Vapor Retarder Two-Thirds Rule

When placing insulation in Portland, Oregon, I rarely use material with a bonded-on vapor retarder (kraft face). I am aware of propaganda favoring cellulose, and raising fear of fiberglass batts, in The Big Burn Video. Proponents of cellulose have dealt with criticism of organic cellulose as inherently less safe than inorganic mineral insulation, and tilt the table too far in the other direction. The video presents ideal cellulose, and fiberglass with no description. I imagine the fiberglass was a least-favorable setting, with air channels (chimney path) the length of flammable kraft facing. A fair comparison would have fiberglass totally filling joist bays, with no kraft facing.

I will never use kraft facing in a wall or in a new-construction ceiling. There I use complete, taped sheathing with polyethylene sheeting designed for the purpose, Swedish Tenoarm. Aside from fire safety concern, I save time and get better fit, in custom-cutting unfaced batts. I also follow the advice of the USA importer of Tenoarm:

http://www.conservationtechnology.com/building_design.html.

I will use kraft batts in an attic floor, to isolate new material from found loose-fill insulation. I use original reasoning in study of dew point data for my location, as reviewed in this posting, with a current update. The commonly-understood two-thirds rule states that a vapor retarder should be to the warm side of two thirds of the applied insulation.

Beginning Thoughts of Math, Carbon Footprint

In effort to show the value of home energy conservation efforts, I have done math for heat transfer, and fuel costs crunched for my city. Now, I want to join the game of declaring benefits as reduction of carbon footprint. An advantage in this is that low, subsidized, cost of heating fuel is divided out. I accept numbers from a recent issue of National Geographic, March 2009, p 67:

Driving: a gallon of gasoline adds 19.6 lb CO2.

One KWh electric use adds 1.5 lb CO2.

100 cf of natural gas emits 12 lb CO2.

I need to back up a few steps, and understand where I am expected to go, with reduction employing such numbers. Start with the EPA Household Emissions Calculator.

Here is my annual carbon footprint, living alone, working hard as a weatherization contractor:

12,438 pounds CO2 in driving 13,400 miles per year.

2,808 pounds CO2 for 239 therms of natural gas in an efficient furnace heating my modest 1000 sf home and productive workplace.

7,063 pounds of CO2 to generate 7663 KWH of electricity per year.

22,309 pounds CO2 before savings efforts volunteered, about 1000 pounds of CO2, through car maintenance and through steadfast recycling.

Numbers correspond fairly well with the National Geographic conversions. I am near the 20,750 per-person US average. I have begun to share my home, and that will push me below the average. The sharing of my home is in fact the most powerful thing I can do.

Better-educated by this study, I am inspired to save a few thousand pounds of CO2 emissions per year. Here are several ways I could save 1000 pounds: Drive less by 8%, fifty gallons, or 1080 miles. Reduce electricity use by 14%. Reduce my use of natural gas for heating, by a harder-to-do 35%, or 85 therms. There is promise in all of these. Only heating reduction through conservation, what I do for others as a contractor, is painless.

I began this writing exercise upon concluding that large effort in a customer's attic of 720 sf, going from R13 to R40, would save fifty therms, the equivalent of using thirty gallons in driving, and about 600 pounds of CO2 averted. It was a small gain, but beyond painless. It is a more than twenty percent annual return on the customer's investment, forever, and further value in more-comfortable living. The customer will still look for harder ways to reduce footprint. The saving corresponds also to that of diligent use of clothes lines in a wet climate; this with no effort.

Free Access to Codes

In a previous post, I expressed my wish that all public regulations important to my safe workmanship, should be available for free online access. I am pleased to find that the National Electric Code, maintained by NFPA, the National Fire Protection Association, can be read online. You only need to register for access. There is no cost. I wish it were word-searchable and printable. If it were pdf, I could readily enlarge for less challenge in reading.

Now, how about building codes?

Sealing Attic Floor Pits

Dropped ceilings in closets are seen in an attic, as floor pits. Photos here, with corrective action, are of a home built in 1953. Attic air is freely admitted to walls the full height of rooms below, amplifying the ceiling-area heat loss or gain, by an order of magnitude. Let's try the math here, on that order of magnitude. Numbers in play are represented by L and W, the dimensions of the ceiling, and H, the below room height. I see that the influence of closet interior walls is debateable where the door is normally closed. Figure the amplified area as 2* (L + W) *H, where L = 46, W = 31 and H = 96. 2* (L + W) *H = 103 sq ft. LW = 9.9 sq ft. The amplification factor is 10.4. If insulating 9.9 sq ft saves $7/ yr, the larger saving is $73/ yr.

