirted access hole. There was no safe landing to move between trusses, from the blunt OSB edge. To move, one had to angle feet to opposing angled truss elements, in long steps across trusses.
About 20% of the plunker area was bare about the precariously-stapled R38 batt, and this really mattered to actual insulation value:
1/(Reff + 3) = .8/41 + .2/3
Reff = 8.6.
A batt on a plunker is ridiculous, dangerous, and often temporary. I continue to do good service in safety of attic access, contending for better building codes , and imagining and building very-simple factory-built hatches that cost no more than the plunker-hole. I prefer to install a wonderful attic ladder, then with every safety feature I can imagine.
I am the first person up here since house construction in 2004, and the home owner has cause to trust that I can make this space useful. There is 15" of loose-fill insulation seemingly almost the required R38. HVAC ducts are strapped-up, for the insulation blow, and are very much in the way.
Good lighting and safe access via ladder is accomplished early in a job. A pretty Fakro LTK 22/47 insulated attic ladder is rigidly mounted with the beginning of 18" box beams at both sides. Outer beam faces are 16" rips of 3/4" plywood. There is a step-off well 9" up from the ceiling.
Preview the accomplished attic improvement equally for usefulness, and energy conservation. Up 18.6" from ceiling drywall, there is very much useful space. New and more-efficient HVAC ducts are almost entirely buried, for their safety and better insulation value, without compromise of floor insulation value. Effective R value of the entire attic floor is now better than R49. Four 900 lumens Sylvania LED disk downlights brightly illuminate the safe, clean, useful attic.
Finished features include a strong, level shelf over a loft cathedral ceiling, making that space useful and safe. Find and exploit every advantage for walking between truss elements. The shelf and flooring constitute a large box beam that restrains this gable wall and adjacent trusses against roll-over in a tornado.
Braces set for alignments during construction are not intended to guard against roll-over of trusses and great tragedy in a tornado. Useful new braces are not in the way of access.
Diagonal bracing against truss rollover is by example of MiTek, USA, MII-GE90-001 .
I have provided the safe, useful storage space that the home owner needed.
Now step back to the work in progress, with demonstration that easily-achieved energy savings are the best reason for the attic conversion. We all can and must afford the best energy efficiencies achievable in our lives. Where one is able to find an honest craftsman or is able to follow freely-offered example, an investment in a durable sixty years and more, chunk of energy independence in our homes, is a significant increment of personal wealth.
This home had complex found conditions. 43% of floor area had askew thick batts, 51% was between trusses with poured loose-fill fiberglass, and 6% was with thermal shorting of truss framing. Two loft cathedral ceilings add elegance to second-floor rooms without the compromise of roof integrity and access limitations of common cathedral construction. Loft cathedrals are easy with truss design but seem to need evolution for improved weatherization.
This collage is of found conditions of R31 and R38 batts of the West loft cathedral.
This collage is of found conditions of R31 batts of the East loft cathedral, and of repair underway under tight hostile conditions with nasty roof nails and danger of falling through drywall. Temporary wood-strip supports and access via a new storage table over the loft were important to holding a good attitude for repairs completed in a half day.
Among the R38 batts of the West loft cathedral, see awful consequence of poor batt placement and failure to block thermal shorts at framing. With 50% contact, the weighted average insulation level is only R3.
1/(Reff + 3) = fjoists/(Rjoists +3) + fbatts in contact/(Rbatts +3) + fbare/3
1/(Reff + 3) = 0.06/6.3 + .47/41 + .47/3
Reff = 2.6
Find the same result, ignoring joist thermal shorts.
1/(Reff + 3) = .5/3 + .5/41
Reff = 2.6
Bare areas dominate the math, overwhelming significance of the framing thermal shorts. Therefore, apply the formula above for the entire attic floor, with glib allowance for joist thermal shorting, whether or not there may be insulation "atop" conductive complex truss framing. Joist thermal shorts remain important in most cathedral ceilings, where a rare reader might amend the math with larger value of Rjoists . Consistent math is achieved by use of an OpenOfficeCalc spreadsheet. Please find that spreadsheet for the first computed result, with 2x4 @24 joists, fbare=, 0, R19, at Google Drive .
The table above applies in general, for a floor with a single layer of batts, or a floor with loose fill insulation. In the table, 6% of floor area is treated as 2x4 joist thermal shorts, R = 3.3. Where bare areas strongly dominate the math, the treatment of thermal shorts is of no consequence. My immediate self interest in the table treats the question whether my rebates organization, Energy Trust Of Oregon , will grant my customer an insulation rebate. Rebate offers are the only offered encouragement of actions by my customers. A rebate is offered only where found insulation has value less than R12.
In another edit of the example spreadsheet , imagine compromise of insulation in a 2x10@24 cathedral ceiling with R19 batts 50% bypassed. Find Reff = 2.3. All insulation that doesn't fill enclosing space has questionable value. Try out your own favorite worry. I wait with skepticism, to study methods in new USDOE Home Energy Score software, hoping that penalties will cause end of ruinous venting with deliberate under-fill of cathedral ceilings.
