Where Failed Flex Ducts in a Crawl Space Were a Magnet to Mice and Rats

This is what happens when R19 kraft-faced batts are stapled to floor sheathing, in a crawl space with framing 4x8@48, so hard to insulate. Twine everywhere just densified the jungle. It was much worse before a couple of rounds, carting away fallen-down batts; really ugly.

Many generations of mice thrived atop the kraft facing and in falling-down caverns.

Half of the batts did not share this decrepitude, sadder then to pull them down for disposal.

About 1200 gallons of compacted batts were sent off to an Eastern Oregon landfill, via this transfer station and rail cars. This is one carload of 250 gallons, a crime, but nothing compared to a mountain of plastic foam that should have had an alternative use.

HVAC ducting came into view, this an awfully-leaky 14" return line. All other ducts were Thermaflex flex, far more to be hated, as probably the major cause of the vermin infestation, the magnets of the post title.

The flex ducts were to be hated for their thoughtless construction. Here a duct is partially detached where it stressfully ducked under a water pipe.

In imagining how to craft vermin-proof new crawl space insulation, consider a romex lead to a living room floor outlet. A competitor suggested  spray foam, nicely ruled out by the wiring obstruction. At about this time I would confront a ruined very-expensive home in a  sad bid visit, uninhabitable due to stink of foam, white hardness coating even the ground.

Horrible decrepitude of the flex ducts was not easily seen. A Northwest corner of the crawl space, least accessible, was littered with rat traps. Why?

Where my discoveries began in Mid-July, 2015, my mandate was just to fix the ruined insulation. I spent part of a day pulling down batts. Then I brought lumber and insulation, to try out a method that had been on-my-mind for years. Here it is:

And with adjusted attitude and method, it works. But, what of interfering ducts? I'm told I must cope with them. I have impending family travel, and a Summer of air conditioning is wanted. I will return, and will find workable paths, in Early-October.

It is late-September, and I will attack the ducts, not really authorized. This is the near duct I had crushed, thought to be attached OK. The liner has a leak, but there is much worse. See the detached spring coils? All Thermaflex ducts in this home are of an early, brittle polyethylene formula. Wires are detached. There are associated liner rips, everywhere.

I expected decrepitude at the thoughtless runaround of laundry water pipes. Curse that damned "duct tape!"

See lots of leakage in the steel piping. See a large separation in the plastic liner, that had been hidden but not blocked, by insulation lining.

See more detached wire, and holes everywhere, inside the flex duct.

Everywhere, is not much exaggeration.

A D-box is a hydraulic monster, itself with usually-leaky attachments.

Incredible.

And, Thermaflex will poo poo, chemistry from mice somehow caused this.

This was the main entry to ducting by rats and mice, then having access to the house interior. The foulness of the liner is evident. Yet a pest abatement contractor spliced in an oversize aluminum flexible duct as the sufficient cure years ago.

Within the insulation lining, not before explored, I found this. The stick was within the air path. With the report I found immense home owner gratitude that I had insisted on demolition and re-imagined ducts.

Crude D-Box tab-in collars can not be sealed.

An insulation-lined turning box replaces the D-box. Use springy lumber to gently find alignment.

A found strap is useful, the rest of the demolished D-box is recycling.

A 16-12-12 wye was an obvious need in this alternative to ridiculous job-hacked D-boxes. Aligning it for clearance of a nearby post is challenging. Begin to see thick flexible grout coating inside all unlined steel fittings, to isolate them somewhat from temperature cycles of carried air. If the steel does not fully swing with air temperature, it has important reduction of thermal mass. Most of the volume in flexible grout is insulative ceramic microballoons.

In a chosen wye orientation, bring on insulating wrap, and secure fittings with screws and UL181 Foilmastic tape.

Some of the weight of steel components is borne by cantilever from the turning box and furnace. Most weight is carried by taut wires at joining pieces. The wires attach to eye bolts in the sreel fittings and to eye screws in the beams above. The ample reserves of insulation jackets are rolled into place as duct assemblies are completed.

In advance of each joining, pull on ample lengths of insulation jacket. Jacket should fully cover all steel and insulation.

Work now with the left-side 12" branch of the 16-12-12 wye. There is a quick 6" wye take-off to a register.

Note the excess liner lengths needed to contain all steel, insulated, out of sight.

Please rely on this diagram of the as-built ducts, to locate the work in following photos.

