Sealed Attic

[Abby Normal]

Some of you guys in here know me, know the kind of climate I am in.

Anyways I built a place with a sealed attic, keeps the heat out in the first place, seems to have really minimized infiltration. Holding 40% RH in a real humid climate without a dehumidifier. Any of you want some details of my opinion of the sealed attic, email me

Attic is pretty bearable to be in, first test run the temps peaked at less than 85 F, averaged about 82 degrees, RH up there in mid 50s. I think my second round of tests will have it doing better than that.

[Zephyr]

What about building expiration [ventilation] to prevent mold and dry rot?

[Abby Normal]

82F at about 55% is not exactly condusive to mold. So far this attic is unconditioned, I will most likely condition it slightly, will try about 40 to 60 CFM of supply/return in the attic, a volume of about 4000 cubic feet. This should drop the attic average temp to perhaps 81F and keep RH under 50%.

Every do a commercial building with a flat roof deck, insulation on top? Maybe some T-bar below bar joists. Open return your this ceiling space or 'attic void' is now a plenum, ducted return it is an unconditioned space similar to what I have done to my attic.

See> What about building expiration [ventilation] to prevent mold and dry rot? >

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[Tony Hwang]

Hmmm, Then that's not sealed!

[Abby Normal]

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ambient dewpoint hovers around 80, concrete, some moisture wicks through I am sure. Pretty confident infiltration be extremely low, comparable to a sealed vapour barrier in a northern climate

[Mark]

so how do you keep the heat from the sun on the roof out of the attic?

Mark

[Abby Normal]

White metal roofing, on top of foam insulation, on top of the roof. About R7, looking a lot more effective at keeping the heat out than a lot of fibreglass does agaionst superheated air.

Gable end attic walls are insulated on the inside with 1.5 inches of styrofoam also.

My second round of tests right now, figure the attic is going to average about 80F. But involved my lowering the temperature in the home down from 79 to 75.

Sheet rock ceiling is presently separting the unconditioned attic from the space below.

The location is a year round cooling environment, humid

[<kjpro]

No insulation directly above the sheet rock?

Must be nice! :-)

[Abby Normal]

No insulation above the sheet rock, the insulation is on top of the roof. White metal roofing reflects a lot of heat away, and the insulation limits how much makes it in in the first place.

[Abby Normal]

I doubt I am even getting a natural air change rate of 0.10 per hour from infiltration. Bring on the pot lights