Bare areas in an attic add up fast. In most homes, expect 5% of the floor area bare, at carelessly insulated eaves. See attic walls in the photo above, with loft cathedrals at left and right, insulation uselessly bridging the wall framing.Those uninsulated attic walls at interior sides of loft cathedrals alone are more than 10% of floor area, and treatment of those walls can not be separated from overall attic improvement.
Bare areas under floor insulation are another 10% of the attic floor, mainly in awful result of blindly stuffing oversize batts before setting drywall, at the loft cathedrals.
Carelessness is the cause of energy waste in this home, in defiance of building codes in effect at home construction in 2004. And, until I showed up to imagine a useful attic, all seemed well. Any inspector or other weatherization contractor would have seen a good-looking attic with no corrections needed. The attic is a dangerous place. Stay out!
I move further beyond the R12 threshold for a rebate, at fbare = 0.15 (see table above), if a bare area equivalent 5% of the attic floor area, is added. This is proposed as a standard allowance to encourage sealing of attic floors.
Payback Math, Insulation Improved Effective Insulation Value Starting R10, Ending R49:
Apply Insulation Math that gives understandable dollar values then easily scaled for a home, heating means and climate, that matters to you. Basis math is for a home with 88%-efficient natural gas heating, 4400 heating degree days, energy cost $2 per therm.
Annual Cost of Heat = (.00002 * 4400 * 24 / .88) * (Area/R) = 2.4* (Area/R)
Let Area = 1200 sf, and R = 1/U = Reff +3.
For the attic floor, the first-year saving of heating cost is $222 - 55 = $167.
Attic walls, the exposed ends of loft cathedrals are another 100 sf, improved from less than R4, to R30. Here the first-year saving of heating cost is $34 - 7 = $27.
Total first-year savings are $194.
In considering savings on into the future, one must account for the rising cost of easy energy through scarcity. Apply Perpetuity Math . The present value of an investment yielding $194 in the first year and continuing indefinitely, is more than $8500, first-year times 44, with a twenty-year outlook and true cost of energy rising at 10% per year. My invoice of $6100 was a bearable cost for wonderful new storage space. All of the cost, including a bit of excess for the storage, is in fact a very profitable investment.
Rebates As Incentive
Once again a rebate application is in process with Energy Trust Of Oregon, for my work. I have asked $296 for the floor insulation, and $30 for the attic wall insulation. $326 total, 5% of job cost. This is a small return of the home owners' thirteen years of contribution to Oregon's Public Purpose fund, a 3% tax upon natural gas and electricity bills.
As I understand it, rebates in fact are not needed as incentives. We just want to know priority of the things-to-do, to be able to afford the work and to trust that it is done honestly, to endure. Incentives are not working to drive weatherization of existing homes, where Energy Trust will promote fewer than 1000 attic insulation improvements in 2017.
Despite need to multiply its productivity times fifty, or go out of business, Energy Trust definitely wills that the described attic would have been left alone. I am commanded in Specifications , that:
IN 1.13—Determination of Existing R-Values
The total R-Value for a floor or an attic shall be calculated based on the depth of the insulation (in inches) multiplied by the recognized R-Value per inch of the insulation material.
15" times R2.2 per inch for loose-fill, is R33. Rebate Denied. And that is the end of a conversation. My customer may receive the asked rebate, but Energy Trust will learn nothing, and will not contact me, for its benefit or as a disciplinary action. Meantime there is some strange complexity offered in Specifications Appendix A:
APPENDIX A: WEIGHTED ATTIC R-VALUE TABLES
These tables shall be used to determine the weighted R-Value of a single attic space with varying levels of insulation. These figures are determined by using a weighted average R-Value calculation without including framing assembly U-Values:
U-Value (U) = 1 ÷ R-Value
Area (A) = area in sq. ft.
Weighted R-Value = 1 ÷ [(U1A1 + U2A2) ÷ (A1 + A2)]
In cases where the existing insulation level is R-0, an R-Value of R-1 is used in its place to determine weighted R-Value.
This math is of course in error, where convection heat transfer coefficients and resistance to heat conduction through surface materials add up always to nearly 3. A low number for convection and surface resistances is a bad idea, for it leads to over-estimate of savings achieved where there was little or no insulation at found conditions. A modestly high value, 3, gives desired under-estimate of savings achieved. Add 3 to all insulation effective R-values and then invert the result, to obtain U-Values. Please see discussion of such concerns at Wikipedia , and ColoradoEnergy.org . Compare savings from insulating a 1200 sf attic from no insulation to R49, assigning 1 or 3 as found effective R-value, 1/U, U = 1 or U = 1/3
$2.4*1200*(1 or 1/3) = $2880 or $960, at found conditions.
$2.4*1200/50 = $58 at R49.