This attachment to a 12-12-6 wye is with necessary change of direction. Pull quite a bit of tension to limit flow resistance. Call the axial taping strain relief.

Here is finished appearance at the 12-12-6 wye, in a high-traffic area. Interleaving insulation and wrap from two directions can be bumpy.

This is the previously-hated low Northwest corner of the crawl space, close up. Leaving at end of an October day, the furnace is back on and all but two registers are served.

Back in the Northwest corner, for some clear-headed, intense duct construction.

Ducts all done, but to rework a branch warming the kitchen. I will leave some of this now-dirty OSB, though I don't expect ever to return.

Here is the Northwest corner at a distance, now not foreign or hated. I see the rocky dirt as dry. I will not bother to pull up ill-fitting black visqueen, over the rocks and concrete piers.

Survey the completed ducting, starting at the furnace. Yes, there is a rat trap down there, never to be needed again, soon to be gone and forgotten. Everywhere there is smoothness overhead, and I have been under there in the duct-running.

North wall alley. Just duck under, to get past the furnace.

The 16-12-12 wye at the furnace nicely split about a post. All weight is carried by duct steel fittings with topside eye bolts, tied by wires to the beams above.

The 12" branch toward the kitchen is pulled over vent piping, off the ground, without much flow resistance at a formation to oval.

The house had a single 7" register for the kitchen, laundry and a little bathroom. Sadly resigned that can't be improved, minimize resistance to the 7" register, new, firmed-up. 8" flex duct transitions through a 7" reducer.

Kitchen HVAC duct finally done. In the distance, I will now finish an obstructing 6" duct from the kitchen grill and fan. Overhead see another approach to hard-covered vermin-proof crawl space insulation using rips of OSB.

A determined recycler, I took apart ducts belatedly hauled from the job, too dirty and bulky for hauling with bagged insulation trash. Recycle all metal, including spring coils chopped to about 12" lengths.  Take a pause. Send that rat ridden end above for examination by Thermaflex in South Carolina.

Thermaflex was nice, accepting a length of the brittle liner for examination at my cost, against accusation failure is general; a cause of mouse and rat access, not a symptom, surely this not the only instance. To my shock and dismay, they would disagree with me, blaming mice as cause of embrittlement. And, they offered no comment whether current production is with better material.

Sharing this blog post then with Thermaflex, I studied their product claims. Theirs are guaranteed for ten years, said to be better than with competitors .These had "served" perhaps 25 years. What are we to expect past-warranty? Have materials improved in current production? We need to know these things. 

Let's have some discussion here. What have others found? Will a manufacturer speak up about materials evolution?

I suggest to Thermaflex that I am worthy as a commenter, for teaching good flex duct installation practices. May we talk about this, too?

Working With Cotton Insulation Batts

This post is edited and reissued as:

https://energyconservationhowto.blogspot.com/2026/02/a-deep-energy-retrofit-fall-of-2013.html   

Please go there.

Better, find all posts discussing cotton batt insulation:

https://energyconservationhowto.blogspot.com/search?q=cotton   

This is the superseded post, not deleted.

Out of necessity for a customer, I have gained lessons in the usefulness of UltraTouch cotton batts in residential weatherization. Here is a sharing of those lessons.

The owner of the reported home aimed to be best green, in needful improvement of insulation, in Fall, 2008. Then, and now, UltraTouch denim batts by Bonded Logic, Inc., offers

impressive claims.

UltraTouch™ Denim Insulation is the successful combination of 35 years of insulation experience and a revolutionary patented manufacturing process that has created a superior and safe product.

UltraTouch is made from high-quality natural fibers. These fibers contain inherent qualities that provide for extremely effective sound absorption and maximum thermal performance. UltraTouch has No Fiberglass Itch and is easy to handle and work with. UltraTouch contains no chemical irritants and requires no warning labels compared to other traditional products. There are no VOC concerns when using UltraTouch, as it is safe for you and the environment.

UltraTouch is also a Class-A Building Product and meets the highest ASTM testing standards for fire and smoke ratings, fungi resistance and corrosiveness. UltraTouch™ Denim Insulation contains 80% post-consumer recycled natural fibers making it an ideal choice for anyone looking to use a high quality sustainable building material.

UltraTouch makes installation user-friendly. The inclusion of perforated batts allows for quick and easy off-size cavity installation. Simply measure, tear, fit and you're done!.

