My Observed ACH50 Numbers in Pre-1990 Existing Home Weatherization

This review of my blower door experience is in challenge of numbers near 30 ACH50, found in example Home Energy Score Reports, issued by US Department Of Energy, Better Buildings Program in years 2015 and 2016.  The reports are both for fictitious homes in Arkansas, built 1970, perhaps with little consciousness of energy efficiency.

 2015 Example:
v2015_HEScore_BB_example_12-15-15.pdf ,  a two-story home 1800 sf with 8-ft ceilings, testing in at 4200 CFM50, 17.5 ACH50. I did not remember confronting so large a number, before.

2016 Example:
Home Energy Score Report Example.pdf , of about November 2016, a single story home with ten-ft ceilings, 1500 sf, testing in at 6500 CFM50, 26 ACH50.

If such large numbers are not fictional in lax construction for milder-weather Arkansas, it does not suggest that huge savings from air sealing justify blower door madness, in Portland, Oregon. Few weatherization contractors in this area will accomplish real tightening of more than 3 ACH50, and some with their building scientist pedigree as blower door believers, will charge more than $2000 for the deed. Yes, at such unjustified cost, it is not worth doing. For a 1000 sf Portland home with an inefficient gas furnace, even with $2 per therm applied cost of natural gas heat, the savings per ACH50 reduction, in preheat cost of fresh air, are only $10 per year. Please see my Insulation Math . Annual savings of 3*$10 = $30 per year at cost of $2000 are a poor investment. At best, the present value of savings through a twenty year horizon are 44*$30 = $1320.  Please find that *44 payback multiplier (vs. *20) in this blog post .

At fair sealing cost of $300, the return is excellent. Abhor a blower door and test-in, test-out , with this. A blower door is almost never employed as the guide of important sealing measures. The value in tightening a home is in just acting in a permanent way, upon every sealing opportunity one sees, in dealing with evident drafts, and in the course of preparation to add insulation. Preparation must include all treatment of home integrity including plumbing, wiring and roofing deficiencies, that would be obstructed by the added insulation. Wiring includes anticipated communications wires and upgrades to permit most-efficient LED lighting.

Where I have spoken out as an Energy Trust Trade Ally, I have asserted that blower door testing with public support should be done rarely, for a stated purpose. Results should then be freely shared, so that we can accelerate consensus on further testing investments. This narrowing of test practice and sharing of paid-for results, never happened. My own sharing here, from my own investment, is a start.
My Test Results
I owned a Minneapolis blower door from 8/15/2008 to 5/16/2009, to dutifully employ it for air sealing test-in and test out in qualification of customer rebates. Finding no other resource, I trained myself with measurements in my 1955 single-story ranch home, 986 sf. I quickly found a stable, repeatable 1330 CFM50 Baseline result. This is 10.1 ACH50, a bit more drafty than the 7 ACH50 target for a healthy home. Tightening my home would take more than three years of staged effort, never to need or to again employ a blower door.

Higashi, October 2008:
The first test in a customer home was done 10/17/2008, a larger single story home, testing in at 1625 CFM50, 14.4 ACH50. The home tested out 11/10/2008 at 1410 CFM50, 12.5 ACH50,  with $27 per year saving of cost to heat makeup air. This was in sealing and insulating of poor solid-steel HVAC ducts of both attic (return) and crawl space (heated), with no other evident opportunities. An air sealing rebate of $215 was paid at a foolishly-offered $1 per CFM50 reduction. The work did not include any discovery under blower door conditions. The crazy ducts block crawl space access and are likely to be detached and again to leak, soon. I did not feel good about this, but always seek the maximum offered rebate for a customer.

Bronner, November 2008:
The second test was done 11/24/2008, testing in to check work of one notorious HPwES crew. who failed to do any apparent sealing, missing quite-large opportunities including a garage wall holed by long-ago car impact of a wood pile. The test-in was 3740 CFM50 in a complex 1937 two-story home, 11.8 ACH50. The test out 1/19/2009 was 3050 CFM50, 9.6 ACH50, but this large improvement, not earned, is thought to be due to closing the door to a conditioned basement, not likely the condition in other tests. I became fatally disenchanted with my blower door here. A blower door show would never be of any use to me in finding anything, and only wasted a half day of progress. I immediately sensed that prior testers in a home always used their blower door only as a marketing scam, not understanding readings at all and doing nothing useful by the testing; always spending more time in testing than in crude and unguided “sealing.”

