https://www.energyvanguard.com/blog/the-lesson-of-the-raining-dripping-crying-duct-boots/ Building science knowledge, HVAC design, & fun Fri, 08 Oct 2021 11:48:14 +0000 hourly 1 https://wordpress.org/?v=6.6.2 https://www.energyvanguard.com/blog/the-lesson-of-the-raining-dripping-crying-duct-boots/#comment-4683 Mon, 28 Jul 2014 05:50:04 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-lesson-of-the-raining-dripping-crying-duct-boots#comment-4683 I recently did an assessment
I recently did an assessment on a house here in Charleston, SC that had its first floor HVAC ducts in the enclosed vented crawl space just as many other homes here do. We did a duct blaster test and determined that the ducts were tight as a tick. The duct system had 3% leakage to the outside. When I later ventured into the crawl space I found the duct insulation to be saturated pretty much throughout, and water was dripping from the bottom of all of the insulation. The duct insulation was R-6 which is code in crawl spaces in our climate zone (3). I wouldn’t be surprised at all to see this in a leaky duct system, but I was a little surprised to see it in such a tight system. I’m searching through some of Lstiburek’s stuff now to see what he has to say about it, but I’d be glad to have input from others. Thanks!

]]> https://www.energyvanguard.com/blog/the-lesson-of-the-raining-dripping-crying-duct-boots/#comment-4682 Mon, 19 May 2014 06:20:33 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-lesson-of-the-raining-dripping-crying-duct-boots#comment-4682 Another condensation problem
Another condensation problem occurs in cold climates in the winter with AC ducts in the attic and a different heating system. The house air with its moisture rises into the ducts, cools and condenses the moisture, cool air sinks and is replaced with more warm moist air from inside the house. The condensation puddles at low points in the duct and some times finds a way to leak out.

]]> https://www.energyvanguard.com/blog/the-lesson-of-the-raining-dripping-crying-duct-boots/#comment-4681 Sat, 17 May 2014 06:04:08 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-lesson-of-the-raining-dripping-crying-duct-boots#comment-4681 You hit the mark on how I got
You hit the mark on how I got gallons of water in my flex duct. The boots need to be insulated but………. HOW and with WHAT?

]]> https://www.energyvanguard.com/blog/the-lesson-of-the-raining-dripping-crying-duct-boots/#comment-4680 Thu, 13 Sep 2012 02:08:50 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-lesson-of-the-raining-dripping-crying-duct-boots#comment-4680 I have seen toilet tank
I have seen toilet tank insulating kits that are installed inside the bowl, and I have two of them in mine for about 30 years; they work great. The insulation is 1/4″ polystyrene sheeting, I don’t remember what the mastic was, but it’s been there from day one without a problem.. I think I have also seen insulated tanks from the factory.

]]> https://www.energyvanguard.com/blog/the-lesson-of-the-raining-dripping-crying-duct-boots/#comment-4679 Wed, 12 Sep 2012 19:56:22 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-lesson-of-the-raining-dripping-crying-duct-boots#comment-4679 John P.:
John P.: Indeed! Thanks for pointing out that important point. Insulation alone isn’t enough. I’ll go back and put that in the article, since it should have been there anyway.

]]> https://www.energyvanguard.com/blog/the-lesson-of-the-raining-dripping-crying-duct-boots/#comment-4678 Wed, 12 Sep 2012 19:49:18 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-lesson-of-the-raining-dripping-crying-duct-boots#comment-4678 Steve Z.:
Steve Z.: You wrap it with duct insulation just like you do any other sheet metal duct. You have to be careful because they’re not a nice symmetrical shape like a round or rectangular section of duct, but it can be done. I’ve had a photo of an insulated boot to the end of the article. 
 
Jake R.: Thanks for bringing up the topic of air flow! Yes, indeed, low air flow can make things colder than they should be and cause condensation to occur where it shouldn’t. Let me add a word of caution for those who might want to check static pressure. Be very careful when drilling holes in the air handler/furnace cabinet. You don’t want to drill into the heat exchanger or evaporator coil! 
 
M. Johnson: I agree with Jake. It’s an easy thing to check that’s not done very often. 
 
David F.: Sweating toilets happen for one of two reasons: Either the air is too humid or the toilet’s too cold. In either case, the temperature of the toilet tank/bowl is below the dew point. You can either raise the temperature of the tank/bowl (which is what your Maine plumbers are doing by mixing in hot water) or lower the humidity of the air. Maybe manufacturers could make an insulated tank/bowl for those of you who live climates that are too cold. 
 
