venting to the house

[robertbarnes62]

hello,

i am a home owner and i have a crawl space, which is where my ac unit is located. i have realized that it is cooler under the house than it is in the house. So i called a couple service companies, that are coming out this coming week.
I am here just to get some information so that the service people cannot screw me. so my questions are as follow: first which type of venting pipe is better? the flexible type that is shiny or the rigid dull metal type? secondly can there be leaks around the main part?(the part all the vent pipes attach to) also how is the best way for them to seal any leaks around any connections?

as much detail will really help. I want to be well prepared so that way i can ask the right questions and hopefully get the job done right.

thanks for any help!

[tinner73]

1. rigid pipe would be best and cost the most.

2. have them seal all connections with mastic/duct sealer.

[mrkool]

Which picture looks more like your crawlspace?

http://www.foothillscrawlspace.com/images/CleanSpace_Before_1.jpg

http://www.foothillscrawlspace.com/images/CleanSpace_After_1.jpg

When you say your ac is in the crawlspace, I hope your talking about just the ductwork and not the furnace/air handler as they tend to rust out real quick down there.

If your crawlspace has been open to outside by foundation vents and the ductwork insulation was put on to tight, then most likely it's soaking wet and needs to be rewrapped and the tape on the joints has come loose, but your on the right track,
most leaks are around where the branch lines connect the the main trunk line and also
where the return duct connects to the panning metal going up to the filter box area.

Depending on how old your ductwork is will depend on the type of take-off,
these are what we've been using for several years now to make a good tight seal.

http://i21.geccdn.net/site/images/n-picgroup/85864.jpg

[robertbarnes62]

1. rigid pipe would be best and cost the most.

2. have them seal all connections with mastic/duct sealer.

Ok, i will talk to them when they come to out...thanks

[robertbarnes62]

Which picture looks more like your crawlspace?

http://www.foothillscrawlspace.com/images/CleanSpace_Before_1.jpg

http://www.foothillscrawlspace.com/images/CleanSpace_After_1.jpg

When you say your ac is in the crawlspace, I hope your talking about just the ductwork and not the furnace/air handler as they tend to rust out real quick down there.

If your crawlspace has been open to outside by foundation vents and the ductwork insulation was put on to tight, then most likely it's soaking wet and needs to be rewrapped and the tape on the joints has come loose, but your on the right track,
most leaks are around where the branch lines connect the the main trunk line and also
where the return duct connects to the panning metal going up to the filter box area.

Depending on how old your ductwork is will depend on the type of take-off,
these are what we've been using for several years now to make a good tight seal.

http://i21.geccdn.net/site/images/n-picgroup/85864.jpg

As far as which pic does mine look like i would say it looks more like the bottom one but there is no insulation but it is dry with plastic on the floor...and it is all in the crawspacethe furnance and everything...so i guess i will have them check to see if it is lleaking...also should i check into gettinng the flexible duccting replaced witth the solid metal box looking type? And should i put insulation on the top of the crawl space? Well i guess that would be the botton of the floor?

[tinner73]

flex duct in a crawlspace only invites critters to live inside the duct.

[mrkool]

We've been sealing off crawlspaces for a couple years now and it can make a big difference in your heating, cooling and air quality, and when sealed properly, critters won't be able get into the crawlspace much less your flex ductwork.

Foundation vents were created before central heat and air and should be sealed off to prevent the outside humidity (moisture) from accessing the cool crawlspace, making for a wet & nasty mold growing place.

If it's sealed off from the outside, any dry cool air leaking out from the ducts can help dry the crawlspace even faster, and when you turn on heat for winter, your floors will be much warmer.

Here's a good site: http://www.buildingscience.com/documents/profiles/etw-montgomery-profile/

http://www.buildingscience.com/images/montgomery_profile.jpg

[robertbarnes62]

flex duct in a crawlspace only invites critters to live inside the duct.

Dang, i guess i will have them quote me a price for the rigid ducting...

[robertbarnes62]

We've been sealing off crawlspaces for a couple years now and it can make a big difference in your heating, cooling and air quality, and when sealed properly, critters won't be able get into the crawlspace much less your flex ductwork.

Foundation vents were created before central heat and air and should be sealed off to prevent the outside humidity (moisture) from accessing the cool crawlspace, making for a wet & nasty mold growing place.

If it's sealed off from the outside, any dry cool air leaking out from the ducts can help dry the crawlspace even faster, and when you turn on heat for winter, your floors will be much warmer.

Here's a good site: http://www.buildingscience.com/documents/profiles/etw-montgomery-profile/

http://www.buildingscience.com/images/montgomery_profile.jpg

So if they seal off the crawlspace i could keep the flix ducts? Also would you say that it has to leaking since the crawlspace is just as if not cooler than in the house?

[mrkool]

It's not only leaking air out, your leaking return duct is probably sucking in the humid air from the crawlspace, and that might be worse than it leaking out from the supply.

A word of warning about sealing off the foundation vents, if you do seal them off, install some type of "under vapor barrier" venting for radon gas, we install a 4" perforated black plastic pipe around the foundation edge where water seeps in, have both ends extend to the outside, connect one end to a small fan or blower.

Similar to this:
http://www.homeservicessouthwest.com/img/crawl-space-drain-pipe.jpg

But with this cheaper stuff from Lowes:
http://t0.gstatic.com/images?q=tbn:ANd9GcQDNTGIB0yuevGxOiEyga_vlw_CDJN44 2gi8SWH0XtYXhzwQ68xXKNnMfzN:

[jpsmith1cm]

It's not only leaking air out, your leaking return duct is probably sucking in the humid air from the crawlspace, and that might be worse than it leaking out from the supply.

A word of warning about sealing off the foundation vents, if you do seal them off, install some type of "under vapor barrier" venting for radon gas, we install a 4" perforated black plastic pipe around the foundation edge where water seeps in, have both ends extend to the outside, connect one end to a small fan or blower.

Similar to this:

But with this cheaper stuff from Lowes:


Mrkool,

Please check your PMs.