Costello, December 2008:
The third test in a customer home was done 12/12/2008, testing in at 760 CFM50 in a small single story ranch home, a tight 7.0 ACH50. There were no sealing opportunities and no test-out, where the attic was insulated and the crawl space was sealed and conditioned.

Levine, February 2009:
This is a typical bungalow home with top half-story weirdness, with result 2300 CFM50, 12.0 ACH50. There were no sealing opportunities in my attic access and insulation work, and no test-out.

Three jobs have shed light on other contractor’s misuse of a blower door, and the magnitude of home leakage that might be found in the majority of existing homes, which were built before 1990.

Wheeler: (January 2010)
This is a 914 sf single-story home built in 1951. It was evaluated as one of 200 homes in a 2008 pilot program of assigning Energy Performance Scores, EPS, in existing homes. The assigned EPS score of 80, was done with PTCS duct sealing  and with R30 insulation of the crawl space by an independent contractor. A blower door test-in of 3670 CFM50 was reported. Extremely large 30 ACH50 was not computed, and was not attributed to a fallen-down duct in the crawl space. That duct was simply reattached by the CS insulation contractor, who may have needed to remove and then reset, all ducts. At May, 2010 and no longer owning  a blower door, I just thoroughly fixed things in the attic of this home. Fixes included replacing broken HVAC solid steel ducts much in the way and frequently stepped-upon, that had been gauze-wrapped and gooped as evident teaching of PTCS that goop fixes anything; the goal is cheapness independent of durability and safety against traffic hazards. I would hereafter have complete disdain for PTCS and EPS.

Weigand: (May, 2010)
This is a 1400 sf single-story home built about 1970. It was  my second confrontation with one notorious HPwES crew, which reported 4220 CFM50, 22.6 ACH50. This extremely large infiltration, not flagged for concern, is in part the result of construction with exterior walls open to the attic. I thoroughly insulated the attic of this home, with preparation including replacement of many poor solid-steel HVAC ducts, sealed air tight. I was not allowed to cap the exterior walls.

Chamberlain: (October 2011)
This is a 1590 sf single-story home built in 1973. This was  my third confrontation with one notorious HPwES crew. The home tested in at 3392 CFM50 (20 ACH50), and tested out at 2248 CFM50 (13.2 ACH50). The very large CFM50 change, 1144 CFM50, at paid cost $450, might have qualified an air sealing rebate of more than $1000, but in the end this home owner did not get any air sealing rebate. The achievement not rewarded, was fraudulent, with perhaps-deliberate misuse of a door to generate most of the reduction. Negligible sealing was achieved in the attic, leaving test-in of about 20 ACH50. My very thorough and imaginative sealing surely reduced leakage by more than half, less than 10 ACH50, but in this Energy Trust did not care. I could not engage a volunteer to do the test out as a learning exercise.


More than 30 ACH50  is possible then in pre-1990 existing homes, where testing is with detached HVAC ducts. Absent detached ducts, numbers much more than 12 ACH50, are not in my experience. I did try to employ my blower door just before it was sold, in a 3500 sf three-story home in Northeast Portland, and found I would have needed several blowers to generate minus fifty pascals test conditions. The evident problem was balloon frame construction, and my interest in testing was over. I can ony suggest that this home with hydronic heat, no heat ducts, was well under 30 ACH50 test-in.


In the course of this exercise I discovered writing by Allison Bailes III PhD, Energy Vanguard, upon discoveries in his Atlanta condominium, built around 1970. Higher infiltration numbers are to be expected in multi-family homes, but his blower door numbers surprise me. 
(At July 18, 2016)
http://www.energyvanguard.com/blog/how-i-achieved-a-21-increase-in-airtightness
Here find test-in at 29.6 ACH50, where part of a bathroom ceiling is missing. Ceiling patched, and with some air tight sealing of exterior walls, the number is down to still-large 20.8 ACH50. Despite advocacy for and practice of blower door testing, Mr. Bailes seems to despair of further reducing his condo fresh air supply.

