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Sunday, March 25, 2012

The Value in Sealing Wall Headers

The savings to be achieved in sealing wall headers are from the very large areas that will convect, where air churns within the wall, refreshed in an infiltration path, or maybe as a throttled static floor pit equalizing with attic air. I think simple math can apply on average, and on instinct choose that of a floor pit, reduced to 25% of temperature equalization with the attic. It would not be hard to confirm an assumption like this, in a serious laboratory test. Has anyone reported on this?


Further simple averaging might present a useful average interior wall area, as a multiple of a home's conditioned space area. I am interested first in one-story homes predominant in the drywall era. An example diligence report finds 2240 sf interior wall area, where home heated space is 1630 sf. Headers affect heated space, times maybe 1.4?


In this example home, I find savings of $448 per year from the sealing of wall headers. I don't know exactly how much time I spent, and cost is all labor. The sealing was done progressively as I staged work areas with stowage of tools and materials.  Two man days, where staging, vacuuming and other efforts also served the sealing? Maybe four, where I reckon decking made the work possible and bearable? I needed the lighting. If I allocated $800 of job cost to header sealing, it is still as profitable as the quicker sealing of ordinary pits. Payback in under two years.


Heat carried in excess infiltration through header gaps, matters less than the wall convection. In the example home there are 140 ft of wall headers. If the average combined gap along two walls is 1/16", gap area is 105 sf. By Insulation Math, involved infiltration costs $0.555*105 = $58 per year. The corresponding reduction in a blower door test is 7.5*105 = 800 CFM50, a worthy result.


In the example home with found R18, final R50, the added insulation saves $112 per year, at cost of $1536. Simple payback awful, in fourteen years.







Saturday, March 24, 2012

Sealing Wall Headers

Homes finished with drywall, or finish plaster over plasterboard, will have gaps seen in the attic floor. Wall drywall can't conform to both headers and (imperfect) studs, and fit give is predominantly at headers. At ordinary wall headers, there is a gap of at least 1/16", on one or both sides of the header. Gaps are reliably larger at wet walls where there are fit mismatches of doubled 2x4, and 2x8 studs. New homes still are rarely built with new airtight drywall methods, and probably will not employ best available gaskets.  Steel framing will result in many weatherization tragedies. 

The only useful instruction offered to me, for competence in weatherization, is that I must seal these gaps. That's it. Ten years ago, a class called Basic Air Sealing. For free, as it should be. I reject the HPwES training of weatherization workers of the past eight years, now delegated to very expensive and incompetent for-profit trainers. HPwES trainers and practitioners tell the absurd lie that a blower door is the means and measure of weatherization. Sealing opportunities in an attic are never found while a house is disabled of usability under blower door test conditions. All opportunities are discovered by sight, as one makes progress through the job, sometimes over the course of several days.

I believe complete sealing of all wall headers is important, and do it without fail. It is made easier for me by installation of safe access, secure decking and lighting. I dig down even through deep loose-fill, in the rare instance where a wise home owner now wants access, as to deal with defective attic ventilation. 


Caulking is the usual sealing method, and I have tried everything offered. Gun-applied foam is fast. I have consumed several Sharpshooter X guns at replacement cost up to $50, and lots of regretted volatile cleaner, yes, claimed exempt VOC, making messes and still not preserving the life of a gun that might be idle for a month. I think a frozen gun is not worth the time of repair, with accelerating degradation. Tube-dispensed caulk goes fast with poor volume control, will not bridge gaps larger than 1/8", and is a tracking hazard on shoes.  




I always have flexible grout in hand in a one-pound tub, for interior work as in a can light annulus. This fingertip application is tedious, but I have not lost a couple hours readying a foam gun. The wetter the surface at application, even down into vertical surfaces, the better. The grout must be handled as paste, but dilutes and is carried into water, like platelets. Little material is needed to bridge a gap. Go back sometimes with repeat quick application. I won't likely step on a treated wall header, in the fifteen minutes before material is dry. Anything tracked could be removed by vacuum or damp sponge. 


The flexible grout is a plaster crack repair material, and much more. I advocate for it to be available everywhere, at my plaster repair blog, offering free samples with promise of impending use and posted report of the experience. I extend the same offer to weatherization advocates and contractors. In weatherization, we must experiment with the packaging. Perhaps the wetting might be by brush of material at paint consistency. Hand-packing paste into an Albion bulk gun was a time loser, with the same overfill problems that are wasteful of squeezed tube caulk. Availability for weatherization might come faster if the material is also used to seal joints of HVAC ducts. Goop presently used on ducts needlessly is not water based, is horribly sticky, and is awful on equipment and clothing. An elbow might not be permanently ruined for reuse, if sealed with grout, not goop, at its alignment seams. Longitudinal pipe seams, aiming up, would be easy to grout.


I am aided sometimes by ability to bag and reset loose fill insulation, using 55-gallon drum liners, always several for trash or for transfer, on a job. With only a few inches of loose fill, just brush away.