Mastic or Not to Mastic

[fexley]

I'm building a new house which has metal duct work on the lower level and flexible duct work on the upper level. The house is about 7000 square feet. I'm expecting that the best thing to do is put mastic on the joints of the duct work? Is this my best path forward. Assuming, yes - roughly how long does this take a contractor to do this type of work. I would like to sanity check my pricing.

Thanks

[HydroAirJoe]

I'm building a new house which has metal duct work on the lower level and flexible duct work on the upper level. The house is about 7000 square feet. I'm expecting that the best thing to do is put mastic on the joints of the duct work? Is this my best path forward. Assuming, yes - roughly how long does this take a contractor to do this type of work. I would like to sanity check my pricing.

Thanks

Not to be a smart a$#, but you are building a 7000 SQ ft home and you are worried about the coast of duck sealing? Sealing the duck should of already been part of HVAC quote you got. If it's not find another contractor.

[HydroAirJoe]

Not to be a smart a$#, but you are building a 7000 SQ ft home and you are worried about the coast of duck sealing? Sealing the duck should of already been part of HVAC quote you got. If it's not find another contractor.

Yikes, shows you what fast fingers and being a smart-a$# will bite you in the "duck" I mean "duct".

[HydroAirJoe]

The thread reminds me of an episode on Holmes on Homes and the Canadian HVAC contractor was sealing the ducts with high temp silicone. Do any of you guys/gals do the same on your jobs? I can't imagine why since that stuff is a pair to clean off and the mastic is water cleanup.

[beenthere]

Assuming, yes - roughly how long does this take a contractor to do this type of work.

Thanks

Depends on the duct system. The more joints, the longer it takes.

[Some Dude]

The thread reminds me of an episode on Holmes on Homes and the Canadian HVAC contractor was sealing the ducts with high temp silicone. Do any of you guys/gals do the same on your jobs? I can't imagine why since that stuff is a pair to clean off and the mastic is water cleanup.

Why on earth would anyone use silicone on duct runs?
To the op, by all means use the mastic, air is not blown through a duct, the entire duct system is pressurized then air flows through each individual run, at least thats how its supposed to work.

[rundawg]

In typical houses, about 20% of the air that moves through the duct system is lost due to leaks, holes, and poorly connected ducts. The result is higher utility bills and difficulty keeping the house comfortable, no matter how the thermostat is set.

Just a 10% leakage will cause thousands of lost BTU’s entering the home.

Bottom line - Seal the ducts.

How long it takes - depends on the size of the ductwork and the professional doing it.

[EBear]

[QUOTE=fexley;5618802]I'm building a new house which has metal duct work on the lower level and flexible duct work on the upper level. The house is about 7000 square feet. I'm expecting that the best thing to do is put mastic on the joints of the duct work? Is this my best path forward. Assuming, yes - roughly how long does this take a contractor to do this type of work. I would like to sanity check my pricing.

Thanks[/QUOTE

This should help you: http://www.energydesignedhomes.com/Papers/DuctSealing.pdf

gl EBear

[CynicX]

Why on earth would anyone use silicone on duct runs?
To the op, by all means use the mastic, air is not blown through a duct, the entire duct system is pressurized then air flows through each individual run, at least thats how its supposed to work.

But zach has a booster fan in every single round line off the main trunk... :)

OP: Yes, mastic seal it. You say flex duct in the second level....there is going to be a main trunk line that is probably metal and insulated right? Dont get some spider web job.

In my area I rarely see new construction companies using mastic. I rarely see new construction companies design and install a decent duct system either.

Anyway if by second level you mean in the attic you will benefit in many difference ways from sealing the duct...

[Henry1]

Mastic. Gives a great seal.

You'd be surprised how many joints, gaps leak.

I got under the old home and took care of a LOT of problems by securing joins with sheet metal screws and then sealing with mastic.

Seems like I was forever down there but the repairs have got to have been worth it.

[badboyheel]

I'm assuming your paying a decent chunk of change to build your home. This is the time to make sure that the job is done right. You don't wanna have the contractor comeback and do repairs once your moved in, and by sealing with mastic on the original install is the way to go. I'm going to assume that there's plenty of ductwork in this house, and therefore there is going to be a considerable amount of air leakage even if the ductwork is done properly. I would recommend mastic at least on your main trunk lines.