He had previously found that Celotex exterior sheathing under a brick exterior of the complex was severely buckled. 
(At April 26, 2016)
http://www.energyvanguard.com/blog/air-flow-pathways-in-a-leaky-bathroom-wall 

Here is the report of fixing the exterior sheathing leakage, at a bathroom wall only.
(At May 23, 2016)
http://www.energyvanguard.com/blog/how-to-fix-a-leaky-underinsulated-exterior-wall 


Also in the course of this exercise I found that homes built from 1994 to 2004 are notoriously leaky, due to cheapening of exterior sheathing, at least in New Zealand . The leakiness refers first to rot problems. We in USA too have cheapened exterior sheathing in reliance upon house wrap, and have had lapses in provisions to screen and drain falling water. Where this is thought the concern of building science, a blower door operator will not be depended upon for solutions.

Mandatory Attic Access Walkways

I submitted the following among proposals for 2018 revision of the International Energy Conservation Code:

Proposal submitted 1/4/2016:

R402.2.4 Access hatches and doors. Hinged doors and lift portals from conditioned spaces to unconditioned spaces (e.g. attics, unconditioned basements and crawl spaces) shall be insulated to the Energy Star standards of exterior opaque swinging doors, and shall be air sealed with well-fitting gaskets. The portal frame shall be sealed air tight in its rough opening. (The standard says: U-Factor ≤ 0.17)

The entry to an attic space at a portal shall have a surround of an ample raised floor that does not diminish insulation value. Flooring shall protect insulation against trampling while giving safe passage, to all attic electrical service points including fans, lights and junction boxes. Junction boxes not accessible from heated space shall be raised above insulation and flooring levels, or where this has failed, shall be flagged as a decked service point. Accessible service points shall include static vents that require periodic cleaning. Where a service point is buried in insulation, insulation over the service point shall be in batt form and tolerant of displacement for accessing the service point.

Existing code of 2015 says:

R402.2.4 Access hatches and doors. Access doors from conditioned spaces to unconditioned spaces such as attics and crawl spaces shall be weatherstripped and insulated to a level equivalent to the insulation on the surrounding surfaces. Access shall be provided to all equipment that prevents damaging or compressing the insulation. A wood- framed or equivalent baffle or retainer is required to be provided when loose-fill insulation is installed, the purpose of which is to prevent the loose-fill insulation from spilling into the living space when the attic access is opened, and to provide a permanent means of maintaining the installed R-value of the loose-fill insulation. 

All of this, and supporting statements offered to conference readers, is summarized in page Better Building Codes For Access Portals, at my web site r5portals.

I defended my proposal at 2016 Committee Action Hearings of the International Code Council in Louisville, KY, on April 18, 2016. There was expressed disdain in the matter of insulation value of a practical hatch, that I cited rival Energy Star standards, and no acknowledgement of my comprehensive math proof, that modest insulation is best; more on that elsewhere. Here, address the second-paragraph flooring requirement, forcefully opposed by one of the rotating intervenors of the National Association  of Home Builders. I took this opposition as formidable, in judges unanimously disapproving my proposal. Several participants privately encouraged me to persist in this and some of my other proposals, but no one came forward as an ally, to help if I would double my onerous personal investment, to offer and defend revised proposals, in Public Comment Hearings, Kansas City.  Those "final" hearings were concluded a week ago, and I was not there. To not feel defeated, I must believe that I am intent upon readiness to try again in the next of the three-year code cycles; then having time to enlist allies.

Here, add defense of the second paragraph of my proposal. I have a really-good example to share, of work done in Oregon City, Oregon June to July, 2016. A customer had discovered that large areas of the attics in his two-year-old home had no insulation. Hard to believe, but evidence showed in zonal early frost melt on the roof, unlike neighboring homes. 500 sq ft was bare, some seen in this view.  I suggest that a mandatory walkway here and an access cut further on, would have led to different and better construction choices. Impaired access is not good, for anyone.

In this photo see beginning of rapid and easy change. The scattered temporary plywood is important to my safety. I have cut down a horrible 16"  OSB skirt about the small access hole.

Move interfering HVAC ducts, and temporarily detach a bath fan duct. Separate HVAC flex ducts at a wye, and move them under the diagonal truss members.

Many trips are needed along a new smooth and level walkway, upon 32" bridges of truss elements. Cut batts to fit, in the garage, and carry pieces in a growing collection of empty insulation bags. A safe passageway should not be an afterthought. Many good things, not least worker safety, result from good access. Let access be lighted too. At least, let workers find power outlets to not rely on a flashlight.