No one would think to mislead, in offering that another $2000 per year is saved. The only math offered by Energy Trust for mixes of insulation then is incorrect. No correspondence to dollar savings is suggested. There are internet links at Fine HomeBuilding and elsewhere to USDOE math of payback calculation, now broken. The missing information handicaps decision making for weatherization. In particular, the treatment of out-of-contact insulation is not addressed, leaving some to think contact doesn't matter. Surely the correct treatment of insulation out of contact and permissive of air bypass driven by heat input and rejection, is to fully discount any value of the insulation.
Tragedy In A Typical 1970s Town Home
Many 1970s homes are dominated by cathedral ceilings that have no actual insulation value. This is the first home I will address with USDOE Home Energy Assessment software. What direction will I find for this condition in 2x10@24 ceilings? I have seen clues that the insulation will not be counted.
The exterior walls of 2x4@16 construction have insulation nearly as poor.This small area at a removed air conditioner, fixed with removal of exterior sheathing, may be the model, unaffordable repair, saving $6 per year at cost of $600.
It may be evident that this home has a personal connection to me. Bitterness about the cathedral ceiling and wall insulation seemingly not treatable, motivated two of the ten proposals for 2018 revision of the International Energy Conservation Code, at Louisville , that I offered and personally defended at great cost. Please find a February 2016 summary of my correspondence with IECC , where I responded at the best of my ability to all editing suggestions. At this code cycle IECC newly offered an online submittal process, cdpAccess, and supported my telephone and email newbie needs. At the conference, I relied on my own printing of proposals vs. existing 2015 code, as in this abbreviated printing for followup discussion with NAIMA. I sorted through a tall stack of paper-printed code and revision in competition with experienced professionals using laptop computers, trying to follow all proceedings that mattered to me.
My proposal 11881 offered:
R402.2.1 Over-fill of insulation. Wherever possible, insulation shall be confined on all six sides. Insulation fill shall be complete and without voids that could allow air bypass of the insulation. Overfill of insulation shall be required to achieve complete insulation fill. In addition to installation methods that prevent voids within the insulation, the methods shall prevent the presence of air spaces between a barrier film such as the kraft facing of a batt or the containment mesh for blown cellulose, and hard wall coverings such as drywall.
At the eaves of an attic, insulation installation methods shall achieve as much insulation R-value as possible toward exterior wall headers. The eaves shall be packed tight with insulation and overfilled except the resulting R-value at these locations shall not be required to exceed R-value required for the adjacent ceiling.
My proposal 11882 offered:
R402.2.2 (N1102.2.2) Ceilings without attic spaces. Such spaces, commonly called cathedral ceilings, have depth limited to that of practical roof framing. They are to be crafted with all of the seriousness of any other conditioned attic, concerned for roof rot in insulation at temperature below the dew point where moist air may pass. A solution for insulation, in well-applied closed-cell foam, must be seen as risky in the event of roofing failure. These spaces shall not be violated by can lights or provisions for attic ventilation and foolish wish to cool composition shingles. There shall be no compromise of required insulation value.
With these provisions, any persisting construction of cathedral ceilings shall be with acceptance composition shingle roofing is not allowed.
My proposal 11859 offered:
R402.2.3 Eave baffle and insulation provisions. Where needed at soffit vents, a solid baffle durable for service of at least sixty years, shall hold insulation at bay, while allowing a stable maximum amount of insulation to be placed. The airflow resistance of each baffled path shall be less than that of its screened vent. Soffit vent paths installed as pre-made "bird block" and designed for placement at every frame bay, shall be placed in every frame bay.
For new home construction and in tear-down remodels, eave baffles and at least all eave-edge ceiling insulation shall be placed before installation of ceiling-edge drywall, if needed to assure thorough insulation, in areas that become inaccessible. Where an attic eave extends to a cathedral ceiling or other roof-over-conditioned spaces, do not employ the insulated cathedral ceiling cavity as passage to admit air for attic venting.
Altogether, these three proposals dealt with my concerns of deficient and irreparable poor construction of the 1970s depicted in the town home photos above.
All ten of my proposals were unanimously disapproved, sometimes with enmity and sometimes with sympathy expressed by other conference attendees. It was awful. Seeking solace from ICC long after, I was chided for not doubling my investment in another try at the final hearings in Kansas City. My goal instead is to develop alliances for another try in submissions for 2021 IECC. Alliances are needed to combat a little army of obstructors seasonally hired to work the hearings, by the National Association Of Home Builders, aiming to squirrel every possible nickel to pockets of big-time builders. I especially need to find a working relationship with NAIMA , the successful obstructor of the batt-overfill proposal. NAIMA must admit for example, that R13 batts are grandly inappropriate in 2x4 exterior walls, never being 3.5" thick as-placed, and possibly of no value.
Please see that math is integral to my contributions for USA responsibility to conserve energy now wasted in our generally-shoddy homes. Please see that regulation in building codes applies only to new homes and major renovation. Energy conservation is not regulated thereafter.
Note to Self: Anticipate a review in Summer 2017, of consequences of 2018 IECC changes approved, by US Department Of Energy. The report may be like that issued for 2015 changes, in August 2014, which did not reveal any useful math.
Issued by Battelle Pacific Northwest National Laboratory, Richland, WA.