“Attics or roofs can be designed and constructed to be either - PowerPoint Presentation

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Uploaded On 2018-09-24

“Attics or roofs can be designed and constructed to be either - PPT Presentation

vented or unvented in any hygrothermal zone MoistureHeat zone The choice of venting or not venting is a design and construction choice not a requirement determined by the physics or by the building code The model building codes allow both vented and unvented roof assemblies The ID: 677912

charles buell attic ventilation buell charles ventilation attic inspections myths air sealing area courtesy roof space vented climate myth

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Slide1

“Attics or roofs can be designed and constructed to be either vented or unvented in any hygrothermal zone (Moisture/Heat zone). The choice of venting or not venting is a design and construction choice not a requirement determined by the physics or by the building code. The model building codes allow both vented and unvented roof assemblies. The applicable physics impacts the design of attic or roof systems as does the applicable building code but neither limit the choice.” Joseph Lstiburek *(highlighting is mine)

Myths of Attic Ventilation © Charles Buell, Charles Buell Inspections Inc

1Slide2

WHERE IS THE DEW POINT? (A bit like “Where’s Waldo,” it can surprise you where it is.)Problems with VentingIt “can” work, but you better keep your HVAC equipment and ducts out of the attic.

Hot roof solutionShorter shingle life?Use of non-air sealing types of insulation

So you live where it is

Hot and Humid?

Myths of Attic Ventilation

2Slide3

Myths of Attic Ventilation

Photo Courtesy Gary Smith,

SafeHome

Inspections, MississippiSlide4

Myths of Attic Ventilation © Charles Buell, Charles Buell Inspections Inc

Photo Courtesy Gary Smith,

SafeHome

Inspections, MississippiSlide5

Air

Pretty much everything you need to know about attic ventilation can be summed up in two words:

Myths of Attic Ventilation

Sealing!

5Slide6

If you think additional venting is “the answer,” you will be wrong, WAY more often than if you assume it is not the answer.

Myths of Attic Ventilation © Charles Buell, Charles Buell Inspections Inc

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What IS “Air Sealing?” Air sealing is simply using whatever means is practical to stop or slow the movement of air from one space to another.Vapor retarder (paints, plastic sheets, some types of insulation)CaulkPaintsSpray foamHouse wrap

DrywallLiquid WRBSheathing (Plywood/OSB/Foam Board/Etc)TapeWeather-strippingInsulationEtc

Myths of Attic Ventilation

Myths of Attic Ventilation © Charles Buell, Charles Buell Inspections Inc

Would you ever recommend fixing a roof leak by adding ventilation?

8Slide9

EVERYBODY knows inadequate ventilation is the cause of everything! Myths of Attic Ventilation © Charles Buell, Charles Buell Inspections IncBut what about ventilation?

Cold Climate

Hot Climate

Mixed Climate

Myth #3Slide10

So what about Ice Dams?Or maybe “damns” is more appropriate.

Myths of Attic Ventilation © Charles Buell, Charles Buell Inspections Inc

10Slide11

Myth #4:Everyone knows ice dams can be fixed with more ventilation **11Slide12

Myths of Attic Ventilation © Charles Buell, Charles Buell Inspections Inc

Hey! I have trained him to walk backwards!

Air Sealing has to happen firstSlide13

Myths of Attic Ventilation © Charles Buell, Charles Buell Inspections Inc

13Slide14

Solid Wood is not sufficient to prevent ice dams

14Slide15

Myths of Attic Ventilation © Charles Buell, Charles Buell Inspections IncPicture courtesy of Jim Quarello, JRV Home Inspection Services, Llc.

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Myths of Attic Ventilation © Charles Buell, Charles Buell Inspections IncPicture courtesy of Don Hester, NCW Home Inspections, Llc.

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50/50 or 60/40?1/150 or 1/300?

Upper

Lower

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Myth #5:The more ventilation the better.18Slide19

What the 2015 IRC says:R806.2 Minimum vent area. The minimum net free ventilating area shall be 1/150 of the area of the vented space.Exception: The minimum net free ventilation area shall be 1/300 of the vented space provided one or more of the following conditions are met:Myths of Attic Ventilation

1. In Climate Zones 6, 7 and 8, a Class I or II vapor retarder is installed on the warm-in-winter side of the ceiling.2. Not less than 40 percent and not more than 50 percent of the required ventilating area is provided by ventilators located in the upper portion of the attic or rafter space. This presentation is mostly geared toward colder and mixed climatesMyths of Attic Ventilation © Charles Buell, Charles Buell Inspections Inc

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ITISCOMPLICATED!

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Myth #6:Attic sheathing temperature, on a sunny day, will be similar to attic air temperature.24Slide25