Foam insulation board attic

[machsnell]

I know this has been discussed.

I am trying to figure out if you think this will help or be wirth it

I have a 1600 sf garage with attic space in northern virginia.

I will be foaming the walls and the ceiling to heat and cool the first.floor.

I dont.want to seal the underside.of the roof deck and have to heat.and cool the attic to maintain the garage area comfortably.

But I.dont want the attic to get.so hot that it burns up everything I put.up there. I had herbicide that I kept there and it.heat.up and bled out and many other items that are negatively affected.by the heat.

I have full ridge and soffit vents.

I have the opportunity.to buy 4x8 foot sheets of 3" eps foam boards for $7.50 each and I figure I would need 70 of them so 500 bucks or so.

My idea was to screw them to the underside of the trusses in the attic which would maintain airflow and convection from soffit to ridge. And the by pridict would be insulating lightly the attic space.

Will this work and be effective?

Will I need to add a louvred vent and a thermostatic attic fan of equal.flow to bring.in outside air and exhaust what will inevitably get.hot?

Thoughts and 2 cents appreciated.


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[Autorotica]

Why not try something like www.atticfoil.com ? Way less expensive and especially suited for keeping heat OUT from the roof.

Chris

 

[budvanbeer1]

"...My idea was to screw them to the underside of the trusses in the attic..."
This would create an insulation ceiling, right?

 

[machsnell]

"...My idea was to screw them to the underside of the trusses in the attic..."
This would create an insulation ceiling, right?

Yes the isulation would be the.ceiling basically. Tape the seams up to seal air in/out.

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[machsnell]

Why not try something like www.atticfoil.com ? Way less expensive and especially suited for keeping heat OUT from the roof.

Chris

If I did the attic foil I would still need to add an air inlet and gable fan correct?

Is this a better.option?

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[DC73]

I dont want to seal the underside of the roof deck and have to heat and cool the attic to maintain the garage area comfortably.

Not a big deal. You don't have to heat or cool the attic space and the garage will be just fine. They spray the underside of the roofs all the time now. The key is to air seal the ceiling so that you don't lose much of the heated and cooled air to the attic. But even if you did lose some air to the attic, it's not a big deal - the air can't escape the attic due to the foam. Just think of the attic as a giant air gap. I wouldn't hesitate to create an un-vented attic if I could afford the spray foam. Depending on your climate and the products used, you could also put some insulation on the attic floor. I'm aware of one home that sprayed foam under the roof for energy efficiency and comfort but put mineral wool insulation on the attic floor for fire and sound control.

Research on GreenBuildingAdvisor.com and BuildingScience.com for more info.

DC

 

[machsnell]

Thx i will go there read.

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[budvanbeer1]

Machsnell, I just noticed your location. Are you getting the 3" panels in MD by any chance?

 

[machsnell]

Yes that is where they are advertised. In silver spring

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