In this access exercise, learn some lessons about HVAC duct installation, attic ventilation and a further thoughtless neglect of access. Preserving duct length is very important as ducts are disassembled and reset. Yet, I must sacrifice about 6" from each flex duct at this wye, because of remnant bad advice of PTCS trainers in the service area of Bonneville Power Administration. Goop, no longer required, should never be applied for liner attachment.

Goop applied blindly and in risk of clothing, missed this under-side zone of the main branch of the wye. There was duct leakage, out of sight. UL181 Nashua 557 tape easily achieves zero leakage here, and is the right choice for easiest damage-free separation of ducts for maintenance or replacement. Know that flexible ducts have claimed useful service life of not more than ten years . See example of Thermaflex ducts as fallen-apart rat paths after about 25 years .

I know that regardless of found condition, I must replace cardboard soffit vent baffles. They rarely survive more than thirty years and when used are with no manufacturer thought or guarantee of acceptable service life (sixty years!). Here I have more than conscience in play. Curl with detached flimsy staples is ugly. Looking down at vent bird block, see poor bird block design employed by most builders. Slot placement demands vent baffles 3 1/2" down from roof sheathing, a large sacrifice of potential insulation depth over exterior wall headers. This bird block is needed in every available roof joist bay, not in every fourth.

Lumber for proper soffit vent baffles is free, in good employment of job scrap. Use 25 cents of good deck screws, not nails. I assembled six baffles in thirty minutes. This is quicker than setting a $1 cardboard baffle, thus less expensive. Wood sleds are easily adapted for obstructions, then set much more securely.

Baffles just 32" tall are ample over R45 batts. I can push R30 top-layer batts tightly against a baffle, for fullest insulation value, and that is the controlling economy.

A hidden attic around this corner was uninsulated too. The triangular access is new. Opportunity was concealed behind redundant OSB sheathing.

While I am at this I will insulate over the garage too, to just R15. I can't bear to crawl there carrying insulation, through this jungle of beam and variable trusses.

Cut in a new access for the garage, "factory built" in my shop. Where truss bottom elements are 2x4, they must not carry loads unless strengthened as composite beams. Leave a couple of 9" rips of plywood that I needed for my safety, but not more flooring.

Here is the fully-dimensioned plan of my hatch, offered to anyone as noted here.

At June 18, 2021, I revisit this post upon reading the post of this date at Insulation Institute Blog: A Hot New Home and Missing Insulation. I see that this post should go further upon process of inspection, not just means of inspection. Process should be for information to the builder and ultimate home owner and not just a manager of building permits. Building permits delve in the short-term self-interest of a builder, to get a certificate of occupancy. They involve inspection requirements  often flouted. by disinterested and unmotivated municipal employees, who take an easy path where inspection is difficult or impossible.

Get better results where inspection is primarily in service of the self interest of the home occupants ever-after. Those citizens of the community  are the real employers of the inspectors. Let these employers then receive indelible proof of critical performance items in the form of pdf documents I call Diligence Reports. A diligence report is created by a professional technical writer rated for integrity and skill in taking photos and notes from the builder daily to generate each required Diligence Report. Report contents are driven by task checklists, and comply with simple national standards. The involvement of three parties in the satisfaction of checklists ensures honesty. 

A recent customer was fascinated with the notion of Diligence Reporting, and made this hat for me! 

I wondered when I would first find cause to share the humor.

Following ACEEE Blog, Furnace Fans As Energy Hog

I'm just a seventy-year old educated person doing weatherization of homes by myself as I see fit, learning and sharing methods and concern over policy issues. I blog. I maintain web sites. I have leading-edge insights in things I pursue, such as fast adoption of better LED down lighting. Writing on 8-26-2014, I am obsessed with an impending meeting in Portland, Oregon, on about 9-30-2014, a hearing of Oregon's Public Utility Commission in turmoil over strange assessment of weatherization cost-effectiveness . I have a lot to learn, if I am to have a contribution to a better outcome. In my research I see valuable writing by ACEEE, the American Council for an Energy-Efficient Economy. They have a blog, and near top I find this post :

Taming an energy hog with efficiency standards 

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June 25, 2014 - 12:12pm

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By Joanna Mauer, Technical Advocacy Manager, Appliance Standards Awareness Project (ASAP)

The Department of Energy (DOE) issued new efficiency standards today that will dramatically reduce the energy use of a little-known home energy hog. Furnace fans, which circulate heated and cooled air throughout a home, consume more than twice the electricity in a year as a typical new refrigerator. The new standards will cut the cost to power furnace fans by about 40% and also deliver improved comfort.