Many bags of UltraTouch R30 in size 23"x48" were purchased, for placement in the crawl space, by a hired top-notch weatherization  contractor, and for the attic, to be placed by the home owner. Things did not go well, with more than $8000 paid to the contractor, and more money tied up in mis-applied  or stockpiled cotton batts, by the home owner. All for little, if any, saving of energy. The home owner was responsible for misunderstanding how to insulate an attic, but was misled by the bad example of the contractor's work in the crawl space, and couldn't find guidance anywhere.

In reporting here, I intend to be useful to contractors and their management authorities everywhere. I hope to also get the attention of batt manufacturer Bonded Logic, Inc.. Bonded Logic may not sell product with no responsibility to advise in competent usage. From an experience here, consumers should learn that benefit from cotton batts is not easily obtained. There are many ways to use them inappropriately. Cotton batts are not uniquely "green;" in that deserving slack over misuse. Search, that now readily finds this blog post, nets little other help, and finds a lot of condemnation. Cotton batts are useless placed alone as wall insulation, where they can't adjustably fill cavities, and cavities not full may have no effective insulation. The recently-added Bonded Logic brag of perforated batts  is empty. Batts still will not fill a wall on thickness, and perforations will likely be at unlucky widths. 

Here, I find pretty decent usage of cotton batts in an attic floor as top layer with flexible fill-in of fiberglass, liking that they tolerate being walked upon. In a crawl space, after a lot of work, I guess they are ok.

Photos that follow are drawn from a Web album with similar captions:

Repairing The Installation Of Cotton Insulation Batts In An Attic and In A Crawl Space 

The attic treatment of cotton batts began with taking down batts unwisely hung from roof joists. After a couple of years, mold was starting to grow above the batts, at the underside of the roof sheathing. Batts were wet.

Cotton batts dropped from roof joists and brought up new, would cover about three quarters of the attic floor.

Top up an R21 insulation base layer using new R11 batts. Supplement R30 cotton batts crossing floor joists, with R30 fiberglass batts. Protect all soffit vents with plywood baffles, and place R30 all the way out to cover exterior wall headers.

Note a Romex electrical wire here, correctly running over, not through floor joists. With thick insulation, electrical service should be permitted by simply lifting top-course batts.

Plywood decking is very important to work access. Plywood is raised 5" above floor joists, upon new 2x4 uprights 24" oc.

Furnace return air ducts are covered with R21 insulation, minimum, including a firm skin of poly skrim kraft upon R11 basement wall insulation. Duct insulation is tucked into top layer batts, or is screwed to plywood decking.










With the blocked access, the home owner was concerned about the placement of the crawl space batts. The batt installer, after days of awful work in this, would not be confronted.  Thinking things weren't right, the home owner chose to forego a rebate claim, and didn't know what to do for resolution.

In the course of attic work, I inspected the crawl space. I reported that, as expected, the twined-up batts were sagging everywhere, only in contact with flooring in lines at edges. Full floor contact is mandated by regulating authority, Energy Trust of Oregon, ETO. Their rule stated:


Insulation shall be installed so that there is no air space between the top of the insulation and the floor.



Unacceptable work is not eligible for rebate, so a rebate now would give the home owner some compensation for the cost of needed repairs. The installer refused to accept any responsibility in this, but we will see what happens in review after the repairs.

In time, I devised a repair plan, posted for more than a year, and shared for comment with responsible parties, manufacturer Bonded Logic, Inc. and regulator Energy Trust Of Oregon. There was no thinking or standing up with me for the interest of the home owner.

This is the actual method of tying up crawl space batts that I had to work with. Batts were generally in pairs of matched 48" length, one 23" wide, the other somehow sawn 21" wide. The twine was fairly useful near to floor joists, and I left it in place. At about every 9" on average, in the slot between batts, I stapled up a loop of 17ga electric fence wire about 20" long, thus:

The battens typically were cut to 43" lengths. I used about 200 eight-foot lengths, costing $1.79 each. The lumber cost is significant.





















Now consider how this might have been done, starting with new batts. I think each batt might be thrown up, upon a 2x3 or 2x4, to then be progressively secured higher-up, with wire and battens. The wires might be preset on other wire or lumber, adding to material cost but saving labor.

The same number of battens are needed whether or not there is benefit of prior twining. Lumber cost here remains about $400. 