Debbie: That’s true here, too. Most new homes have insulated boots, but there are plenty of existing homes out there that don’t, even some that are relatively new. Yeah, that was an interesting moment when I discovered that we were broadcasting our conversation. Lesson learned on that one. 
 

]]> https://www.energyvanguard.com/blog/the-lesson-of-the-raining-dripping-crying-duct-boots/#comment-4677 Wed, 12 Sep 2012 19:49:00 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-lesson-of-the-raining-dripping-crying-duct-boots#comment-4677 This is a place where a good
This is a place where a good air and vapor seal are needed. Remember the insulation will only make the outside surface of the duct colder. You need to make sure the air carrying the moisture does not get to that cold surface. A continuous air and vapor barrier are needed if you want to be confident that you have avoided the problem. (no leaks either)

]]> https://www.energyvanguard.com/blog/the-lesson-of-the-raining-dripping-crying-duct-boots/#comment-4676 Wed, 12 Sep 2012 19:12:07 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-lesson-of-the-raining-dripping-crying-duct-boots#comment-4676 hot humid climate. 
hot humid climate. 
 
most supply boots here in my area are insulated. only older heating only systems 
 
have uninsulated boots. As most of the duct installs here are in the attic, with insulated boots, it then becomes the hole where the boot pentrates the ceiling that becomes the dewpoint concern. oversized cuts for boots that are not mastic sealed. (note..mastic not caulked) once supply grill is attached from inside the house, the heat from the attic condenses on the supply grill via the oversized cut of the sheetrock. also in the attic, on the side of the boot where it is nailed/screwed/attached to ceiling joist is still a tight fit..but the other side of the boot is picked up off the attic floor by the screw attaching the grill. having seen this over and over, I’ve found the best fix to be as follows. remove supply grill from inside house, 
 
use hardcast brand mastic 1402 tape. I usually use 3″ tape split lengthways into two 1 1/2″ strips. one length of the tape is applied to sheetrock ceiling 
 
the other folded into the supply boot and sealed to the metal lip inside the box. I’ve done this for wall, attic and floor boots. the material is specific, foil tapes don’t adhere, asphalt backings dont adhere and caulk shrinks. my solution is a one time and done. tried and tested. eliminates duct/boot leakage and condensation stains on ceilings, walls… 
 
 
 
when you did the entry on tapes, I was glad to see that you included mastic tape. IMO between the paint on mastics and mastic tape, there are very few areas that can’t be sealed..and long term as opposed to short term lives of other tapes. 
 
in the few cases I’ve come across uninsulated boots I’ve used ductwrap (stapled &fsk; taped to hold ductwrap in contact with boot) mastic sealed at penetration into bldg envelope. then the above mastic tape method to stop any other leakage. 
 
 
 
good article Alison. I enjoyed your webinar about mini-splits also. just to poke you…always turn off audio when webinar is over..LOL! 
 

]]> https://www.energyvanguard.com/blog/the-lesson-of-the-raining-dripping-crying-duct-boots/#comment-4675 Wed, 12 Sep 2012 19:04:55 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-lesson-of-the-raining-dripping-crying-duct-boots#comment-4675 Another place where
Another place where condensation shows up is a toilet. Cold water in tanks and bowls makes water vapor condense and run down the sides of the toilet. I’ve often seen wet wood and mold under a toilet. 
 
Here in Maine, plumbers sometimes mix hot water with the cold water supply so the water in the tank is warm enough not to cause condensation. That’s an expensive fix. 
 
But what else can you do about it? 
 
David

]]> https://www.energyvanguard.com/blog/the-lesson-of-the-raining-dripping-crying-duct-boots/#comment-4674 Wed, 12 Sep 2012 17:07:05 +0000 http://energyvanguard.flywheelsites.com/?blog_post=the-lesson-of-the-raining-dripping-crying-duct-boots#comment-4674 Static pressure is not
Static pressure is not checked nearly enough. In most cases, high static pressure correlates with low air flow. Low air flow leads to capacity and efficiency loss, comfort issues, and can reduce equipment life. The measurements are very, very easy to do–a couple of holes to drill and a digital manometer. Easy as pie.

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