Most furnace fans come as part of a furnace. But in homes with central air conditioning, the fan circulates cooled air during the summer in addition to the heated air during the winter. Furnace fans consume about 1,000 kilowatt-hours per year, or almost 10% of the total electricity use of an average U.S. home. And yet, while the energy use of furnace fans is significantly higher than that of other common home appliances (see below), because furnace fans are inside a furnace, their energy consumption is hidden to most consumers.

And, I comment:

Your furnace fan likely consumes more than twice the electricity of your refrigerator. In time a new furnace will implement some cost savings for you. But, please think. In most homes, most of the load on that fan is in hacked-in D-boxes entering and leaving a furnace. We must NOT continue to build heating systems where ducting is an afterthought of the arriving installation crew. We must install intelligently-designed hydrodynamically-efficient plena . These plena must not be judged solely upon higher installed cost, to be avoided.

The fan is not simply the hog. It is the summation of fan with leaky and stupid ducting. We should replace that ducting now. When your furnace fails, and that is the cost-effective time to replace it , be ready with the better ducting already in place. Your installer won't give much thought to your ducts if called in an emergency, perhaps not offering improvement under any circumstance. Fix ducts now, upon your own initiative! The engineered plena and strongly-attached, zero leakage ducts, will only make your furnace more serviceable. In the deal, get rid of heat capacity in ducts , acting just like leakage.

At 9/28/2015, admit that electricity draw by a furnace with a squirrel cage fan goes down , if ducts are more resistive and blower flow is reduced. Added cost with poor duct design is in longer run times, and greatly increased run times to cope with an important room that has inadequate register flow. The savings in motor electrical efficiency are very large , but this is not associated with a campaign for better ducts. In time, I will rewrite the previous paragraph. I will not relent in campaigning for well-built ducts, asserting that octopus D-box ducting is foolish.

At 9/27/2016, begin reporting of experimental measurements of blower behavior as function of duct resistance. Here is a setup to measure furnace electrical power draw, as one of the efficiency parameters:

Caption:

This Kill-A -Watt meter is in series with all electrical power draw of my furnace with very-efficient ducts. The display here is of 7 watts dead draw. In a heating cycle, the power steps up to 130 watts while firing and then to about 450 watts (5.2 amps) while the blower runs. 

If I fully cover the return air filter with cardboard, I hear rumbling complaint, and power draw falls to 400 watts. The lesson is that duct inefficiency will have little effect on momentary power draw, yet large impact on fuel and electrical energy consumed, in proportion to cycle time, inverse to blower flow rate.






My challenge in assessing savings from improvement of duct efficiency will be to sense change of blower flow rate with logical reduction of duct resistance.

Google:
Squirrel cage blower flow rate impact of reduced duct resistance 

Find AMCA, Air Movement and Control Association International, Inc. , via Wikipedia at top of the search. I hope that AMCA can help me in test setup for the myriad of home situations I will face. I am advised by excellent blower manufacturer Rosenberg USA , that flow rate is not easily or accurately inferred from static pressure measurements. I don't expect to get much help from any furnace manufacturer.

I can reach some conclusions about operation with variable duct resistance, from two non-obtrusive holes in my furnace ducts. Operate my new Testo 510 digital manometer in scale Pascals, Pa. I don't need any heat in warm late-September, but run the thermostat up to force heating cycles.

With furnace firing and blower running, read 33 to 35 Pa across the filter. Close 75% of floor registers and read 27 to 28 Pa, corresponding to a 10% drop in flow through the filter. After firing stops, and with registers again open, observe 32 to 33 Pa filter pressure differential.

Extreme changes to ducts aren't likely to change blower flow by more than 10%. Where reduced flow is with same heat input, the temperature at registers will go up, and cycle time will change little.






I learn here that measurements of operating cost effect, may not help to justify duct innovation. Perhaps it is enough to offer such for reasons of getting ducts buried, out of harms way. and for better regulation of equal register flows without need of dampers and their confused settings. In the process, ensure there is zero leakage of ducts, and a minimum of the leakage-like effect of needless thermal mass of steel, swinging with furnace cycles.