 

Carry the argument of an order-of magnitude multiplier a bit further. For this closet, if the door were left open, the area exposed to attic-room temperature difference increases by the interior side-wall area below the drop. The larger amplification factor is 13.5. The smaller amplification factor, (2* (L + W) *H) / LW, is a minimum for home situations. I imagine home situations where the minimum is larger than 10.4. How about a long, deep wall used as a ventilation chase? Ten ft long, a foot deep. The amplification factor for a one-floor 8-ft chase is 17.6. If the chase runs down two floors, 16-ft, the amplification factor is 35.

I argue to my rebates manager, that pit closure is far more important than air sealing opportunities in an attic floor. Pits are often overlooked or are improperly fixed when found. Old insulation may be draped over a pit, merely hiding it, with slight impediment to air flow driven by the temperature gradients. A loose-fill installer will almost never know of the neglect. There are no incentives to pick up that old, dirty insulation to find and fix pits or other problems, in practice. In my area the testing trade, Home Performance, is promoted by a fifty percent of cost rebate for air sealing work if that achieves quite-large drop of infiltration, 300 cfm or more under test conditions. That is absolutely unhelpful here. The problems are not made detectable by blower-door conditions of pull from the attic. A pit doesn't contribute to infiltration.

My closure of the pit employs half-inch drywall pulled up to floor joists, and edge-sealed with spray foam, or better, my flexible grout which I offer for free with easy conditions, as a sample. I prefer GP Densarmor fiberglass-faced drywall, kept as scrap from my closet projects. Screw a length of 2x4 under the drywall for lifting and anchoring. Sandwich the drywall with another 2x4. I shape Densarmor edges with a Shurform plane. Ordinary drywall is too brittle, and paper facing resists trimming of edges.

This relatively simple pit closure took more than an hour of actual performance. With an extra trip it is far more costly to an installer, if not known in advance and rewarded through a contract. If a contract change must be argued or if the worker is somehow detached from responsibility, a proper fix is not mere due diligence. It is unlikely to happen.

This home was like a test lab for pit sealing. A rare opportunity, yet daunting since problems were detected upon bidding. Daunting since more time would be spent in the attic in summertime heat. Daunting since pulling drywall up under floor joists requires more than a bit of cleverness.

There were three more pit areas, one including a dropped ceiling over a bathtub; another a long wall with dead volume associated with a grand fireplace; and another very simple at a dropped ceiling over the home entry. That at the fireplace involved working in extremely cramped overhead, out to an outside wall, and had six hours of actual performance. Multiple visits dealt with rerun of interfering wires. All of these problems were happily hidden, until I pulled up nice-looking insulation.

I challenge Energy Trust of Oregon, and other rebate organizations, to do a better job of serving and protecting Utility consumers. All stuations that invite being overlooked, should be specifically reported by weatherization contractors, to secure diligence rebates. I ask for a new rebate program, where reported pit closure qualifies rebate-times-ten for involved floor area. All diligence rebates should be presented for public examination and learning. This reward approach is consistent with the fact that some pits are large enough that pit walls could be insulated instead of making a difficult but fall-protective cover. The alternative reward of fifty percent of repair cost is of comparable size, and would work if the conflicted tie to reward those invested in Home Performance, were removed. Keeping the tie here is absurd, yet that is the dogged position of Energy Trust of Oregon. Keeping the tie is a grave disservice to homeowners. While I owned a blower door, modestly invested in Home Performance, I NEVER found a problem not more-readily detected by simple observation. I never found a home without a great excess of infiltration, to be dealt with by progressive and obvious measures such as window replacement. Tests taught nothing.

Here is related comment upon feedback to focus on unique and interesting opportunities, and to raise the state of the art in weatherization. At the last Energy Trust Trade Ally meeting I attended, I shouted out that blower door testing for unique purposes should be rewarded directly to the contractor, a token amount of $50, if he offers a report of why and what learned for PUBLIC DISCLOSURE. A family of public reports would raise the state of the art among contractors nationwide, would inform the DIY public, and would sell Home Performance services. We all need to better imagine the situations where blower door and/ or infrared thermography testing profits the homeowner. The situations may be uncommon.