There is a nicer solution that has higher material cost, but would be superior overall:

Complete coverage with 3/8" CDX plywood sections costs about $15 for each eight-foot length of joist bay. Four eight-foot 1x2 battens in the same service would cost about $7. The lumber cost is doubled, but the isolation of insulation is a good deal, that should be mandatory. No insulation anywhere, not even on an attic floor, should be left raw, to be abused. Reduced labor costs might more than compensate for plywood cost. Where insulation is already hanging down but is not foul, this is a really good solution.



Home Performance Education For The Determined Or Advised Reader

The situation of waste found in this home had existed for nearly three years.  

Enter then, myself, first for the attic work. I was discovered through new home owner membership in Angie's List. Already in Fall, 2011, I had been banished as a Trade Ally of Energy Trust of Oregon, and could not be found among the "players." Banishment for a year, but now seemingly forever, was for reporting to each customer the things I do, that are not done by those within the embrace of Energy Trust, contractors who brag upon the misperceptions of "Home Performance With Energy Star," HPwES. 

The problems with HPwES begin with a basic false claim, that a blower door is the guide and measure of weatherization progress. As guide, in eight years of ever more-professional service, I have never seen a situation needing guidance of a blower door. As measure, achievable sealing rarely has value of more than $20 per year.

I have repaired many large energy bleeds not at all detectable by a blower door. Most attic floor pits, as with the generally-found chimney chase, have little effect on blower door readings. Where the goal is real or jiggered improvement of blower door readings, by hundreds of CFM50,  correction of floor pits is not rewarded.  

Even where they might affect blower door readings, bleeds are almost never found that way. The clean-shirted technician can not and will not be in the usual dark and dangerous attic while his blower door is operating.  Workers will rarely take initiative to fix the things they might see and care about, of course unknown, then not in a contract. Buried problems usually have much higher opportunity cost, than any benefit.

Among issues that could be seen and expressed, the home owner was very upset by ugly and useless "sealing", as characterized by this crude aerosol orange foaming about the exhaust duct of the kitchen microwave, in a kitchen cabinet. 


















The conditions of unacceptable sealing found, and their repair, can not be summed up in a few photos. For the detailed story of sealing, please download and study a large pdf album:

Real Sealing Fixes HPwES Sealing In An Oregon Attic 

Where CFM50 = 7.5 * (Hole Size, sq in), total ducts hole size is 71 sq in., as with more than two 6" ducts (28 sq in each) fully detached. If workers found two duct sections detached, and reset them without comment, that is not duct sealing action of goop troops. It should not count. If ducts can fall down, then how could workers justify leaving the crawl space inaccessible after their departure? Leakage of 205 CFM50 is still huge, and should not be allowed. None of the steel ducts were found or left with required screws. Nearly all joints, now stiffened with goop, remained closed by dried-out ordinary duct tape. This was not duct sealing by some scientific process, and was not worthy of compensation. Most of the involved money should be reclaimed to compensate the home owner for the cost of my fully replacing the ducts, needfully and with courage, restoring access for extremely difficult work in the crawl space.

I don't believe sealing actions could have amounted to more than a few hundred CFM50. A 100 CFM50 reduction is closure of 13 sq in, a total equivalent hole four inches diameter or a gap 1/16" wide and 18 ft long. The great majority of reported reduction was from knowing fraud in devising a to-be-closed air handler room yet attic floor pit, with a gasketed new door. It is not allowed that an interior door may be closed in pre or post "Home Performance Testing." The door was a mystery to the home owner, perhaps to be closed for convenience.

This was my third run-in with this contractor, where I did the real sealing. In one, there were a car-bashed large hole in the garage wall, hidden behind a woodpile, and two closets with large leakage to outside controlled by closing doors; of course none found by blower door.

No one does better sealing of an attic floor or HVAC ducting than I do, with absolute disdain for fraud of Home Performance. I find problems as one must, digging down and dirty, by sight. I don't just reduce duct leakage. I methodically eliminate it, verifiable by sight as I go, and in method-sampling photos.

Here is discussion of my improvement of the crawlspace HVAC ducts in this home:
http://energyconservationhowto.blogspot.com/2013/11/more-hvac-circuitry-in-crawl-space.html 

The ugly obstructions beginning at the access hole are gone! Repair of the cotton-batt insulation could only be done after removing the found HVAC ducts for recycling. Quite a pile. Hundreds of pounds of steel that had responded to every furnace cycle .