Where I offer sealing and insulation improvement along with duct innovation, I despair of making sense of measurements now possible with my investment in instruments, from long-term monitoring of expected home energy savings. 

More HVAC Circuitry, In A Crawl Space

The above diagram of a crawl space warm air duct system is a 1:120 scale drawing, with overlay of structure details upon a Google satellite photo. Please note similarity to planning graphics and involved ducting elements for similar achievement in an attic.

Photos and discussion parallel a post in a web album, More HVAC Circuitry, In A Crawl Space. The really curious may examine too, a full photo album CS Insulation Repair and Heat Ducts, including found conditions of the failed UltraTouch batt installation by "twining" method, and of impassable and leaking conditions in the found system of steel warm air ducts. A separate blog post will address the cotton batt insulation repair. The involved home in Hillsboro, Oregon is also the site of a publicly-shared full photo album documenting attic floor weatherization with UltraTouch cotton batts: Real Sealing Fixes HPwES Sealing In An Oregon Attic. Full pdf photo albums always tell a story best, but please know they are poorly rendered when viewed in GoogleDocs. If you want to examine such albums, please bother to download them.


Elements of a new warm air duct system are in two nearly-equal branches, called North and South. The branches include a well-considered set of plenum components below the furnace. A 14x19 turning plenum replaces a crude D-box.

The furnace plena have a 1" insulation liner and end in a triangular head with two 12" starter collars serving a system of flexible ducts.

Two 6" registers near the furnace are served by the first of four lateral take-offs, circuit label T12x6. These and all steel couplings of flexible ducts, are hung from the overhead via eye bolts. These two, hanging low, are pulled up by wire loops. Never support steel couplings by strapping upon the flexible ducts. Don't rely on screws and tape for suspension via metal couplings.

Here note the 1" insulation lining, and turning vanes. Getting prepared with such well-conceived and well-built elements is a small step of installer professionalism. Expect you may need a couple of weeks lead time for fabrication by a superior sheet metal fabricator. My fabricator in Portland, Oregon is Vinje & Son.

Don't accept dissing of flexible ducts, that they have extraordinary friction. Where each duct section is fully supported by straps and by steel couplings, draw small tension in the liner, taking up coils as needed, to align the duct and coupling. High-resistance problems are always the result of careless alignment, with tripping over steel edges. Plan excess of insulation jackets, to draw them fully-overlapping, over couplings.

This is coupling component R8x6, used two places at branch ends, where 6" ducts to registers are of length not more than six feet. I wish for simpler one-piece reducers, but want ample starter lengths for liner take-up and secure taping. Here and in the previous photo, see that the eye bolt hanger of a steel fitting passes through a hole in plywood overhead. A wood dowel cut from nimble tree branch passes through the bolt eye to releasably hold everything up. The release can allow better fit of insulation jacket overlap.

Here is the completed end of the North branch at a 6" register. The hanger of the R8x6 is out if sight above the jacketed water pipe. See only tough black liner, strapping and some Nashua 557 tape. Leave no opening for mice. Wherever possible, draw ducting tight against plywood guides, as barrier to mice.

This is the new heart of the duct system under the furnace, with a turning plenum.

This is the well-strapped head of the North branch 12" duct, tightly in contact with overhead 1/2"  plywood strips. One can readily crawl anywhere in this crawl space, sliding under the smooth plastic covering if necessary.










The following is an exercise in defense against anticipated criticism there are no balancing dampers and ACCA Manual D consideration, in new invention of furnace warm air ducts.

Please see that residential HVAC should be naturally balanced with good flow dynamics in orientation and more, of plena, take-offs and reducer or wye fittings. Air flow in thoughtless ducting can be extremely chaotic, and not amenable to tweaking with manometer measurements not-at-all understood. With smart ducting, simply rely on the already-present register grills.

The practical concerns in duct design are to allow overall free flow, limiting air handler power draw, and getting the heat where a deficiency is noted. The complaint to be resolved will be of too little heat in a favored room. Don't respond by dampering flow to other rooms. Just tackle the duct path to that room. Find an obstruction, perhaps a crushed or pinched duct, or misalignment in a coupling. Failing that, increase the size of ducting for that room, perhaps just in a more-intelligent register. Look for missing insulation as the cause of discomfort.

At Pinterest , please find a growing collection of affordable and suitable HVAC registers, that include easy damper adjustment.