EXISTING HOMES
Weatherization Specification Manual
QUICK REFERENCE GUIDE
(R-values are typical and intended as guides when specific manufacturer's information is unavailable)
Insulation Material
R-value (per inch)
Description (typical)
Loose fill fiberglass
2.3
Colors Pink/White/Yellow
Fiberglass batts (blanket)
3.1
Pink/ Yellow R-value can change depending on condition. See chart.
Cellulose fiber
3.7
Light gray/recycled paper products
Rockwool Loosefill
Black/Gray Similar to Fiberglass
Vermiculite
2.1
Silver/Brown Mica like
Perlite
Silver/White
Fiberglass Batt condition Ratings for attics
Good condition
3
No gaps or other imperfections
Fair condition
2
Gaps over 2.5%
Poor condition
0.7
Gaps over 5%
Fiberglass Loose Fill
R-values
3 1/2 inches
8
5 inches
11.5
6 inches
14
7 inches
16
8 inches
18.5
9 inches
21
10 inches
23
12 inches
28
15 to 17 inches
38
Rock wool Loose Fill
11
19
22
25
30
37
15 inches
47
Cellulose Loose Fill
13
26
33
Eave Vents
4 holes NFA=.09 sq. ft.
3 holes NFA=.07sq. ft.
1 hole NFA=.02 sq. ft.
Small rectangle opening NFA=0.25 sq. ft.
Large rectangle opening NFA=0.42 sq. ft.
Attic Ventilation
Roof jacks 7 inches diameter NFA= 0.21 sq. ft.
Roof jacks 8 inches diameter NFA=0.28 sq. ft.
Roof jacks 9 inches diameter NFA=0.35 sq. ft.
Roof jacks 12 inches diameter NFA=0.38 sq. ft.
Gable vent 12 inches x18 inches NFA=0.75 sq. ft.
Gable vent 12 inches x24 inches NFA=1.50 sq. ft.
Gable vent 12 inches x12 inches NFA=0.5 sq. ft.
To determine the size of the vent in Net Free Area (NFA) sq. ft., use the following equation:
Screen Factor:
The screen factor accounts for the loss in ventilation due to any louvers or screen cloth restricting airflow.
Here is a chart of screen factors:
1/4 or 1/2 mesh per inch without louvers = 1.00
1/4 or 1/2 mesh per inch with rain louvers= 2.00
1/8 mesh per inch without rain louvers= 1.25
1/8 mesh per inch with rain louvers= 2.25
1/16 mesh per inch without rain louvers= 2.00
1/16 mesh per inch with rain louvers= 3.00
For example: 14 1/2" X 3" vent with a 1/8" mesh = .24 sq. ft. NFA
Rule of thumb: Half of the opening size =NFA
(Most often, this will be within acceptable limits for gable vents)
Default Window U-values
U- Value
R-value
Single pane Aluminum frame
1.30
0.77
Single pane w/storm aluminum
1.10
0.91
Double pane aluminum
0.81
1.23
Vinyl double pane (no low-E)
0.48
2.08
Vinyl double pane Low-E/gas
0.35
2.86
Vinyl double pane Lowe-E Super Spacers/gas
0.28
3.57
Contact Information for Exemptions For waivers and interpretations, contact existinghomesta@energytrust.org or call 1.866.365.3526 option 9.
After Existing Homes gives a verbal exemption or interpretation, a waiver form will be sent by an Energy Trust representative within 24 hours and documentation of the exemption will be confirmed with the contractor.