Duct installation thru attic insulation

[humpy]

We are working on an office building with a pitched roof structure. Split air handlers will be in attic. Main trunks thru/between attic trusses. Branch ducts will run hard in the attic and punch between trusses and thru the insulation(batts)where a short length of flex will connect to our diffuser in a hung ceiling. The architect wants to hold the insulation between the bottom chord of the trusses up with chicken wire. We suggested drywall on the bottom of the trusses and were told it would not be in the budget. If we cannot talk him into the drywall, how are the duct penetrations thru the batts and wire mesh typically sealed? I was thinking of having the M.C. provide at least a piece of plywood at the points where branches come down. Something to cut a hole in and seal the ductwork to. Then batts could be cut and rest close to the penetration. Thanks for any input. I'm not fond of this insulation detail, but I guess it's better than batts on the hung ceiling.

 

[AbbyNormal]

That is about the worst type of attic to deal with down here, I am in a hot humid climate. Pop a t-bar tile and see fibre glass friction fitted between trusses. Air passes through easily, at least the fibreglass filters out the dirt as heat and humidity pass through. That kraft paper does not do a lot in my opinion.

You mentioned hung ceiling and a reluctance to use sheet rock on the under side of the trusses so the hung ceiling must be a T-bar and not suspended metal channels with sheet rock other wise the architect could of had an even higher ceiling and solved a couple problems at once.

Should be an air barrier on the under side of the trusses in my opinion and if it was all drywalled like you suggested it would have been a lot better.

If are in a colder climate like New York State hump, it could be a vapour barrier like poly.

Some plywood at the penetration would work good with a vapour barrier.

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[humpy]

Thanks for the reply. This is a t-bar lay-in ceiling. The ceiling is useful to keep our water piping out of the attic. Good point though with substituting a higher drywall ceiling for the current arrangement. We could run the water under slab. I'll look into it. As with many jobs, function follows form follows budget.