Can't see ductwork in attic??

[Shawn Thompson]

Did a house today that had additional blown ins. in the attic recently. I could tell, of course, that there was ductwork because I could see the straps and small areas of ducting. But the ductowrk, as a whole, was pretty much fully covered with the addition of this new insualtion. (call it out as a negative??)

[Brandon Whitmore]

In my area, the only problem with that would be energy loss since the insulation will not be as thick in those areas.

[Shawn Thompson]

Thank you, I think I will just bring it to the attention of the client as a non-typical finding.

[Jim Luttrall]

NOT a problem. In fact, this would actually be a good thing to have additional insulation surrounding the duct work.
What possible problems are you dreaming of?

[Ted Menelly]

Actually the duct work should not be lying in the insulation. The straps are there to hold it up out of it. But in saying that, having insulation below and on top of the duct work it is helping with loss from the ducts as most flex duct is fairly minimal in R factor. Maybe helps a little!!!!!!!!!!!!

[Shawn Thompson]

Just wasn't sure. This forum is great. I ended up just making a small disclaimer on the report about the limited visibility. I was thinking logic I guess. If this is not a "problem" and is actually a "plus" of some sort, then I would expect to see it all the time even on new construction. But of course on new construction it is strapped nicely above the insulation. So the purpose of the question was just makin sure I didnt make a big deal about nothing. Thanks.

[Jim Luttrall]

It is perfectly acceptable for ductwork to be supported on the ceiling joist with no hangers provided that the support intervals and other installation standards are followed.

http://www.flexibleduct.org/download/ADC~Inst.pdf

[Brandon Whitmore]

Would the installation of the ducts on top of the joists allow for enough insulation to comply with energy codes? Considering the fact that insulation contractors are not going to blow in more insulation on top of the duct area only.

[Jim Luttrall]

I can't see that a duct covered in insulation is going to be detrimental to the energy use of the house. As in the case of the OP


But the ductwork, as a whole, was pretty much fully covered with the addition of this new insulation.

Effectively moving the duct out of the attic toward the interior of the thermal envelope will be reducing the heat transfer from the attic to the duct and thereby the interior. What you loose on the attic floor, you will gain as the bottom and sides of the duct are insulated from the attic. I think anyone would be hard pressed to prove a detrimental energy loss on the situation described by the OP.

[Ted Menelly]

I can't see that a duct covered in insulation is going to be detrimental to the energy use of the house. As in the case of the OP



Effectively moving the duct out of the attic toward the interior of the thermal envelope will be reducing the heat transfer from the attic to the duct and thereby the interior. What you loose on the attic floor, you will gain as the bottom and sides of the duct are insulated from the attic. I think anyone would be hard pressed to prove a detrimental energy loss on the situation described by the OP.


Exactly what I was saying without saying it.

[Jerry Peck]

It is perfectly acceptable for ductwork to be supported on the ceiling joist with no hangers provided that the support intervals and other installation standards are followed.

http://www.flexibleduct.org/download/ADC~Inst.pdf

Provided ... of course ... that the duct *do not crush the insulation*. Note that the drawing allowing that does not show any insulation.

That would work fine in a house insulated with Icynene sprayed on the underside of the roof sheathing but not where the duct would be laying on the insulation.

[Jerry Peck]

I can't see that a duct covered in insulation is going to be detrimental to the energy use of the house. As in the case of the OP

Effectively moving the duct out of the attic toward the interior of the thermal envelope will be reducing the heat transfer from the attic to the duct and thereby the interior. What you loose on the attic floor, you will gain as the bottom and sides of the duct are insulated from the attic. I think anyone would be hard pressed to prove a detrimental energy loss on the situation described by the OP.

Nope. The MINIMUM insulation would still need to be met, and you cannot count more next to the duct as replacing that which is not where the duct is.

It would be hard pressed to prove a NON-detrimental "energy loss on the situation described by the OP" unless the full thickness of the insulation was there.

[Brandon Whitmore]

We need good answers on this one. I've been writing up ducts that are lying on/ in blown in insulation for years. I've always believed that it would be an energy loss issue----- it sure would be nice to know for sure.

[Jerry Peck]

We need good answers on this one. I've been writing up ducts that are lying on/ in blown in insulation for years. I've always believed that it would be an energy loss issue ...

It is as the insulation is either compressed or missing in depth ... or both.

[Jim Luttrall]

Getting back to the original question:

But the ductwork, as a whole, was pretty much fully covered with the addition of this new insulation. (call it out as a negative??)
Yes or no?
I vote no that it should not be called out as a negative.
Adding insulation to an otherwise compliant installation is not in and of itself a negative.
Adding insulation would in my opinion be a positive and no negative effects from the addition of new insulation would be present. No condensation, no detrimental effect of any kind to the existing insulation, duct or structure.

[Bob Spermo]

Assuming the joists are 2x6 - a filled cavity of blown insulation would give you an R factor of around 19. If it is a 10" duct and is covered with blown insulation that could be another R-30. Energy Star Certification computer programs give you extra points for ducts in the insulation. Whatever small gaps of insulation you would get because the ducts are there would be offset by keeping the air in the ducts from getting heated by the attic. Most new construction (at least Energy Star homes) is installing ducts with an R-8. I vote it is a positive to bury the ducts!

[Vern Heiler]

The insulation in question is between the attic and the interior side of the ceiling. Duct buried in the insulation is just an air space in the insulation, which is what insulation is, an air space. If the fan is not on it is a dead air space and if the fan is on the heat or cold would not make it to the ceiling surface. I see buried duct all the time and think it is better than suspended above the insulation.
JMHO
Vern