What duct insulation to use?

[92utownxh]

I'm planning a few projects: duct insulation, floor insulation, and windows and doors. I'm planning to do them in that order. What are your opinions on what is the best value for the money?

I'm planning to insulate the ductwork in my crawlspace unless I should do something else first. There are two kinds I'm looking at, but I'm not sure what is better. One is double sided foil with a bubble thing in between and an R-value of 3.7. The other is fiberglass with foil on the outside, but I can't find an R-value. Both of these are at Lowes. Will condensation be a problem with either of them?

 

[Slick]

what are your ducts now? Metal I assume...round or square? Can you get to all the sides of the duct?

 

[92utownxh]

The ducts are metal and square. I can get to all sides of them.

 

[Laird]

I used rigid foam insulation to insulate the foundation walls of my crawlspace. I originally had insulated flexduct for my duct work but the mice tore it all up over 15 years or so and I replaced it with uninsulated metal. Try as I might I was never able to mouseproof my crawlspace and living out in the country the mice are abundant. My crawlspace and floors now stay warm and the foam was easy to install with caulking/glue. I also now have no fear of any pipes freezing during cold weather.

 

[Slick]

I had similar and tried to find a solution which ended up being ripping it out and putting in new duct board ducts...probably not what you wanted to hear but I couldn't find a good way to insulate without being a mess. I'd pick fiberglass over bubble wrap myself but it's a mess to wrap it around and tape it on etc. HVAC contractors have long tubes they can slip over them that are the best I think but it's not easy to do, have to take down hangers etc.

 

[trax]

The R value of the wraps I use are pretty close, 1 1/2'" foil faced fiberglass is R-4 and the bubble wrap is 4.2 Condensation shouldn't be an issue with either if it is wraped tight and sealed with a good scrim tape. The bubble wrap is a little more exspensive but it is easier to work with and no itching or breathing fiberglass fibers. You may want to consider insulating the walls and sills of your crawl space instead of the ducts. By sealing and insulating the ducts you may create a cold floor above and if there are any water lines they could freeze up on you.

 

[92utownxh]

I've been trying to figure out what is the best thing to do. Most of the crawlspace is dirt with plastic over it. One section has concrete, and that is where the water heater, propane furnace, and well tank are. The owb lines go in there too.

Is it best to just insulate the walls and not worry about anything else? So far I haven't had any issues with pipes freezing, and they are not insulated. If I just insulate the walls, what is better: foam boards or fiberglass batts? The foam boards are expensive! Right now a lot of air gets in the crawlspace and some of the floors are cold.

I've been tossing this around for awhile now, but I'm ready to do it now. Just insulate the foundation walls, or insulate the floors and all the plumbing and ductwork?

 

[fourapples]

Input and some questions

I have been insulating my metal HVAC ducts, about 50% complete,but after reading it appears it may be wise to seal them first with mastic compound vs tape that will dry out. I have been using fiberglass with foil and taping insulation seams. I need to evaluate the process of sealing with mastic first, they say it can increase efficiency by 20-25%. Has anyone used mastic to seal their ductwork and is there a noticeable difference?

Here is another question..... I am sure most of us insulate the inside OWB lines but I have wondered about making a foam type box or something to insulate the plate exchanger for my DHW. After all a 10 plate exchanger unfolded would be about 10 linear feet of unprotected water flow and a 20 plate even more. Has anyone insulated their plate exchanger and how did you do it? Is this overkill?

 

[ericjeeper]

I've been trying to figure out what is the best thing to do. Most of the crawlspace is dirt with plastic over it. One section has concrete, and that is where the water heater, propane furnace, and well tank are. The owb lines go in there too.

Is it best to just insulate the walls and not worry about anything else? So far I haven't had any issues with pipes freezing, and they are not insulated. If I just insulate the walls, what is better: foam boards or fiberglass batts? The foam boards are expensive! Right now a lot of air gets in the crawlspace and some of the floors are cold.

I've been tossing this around for awhile now, but I'm ready to do it now. Just insulate the foundation walls, or insulate the floors and all the plumbing and ductwork?

If you really wish to seal it up go with closed cell spray foam.Applied directly to the foundation walls all the way up to the floor.

 

[mtfallsmikey]

Ducts: Code spec is 2" thick, foil-backed...either tape/use duct sealant (pookie) on the joints, duct tape supposed to meet UL 180 spec.

 

[92utownxh]

I've looked at the closed cell spray foam, but it's more than double the cost of anything else. I can't do that now. I know that would be the best thing though.

I guess now I'm trying to find out if it's best to insulate the floor or the foundation walls. Also what is the best thing to use (cost, quality, etc.). If I were to insulate the foundation would it be worth it to insulate the ducts? Thanks for the help.