venting / insulation of attic gables
#1
03-19-14, 08:27 AM
venting / insulation of attic gables
The house I purchased has three gables, each with a louvered vent. I got into the attic and aside from loose cellulose insulation on the attic floor, there are fiberglass batts between the studs of each gable, except where the vent is.
What is the point of the fiberglass batts insulating the gable walls when they have vents?
PS there is no insulation on the underside of the roof, but there are the normal vents in the roof, not sure what those vents are called
What is the point of the fiberglass batts insulating the gable walls when they have vents?
PS there is no insulation on the underside of the roof, but there are the normal vents in the roof, not sure what those vents are called
#2
03-19-14, 09:06 AM
Banned. Rule And/Or Policy Violation
The insulation on the end walls is useless.
There's not suppose to any insulation in the rafter bays unless the attic is heated and cooled.
Are there soffit vents?
Only need to be insulating the building envelop.
Here's something to give you an idea of how much insulation should have been in your attic.
Recommended Levels of Insulation : ENERGY STAR
There's not suppose to any insulation in the rafter bays unless the attic is heated and cooled.
Are there soffit vents?
Only need to be insulating the building envelop.
Here's something to give you an idea of how much insulation should have been in your attic.
Recommended Levels of Insulation : ENERGY STAR
#3
03-19-14, 10:32 AM
>> Are there soffit vents?
Yes. Though in my old house, each panel soffit was a vent. In this house we moved to, about every third soffit panel is vented.
>> concerning the Energy Star hyperlink
I'm in zone 5, and the existing loose cellulose insulation is about 4 inches deep ~ which I think is equal to about R-12? So is the Energy Star page suggesting I should add another R38 to R49 ???
"Add Insulation to Attic" --> "Existing 3-4 Inches of Insulation" --> "5 to 8"
Yes. Though in my old house, each panel soffit was a vent. In this house we moved to, about every third soffit panel is vented.
>> concerning the Energy Star hyperlink
I'm in zone 5, and the existing loose cellulose insulation is about 4 inches deep ~ which I think is equal to about R-12? So is the Energy Star page suggesting I should add another R38 to R49 ???
"Add Insulation to Attic" --> "Existing 3-4 Inches of Insulation" --> "5 to 8"
#4
03-19-14, 11:51 AM
Before you bury the attic, an important step is to seal as many air leaks from below as possible. Many are easy, but many are not obvious. Getting to them is much easier before the extra foot of insulation and will probably save more energy than the insulation. Link below.
The guidelines for ventilation are 1ft² of net free vent area (NFA) for every 150 ft² of attic floor. Divide that resulting calculation half high and half low. Look for a ridge vent to see if one has been added. A typical NFA for a vent with a screen and louvers is 50% to 70% of its area.
Be sure to add baffles to each rafter bay to prevent new insulation from blocking the air flow.
Bud
http://www.efficiencyvermont.com/ste...ide_062507.pdf
The guidelines for ventilation are 1ft² of net free vent area (NFA) for every 150 ft² of attic floor. Divide that resulting calculation half high and half low. Look for a ridge vent to see if one has been added. A typical NFA for a vent with a screen and louvers is 50% to 70% of its area.
Be sure to add baffles to each rafter bay to prevent new insulation from blocking the air flow.
Bud
http://www.efficiencyvermont.com/ste...ide_062507.pdf
#5
03-19-14, 12:42 PM
Thank you for that hyperlink to the PDF.
>> an important step is to seal as many air leaks from below as possible
I have done that already. The only exception is the bathroom fan/vent.
>> Be sure to add baffles to each rafter bay to prevent new insulation from blocking the air flow.
There are already cardboard baffles in place.
Since there is already loose cellulose insulation present, should I "add" the same type of insulation material?
Do I need to be concerned that the existing insulation may be compressed by additional insulation material?
>> an important step is to seal as many air leaks from below as possible
I have done that already. The only exception is the bathroom fan/vent.
>> Be sure to add baffles to each rafter bay to prevent new insulation from blocking the air flow.
There are already cardboard baffles in place.
Since there is already loose cellulose insulation present, should I "add" the same type of insulation material?
Do I need to be concerned that the existing insulation may be compressed by additional insulation material?
#6
03-19-14, 03:24 PM
Be sure there are baffles in all rafter bays, not just those with vents. Also, if the rafter configuration is such that you can easily place something to protect the ends of the ceiling joists to prevent the incoming air from wind washing the insulation.
It is expected that additional layers will compress what is already there, just account for the loss of depth by adding extra. The bad part about compressing insulation is more about the loss of thickness than the loss of r-value per inch, up to a point.
Be sure the bath exhaust fan vents to the outside and not just into a soffit or even just below it.
Bud
It is expected that additional layers will compress what is already there, just account for the loss of depth by adding extra. The bad part about compressing insulation is more about the loss of thickness than the loss of r-value per inch, up to a point.
Be sure the bath exhaust fan vents to the outside and not just into a soffit or even just below it.
Bud