Using Baffles With Attic Batt Insulation

This use of a one-foot length of Durovent baffle material seemed to work. The flimsy foam shape is held against roof sheathing by batt insulation stuffed beneath. Placing the top-course crossing batts goes faster, and I get more insulation at the periphery, when I don't have to worry about blocking vents, of whatever baffle material is deemed acceptable.

Here is a photo album detailing this job, rationalizing use of flimsy Durovent baffles. I have never used cardboard baffles.


In 2016, advise against use of Durovent, too. I have seen expanded polystyrene board  insulation under siding, disintegrated under heat of less than ten years service. I will not guarantee service of EPS. 
 

I now use only strong plywood baffles, reaching all the way to the attic floor and blocked by good 2x4 remnants. Please see a presentation at my web site. Here is another blog post, where plywood baffles were foollishly installed. For the photo at the left, note  concern that plywood roof sheathing should have edge clips over 24" spans. Brittle shingle underlayment may be cut by a plywood edge, causing roofing failure (a hard-to-fix leak). How, now, would one align the plywood edges? This is stated in a September, 2012 update of this post, I have become opposed to deployment of continuous roof vents, especially as soffit-area air inlets, which slot the sheathing and underlayment. I want to rely on underlayment as a second stop against water driven under shingles. What will happen in a reroof, where slots are "lost", and a product like SmartVent no longer covers a tear? Make good use of your soffits, if you can.

Add more on 7/26/2016, from this album :

R30 crossing batts align with tops of baffles 18" tall. Make the baffles from taller scraps if you wish. With this steep roof, place outer R30 batts as 12” lengths. Split a 12” R30 batt to stuff under a baffle. Take care to fit most batts of  consistent 24" x 48" dimension, so that lifted batts someday do not become a jigsaw puzzle. Expect to briefly lift and reset a few regular-sized top-layer batts for safe footing on joist tops for maintenance as in inspecting and cleaning soffit vent screens.


In a national plague of stink bugs, expect frequent need to reach down the tolerant baffles occasionally to vacuum. You could never do that through a cardboard silly-thing 36" tall.

Kneewall Closet Access and Insulation

The light at the floor aims at a difficult insulation opportunity, behind finished knee walls.

Let's see what is behind this crude door.

A conscientious installer of cellulose insulation made a best effort through here, to weatherize the ceiling of the home Living Room. Coverage is a spotty twenty percent, with none in the lee of obstructions.

I will fix this, from a new, better access. Attic Access is what I do, and that involves willingness to cut and crawl through plaster walls.

With a hole in the knee wall, the problem is manageable.

I have improved ceiling insulation to R40, over 80 sq ft, and the accessible areas of the cut knee wall to R15. After rebates, despite access cost, the job cost will be repaid by energy savings, in less than ten years. For the homeowner, it is one more thing to feel good about.

The real-plaster patch need not demand support by a professional plasterer. Block opening edges and reset lath. Repair pre-existing cracks with flexible grout as a nice plus of the weatherization. Prime edges, brushing on Plaster-Weld. Screw-attach expanded-metal lath. The patch area is easily filled in one application of Structolite plaster, struck level with a 4-foot feather-edge if it fits. Here, there was compromise, using other tools to level the patch.

Final finish is with broad application of mud. This will need texture and primer.

Please know that I proceeded to fully insulate the kneewall closet that led me to the ceiling-insulation opportunity, post Kneewall Closet Air Barrier. Know the closet was left in this perilous condition with insulation protected only by sealed-tight house wrap.

Recycling Extruded Polystyrene Foam, (Styrofoam)

This post is edited as of November 7, 2009.

EPS foam blocks (Styrofoam) ARE recyclable, in Portland, Oregon. Recycling, of clean material only, is a service of Pacific Land Clearing, at three of their four locations in metro Portland.

http://www.plcrecycling.com/centers.html

This Bee Newspaper review, tells the story, as of June 4, 2008, with info on what PLC does with the styrofoam. Reported options include a volunteered service of the seasonal Moreland Farmers Market, which brings a weekly collection to PLC.

I find styrofoam stored in attics, often. Stored. Not really doing any good as insulation, where air freely seeps under. I collect material in a 55-gallon drum liner, and when full, make a trip to a PLC location. I want my city to require all recycling centers to accept material, and bring it to PLC. As noted in The Bee, the mindset that styrofoam must go with trash, is hard to undo.

Every city should look for means to consume styrofoam as done by PLC and as described in The Bee.